Sample records for abdominal muscle contraction

  1. Electromyographic evaluation of abdominal-muscle function with and without concomitant pelvic-floor-muscle contraction.

    PubMed

    Tahan, Nahid; Arab, Amir Massoud; Vaseghi, Bita; Khademi, Khosro

    2013-05-01

    Coactivation of abdominal and pelvic-floor muscles (PFM) is an issue considered by researchers recently. Electromyography (EMG) studies have shown that the abdominal-muscle activity is a normal response to PFM activity, and increase in EMG activity of the PFM concomitant with abdominal-muscle contraction was also reported. The purpose of this study was to compare the changes in EMG activity of the deep abdominal muscles during abdominal-muscle contraction (abdominal hollowing and bracing) with and without concomitant PFM contraction in healthy and low-back-pain (LBP) subjects. A 2 × 2 repeated-measures design. Laboratory. 30 subjects (15 with LBP, 15 without LBP). Peak rectified EMG of abdominal muscles. No difference in EMG of abdominal muscles with and without concomitant PFM contraction in abdominal hollowing (P = .84) and abdominal bracing (P = .53). No difference in EMG signal of abdominal muscles with and without PFM contraction between LBP and healthy subjects in both abdominal hollowing (P = .88) and abdominal bracing (P = .98) maneuvers. Adding PFM contraction had no significant effect on abdominal-muscle contraction in subjects with and without LBP.

  2. Contraction of Abdominal Wall Muscles Influences Incisional Hernia Occurrence and Size

    PubMed Central

    Lien, Samuel C.; Hu, Yaxi; Wollstein, Adi; Franz, Michael G.; Patel, Shaun P.; Kuzon, William M.; Urbanchek, Melanie G.

    2015-01-01

    Background Incisional hernias are a complication in 10% of all open abdominal operations and can result in significant morbidity. The purpose of this study is to determine if inhibiting abdominal muscle contraction influences incisional hernia formation during laparotomy healing. We hypothesize that reducing abdominal musculature deformation reduces incisional hernia occurrence and size. Study Design Using an established rat model for incisional hernia, a laparotomy through the linea alba was closed with one mid-incision, fast-absorbing suture. Three groups were compared: a SHAM group (SHAM; n = 6) received no laparotomies while the Saline Hernia (SH; n = 6) and Botox Hernia (BH; n = 6) groups were treated once with equal volume saline or Botulinum Toxin (Botox®, Allergan) before the incomplete laparotomy closure. On post-operative day 14, the abdominal wall was examined for herniation and adhesions and contractile forces were measured for abdominal wall muscles. Results No hernias developed in SHAM rats. Rostral hernias developed in all SH and BH rats. Caudal hernias developed in all SH rats, but in only 50% of the BH rats. Rostral hernias in the BH group were 35% shorter and 43% narrower compared to those in the SH group (p < 0.05). The BH group had weaker abdominal muscles compared to the SHAM and SH groups (p < 0.05). Conclusions In our rat model, partial paralysis of abdominal muscles reduces the number and size of incisional hernias. These results confirm abdominal wall muscle contractions play a significant role in the pathophysiology of incisional hernia formation. PMID:25817097

  3. Relationship between abdominal and pelvic floor muscle activation and intravaginal pressure during pelvic floor muscle contractions in healthy continent women.

    PubMed

    Madill, Stéphanie J; McLean, Linda

    2006-01-01

    Activation of the abdominal muscles might contribute to the generation of a strong pelvic floor muscle contraction, and consequently may contribute to the continence mechanism in women. The purpose of this study was to determine the abdominal muscle activation levels and the patterns of muscle activity associated with voluntary pelvic floor muscle (PFM) contractions in urinary continent women. Fifteen healthy continent women participated. They performed three maximal contractions of each of the four abdominal muscles and of their PFMs while in supine. Abdominal and PFM activity was recorded using electromyography (EMG), and intravaginal pressure was recorded using a custom modified Femiscan probe. During voluntary maximal PFM contractions, rectus abdominus was activated to 9.61 (+/-7.42)% maximal voluntary electrical activity (MVE), transversus abdominus was activated to 224.30(+/-47.4)% MVE, the external obliques were activated to 18.72(+/-13.33)% MVE, and the internal obliques were activated to 81.47(+/-63.57)% MVE. A clear pattern of activation emerged, whereby the transversus abdominus, internal oblique, and rectus abdominus muscles worked with the PFM in the initial generation of maximal intravaginal pressure. PFM activity predominated in the initial rise in lower vaginal pressure, with later increases in pressure (up to 70% maximum pressure) being associated with the combined activation of the PFM, rectus abdominus, internal obliques, and transverses abdominus. These abdominal muscles were the primary source of intravaginal pressure increases in the latter 30% of the task, whereas there was little increase in PFM activation from this point on. The external oblique muscles showed no clear pattern of activity, but worked at approximately 20% MVE throughout the PFM contractions, suggesting that their role may be predominantly in postural setting prior to the initiation of intravaginal pressure increases. Defined patterns of abdominal muscle activity were found

  4. Comparison of changes in the mobility of the pelvic floor muscle on during the abdominal drawing-in maneuver, maximal expiration, and pelvic floor muscle maximal contraction.

    PubMed

    Jung, Halim; Jung, Sangwoo; Joo, Sunghee; Song, Changho

    2016-01-01

    [Purpose] The purpose of this study was to compare changes in the mobility of the pelvic floor muscle during the abdominal drawing-in maneuver, maximal expiration, and pelvic floor muscle maximal contraction. [Subjects] Thirty healthy adults participated in this study (15 men and 15 women). [Methods] All participants performed a bridge exercise and abdominal curl-up during the abdominal drawing-in maneuver, maximal expiration, and pelvic floor muscle maximal contraction. Pelvic floor mobility was evaluated as the distance from the bladder base using ultrasound. [Results] According to exercise method, bridge exercise and abdominal curl-ups led to significantly different pelvic floor mobility. The pelvic floor muscle was elevated during the abdominal drawing-in maneuver and descended during maximal expiration. Finally, pelvic floor muscle mobility was greater during abdominal curl-up than during the bridge exercise. [Conclusion] According to these results, the abdominal drawing-in maneuver induced pelvic floor muscle contraction, and pelvic floor muscle contraction was greater during the abdominal curl-up than during the bridge exercise.

  5. Comparison of changes in the mobility of the pelvic floor muscle on during the abdominal drawing-in maneuver, maximal expiration, and pelvic floor muscle maximal contraction

    PubMed Central

    Jung, Halim; Jung, Sangwoo; Joo, Sunghee; Song, Changho

    2016-01-01

    [Purpose] The purpose of this study was to compare changes in the mobility of the pelvic floor muscle during the abdominal drawing-in maneuver, maximal expiration, and pelvic floor muscle maximal contraction. [Subjects] Thirty healthy adults participated in this study (15 men and 15 women). [Methods] All participants performed a bridge exercise and abdominal curl-up during the abdominal drawing-in maneuver, maximal expiration, and pelvic floor muscle maximal contraction. Pelvic floor mobility was evaluated as the distance from the bladder base using ultrasound. [Results] According to exercise method, bridge exercise and abdominal curl-ups led to significantly different pelvic floor mobility. The pelvic floor muscle was elevated during the abdominal drawing-in maneuver and descended during maximal expiration. Finally, pelvic floor muscle mobility was greater during abdominal curl-up than during the bridge exercise. [Conclusion] According to these results, the abdominal drawing-in maneuver induced pelvic floor muscle contraction, and pelvic floor muscle contraction was greater during the abdominal curl-up than during the bridge exercise. PMID:27065532

  6. Measurement the thickness of the transverse abdominal muscle in different tasks.

    PubMed

    Pang, Ling; Yin, Liquan; Tajiri, Kimiko; Huo, Ming; Maruyama, Hitoshi

    2017-02-01

    [Purpose] This study examined the measurement of the thickness of the transverse abdominal muscle in different tasks. [Subjects and Methods] The subjects were eleven healthy adult females. Thicknesses of transverse abdominal muscle were measured in seven tasks in the supine position. The tasks were: 1) Resting state, 2) Maximal contraction of transverse abdominal muscle, 3) Maximal contraction of levator ani muscle, 4) Maximal simultaneous contraction of both transverse abdominal muscle and levator ani muscle, 5) Maximal simultaneous contraction of both transverse abdominal muscle and levator ani muscle with front side resistance added to both knee, 6) Maximal simultaneous contraction of both transverse abdominal muscle and levator ani muscle with diagonal resistance added to both knees, and 7) Maximal simultaneous contraction of both transverse abdominal muscle and levator ani muscle with lateral resistance added to both knees. [Results] The thicknesses of transverse abdominal muscle during maximal simultaneous contraction and maximal simultaneous contraction with resistance were greater than during the resting state. [Conclusion] The muscle output during simultaneous contraction and resistance movement were larger than that of each individual muscle.

  7. Pelvic floor muscle contraction and abdominal hollowing during walking can selectively activate local trunk stabilizing muscles.

    PubMed

    Lee, Ah Young; Baek, Seung Ok; Cho, Yun Woo; Lim, Tae Hong; Jones, Rodney; Ahn, Sang Ho

    2016-11-21

    Trunk muscle exercises are widely performed, and many studies have been performed to examine their effects on low back pains. However, the effect of trunk muscles activations during walking with pelvic floor muscle contraction (PFMC) and abdominal hollowing (AH) has not been clarified. To investigate whether walking with PFMC and AH is more effective for promoting local trunk muscle activation than walking without PFMC and AH. Twenty healthy men (28.9 ± 3.14 years, 177.2 ± 4.25 cm, 72.1 ± 6.39 kg, body mass index 22.78 ± 2.38 kg/m2) were participated in this study. Surface electrodes were attached over the multifidus (MF), lumbar erector spinae (LES), thoracic erector spinae (TES), transverse abdominus-internal oblique abdominals (TrA-IO), external oblique abdominals (EO), and rectus abdominus (RA). The amplitudes of electromyographic signals were measured during a normal walking with and without PFMC and AH. PFMC and AH while walking was found to result in significant bilateral increases in the normalized maximum voluntary contraction (MVC) of MFs and TrA-IOs (p< 0.05). Ratios of local muscle activity to global muscle activities were increased while performing PFMC and AH during normal walking. Bilateral TrA-IO/EO activity ratios were significantly increased by PFMC and AH (p< 0.05). Performance of the PFMC and AH during walking resulted in significantly more recruitment of local trunk muscles. This study suggests that PFMC and AH during normal daily walking improves activation of muscles responsible for spinal dynamic stabilization and might be useful if integrated into low back disability and pain physical rehabilitation efforts.

  8. The effect of motor control training on abdominal muscle contraction during simulated weight bearing in elite cricketers.

    PubMed

    Hides, Julie A; Endicott, Timothy; Mendis, M Dilani; Stanton, Warren R

    2016-07-01

    To investigate whether motor control training alters automatic contraction of abdominal muscles in elite cricketers with low back pain (LBP) during performance of a simulated unilateral weight-bearing task. Clinical trial. 26 male elite-cricketers attended a 13-week cricket training camp. Prior to the camp, participants were allocated to a LBP or asymptomatic group. Real-time ultrasound imaging was used to assess automatic abdominal muscle response to axial loading. During the camp, the LBP group performed a staged motor control training program. Following the camp, the automatic response of the abdominal muscles was re-assessed. At pre-camp assessment, when participants were axially loaded with 25% of their own bodyweight, the LBP group showed a 15.5% thicker internal oblique (IO) muscle compared to the asymptomatic group (p = 0.009). The post-camp assessment showed that participants in the LBP group demonstrated less contraction of the IO muscle in response to axial loading compared with the asymptomatic group. A trend was found in the automatic recruitment pattern of the transversus abdominis (p = 0.08). Motor control training normalized excessive contraction of abdominal muscles in response to a low load task. This may be a useful strategy for rehabilitation of cricketers with LBP. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Differences in muscle activation patterns during pelvic floor muscle contraction and Valsalva maneuver.

    PubMed

    Thompson, Judith A; O'Sullivan, Peter B; Briffa, N Kathryn; Neumann, Patricia

    2006-01-01

    To investigate the different muscle activation patterns around the abdomino-pelvic cavity in continent women and their effect on pressure generation during a correct pelvic floor muscle (PFM) contraction and a Valsalva maneuver. Thirteen continent women were assessed. Abdominal, chest wall, and PFM activity and vaginal and intra-abdominal pressure (IAP), were recorded during two tasks: PFM contraction and Valsalva whilst bladder base position was monitored on trans-abdominal ultrasound. A correct PFM contraction was defined as one that resulted in bladder base elevation and a Valsalva resulted in bladder base depression. Comparison of the mean of the normalized EMG activity of all the individual muscle groups was significantly different between PFM contraction and Valsalva (P = 0.04). During a correct PFM contraction, the PFM were more active than during Valsalva (P = 0.001). During Valsalva, all the abdominal muscles (IO (P = 0.006), EO (P < 0.001), RA (P = 0.011)), and the chest wall (P < 0.001) were more active than during PFM contraction. The change in IAP was greater during Valsalva (P = 0.001) but there was no difference in the change in vaginal pressure between PFM contraction and Valsalva (P = 0.971). This study demonstrates a difference in muscle activation patterns between a correct PFM contraction and Valsalva maneuver. It is important to include assessment of the abdominal wall, chest wall, and respiration in the clinical evaluation of women performing PFM exercises as abdominal wall bracing combined with an increase in chest wall activity may cause rises in IAP and PFM descent. (c) 2005 Wiley-Liss, Inc.

  10. Simultaneous Recording and Analysis of Uterine and Abdominal Muscle Electromyographic Activity in Nulliparous Women During Labor.

    PubMed

    Qian, Xueya; Li, Pin; Shi, Shao-Qing; Garfield, Robert E; Liu, Huishu

    2017-03-01

    To record and characterize electromyography (EMG) from the uterus and abdominal muscles during the nonlabor to first and second stages of labor and to define relationships to contractions. Nulliparous patients without any treatments were used (n = 12 nonlabor stage, 48 during first stage and 33 during second stage). Electromyography of both uterine and abdominal muscles was simultaneously recorded from electrodes placed on patients' abdominal surface using filters to separate uterine and abdominal EMG. Contractions of muscles were also recorded using tocodynamometry. Electromyography was characterized by analysis of various parameters. During the first stage of labor, when abdominal EMG is absent, uterine EMG bursts temporally correspond to contractions. In the second stage, uterine EMG bursts usually occur at same frequency as groups of abdominal bursts and precede abdominal bursts, whereas abdominal EMG bursts correspond to contractions and are accompanied by feelings of "urge to push." Uterine EMG increases progressively from nonlabor to second stage of labor. (1) Uterine EMG activity can be separated from abdominal EMG events by filtering. (2) Uterine EMG gradually evolves from the antepartum stage to the first and second stages of labor. (3) Uterine and abdominal EMG reflect electrical activity of the muscles during labor and are valuable to assess uterine and abdominal muscle events that control labor. (4) During the first stage of labor uterine, EMG is responsible for contractions, and during the second stage, both uterine and abdominal muscle participate in labor.

  11. The functional coupling of the deep abdominal and paraspinal muscles: the effects of simulated paraspinal muscle contraction on force transfer to the middle and posterior layer of the thoracolumbar fascia

    PubMed Central

    Vleeming, A; Schuenke, M D; Danneels, L; Willard, F H

    2014-01-01

    The thoracolumbar fascia (TLF) consists of aponeurotic and fascial layers that interweave the paraspinal and abdominal muscles into a complex matrix stabilizing the lumbosacral spine. To better understand low back pain, it is essential to appreciate how these muscles cooperate to influence lumbopelvic stability. This study tested the following hypotheses: (i) pressure within the TLF's paraspinal muscular compartment (PMC) alters load transfer between the TLF's posterior and middle layers (PLF and MLF); and (ii) with increased tension of the common tendon of the transversus abdominis (CTrA) and internal oblique muscles and incremental PMC pressure, fascial tension is primarily transferred to the PLF. In cadaveric axial sections, paraspinal muscles were replaced with inflatable tubes to simulate paraspinal muscle contraction. At each inflation increment, tension was created in the CTrA to simulate contraction of the deep abdominal muscles. Fluoroscopic images and load cells captured changes in the size, shape and tension of the PMC due to inflation, with and without tension to the CTrA. In the absence of PMC pressure, increasing tension on the CTrA resulted in anterior and lateral movement of the PMC. PMC inflation in the absence of tension to the CTrA resulted in a small increase in the PMC perimeter and a larger posterior displacement. Combining PMC inflation and tension to the CTrA resulted in an incremental increase in PLF tension without significantly altering tension in the MLF. Paraspinal muscle contraction leads to posterior displacement of the PLF. When expansion is combined with abdominal muscle contraction, the CTrA and internal oblique transfers tension almost exclusively to the PLF, thereby girdling the paraspinal muscles. The lateral border of the PMC is restrained from displacement to maintain integrity. Posterior movement of the PMC represents an increase of the PLF extension moment arm. Dysfunctional paraspinal muscles would reduce the posterior

  12. The functional coupling of the deep abdominal and paraspinal muscles: the effects of simulated paraspinal muscle contraction on force transfer to the middle and posterior layer of the thoracolumbar fascia.

    PubMed

    Vleeming, A; Schuenke, M D; Danneels, L; Willard, F H

    2014-10-01

    The thoracolumbar fascia (TLF) consists of aponeurotic and fascial layers that interweave the paraspinal and abdominal muscles into a complex matrix stabilizing the lumbosacral spine. To better understand low back pain, it is essential to appreciate how these muscles cooperate to influence lumbopelvic stability. This study tested the following hypotheses: (i) pressure within the TLF's paraspinal muscular compartment (PMC) alters load transfer between the TLF's posterior and middle layers (PLF and MLF); and (ii) with increased tension of the common tendon of the transversus abdominis (CTrA) and internal oblique muscles and incremental PMC pressure, fascial tension is primarily transferred to the PLF. In cadaveric axial sections, paraspinal muscles were replaced with inflatable tubes to simulate paraspinal muscle contraction. At each inflation increment, tension was created in the CTrA to simulate contraction of the deep abdominal muscles. Fluoroscopic images and load cells captured changes in the size, shape and tension of the PMC due to inflation, with and without tension to the CTrA. In the absence of PMC pressure, increasing tension on the CTrA resulted in anterior and lateral movement of the PMC. PMC inflation in the absence of tension to the CTrA resulted in a small increase in the PMC perimeter and a larger posterior displacement. Combining PMC inflation and tension to the CTrA resulted in an incremental increase in PLF tension without significantly altering tension in the MLF. Paraspinal muscle contraction leads to posterior displacement of the PLF. When expansion is combined with abdominal muscle contraction, the CTrA and internal oblique transfers tension almost exclusively to the PLF, thereby girdling the paraspinal muscles. The lateral border of the PMC is restrained from displacement to maintain integrity. Posterior movement of the PMC represents an increase of the PLF extension moment arm. Dysfunctional paraspinal muscles would reduce the posterior

  13. Surface Electromyographic Activity of the Abdominal Muscles During Pelvic-Tilt and Abdominal-Hollowing Exercises.

    PubMed

    Drysdale, Cheri L.; Earl, Jennifer E.; Hertel, Jay

    2004-03-01

    OBJECTIVE: To investigate surface electromyographic (EMG) activity of the rectus abdominus and external oblique abdominus muscles during pelvic-tilt and abdominal-hollowing exercises performed in different positions. DESIGN AND SETTING: 2 x 3 (exercise by position) within-subjects design with repeated measures on both factors. All testing was performed in a university laboratory. SUBJECTS: Twenty-six healthy, active young adult females. MEASUREMENTS: Surface EMG activity was recorded from the left and right rectus abdominus and external oblique muscles while the 2 exercises (pelvic tilt and abdominal hollowing) were performed in different positions (standard, legs supported, and legs unsupported). The standard position was supine in the crook-lying position, the supported position was with hips and knees flexed to 90 degrees and legs supported on a platform, and the unsupported position was with hips and knees flexed to 90 degrees without external support. Peak EMG activity was normalized to a maximum voluntary isometric contraction for each muscle. RESULTS: For the rectus abdominus, there was an interaction between position and activity. Abdominal hollowing produced significantly less activity than the pelvic tilt in all positions. The difference between the 2 exercises with the legs unsupported was of a greater magnitude than the other 2 positions. For the external obliques, there was significantly lower activity during the abdominal hollowing compared with the pelvic tilting. The greatest muscle activity occurred with the legs-unsupported position during both exercises. CONCLUSIONS: Abdominal-hollowing exercises produced less rectus abdominus and external oblique activity than pelvic-tilting exercises. Abdominal hollowing may be performed with minimal activation of the large global abdominal muscles.

  14. Surface Electromyographic Activity of the Abdominal Muscles During Pelvic-Tilt and Abdominal-Hollowing Exercises

    PubMed Central

    Drysdale, Cheri L.; Earl, Jennifer E.

    2004-01-01

    Objective: To investigate surface electromyographic (EMG) activity of the rectus abdominus and external oblique abdominus muscles during pelvic-tilt and abdominal-hollowing exercises performed in different positions. Design and Setting: 2 × 3 (exercise by position) within-subjects design with repeated measures on both factors. All testing was performed in a university laboratory. Subjects: Twenty-six healthy, active young adult females. Measurements: Surface EMG activity was recorded from the left and right rectus abdominus and external oblique muscles while the 2 exercises (pelvic tilt and abdominal hollowing) were performed in different positions (standard, legs supported, and legs unsupported). The standard position was supine in the crook-lying position, the supported position was with hips and knees flexed to 90° and legs supported on a platform, and the unsupported position was with hips and knees flexed to 90° without external support. Peak EMG activity was normalized to a maximum voluntary isometric contraction for each muscle. Results: For the rectus abdominus, there was an interaction between position and activity. Abdominal hollowing produced significantly less activity than the pelvic tilt in all positions. The difference between the 2 exercises with the legs unsupported was of a greater magnitude than the other 2 positions. For the external obliques, there was significantly lower activity during the abdominal hollowing compared with the pelvic tilting. The greatest muscle activity occurred with the legs-unsupported position during both exercises. Conclusions: Abdominal-hollowing exercises produced less rectus abdominus and external oblique activity than pelvic-tilting exercises. Abdominal hollowing may be performed with minimal activation of the large global abdominal muscles. PMID:15085209

  15. Assessment of abdominal muscle function in individuals with motor-complete spinal cord injury above T6 in response to transcranial magnetic stimulation.

    PubMed

    Bjerkefors, Anna; Squair, Jordan W; Chua, Romeo; Lam, Tania; Chen, Zhen; Carpenter, Mark G

    2015-02-01

    To use transcranial magnetic stimulation and electromyography to assess the potential for preserved function in the abdominal muscles in individuals classified with motor-complete spinal cord injury above T6. Five individuals with spinal cord injury (C5-T3) and 5 able-bodied individuals. Transcranial magnetic stimulation was delivered over the abdominal region of primary motor cortex during resting and sub-maximal (or attempted) contractions. Surface electromyography was used to record motor-evoked potentials as well as maximal voluntary (or attempted) contractions in the abdominal muscles and the diaphragm. Responses to transcranial magnetic stimulation in the abdominal muscles occurred in all spinal cord injury subjects. Latencies of muscle response onsets were similar in both groups; however, peak-to-peak amplitudes were smaller in the spinal cord injury group. During maximal voluntary (or attempted) contractions all spinal cord injury subjects were able to elicit electromyography activity above resting levels in more than one abdominal muscle across tasks. Individuals with motor-complete spinal cord injury above T6 were able to activate abdominal muscles in response to transcranial magnetic stimulation and during maximal voluntary (or attempted) contractions. The activation was induced directly through corticospinal pathways, and not indirectly by stretch reflex activations of the diaphragm. Transcranial magnetic stimulation and electromyography measurements provide a useful method to assess motor preservation of abdominal muscles in persons with spinal cord injury.

  16. Measurement of superficial and deep abdominal muscle thickness: an ultrasonography study.

    PubMed

    Tahan, Nahid; Khademi-Kalantari, Khosro; Mohseni-Bandpei, Mohammad Ali; Mikaili, Saeed; Baghban, Alireza Akbarzadeh; Jaberzadeh, Shapour

    2016-08-23

    Real-time ultrasound imaging is a valid method in the field of rehabilitation. The ultrasound imaging allows direct visualization for real-time study of the muscles as they contract over the time. Measuring of the size of each abdominal muscle in relation to the others provides useful information about the differences in structure, as well as data on trunk muscle activation patterns. The purpose of this study was to assess the size and symmetry of the abdominal muscles at rest in healthy adults and to provide a reference range of absolute abdominal muscle size in a relatively large population. A total 156 healthy subjects with the age range of 18-44 years were randomly recruited. The thickness of internal oblique, external oblique, transverse abdominis, and rectus abdominis muscles was measured at rest on both right and left sides using ultrasound. Independent t test was used to compare the mean thickness of each abdominal muscle between males and females. Differences on side-to-side thicknesses were assessed using paired t test. The association between abdominal muscle thicknesses with gender and anthropometric variables was examined using the Pearson correlation coefficient. A normal pattern of increasing order of mean abdominal muscle thickness was found in both genders at both right and left sides: transverse abdominis < external oblique < internal oblique < rectus abdominis. There was a significant difference on the size of transverse abdominis, internal oblique, and external oblique muscles between right and left sides in both genders. Males had significantly thicker abdominal muscles than females. Age was significantly correlated with the thickness of internal oblique, external oblique, and rectus abdominis muscles. Body mass index was also positively correlated with muscle thickness of rectus abdominis and external oblique. The results provide a normal reference range for the abdominal muscles in healthy subjects and may be used as an index to

  17. The effects of neuromuscular electrical stimulation at different frequencies on the activations of deep abdominal stabilizing muscles.

    PubMed

    Cho, Hee Kyung; Jung, Gil Su; Kim, Eun Hyuk; Cho, Yun Woo; Kim, Sang Woo; Ahn, Sang Ho

    2016-01-01

    Low back pain is associated with transversus abdominis (TrA) dysfunction. Recently, it was proposed that Neuromuscular Electrical Stimulation (NMES) could be used to stimulate deep abdominal muscle contractions and improve lumbopelvic stability. The purpose of this study was to determine the optimal stimulation frequency required during NMES for the activation of deep abdominal muscles. Twenty healthy volunteers between the ages of 24 and 32 were included. The portable research-stimulator was applied using a 10 second contraction time, and a 10 second resting time at 20 Hz, 50 Hz, and 80 Hz. Changes in muscle thicknesses were determined for the TrA, obliquus internus (OI), and obliquus externus (OE) by real time ultrasound imaging. Significant thickness increases in the TrA, OI, and OE were observed during NMES versus the resting state (p < 0.05). Of the frequencies examined, 50 Hz NMES produced the greatest increase in TrA thickness (1.33 fold as compared with 1.22 fold at 20 Hz and 1.21 fold at 80 Hz) (p < 0.05). Our results indicate that NMES can preferentially stimulate contractions in deep abdominal stabilizing muscles. Most importantly, 50 Hz NMES produced greater muscle thickness increases than 20 or 80 Hz.

  18. Abdominal muscle activity during a standing long jump.

    PubMed

    Okubo, Yu; Kaneoka, Koji; Shiina, Itsuo; Tatsumura, Masaki; Miyakawa, Shumpei

    2013-08-01

    Experimental laboratory study. To measure the activation patterns (onset and magnitude) of the abdominal muscles during a standing long jump using wire and surface electromyography. Activation patterns of the abdominal muscles, especially the deep muscles such as the transversus abdominis (TrA), have yet to be examined during full-body movements such as jumping. Thirteen healthy men participated. Wire electrodes were inserted into the TrA with the guidance of ultrasonography, and surface electrodes were attached to the skin overlying the rectus abdominis (RA) and external oblique (EO). Electromyographic signals and video images were recorded while each subject performed a standing long jump. The jump task was divided into 3 phases: preparation, push-off, and float. For each muscle, activation onset relative to the onset of the RA and normalized muscle activation levels (percent maximum voluntary contraction) were analyzed during each phase. Comparisons between muscles and phases were assessed using 2-way analyses of variance. The onset times of the TrA and EO relative to the onset of the RA were -0.13 ? 0.17 seconds and -0.02 ? 0.07 seconds, respectively. Onset of TrA activation was earlier than that of the EO. The activation levels of all 3 muscles were significantly greater during the push-off phase than during the preparation and float phases. Consistent with previously published trunk-perturbation studies in healthy persons, the TrA was activated prior to the RA and EO. Additionally, the highest muscle activation levels were observed during the push-off phase.

  19. Muscle Contraction.

    PubMed

    Sweeney, H Lee; Hammers, David W

    2018-02-01

    SUMMARYMuscle cells are designed to generate force and movement. There are three types of mammalian muscles-skeletal, cardiac, and smooth. Skeletal muscles are attached to bones and move them relative to each other. Cardiac muscle comprises the heart, which pumps blood through the vasculature. Skeletal and cardiac muscles are known as striated muscles, because the filaments of actin and myosin that power their contraction are organized into repeating arrays, called sarcomeres, that have a striated microscopic appearance. Smooth muscle does not contain sarcomeres but uses the contraction of filaments of actin and myosin to constrict blood vessels and move the contents of hollow organs in the body. Here, we review the principal molecular organization of the three types of muscle and their contractile regulation through signaling mechanisms and discuss their major structural and functional similarities that hint at the possible evolutionary relationships between the cell types. Copyright © 2018 Cold Spring Harbor Laboratory Press; all rights reserved.

  20. Transabdominal ultrasound to assess pelvic floor muscle performance during abdominal curl in exercising women.

    PubMed

    Barton, Amanda; Serrao, Chloe; Thompson, Judith; Briffa, Kathy

    2015-12-01

    The aim of this study was to assess pelvic floor muscle (PFM) function using transabdominal ultrasound (TAUS) in women attending group exercise classes. Specific aims were to: (1) identify the ability to perform a correct elevating PFM contraction and (2) assess bladder-base movement during an abdominal curl exercise. Ninety women participating in group exercise were recruited to complete a survey and TAUS assessment performed by two qualified Continence and Women's Health physiotherapists with clinical experience in ultrasound scanning. The assessment comprised three attempts of a PFM contraction and an abdominal curl exercise in crook lying. Bladder-base displacement was measured to determine correct or incorrect activation patterns. Twenty-five percent (n = 23) of women were unable to demonstrate an elevating PFM contraction, and all women displayed bladder-base depression on abdominal curl (range 0.33-31.2 mm). Parous women displayed, on average, significantly more bladder-base depression than did nulliparous women [15.5 (7.3) mm vs 11.4 (5.8) mm, p < 0.009). Sixty percent (n = 54) reported stress urinary incontinence (SUI). There was no association between SUI and the inability to perform an elevating PFM contraction (p = 0.278) or the amount of bladder-base depression with abdominal curl [14.1 (7.6) mm SUI vs 14.2 (6.7) mm non-SUI]. TAUS identified that 25 % of women who participated in group exercise were unable to perform a correctly elevating PFM contraction, and all depressed the bladder-base on abdominal curl. Therefore, exercising women may be at risk of PFM dysfunction when performing abdominal curl activities.

  1. Effects of inspiratory muscle training on balance ability and abdominal muscle thickness in chronic stroke patients

    PubMed Central

    Oh, Dongha; Kim, Gayeong; Lee, Wanhee; Shin, Mary Myong Sook

    2016-01-01

    [Purpose] This study evaluated the effects of inspiratory muscle training on pulmonary function, deep abdominal muscle thickness, and balance ability in stroke patients. [Subjects] Twenty-three stroke patients were randomly allocated to an experimental (n = 11) or control group (n = 12). [Methods] The experimental group received inspiratory muscle training-based abdominal muscle strengthening with conventional physical therapy; the control group received standard abdominal muscle strengthening with conventional physical therapy. Treatment was conducted 20 minutes per day, 3 times per week for 6 weeks. Pulmonary function testing was performed using an electronic spirometer. Deep abdominal muscle thickness was measured by ultrasonography. Balance was measured using the Berg balance scale. [Results] Forced vital capacity, forced expiratory volume in 1 second, deep abdominal muscle thickness, and Berg balance scale scores were significantly improved in the experimental group than in the control group. [Conclusion] Abdominal muscle strengthening accompanied by inspiratory muscle training is recommended to improve pulmonary function in stroke patients, and may also be used as a practical adjunct to conventional physical therapy. PMID:26957739

  2. Cardiac function in muscular dystrophy associates with abdominal muscle pathology.

    PubMed

    Gardner, Brandon B; Swaggart, Kayleigh A; Kim, Gene; Watson, Sydeaka; McNally, Elizabeth M

    The muscular dystrophies target muscle groups differentially. In mouse models of muscular dystrophy, notably the mdx model of Duchenne Muscular Dystrophy, the diaphragm muscle shows marked fibrosis and at an earlier age than other muscle groups, more reflective of the histopathology seen in human muscular dystrophy. Using a mouse model of limb girdle muscular dystrophy, the Sgcg mouse, we compared muscle pathology across different muscle groups and heart. A cohort of nearly 200 Sgcg mice were studied using multiple measures of pathology including echocardiography, Evans blue dye uptake and hydroxyproline content in multiple muscle groups. Spearman rank correlations were determined among echocardiographic and pathological parameters. The abdominal muscles were found to have more fibrosis than other muscle groups, including the diaphragm muscle. The abdominal muscles also had more Evans blue dye uptake than other muscle groups. The amount of diaphragm fibrosis was found to correlate positively with fibrosis in the left ventricle, and abdominal muscle fibrosis correlated with impaired left ventricular function. Fibrosis in the abdominal muscles negatively correlated with fibrosis in the diaphragm and right ventricles. Together these data reflect the recruitment of abdominal muscles as respiratory muscles in muscular dystrophy, a finding consistent with data from human patients.

  3. Relative Activity of Abdominal Muscles during Commonly Prescribed Strengthening Exercises.

    ERIC Educational Resources Information Center

    Willett, Gilbert M.; Hyde, Jennifer E.; Uhrlaub, Michael B.; Wendel, Cara L.; Karst, Gregory M.

    2001-01-01

    Examined the relative electromyographic (EMG) activity of upper and lower rectus abdominis (LRA) and external oblique (EOA) muscles during five abdominal strengthening exercises. Isometric and dynamic EMG data indicated that abdominal strengthening exercises activated various abdominal muscle groups. For the LRA and EOA muscle groups, there were…

  4. Aerobic metabolism on muscle contraction in porcine gastric smooth muscle.

    PubMed

    Kanda, Hidenori; Kaneda, Takeharu; Nagai, Yuta; Urakawa, Norimoto; Shimizu, Kazumasa

    2018-05-18

    Exposure to chronic hypoxic conditions causes various gastric diseases, including gastric ulcers. It has been suggested that gastric smooth muscle contraction is associated with aerobic metabolism. However, there are no reports on the association between gastric smooth muscle contraction and aerobic metabolism, and we have investigated this association in the present study. High K + - and carbachol (CCh)-induced muscle contractions involved increasing O 2 consumption. Aeration with N 2 (hypoxia) and NaCN significantly decreased high K + - and CCh-induced muscle contraction and O 2 consumption. In addition, hypoxia and NaCN significantly decreased creatine phosphate (PCr) contents in the presence of high K + . Moreover, decrease in CCh-induced contraction and O 2 consumption was greater than that of high K + . Our results suggest that hypoxia and NaCN inhibit high K + - and CCh-induced contractions in gastric fundus smooth muscles by decreasing O 2 consumption and intracellular PCr content. However, the inhibition of CCh-induced muscle contraction was greater than that of high K + -induced muscle contraction.

  5. Responses of intra-abdominal pressure and abdominal muscle activity during dynamic trunk loading in man.

    PubMed

    Cresswell, A G

    1993-01-01

    The purpose of this study was to determine and compare interactions between the abdominal musculature and intra-abdominal pressure (IAP) during controlled dynamic and static trunk muscle loading. Myoelectric activity was recorded in six subjects from the rectus abdominis, obliquus externus, obliquus internus, transversus abdominis and erector spinae muscles using surface and intra-muscular fine-wire electrodes. The IAP was recorded intra-gastrically. Trunk flexions and extensions were performed lying on one side on a swivel table. An adjustable brake provided different friction loading conditions, while adding weights to an unbraked swivel table afforded various levels of inertial loading. During trunk extensions at all friction loads, IAP was elevated (1.8-7.2 kPa) with concomitant activity in transversus abdominis and obliquus internus muscles--little or no activity was seen from rectus abdominis and obliquus externus muscles. For inertia loading during trunk extension, IAP levels were somewhat lower (1.8-5.6 kPa) and displayed a second peak when abdominal muscle activity occurred in the course of decelerating the movement. For single trunk flexions with friction loading, IAP was higher than that seen in extension conditions and increased with added resistance. For inertial loading during trunk flexion, IAP showed two peaks, the larger first peak matched peak forward acceleration and general abdominal muscle activation, while the second corresponded to peak deceleration and was accompanied by activity in transversus abdominis and erector spinae muscles. It was apparent that different loading strategies produced markedly different patterns of response in both trunk musculature and intra-abdominal pressure.

  6. Active behavior of abdominal wall muscles: Experimental results and numerical model formulation.

    PubMed

    Grasa, J; Sierra, M; Lauzeral, N; Muñoz, M J; Miana-Mena, F J; Calvo, B

    2016-08-01

    In the present study a computational finite element technique is proposed to simulate the mechanical response of muscles in the abdominal wall. This technique considers the active behavior of the tissue taking into account both collagen and muscle fiber directions. In an attempt to obtain the computational response as close as possible to real muscles, the parameters needed to adjust the mathematical formulation were determined from in vitro experimental tests. Experiments were conducted on male New Zealand White rabbits (2047±34g) and the active properties of three different muscles: Rectus Abdominis, External Oblique and multi-layered samples formed by three muscles (External Oblique, Internal Oblique, and Transversus Abdominis) were characterized. The parameters obtained for each muscle were incorporated into a finite strain formulation to simulate active behavior of muscles incorporating the anisotropy of the tissue. The results show the potential of the model to predict the anisotropic behavior of the tissue associated to fibers and how this influences on the strain, stress and generated force during an isometric contraction. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. [Effects of TWP on capacity of muscle contraction].

    PubMed

    Zhang, Yun; Yu, Jingrui; Lü, Guangneng; Li, Keyong; Xu, Jianguo

    2003-04-01

    To investigate the direct effects of Tripterygium Wilfordii Polyglycosidium (TWP) on capability of muscle contraction. Using electronic stimulator to stimulate the phrenic nerve of the isolated phrenic nerve diaphragm preparation of 30 rats or directly stimulate the isolated gastrocnemius muscle preparation of 45 toads in vitro, we studied the effects of TWP on capability of muscle intrinsic contraction. TWP in 20 mg/L increased the amplitude of muscle contraction in initial 60 min but did not make further increase of the amplitude of muscle contraction from 60 min to 90 min in the isolated phrenic nerve diaphragm preparation of rat under one-third optimal stimulus. TWP in 40 mg/L and in 60 mg/L did not cause decrease of amplitude of muscle contraction in initial 60 min in isolated phrenic nerve diaphragm preparation of rat under one-third optimal stimulus. TWP in 60 mg/L did not cause decrease of tension of signal-contraction in initial 30 min in isolated gastrocnemius muscle preparation of toad under one-third optimal direct stimulus. Solvent DMSO could obviously reduce the tension of muscle contraction both in isolated phrenic nerve diaphragm preparation of rat and in isolated gastrocnemius muscle preparation of toad under one-third optimal stimulus. TWP can limitedly enhance the capability of muscle contraction; Solvent DMSO can restrain muscle contraction.

  8. Contraction of the Ventral Abdomen Potentiates Extracardiac Retrograde Hemolymph Propulsion in the Mosquito Hemocoel

    PubMed Central

    Andereck, Jonathan W.; King, Jonas G.; Hillyer, Julián F.

    2010-01-01

    Background Hemolymph circulation in mosquitoes is primarily controlled by the contractile action of a dorsal vessel that runs underneath the dorsal midline and is subdivided into a thoracic aorta and an abdominal heart. Wave-like peristaltic contractions of the heart alternate in propelling hemolymph in anterograde and retrograde directions, where it empties into the hemocoel at the terminal ends of the insect. During our analyses of hemolymph propulsion in Anopheles gambiae, we observed periodic ventral abdominal contractions and hypothesized that they promote extracardiac hemolymph circulation in the abdominal hemocoel. Methodology/Principal Findings We devised methods to simultaneously analyze both heart and abdominal contractions, as well as to measure hemolymph flow in the abdominal hemocoel. Qualitative and quantitative analyses revealed that ventral abdominal contractions occur as series of bursts that propagate in the retrograde direction. Periods of ventral abdominal contraction begin only during periods of anterograde heart contraction and end immediately following a heartbeat directional reversal, suggesting that ventral abdominal contractions function to propel extracardiac hemolymph in the retrograde direction. To test this functional role, fluorescent microspheres were intrathoracically injected and their trajectory tracked throughout the hemocoel. Quantitative measurements of microsphere movement in extracardiac regions of the abdominal cavity showed that during periods of abdominal contractions hemolymph flows in dorsal and retrograde directions at a higher velocity and with greater acceleration than during periods of abdominal rest. Histochemical staining of the abdominal musculature then revealed that ventral abdominal contractions result from the contraction of intrasegmental lateral muscle fibers, intersegmental ventral muscle bands, and the ventral transverse muscles that form the ventral diaphragm. Conclusions/Significance These data show that

  9. Functional electrical stimulation to the abdominal wall muscles synchronized with the expiratory flow does not induce muscle fatigue.

    PubMed

    Okuno, Yukako; Takahashi, Ryoichi; Sewa, Yoko; Ohse, Hirotaka; Imura, Shigeyuki; Tomita, Kazuhide

    2017-03-01

    [Purpose] Continuous electrical stimulation of abdominal wall muscles is known to induce mild muscle fatigue. However, it is not clear whether this is also true for functional electrical stimulation delivered only during the expiratory phase of breathing. This study aimed to examine whether or not intermittent electrical stimulation delivered to abdominal wall muscles induces muscle fatigue. [Subjects and Methods] The subjects were nine healthy adults. Abdominal electrical stimulation was applied for 1.5 seconds from the start of expiration and then turned off during inspiration. The electrodes were attached to both sides of the abdomen at the lower margin of the 12th rib. Abdominal electrical stimulation was delivered for 15 minutes with the subject in a seated position. Expiratory flow was measured during stimulus. Trunk flexor torque and electromyography activity were measured to evaluate abdominal muscle fatigue. [Results] The mean stimulation on/off ratio was 1:2.3. The declining rate of abdominal muscle torque was 61.1 ± 19.1% before stimulus and 56.5 ± 20.9% after stimulus, not significantly different. The declining rate of mean power frequency was 47.8 ± 11.7% before stimulus and 47.9 ± 10.2% after stimulus, not significantly different. [Conclusion] It was found that intermittent electrical stimulation to abdominal muscles synchronized with the expiratory would not induce muscle fatigue.

  10. The effects of therapeutic hip exercise with abdominal core activation on recruitment of the hip muscles.

    PubMed

    Chan, Mandy Ky; Chow, Ka Wai; Lai, Alfred Ys; Mak, Noble Kc; Sze, Jason Ch; Tsang, Sharon Mh

    2017-07-21

    Core stabilization has been utilized for rehabilitation and prevention of lower limb musculoskeletal injuries. Previous studies showed that activation of the abdominal core muscles enhanced the hip muscle activity in hip extension and abduction exercises. However, the lack of the direct measurement and quantification of the activation level of the abdominal core muscles during the execution of the hip exercises affect the level of evidence to substantiate the proposed application of core exercises to promote training and rehabilitation outcome of the hip region. The aim of the present study was to examine the effects of abdominal core activation, which is monitored directly by surface electromyography (EMG), on hip muscle activation while performing different hip exercises, and to explore whether participant characteristics such as gender, physical activity level and contractile properties of muscles, which is assessed by tensiomyography (TMG), have confounding effect to the activation of hip muscles in enhanced core condition. Surface EMG of bilateral internal obliques (IO), upper gluteus maximus (UGMax), lower gluteus maximus (LGMax), gluteus medius (GMed) and biceps femoris (BF) of dominant leg was recorded in 20 young healthy subjects while performing 3 hip exercises: Clam, side-lying hip abduction (HABD), and prone hip extension (PHE) in 2 conditions: natural core activation (NC) and enhanced core activation (CO). EMG signals normalized to percentage of maximal voluntary isometric contraction (%MVIC) were compared between two core conditions with the threshold of the enhanced abdominal core condition defined as >20%MVIC of IO. Enhanced abdominal core activation has significantly promoted the activation level of GMed in all phases of clam exercise (P < 0.05), and UGMax in all phases of PHE exercise (P < 0.05), LGMax in eccentric phases of all 3 exercises (P < 0.05), and BF in all phases of all 3 exercises except the eccentric phase of PHE exercise (P

  11. Muscle Contraction Arrests Tumor Growth

    DTIC Science & Technology

    2006-09-01

    AD_________________ Award Number: W81XWH-05-1-0464 TITLE: Muscle Contraction Arrests Tumor Growth...DATE 01-09-2006 2. REPORT TYPE Annual 3. DATES COVERED 1 Sep 2005 – 31 Aug 2006 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Muscle ... Contraction Arrests Tumor Growth 5b. GRANT NUMBER W81XWH-05-1-0464 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Kim Westerlind, Ph.D. 5d. PROJECT NUMBER

  12. Why Do Abdominal Muscles Sometimes Separate during Pregnancy?

    MedlinePlus

    ... muscles that meet in the middle of the abdomen (rectus muscles) to become separated by an abnormal distance — ... to sitting up. Diastasis recti can weaken the abdominal muscles, causing lower back pain and making it difficult to lift objects or ...

  13. Use of the rectus abdominis muscle for abdominal stoma sphincter construction: an anatomical feasibility study.

    PubMed

    Bardoel, J W; Stadelmann, W K; Tobin, G R; Werker, P M; Stremel, R W; Kon, M; Barker, J H

    2000-02-01

    Permanent fecal abdominal stomas significantly decrease quality of life. Previous attempts to create continent stomas by using dynamic myoplasty procedures have resulted in disappointing outcomes, primarily owing to denervation atrophy of the muscle flap that was used in the creation of the sphincter and because of muscle fatigue resulting from continuous electrical stimulation that is received by the flap to force contraction. On the basis of these problems, we designed two separate studies: an anatomical study addressing flap denervation and a functional study addressing muscle fatigue. The present study addresses the first topic and was designed to develop a rectus abdominis muscle flap into a sphincter that was anatomically situated to create a stoma while preserving as much innervation as possible. In 24 rectus abdominis muscles of human cadavers, the neurovascular anatomy was defined, then the anatomical feasibility of two different muscle flap configurations was considered. The flaps investigated were the peninsula flap and island flap designs, with both using the most caudal segment of the rectus abdominis muscle in construction of the sphincter. Neither flap design required the killing of a nerve for stoma sphincter creation, resulting in minimal muscle denervation. The conclusion of our comparison was that the above, in conjunction with other features of the island flap design, such as muscle overlap after sphincter formation and abdominal wall positioning of the sphincter, made the island flap design better suited to stoma sphincter construction.

  14. Muscle activity in upper and lower rectus abdominus during abdominal exercises.

    PubMed

    Sarti, M A; Monfort, M; Fuster, M A; Villaplana, L A

    1996-12-01

    To compare the intensity of the upper versus lower rectus abdominis (RA) muscle activity provoked by each of two different abdominal exercises and to contrast the intensity of contraction elicited by two different abdominal exercises on each RA muscle portion. Nonrandomized control trial. Kinesiology laboratory in a university medicine faculty. Convenience sample of 33 healthy volunteers. Subjects who had practiced endurance or strength training activities (1.5 hours 3 days a week for 3 years) and those who had not accomplished that criterion comprised a high and a low physical activity group, respectively. Each of these two groups was divided by the ability to perform the exercises into two subgroups: correct and incorrect performers (cp, ic). Average surface iEMG was compared between upper and lower RA and on each muscle portion performing curl-up (CU) and posterior pelvic tilt (PT) exercises. The coefficient of variation, a two-way analysis of variance, and the t test were calculated. The upper RA showed significantly greater activity during performance of CU exercise by the cp subgroups of both high (t = 2.14302, 95%) and low (t = 2.35875, 95%) activity groups. Only the cp subgroup of the high activity group showed that PT was significantly more strenuous than CU exercise on lower RA (t = -2.06467, 95%). Among correct performers, CU produces greater activity on upper RA. For persons who have a high level of activity, PT is more strenuous than CU on lower RA. Among incorrect performers, either exercise indistinctly activates the muscle portions.

  15. Abdomino-phrenic dyssynergia in patients with abdominal bloating and distension.

    PubMed

    Villoria, Albert; Azpiroz, Fernando; Burri, Emanuel; Cisternas, Daniel; Soldevilla, Alfredo; Malagelada, Juan-R

    2011-05-01

    The abdomen normally accommodates intra-abdominal volume increments. Patients complaining of abdominal distension exhibit abnormal accommodation of colonic gas loads (defective contraction and excessive protrusion of the anterior wall). However, abdominal imaging demonstrated diaphragmatic descent during spontaneous episodes of bloating in patients with functional gut disorders. We aimed to establish the role of the diaphragm in abdominal distension. In 20 patients complaining of abdominal bloating and 15 healthy subjects, we increased the volume of the abdominal cavity with a colonic gas load, while measuring abdominal girth and electromyographic activity of the anterior abdominal muscles and of the diaphragm. In healthy subjects, the colonic gas load increased girth, relaxed the diaphragm, and increased anterior wall tone. With the same gas load, patients developed significantly more abdominal distension; this was associated with paradoxical contraction of the diaphragm and relaxation of the internal oblique muscle. In this experimental provocation model, abnormal accommodation of the diaphragm is involved in abdominal distension.

  16. Onset in abdominal muscles recorded simultaneously by ultrasound imaging and intramuscular electromyography.

    PubMed

    Vasseljen, Ottar; Fladmark, Anne M; Westad, Christian; Torp, Hans G

    2009-04-01

    Delayed onset of muscle activity in abdominal muscles has been related to low back pain. To investigate this in larger clinical trials it would be beneficial if non-invasive and less cumbersome alternatives to intramuscular electromyography (EMG) were available. This study was designed to compare onset of muscle activity recorded by intramuscular EMG to onset of muscle deformations by ultrasound imaging. Muscle deformations were recorded by two ultrasound imaging modes at high time resolution (m-mode and tissue velocity) in separate sessions and compared to simultaneously recorded intramuscular EMG in three abdominal muscles. Tissue velocity imaging was converted to strain rate which measures deformation velocity gradients within small regions, giving information about the rate of local tissue shortening or lengthening along the beam axis. Onsets in transversus abdominis (TrA), obliquus internus abdominis (OI) and obliquus externus abdominis (OE) were recorded during rapid arm flexions in ten healthy subjects. During ultrasound m-mode recordings, the results showed that mean onsets by EMG were detected 7 ms (95% CI of mean difference; +/-4 ms) and 2 ms (95% CI of mean difference; +/-6 ms) before concurrent ultrasound m-mode detected onsets in TrA and OI, respectively. In contrast, OE onset was recorded 54 ms (95% CI of bias; +/-16 ms) later by EMG compared to ultrasound m-mode. The discrepancy of ultrasound m-mode to accurately record onset in OE was practically corrected in the ultrasound-based strain rate recordings. However, this could only be applied on half of the subjects due to the angle dependency between the ultrasound beam and the direction of the contraction in strain rate recordings. The angle dependency needs to be further explored.

  17. Uninvolved versus target muscle contraction during contract: relax proprioceptive neuromuscular facilitation stretching.

    PubMed

    Azevedo, Daniel Camara; Melo, Raphael Marques; Alves Corrêa, Ricardo Vidal; Chalmers, Gordon

    2011-08-01

    The purpose of this study was to compare the acute effect of the contract-relax (CR) stretching technique on knee active range of motion (ROM) using target muscle contraction or an uninvolved muscle contraction. pre-test post-test control experimental design. Clinical research laboratory. Sixty healthy men were randomly assigned to one of three groups. The Contract-Relax group (CR) performed a traditional hamstring CR stretch, the Modified Contract-Relax group (MCR) performed hamstring CR stretching using contraction of an uninvolved muscle distant from the target muscle, and the Control group (CG) did not stretch. Active knee extension test was performed before and after the stretching procedure. Two-way between-within analysis of variance (ANOVA) results showed a significant interaction between group and pre-test to post-test (p < 0.001). Post-hoc examination of individual groups showed no significant change in ROM for the CG (0.8°, p = 0.084), and a significant moderate increase in ROM for both the CR (7.0°, p < 0.001) and MCR (7.0°, p < 0.001) groups. ROM gain following a CR PNF procedure is the same whether the target stretching muscle is contracted, or an uninvolved muscle is contracted. Copyright © 2011 Elsevier Ltd. All rights reserved.

  18. Electromyographic and kinetic analysis of two abdominal muscle performance tests.

    PubMed

    Haladay, Douglas E; Denegar, Craig R; Miller, Sayers J; Challis, John

    2015-01-01

    In order to accurately assess the abdominal muscles, clinicians need valid clinical measures. The double leg lowering test (DLLT) and lower abdominal muscle progression (LAMP) are two common tests of abdominal muscle performance. The purposes of this study were to determine the relation between surface electromyographic (EMG) activity during the DLLT and LAMP levels; hip joint resultant moments and DLLT and LAMP levels; and the two measures of DLLT and LAMP. Ten healthy participants were tested under both conditions. Surface EMG activity of the abdominal muscles was obtained, while pelvic movement was detected simultaneously. A moderate to strong association was found between rectus abdominus muscle activity and a moderate association with the external obliques with both test levels. For the internal oblique/transversus abdominus, a moderate and weak association was found with the DLLT and LAMP, respectively. A very strong association existed between the hip resultant joint moments (RJM) and the DLLT, while there was a weak correlation between hip RJM and the LAMP. No significant correlation was found between the DLLT and LAMP grades. This finding suggests that these tests may measure different qualities of muscle performance and provides preliminary support for their use. Further evaluation of these assessments with clinical populations is necessary.

  19. Psychometric Properties of the Deep Muscle Contraction Scale for Assessment of the Drawing-in Maneuver in Patients With Chronic Nonspecific Low Back Pain.

    PubMed

    Oliveira, Crystian B; Negrão Filho, Ruben F; Franco, Márcia R; Morelhão, Priscila K; Araujo, Amanda C; Pinto, Rafael Z

    2017-06-01

    Study Design A prospective cohort study. Background Motor control dysfunctions have been commonly reported in patients with chronic nonspecific low back pain (LBP). Physical therapists need clinical tools with adequate psychometric properties to assess such patients in clinical practice. The deep muscle contraction (DMC) scale is a clinical rating scale for assessing patients' ability to voluntarily contract deep abdominal muscles. Objectives To investigate the intrarater reliability, floor and ceiling effects, internal and external responsiveness, and correlation analysis (with ultrasound measures) of the DMC scale in patients with chronic nonspecific LBP undergoing a lumbar stabilization exercise program. Methods Sixty-two patients with chronic nonspecific LBP were included. At baseline, self-report questionnaires were administered to patients and a trained assessor evaluated abdominal muscle recruitment with the DMC scale and ultrasound imaging. Four ratios of the change in abdominal muscle thickness between the resting and contracted states were calculated through the ultrasound measures. After 1 week, the same ultrasound measures and DMC scale were collected again for the reliability analysis. The proportions of patients with the lowest and highest scores on the DMC scale were calculated to investigate floor and ceiling effects. All patients underwent a lumbar stabilization program, administered twice a week for 8 weeks. After the treatment period, all measures were collected again, with the addition of the global perceived effect scale, to assess the internal and external responsiveness of the measures. Correlation coefficients between ultrasound ratios and DMC scale total and subscale scores were also calculated. Results The intrarater reliability of the DMC scale and the 4 ratios of abdominal muscle thickness varied from moderate to excellent. The DMC scale showed no floor or ceiling effects. Results for internal responsiveness of the DMC scale showed large

  20. Endurance training facilitates myoglobin desaturation during muscle contraction in rat skeletal muscle.

    PubMed

    Takakura, Hisashi; Furuichi, Yasuro; Yamada, Tatsuya; Jue, Thomas; Ojino, Minoru; Hashimoto, Takeshi; Iwase, Satoshi; Hojo, Tatsuya; Izawa, Tetsuya; Masuda, Kazumi

    2015-03-24

    At onset of muscle contraction, myoglobin (Mb) immediately releases its bound O2 to the mitochondria. Accordingly, intracellular O2 tension (PmbO2) markedly declines in order to increase muscle O2 uptake (mVO2). However, whether the change in PmbO2 during muscle contraction modulates mVO2 and whether the O2 release rate from Mb increases in endurance-trained muscles remain unclear. The purpose of this study was, therefore, to determine the effect of endurance training on O2 saturation of Mb (SmbO2) and PmbO2 kinetics during muscle contraction. Male Wistar rats were subjected to a 4-week swimming training (Tr group; 6 days per week, 30 min × 4 sets per day) with a weight load of 2% body mass. After the training period, deoxygenated Mb kinetics during muscle contraction were measured using near-infrared spectroscopy under hemoglobin-free medium perfusion. In the Tr group, the VmO2peak significantly increased by 32%. Although the PmbO2 during muscle contraction did not affect the increased mVO2 in endurance-trained muscle, the O2 release rate from Mb increased because of the increased Mb concentration and faster decremental rate in SmbO2 at the maximal twitch tension. These results suggest that the Mb dynamics during muscle contraction are contributing factors to faster VO2 kinetics in endurance-trained muscle.

  1. Endurance training facilitates myoglobin desaturation during muscle contraction in rat skeletal muscle

    PubMed Central

    Takakura, Hisashi; Furuichi, Yasuro; Yamada, Tatsuya; Jue, Thomas; Ojino, Minoru; Hashimoto, Takeshi; Iwase, Satoshi; Hojo, Tatsuya; Izawa, Tetsuya; Masuda, Kazumi

    2015-01-01

    At onset of muscle contraction, myoglobin (Mb) immediately releases its bound O2 to the mitochondria. Accordingly, intracellular O2 tension (PmbO2) markedly declines in order to increase muscle O2 uptake (mO2). However, whether the change in PmbO2 during muscle contraction modulates mO2 and whether the O2 release rate from Mb increases in endurance-trained muscles remain unclear. The purpose of this study was, therefore, to determine the effect of endurance training on O2 saturation of Mb (SmbO2) and PmbO2 kinetics during muscle contraction. Male Wistar rats were subjected to a 4-week swimming training (Tr group; 6 days per week, 30 min × 4 sets per day) with a weight load of 2% body mass. After the training period, deoxygenated Mb kinetics during muscle contraction were measured using near-infrared spectroscopy under hemoglobin-free medium perfusion. In the Tr group, the mO2peak significantly increased by 32%. Although the PmbO2 during muscle contraction did not affect the increased mO2 in endurance-trained muscle, the O2 release rate from Mb increased because of the increased Mb concentration and faster decremental rate in SmbO2 at the maximal twitch tension. These results suggest that the Mb dynamics during muscle contraction are contributing factors to faster O2 kinetics in endurance-trained muscle. PMID:25801957

  2. Lumbar muscle rhabdomyolysis after abdominal aortic surgery.

    PubMed

    Bertrand, M; Godet, G; Fléron, M H; Bernard, M A; Orcel, P; Riou, B; Kieffer, E; Coriat, P

    1997-07-01

    Lumbar muscle rhabdomyolysis has been very rarely reported after surgery. The aim of this study was to determine its incidence and main characteristics in a large population undergoing abdominal aortic surgery. Over a 21-mo period, 224 consecutive patients, 209 male and 15 female, mean age 65 +/- 10 yr, underwent abdominal aortic surgery (aortic aneurysm in 142 patients and occlusive aortic degenerative disease in 82 patients). Surgical incision was a midline incision with exaggerated hyperlordosis in 173 patients and a flank incision with a retroperitoneal approach in 51 patients. Postoperative rhabdomyolysis was diagnosed in 20 patients. In these patients, 9 (4%) experienced severe low back pain, and lumbar muscle rhabdomyolysis was confirmed by tomodensitometry (n = 6) or muscle biopsy (n = 3). The remaining 11 patients had lower limb muscle rhabdomyolysis. Rhabdomyolysis occurred after surgery of longer duration, which involved more frequent visceral artery reimplantation, with longer duration of aortic clamping and greater intraoperative bleeding. Lumbar rhabdomyolysis occurred in younger patients who were more frequently obese. On first postoperative day, the mean creatine kinase (CK) value was greater in lumbar rhabdomyolysis than in lower limb rhabdomyolysis (17,082 +/- 15,003 vs 3,313 +/- 3,120 IU/L, P < 0.05). Acute renal failure and postoperative death did not occur in patients with lumbar muscle rhabdomyolysis. Lumbar rhabdomyolysis was not a rare event after abdominal aortic surgery (4%). This syndrome was characterized by postoperative low back pain of unusual severity, which required analgesic therapy, and induced a very high increase in CK with typical findings at tomodensitometry or muscle biopsy but was not associated with postoperative renal failure.

  3. The effect of abdominal resistance training and energy restricted diet on lateral abdominal muscles thickness of overweight and obese women.

    PubMed

    Noormohammadpour, Pardis; Kordi, Ramin; Dehghani, Saeed; Rostami, Mohsen

    2012-07-01

    The role of transabdominal muscles (external oblique, internal oblique and transversus abdominis) on core stability has been shown previously. Energy restricted diet and abdominal resistance training are commonly used by overweight and obese people to reduce their weight. In this study we investigated the impact of 12 weeks concurrent energy restricted diet and abdominal resistance training on the thickness of the lateral abdominal muscles of 19 obese and overweight women employing ultrasonography in resting and drawing-in maneuvers. The results showed significant increase of the muscle thicknesses during drawing-in maneuver after 12 weeks intervention. Based on our findings, it can be concluded that 12 weeks concurrent abdominal resistance training and energy restricted diet in addition to weight loss lead to improvement of transabdominal muscles thickness in obese and overweight people. Considering the role of these muscles in core stability, using this therapeutic protocol in obese people, particularly in those who have weakness of these muscles might be helpful. Copyright © 2011 Elsevier Ltd. All rights reserved.

  4. Comparison of lateral abdominal muscle thickness between weightlifters and matched controls.

    PubMed

    Sitilertpisan, Patraporn; Pirunsan, Ubon; Puangmali, Aatit; Ratanapinunchai, Jonjin; Kiatwattanacharoen, Suchart; Neamin, Hudsaleark; Laskin, James J

    2011-11-01

    To compare lateral abdominal muscle thickness between weightlifters and matched controls. A case control study design. University laboratory. 16 female Thai national weightlifters and 16 matched controls participated in this study. Ultrasound imaging with a 12-MHz linear array was used to measure the resting thickness of transversus abdominis (TrA), internal oblique (IO) and total thickness (Total) of lateral abdominal muscle (LAM) on the right side of abdominal wall. The absolute muscle thickness and the relative contribution of each muscle to the total thickness were determined. Weightlifters had significantly thicker absolute TrA and IO muscles than matched controls (p < 0.01). Further, the relative thickness of the IO was significantly greater in weightlifters than matched controls (p < 0.05). The findings of this study suggest that routine Olympic style weight training among female weightlifters appears to result in preferential hypertrophy or adaptation of the IO muscle. Copyright © 2011 Elsevier Ltd. All rights reserved.

  5. Sepsis attenuates the anabolic response to skeletal muscle contraction

    PubMed Central

    Steiner, Jennifer L.; Lang, Charles H.

    2014-01-01

    Electrically stimulated muscle contraction is a potential clinical therapy to treat sepsis-induced myopathy; however, whether sepsis alters contraction-induced anabolic signaling is unknown. Polymicrobial peritonitis was produced by cecal ligation and puncture (CLP) in male C57BL/6 mice and time-matched, pair-fed controls (CON). At ~24 h post-CLP, the right hindlimb was electrically stimulated via the sciatic nerve to evoke maximal muscle contractions and the gastrocnemius was collected 2 h later. Protein synthesis was increased by muscle contraction in CON mice. Sepsis suppressed the rate of synthesis in both the non-stimulated (31%) and stimulated (57%) muscle versus CON. Contraction of muscle in CON mice increased the phosphorylation of mTORC1 substrates S6K1 Thr389 (8-fold), S6K1 Thr421/Ser424 (7-fold) and 4E-BP1 Ser65 (11-fold). Sepsis blunted the contraction-induced phosphorylation of S6K1 Thr389 (67%), S6K1 Thr421/Ser424 (46%) and 4E-BP1 Ser65 (85%). Conversely, sepsis did not appear to modulate protein elongation as eEF2 Thr56 phosphorylation was decreased similarly by muscle contraction in both groups. MAPK signaling was discordant following muscle contraction in septic muscle; phosphorylation of ERK Thr202/Tyr204 and p38 Thr180/Tyr182 was increased similarly in both CON and CLP mice while sepsis prevented the contraction-induced phosphorylation of JNK Thr183/Tyr185 and c-JUN Ser63. The expression of IL-6 and TNF-α mRNA in muscle was increased by sepsis, and contraction increased TNF-α to a greater extent in muscle from septic than CON mice. Injection of the mTOR inhibitor Torin2 in separate mice confirmed that contraction-induced increases in S6K1 and 4E-BP1 were mTOR-mediated. These findings demonstrate that resistance to contraction-induced anabolic signaling occurs during sepsis and is predominantly mTORC1-dependent. PMID:25423127

  6. Sepsis attenuates the anabolic response to skeletal muscle contraction.

    PubMed

    Steiner, Jennifer L; Lang, Charles H

    2015-04-01

    Electrically stimulated muscle contraction is a potential clinical therapy to treat sepsis-induced myopathy; however, whether sepsis alters contraction-induced anabolic signaling is unknown. Polymicrobial peritonitis was produced by cecal ligation and puncture (CLP) in male C57BL/6 mice and time-matched, pair-fed controls (CON). At ∼24 h post-CLP, the right hindlimb was electrically stimulated via the sciatic nerve to evoke maximal muscle contractions, and the gastrocnemius was collected 2 h later. Protein synthesis was increased by muscle contraction in CON mice. Sepsis suppressed the rate of synthesis in both the nonstimulated (31%) and stimulated (57%) muscle versus CON. Contraction of muscle in CON mice increased the phosphorylation of mTORC1 (mammalian target of rapamycin [mTOR] complex 1) substrates S6K1 (70-kd ribosomal protein S6 kinase 1) Thr (8-fold), S6K1 ThrSer (7-fold) and 4E-BP1 Ser (11-fold). Sepsis blunted the contraction-induced phosphorylation of S6K1 Thr (67%), S6K1 ThrSer (46%), and 4E-BP1 Ser (85%). Conversely, sepsis did not appear to modulate protein elongation as eEF2 Thr phosphorylation was decreased similarly by muscle contraction in both groups. Mitogen-activated protein kinase signaling was discordant following contraction in septic muscle; phosphorylation of extracellular signal-regulated kinase ThrTyr and p38 ThrTyr was increased similarly in both CON and CLP mice, while sepsis prevented the contraction-induced phosphorylation of JNK ThrTyr and c-JUN Ser. The expression of interleukin 6 and tumor necrosis factor α (TNF-α) mRNA in muscle was increased by sepsis, and contraction increased TNF-α to a greater extent in muscle from septic than CON mice. Injection of the mTOR inhibitor Torin2 in separate mice confirmed that contraction-induced increases in S6K1 and 4E-BP1 were mTOR mediated. These findings demonstrate that resistance to contraction-induced anabolic signaling occurs during sepsis and is predominantly mTORC1-dependent.

  7. Verification of an optimized stimulation point on the abdominal wall for transcutaneous neuromuscular electrical stimulation for activation of deep lumbar stabilizing muscles.

    PubMed

    Baek, Seung Ok; Cho, Hee Kyung; Jung, Gil Su; Son, Su Min; Cho, Yun Woo; Ahn, Sang Ho

    2014-09-01

    Transcutaneous neuromuscular electrical stimulation (NMES) can stimulate contractions in deep lumbar stabilizing muscles. An optimal protocol has not been devised for the activation of these muscles by NMES, and information is lacking regarding an optimal stimulation point on the abdominal wall. The goal was to determine a single optimized stimulation point on the abdominal wall for transcutaneous NMES for the activation of deep lumbar stabilizing muscles. Ultrasound images of the spinal stabilizing muscles were captured during NMES at three sites on the lateral abdominal wall. After an optimal location for the placement of the electrodes was determined, changes in the thickness of the lumbar multifidus (LM) were measured during NMES. Three stimulation points were investigated using 20 healthy physically active male volunteers. A reference point R, 1 cm superior to the iliac crest along the midaxillary line, was used. Three study points were used: stimulation point S1 was located 2 cm superior and 2 cm medial to the anterior superior iliac spine, stimulation point S3 was 2 cm below the lowest rib along the same sagittal plane as S1, and stimulation point S2 was midway between S1 and S3. Sessions were conducted stimulating at S1, S2, or S3 using R for reference. Real-time ultrasound imaging (RUSI) of the abdominal muscles was captured during each stimulation session. In addition, RUSI images were captured of the LM during stimulation at S1. Thickness, as measured by RUSI, of the transverse abdominis (TrA), obliquus internus, and obliquus externus was greater during NMES than at rest for all three study points (p<.05). Transverse abdominis was significantly stimulated more by NMES at S1 than at the other points (p<.05). The LM thickness was also significantly greater during NMES at S1 than at rest (p<.05). Neuromuscular electrical stimulation at S1 optimally activated deep spinal stabilizing muscles, TrA and LM, as evidenced by RUSI. The authors recommend this

  8. Muscle contraction increases carnitine uptake via translocation of OCTN2

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Furuichi, Yasuro; Sugiura, Tomoko; Kato, Yukio

    Highlights: Black-Right-Pointing-Pointer Muscle contraction augmented carnitine uptake into rat hindlimb muscles. Black-Right-Pointing-Pointer An increase in carnitine uptake was due to an intrinsic clearance, not blood flow. Black-Right-Pointing-Pointer Histochemical analysis showed sarcolemmal OCTN2 was emphasized after contraction. Black-Right-Pointing-Pointer OCTN2 protein in sarcolemmal fraction was increased in contracting muscles. -- Abstract: Since carnitine plays an important role in fat oxidation, influx of carnitine could be crucial for muscle metabolism. OCTN2 (SLC22A5), a sodium-dependent solute carrier, is assumed to transport carnitine into skeletal muscle cells. Acute regulation of OCTN2 activity in rat hindlimb muscles was investigated in response to electrically induced contractile activity.more » The tissue uptake clearance (CL{sub uptake}) of L-[{sup 3}H]carnitine during muscle contraction was examined in vivo using integration plot analysis. The CL{sub uptake} of [{sup 14}C]iodoantipyrine (IAP) was also determined as an index of tissue blood flow. To test the hypothesis that increased carnitine uptake involves the translocation of OCTN2, contraction-induced alteration in the subcellular localization of OCTN2 was examined. The CL{sub uptake} of L-[{sup 3}H]carnitine in the contracting muscles increased 1.4-1.7-fold as compared to that in the contralateral resting muscles (p < 0.05). The CL{sub uptake} of [{sup 14}C]IAP was much higher than that of L-[{sup 3}H]carnitine, but no association between the increase in carnitine uptake and blood flow was obtained. Co-immunostaining of OCTN2 and dystrophin (a muscle plasma membrane marker) showed an increase in OCTN2 signal in the plasma membrane after muscle contraction. Western blotting showed that the level of sarcolemmal OCTN2 was greater in contracting muscles than in resting muscles (p < 0.05). The present study showed that muscle contraction facilitated carnitine uptake in skeletal muscles

  9. An investigation of abdominal muscle recruitment for sustained phonation in 25 healthy singers.

    PubMed

    Macdonald, Ian; Rubin, John S; Blake, Ed; Hirani, Shashi; Epstein, Ruth

    2012-11-01

    The purpose of this study was to investigate the baseline muscle thickness and recruitment patterns of the transversus abdominis muscle (TAM) and the internal oblique muscle (IOM) during semisupine phonation in a group of healthy performers. This was a 2 × 3×2 within-group, repeated-measure study in which 25 professional vocalists--12 male and 13 female performed a series of sustained pitches in differing vocal qualities. Measurements were taken with ultrasound (Sonosite Micromaxx Ultrasound System) of the baseline thickness and % recruitment during voicing, of two deep abdominal muscles--TAM and the IOM. Correlations between TAM and IOM absolute change scores, TAM and IOM percentage change scores, and changes in muscle thickness (absolute and percentage) and age were examined using Spearman's correlations. Gender differences in the four types of change scores within each combination of pitch and quality were conducted with one-way analysis of variances. Differences in muscle thickness change 1) absolute scores and 2) percentage change in TAM and IOM, by pitch and quality (and their interactions) were analyzed using linear mixed models, using restricted maximum likelihood estimations, employing a Toeplitz variance-covariance matrix structure in SPSS (IBM, 2011). Post hoc analyses for independent variable group differences used Sidak's correction for multiple comparisons. Alpha level was set to 0.05. In terms of absolute contractions (changes in the actual millimeter thickness of the muscle), the IOM was greater than the TAM. However in terms of percentage changes in muscles during phonation, the TAM was always greater than the IOM. The TAM as a percentage change was recruited preferentially and significantly in most vocal qualities tested. Although there were differences in muscle mass and recruitment patterns between genders, and males had thicker muscle mass at rest, differences due to muscle mass were not conclusive. Overall this study supports the argument

  10. Influence of exercise training on the oxidative capacity of rat abdominal muscles

    NASA Technical Reports Server (NTRS)

    Uribe, J. M.; Stump, C. S.; Tipton, C. M.; Fregosi, R. F.

    1992-01-01

    Our purpose was to determine if endurance exercise training would increase the oxidative capacity of the abdominal expiratory muscles of the rat. Accordingly, 9 male rats were subjected to an endurance training protocol (1 h/day, 6 days/week, 9 weeks) and 9 litter-mates served as controls. Citrate synthase (CS) activity was used as an index of oxidative capacity, and was determined in the following muscles: soleus, plantaris, costal diaphragm, crural diaphragm, and in all four abdominal muscles: rectus abdominis, transversus abdominis, external oblique, and internal oblique. Compared to their non-trained litter-mates, the trained rats had higher peak whole body oxygen consumption rates (+ 16%) and CS activities in plantaris (+34%) and soleus (+36%) muscles. Thus, the training program caused substantial systemic and locomotor muscle adaptations. The CS activity of costal diaphragm was 20% greater in the trained animals, but no difference was observed in crural diaphragm. The CS activity in the abdominal muscles was less than one-half of that in locomotor and diaphragm muscles, and there were no significant changes with training except in the rectus abdominis where a 26% increase was observed. The increase in rectus abdominis CS activity may reflect its role in postural support and/or locomotion, as none of the primary expiratory pumping muscles adapted to the training protocol. The relatively low levels of CS activity in the abdominal muscles suggests that they are not recruited frequently at rest, and the lack of an increase with training indicates that these muscles do not contribute significantly to the increased ventilatory activity accompanying exercise in the rat.

  11. An oblique muscle hematoma as a rare cause of severe abdominal pain: a case report.

    PubMed

    Shimodaira, Masanori; Kitano, Tomohiro; Kibata, Minoru; Shirahata, Kumiko

    2013-01-18

    Abdominal wall hematomas are an uncommon cause of acute abdominal pain and are often misdiagnosed. They are more common in elderly individuals, particularly in those under anticoagulant therapy. Most abdominal wall hematomas occur in the rectus sheath, and hematomas within the oblique muscle are very rare and are poorly described in the literature. Here we report the case of an oblique muscle hematoma in a middle-aged patient who was not under anticoagulant therapy. A 42-year-old Japanese man presented with a painful, enlarging, lateral abdominal wall mass, which appeared after playing baseball. Abdominal computed tomography and ultrasonography showed a large soft tissue mass located in the patient's left internal oblique muscle. A diagnosis of a lateral oblique muscle hematoma was made and the patient was treated conservatively. Physicians should consider an oblique muscle hematoma during the initial differential diagnosis of pain in the lateral abdominal wall even in the absence of anticoagulant therapy or trauma.

  12. Influence of prolonged unilateral cervical muscle contraction on head repositioning--decreased overshoot after a 5-min static muscle contraction task.

    PubMed

    Malmström, Eva-Maj; Karlberg, Mikael; Holmström, Eva; Fransson, Per-Anders; Hansson, Gert-Ake; Magnusson, Måns

    2010-06-01

    The ability to reproduce a specified head-on-trunk position can be an indirect test of cervical proprioception. This ability is affected in subjects with neck pain, but it is unclear whether and how much pain or continuous muscle contraction factors contribute to this effect. We studied the influence of a static unilateral neck muscle contraction task (5 min of lateral flexion at 30% of maximal voluntary contraction) on head repositioning ability in 20 subjects (10 women, 10 men; mean age 37 years) with healthy necks. Head repositioning ability was tested in the horizontal plane with 30 degrees target and neutral head position tests; head position was recorded by Zebris((R)), an ultrasound-based motion analyser. Head repositioning ability was analysed for accuracy (mean of signed differences between introduced and reproduced positions) and precision (standard deviation of the differences). Accuracy of head repositioning ability increased significantly after the muscle contraction task, as the normal overshoot was reduced. An average overshoot of 7.1 degrees decreased to 4.6 degrees after the muscle contraction task for the 30 degrees target and from 2.2 degrees to 1.4 degrees for neutral head position. The increased accuracy was most pronounced for movements directed towards the activated side. Hence, prolonged unilateral neck muscle contraction may increase the sensitivity of cervical proprioceptors.

  13. Energetic aspects of skeletal muscle contraction: implications of fiber types.

    PubMed

    Rall, J A

    1985-01-01

    In this chapter fundamental energetic properties of skeletal muscles as elucidated from isolated muscle preparations are described. Implications of these intrinsic properties for the energetic characterization of different fiber types and for the understanding of locomotion have been considered. Emphasis was placed on the myriad of physical and chemical techniques that can be employed to understand muscle energetics and on the interrelationship of results from different techniques. The anaerobic initial processes which liberate energy during contraction and relaxation are discussed in detail. The high-energy phosphate (approximately P) utilized during contraction and relaxation can be distributed between actomyosin ATPase or cross-bridge cycling (70%) and the Ca2+ ATPase of the sacroplasmic reticulum (30%). Muscle shortening increases the rate of approximately P hydrolysis, and stretching a muscle during contraction suppresses the rate of approximately P hydrolysis. The economy of an isometric contraction is defined as the ratio of isometric mechanical response to energetic cost and is shown to be a fundamental intrinsic parameter describing muscle energetics. Economy of contraction varies across the animal kingdom by over three orders of magnitude and is different in different mammalian fiber types. In mammalian skeletal muscles differences in economy of contraction can be attributed mainly to differences in the specific actomyosin and Ca2+ ATPase of muscles. Furthermore, there is an inverse relationship between economy of contraction and maximum velocity of muscle shortening (Vmax) and maximum power output. This is a fundamental relationship. Muscles cannot be economical at developing and maintaining force and also exhibit rapid shortening. Interestingly, there appears to be a subtle system of unknown nature that modulates the Vmax and economy of contraction. Efficiency of a work-producing contraction is defined and contrasted to the economy of contraction

  14. Imaging two-dimensional mechanical waves of skeletal muscle contraction.

    PubMed

    Grönlund, Christer; Claesson, Kenji; Holtermann, Andreas

    2013-02-01

    Skeletal muscle contraction is related to rapid mechanical shortening and thickening. Recently, specialized ultrasound systems have been applied to demonstrate and quantify transient tissue velocities and one-dimensional (1-D) propagation of mechanical waves during muscle contraction. Such waves could potentially provide novel information on musculoskeletal characteristics, function and disorders. In this work, we demonstrate two-dimensional (2-D) mechanical wave imaging following the skeletal muscle contraction. B-mode image acquisition during multiple consecutive electrostimulations, speckle-tracking and a time-stamp sorting protocol were used to obtain 1.4 kHz frame rate 2-D tissue velocity imaging of the biceps brachii muscle contraction. The results present novel information on tissue velocity profiles and mechanical wave propagation. In particular, counter-propagating compressional and shear waves in the longitudinal direction were observed in the contracting tissue (speed 2.8-4.4 m/s) and a compressional wave in the transverse direction of the non-contracting muscle tissue (1.2-1.9 m/s). In conclusion, analysing transient 2-D tissue velocity allows simultaneous assessment of both active and passive muscle tissue properties. Copyright © 2013 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  15. The effects of running in place in a limited area with abdominal drawing-in maneuvers on abdominal muscle thickness in chronic low back pain patients.

    PubMed

    Gong, Wontae

    2016-11-21

    Based on previous studies indicating that core stabilization exercises accompanied by abdominal drawing-in maneuvers increase the thickness of the transversus abdominis muscle. The purpose of this study was to compare the measurements of abdominal muscle thicknesses during running in place in a limited area with the abdominal drawing-in maneuver. The study classified the subjects into two experimental groups: the training group (M = 2, F = 13), and the control group (M = 2, F = 13). The training group performed three sets of running in place in a limited area with abdominal drawing-in maneuvers each time, three times a week for six weeks. The abdominal muscle thicknesses of the subjects were measured using ultrasonography. Comparing the training group's abdominal muscle thickness before and after this study, there was a statistical significance in all of the external obliquus abdominis, the internal obliquus abdominis, and the transversus abdominis. In particular, thicknesses of external obliquus abdominis and internal obliquus increased remarkably. Running in place in a limited area accompanied by abdominal drawing-in maneuvers increased the thickness of the deep abdominal muscles that are the basis of trunk stabilization.

  16. Training through gametherapy promotes coactivation of the pelvic floor and abdominal muscles in young women, nulliparous and continents

    PubMed Central

    Silva, Valeria Regina; Riccetto, Cássio; Martinho, Natalia Miguel; Marques, Joseane; Carvalho, Leonardo Cesar; Botelho, Simone

    2016-01-01

    ABSTRACT Introduction and objectives: Several studies have been investigated co-activation can enhance the effectveness of PFM training protocols allowing preventive and therapeutic goals in pelvic floor dysfunctions. The objective of the present study was to investigate if an abdominal-pelvic protocol of training (APT) using gametherapy would allow co-activation of PFM and transversus abdominis/oblique internal (TrA/OI) muscles. Patients and methods: Twenty-five nulliparous, continent, young females, with median age 24.76 (±3.76) years were evaluated using digital palpation (DP) of PFM and surface electromyography of PFM and TrA/OI simultaneously, during maximal voluntary contraction (MVC), alternating PFM and TrA/OI contraction requests. All women participated on a supervised program of APT using gametherapy, that included exercises of pelvic mobilization associated to contraction of TrA/OI muscles oriented by virtual games, for 30 minutes, three times a week, in a total of 10 sessions. Electromyographic data were processed and analyzed by ANOVA - analysis of variance. Results: When MVC of TrA/OI was solicited, it was observed simultaneous increase of electromyographic activity of PFM (p=0.001) following ATP. However, EMG activity did not change significantly during MVC of PFM. Conclusion: Training using gametherapy allowed better co-activation of pelvic floor muscles in response to contraction of TrA, in young nulliparous and continent women. PMID:27564290

  17. Training through gametherapy promotes coactivation of the pelvic floor and abdominal muscles in young women, nulliparous and continents.

    PubMed

    Silva, Valeria Regina; Riccetto, Cássio Luis Zanettini; Martinho, Natalia Miguel; Marques, Joseane; Carvalho, Leonardo Cesar; Botelho, Simone

    2016-01-01

    several studies have been investigated co-activation can enhance the effectveness of PFM training protocols allowing preventive and therapeutic goals in pelvic floor dysfunctions. The objective of the present study was to investigate if an abdominal-pelvic protocol of training (APT) using gametherapy would allow co-activation of PFM and transversus abdominis/oblique internal (TrA/OI) muscles. Twenty-five nulliparous, continent, young females, with median age 24.76 (±3.76) years were evaluated using digital palpation (DP) of PFM and surfasse electromyography of PFM and TrA/OI simultaneously, during maximal voluntary contraction (MVC), alternating PFM and TrA/OI contraction requests. All women participated on a supervised program of APT using gametherapy, that included exercises of pelvic mobilization associated to contraction of TrA/OI muscles oriented by virtual games, for 30 minutes, three times a week, in a total of 10 sessions. Electromyographic data were processed and analyzed by ANOVA - analysis of variance. When MVC of TrA/OI was solicited, it was observed simultaneous increase of electromyographic activity of PFM (p=0.001) following ATP. However, EMG activity did not change significantly during MVC of PFM. Training using gametherapy allowed better co-activation of pelvic floor muscles in response to contraction of TrA, in young nulliparous and continent women. Copyright© by the International Brazilian Journal of Urology.

  18. Association of visceral fat area with abdominal skeletal muscle distribution in overweight Japanese adults.

    PubMed

    Tanaka, Noriko I; Murakami, Haruka; Ohmori, Yumi; Aiba, Naomi; Morita, Akemi; Watanabe, Shaw; Miyachi, Motohiko

    2016-07-20

    Quantitative evaluation of visceral fat mass and skeletal muscle mass is important for health promotion. Recently, some studies suggested the existence of adipocyte-myocyte negative crosstalk. If so, abdominal skeletal muscles may easily and negatively affected not only by the age but also the visceral fat because age-related reduction in abdominal region is greater compared with limbs. We cross-sectionally examined the existence of quantitative associations between visceral fat area and abdominal skeletal muscle distribution in overweight people. A total of 230 Japanese males and females who aged 40-64 years and whose body mass index (BMI) was 28.0-44.8kg/m 2 participated in this study. The cross-sectional area (CSA) of the visceral fat, subcutaneous fat, and abdominal skeletal muscles, namely, the rectus abdominis, abdominal oblique, erector spinae, and iliopsoas muscles were measured by the computed tomography images. Stepwise regression analyses revealed the existence of sex difference in the relation between visceral fat CSA and other morphological variables. In males, BMI was a positive, and the iliopsoas muscle group CSA was a negative contributor of the visceral fat CSA. In females, both age and BMI were selected as positive contributors. These data suggested that the visceral fat CSA may negatively associated with iliopsoas muscle group CSA in males. In females, the visceral fat CSA was not significantly related to the distribution of the abdominal skeletal muscle groups. Copyright © 2016 Asia Oceania Association for the Study of Obesity. Published by Elsevier Ltd. All rights reserved.

  19. Capsiate supplementation reduces oxidative cost of contraction in exercising mouse skeletal muscle in vivo.

    PubMed

    Yashiro, Kazuya; Tonson, Anne; Pecchi, Émilie; Vilmen, Christophe; Le Fur, Yann; Bernard, Monique; Bendahan, David; Giannesini, Benoît

    2015-01-01

    Chronic administration of capsiate is known to accelerate whole-body basal energy metabolism, but the consequences in exercising skeletal muscle remain very poorly documented. In order to clarify this issue, the effect of 2-week daily administration of either vehicle (control) or purified capsiate (at 10- or 100-mg/kg body weight) on skeletal muscle function and energetics were investigated throughout a multidisciplinary approach combining in vivo and in vitro measurements in mice. Mechanical performance and energy metabolism were assessed strictly non-invasively in contracting gastrocnemius muscle using magnetic resonance (MR) imaging and 31-phosphorus MR spectroscopy (31P-MRS). Regardless of the dose, capsiate treatments markedly disturbed basal bioenergetics in vivo including intracellular pH alkalosis and decreased phosphocreatine content. Besides, capsiate administration did affect neither mitochondrial uncoupling protein-3 gene expression nor both basal and maximal oxygen consumption in isolated saponin-permeabilized fibers, but decreased by about twofold the Km of mitochondrial respiration for ADP. During a standardized in vivo fatiguing protocol (6-min of repeated maximal isometric contractions electrically induced at a frequency of 1.7 Hz), both capsiate treatments reduced oxidative cost of contraction by 30-40%, whereas force-generating capacity and fatigability were not changed. Moreover, the rate of phosphocreatine resynthesis during the post-electrostimulation recovery period remained unaffected by capsiate. Both capsiate treatments further promoted muscle mass gain, and the higher dose also reduced body weight gain and abdominal fat content. These findings demonstrate that, in addition to its anti-obesity effect, capsiate supplementation improves oxidative metabolism in exercising muscle, which strengthen this compound as a natural compound for improving health.

  20. The effects of surface condition on abdominal muscle activity during single-legged hold exercise.

    PubMed

    Ha, Sung-min; Oh, Jae-seop; Jeon, In-cheol; Kwon, Oh-yun

    2015-02-01

    To treat low-back pain, various spinal stability exercises are commonly used to improve trunk muscle function and strength. Because human movement for normal daily activity occurs in multi-dimensions, the importance of exercise in multi-dimensions or on unstable surfaces has been emphasized. Recently, a motorized rotating platform (MRP) for facilitating multi-dimensions dynamic movement was introduced for clinical use. However, the abdominal muscle activity with this device has not been reported. The purpose of this study was to compare the abdominal muscle activity (rectus abdominis, external and internal oblique muscles) during an active single-leg-hold (SLH) exercise on a floor (stable surface), foam roll, and motorized rotating platform (MRP). Thirteen healthy male subjects participated in this study. Using electromyography, the abdominal muscle activity was measured while the subjects performed SLH exercises on floor (stable surface), foam roll, and MRP. There were significant differences in the abdominal muscle activities among conditions (P<.05), except for left EO (P>.05) (Fig. 2). After the Bonferroni correction, however, no significant differences among conditions remained, except for differences in both side IO muscle activity between the floor and foam roll conditions (padj<0.017). The findings suggest that performing the SLH exercises on a foam roll and MRP is more effective increased activities of both side of RA and IO, and Rt. EO compared to floor condition. However, there were no significant differences in abdominal muscles activity in the multiple comparison between conditions (mean difference were smaller than the standard deviation in the abdominal muscle activities) (padj>0.017), except for differences in both side IO muscle activity between the floor (stable surface) and foam roll (padj<0.017) (effect size: 0.79/0.62 (non-supporting/supporting leg) for foam-roll versus floor). Copyright © 2014 Elsevier Ltd. All rights reserved.

  1. The role of titin in eccentric muscle contraction.

    PubMed

    Herzog, Walter

    2014-08-15

    Muscle contraction and force regulation in skeletal muscle have been thought to occur exclusively through the relative sliding of and the interaction between the contractile filaments actin and myosin. While this two-filament sarcomere model has worked well in explaining the properties of isometrically and concentrically contracting muscle, it has failed miserably in explaining experimental observations in eccentric contractions. Here, I suggest, and provide evidence, that a third filament, titin, is involved in force regulation of sarcomeres by adjusting its stiffness in an activation-dependent (calcium) and active force-dependent manner. Upon muscle activation, titin binds calcium at specific sites, thereby increasing its stiffness, and cross-bridge attachment to actin is thought to free up binding sites for titin on actin, thereby reducing titin's free-spring length, thus increasing its stiffness and force upon stretch of active muscle. This role of titin as a third force regulating myofilament in sarcomeres, although not fully proven, would account for many of the unexplained properties of eccentric muscle contraction, while simultaneously not affecting the properties predicted by the two-filament cross-bridge model in isometric and concentric muscle function. Here, I identify the problems of the two-filament sarcomere model and demonstrate the advantages of the three-filament model by providing evidence of titin's contribution to active force in eccentric muscle function. © 2014. Published by The Company of Biologists Ltd.

  2. Contributions of Central Command and Muscle Feedback to Sympathetic Nerve Activity in Contracting Human Skeletal Muscle.

    PubMed

    Boulton, Daniel; Taylor, Chloe E; Macefield, Vaughan G; Green, Simon

    2016-01-01

    During voluntary contractions, muscle sympathetic nerve activity (MSNA) to contracting muscles increases in proportion to force but the underlying mechanisms are not clear. To shed light on these mechanisms, particularly the influences of central command and muscle afferent feedback, the present study tested the hypothesis that MSNA is greater during voluntary compared with electrically-evoked contractions. Seven male subjects performed a series of 1-min isometric dorsiflexion contractions (left leg) separated by 2-min rest periods, alternating between voluntary and electrically-evoked contractions at similar forces (5-10% of maximum). MSNA was recorded continuously (microneurography) from the left peroneal nerve and quantified from cardiac-synchronized, negative-going spikes in the neurogram. Compared with pre-contraction values, MSNA increased by 51 ± 34% (P < 0.01) during voluntary contractions but did not change significantly during electrically-evoked contractions (-8 ± 12%, P > 0.05). MSNA analyzed at 15-s intervals revealed that this effect of voluntary contraction appeared 15-30 s after contraction onset (P < 0.01), remained elevated until the end of contraction, and disappeared within 15 s after contraction. These findings suggest that central command, and not feedback from contracting muscle, is the primary mechanism responsible for the increase in MSNA to contracting muscle. The time-course of MSNA suggests that there is a longer delay in the onset of this effect compared with its cessation after contraction.

  3. Two-wave model of the muscle contraction.

    PubMed

    Molski, Marcin

    2009-05-01

    The Matsuno model of the muscle contraction is considered in the framework of the two-wave Corben's theory of composite objects built up of both time- and space-like components. It has been proved that during muscle contraction the locally coherent aggregates distributed along the actin filament interact by means of space-like fields, which are solutions of the relativistic Feinberg equation. The existence of such interactions and lack of decoherence are conditions sine qua non for appearance of the quantum entanglement between actin monomers in an ATP-activated filament. A possible role of a quantum potential in the muscle contraction is discussed and the mass of the carrier of space-like interactions is estimated m0' = 7.3 x 10(-32) g (46 eV).

  4. Influence of adequate pelvic floor muscle contraction on the movement of the coccyx during pelvic floor muscle training.

    PubMed

    Fujisaki, Akiko; Shigeta, Miwa; Shimoinaba, Misa; Yoshimura, Yasukuni

    2018-04-01

    [Purpose] Pelvic floor muscle training is a first-line therapy for female stress urinary incontinence. Previous studies have suggested that the coccyx tip moves ventrally and cranially during pelvic floor muscle contraction. The study aimed to elucidate the influence of adequate pelvic floor muscle contraction on coccyx movement. [Subjects and Methods] Sixty-three females (57 patients with stress urinary incontinence and additional 6 healthy volunteers) were enrolled. Using magnetic resonance imaging, coccyx movement was evaluated during pelvic floor muscle contraction and strain. An adequate contraction was defined as a contraction with good Oxford grading scale [≥3] and without inadequate muscle substitution patterns. [Results] Inadequate muscle substitution patterns were observed in 33 participants (52.4%). No significant difference was observed in the movement of the coccyx tip in the ventrodorsal direction between females with and without inadequate muscle substitution patterns. However, a significant increase in the movement of the coccyx tip in the cranial direction was detected in the group without inadequate muscle substitution patterns. Compared to participants with inadequate pelvic floor muscle contraction, those who had adequate pelvic floor muscle contraction exhibited significantly increased cranial movement of the coccyx. [Conclusion] Adequate pelvic floor muscle contraction can produce cranial movement of the coccyx tip.

  5. Muscle co-contraction patterns in robot-mediated force field learning to guide specific muscle group training.

    PubMed

    Pizzamiglio, Sara; Desowska, Adela; Shojaii, Pegah; Taga, Myriam; Turner, Duncan L

    2017-01-01

    Muscle co-contraction is a strategy of increasing movement accuracy and stability employed in dealing with force perturbation of movement. It is often seen in neuropathological populations. The direction of movement influences the pattern of co-contraction, but not all movements are easily achievable for populations with motor deficits. Manipulating the direction of the force instead, may be a promising rehabilitation protocol to train movement with use of a co-contraction reduction strategy. Force field learning paradigms provide a well described procedure to evoke and test muscle co-contraction. The aim of this study was to test the muscle co-contraction pattern in a wide range of arm muscles in different force-field directions utilising a robot-mediated force field learning paradigm of motor adaptation. Forty-two participants volunteered to participate in a study utilising robot-mediated force field motor adaptation paradigm with a clockwise or counter-clockwise force field. Kinematics and surface electromyography (EMG) of eight arm muscles were measured. Both muscle activation and co-contraction was earlier and stronger in flexors in the clockwise condition and in extensors in the counter-clockwise condition. Manipulating the force field direction leads to changes in the pattern of muscle co-contraction.

  6. Simulation studies of circular muscle contraction, longitudinal muscle shortening, and their coordination in esophageal transport.

    PubMed

    Kou, Wenjun; Pandolfino, John E; Kahrilas, Peter J; Patankar, Neelesh A

    2015-08-15

    On the basis of a fully coupled active musculomechanical model for esophageal transport, we aimed to find the roles of circular muscle (CM) contraction and longitudinal muscle (LM) shortening in esophageal transport, and the influence of their coordination. Two groups of studies were conducted using a computational model. In the first group, bolus transport with only CM contraction, only LM shortening, or both was simulated. Overall features and detailed information on pressure and the cross-sectional area (CSA) of mucosal and the two muscle layers were analyzed. In the second group, bolus transport with varying delay in CM contraction or LM shortening was simulated. The effect of delay on esophageal transport was studied. For cases showing abnormal transport, pressure and CSA were further analyzed. CM contraction by itself was sufficient to transport bolus, but LM shortening by itself was not. CM contraction decreased the CSA and the radius of the muscle layer locally, but LM shortening increased the CSA. Synchronized CM contraction and LM shortening led to overlapping of muscle CSA and pressure peaks. Advancing LM shortening adversely influenced bolus transport, whereas lagging LM shortening was irrelevant to bolus transport. In conclusion, CM contraction generates high squeezing pressure, which plays a primary role in esophageal transport. LM shortening increases muscle CSA, which helps to strengthen CM contraction. Advancing LM shortening decreases esophageal distensibility in the bolus region. Lagging LM shortening no longer helps esophageal transport. Synchronized CM contraction and LM shortening seems to be most effective for esophageal transport. Copyright © 2015 the American Physiological Society.

  7. Diaphragmatic lymphatic vessel behavior during local skeletal muscle contraction.

    PubMed

    Moriondo, Andrea; Solari, Eleonora; Marcozzi, Cristiana; Negrini, Daniela

    2015-02-01

    The mechanism through which the stresses developed in the diaphragmatic tissue during skeletal muscle contraction sustain local lymphatic function was studied in 10 deeply anesthetized, tracheotomized adult Wistar rats whose diaphragm was exposed after thoracotomy. To evaluate the direct effect of skeletal muscle contraction on the hydraulic intraluminal lymphatic pressures (Plymph) and lymphatic vessel geometry, the maximal contraction of diaphragmatic fibers adjacent to a lymphatic vessel was elicited by injection of 9.2 nl of 1 M KCl solution among diaphragmatic fibers while Plymph was recorded through micropuncture and vessel geometry via stereomicroscopy video recording. In lymphatics oriented perpendicularly to the longitudinal axis of muscle fibers and located at <300 μm from KCl injection, vessel diameter at maximal skeletal muscle contraction (Dmc) decreased to 61.3 ± 1.4% of the precontraction value [resting diameter (Drest)]; however, if injection was at >900 μm from the vessel, Dmc enlarged to 131.1 ± 2.3% of Drest. In vessels parallel to muscle fibers, Dmc increased to 122.8 ± 2.9% of Drest. During contraction, Plymph decreased as much as 22.5 ± 2.6 cmH2O in all submesothelial superficial vessels, whereas it increased by 10.7 ± 5.1 cmH2O in deeper vessels running perpendicular to contracting muscle fibers. Hence, the three-dimensional arrangement of the diaphragmatic lymphatic network seems to be finalized to efficiently exploit the stresses exerted by muscle fibers during the contracting inspiratory phase to promote lymph formation in superficial submesothelial lymphatics and its further propulsion in deeper intramuscular vessels. Copyright © 2015 the American Physiological Society.

  8. Protons act as a transmitter for muscle contraction in C. elegans.

    PubMed

    Beg, Asim A; Ernstrom, Glen G; Nix, Paola; Davis, M Wayne; Jorgensen, Erik M

    2008-01-11

    Muscle contraction is normally mediated by the release of neurotransmitters from motor neurons. Here we demonstrate that protons can act as a direct transmitter from intestinal cells to stimulate muscle contraction. During the C. elegans defecation motor program the posterior body muscles contract even in the absence of neuronal inputs or vesicular neurotransmission. In this study, we demonstrate that the space between the intestine and the muscle is acidified just prior to muscle contraction and that the release of caged protons is sufficient to induce muscle contraction. PBO-4 is a putative Na+/H+ ion exchanger expressed on the basolateral membrane of the intestine, juxtaposed to the posterior body muscles. In pbo-4 mutants the extracellular space is not acidified and the muscles fail to contract. The pbo-5 and pbo-6 genes encode subunits of a "cys-loop" proton-gated cation channel required for muscles to respond to acidification. In heterologous expression assays the PBO receptor is half-maximally activated at a pH of 6.8. The identification of the mechanisms for release and reception of proton signals establishes a highly unusual mechanism for intercellular communication.

  9. Protons act as a transmitter for muscle contraction in C. elegans

    PubMed Central

    Beg, Asim A.; Ernstrom, Glen G.; Nix, Paola; Davis, M. Wayne; Jorgensen, Erik M.

    2008-01-01

    Muscle contraction is normally mediated by the release of neurotransmitters from motor neurons. Here we demonstrate that protons can act as a direct transmitter from intestinal cells to stimulate muscle contraction. During the C. elegans defecation motor program the posterior body muscles contract even in the absence of neuronal inputs or vesicular neurotransmission. In this study, we demonstrate that the space between the intestine and the muscle is acidified just prior to muscle contraction and that the release of caged protons is sufficient to induce muscle contraction. PBO-4 is a putative Na+/H+ ion exchanger expressed on the basolateral membrane of the intestine, juxtaposed to the posterior body muscles. In pbo-4 mutants the extracellular space is not acidified and the muscles fail to contract. The pbo-5 and pbo-6 genes encode subunits of a ‘cys-loop’ proton-gated cation channel required for muscles to respond to acidification. In heterologous expression assays the PBO receptor is half-maximally activated at a pH of 6.8. The identification of the mechanisms for release and reception of proton signals establishes a highly unusual mechanism for intercellular communication. PMID:18191228

  10. [Postpartum pelvic floor muscle training and abdominal rehabilitation: Guidelines].

    PubMed

    Deffieux, X; Vieillefosse, S; Billecocq, S; Battut, A; Nizard, J; Coulm, B; Thubert, T

    2015-12-01

    Provide guidelines for clinical practice concerning postpartum rehabilitation. Systematically review of the literature concerning postpartum pelvic floor muscle training and abdominal rehabilitation. Pelvic-floor rehabilitation using pelvic floor muscle contraction exercises is recommended to treat persistent urinary incontinence at 3 months postpartum (grade A), regardless of the type of incontinence. At least 3 guided sessions with a therapist is recommended, associated with pelvic floor muscle exercises at home. This postpartum rehabilitation improves short-term urinary incontinence (1 year) but not long-term (6-12 years). Early pelvic-floor rehabilitation (within 2 months following childbirth) is not recommended (grade C). Postpartum pelvic-floor rehabilitation in women presenting with anal incontinence, is associated with a lower prevalence of anal incontinence symptoms in short-term (1 year) (EL3) but not long-term (6 and 12) (EL3). Postpartum pelvic-floor rehabilitation is recommended to treat anal incontinence (grade C) but results are not maintained in medium or long term. No randomized trials have evaluated the pelvic-floor rehabilitation in asymptomatic women in order to prevent urinary or anal incontinence in medium or long term. It is therefore not recommended (expert consensus). Rehabilitation supervised by a therapist (physiotherapist or midwife) is not associated with better results than simple advice for voluntary contraction of the pelvic floor muscles to prevent/correct, in short term (6 months), a persistent prolapse 6 weeks postpartum (EL2), whether or not with a levator ani avulsion (EL3). Postpartum pelvic-floor rehabilitation is not associated with a decrease in the prevalence of dyspareunia at 1-year follow-up (EL3). Postpartum pelvic-floor rehabilitation guided by a therapist is therefore not recommended to treat or prevent prolapse (grade C) or dyspareunia (grade C). No randomized trials have evaluated the effect of pelvic

  11. Prior history of FDI muscle contraction: different effect on MEP amplitude and muscle activity.

    PubMed

    Talis, V L; Kazennikov, O V; Castellote, J M; Grishin, A A; Ioffe, M E

    2014-03-01

    Motor evoked potentials (MEPs) in the right first dorsal interosseous (FDI) muscle elicited by transcranial magnetic stimulation of left motor cortex were assessed in ten healthy subjects during maintenance of a fixed FDI contraction level. Subjects maintained an integrated EMG (IEMG) level with visual feedback and reproduced this level by memory afterwards in the following tasks: stationary FDI muscle contraction at the level of 40 ± 5 % of its maximum voluntary contraction (MVC; 40 % task), at the level of 20 ± 5 % MVC (20 % task), and also when 20 % MVC was preceded by either no contraction (0-20 task), by stronger muscle contraction (40-20 task) or by no contraction with a previous strong contraction (40-0-20 task). The results show that the IEMG level was within the prescribed limits when 20 and 40 % stationary tasks were executed with and without visual feedback. In 0-20, 40-20, and 40-0-20 tasks, 20 % IEMG level was precisely controlled in the presence of visual feedback, but without visual feedback the IEMG and force during 20 % IEMG maintenance were significantly higher in the 40-0-20 task than those in 0-20 and 40-20 tasks. That is, without visual feedback, there were significant variations in muscle activity due to different prehistory of contraction. In stationary tasks, MEP amplitudes in 40 % task were higher than in 20 % task. MEPs did not differ significantly during maintenance of the 20 % level in tasks with different prehistory of muscle contraction with and without visual feedback. Thus, in spite of variations in muscle background activity due to different prehistory of contraction MEPs did not vary significantly. This dissociation suggests that the voluntary maintenance of IEMG level is determined not only by cortical mechanisms, as reflected by corticospinal excitability, but also by lower levels of CNS, where afferent signals and influences from other brain structures and spinal cord are convergent.

  12. YFa and analogs: Investigation of opioid receptors in smooth muscle contraction

    PubMed Central

    Kumar, Krishan; Goyal, Ritika; Mudgal, Annu; Mohan, Anita; Pasha, Santosh

    2011-01-01

    AIM: To study the pharmacological profile and inhibition of smooth muscle contraction by YFa and its analogs in conjunction with their receptor selectivity. METHODS: The effects of YFa and its analogs (D-Ala2) YFa, Y (D-Ala2) GFMKKKFMRF amide and Des-Phe-YGGFMKKKFMR amide in guinea pig ileum (GPI) and mouse vas deferens (MVD) motility were studied using an isolated tissue organ bath system, and morphine and DynA (1-13) served as controls. Acetylcholine was used for muscle stimulation. The observations were validated by specific antagonist pretreatment experiments using naloxonazine, naltrindole and norbinaltorphimine norBNI. RESULTS: YFa did not demonstrate significant inhibition of GPI muscle contraction as compared with morphine (15% vs 62%, P = 0.0002), but moderate inhibition of MVD muscle contraction, indicating the role of κ opioid receptors in the contraction. A moderate inhibition of GPI muscles by (Des-Phe) YFa revealed the role of anti-opiate receptors in the smooth muscle contraction. (D-Ala-2) YFa showed significant inhibition of smooth muscle contraction, indicating the involvement of mainly δ receptors in MVD contraction. These results were supported by specific antagonist pretreatment assays. CONCLUSION: YFa revealed its side-effect-free analgesic properties with regard to arrest of gastrointestinal transit. The study provides evidences for the involvement of κ and anti-opioid receptors in smooth muscle contraction. PMID:22110284

  13. YFa and analogs: investigation of opioid receptors in smooth muscle contraction.

    PubMed

    Kumar, Krishan; Goyal, Ritika; Mudgal, Annu; Mohan, Anita; Pasha, Santosh

    2011-10-28

    To study the pharmacological profile and inhibition of smooth muscle contraction by YFa and its analogs in conjunction with their receptor selectivity. The effects of YFa and its analogs (D-Ala2) YFa, Y (D-Ala2) GFMKKKFMRF amide and Des-Phe-YGGFMKKKFMR amide in guinea pig ileum (GPI) and mouse vas deferens (MVD) motility were studied using an isolated tissue organ bath system, and morphine and DynA (1-13) served as controls. Acetylcholine was used for muscle stimulation. The observations were validated by specific antagonist pretreatment experiments using naloxonazine, naltrindole and norbinaltorphimine norBNI. YFa did not demonstrate significant inhibition of GPI muscle contraction as compared with morphine (15% vs 62%, P = 0.0002), but moderate inhibition of MVD muscle contraction, indicating the role of κ opioid receptors in the contraction. A moderate inhibition of GPI muscles by (Des-Phe) YFa revealed the role of anti-opiate receptors in the smooth muscle contraction. (D-Ala-2) YFa showed significant inhibition of smooth muscle contraction, indicating the involvement of mainly δ receptors in MVD contraction. These results were supported by specific antagonist pretreatment assays. YFa revealed its side-effect-free analgesic properties with regard to arrest of gastrointestinal transit. The study provides evidences for the involvement of κ and anti-opioid receptors in smooth muscle contraction.

  14. Effects of muscle contraction on cervical vestibular evoked myogenic potentials in normal subjects.

    PubMed

    Rosengren, Sally M

    2015-11-01

    Cervical vestibular evoked myogenic potentials (cVEMPs) are vestibular-dependent muscle reflexes recorded from the sternocleidomastoid (SCM) muscles in humans. cVEMP amplitude is modulated by stimulus intensity and SCM muscle contraction strength, but the effect of muscle contraction is less well-documented. The effects of intensity and contraction were therefore compared in 25 normal subjects over a wide range of contractions. cVEMPs were recorded at different contraction levels while holding stimulus intensity constant and at different intensities while holding SCM contraction constant. The effect of muscle contraction on cVEMP amplitude was linear for most of the range of muscle contractions in the majority of subjects (mean R(2)=0.93), although there were some nonlinearities when the contraction was either very weak or very strong. Very weak contractions were associated with absent responses, incomplete morphology and prolonged p13 latencies. Normalization of amplitudes, by dividing the p13-n23 amplitude by the muscle contraction estimate, reduced the effect of muscle contraction, but tended to underestimate the amplitude with weak contractions. Minimum contraction levels are required for accurate interpretation of cVEMPs. These data highlight the importance of measuring SCM contraction strength when recording cVEMPs. Copyright © 2015 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

  15. Importance of contraction history on muscle force of porcine urinary bladder smooth muscle.

    PubMed

    Menzel, Robin; Böl, Markus; Siebert, Tobias

    2017-02-01

    The purpose of this study was to provide a comprehensive dataset of porcine urinary bladder smooth muscle properties. Particularly, the history dependence of force production, namely force depression (FD) following shortening and force enhancement (FE) following stretch, was analysed. During active micturition, the circumference of the urinary bladder changes enormously. Thus, FD might be an important phenomenon during smooth muscle contraction. Electrically stimulated, intact urinary bladder strips from pigs (n = 10) were suspended in an aerated-filled organ bath, and different isometric, isotonic, and isokinetic contraction protocols were performed to determine the force-length and the force-velocity relation. FD and FE were assessed in concentric and eccentric contractions with different ramp lengths and ramp velocities. Bladder smooth muscles exhibit considerable amounts of FD and FE. The amount of FD increased significantly with ramp length, while FE did not change. However, FE and FD were independent of ramp velocity. The results imply that smooth muscle bladder strips exhibit similar muscle properties and history-dependent behaviour compared to striated muscles. The provided dataset of muscle properties is important for bladder modelling as well as for the analyses and interpretation of dynamic bladder filling and voiding.

  16. Ultrasound elastography-based assessment of the elasticity of the supraspinatus muscle and tendon during muscle contraction.

    PubMed

    Muraki, Takayuki; Ishikawa, Hiroaki; Morise, Shuhei; Yamamoto, Nobuyuki; Sano, Hirotaka; Itoi, Eiji; Izumi, Shin-ichi

    2015-01-01

    Although elasticity of the supraspinatus muscle and tendon is a useful parameter to represent the conditions of the supraspinatus muscle and tendon, assessment of the elasticity in clinical settings has not been established. The purpose of this study was to determine the elasticity of the supraspinatus muscle belly and tendon under different muscle contraction conditions using ultrasound real-time tissue elastography (RTE). Twenty-three healthy individuals participated in this study. Ultrasound RTE was used for elasticity measurements of the muscle belly and tendon of the supraspinatus muscle. The elasticity was defined as the ratio of strain in the tissues to that in an acoustic coupler (reference). A greater ratio indicated that the tissue was softer. Measurements were performed with study subjects in the lateral decubitus position at 10° of shoulder abduction under conditions of (1) no contraction, (2) isometric contraction without a weight, and (3) isometric contraction with a 1-kg weight. The intraclass correlation coefficient (ICC1,3) of 3 measurements under each condition ranged from 0.931 to 0.998, showing high intraobserver reliability. Strain ratios for both the supraspinatus muscle belly and tendon significantly decreased with increases in muscle contraction (P < .001). Ultrasound RTE with the acoustic coupler has the potential to noninvasively detect changes in the elasticity of the supraspinatus muscle belly and tendon that accompany varying levels of muscle contraction in clinical practice. Copyright © 2015 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.

  17. Materials fatigue initiates eccentric contraction-induced injury in rat soleus muscle.

    PubMed Central

    Warren, G L; Hayes, D A; Lowe, D A; Prior, B M; Armstrong, R B

    1993-01-01

    1. The initiation of exercise-induced muscle injury is thought to be the result of high tensile stresses produced in the muscle during eccentric contractions. Materials science theory suggests that high tensile stresses could initiate the injury during the first eccentric contraction (normal stress theory) or after multiple eccentric contractions (materials fatigue). It was the objective of this study to investigate the two possibilities. 2. Rat soleus muscles (n = 66; 11 protocols with 6 muscles per protocol) were isolated, placed in an oxygenated Krebs-Ringer buffer at 37 degrees C, and baseline measurements were made. The muscle then performed an injury protocol which consisted of between zero and ten eccentric contractions (muscle starting length = 0.90 soleus muscle length, L0; length change = 0.25 L0; velocity = 1.5 L0/s; peak force = 180% maximal isometric tetanic tension (P0); time between contractions = 4 min; total duration of the injury protocol = 40 min). At the end of the injury protocol, the muscle was incubated in buffer for 1 h; every 15 min, an isometric twitch and tetanus were performed and lactate dehydrogenase (LDH) release was measured. Total muscle [Ca2+] was measured at the end of the incubation. 3. Change-point regression analysis indicates that at 0 min into the incubation, declines in P0, maximal rate of tension development (+dP/dt), maximal rate of relaxation (-dP/dt), and muscle stiffness (dP/dx) became significantly greater after eight eccentric contractions (p < or = 0.05). No relation was found between the number of eccentric contractions performed and the LDH activity at 0 min into the incubation, although after 60 min of incubation, LDH activity in the buffer was linearly related to eccentric contraction number (p = 0.01). There was no relationship between total muscle [Ca2+] and eccentric contraction number. These findings support the materials fatigue hypothesis of exercise-induced muscle injury. PMID:8229814

  18. Pain intensity and abdominal muscle activation during walking in patients with low back pain: The STROBE study.

    PubMed

    Kim, Si-Hyun; Park, Kyue-Nam; Kwon, Oh-Yun

    2017-10-01

    Nonspecific low back pain (LBP) is a common musculoskeletal problem that is intensified during physical activity. Patients with LBP have been reported to change their abdominal muscle activity during walking; however, the effects of pain intensity, disability level, and fear-avoidance belief on this relationship have not been evaluated. Thus, we compared abdominal muscle activity in patients with LBP and asymptomatic controls, and assessed the impact of pain intensity, disability level, and fear-avoidance belief.Thirty patients with LBP divided into groups reporting low (LLBP) and high-pain intensity low back pain (HLBP), and 15 participants without LBP were recruited. LBP patients' self-reported pain intensity, disability, and fear-avoidance belief were recorded. To examine abdominal muscle activity (rectus abdominis [RA], internal [IO], and external oblique [EO] muscles) during walking, all subjects walked at a self-selected speed. Abdominal muscle activity (RA, IO, and EO) was compared among groups (LLBP, HLBP, and controls) in different phases of walking (double support vs swing). Relationships between abdominal muscle activity and clinical measures (pain intensity, disability, fear-avoidance belief) were analyzed using partial correlation analysis.Right IO muscle activity during walking was significantly decreased in LLBP and HLBP compared with controls in certain walking phase. Partial correlation coefficients showed significant correlations between fear-avoidance belief and right EO activity (r = .377, P < .05) and between disability index and left IO activity (r = .377, P < .05) in patients with LBP. No significant difference was found in abdominal muscle activity in walking between patients with LLBP and HLBP (P > .05).This study demonstrated decreased IO muscle activity during certain walking phases in LLBP and HLBP compared with asymptomatic participants. Although altered IO muscle activity during walking was observed in patients with

  19. The effect of different acute muscle contraction regimens on the expression of muscle proteolytic signaling proteins and genes.

    PubMed

    Ato, Satoru; Makanae, Yuhei; Kido, Kohei; Sase, Kohei; Yoshii, Naomi; Fujita, Satoshi

    2017-08-01

    Previous studies have reported that different modes of muscle contraction (i.e., eccentric or concentric contraction) with similar contraction times can affect muscle proteolytic responses. However, the effect of different contraction modes on muscle proteolytic response under the same force-time integral (FTI: contraction force × time) has not been investigated. The purpose of this study was to investigate the effect of different contraction modes, with the same FTI, on acute proteolytic signaling responses. Eleven-week-old male Sprague-Dawley rats were randomly assigned to eccentric (EC), concentric (CC), or isometric contraction (IC) groups. Different modes of muscle contraction were performed on the right gastrocnemius muscle using electrical stimulation, with the left muscle acting as a control. In order to apply an equivalent FTI, the number of stimulation sets was modified between the groups. Muscle samples were taken immediately and three hours after exercise. Phosphorylation of FoxO3a at Ser253 was significantly increased immediately after exercise compared to controls irrespective of contraction mode. The mRNA levels of the ubiquitin ligases, MuRF1, and MAFbx mRNA were unchanged by contraction mode or time. Phosphorylation of ULK1 at Ser317 (positive regulatory site) and Ser757 (negative regulatory site) was significantly increased compared to controls, immediately or 3 h after exercise, in all contraction modes. The autophagy markers (LC3B-II/I ratio and p62 expression) were unchanged, regardless of contraction mode. These data suggest that differences in contraction mode during resistance exercise with a constant FTI, are not factors in regulating proteolytic signaling in the early phase of skeletal muscle contraction. © 2017 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

  20. Physiological response to submaximal isometric contractions of the paravertebral muscles

    NASA Technical Reports Server (NTRS)

    Jensen, B. R.; Jorgensen, K.; Hargens, A. R.; Nielsen, P. K.; Nicolaisen, T.

    1999-01-01

    STUDY DESIGN: Brief (30-second) isometric trunk extensions at 5%, 20%, 40%, 60%, and 80% of maximal voluntary contraction (MVC) and 3 minutes of prolonged trunk extension (20% MVC) in erect position were studied in nine healthy male subjects. OBJECTIVES: To investigate the intercorrelation between intramuscular pressure and tissue oxygenation of the paravertebral muscles during submaximal isometric contractions and further, to evaluate paravertebral electromyogram and intramuscular pressure as indicators of force development. SUMMARY OF BACKGROUND DATA: Local physiologic responses to muscle contraction are incompletely understood. METHODS: Relative oxygenation was monitored with noninvasive near-infrared spectroscopy, intramuscular pressure was measured with a transducer-tipped catheter, and surface electromyogram was monitored at three recording sites. RESULTS: The root mean square amplitudes of the paravertebral electromyogram (L4, left and right; T12, right) and intramuscular pressure measured in the lumbar multifidus muscle at L4 increased with greater force development in a curvilinear manner. A significant decrease in the oxygenation of the lumbar paravertebral muscle in response to muscle contraction was found at an initial contraction level of 20% MVC. This corresponded to a paravertebral intramuscular pressure of 30-40 mm Hg. However, during prolonged trunk extension, no further decrease in tissue oxygenation was found compared with the tissue oxygenation level at the end of the brief contractions, indicating that homeostatic adjustments (mean blood pressure and heart rate) over time were sufficient to maintain paravertebral muscle oxygen levels. CONCLUSION: At a threshold intramuscular pressure of 30-40 mm Hg during muscle contraction, oxygenation in the paravertebral muscles is significantly reduced. The effect of further increase in intramuscular pressure on tissue oxygenation over time may be compensated for by an increase in blood pressure and heart

  1. Cisapride stimulates contraction of idiopathic megacolonic smooth muscle in cats.

    PubMed

    Hasler, A H; Washabau, R J

    1997-01-01

    We have previously shown that cisapride, a substituted piperidinyl benzamide, stimulates contraction of healthy feline colonic smooth muscle. The purpose of the present investigation was to determine the effect of cisapride on feline idiopathic megacolonic smooth muscle function. Longitudinal smooth muscle strips from ascending and descending colon were obtained from cats with idiopathic megacolon, suspended in a 1.5 mM Ca(2+)-HEPES buffer solution (37 degrees C, 100% O2, pH 7.4), attached to isometric force transducers, and stretched to optimal muscle length (Lo). Control responses were obtained at each muscle site with acetylcholine (10(-8) to 10(-4) M), substance P (10(-11) to 10(-7) M), or potassium chloride (10 to 80 mM). Muscles were then stimulated with cumulative (10(-9) to 10(-6) M) doses of cisapride in the absence or presence of tetrodotoxin (10(-6) M) and atropine (10(-6) M), or in a 0 calcium HEPES buffer solution. In cats with idiopathic megacolon, cisapride stimulated contractions of longitudinal smooth muscle from both the ascending and the descending colon. Cisapride-induced contractions were similar in magnitude to those induced by substance P and acetylcholine in the ascending colon, but were less than those observed in the descending colon. Cisapride-induced contractions in megacolonic smooth muscle were only partially inhibited by tetrodotoxin and atropine, but were virtually abolished by removal of extracellular calcium. We concluded that cisapride-induced contractions of feline megacolonic smooth muscle are largely smooth muscle mediated and dependent on influx of extracellular calcium. Cisapride-induced contractions in megacolonic smooth muscle are only partially dependent on enteric cholinergic nerves. Thus, cisapride may be useful in the treatment of cats with idiopathic megacolon.

  2. Skeletal muscle ceramide species in men with abdominal obesity.

    PubMed

    de la Maza, M P; Rodriguez, J M; Hirsch, S; Leiva, L; Barrera, G; Bunout, D

    2015-04-01

    Obesity is a risk factor for diabetes and its consequences, including accelerated ageing and mortality. The underlying factor could be accumulation of certain lipid moieties, such as ceramides (CER) and diacylgycerol (DAG) within muscle tissue, which are known to promote insulin resistance (IR), induce inflammation and oxidative injury, ultimately altering muscle function. First, to study the relationship between body composition and age (independent variables) with skeletal muscle accumulation of lipid species, oxidative injury and strength. Second, to analyze the relationship between muscle tissue metabolites and insulin resistance, inflammation and lymphocyte telomere length, the latter as an indicator of ageing. The sample included 56 healthy sedentary males, scheduled for inguinal hernia surgery, aged 27 to 80 y. Each individual was subject to anthropometric measurements, body composition assessment through radiologic densitometry (DEXA), measurement of handgrip and quadriceps strength, serum biochemical parameters (lipoproteins, creatinine, high sensitivity C reactive protein [hsCRP], fasting and post glucose insulin and glucose concentrations for calculation of IR through the Matsuda and HOMA-IR indexes), and extraction of peripheral leukocytes for measurement of telomere length. During the surgical procedure, a sample of muscle tissue was obtained (anterior abdominal oblique) in order to measure CER and DAG (and sub species according to chain length and saturation) by mass spectrometry, 4 hydroxy-2-nonenal adducts (4-HNE) using electron microscopy immunohistochemistry, and carboxymethyl-lisine (CML) by immunohistochemistry, the latter as indicators of oxidative stress (OS). Body mass index (BMI) of twenty six individuals was > 25 k/m2, while BMI of 7 was > 30 k/m2. Overweight/obese individuals, did not exhibit differences in skeletal muscle lipid metabolites, however total CER and specific long chain CER sub-species (20 and 22 carbon) increased

  3. A magnetic resonance imaging investigation of the transversus abdominis muscle during drawing-in of the abdominal wall in elite Australian Football League players with and without low back pain.

    PubMed

    Hides, Julie A; Boughen, Carly L; Stanton, Warren R; Strudwick, Mark W; Wilson, Stephen J

    2010-01-01

    Single-blinded quasi-experimental study. To investigate the ability of elite football players with and without low back pain (LBP) to voluntarily draw-in the abdominal wall. While there has been considerable debate regarding the contribution of the transversus abdominis (TrA) muscle to control the lumbar spine and pelvis, there is evidence that retraining motor control of the deep trunk muscles is commensurate with decreases in LBP. Magnetic resonance imaging (MRI) has been used to assess the TrA muscle during the draw-in maneuver, with the contraction of the TrA muscle reducing the circumference of the trunk. Impairments in performance of the draw-in maneuver have been shown in people with LBP. Forty-three elite players from a team in the Australian Football League were allocated to 3 groups: those with "no LBP," "a history of LBP but no current LBP," or "current LBP." MRI was used to image the cross-sectional area (CSA) of the trunk at the level of the L3-4 disc at the start and end of the draw-in maneuver. There was a significant decrease in the CSA of the trunk with the performance of the draw-in maneuver (P<.001). Subjects in the "no LBP" group were better able to "draw-in" the abdominal wall than subjects with current LBP (P = .015). This study provides evidence of an altered ability to draw-in the abdominal wall in footballers with current LBP. Retraining contraction of the TrA muscle may constitute one part of an exercise-therapy approach for athletes with current LBP.

  4. Muscle fibre recruitment can respond to the mechanics of the muscle contraction.

    PubMed

    Wakeling, James M; Uehli, Katrin; Rozitis, Antra I

    2006-08-22

    This study investigates the motor unit recruitment patterns between and within muscles of the triceps surae during cycling on a stationary ergometer at a range of pedal speeds and resistances. Muscle activity was measured from the soleus (SOL), medial gastrocnemius (MG) and lateral gastrocnemius (LG) using surface electromyography (EMG) and quantified using wavelet and principal component analysis. Muscle fascicle strain rates were quantified using ultrasonography, and the muscle-tendon unit lengths were calculated from the segmental kinematics. The EMG intensities showed that the body uses the SOL relatively more for the higher-force, lower-velocity contractions than the MG and LG. The EMG spectra showed a shift to higher frequencies at faster muscle fascicle strain rates for MG: these shifts were independent of the level of muscle activity, the locomotor load and the muscle fascicle strain. These results indicated that a selective recruitment of the faster motor units occurred within the MG muscle in response to the increasing muscle fascicle strain rates. This preferential recruitment of the faster fibres for the faster tasks indicates that in some circumstances motor unit recruitment during locomotion can match the contractile properties of the muscle fibres to the mechanical demands of the contraction.

  5. Changes in oxygen consumption of human muscle and tendon following repeat muscle contractions.

    PubMed

    Kubo, Keitaro; Ikebukuro, Toshihiro; Tsunoda, Naoya; Kanehisa, Hiroaki

    2008-11-01

    The purpose of this study was to investigate changes in the oxygen consumption (VO(2)) of muscle and tendon following repeat muscle contractions. During endurance tests (50 repetitions at 70% of the maximum voluntary contraction with 5-s contractions and 5-s rest) and the recovery period (0-10 min), we measured the blood volume and oxygen saturation (StO(2)) of the medial gastrocnemius muscle and Achilles tendon using near infrared spectroscopy and red laser light. Nine male subjects performed the endurance tests three times on separate days (tests-1, 2, and 3). Before and after (test-1: immediately after, test-2: at the 5-min recovery point, test-3: at the 10-min recovery point) the endurance tests, the rate of StO(2) during 8-min period of arterial occlusion was measured to estimate the VO(2) of muscle and tendon. In test-3, after the end of exercise, the THb and StO(2) of the Achilles tendon increased gradually, and these values were higher than the pre-exercise levels until the end of the recovery period. The VO(2) of tendon as well as muscle increased significantly after the repeat muscle contractions. Furthermore, the VO(2) of tendon returned to the pre-exercise level at the 10-min point of recovery, although that of muscle was significantly higher compared to the pre-exercise level until the end of the recovery period. These results indicate that the difference between oxygen supply and consumption within tendon was greater after compared to before exercise.

  6. Muscle contraction: A mechanical perspective.

    PubMed

    Marcucci, L; Truskinovsky, L

    2010-08-01

    In this paper we present a purely mechanical analog of the conventional chemo-mechanical modeling of muscle contraction. We abandon the description of kinetics of the power stroke in terms of jump processes and instead resolve the continuous stochastic evolution on an appropriate energy landscape. In general physical terms, we replace hard spin chemical variables by soft spin variables representing mechanical snap-springs. This allows us to treat the case of small and even disappearing barriers and, more importantly, to incorporate the mechanical representation of the power stroke into the theory of Brownian ratchets. The model provides the simplest non-chemical description for the main stages of the biochemical Lymn-Taylor cycle and may be used as a basis for the artificial micro-mechanical reproduction of the muscle contraction mechanism.

  7. Optical NIR monitoring of skeletal muscle contraction

    NASA Astrophysics Data System (ADS)

    Lago, Paolo; Gelmetti, Andrea; Pavesi, Roberta; Zambarbieri, Daniela

    1996-12-01

    NIR spectroscopy allows monitoring of muscle oxygenation and perfusion during contraction. The knowledge of modifications of blood characteristics in body tissues has relevant clinical interest. A compact and reliable device, which makes use of two laser diodes at 750 and 810 nm coupled with the skin surface through optical fibers, was tested. NIR and surface EMG signals during isometric contractions both in normal and ischaemic conditions were analyzed. A set of parameters from the 750/810 spectroscopic curve was analyzed. Two different categories depending on the recovery rate from maximal voluntary contraction to basal oxygenation conditions were found. This behavior can give information about metabolic modifications during muscle fatigue. Interesting results in testing isokinetic rehabilitation training were also obtained.

  8. Control of abdominal muscles by brain stem respiratory neurons in the cat

    NASA Technical Reports Server (NTRS)

    Miller, Alan D.; Ezure, Kazuhisa; Suzuki, Ichiro

    1985-01-01

    The nature of the control of abdominal muscles by the brain stem respiratory neurons was investigated in decerebrate unanesthetized cats. First, it was determined which of the brain stem respiratory neurons project to the lumbar cord (from which the abdominal muscles receive part of their innervation), by stimulating the neurons monopolarly. In a second part of the study, it was determined if lumbar-projecting respiratory neurons make monosynaptic connections with abdominal motoneurons; in these experiments, discriminate spontaneous spikes of antidromically acivated expiratory (E) neurons were used to trigger activity from both L1 and L2 nerves. A large projection was observed from E neurons in the caudal ventral respiratory group to the contralateral upper lumber cord. However, cross-correlation experiments found only two (out of 47 neuron pairs tested) strong monosynaptic connections between brain stem neurons and abdominal motoneurons.

  9. Effects of non-paretic arm exercises using a tubing band on abdominal muscle activity in stroke patients.

    PubMed

    Lee, Dong-Kyu; Kang, Min-Hyeok; Kim, Ji-Won; Kim, Yang-Gon; Park, Ji-Hyuk; Oh, Jae-Seop

    2013-01-01

    Abdominal strengthening exercises are important for stroke patients; however, there is a lack of research on therapeutic exercises for increasing abdominal muscle activity in stroke patients. We investigated the effects of non-paretic arm exercises using a tubing band on abdominal muscle activity in stroke patients. In total, 18 hemiplegic subjects (13 males, 5 females) were recruited. All subjects performed non-paretic arm exercises involving three different shoulder movements (extension, flexion, and horizontal abduction) using an elastic tubing band. Surface electromyography (EMG) signals were recorded from the rectus abdominis (RA), external oblique (EO), and internal oblique (IO) muscles bilaterally during non-paretic arm exercises. EMG activities of abdominal muscles during non-paretic arm extension and horizontal abduction were increased significantly versus shoulder flexion when subjects performed the arm exercise in a seated position. Muscle activity of the EO was significantly greater in the paretic than the non-paretic side during non-paretic arm extension and horizontal abduction. We suggest that non-paretic arm extension and horizontal abduction exercises using an elastic tubing band may be effective in increasing abdominal muscle activity.

  10. Clinical evaluation of extraperitoneal colostomy without damaging the muscle layer of the abdominal wall.

    PubMed

    Dong, L-R; Zhu, Y-M; Xu, Q; Cao, C-X; Zhang, B-Z

    2012-01-01

    This study investigated whether extraperitoneal colostomy without damaging the muscle layer of the abdominal wall is an improved surgical procedure compared with conventional sigmoid colostomy in patients undergoing abdominoperineal resection. Patients with rectal cancer undergoing abdominoperineal resection were selected and randomly divided into two groups: the study group received extraperitoneal colostomy without damaging the muscle layer of the abdominal wall and the control group received conventional colostomy. Clinical data from both groups were analysed. A total of 128 patients were included: 66 received extraperitoneal colostomy without damaging the muscle layer of the abdominal wall and 62 received conventional colostomy. Significant differences between the two groups were found in relation to colostomy operating time, defaecation sensation, bowel control and overall stoma-related complications. Duration of postoperative hospital stay was also significantly different between the study groups. Extraperitoneal colostomy without damaging the muscle layer of the abdominal wall was found to be an improved procedure compared with conventional sigmoid colostomy in abdominoperineal resection, and may reduce colostomy-related complications, shorten operating time and postoperative hospital stay, and potentially improve patients' quality of life.

  11. Limb congestion enhances the synchronization of sympathetic outflow with muscle contraction

    NASA Technical Reports Server (NTRS)

    Mostoufi-Moab, S.; Herr, M. D.; Silber, D. H.; Gray, K. S.; Leuenberger, U. A.; Sinoway, L. I.

    2000-01-01

    In this report, we examined if the synchronization of muscle sympathetic nerve activity (MSNA) with muscle contraction is enhanced by limb congestion. To explore this relationship, we applied signal-averaging techniques to the MSNA signal obtained during short bouts of forearm contraction (2-s contraction/3-s rest cycle) at 40% maximal voluntary contraction for 5 min. We performed this analysis before and after forearm venous congestion; an intervention that augments the autonomic response to sustained static muscle contractions via a local effect on muscle afferents. There was an increased percentage of the MSNA noted during second 2 of the 5-s contraction/rest cycles. The percentage of total MSNA seen during this particular second increased from minute 1 to 5 of contraction and was increased further by limb congestion (control minute 1 = 25.6 +/- 2.0%, minute 5 = 32.8 +/- 2.2%; limb congestion minute 1 = 29.3 +/- 2.1%, minute 5 = 37.8 +/- 3.9%; exercise main effect <0.005; limb congestion main effect P = 0.054). These changes in the distribution of signal-averaged MSNA were seen despite the fact that the mean number of sympathetic discharges did not increase over baseline. We conclude that synchronization of contraction and MSNA is seen during short repetitive bouts of handgrip. The sensitizing effect of contraction time and limb congestion are apparently due to feedback from muscle afferents within the exercising muscle.

  12. Forearm muscle oxygenation decreases with low levels of voluntary contraction

    NASA Technical Reports Server (NTRS)

    Murthy, G.; Kahan, N. J.; Hargens, A. R.; Rempel, D. M.

    1997-01-01

    The purpose of our investigation was to determine if the near infrared spectroscopy technique was sensitive to changes in tissue oxygenation at low levels of isometric contraction in the extensor carpi radialis brevis muscle. Nine subjects were seated with the right arm abducted to 45 degrees, elbow flexed to 85 degrees, forearm pronated 45 degrees, and wrist and forearm supported on an armrest throughout the protocol. Altered tissue oxygenation was measured noninvasively with near infrared spectroscopy. The near infrared spectroscopy probe was placed over the extensor carpi radialis brevis of the subject's right forearm and secured with an elastic wrap. After 1 minute of baseline measurements taken with the muscle relaxed, four different loads were applied just proximal to the metacarpophalangeal joint such that the subjects isometrically contracted the extensor carpi radialis brevis at 5, 10, 15, and 50% of the maximum voluntary contraction for 1 minute each. A 3-minute recovery period followed each level of contraction. At the end of the protocol, with the probe still in place, a value for ischemic tissue oxygenation was obtained for each subject. This value was considered the physiological zero and hence 0% tissue oxygenation. Mean tissue oxygenation (+/-SE) decreased from resting baseline (100% tissue oxygenation) to 89 +/- 4, 81 +/- 8, 78 +/- 8, and 47 +/- 8% at 5, 10, 15, and 50% of the maximum voluntary contraction, respectively. Tissue oxygenation levels at 10, 15, and 50% of the maximum voluntary contraction were significantly lower (p < 0.05) than the baseline value. Our results indicate that tissue oxygenation significantly decreases during brief, low levels of static muscle contraction and that near infrared spectroscopy is a sensitive technique for detecting deoxygenation noninvasively at low levels of forearm muscle contraction. Our findings have important implications in occupational medicine because oxygen depletion induced by low levels of muscle

  13. [Forskolin inhibits spontaneous contraction of gastric antral smooth muscle in rats].

    PubMed

    Jiang, Jing-Zhi; Sun, Qian; Xu, Dong-Yuan; Zhang, Mo-Han; Piao, Li-Hua; Cai, Ying-Lan; Jin, Zheng

    2013-04-25

    The aim of the present study was to investigate the effects of cyclic adenosine monophosphate (cAMP) on rat gastric antral circular smooth muscle function. Forskolin, a direct activator of adenylyl cyclase (AC), was used to observe the influences of cAMP. Multi-channel physiological recorder was used to record spontaneous contraction activity of gastric antral circular muscle from Wistar rats. And ELISA method was used to detect the change of cAMP production in perfusate. The results showed that forskolin concentration-dependently suppressed the amplitude and frequency of the spontaneous contraction of the gastric antral muscle, and lowered the baseline of contraction movement significantly. Forskolin concentration-dependently increased the production of cAMP in the perfusate, which showed a significant negative correlation with the contraction amplitude of gastric antral ring muscle. The inhibitory effect of forskolin on spontaneous contraction activity of rat gastric antral circular muscle could be blocked by cAMP-dependent protein kinase (PKA) inhibitor H-89. These results suggest forskolin increases cAMP production and then activates PKA pathway, resulting in the inhibition of the spontaneous contraction activity of rat gastric antral circular smooth muscle.

  14. Effects of hypothyroidism on the skeletal muscle blood flow response to contractions.

    PubMed

    Bausch, L; McAllister, R M

    2003-04-01

    Hypothyroidism is associated with impaired blood flow to skeletal muscle under whole body exercise conditions. It is unclear whether poor cardiac and/or vascular function account for blunted muscle blood flow. Our experiment isolated a small group of hindlimb muscles and simulated exercise via tetanic contractions. We hypothesized that muscle blood flow would be attenuated in hypothyroid rats (HYPO) compared with euthyroid rats (EUT). Rats were made hypothyroid by mixing propylthiouracil in their drinking water (2.35 x 10-3 mol/l). Treatment efficacy was evidenced by lower serum T3 concentrations and resting heart rates in HYPO (both P<0.05). In the experimental preparation, isometric contractions of the lower right hindlimb muscles at a rate of 30 tetani/min were induced via sciatic nerve stimulation. Regional blood flows were determined by the radiolabelled microsphere method at three time points: rest, 2 min of contractions and 10 min of contractions. Muscle blood flow generally increased from rest ( approximately 5-10 ml/min per 100 g) through contractions for both groups. Further, blood flow during contractions did not differ between groups for any muscle (eg. red section of gastrocnemius muscle; EUT, 59.9 +/- 14.1; HYPO, 61.1 +/- 15.0; NS between groups). These findings indicate that hypothyroidism does not significantly impair skeletal muscle blood flow when only a small muscle mass is contracting. Our findings suggest that impaired blood flow under whole body exercise is accounted for by inadequate cardiac function rather than abnormal vascular function.

  15. Influence of inward pressure of the transducer on lateral abdominal muscle thickness during ultrasound imaging.

    PubMed

    Ishida, Hiroshi; Watanabe, Sususmu

    2012-09-01

    Controlled laboratory study, technical note. The purpose of this study was to quantify changes in the thickness of the transversus abdominis, internal oblique, and external oblique muscles induced by different inward pressures of the transducer during ultrasound imaging (USI). USI of the lateral abdominal muscles is increasingly used in managing musculoskeletal dysfunction. However, to the best of our knowledge, no study has evaluated the influence of different inward pressures of the transducer on the lateral abdominal muscle thickness during USI. Thirty healthy male volunteers participated in this study. The thickness of the transversus abdominis, internal oblique, and external oblique muscles was measured with USI by the same rater in 4 conditions of inward pressures of 0.5, 1.0, 2.0, and 4.0 N. Intraclass correlation coefficients (ICC1,1), with 95% confidence intervals, were calculated, and a repeated-measures analysis of variance was used to assess the influence of inward pressure on the thickness of the lateral abdominal muscles. The thickness of the transversus abdominis, internal oblique, and external oblique muscles was significantly different among the 4 conditions (P<.038). The mean difference between the 0.5-N and 4.0-N conditions was greater than the minimal detectable change of the 0.5-N condition in the lateral abdominal muscles. The difference in magnitude produced by the forces under different conditions was meaningful. When using a technique that involves a handheld transducer, the examiner should attempt to maintain consistent inward pressure of the transducer during USI to quantify the thickness of lateral abdominal muscles. J Orthop Sports Phys Ther 2012;42(9):815-818, Epub 19 April 2012. doi:10.2519/jospt.2012.4064.

  16. Ciliary muscle contraction force and trapezius muscle activity during manual tracking of a moving visual target.

    PubMed

    Domkin, Dmitry; Forsman, Mikael; Richter, Hans O

    2016-06-01

    Previous studies have shown an association of visual demands during near work and increased activity of the trapezius muscle. Those studies were conducted under stationary postural conditions with fixed gaze and artificial visual load. The present study investigated the relationship between ciliary muscle contraction force and trapezius muscle activity across individuals during performance of a natural dynamic motor task under free gaze conditions. Participants (N=11) tracked a moving visual target with a digital pen on a computer screen. Tracking performance, eye refraction and trapezius muscle activity were continuously measured. Ciliary muscle contraction force was computed from eye accommodative response. There was a significant Pearson correlation between ciliary muscle contraction force and trapezius muscle activity on the tracking side (0.78, p<0.01) and passive side (0.64, p<0.05). The study supports the hypothesis that high visual demands, leading to an increased ciliary muscle contraction during continuous eye-hand coordination, may increase trapezius muscle tension and thus contribute to the development of musculoskeletal complaints in the neck-shoulder area. Further experimental studies are required to clarify whether the relationship is valid within each individual or may represent a general personal trait, when individuals with higher eye accommodative response tend to have higher trapezius muscle activity. Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. Endogenous Cardiac Troponin T Modulates Ca2+-Mediated Smooth Muscle Contraction

    PubMed Central

    Kajioka, Shunichi; Takahashi-Yanaga, Fumi; Shahab, Nouval; Onimaru, Mitsuho; Matsuda, Miho; Takahashi, Ryosuke; Asano, Haruhiko; Morita, Hiromitsu; Morimoto, Sachio; Yonemitsu, Yoshikazu; Hayashi, Maya; Seki, Narihito; Sasaguri, Toshiuyki; Hirata, Masato; Nakayama, Shinsuke; Naito, Seiji

    2012-01-01

    Mechanisms linked to actin filaments have long been thought to cooperate in smooth muscle contraction, although key molecules were unclear. We show evidence that cardiac troponin T (cTnT) substantially contributes to Ca2+-mediated contraction in a physiological range of cytosolic Ca2+ concentration ([Ca2+]i). cTnT was detected in various smooth muscles of the aorta, trachea, gut and urinary bladder, including in humans. Also, cTnT was distributed along with tropomyosin in smooth muscle cells, suggesting that these proteins are ready to cause smooth muscle contraction. In chemically permeabilised smooth muscle of cTnT+/− mice in which cTnT reduced to ~50%, the Ca2+-force relationship was shifted toward greater [Ca2+]i, indicating a sizeable contribution of cTnT to smooth muscle contraction at [Ca2+]i < 1 μM. Furthermore, addition of supplemental TnI and TnC reconstructed a troponin system to enhance contraction. The results indicated that a Tn/Tn-like system on actin-filaments cooperates together with the thick-filament pathway. PMID:23248744

  18. Functional magnetic stimulation of the abdominal muscles in humans.

    PubMed

    Polkey, M I; Luo, Y; Guleria, R; Hamnegård, C H; Green, M; Moxham, J

    1999-08-01

    Functional magnetic stimulation (FMS) of the thoracic nerve roots to simulate cough has been suggested as a treatment approach in patients unable to voluntarily activate the abdominal muscles. However, factors that could influence the efficacy of FMS in clinical use have not been evaluated. In the present investigation we studied train length, posture, and frequency to determine the optimal stimulation protocol. We also evaluated the use of a valve at the mouth to enhance glottic function and investigated whether lung volume at the time of stimulation would influence the tension generated by the abdominal muscles. Studies were performed using a Magstim rapid stimulator augmented by four booster packs in nine healthy subjects; we measured the change in gastric (DeltaPga(FMS)), esophageal (DeltaPes(FMS)), and mouth pressure and expiratory flow. With our apparatus pressure generation was maximized by having a train length of at least 300 ms and a frequency of 25 Hz. Posture and valve use were not important determinants of DeltaPga(FMS) or DeltaPes(FMS). Lung volume exerted only a minor influence on DeltaPga(FMS), but the ratio DeltaPes(FMS):DeltaPga(FMS) was increased at TLC compared with FRC. Expiratory flow was increased by adopting a seated posture and using an occlusion valve with an opening threshold close to the maximum DeltaPes(FMS) generated by the stimulus train; however, expiratory flow was susceptible to interference from glottic incoordination. Representative results (with train length 600 ms, 25 Hz, and 100% power, seated) were mean DeltaPga(FMS), 166 cm H(2)O; mean DeltaPes(FMS), 108 cm H(2)O; and mean expiratory flow, 311 L/min. We confirm that FMS of the abdominal muscles can generate a substantial positive intra-abdominal and intrathoracic pressure and, consequently, expiratory flow in normal subjects.

  19. In-vivo measurement of muscle tension: dynamic properties of the MC sensor during isometric muscle contraction.

    PubMed

    Đorđević, Srđan; Tomažič, Sašo; Narici, Marco; Pišot, Rado; Meglič, Andrej

    2014-09-25

    Skeletal muscle is the largest tissue structure in our body and plays an essential role for producing motion through integrated action with bones, tendons, ligaments and joints, for stabilizing body position, for generation of heat through cell respiration and for blood glucose disposal. A key function of skeletal muscle is force generation. Non-invasive and selective measurement of muscle contraction force in the field and in clinical settings has always been challenging. The aim of our work has been to develop a sensor that can overcome these difficulties and therefore enable measurement of muscle force during different contraction conditions. In this study, we tested the mechanical properties of a "Muscle Contraction" (MC) sensor during isometric muscle contraction in different length/tension conditions. The MC sensor is attached so that it indents the skin overlying a muscle group and detects varying degrees of tension during muscular contraction. We compared MC sensor readings over the biceps brachii (BB) muscle to dynamometric measurements of force of elbow flexion, together with recordings of surface EMG signal of BB during isometric contractions at 15° and 90° of elbow flexion. Statistical correlation between MC signal and force was very high at 15° (r = 0.976) and 90° (r = 0.966) across the complete time domain. Normalized SD or σN = σ/max(FMC) was used as a measure of linearity of MC signal and elbow flexion force in dynamic conditions. The average was 8.24% for an elbow angle of 90° and 10.01% for an elbow of angle 15°, which indicates high linearity and good dynamic properties of MC sensor signal when compared to elbow flexion force. The next step of testing MC sensor potential will be to measure tension of muscle-tendon complex in conditions when length and tension change simultaneously during human motion.

  20. The use of abdominal muscle training, breathing exercises and abdominal massage to treat paediatric chronic functional constipation.

    PubMed

    Silva, C A G; Motta, M E F A

    2013-05-01

    The effect of muscular training, abdominal massage and diaphragmatic breathing was compared with medical treatment in a prospective randomized trial of patients with chronic functional constipation. Patients aged 4-18 years old with functional constipation according to the Rome III criteria were randomized to physiotherapy or medical treatment. In the physiotherapy group, exercises (isometric training of the abdominal muscles, diaphragmatic breathing exercises and abdominal massage) were employed during 12 40-min sessions twice a week by a trained physiotherapist, with laxatives. Patients in the medication group were only given laxatives. Primary outcome measures were frequency of defaecation and faecal incontinence. The analysis was performed by intention-to-treat. After 6 weeks of treatment, the frequency of bowel movements was higher in the physiotherapy group [5.1 (2.1) days/week] than in the medication group [3.9 (2.0) days/week] (P = 0.01). The frequency of faecal incontinence was no different between the groups [3.6 (1.9) days/week vs 3.0 (2.1) days/week] (P = 0.31). The combined use of isometric training of abdominal muscles, breathing exercises and abdominal massage increased defaecation frequency after 6 weeks but faecal incontinence remained unchanged. Physiotherapy may be a useful treatment for constipation. Colorectal Disease © 2013 The Association of Coloproctology of Great Britain and Ireland.

  1. Contraction coupling efficiency of human first dorsal interosseous muscle.

    PubMed

    Jubrias, Sharon A; Vollestad, Nina K; Gronka, Rod K; Kushmerick, Martin J

    2008-04-01

    During working contractions, chemical energy in the form of ATP is converted to external work. The efficiency of this conversion, called 'contraction coupling efficiency', is calculated by the ratio of work output to energy input from ATP splitting. Experiments on isolated muscles and permeabilized fibres show the efficiency of this conversion has a wide range, 0.2-0.7. We measured the work output in contractions of a single human hand muscle in vivo and of the ATP cost of that work to calculate the contraction coupling efficiency of the muscle. Five subjects performed six bouts of rapid voluntary contractions every 1.5 s for 42 s (28 contractions, each with time to peak force < 150 ms). The bouts encompassed a 7-fold range of workloads. The ATP cost during work was quantified by measuring the extent of chemical changes within the muscle from (31)P magnetic resonance spectra. Contraction coupling efficiency was determined as the slope of paired measurements of work output and ATP cost at the five graded work loads. The results show that 0.68 of the chemical energy available from ATP splitting was converted to external work output. A plausible mechanism to account for this high value is a substantially lower efficiency for mitochondrial ATP synthesis. The method described here can be used to analyse changes in the overall efficiency determined from oxygen consumption during exercise that can occur in disease or with age, and to test the hypothesis that such changes are due to reduced contraction coupling efficiency.

  2. History-dependence of muscle slack length following contraction and stretch in the human vastus lateralis.

    PubMed

    Stubbs, Peter W; Walsh, Lee D; D'Souza, Arkiev; Héroux, Martin E; Bolsterlee, Bart; Gandevia, Simon C; Herbert, Robert D

    2018-06-01

    In reduced muscle preparations, the slack length and passive stiffness of muscle fibres have been shown to be influenced by previous muscle contraction or stretch. In human muscles, such behaviours have been inferred from measures of muscle force, joint stiffness and reflex magnitudes and latencies. Using ultrasound imaging, we directly observed that isometric contraction of the vastus lateralis muscle at short lengths reduces the slack lengths of the muscle-tendon unit and muscle fascicles. The effect is apparent 60 s after the contraction. These observations imply that muscle contraction at short lengths causes the formation of bonds which reduce the effective length of structures that generate passive tension in muscles. In reduced muscle preparations, stretch and muscle contraction change the properties of relaxed muscle fibres. In humans, effects of stretch and contraction on properties of relaxed muscles have been inferred from measurements of time taken to develop force, joint stiffness and reflex latencies. The current study used ultrasound imaging to directly observe the effects of stretch and contraction on muscle-tendon slack length and fascicle slack length of the human vastus lateralis muscle in vivo. The muscle was conditioned by (a) strong isometric contractions at long muscle-tendon lengths, (b) strong isometric contractions at short muscle-tendon lengths, (c) weak isometric contractions at long muscle-tendon lengths and (d) slow stretches. One minute after conditioning, ultrasound images were acquired from the relaxed muscle as it was slowly lengthened through its physiological range. The ultrasound image sequences were used to identify muscle-tendon slack angles and fascicle slack lengths. Contraction at short muscle-tendon lengths caused a mean 13.5 degree (95% CI 11.8-15.0 degree) shift in the muscle-tendon slack angle towards shorter muscle-tendon lengths, and a mean 5 mm (95% CI 2-8 mm) reduction in fascicle slack length, compared to the

  3. Work Done by Titin Protein Folding Assists Muscle Contraction.

    PubMed

    Rivas-Pardo, Jaime Andrés; Eckels, Edward C; Popa, Ionel; Kosuri, Pallav; Linke, Wolfgang A; Fernández, Julio M

    2016-02-16

    Current theories of muscle contraction propose that the power stroke of a myosin motor is the sole source of mechanical energy driving the sliding filaments of a contracting muscle. These models exclude titin, the largest protein in the human body, which determines the passive elasticity of muscles. Here, we show that stepwise unfolding/folding of titin immunoglobulin (Ig) domains occurs in the elastic I band region of intact myofibrils at physiological sarcomere lengths and forces of 6-8 pN. We use single-molecule techniques to demonstrate that unfolded titin Ig domains undergo a spontaneous stepwise folding contraction at forces below 10 pN, delivering up to 105 zJ of additional contractile energy, which is larger than the mechanical energy delivered by the power stroke of a myosin motor. Thus, it appears inescapable that folding of titin Ig domains is an important, but as yet unrecognized, contributor to the force generated by a contracting muscle. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  4. Characteristics of power spectrum density function of EMG during muscle contraction below 30%MVC.

    PubMed

    Roman-Liu, Danuta; Konarska, Maria

    2009-10-01

    The aim of the study was to quantify changes in PSDF frequency bands of the EMG signal and EMG parameters such as MF, MPF and zero crossing, with an increase in the level of muscle contractions in the range from 0.5% to 30% RMS(max) and to determine the frequency bands with the lowest dependency on RMS level so that this could be used in investigating muscle fatigue. Sixteen men, aged from 23 to 33 years old (mean 26.1), who participated in the study performed two force exertion tests. Fragments of EMG which corresponded to the levels of muscle contraction of 0.5%, 1%, 2.5%, 5%, 10%, 15%, 20%, 25%, 30% RMS(max) registered from left and right trapezius pars descendents (TP) and left and right extensor digitorum superficialis (ED) muscles were selected for analysis. The analysis included changes in standard parameters of the EMG signal and changes in PSDF frequency bands, which occurred across muscle contraction levels. To analyze changes in PSDF across the level of muscle contraction, the spectrum was divided into six frequency bandwidths. The analysis of parameters focused on the differences in those parameters between the analyzed muscles, at different levels of muscle contraction. The study revealed that, at muscle contraction levels below 5% RMSmax, contraction level influences standard parameters of the EMG signal and that at such levels of muscle contraction every change in muscle contraction level (recruitment of additional MUs) is reflected in PSDF. The frequency band with the lowest dependency on contraction level was 76-140 Hz for which in both muscles no contraction level effect was detected for contraction levels above 5% RMS(max). The reproducibility of the results was very high, since the observations in of the left and right muscles were almost equal. The other factor, which strongly influences PSDF of the EMG signal, is probably the examined muscle structure (muscle morphology, size, function, subcutaneous layer, cross talk). It seems that low

  5. Body Mass Normalization for Lateral Abdominal Muscle Thickness Measurements in Adolescent Athletes.

    PubMed

    Linek, Pawel

    2017-09-01

    To determine the value of allometric parameters for ultrasound measurements of the oblique external (OE), oblique internal (OI), and transversus abdominis (TrA) muscles in adolescent athletes. The allometric parameter is the slope of the linear regression line between the log-transformed body mass and log-transformed muscle size measurement. The study included 114 male adolescent football players between the ages of 10 and 19 years. All individuals with no surgical procedures performed on the trunk area and who had played a sport for at least 2 years were included. A real-time B-mode ultrasound scanner with a linear array transducer was used to obtain images of the lateral abdominal muscles from both sides of the body. A stabilometric platform was used to assess the body mass value. The correlations between body mass and the OE, OI, and TrA muscle thicknesses were r = 0.73, r = 0.79, and r = 0.64, respectively (in all cases, P < .0001). The allometric parameters were 0.77 for the OE, 0.67 for the OI, and 0.61 for the TrA. Using these parameters, no significant correlations were found between body mass and the allometric-scaled thickness of the lateral abdominal muscles. Significant positive correlations exist between body mass and lateral abdominal muscle thickness in adolescent athletes. Therefore, it is reasonable to advise that the values of the allometric parameters for the OE, OI, and TrA muscles obtained in this study should be used, and the allometric-scaled thicknesses of those muscles should be analyzed in future research on adolescent athletes. © 2017 by the American Institute of Ultrasound in Medicine.

  6. Aerobic metabolism on muscle contraction in porcine iris sphincter.

    PubMed

    Kanda, Hidenori; Kaneda, Takeharu; Kato, Asami; Yogo, Takuya; Harada, Yasuji; Hara, Yasusi; Urakawa, Norimoto; Shimizu, Kazumasa

    2016-12-01

    Eyes are supplied O 2 through the cornea and vessels of the retina and iris, which are tissues characterized by aerobic metabolism. Meanwhile, there are no reports on the association between iris sphincter contraction and aerobic metabolism. In this paper, we studied the aforementioned association. Eyes from adult pigs of either sex were obtained from a local abattoir. A muscle strip was connected to a transducer to isometrically record the tension. O 2 consumption was measured using a Clark-type polarograph connected to a biological oxygen monitor. Creatine phosphate (PCr) and adenosine triphosphate (ATP) contents were measured in the muscle strips by high-performance liquid chromatography (HPLC). Iris sphincter muscles were measured in resting, contractile or hypoxic phases. Contraction was induced by hyperosmotic 65 mM KCl (H-65K + ) or carbachol (CCh), and hypoxia was induced by aeration with N 2 instead of O 2 or by addition of sodium cyanide (NaCN). H-65K + - and CCh-induced muscle contraction, involved increasing O 2 consumption. Hypoxia and NaCN significantly decreased H-65K + - and CCh-induced muscle contraction and/or O 2 consumption and PCr contents. Our results suggest that the contractile behavior in porcine iris sphincter highly depends on mitogen oxidative metabolism.

  7. Electrically evoked local muscle contractions cause an increase in hippocampal BDNF.

    PubMed

    Maekawa, Takahiro; Ogasawara, Riki; Tsutaki, Arata; Lee, Kihyuk; Nakada, Satoshi; Nakazato, Koichi; Ishii, Naokata

    2018-05-01

    High-intensity exercise has recently been shown to cause an increase in brain-derived neurotropic factor (BDNF) in the hippocampus. Some studies have suggested that myokines secreted from contracting skeletal muscle, such as irisin (one of the truncated form of fibronectin type III domain-containing protein 5 (FNDC5)), play important roles in this process. Thus, we hypothesized that locally evoked muscle contractions may cause an increase of BDNF in the hippocampus through some afferent mechanisms. Under anesthesia, Sprague-Dawley rats were fixed on a custom-made dynamometer and their triceps surae muscles were made to maximally contract via delivery of electric stimulations of the sciatic nerve (100 Hz with 1-ms pulse and 3-s duration). Following 50 repeated maximal isometric contractions, the protein expressions of BDNF and activation of its receptor in the hippocampus significantly increased compared with the sham-operated control rats. However, the expression of both BDNF and FNDC5 within stimulated muscles did not significantly increase, nor did their serum concentrations change. These results indicate that local muscular contractions under unconsciousness can induce BDNF expression in the hippocampus. This effect may be mediated by peripheral reception of muscle contraction, but not by systemic factors.

  8. Reflex muscle contraction in anterior shoulder instability.

    PubMed

    Wallace, D A; Beard, D J; Gill, R H; Eng, B; Carr, A J

    1997-01-01

    Reduced proprioception may contribute to recurrent anterior shoulder instability. Twelve patients with unilateral shoulder instability were investigated for evidence of deficient proprioception with an activated pneumatic cylinder and surface electromyography electrodes; the contralateral normal shoulder was used as a control. The latency between onset of movement and the detection of muscle contraction was used as an index of proprioception. No significant difference in muscle contraction latency was detected between the stable and unstable shoulders, suggesting that there was no significant defect in muscular reflex activity. This study does not support the use proprioception-enhancing physiotherapy in the treatment of posttraumatic anterior shoulder instability.

  9. Analysis of Muscle Contraction on Pottery Manufacturing Process Using Electromyography (EMG)

    NASA Astrophysics Data System (ADS)

    Soewardi, Hartomo; Azka Rahmayani, Amalia

    2016-01-01

    One of the most common problems in pottery manufacturing process is musculoskeletal disorders on workers. This disorder was caused by uncomfortable posture where the workers sit on the floor with one leg was folded and another was twisted for long duration. Back, waist, buttock, and right knee frequently experience the disorders. The objective of this research is to investigate the muscle contraction at such body part of workers in manufacturing process of pottery. Electromyography is used to investigate the muscle contraction based on the median frequency signal. Focus measurements is conducted on four muscles types. They are lower interscapular muscle on the right and left side, dorsal lumbar muscle, and lateral hamstring muscle. Statistical analysis is conducted to test differences of muscle contraction between female and male. The result of this research showed that the muscle which reached the highest contraction is dorsal lumbar muscle with the average of median frequency is 51,84 Hz. Then followed by lower interscapular muscle on the left side with the average of median frequency is 31,30 hz, lower interscapular muscle on the right side average of median frequency is 31,24 Hz, and lateral hamstring muscle average of median frequency is 21,77 Hz. Based on the statistic analysis result, there were no differences between male and female on left and right lower interscapular muscle and dorsal lumbar muscle but there were differences on lateral hamstring muscle with the significance level is 5%. Besides that, there were differences for all combination muscle types with the level of significance is 5%.

  10. Extracellular adenosine initiates rapid arteriolar vasodilation induced by a single skeletal muscle contraction in hamster cremaster muscle.

    PubMed

    Ross, G A; Mihok, M L; Murrant, C L

    2013-05-01

    Recent studies suggest that adenosine (ADO) can be produced extracellularly in response to skeletal muscle contraction. We tested the hypothesis that a single muscle contraction produces extracellular ADO rapidly enough and in physiologically relevant concentrations to be able to contribute to the rapid vasodilation that occurs at the onset of muscle contraction. We stimulated four to five skeletal muscle fibres in the anaesthetized hamster cremaster preparation in situ and measured the change in diameter of arterioles at a site of overlap with the stimulated muscle fibres before and after a single contraction (stimulus frequencies: 4, 20 and 60 Hz; 250 ms train duration). Muscle fibres were stimulated in the absence and presence of non-specific ADO membrane receptor antagonists 8-phenyltheophylline (8-PT, 10(-6) M) or xanthine amine congener (XAC, 10(-6) M) or an inhibitor of an extracellular source of ADO, ecto-5'-nucleotidase inhibitor α,β-methylene adenosine 5'-diphosphate (AMPCP, 10(-5) M). We observed that the dilatory event at 4 s following a single contraction was significantly inhibited at all stimulus frequencies by an average of 63.9 ± 2.6% by 8-PT. The 20-s dilatory event that occurred at 20 and 60 Hz was significantly inhibited by 53.6 ± 2.6 and 73.8 ± 2.3% by 8-PT and XAC respectively. Further, both the 4- and 20-s dilatory events were significantly inhibited by AMPCP by 78.6 ± 6.6 and 67.1 ± 1.5%, respectively, at each stimulus frequency tested. Our data show that ADO is produced extracellularly during a single muscle contraction and that it is produced rapidly enough and in physiologically relevant concentrations to contribute to the rapid vasodilation in response to muscle contraction. © 2013 The Authors Acta Physiologica © 2013 Scandinavian Physiological Society.

  11. Eccentric contractions disrupt FKBP12 content in mouse skeletal muscle

    PubMed Central

    Baumann, Cory W.; Rogers, Russell G.; Gahlot, Nidhi; Ingalls, Christopher P.

    2014-01-01

    Abstract Strength deficits associated with eccentric contraction‐induced muscle injury stem, in part, from impaired voltage‐gated sarcoplasmic reticulum (SR) Ca2+ release. FKBP12 is a 12‐kD immunophilin known to bind to the SR Ca2+ release channel (ryanodine receptor, RyR1) and plays an important role in excitation‐contraction coupling. To assess the effects of eccentric contractions on FKBP12 content, we measured anterior crural muscle (tibialis anterior [TA], extensor digitorum longus [EDL], extensor hallucis longus muscles) strength and FKBP12 content in pellet and supernatant fractions after centrifugation via immunoblotting from mice before and after a single bout of either 150 eccentric or concentric contractions. There were no changes in peak isometric torque or FKBP12 content in TA muscles after concentric contractions. However, FKBP12 content was reduced in the pelleted fraction immediately after eccentric contractions, and increased in the soluble protein fraction 3 day after injury induction. FKBP12 content was correlated (P = 0.025; R2= 0.38) to strength deficits immediately after injury induction. In summary, eccentric contraction‐induced muscle injury is associated with significant alterations in FKBP12 content after injury, and is correlated with changes in peak isometric torque. PMID:25347864

  12. Contraction-induced muscle damage is unaffected by vitamin E supplementation.

    PubMed

    Beaton, Louise J; Allan, Damon A; Tarnopolsky, Mark A; Tiidus, Peter M; Phillips, Stuart M

    2002-05-01

    Vitamin E supplementation may confer a protective effect against eccentrically biased exercise-induced muscle damage through stabilization of the cell membrane and possibly via inhibition of free radical formation. Evidence supporting a protective role of vitamin E after contraction-induced muscle injury in humans is, however, inconsistent. The present study sought to determine the effect of vitamin E supplementation on indices of exercise-induced muscle damage and the postexercise inflammatory response after performance of repeated eccentric muscle contractions. Young healthy men performed a bout of 240 maximal isokinetic eccentric muscle contractions (0.52 rad.s-1) after being supplemented for 30 d with either vitamin E (N = 9; 1200 IU.d-1) or placebo (N = 7; safflower oil). Measurements of torque (isometric and concentric) decreased (P < 0.05) below preexercise values immediately post- and at 48 h post-exercise. Biopsies taken 24 h postexercise showed a significant increase in the amount of extensive Z-band disruption (P < 0.01); however, neither the torque deficit nor the extent of Z-band disruption were affected by vitamin E. Exercise resulted in increased macrophage cell infiltration (P = 0.05) into muscle, which was also unaffected by vitamin E. Serum CK also increased as a result of the exercise (P < 0.05) with no effect of vitamin E. We conclude that vitamin E supplementation (30 d at 1200 IU.d-1), which resulted in a 2.8-fold higher serum vitamin E concentration (P < 0.01), had no affect on indices of contraction-induced muscle damage nor inflammation (macrophage infiltration) as a result of eccentrically biased muscle contractions.

  13. Control of abdominal and expiratory intercostal muscle activity during vomiting - Role of ventral respiratory group expiratory neurons

    NASA Technical Reports Server (NTRS)

    Miller, Alan D.; Tan, L. K.; Suzuki, Ichiro

    1987-01-01

    The role of ventral respiratory group (VRG) expiratory (E) neurons in the control of abdominal and internal intercostal muscle activity during vomiting was investigated in cats. Two series of experiments were performed: in one, the activity of VRG E neurons was recorded during fictive vomiting in cats that were decerebrated, paralyzed, and artificially ventilated; in the second, the abdominal muscle activity during vomiting was compared before and after sectioning the axons of descending VRG E neurons in decerebrate spontaneously breathing cats. The results show that about two-thirds of VRG E neurons that project at least as far caudally as the lower thoracic cord contribute to internal intercostal muscle activity during vomiting. The remaining VRG E neurons contribute to abdominal muscle activation. As shown by severing the axons of the VRG E neurons, other, as yet unidenified, inputs (either descending from the brain stem or arising from spinal reflexes) can also produce abdominal muscle activation.

  14. Body Mass Normalization for Ultrasound Measurements of Adolescent Lateral Abdominal Muscle Thickness.

    PubMed

    Linek, Pawel; Saulicz, Edward; Wolny, Tomasz; Myśliwiec, Andrzej

    2017-04-01

    The purpose of this study was to determine the value of the allometric parameter for ultrasound measurements of the thickness of the oblique external (OE), internal (OI), and transversus abdominis (TrA) muscles in the adolescent population. The allometric parameter is the slope of the linear regression line between the log transformed body mass and log transformed muscle size measurement. The study included 321 adolescents between the ages of 10 and 17, consisting of 160 boys and 161 girls. The participants were recruited from local schools and attended regular school classes at normal grade levels. All individuals with no signs of scoliosis (screening with use of a scoliometer), and no surgical procedures performed on the trunk area were included. A real-time ultrasound B-scanner with a linear array transducer was used to obtain images of the lateral abdominal muscles from both sides of the body. The correlation between body mass and the OE muscle was r = 0.69; the OI muscle r = 0.68; and the TrA muscle r = 0.53 (in all cases, P < .0001). The allometric parameter for the OE was 0.88296; the OI 0.718756; and the TrA 0.60986. Using these parameters, no significant correlations were found between body mass and the allometric-scaled thickness of the lateral abdominal muscles. Significant positive correlations exist between body mass and lateral abdominal muscle thickness assessed by ultrasound imaging. Therefore, it is reasonable to advise that the values of the allometric parameters for OE, OI, and TrA obtained in this study should be used in other studies performed on adolescents. © 2016 by the American Institute of Ultrasound in Medicine.

  15. Neutrophils contribute to muscle injury and impair its resolution after lengthening contractions in mice

    PubMed Central

    Pizza, Francis X; Peterson, Jennifer M; Baas, Joel H; Koh, Timothy J

    2005-01-01

    We tested the hypotheses that: (1) neutrophil accumulation after contraction-induced muscle injury is dependent on the β2 integrin CD18, (2) neutrophils contribute to muscle injury and oxidative damage after contraction-induced muscle injury, and (3) neutrophils aid the resolution of contraction-induced muscle injury. These hypotheses were tested by exposing extensor digitorum longus (EDL) muscles of mice deficient in CD18 (CD18−/−; Itgb2tm1Bay) and of wild type mice (C57BL/6) to in situ lengthening contractions and by quantifying markers of muscle inflammation, injury, oxidative damage and regeneration/repair. Neutrophil concentrations were significantly elevated in wild type mice at 6 h and 3 days post-lengthening contractions; however, neutrophils remained at control levels at these time points in CD18−/− mice. These data indicate that CD18 is required for neutrophil accumulation after contraction-induced muscle injury. Histological and functional (isometric force deficit) signs of muscle injury and total carbonyl content, a marker of oxidative damage, were significantly higher in wild type relative to CD18−/− mice 3 days after lengthening contractions. These data show that neutrophils exacerbate contraction-induced muscle injury. After statistically controlling for differences in the force deficit at 3 days, wild type mice also demonstrated a higher force deficit at 7 days, a lower percentage of myofibres expressing embryonic myosin heavy chain at 3 and 7 days, and a smaller cross sectional area of central nucleated myofibres at 14 days relative to CD18−/− mice. These observations suggest that neutrophils impair the restoration of muscle structure and function after injury. In conclusion, neutrophil accumulation after contraction-induced muscle injury is dependent on CD18. Furthermore, neutrophils appear to contribute to muscle injury and impair some of the events associated with the resolution of contraction-induced muscle injury. PMID

  16. Effect of intermittent eccentric contractions on symptoms of muscle microinjury.

    PubMed

    Teague, B N; Schwane, J A

    1995-10-01

    The purpose was to determine whether varying the duration of rest between contractions affects selected symptoms of eccentric contraction-induced skeletal muscle microinjury. Thirty-three women were assigned to three groups (N = 11). Each performed one bout of exercise with each arm involving 10 eccentric contractions of the elbow flexor muscles, lowering a load equaling 60% of maximal static force. One arm exercised continuously; the other exercised with rest periods of 15 s, 5 min, or 10 min between contractions, depending on the group. Preexercise and 0, 24, and 48 h postexercise, symptoms of microinjury in the elbow flexor muscles were assessed: soreness and changes in strength, resting elbow angle ("musculotendinous stiffness"), and arm girth ("swelling"). For all groups combined, 10 continuous contractions caused changes (P < 0.05) in all variables at every measurement time. For example, soreness ratings (0-10 scale) were 4.3 +/- 2.0 (24 h) and 4.3 +/- 2.1 (48 h) and strength was reduced 18% 0 h postexercise. Responses were similar with 15 s of rest between contractions. Although they were moderated, symptoms occurred even with 5 and 10 min of rest. With 10 min between contractions, soreness occurred (e.g., 2.4 +/- 1.5 [24 h]) and strength was 17% reduced 0 h postexercise. Results are most consistent with a mechanical cause of eccentric contraction-induced muscle microinjury, rather than a metabolic or other factor with a short recovery time, although involvement of the latter cannot be ruled out.

  17. Ultrasound Assessment of Abdominal Muscle Thickness in Postpartum vs Nulliparous Women.

    PubMed

    Weis, Carol Ann; Triano, John J; Barrett, Jon; Campbell, Michelle D; Croy, Martine; Roeder, Jessica

    2015-06-01

    The purpose of this study was to determine the effect size in measurable change of abdominal musculature morphology using ultrasonography in postpartum women within 1 month of a healthy, vaginal delivery. One hundred fifty-six participants were recruited for this study. B-mode ultrasound imaging was used to measure abdominal muscle thickness on 80 nulliparous women and 76 mothers who had delivered within the past 4 weeks. Measures were taken for the upper and lower rectus abdominus, external and internal obliques, and transversus abdominus at rest. Statistically significant differences were found in the thickness of the rectus abdominus muscle at both sites; upper (P < .0001) and lower (P < .0001) as well as the internal oblique (P < .0001). All 3 muscles were thinner in postpartum participants (8.29 ± 1.83 mm, 8.89 ± 2.29 mm, and 7.06 ± 1.82 mm, respectively) within the first month of delivery than in controls (10.82 ± 1.93 mm, 11.13 ± 2.38 mm, and 8.36 ± 1.87 mm, respectively). Large effect sizes were found for the influence of pregnancy on the rectus muscle segments (1.35 for the upper rectus abdominus and 1.00 for the lower rectus abdominus) and a medium effect size for the internal oblique (0.71). No significant differences were observed in the remaining 2 muscles. This study showed that there are differences in morphology of the abdominal muscles in pregnant women vs nonpregnant controls. The large effect sizes reported may provide the basis for future studies examining relationships between morphology, functional change, and back pain during pregnancy. Copyright © 2015 National University of Health Sciences. Published by Elsevier Inc. All rights reserved.

  18. Age-associated changes in muscle activity during isometric contraction.

    PubMed

    Arjunan, Sridhar P; Kumar, Dinesh K

    2013-04-01

    We investigated the effect of age on the complexity of muscle activity and the variance in the force of isometric contraction. Surface electromyography (sEMG) from biceps brachii muscle and force of contraction were recorded from 96 subjects (20-70 years of age) during isometric contractions. There was a reduction in the complexity of sEMG associated with aging. The relationship of age and complexity was approximated using a bilinear fit, with the average knee point at 45 years. There was an age-associated increase in the coefficient of variation (CoV) of the force of muscle contraction, and this increase was correlated with the decrease in complexity of sEMG (r(2) = 0.76). There was an age-associated increase in CoV and also a reduction in the complexity of sEMG. The correlation between these 2 factors can be explained based on the age-associated increase in motor unit density. Copyright © 2012 Wiley Periodicals, Inc.

  19. In-Vivo Measurement of Muscle Tension: Dynamic Properties of the MC Sensor during Isometric Muscle Contraction

    PubMed Central

    Đorđević, Srđan; Tomažič, Sašo; Narici, Marco; Pišot, Rado; Meglič, Andrej

    2014-01-01

    Skeletal muscle is the largest tissue structure in our body and plays an essential role for producing motion through integrated action with bones, tendons, ligaments and joints, for stabilizing body position, for generation of heat through cell respiration and for blood glucose disposal. A key function of skeletal muscle is force generation. Non-invasive and selective measurement of muscle contraction force in the field and in clinical settings has always been challenging. The aim of our work has been to develop a sensor that can overcome these difficulties and therefore enable measurement of muscle force during different contraction conditions. In this study, we tested the mechanical properties of a “Muscle Contraction” (MC) sensor during isometric muscle contraction in different length/tension conditions. The MC sensor is attached so that it indents the skin overlying a muscle group and detects varying degrees of tension during muscular contraction. We compared MC sensor readings over the biceps brachii (BB) muscle to dynamometric measurements of force of elbow flexion, together with recordings of surface EMG signal of BB during isometric contractions at 15° and 90° of elbow flexion. Statistical correlation between MC signal and force was very high at 15° (r = 0.976) and 90° (r = 0.966) across the complete time domain. Normalized SD or σN = σ/max(FMC) was used as a measure of linearity of MC signal and elbow flexion force in dynamic conditions. The average was 8.24% for an elbow angle of 90° and 10.01% for an elbow of angle 15°, which indicates high linearity and good dynamic properties of MC sensor signal when compared to elbow flexion force. The next step of testing MC sensor potential will be to measure tension of muscle-tendon complex in conditions when length and tension change simultaneously during human motion. PMID:25256114

  20. On the thermodynamics of smooth muscle contraction

    NASA Astrophysics Data System (ADS)

    Stålhand, Jonas; McMeeking, Robert M.; Holzapfel, Gerhard A.

    2016-09-01

    Cell function is based on many dynamically complex networks of interacting biochemical reactions. Enzymes may increase the rate of only those reactions that are thermodynamically consistent. In this paper we specifically treat the contraction of smooth muscle cells from the continuum thermodynamics point of view by considering them as an open system where matter passes through the cell membrane. We systematically set up a well-known four-state kinetic model for the cross-bridge interaction of actin and myosin in smooth muscle, where the transition between each state is driven by forward and reverse reactions. Chemical, mechanical and energy balance laws are provided in local forms, while energy balance is also formulated in the more convenient temperature form. We derive the local (non-negative) production of entropy from which we deduce the reduced entropy inequality and the constitutive equations for the first Piola-Kirchhoff stress tensor, the heat flux, the ion and molecular flux and the entropy. One example for smooth muscle contraction is analyzed in more detail in order to provide orientation within the established general thermodynamic framework. In particular the stress evolution, heat generation, muscle shorting rate and a condition for muscle cooling are derived.

  1. The effects of muscle contraction and recombinant osteocalcin on insulin sensitivity ex vivo.

    PubMed

    Levinger, I; Lin, X; Zhang, X; Brennan-Speranza, T C; Volpato, B; Hayes, A; Jerums, G; Seeman, E; McConell, G

    2016-02-01

    We tested whether GPRC6A, the putative receptor of undercarboxylated osteocalcin (ucOC), is present in mouse muscle and whether ucOC increases insulin sensitivity following ex vivo muscle contraction. GPPRC6A is expressed in mouse muscle and in the mouse myotubes from a cell line. ucOC potentiated the effect of ex vivo contraction on insulin sensitivity. Acute exercise increases skeletal muscle insulin sensitivity. In humans, exercise increases circulating ucOC, a hormone that increases insulin sensitivity in rodents. We tested whether GPRC6A, the putative receptor of ucOC, is present in mouse muscle and whether recombinant ucOC increases insulin sensitivity in both C2C12 myotubes and whole mouse muscle following ex vivo muscle contraction. Glucose uptake was examined in C2C12 myotubes that express GPRC6A following treatment with insulin alone or with insulin and increasing ucOC concentrations (0.3, 3, 10 and 30 ng/ml). In addition, glucose uptake, phosphorylated (p-)AKT and p-AS160 were examined ex vivo in extensor digitorum longus (EDL) dissected from C57BL/6J wild-type mice, at rest, following insulin alone, after muscle contraction followed by insulin and after muscle contraction followed by recombinant ucOC then insulin exposure. We observed protein expression of the likely receptor for ucOC, GPRC6A, in whole muscle sections and differentiated mouse myotubes. We observed reduced GPRC6A expression following siRNA transfection. ucOC significantly increased insulin-stimulated glucose uptake dose-dependently up to 10 ng/ml, in differentiated mouse C2C12 myotubes. Insulin increased EDL glucose uptake (∼30 %, p < 0.05) and p-AKT and p-AKT/AKT compared with rest (all p < 0.05). Contraction prior to insulin increased muscle glucose uptake (∼25 %, p < 0.05), p-AKT, p-AKT/AKT, p-AS160 and p-AS160/AS160 compared with contraction alone (all p < 0.05). ucOC after contraction increased insulin-stimulated muscle glucose uptake (∼12 % p < 0

  2. Animal electricity, Ca2+ and muscle contraction. A brief history of muscle research.

    PubMed

    Martonosi, A N

    2000-01-01

    This brief review attempts to summarize some of the major phases of muscle research from Leeuwenhoek's description of sarcomeres in 1674, through Galvani's observation of "animal electricity" in 1791, to the discovery of Ca2+ as the key messenger in the coupling of nerve excitation to muscle contraction. The emerging molecular mechanism of the contraction process is one of the great achievements of biology, reflecting the intimate links between physics, chemistry and the life Sciences in the solution of biological problems.

  3. Efficiency of muscle contraction. The chemimechanic equilibrium

    NASA Astrophysics Data System (ADS)

    Becker, E. W.

    1991-10-01

    Although muscle contraction is one of the principal themes of biological research, the exact mechanism whereby the chemical free energy of ATP hydrolysis is converted into mechanical work remains elusive. The high thermodynamic efficiency of the process, above all, is difficult to explain on the basis of present theories. A model of the elementary effect in muscle contraction is proposed which aims at high thermodynamic efficiency based on an approximate equilibrium between chemical and mechanical forces throughout the transfer of free energy. The experimental results described in the literature support the assumption that chemimechanic equilibrium is approximated by a free energy transfer system based on the binding of divalent metal ions to the myosin light chains. Muscle contraction demonstrated without light chains is expected to proceed with a considerably lower efficiency. Free energy transfer systems based on the binding of ions to proteins seem to be widespread in the cell. By establishing an approximate chemimechanic equilibrium, they could facilitate biological reactions considerably and save large amounts of free energy. The concept of chemimechanic equilibrium is seen as a supplementation to the concept of chemiosmotic equilibrium introduced for the membrane transport by P. Mitchell.

  4. A chemical kinetic theory on muscle contraction and spontaneous oscillation

    NASA Astrophysics Data System (ADS)

    Guo, Wei-Sheng; Luo, Liao-Fu; Li, Qian-Zhong

    2002-09-01

    From a set of chemical kinetic equations describing the actin-activated myosin ATPase cycle, we show that, in active muscle, the fraction of myosin heads in any given biochemical state is independent of both [ADP] and [P i]. Combining muscle mechanics data of Pate and Cooke, we deduce the muscle state equation in which muscle force is a state variable of the muscle system. The theoretical results are consistent with Baker's experimental data but somewhat different from conventional muscle theory. Based on the muscle state equation with the knowledge of special structure of muscle, we present a physical mechanism which can lead to both contraction and oscillation of sarcomeres. It explains the muscle spontaneous oscillatory contraction in a natural way and agrees well with experimental data. The model will be helpful in studying the oscillatory behavior of cilia and flagella.

  5. Metabolic profiling of muscle contraction in lean compared with obese rodents.

    PubMed

    Thyfault, John P; Cree, Melanie G; Tapscott, Edward B; Bell, Jill A; Koves, Timothy R; Ilkayeva, Olga; Wolfe, Robert R; Dohm, G Lynis; Muoio, Deborah M

    2010-09-01

    Interest in the pathophysiological relevance of intramuscular triacylglycerol (IMTG) accumulation has grown from numerous studies reporting that abnormally high glycerolipid levels in tissues of obese and diabetic subjects correlate negatively with glucose tolerance. Here, we used a hindlimb perfusion model to examine the impact of obesity and elevated IMTG levels on contraction-induced changes in skeletal muscle fuel metabolism. Comprehensive lipid profiling was performed on gastrocnemius muscles harvested from lean and obese Zucker rats immediately and 25 min after 15 min of one-legged electrically stimulated contraction compared with the contralateral control (rested) limbs. Predictably, IMTG content was grossly elevated in control muscles from obese rats compared with their lean counterparts. In muscles of obese (but not lean) rats, contraction resulted in marked hydrolysis of IMTG, which was then restored to near resting levels during 25 min of recovery. Despite dramatic phenotypical differences in contraction-induced IMTG turnover, muscle levels of diacylglycerol (DAG) and long-chain acyl-CoAs (LCACoA) were surprisingly similar between groups. Tissue profiles of acylcarnitine metabolites suggested that the surfeit of IMTG in obese rats fueled higher rates of fat oxidation relative to the lean group. Muscles of the obese rats had reduced lactate levels immediately following contraction and higher glycogen resynthesis during recovery, consistent with a lipid-associated glucose-sparing effect. Together, these findings suggest that contraction-induced mobilization of local lipid reserves in obese muscles promotes beta-oxidation, while discouraging glucose utilization. Further studies are necessary to determine whether persistent oxidation of IMTG-derived fatty acids contributes to systemic glucose intolerance in other physiological settings.

  6. Computation and evaluation of features of surface electromyogram to identify the force of muscle contraction and muscle fatigue.

    PubMed

    Arjunan, Sridhar P; Kumar, Dinesh K; Naik, Ganesh

    2014-01-01

    The relationship between force of muscle contraction and muscle fatigue with six different features of surface electromyogram (sEMG) was determined by conducting experiments on thirty-five volunteers. The participants performed isometric contractions at 50%, 75%, and 100% of their maximum voluntary contraction (MVC). Six features were considered in this study: normalised spectral index (NSM5), median frequency, root mean square, waveform length, normalised root mean square (NRMS), and increase in synchronization (IIS) index. Analysis of variance (ANOVA) and linear regression analysis were performed to determine the significance of the feature with respect to the three factors: muscle force, muscle fatigue, and subject. The results show that IIS index of sEMG had the highest correlation with muscle fatigue and the relationship was statistically significant (P < 0.01), while NSM5 associated best with level of muscle contraction (%MVC) (P < 0.01). Both of these features were not affected by the intersubject variations (P > 0.05).

  7. Computation and Evaluation of Features of Surface Electromyogram to Identify the Force of Muscle Contraction and Muscle Fatigue

    PubMed Central

    Arjunan, Sridhar P.; Kumar, Dinesh K.; Naik, Ganesh

    2014-01-01

    The relationship between force of muscle contraction and muscle fatigue with six different features of surface electromyogram (sEMG) was determined by conducting experiments on thirty-five volunteers. The participants performed isometric contractions at 50%, 75%, and 100% of their maximum voluntary contraction (MVC). Six features were considered in this study: normalised spectral index (NSM5), median frequency, root mean square, waveform length, normalised root mean square (NRMS), and increase in synchronization (IIS) index. Analysis of variance (ANOVA) and linear regression analysis were performed to determine the significance of the feature with respect to the three factors: muscle force, muscle fatigue, and subject. The results show that IIS index of sEMG had the highest correlation with muscle fatigue and the relationship was statistically significant (P < 0.01), while NSM5 associated best with level of muscle contraction (%MVC) (P < 0.01). Both of these features were not affected by the intersubject variations (P > 0.05). PMID:24995275

  8. Dynamics of myosin-driven skeletal muscle contraction: I. Steady-state force generation.

    PubMed

    Lan, Ganhui; Sun, Sean X

    2005-06-01

    Skeletal muscle contraction is a canonical example of motor-driven force generation. Despite the long history of research in this topic, a mechanistic explanation of the collective myosin force generation is lacking. We present a theoretical model of muscle contraction based on the conformational movements of individual myosins and experimentally measured chemical rate constants. Detailed mechanics of the myosin motor and the geometry of the sarcomere are taken into account. Two possible scenarios of force generation are examined. We find only one of the scenarios can give rise to a plausible contraction mechanism. We propose that the synchrony in muscle contraction is due to a force-dependent ADP release step. Computational results of a half sarcomere with 150 myosin heads can explain the experimentally measured force-velocity relationship and efficiency data. We predict that the number of working myosin motors increases as the load force is increased, thus showing synchrony among myosin motors during muscle contraction. We also find that titin molecules anchoring the thick filament are passive force generators in assisting muscle contraction.

  9. Dynamics of Myosin-Driven Skeletal Muscle Contraction: I. Steady-State Force Generation

    PubMed Central

    Lan, Ganhui; Sun, Sean X.

    2005-01-01

    Skeletal muscle contraction is a canonical example of motor-driven force generation. Despite the long history of research in this topic, a mechanistic explanation of the collective myosin force generation is lacking. We present a theoretical model of muscle contraction based on the conformational movements of individual myosins and experimentally measured chemical rate constants. Detailed mechanics of the myosin motor and the geometry of the sarcomere are taken into account. Two possible scenarios of force generation are examined. We find only one of the scenarios can give rise to a plausible contraction mechanism. We propose that the synchrony in muscle contraction is due to a force-dependent ADP release step. Computational results of a half sarcomere with 150 myosin heads can explain the experimentally measured force-velocity relationship and efficiency data. We predict that the number of working myosin motors increases as the load force is increased, thus showing synchrony among myosin motors during muscle contraction. We also find that titin molecules anchoring the thick filament are passive force generators in assisting muscle contraction. PMID:15778440

  10. Impedance Alterations in Healthy and Diseased Mice During Electrically Induced Muscle Contraction.

    PubMed

    Sanchez, Benjamin; Li, Jia; Geisbush, Tom; Bardia, Ramon Bragos; Rutkove, Seward B

    2016-08-01

    Alterations in the health of muscles can be evaluated through the use of electrical impedance myography (EIM). To date, however, nearly all work in this field has relied upon the measurement of muscle at rest. To provide an insight into the contractile mechanisms of healthy and disease muscle, we evaluated the alterations in the spectroscopic impedance behavior of muscle during the active process of muscle contraction. The gastrocnemii from a total of 13 mice were studied (five wild type, four muscular dystrophy animals, and four amyotrophic lateral sclerosis animals). Muscle contraction was induced via monophasic current pulse stimulation of the sciatic nerve. Simultaneously, multisine EIM (1 kHz to 1 MHz) and force measurements of the muscle were performed. Stimulation was applied at three different rates to produce mild, moderate, and strong contractions. We identified changes in both single and multifrequency data, as assessed by the Cole impedance model parameters. The processes of contraction and relaxation were clearly identified in the impedance spectra and quantified via derivative plots. Reductions in the center frequency fc were observed during the contraction consistent with the increasing muscle fiber diameter. Different EIM stimulation rate-dependencies were also detected across the three groups of animals.

  11. Regulation of Contraction by the Thick Filaments in Skeletal Muscle.

    PubMed

    Irving, Malcolm

    2017-12-19

    Contraction of skeletal muscle cells is initiated by a well-known signaling pathway. An action potential in a motor nerve triggers an action potential in a muscle cell membrane, a transient increase of intracellular calcium concentration, binding of calcium to troponin in the actin-containing thin filaments, and a structural change in the thin filaments that allows myosin motors from the thick filaments to bind to actin and generate force. This calcium/thin filament mediated pathway provides the "START" signal for contraction, but it is argued that the functional response of the muscle cell, including the speed of its contraction and relaxation, adaptation to the external load, and the metabolic cost of contraction is largely determined by additional mechanisms. This review considers the role of the thick filaments in those mechanisms, and puts forward a paradigm for the control of contraction in skeletal muscle in which both the thick and thin filaments have a regulatory function. The OFF state of the thick filament is characterized by helical packing of most of the myosin head or motor domains on the thick filament surface in a conformation that makes them unavailable for actin binding or ATP hydrolysis, although a small fraction of the myosin heads are constitutively ON. The availability of the majority fraction of the myosin heads for contraction is controlled in part by the external load on the muscle, so that these heads only attach to actin and hydrolyze ATP when they are required. This phenomenon seems to be the major determinant of the well-known force-velocity relationship of muscle, and controls the metabolic cost of contraction. The regulatory state of the thick filament also seems to control the dynamics of both muscle activation and relaxation. Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  12. Evaluating abdominal core muscle fatigue: Assessment of the validity and reliability of the prone bridging test.

    PubMed

    De Blaiser, C; De Ridder, R; Willems, T; Danneels, L; Vanden Bossche, L; Palmans, T; Roosen, P

    2018-02-01

    The aims of this study were to research the amplitude and median frequency characteristics of selected abdominal, back, and hip muscles of healthy subjects during a prone bridging endurance test, based on surface electromyography (sEMG), (a) to determine if the prone bridging test is a valid field test to measure abdominal muscle fatigue, and (b) to evaluate if the current method of administrating the prone bridging test is reliable. Thirty healthy subjects participated in this experiment. The sEMG activity of seven abdominal, back, and hip muscles was bilaterally measured. Normalized median frequencies were computed from the EMG power spectra. The prone bridging tests were repeated on separate days to evaluate inter and intratester reliability. Significant differences in normalized median frequency slope (NMF slope ) values between several abdominal, back, and hip muscles could be demonstrated. Moderate-to-high correlation coefficients were shown between NMF slope values and endurance time. Multiple backward linear regression revealed that the test endurance time could only be significantly predicted by the NMF slope of the rectus abdominis. Statistical analysis showed excellent reliability (ICC=0.87-0.89). The findings of this study support the validity and reliability of the prone bridging test for evaluating abdominal muscle fatigue. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  13. Poorly Understood Aspects of Striated Muscle Contraction

    PubMed Central

    Månsson, Alf

    2015-01-01

    Muscle contraction results from cyclic interactions between the contractile proteins myosin and actin, driven by the turnover of adenosine triphosphate (ATP). Despite intense studies, several molecular events in the contraction process are poorly understood, including the relationship between force-generation and phosphate-release in the ATP-turnover. Different aspects of the force-generating transition are reflected in the changes in tension development by muscle cells, myofibrils and single molecules upon changes in temperature, altered phosphate concentration, or length perturbations. It has been notoriously difficult to explain all these events within a given theoretical framework and to unequivocally correlate observed events with the atomic structures of the myosin motor. Other incompletely understood issues include the role of the two heads of myosin II and structural changes in the actin filaments as well as the importance of the three-dimensional order. We here review these issues in relation to controversies regarding basic physiological properties of striated muscle. We also briefly consider actomyosin mutation effects in cardiac and skeletal muscle function and the possibility to treat these defects by drugs. PMID:25961006

  14. Poorly understood aspects of striated muscle contraction.

    PubMed

    Månsson, Alf; Rassier, Dilson; Tsiavaliaris, Georgios

    2015-01-01

    Muscle contraction results from cyclic interactions between the contractile proteins myosin and actin, driven by the turnover of adenosine triphosphate (ATP). Despite intense studies, several molecular events in the contraction process are poorly understood, including the relationship between force-generation and phosphate-release in the ATP-turnover. Different aspects of the force-generating transition are reflected in the changes in tension development by muscle cells, myofibrils and single molecules upon changes in temperature, altered phosphate concentration, or length perturbations. It has been notoriously difficult to explain all these events within a given theoretical framework and to unequivocally correlate observed events with the atomic structures of the myosin motor. Other incompletely understood issues include the role of the two heads of myosin II and structural changes in the actin filaments as well as the importance of the three-dimensional order. We here review these issues in relation to controversies regarding basic physiological properties of striated muscle. We also briefly consider actomyosin mutation effects in cardiac and skeletal muscle function and the possibility to treat these defects by drugs.

  15. Human muscle fascicle behavior in agonist and antagonist isometric contractions.

    PubMed

    Simoneau, Emilie M; Longo, Stefano; Seynnes, Olivier R; Narici, Marco V

    2012-01-01

    The aim of this study was to compare, at a given level of electromyographic (EMG) activity, the behavior of dorsiflexor and plantarflexor muscles as assessed via their architecture (pennation angle and fiber length) during agonist or antagonist isometric contractions. Real-time ultrasonography and EMG activity of gastrocnemius medialis (GM) and tibialis anterior (TA) muscles were obtained while young males performed ramp isometric contractions in dorsi- and plantarflexion. For both muscles, at a similar level of EMG activity, fiber length was longer, and pennation angle was smaller, during antagonist than during agonist contractions. These results indicate that, at similar levels of EMG activity, GM and TA muscles elicit a higher mechanical output while acting as an antagonist. These findings have important implications for muscle function testing. They show that estimation of antagonistic force using the common method based on the EMG/net torque relationship yields underestimated values. Copyright © 2011 Wiley Periodicals, Inc.

  16. Action potentials drive body wall muscle contractions in Caenorhabditis elegans

    PubMed Central

    Gao, Shangbang; Zhen, Mei

    2011-01-01

    The sinusoidal locomotion exhibited by Caenorhabditis elegans predicts a tight regulation of contractions and relaxations of its body wall muscles. Vertebrate skeletal muscle contractions are driven by voltage-gated sodium channel–dependent action potentials. How coordinated motor outputs are regulated in C. elegans, which does not have voltage-gated sodium channels, remains unknown. Here, we show that C. elegans body wall muscles fire all-or-none, calcium-dependent action potentials that are driven by the L-type voltage-gated calcium and Kv1 voltage-dependent potassium channels. We further demonstrate that the excitatory and inhibitory motoneuron activities regulate the frequency of action potentials to coordinate muscle contraction and relaxation, respectively. This study provides direct evidence for the dual-modulatory model of the C. elegans motor circuit; moreover, it reveals a mode of motor control in which muscle cells integrate graded inputs of the nervous system and respond with all-or-none electrical signals. PMID:21248227

  17. Mechanism linking glycogen concentration and glycogenolytic rate in perfused contracting rat skeletal muscle.

    PubMed Central

    Hespel, P; Richter, E A

    1992-01-01

    The influence of differences in glycogen concentration on glycogen breakdown and on phosphorylase activity was investigated in perfused contracting rat skeletal muscle. The rats were preconditioned by a combination of swimming exercise and diet (carbohydrate-free or carbohydrate-rich) in order to obtain four sub-groups of rats with varying resting muscle glycogen concentrations (range 10-60 mumol/g wet wt.). Pre-contraction muscle glycogen concentration was closely positively correlated with glycogen breakdown over 15 min of intermittent short tetanic contractions (r = 0.75; P less than 0.001; n = 56) at the same tension development and oxygen uptake. Additional studies in supercompensated and glycogen-depleted hindquarters during electrical stimulation for 20 s or 2 min revealed that the difference in glycogenolytic rate was found at the beginning rather than at the end of the contraction period. Phosphorylase alpha activity was approximately twice as high (P less than 0.001) in supercompensated muscles as in glycogen-depleted muscles after 20 s as well as after 2 min of contractions. It is concluded that glycogen concentration is an important determinant of phosphorylase activity in contracting skeletal muscle, and probably via this mechanism a regulator of glycogenolytic rate during muscle contraction. PMID:1622395

  18. Comparison of the efficiency of rat papillary muscles during afterloaded isotonic contractions and contractions with sinusoidal length changes.

    PubMed

    Mellors, L J; Gibbs, C L; Barclay, C J

    2001-05-01

    The results of previous studies suggest that the maximum mechanical efficiency of rat papillary muscles is lower during a contraction protocol involving sinusoidal length changes than during one involving afterloaded isotonic contractions. The aim of this study was to compare directly the efficiency of isolated rat papillary muscle preparations in isotonic and sinusoidal contraction protocols. Experiments were performed in vitro (27 degrees C) using left ventricular papillary muscles from adult rats. Each preparation performed three contraction protocols: (i) low-frequency afterloaded isotonic contractions (10 twitches at 0.2 Hz), (ii) sinusoidal length change contractions with phasic stimulation (40 twitches at 2 Hz) and (iii) high-frequency afterloaded isotonic contractions (40 twitches at 2 Hz). The first two protocols resembled those used in previous studies and the third combined the characteristics of the first two. The parameters for each protocol were adjusted to those that gave maximum efficiency. For the afterloaded isotonic protocols, the afterload was set to 0.3 of the maximum developed force. The sinusoidal length change protocol incorporated a cycle amplitude of +/-5% resting length and a stimulus phase of -10 degrees. Measurements of force output, muscle length change and muscle temperature change were used to calculate the work and heat produced during and after each protocol. Net mechanical efficiency was defined as the proportion of the energy (enthalpy) liberated by the muscle that appeared as work. The efficiency in the low-frequency, isotonic contraction protocol was 21.1+/-1.4% (mean +/- s.e.m., N=6) and that in the sinusoidal protocol was 13.2+/-0.7%, consistent with previous results. This difference was not due to the higher frequency or greater number of twitches because efficiency in the high-frequency, isotonic protocol was 21.5+/-1.0%. Although these results apparently confirm that efficiency is protocol-dependent, additional experiments

  19. Alcohol intoxication following muscle contraction in mice decreases muscle protein synthesis but not mTOR signal transduction.

    PubMed

    Steiner, Jennifer L; Lang, Charles H

    2015-01-01

    Alcohol (ethanol [EtOH]) intoxication antagonizes stimulation of muscle protein synthesis and mammalian target of rapamycin (mTOR) signaling. However, whether the anabolic response can be reversed when alcohol is consumed after the stimulus is unknown. A single bout of electrically stimulated muscle contractions (10 sets of 6 contractions) was induced in fasted male C57BL/6 mice 2 hours prior to alcohol intoxication. EtOH was injected intraperitoneally (3 g/kg), and the gastrocnemius/plantaris muscle complex was collected 2 hours later from the stimulated and contralateral unstimulated control leg. Muscle contraction increased protein synthesis 28% in control mice, while EtOH abolished this stimulation-induced increase. Further, EtOH suppressed the rate of synthesis ~75% compared to control muscle irrespective of stimulation. This decrease was associated with impaired protein elongation as EtOH increased the phosphorylation of eEF2 Thr(56) . In contrast, stimulation-induced increases in mTOR protein complex-1 (mTORC1) (S6K1 Thr(421) /Ser(424) , S6K1 Thr(389) , rpS6 Ser(240/244) , and 4E-BP1 Thr(37/46) ) and mitogen-activated protein kinase (MAPK) (JNK Thr(183) /Tyr(185) , p38 Thr(180) /Tyr(182) , and rpS6S(235/236) ) signaling were not reversed by acute EtOH. These data suggest that EtOH-induced decreases in protein synthesis in fasted mice may be independent of mTORC1 and MAPK signaling following muscle contraction and instead due to the antagonistic actions of EtOH on mRNA translation elongation. Therefore, EtOH suppresses the contraction-induced increase in protein synthesis, and over time has the potential to prevent skeletal muscle hypertrophy induced by repeated muscle contraction. Copyright © 2015 by the Research Society on Alcoholism.

  20. Alcohol intoxication following muscle contraction in mice decreases muscle protein synthesis but not mTOR signal transduction

    PubMed Central

    Steiner, Jennifer L.; Lang, Charles H.

    2014-01-01

    Background Alcohol [ethanol (EtOH)] intoxication antagonizes stimulation of muscle protein synthesis and mTOR signaling. However, whether the anabolic response can be reversed when alcohol is consumed after the stimulus is unknown. Methods A single bout of electrically stimulated muscle contractions (10 sets of 6 contractions) were induced in fasted male C57BL/6 mice 2 h prior to alcohol intoxication. EtOH was injected IP (3g/kg) and the gastrocnemius/plantaris muscle complex was collected 2 h later from the stimulated and contralateral unstimulated control leg. Results Muscle contraction increased protein synthesis 28% in control mice while EtOH abolished this stimulation-induced increase. Further, EtOH suppressed the rate of synthesis ~75% compared to control muscle irrespective of stimulation. This decrease was associated with impaired protein elongation as EtOH increased the phosphorylation of eEF2 Thr56. In contrast, stimulation-induced increases in mTORC1 (S6K1 Thr421/Ser424, S6K1 Thr389, rpS6 Ser240/244, 4E-BP1 Thr37/46) and MAPK (JNK Thr183/Tyr185, p38 Thr180/Tyr182, and rpS6S235/236) signaling were not reversed by acute EtOH. Conclusion These data suggest that EtOH-induced decreases in protein synthesis in fasted mice may be independent of mTORC1 and MAPK signaling following muscle contraction and instead due to the antagonistic actions of EtOH on mRNA translation elongation. Therefore, EtOH suppresses the contraction-induced increase in protein synthesis and over time has the potential to prevent skeletal muscle hypertrophy induced by repeated muscle contraction. PMID:25623400

  1. Skeletal muscle contraction in protecting joints and bones by absorbing mechanical impacts

    NASA Astrophysics Data System (ADS)

    Rudenko, O. V.; Tsyuryupa, S.; Sarvazyan, A.

    2016-09-01

    We have previously hypothesized that the dissipation of mechanical energy of external impact is a fundamental function of skeletal muscle in addition to its primary function to convert chemical energy into mechanical energy. In this paper, a mathematical justification of this hypothesis is presented. First, a simple mechanical model, in which the muscle is considered as a simple Hookean spring, is considered. This analysis serves as an introduction to the consideration of a biomechanical model taking into account the molecular mechanism of muscle contraction, kinetics of myosin bridges, sarcomere dynamics, and tension of muscle fibers. It is shown that a muscle behaves like a nonlinear and adaptive spring tempering the force of impact and increasing the duration of the collision. The temporal profiles of muscle reaction to the impact as functions of the levels of muscle contraction, durations of the impact front, and the time constants of myosin bridges closing, are obtained. The absorption of mechanical shock energy is achieved due to the increased viscoelasticity of the contracting skeletal muscle. Controlling the contraction level allows for the optimization of the stiffness and viscosity of the muscle necessary for the protection of the joints and bones.

  2. Complex myograph allows the examination of complex muscle contractions for the assessment of muscle force, shortening, velocity, and work in vivo

    PubMed Central

    Rahe-Meyer, Niels; Pawlak, Matthias; Weilbach, Christian; Osthaus, Wilhelm Alexander; Ruhschulte, Hainer; Solomon, Cristina; Piepenbrock, Siegfried; Winterhalter, Michael

    2008-01-01

    Background The devices used for in vivo examination of muscle contractions assess only pure force contractions and the so-called isokinetic contractions. In isokinetic experiments, the extremity and its muscle are artificially moved with constant velocity by the measuring device, while a tetanic contraction is induced in the muscle, either by electrical stimulation or by maximal voluntary activation. With these systems, experiments cannot be performed at pre-defined, constant muscle length, single contractions cannot be evaluated individually and the separate examination of the isometric and the isotonic components of single contractions is not possible. Methods The myograph presented in our study has two newly developed technical units, i.e. a). a counterforce unit which can load the muscle with an adjustable, but constant force and b). a length-adjusting unit which allows for both the stretching and the contraction length to be infinitely adjustable independently of one another. The two units support the examination of complex types of contraction and store the counterforce and length-adjusting settings, so that these conditions may be accurately reapplied in later sessions. Results The measurement examples presented show that the muscle can be brought to every possible pre-stretching length and that single isotonic or complex isometric-isotonic contractions may be performed at every length. The applied forces act during different phases of contraction, resulting into different pre- and after-loads that can be kept constant – uninfluenced by the contraction. Maximal values for force, shortening, velocity and work may be obtained for individual muscles. This offers the possibility to obtain information on the muscle status and to monitor its changes under non-invasive measurement conditions. Conclusion With the Complex Myograph, the whole spectrum of a muscle's mechanical characteristics may be assessed. PMID:18616815

  3. Adaptive strength gains in dystrophic muscle exposed to repeated bouts of eccentric contraction

    PubMed Central

    Call, Jarrod A.; Eckhoff, Michael D.; Baltgalvis, Kristen A.; Warren, Gordon L.

    2011-01-01

    The objective of this study was to determine the functional recovery and adaptation of dystrophic muscle to multiple bouts of contraction-induced injury. Because lengthening (i.e., eccentric) contractions are extremely injurious for dystrophic muscle, it was considered that repeated bouts of such contractions would exacerbate the disease phenotype in mdx mice. Anterior crural muscles (tibialis anterior and extensor digitorum longus) and posterior crural muscles (gastrocnemius, soleus, and plantaris) from mdx mice performed one or five repeated bouts of 100 electrically stimulated eccentric contractions in vivo, and each bout was separated by 10–18 days. Functional recovery from one bout was achieved 7 days after injury, which was in contrast to a group of wild-type mice, which still showed a 25% decrement in electrically stimulated isometric torque at that time point. Across bouts there was no difference in the immediate loss of strength after repeated bouts of eccentric contractions for mdx mice (−70%, P = 0.68). However, after recovery from each bout, dystrophic muscle had greater torque-generating capacity such that isometric torque was increased ∼38% for both anterior and posterior crural muscles at bout 5 compared with bout 1 (P < 0.001). Moreover, isolated extensor digitorum longus muscles excised from in vivo-tested hindlimbs 14–18 days after bout 5 had greater specific force than contralateral control muscles (12.2 vs. 10.4 N/cm2, P = 0.005) and a 20% greater maximal relaxation rate (P = 0.049). Additional adaptations due to the multiple bouts of eccentric contractions included rapid recovery and/or sparing of contractile proteins, enhanced parvalbumin expression, and a decrease in fiber size variability. In conclusion, eccentric contractions are injurious to dystrophic skeletal muscle; however, the muscle recovers function rapidly and adapts to repeated bouts of eccentric contractions by improving strength. PMID:21960659

  4. Relationship between isometric contraction intensity and muscle hardness assessed by ultrasound strain elastography.

    PubMed

    Inami, Takayuki; Tsujimura, Toru; Shimizu, Takuya; Watanabe, Takemasa; Lau, Wing Yin; Nosaka, Kazunori

    2017-05-01

    Ultrasound elastography is used to assess muscle hardness or stiffness; however, no previous studies have validated muscle hardness measures using ultrasound strain elastography (SE). This study investigated the relationship between plantar flexor isometric contraction intensity and gastrocnemius hardness assessed by SE. We hypothesised that the muscle would become harder linearly with an increase in the contraction intensity of the plantar flexors. Fifteen young women (20.1 ± 0.8 years) performed isometric contractions of the ankle plantar flexors at four different intensities (25, 50, 75, 100% of maximal voluntary contraction force: MVC) at 0° plantar flexion. Using SE images, the strain ratio (SR) between the muscle and an acoustic coupler (elastic modulus 22.6 kPa) placed over the skin was calculated (muscle/coupler); pennation angle and muscle thickness were measured for the resting and contracting conditions. SR decreased with increasing contraction intensity from rest (1.28 ± 0.20) to 25% (0.99 ± 0.21), 50% (0.61 ± 0.15), 75% (0.34 ± 0.1) and 100% MVC (0.20 ± 0.05). SR decreased linearly (P < 0.05) with increasing MVC from rest to 75% MVC, but levelled off from 75 and 100% MVC. SR was negatively correlated with pennation angle (r = -0.80, P < 0.01) and muscle thickness ( r= -0.78,  P< 0.01). SR appears to represent muscle hardness changes in response to contraction intensity changes, in the assumption that the gastrocnemius muscle contraction intensity is proportional to the plantar flexion intensity. We concluded that gastrocnemius muscle hardness changes could be validly assessed by SR, and the force-hardness relationship was not linear.

  5. Comparative studies on troponin, a Ca²⁺-dependent regulator of muscle contraction, in striated and smooth muscles of protochordates.

    PubMed

    Obinata, Takashi; Sato, Naruki

    2012-01-01

    Troponin is well known as a Ca(2+)-dependent regulator of striated muscle contraction and it has been generally accepted that troponin functions as an inhibitor of muscle contraction or actin-myosin interaction at low Ca(2+) concentrations, and Ca(2+) at higher concentrations removes the inhibitory action of troponin. Recently, however, troponin became detectable in non-striated muscles of several invertebrates and in addition, unique troponin that functions as a Ca(2+)-dependent activator of muscle contraction has been detected in protochordate animals, although troponin in vertebrate striated muscle is known as an inhibitor of the contraction in the absence of a Ca(2+). Further studies on troponin in invertebrate muscle, especially in non-striated muscle, would provide new insight into the evolution of regulatory systems for muscle contraction and diverse function of troponin and related proteins. The methodology used for preparation and characterization of functional properties of protochordate striated and smooth muscles will be helpful for further studies of troponin in other invertebrate animals. Copyright © 2011. Published by Elsevier Inc.

  6. Low-Grade Myxofibrosarcoma of the Rectus Abdominus Muscle Infiltrating into Abdominal Cavity: A Case Report.

    PubMed

    Nomura, Tadashi; Sakakibara, Shunsuke; Moriwaki, Aya; Kawamoto, Teruya; Suzuki, Satoshi; Ishimura, Takeshi; Hashikawa, Kazunobu; Terashi, Hiroto

    2017-01-01

    Objective: Myxofibrosarcoma (MFS) is a relatively rare tumor that is histologically characterized by myxoid stroma and spindle cell proliferation. This tumor most commonly arises as a slow growing, enlarging painless mass in the extremities of elderly patients. Methods: We report a case of a primary, low-grade MFS in the rectus abdominis muscle infiltrating the abdominal cavity of a 75-year-old man. Results: The patient underwent a wide excision of the right abdominal wall mass with a 3-cm surgical margin from the scar due to a biopsy. The tumor infiltrated the urinary bladder, peritoneum, and external iliac vessels. Twenty-six months after the initial operation, he had recurrences in his abdominal wall, urinary bladder, and right iliac vessels. Conclusions: To our knowledge, primary MFS of the muscle in the abdomen has not been documented previously. Although this case was histopathologically classified as a low-grade tumor, it infiltrated the abdominal cavity. The tumor is suspected to have penetrated the abdominal cavity below the linea arcuata, which lacks the posterior sheath of the rectus abdominis muscle; from there, it could easily spread without being blocked by any biological barriers.

  7. [Excitation-contraction coupling in skeletal muscle: questions remaining after 50 years of research].

    PubMed

    Calderón-Vélez, Juan Camilo; Figueroa-Gordon, Lourdes Carolina

    2009-03-01

    The excitation-contraction coupling mechanism was defined as the entire sequence of reactions linking excitation of plasma membrane to activation of contraction in skeletal muscle. By using different techniques, their regulation and interactions have been studied during the last 50 years, defining until now the importance and origin of the calcium ion as a contractile activator and the main proteins involved in the whole mechanism. Furthermore, the study of the ultrastructural basis and pharmacological regulation of the excitation-contraction coupling phenomenon has begun. The excitation-contraction coupling is thought to be altered in situations as ageing, muscle fatigue and some muscle diseases. However, many questions remain to be answered. For example, (1) How excitation-contraction coupling develops and ages? (2) What role does it play in muscle fatigue and other diseases? (3) What is the nature of the interaction between the proteins believed to be involved? The present review describes excitation-contraction coupling in skeletal muscle and techniques used to better understand it as an introduction for discussing unanswered questions regarding excitation-contraction coupling.

  8. Metabolic adaptations to repeated periods of contraction with reduced blood flow in canine skeletal muscle

    PubMed Central

    MacInnes, Alan; Timmons, James A

    2005-01-01

    Background Patients suffering from Intermittent Claudication (IC) experience repeated periods of muscle contraction with low blood flow, throughout the day and this may contribute to the hypothesised skeletal muscle abnormalities. However, no study has evaluated the consequences of intermittent contraction with low blood flow on skeletal muscle tissue. Our aim was to generate this basic physiological data, determining the 'normal' response of healthy skeletal muscle tissue. We specifically proposed that the metabolic responses to contraction would be modified under such circumstances, revealing endogenous strategies engaged to protect the muscle adenine nucleotide pool. Utilizing a canine gracilis model (n = 9), the muscle was stimulated to contract (5 Hz) for three 10 min periods (separated by 10 min rest) under low blood flow conditions (80% reduced), followed by 1 hr recovery and then a fourth period of 10 min stimulation. Muscle biopsies were obtained prior to and following the first and fourth contraction periods. Direct arterio-venous sampling allowed for the calculation of muscle metabolite efflux and oxygen consumption. Results During the first period of contraction, [ATP] was reduced by ~30%. During this period there was also a 10 fold increase in muscle lactate concentration and a substantial increase in muscle lactate and ammonia efflux. Subsequently, lactate efflux was similar during the first three periods, while ammonia efflux was reduced by the third period. Following 1 hr recovery, muscle lactate and phosphocreatine concentrations had returned to resting values, while muscle [ATP] remained 20% lower. During the fourth contraction period no ammonia efflux or change in muscle ATP content occured. Despite such contrasting metabolic responses, muscle tension and oxygen consumption were identical during all contraction periods from 3 to 10 min. Conclusion repeated periods of muscle contraction, with low blood flow, results in cessation of muscle ammonia

  9. Compensatory strategies during walking in response to excessive muscle co-contraction at the ankle joint.

    PubMed

    Wang, Ruoli; Gutierrez-Farewik, Elena M

    2014-03-01

    Excessive co-contraction causes inefficient or abnormal movement in several neuromuscular pathologies. How synergistic muscles spanning the ankle, knee and hip adapt to co-contraction of ankle muscles is not well understood. This study aimed to identify the compensation strategies required to retain normal walking with excessive antagonistic ankle muscle co-contraction. Muscle-actuated simulations of normal walking were performed to quantify compensatory mechanisms of ankle and knee muscles during stance in the presence of normal, medium and high levels of co-contraction of antagonistic pairs gastrocnemius+tibialis anterior and soleus+tibialis anterior. The study showed that if co-contraction increases, the synergistic ankle muscles can compensate; with gastrocmemius+tibialis anterior co-contraction, the soleus will increase its contribution to ankle plantarflexion acceleration. At the knee, however, almost all muscles spanning the knee and hip are involved in compensation. We also found that ankle and knee muscles alone can provide sufficient compensation at the ankle joint, but hip muscles must be involved to generate sufficient knee moment. Our findings imply that subjects with a rather high level of dorsiflexor+plantarflexor co-contraction can still perform normal walking. This also suggests that capacity of other lower limb muscles to compensate is important to retain normal walking in co-contracted persons. The compensatory mechanisms can be useful in clinical interpretation of motion analyses, when secondary muscle co-contraction or other deficits may present simultaneously in subjects with motion disorders. Copyright © 2014 Elsevier B.V. All rights reserved.

  10. Effect of muscle relaxation in the foot on simultaneous muscle contraction in the contralateral hand.

    PubMed

    Kato, Kouki; Kanosue, Kazuyuki

    2016-10-28

    We investigated the effects of foot muscle relaxation and contraction on muscle activities in the hand on both ipsilateral and contralateral sides. The subjects sat in an armchair with hands in the pronated position. They were able to freely move their right/left hand and foot. They performed three tasks for both ipsilateral (right hand and right foot) and contralateral limb coordination (left hand and right foot for a total of six tasks). These tasks involved: (1) wrist extension from a flexed (resting) position, (2) wrist extension with simultaneous ankle dorsiflexion from a plantarflexed (resting) position, and (3) wrist extension with simultaneous ankle relaxation from a dorsiflexed position. The subjects performed each task as fast as possible after hearing the start signal. Reaction time for the wrist extensor contraction (i.e. the degree to which it preceded the motor reaction time), as observed in electromyography (EMG), became longer when it was concurrently done with relaxation of the ankle dorsiflexor. Also, the magnitude of EMG activity became smaller, as compared with activity when wrist extensor contraction was done alone or with contraction of the ankle dorsiflexor. These effects were observed not only for the ipsilateral hand, but also for the contralateral hand. Our findings suggest that muscle relaxation in one limb interferes with muscle contraction in both the ipsilateral and contralateral limbs. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  11. Ultrasound Assessment of Abdominal Muscle Thickness in Women With and Without Low Back Pain During Pregnancy.

    PubMed

    Weis, Carol Ann; Nash, Jennifer; Triano, John J; Barrett, Jon

    2017-05-01

    The aim of this preliminary study was to determine the differences in abdominal musculature thickness, within 1 month of delivery, in women who experienced back pain during pregnancy compared with those who did not. B-mode ultrasound imaging was used to measure abdominal muscle thickness on 76 postpartum participants who participated in a larger study; 47 women experienced back pain during pregnancy, and 29 did not. Participant data were stratified by group, and primary comparisons were based on these grouping across the abdominal muscles, including rectus abdominis (upper and lower fibers), external oblique, internal oblique, and transversus abdominis. Means and standard deviations were also used to set parameters for future studies. In the present study, there was no difference in any abdominal muscle thickness between groups. Women with low back pain were significantly shorter (165.19 ± 6.64 cm) than women who did not have from back pain during pregnancy (169.38 ± 7.58 cm). All other demographics, such as age, weight, and date tested postpartum, were not significantly different between groups. The results of this study showed no variation in abdominal muscle thickness in women who had back pain during pregnancy and those who did not. Copyright © 2017. Published by Elsevier Inc.

  12. Reconstruction with latissimus dorsi, external abdominal oblique and cranial sartorius muscle flaps for a large defect of abdominal wall in a dog after surgical removal of infiltrative lipoma

    PubMed Central

    FENG, Yu-Ching; CHEN, Kuan-Sheng; CHANG, Shih-Chieh

    2016-01-01

    This animal was presented with a large-sized infiltrative lipoma in the abdominal wall that had been noted for 4 years. This lipoma was confirmed by histological examination from a previous biopsy, and the infiltrative features were identified by a computerized tomography scan. The surgical removal created a large-sized abdominal defect that was closed by a combination of latissimus dorsi and external abdominal oblique muscle flaps in a pedicle pattern. A small dehiscence at the most distal end of the muscle flap resulted in a small-sized abdominal hernia and was repaired with cranial sartorius muscle flap 14 days after surgery. The dog was in good general health with no signs of tumor recurrence after 18 months of follow-up. PMID:27476526

  13. Development of new muscle contraction sensor to replace sEMG for using in muscles analysis fields.

    PubMed

    Zhang, D; Matsuoka, Y; Kong, W; Imtiaz, U; Bartolomeo, L; Cosentino, S; Zecca, M; Sessa, S; Ishii, H; Takanishi, A

    2014-01-01

    Nowadays, the technologies for detecting, processing and interpreting bioelectrical signals have improved tremendously. In particular, surface electromyography (sEMG) has gained momentum in a wide range of applications in various fields. However, sEMG sensing has several shortcomings, the most important being: measurements are heavily sensible to individual differences, sensors are difficult to position and very expensive. In this paper, the authors will present an innovative muscle contraction sensing device (MC sensor), aiming to replace sEMG sensing in the field of muscle movement analysis. Compared with sEMG, this sensor is easier to position, setup and use, less dependent from individual differences, and less expensive. Preliminary experiments, described in this paper, confirm that MC sensing is suitable for muscle contraction analysis, and compare the results of sEMG and MC sensor for the measurement of forearm muscle contraction.

  14. Forearm Muscle Oxygenation Decreases During Low Levels of Brief, Isometric Contraction

    NASA Technical Reports Server (NTRS)

    Murthy Gita; Kahan, N. J.; Hargens, Alan R.; Rempel, D. M.; Hargens, Murthy G. (Technical Monitor)

    1997-01-01

    Regional muscle pain syndromes can be caused by repeated and sustained exertion of a specific muscle. Such exertion may elevate local tissue fluid pressure, reduce blood flow and tissue oxygenation (TO2), and cause fatigue, pain and functional deficits of the Involved muscle. Low levels (less than 20% maximum voluntary contraction (MVC)) of prolonged static contraction of the upper extremity are common In many occupational settings and May cause fatigue. The purpose of our Investigation was to determine whether TO2 decreases significantly at low levels of static contraction of the extensor carpi radialis brevis (ECRB).

  15. [Thin filament elasticity and its role in the muscle contraction].

    PubMed

    Skubiszak, L

    2006-01-01

    The available experimental methods do not allow one to establish unambiguously the molecular structural events during muscle contraction. To resolve the existing controversies, I have devised an unconventional original computer program. The new approach allows the reconstruction of the hexagonal lattice of the sarcomere for different muscle states and verification of the structure by comparison of the calculated Fourier spectra with the real diffraction patterns. Previously, by the use of this approach, the real structure of a myosin filament from vertebrate striated muscle has been reconstructed (http://zope.ibib.waw.pl/pspk). In this work, a reconstruction for the thin filament is presented for three states: relaxed, after activation, and during contraction. Good consistency of the calculated Fourier spectra with the real diffraction patterns available in the literature suggests that the thin filament, due to flexibility, plays an active part in muscle contraction, as myosin cross-bridges do.

  16. Repetitive muscle compression reduces vascular mechano-sensitivity and the hyperemic response to muscle contraction.

    PubMed

    Messere, A; Turturici, M; Millo, G; Roatta, S

    2017-06-01

    Animal studies have shown that the rapid hyperemic response to external muscle compression undergoes inactivation upon repetitive stimulation, but this phenomenon has never been observed in humans. The aim of the present study was to determine whether 1) the vascular mechano-sensitivity underlying muscle compression-induced hyperemia is inactivated in an inter-stimulus interval (ISI)-dependent fashion upon repetitive stimulation, as suggested by animal studies, and 2) whether such inactivation also attenuates contraction-induced hyperemia. Brachial artery blood flow was measured by echo Doppler sonography in 13 healthy adults in response to 1) single and repetitive cuff muscle compression (CMC) of the forearm (20 CMCs, 1 s ISI); 2) a sequence of CMC delivered at decreasing ISI from 120 to 2 s; and 3) electrically-stimulated contraction of the forearm muscles before and after repetitive CMC. The peak amplitude of hyperemia in response to CMC normalized to baseline decreased from 2.2 ± 0.6 to 1.4 ± 0.4 after repetitive CMC and, in general, was decreased at ISI < 240 s. The peak amplitude of contraction-induced hyperemia was attenuated after as compared to before repeated CMC (1.7 ± 0.4 and 2.6 ± 0.6, respectively). Mechano-sensitivity of the vascular network can be conditioned by previous mechanical stimulation, and such preconditioning may substantially decrease contraction-induced hyperemia.

  17. Energetics of muscle contraction: further trials.

    PubMed

    Yamada, Kazuhiro

    2017-01-01

    Knowledge accumulated in the field of energetics of muscle contraction has been reviewed in this article. Active muscle converts chemical energy into heat and work. Therefore, measurements of heat production and mechanical work provide the framework for understanding the process of energy conversion in contraction. In the 1970s, precise comparison between energy output and the associated chemical reactions was performed. It has been found that the two do not match in several situations, resulting in an energy balance discrepancy. More recently, efforts in resolving these discrepancies in the energy balance have been made involving chemical analysis, phosphorus nuclear magnetic resonance spectroscopy, and microcalorimetry. Through reviewing the evidence from these studies, the energy balance discrepancy developed early during isometric contraction has become well understood on a quantitative basis. In this situation energy balance is established when we take into account the binding of Ca to sarcoplasmic proteins such as troponin and parvalbumin, and also the shift of cross-bridge states. On the other hand, the energy balance discrepancy observed during rapid shortening still remains to be clarified. The problem may be related to the essential mechanism of cross-bridge action.

  18. Agonist muscle adaptation accompanied by antagonist muscle atrophy in the hindlimb of mice following stretch-shortening contraction training.

    PubMed

    Rader, Erik P; Naimo, Marshall A; Ensey, James; Baker, Brent A

    2017-02-02

    The vast majority of dynamometer-based animal models for investigation of the response to chronic muscle contraction exposure has been limited to analysis of isometric, lengthening, or shortening contractions in isolation. An exception to this has been the utilization of a rat model to study stretch-shortening contractions (SSCs), a sequence of consecutive isometric, lengthening, and shortening contractions common during daily activity and resistance-type exercise. However, the availability of diverse genetic strains of rats is limited. Therefore, the purpose of the present study was to develop a dynamometer-based SSC training protocol to induce increased muscle mass and performance in plantarflexor muscles of mice. Young (3 months old) C57BL/6 mice were subjected to 1 month of plantarflexion SSC training. Hindlimb muscles were analyzed for muscle mass, quantitative morphology, myogenesis/myopathy relevant gene expression, and fiber type distribution. The main aim of the research was achieved when training induced a 2-fold increase in plantarflexion peak torque output and a 19% increase in muscle mass for the agonist plantaris (PLT) muscle. In establishing this model, several outcomes emerged which raised the value of the model past that of being a mere recapitulation of the rat model. An increase in the number of muscle fibers per transverse muscle section accounted for the PLT muscle mass gain while the antagonist tibialis anterior (TA) muscle atrophied by 30% with preferential atrophy of type IIb and IIx fibers. These alterations were accompanied by distinct gene expression profiles. The findings confirm the development of a stretch-shortening contraction training model for the PLT muscle of mice and demonstrate that increased cross-sectional fiber number can occur following high-intensity SSC training. Furthermore, the TA muscle atrophy provides direct evidence for the concept of muscle imbalance in phasic non-weight bearing muscles, a concept largely

  19. Breathing-synchronised electrical stimulation of the abdominal muscles in patients with acute tetraplegia: A prospective proof-of-concept study.

    PubMed

    Liebscher, Thomas; Schauer, Thomas; Stephan, Ralph; Prilipp, Erik; Niedeggen, Andreas; Ekkernkamp, Axel; Seidl, Rainer O

    2016-11-01

    To examine whether, by enhancing breathing depth and expectoration, early use of breathing-synchronised electrical stimulation of the abdominal muscles (abdominal functional electrical stimulation, AFES) is able to reduce pulmonary complications during the acute phase of tetraplegia. Prospective proof-of-concept study. Spinal cord unit at a level 1 trauma center. Following cardiovascular stabilisation, in addition to standard treatments, patients with acute traumatic tetraplegia (ASIA Impairment Scale A or B) underwent breathing-synchronised electrical stimulation of the abdominal muscles to aid expiration and expectoration. The treatment was delivered in 30-minute sessions, twice a day for 90 days. The target was for nine of 15 patients to remain free of pneumonia meeting Centers for Disease Control and Prevention (CDC) diagnostic criteria. Eleven patients were recruited to the study between October 2011 and November 2012. Two patients left the study before completion. None of the patients contracted pneumonia during the study period. No complications from electrical stimulation were observed. AFES led to a statistically significant increase in peak inspiratory and expiratory flows and a non-statistically significant increase in tidal volume and inspiratory and expiratory flow. When surveyed, 6 out of 9 patients (67%) reported that the stimulation procedure led to a significant improvement in breathing and coughing. AFES appears to be able to improve breathing and expectoration and prevent pneumonia in the acute phase of tetraplegia (up to 90 days post-trauma). This result is being validated in a prospective multicentre comparative study.

  20. Titanium Dioxide Modulation of the Contractibility of Visceral Smooth Muscles In Vivo

    NASA Astrophysics Data System (ADS)

    Tsymbalyuk, Olga V.; Naumenko, Anna M.; Rohovtsov, Oleksandr O.; Skoryk, Mykola A.; Voiteshenko, Ivan S.; Skryshevsky, Valeriy A.; Davydovska, Tamara L.

    2017-02-01

    Electronic scanning microscopy was used in the work to obtain the image and to identify the sizes of titanium dioxide (TiO2) nanoparticles 21 ± 5 nm. The qualitative and quantitative elemental analysis of the preparations of the caecum, antrum, myometrium, kidneys, and lungs of the rats, burdened with titanium dioxide, was also performed. It was established using the tenzometric method in the isometric mode that the accumulation of titanium dioxide in smooth muscles of the caecum resulted in the considerable, compared to the control, increase in the frequency of their spontaneous contractions, the decrease in the duration of the contraction-relaxation cycle, and the decrease in the indices of muscle functioning efficiency (the index of contractions in Montevideo units (MU) and the index of contractions in Alexandria units (AU)). In the same experimental conditions, there was not the increase, but the decrease in the frequency of spontaneous contractions, the duration of the contraction-relaxation cycle, and the increase in MU and AU indices in the smooth muscles of myometrium (in the group of rats, burdened with TiO2 for 30 days). It was also determined that TiO2 modulates both the mechanisms of the input of extracellular Ca2+ ions and the mechanisms of decreasing the concentration of these cations in smooth muscle cells of the caecum during the generation of the high potassium contraction. In these conditions, there is a considerable increase in the normalized maximal velocity of the contraction phase and the relaxation phase. It was demonstrated in the work that titanium dioxide also changes the cholinergic excitation in these muscles. The impact of titanium dioxide in the group of rats, burdened with TiO2, was accompanied with a considerable impairment of the kinetics of forming the tonic component of the oxytocin-induced contraction of the smooth muscles of myometrium.

  1. Electrical and Mechanical Responses in Deep Abdominal Extensor Muscles of Crayfish and Lobster

    PubMed Central

    Abbott, Bernard C.; Parnas, I.

    1965-01-01

    Electrical and mechanical studies have been made of the deep abdominal extensor muscles, medial (DEAM) and lateral (DEAL), of crayfish and lobster. The medial muscle responds to direct (intracellular) and indirect stimulation with a transient membrane depolarization which exhibits the properties of a propagated non-decremental action potential but does not overshoot the zero level. The amplitude is about 30 mv in crayfish and 50 mv in lobster. It is followed by a fast all-or-none twitch whose duration at 20°C is 30 to 50 msec. and whose developed tension is 500 gm/cm2 or about half the tetanic value. Membrane potential is K+-dependent and immersion in high K+ induces a brief transient tension rise as in other twitch-type muscles. The action potential and twitch are normal even if all external Na+ is replaced with sucrose but vary with external Ca++, the action potential increasing 8 to 10 mv for a twofold increase in Ca++. The lateral muscle (DEAL) is much slower and responds to intracellular stimulation only with an electrotonic or a local response. Mechanical responses and relaxation speeds are slow with minimal duration of contraction of 0.5 to 2 seconds. Immersion in high K solutions induces large maintained tensions. Sarcomere length in the fast DEAM is uniform and about 2 µ at rest, but in the DEAL speed is less and sarcomere length is greater averaging about 4.5 µ but with a mixed population of fibers. PMID:14324996

  2. Inflammatory cells in rat skeletal muscle are elevated after electrically stimulated contractions.

    PubMed

    McLoughlin, Thomas J; Mylona, Eleni; Hornberger, Troy A; Esser, Karyn A; Pizza, Francis X

    2003-03-01

    We determined the effect of muscle contractions resulting from high-frequency electrical stimulation (HFES) on inflammatory cells in rat tibialis anterior (TA), plantaris (Pln), and soleus (Sol) muscles at 6, 24, and 72 h post-HFES. A minimum of four and a maximum of seven rats were analyzed at each time point. HFES, applied to the sciatic nerve, caused the Sol and Pln to contract concentrically and the TA to contract eccentrically. Neutrophils were higher (P < 0.05) at 6 and 24 h after HFES in the Sol, Pln, and TA muscles relative to control muscles. ED1(+) macrophages in the Pln were elevated at 6 and 24 h after HFES and were also elevated in the Sol and TA after HFES relative to controls. ED2(+) macrophages in the Sol and TA were elevated at 24 and 72 h after HFES, respectively, and were also elevated in the Pln after HFES relative to controls. In contrast to the TA muscles, the Pln and Sol muscles showed no gross histological abnormalities. Collectively, these data indicate that both eccentric and concentric contractions can increase inflammatory cells in muscle, regardless of whether overt histological signs of injury are apparent.

  3. Mechanisms of postprandial abdominal bloating and distension in functional dyspepsia.

    PubMed

    Burri, Emanuel; Barba, Elizabeth; Huaman, Jose Walter; Cisternas, Daniel; Accarino, Anna; Soldevilla, Alfredo; Malagelada, Juan-R; Azpiroz, Fernando

    2014-03-01

    Patients with irritable bowel syndrome and abdominal bloating exhibit abnormal responses of the abdominal wall to colonic gas loads. We hypothesised that in patients with postprandial bloating, ingestion of a meal triggers comparable abdominal wall dyssynergia. Our aim was to characterise abdominal accommodation to a meal in patients with postprandial bloating. A test meal (0.8 kcal/ml nutrients plus 27 g/litre polyethylenglycol 4000) was administered at 50 ml/min as long as tolerated in 10 patients with postprandial bloating (fulfilling Rome III criteria for postprandial distress syndrome) and 12 healthy subjects, while electromyographic (EMG) responses of the anterior wall (upper and lower rectus, external and internal oblique via bipolar surface electrodes) and the diaphragm (via six ring electrodes over an oesophageal tube in the hiatus) were measured. Means +/- SD were calculated. Healthy subjects tolerated a meal volume of 913±308 ml; normal abdominal wall accommodation to the meal consisted of diaphragmatic relaxation (EMG activity decreased by 15±6%) and a compensatory contraction (25±9% increase) of the upper abdominal wall muscles (upper rectus and external oblique), with no changes in the lower anterior muscles (lower rectus and internal oblique). Patients tolerated lower volume loads (604±310 ml; p=0.030 vs healthy subjects) and developed a paradoxical response, that is, diaphragmatic contraction (14±3% EMG increment; p<0.01 vs healthy subjects) and upper anterior wall relaxation (9±4% inhibition; p<0.01 vs healthy subjects). In functional dyspepsia, postprandial abdominal distension is produced by an abnormal viscerosomatic response to meal ingestion that alters normal abdominal accommodation.

  4. Regulation of phosphorylase kinase by low concentrations of Ca ions upon muscle contraction: the connection between metabolism and muscle contraction and the connection between muscle physiology and Ca-dependent signal transduction.

    PubMed

    Ozawa, Eijiro

    2011-01-01

    It had long been one of the crucial questions in muscle physiology how glycogenolysis is regulated in connection with muscle contraction, when we found the answer to this question in the last half of the 1960s. By that time, the two principal currents of muscle physiology, namely, the metabolic flow starting from glycogen and the mechanisms of muscle contraction, had already been clarified at the molecular level thanks to our senior researchers. Thus, the final question we had to answer was how to connect these two currents. We found that low concentrations of Ca ions (10(-7)-10(-4) M) released from the sarcoplasmic reticulum for the regulation of muscle contraction simultaneously reversibly activate phosphorylase kinase, the enzyme regulating glycogenolysis. Moreover, we found that adenosine 3',5'-monophosphate (cyclic AMP), which is already known to activate muscle phosphorylase kinase, is not effective in the absence of such concentrations of Ca ions. Thus, cyclic AMP is not effective by itself alone and only modifies the activation process in the presence of Ca ions (at that time, cyclic AMP-dependent protein kinase had not yet been identified). After a while, it turned out that our works have not only provided the solution to the above problem on muscle physiology, but have also been considered as the first report of Ca-dependent protein phosphorylation, which is one of the central problems in current cell biology. Phosphorylase kinase is the first protein kinase to phosphorylate a protein resulting in the change in the function of the phosphorylated protein, as shown by Krebs and Fischer. Our works further showed that this protein kinase is regulated in a Ca-dependent manner. Accordingly, our works introduced the concept of low concentrations of Ca ions, which were first identified as the regulatory substance of muscle contraction, to the vast field of Ca biology including signal transduction.

  5. Reliability of ultrasound thickness measurement of the abdominal muscles during clinical isometric endurance tests.

    PubMed

    ShahAli, Shabnam; Arab, Amir Massoud; Talebian, Saeed; Ebrahimi, Esmaeil; Bahmani, Andia; Karimi, Noureddin; Nabavi, Hoda

    2015-07-01

    The study was designed to evaluate the intra-examiner reliability of ultrasound (US) thickness measurement of abdominal muscles activity when supine lying and during two isometric endurance tests in subjects with and without Low back pain (LBP). A total of 19 women (9 with LBP, 10 without LBP) participated in the study. Within-day reliability of the US thickness measurements at supine lying and the two isometric endurance tests were assessed in all subjects. The intra-class correlation coefficient (ICC) was used to assess the relative reliability of thickness measurement. The standard error of measurement (SEM), minimal detectable change (MDC) and the coefficient of variation (CV) were used to evaluate the absolute reliability. Results indicated high ICC scores (0.73-0.99) and also small SEM and MDC scores for within-day reliability assessment. The Bland-Altman plots of agreement in US measurement of the abdominal muscles during the two isometric endurance tests demonstrated that 95% of the observations fall between the limits of agreement for test and retest measurements. Together the results indicate high intra-tester reliability for the US measurement of the thickness of abdominal muscles in all the positions tested. According to the study's findings, US imaging can be used as a reliable method for assessment of abdominal muscles activity in supine lying and the two isometric endurance tests employed, in participants with and without LBP. Copyright © 2014 Elsevier Ltd. All rights reserved.

  6. Prediction of maximal surface electromyographically based voluntary contractions of erector spinae muscles from sonographic measurements during isometric contractions.

    PubMed

    Cuesta-Vargas, Antonio I; González-Sánchez, Manuel

    2014-03-01

    Currently, there are no studies combining electromyography (EMG) and sonography to estimate the absolute and relative strength values of erector spinae (ES) muscles in healthy individuals. The purpose of this study was to establish whether the maximum voluntary contraction (MVC) of the ES during isometric contractions could be predicted from the changes in surface EMG as well as in fiber pennation and thickness as measured by sonography. Thirty healthy adults performed 3 isometric extensions at 45° from the vertical to calculate the MVC force. Contractions at 33% and 100% of the MVC force were then used during sonographic and EMG recordings. These measurements were used to observe the architecture and function of the muscles during contraction. Statistical analysis was performed using bivariate regression and regression equations. The slope for each regression equation was statistically significant (P < .001) with R(2) values of 0.837 and 0.986 for the right and left ES, respectively. The standard error estimate between the sonographic measurements and the regression-estimated pennation angles for the right and left ES were 0.10 and 0.02, respectively. Erector spinae muscle activation can be predicted from the changes in fiber pennation during isometric contractions at 33% and 100% of the MVC force. These findings could be essential for developing a regression equation that could estimate the level of muscle activation from changes in the muscle architecture.

  7. Associations of Abdominal Muscle Area with 4-Year Change in Coronary Artery Calcium Differ by Ethnicity Among Post-Menopausal Women.

    PubMed

    Wassel, Christina L; Laughlin, Gail A; Saad, Sarah D; Araneta, Maria Rosario G; Wooten, Wilma; Barrett-Connor, Elizabeth; Allison, Matthew A

    2015-11-05

    To examine the association of abdominal muscle area with coronary artery calcium (CAC) presence, extent, and progression in a multi-ethnic cohort of older, community-dwelling post-menopausal women. Cross-sectional and longitudinal population-based cohort. The sample comprised 179 non-Hispanic White women, 116 Filipina women and 144 African American women, all without known CVD, who underwent chest and abdominal computed tomography (CT) scans twice about four years apart for abdominal muscle and fat, as well as CAC. CAC presence, extent and progression. There was a significant interaction of ethnicity with baseline oblique muscle area (p-for-interaction .01), and marginally significant interactions with baseline total and paraspinal muscle for change in CAC (p-for-interactions both .09). Among Filipina women, each standard deviation (SD) greater total muscle area was associated with a 26% (95% CI (-43%, -4%), P=.02) reduced rate of change in CAC; higher paraspinal and oblique muscle area were associated with a 24% (-38%, -6%, P=.01) and a 37% (-53%, -16%, P=.0002) reduced rate of change in CAC, respectively. These associations were not significant in African American or non-Hispanic White women. There were no significant associations of abdominal muscle with CAC presence or extent, nor were there significant ethnicity by muscle interactions in these models. Among Filipina women, greater abdominal muscle mass is associated with a decreased rate of CAC progression. Higher muscle mass may be important for this group in reducing CVD outcomes.

  8. Contraction-free, fume-fixed longitudinal sections of fresh frozen muscle

    NASA Technical Reports Server (NTRS)

    Riley, Danny A.; Slocum, Glenn R.

    1988-01-01

    Contraction damage occurring when longitudinal frozen sections of fresh unfixed muscles are thawed on microscope slides has limited histological examination of this tissue mainly to cross sections. Longitudinally oriented sections are advantageous for investigating properties that vary along the length of the muscle fibers. A fume fixation technique has been developed for preventing contraction of thick longitudinal frozen sections. The technique is compatible with histochemical staining of enzymes.

  9. Comparison of contraction times of a muscle and its motor units

    NASA Technical Reports Server (NTRS)

    Eldred, E.; Smith, L.; Edgerton, V. R.

    1992-01-01

    The twitch contraction time (CT) for each of 13 soleus (SOL) and 13 medial gastrocnemius (MG) muscles was compared with the mean CT from a sample of its motor units (MUs; 356 total) to see if the CT of a whole muscle when tested at its optimal length (Lo) differed systematically from that of its MUs tested at their individual Lo's. The CTs of the whole muscle were significantly longer in the ratio of 1.13. This is consistent with a hypothesis that electrical-field effects result in a more protracted contraction of the individual muscle fiber.

  10. Changes in multifidus and abdominal muscle size in response to microgravity: possible implications for low back pain research.

    PubMed

    Hides, J A; Lambrecht, G; Stanton, W R; Damann, V

    2016-05-01

    In microgravity, muscle atrophy occurs in the intrinsic muscles of the spine, with changes also observed in the abdominal muscles. Exercises are undertaken on the International Space Station and on Earth following space flight to remediate these effects. Similar effects have been seen on Earth in prolonged bed rest studies and in people with low back pain (LBP). The aim of this case report was to examine the effects of microgravity, exercise in microgravity and post-flight rehabilitation on the size of the multifidus and antero-lateral abdominal muscles. Ultrasound imaging was used to assess size of the multifidus, transversus abdominis and internal oblique muscles at four time points: pre-flight and after daily rehabilitation on day one (R + 1), day 8 (R + 8) and day 14 (R + 14) after return to Earth (following 6 months in microgravity). Exercises in microgravity maintained multifidus size at L2-L4, however, after spaceflight, size of the multifidus muscle at L5 was reduced, size of the internal oblique muscle was increased and size of transversus abdominis was reduced. Rehabilitation post-space flight resulted in hypertrophy of the multifidus muscle to pre-mission size at the L5 vertebral level and restoration of antero-lateral abdominal muscle size. Exercise in space can prevent loss of spinal intrinsic muscle size. For the multifidus muscles, effectiveness varied at different levels of the spine. Post-mission rehabilitation targeting specific motor control restored muscle balance between the antero-lateral abdominal and multifidus muscles, similar to results from intervention trials for people with LBP. A limitation of the current investigation is that only one astronaut was studied, however, the microgravity model could be valuable as predictable effects on trunk muscles can be induced and interventions evaluated. Level of Evidence Case series.

  11. The effects of trunk extensor and abdominal muscle fatigue on postural control and trunk proprioception in young, healthy individuals.

    PubMed

    Larson, Dennis J; Brown, Stephen H M

    2018-02-01

    The purpose of this study was to induce both trunk extensor and abdominal muscle fatigue, on separate occasions, and compare their effects on standing postural control and trunk proprioception, as well as look at the effects of a recovery period on these outcome measures. A total of 20 individuals participated, with 10 (5 males and 5 females) completing either a standing postural control or lumbar axial repositioning protocol. Participants completed their randomly assigned protocol on two occasions, separated by at least 4  days, with either their trunk extensor or abdominal muscles being fatigued on either day. Postural control centre of pressure variables and trunk proprioception errors were compared pre- and post-fatigue. Results showed that both trunk extensor and abdominal muscle fatigue significantly degraded standing postural control immediately post-fatigue, with recovery occurring within 2 min post-fatigue. In general, these degradative effects on postural control appeared to be greater when the trunk extensor muscles were fatigued compared to the abdominal muscles. No statistically significant changes in trunk proprioception were found after either fatigue protocol. The present findings demonstrate our body's ability to quickly adapt and reweight somatosensory information to maintain postural control and trunk proprioception, as well as illustrate the importance of considering the abdominal muscles, along with the trunk extensor muscles, when considering the impact of fatigue on trunk movement and postural control. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Myosin Light Chain Kinase Is Necessary for Tonic Airway Smooth Muscle Contraction*

    PubMed Central

    Zhang, Wen-Cheng; Peng, Ya-Jing; Zhang, Gen-Sheng; He, Wei-Qi; Qiao, Yan-Ning; Dong, Ying-Ying; Gao, Yun-Qian; Chen, Chen; Zhang, Cheng-Hai; Li, Wen; Shen, Hua-Hao; Ning, Wen; Kamm, Kristine E.; Stull, James T.; Gao, Xiang; Zhu, Min-Sheng

    2010-01-01

    Different interacting signaling modules involving Ca2+/calmodulin-dependent myosin light chain kinase, Ca2+-independent regulatory light chain phosphorylation, myosin phosphatase inhibition, and actin filament-based proteins are proposed as specific cellular mechanisms involved in the regulation of smooth muscle contraction. However, the relative importance of specific modules is not well defined. By using tamoxifen-activated and smooth muscle-specific knock-out of myosin light chain kinase in mice, we analyzed its role in tonic airway smooth muscle contraction. Knock-out of the kinase in both tracheal and bronchial smooth muscle significantly reduced contraction and myosin phosphorylation responses to K+-depolarization and acetylcholine. Kinase-deficient mice lacked bronchial constrictions in normal and asthmatic airways, whereas the asthmatic inflammation response was not affected. These results indicate that myosin light chain kinase acts as a central participant in the contractile signaling module of tonic smooth muscle. Importantly, contractile airway smooth muscles are necessary for physiological and asthmatic airway resistance. PMID:20018858

  13. The role of TRPP2 in agonist-induced gallbladder smooth muscle contraction.

    PubMed

    Zhong, Xingguo; Fu, Jie; Song, Kai; Xue, Nairui; Gong, Renhua; Sun, Dengqun; Luo, Huilai; He, Wenzhu; Pan, Xiang; Shen, Bing; Du, Juan

    2016-04-01

    TRPP2 channel protein belongs to the superfamily of transient receptor potential (TRP) channels and is widely expressed in various tissues, including smooth muscle in digestive gut. Accumulating evidence has demonstrated that TRPP2 can mediate Ca(2+) release from Ca(2+) stores. However, the functional role of TRPP2 in gallbladder smooth muscle contraction still remains unclear. In this study, we used Ca(2+) imaging and tension measurements to test agonist-induced intracellular Ca(2+) concentration increase and smooth muscle contraction of guinea pig gallbladder, respectively. When TRPP2 protein was knocked down in gallbladder muscle strips from guinea pig, carbachol (CCh)-evoked Ca(2+) release and extracellular Ca(2+) influx were reduced significantly, and gallbladder contractions induced by endothelin 1 and cholecystokinin were suppressed markedly as well. CCh-induced gallbladder contraction was markedly suppressed by pretreatment with U73122, which inhibits phospholipase C to terminate inositol 1,4,5-trisphosphate receptor (IP3) production, and 2-aminoethoxydiphenyl borate (2APB), which inhibits IP3 recepor (IP3R) to abolish IP3R-mediated Ca(2+) release. To confirm the role of Ca(2+) release in CCh-induced gallbladder contraction, we used thapsigargin (TG)-to deplete Ca(2+) stores via inhibiting sarco/endoplasmic reticulum Ca(2+)-ATPase and eliminate the role of store-operated Ca(2+) entry on the CCh-induced gallbladder contraction. Preincubation with 2 μmol L(-1) TG significantly decreased the CCh-induced gallbladder contraction. In addition, pretreatments with U73122, 2APB or TG abolished the difference of the CCh-induced gallbladder contraction between TRPP2 knockdown and control groups. We conclude that TRPP2 mediates Ca(2+) release from intracellular Ca(2+) stores, and has an essential role in agonist-induced gallbladder muscle contraction.

  14. Flexing the abdominals: do bigger muscles make better fighters?

    PubMed

    Mowles, Sophie L; Cotton, Peter A; Briffa, Mark

    2011-06-23

    Animal contests often involve the use of repeated signals, which are assumed to advertise stamina, and hence fighting ability. While an individual may be predicted to give up once it has crossed an energetic threshold, costs inflicted by its opponent may also contribute to the giving-up decision. Therefore, physical strength should be of key importance in contests, allowing high signal magnitude as well as potentially inflicting costs. We investigated this using hermit crab shell fights, which employ a 'hybrid signal' of shell rapping, which advertises stamina but also imposes potentially deleterious consequences for the receiver. We examined the links between contest outcomes and two proxies for strength; the protein content and relative mass of hermit crab abdominal muscles, the main muscle group used in shell rapping. Our results indicate that there was no difference in muscle protein between winners and losers, whereas winners had significantly greater muscle mass : body mass ratios. Thus, while stamina has been assumed by theory to be an important determinant of agonistic success, the present results demonstrate the importance of muscle size and thereby strength.

  15. Flexing the abdominals: do bigger muscles make better fighters?

    PubMed Central

    Mowles, Sophie L.; Cotton, Peter A.; Briffa, Mark

    2011-01-01

    Animal contests often involve the use of repeated signals, which are assumed to advertise stamina, and hence fighting ability. While an individual may be predicted to give up once it has crossed an energetic threshold, costs inflicted by its opponent may also contribute to the giving-up decision. Therefore, physical strength should be of key importance in contests, allowing high signal magnitude as well as potentially inflicting costs. We investigated this using hermit crab shell fights, which employ a ‘hybrid signal’ of shell rapping, which advertises stamina but also imposes potentially deleterious consequences for the receiver. We examined the links between contest outcomes and two proxies for strength; the protein content and relative mass of hermit crab abdominal muscles, the main muscle group used in shell rapping. Our results indicate that there was no difference in muscle protein between winners and losers, whereas winners had significantly greater muscle mass : body mass ratios. Thus, while stamina has been assumed by theory to be an important determinant of agonistic success, the present results demonstrate the importance of muscle size and thereby strength. PMID:21247940

  16. Effects of multidimensional pelvic floor muscle training in healthy young women.

    PubMed

    Talasz, Helena; Kalchschmid, Elisabeth; Kofler, Markus; Lechleitner, Monika

    2012-03-01

    Cross-sectional and interventional study to assess pelvic floor muscle (PFM) function in healthy young nulliparous women and to determine the effects of a 3-month PFM training program with emphasis on co-contraction of PFM and anterolateral abdominal muscles and on correctly performed coughing patterns. PFM function was assessed by digital vaginal palpation in 40 volunteers and graded according to the 6-point Oxford grading scale. The PFM training program was comprised theoretical instruction, as well as verbal feedback during hands-on instruction and repeated training sessions focussing on strengthening PFM and anterolateral abdominal muscle co-contraction during forced expiration and coughing. At baseline, 30 women (75%) were able to perform normal PFM contractions at rest (Oxford scale score ≥ 3); only 4 of them (10%) presented additional involuntary PFM contractions before and during coughing. The remaining 10 women (25%) were unable to perform voluntary or involuntary PFM contractions. Mean Oxford scale score in the whole group was 3.3 ± 1.7. After completing the PFM training program, 29 women (72.5%) performed cough-related PFM contractions and group mean Oxford scale score increased significantly to 4.2 ± 1.0. The study shows that PFM dysfunction may be detected even in healthy young women. Multidimensional training, however, may significantly improve PFM function.

  17. Study on contraction and relaxation of experimentally denervated and immobilized muscles: Comparison with dystrophic muscles

    NASA Technical Reports Server (NTRS)

    Takamori, M.; Tsujihata, M.; Mori, M.; Hazama, R.; Ide, Y.

    1980-01-01

    The contraction-relaxation mechanism of experimentally denervated and immobilized muscles of the rabbit is examined. Results are compared with those of human dystrophic muscles, in order to elucidate the role and extent of the neurotrophic factor, and the role played by the intrinsic activity of muscle in connection with pathogenesis and pathophysiology of this disease.

  18. Local nitric oxide synthase inhibition reduces skeletal muscle glucose uptake but not capillary blood flow during in situ muscle contraction in rats.

    PubMed

    Ross, Renee M; Wadley, Glenn D; Clark, Michael G; Rattigan, Stephen; McConell, Glenn K

    2007-12-01

    We have previously shown in humans that local infusion of a nitric oxide synthase (NOS) inhibitor into the femoral artery attenuates the increase in leg glucose uptake during exercise without influencing total leg blood flow. However, rodent studies examining the effect of NOS inhibition on contraction-stimulated skeletal muscle glucose uptake have yielded contradictory results. This study examined the effect of local infusion of an NOS inhibitor on skeletal muscle glucose uptake (2-deoxyglucose) and capillary blood flow (contrast-enhanced ultrasound) during in situ contractions in rats. Male hooded Wistar rats were anesthetized and one hindleg electrically stimulated to contract (2 Hz, 0.1 ms) for 30 min while the other leg rested. After 10 min, the NOS inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME) (arterial concentration of 5 micromol/l) or saline was infused into the epigastric artery of the contracting leg. Local NOS inhibition had no effect on blood pressure, heart rate, or muscle contraction force. Contractions increased (P < 0.05) skeletal muscle NOS activity, and this was prevented by L-NAME infusion. NOS inhibition caused a modest significant (P < 0.05) attenuation of the increase in femoral blood flow during contractions, but importantly there was no effect on capillary recruitment. NOS inhibition attenuated (P < 0.05) the increase in contraction-stimulated skeletal muscle glucose uptake by approximately 35%, without affecting AMP-activated protein kinase (AMPK) activation. NOS inhibition attenuated increases in skeletal muscle glucose uptake during contraction without influencing capillary recruitment, suggesting that NO is critical for part of the normal increase in skeletal muscle fiber glucose uptake during contraction.

  19. Reactive oxygen species generation is not different during isometric and lengthening contractions of mouse muscle

    PubMed Central

    Sloboda, Darcée D.

    2013-01-01

    Skeletal muscles can be injured by lengthening contractions, when the muscles are stretched while activated. Lengthening contractions produce structural damage that leads to the degeneration and regeneration of damaged muscle fibers by mechanisms that have not been fully elucidated. Reactive oxygen species (ROS) generated at the time of injury may initiate degenerative or regenerative processes. In the present study we hypothesized that lengthening contractions that damage the muscle would generate more ROS than isometric contractions that do not cause damage. To test our hypothesis, we subjected muscles of mice to lengthening contractions or isometric contractions and simultaneously monitored intracellular ROS generation with the fluorescent indicator 5-(and-6)-chloromethyl-2′,7′-dichlorodihydrofluorescein (CM-DCFH), which is oxidized by ROS to form the fluorescent product CM-DCF. We found that CM-DCF fluorescence was not different during or shortly after lengthening contractions compared with isometric controls, regardless of the amount of stretch and damage that occurred during the lengthening contractions. The only exception was that after severe stretches, the increase in CM-DCF fluorescence was impaired. We conclude that lengthening contractions that damage the muscle do not generate more ROS than isometric contractions that do not cause damage. The implication is that ROS generated at the time of injury are not the initiating signals for subsequent degenerative or regenerative processes. PMID:23948772

  20. Reactive oxygen species generation is not different during isometric and lengthening contractions of mouse muscle.

    PubMed

    Sloboda, Darcée D; Brooks, Susan V

    2013-10-01

    Skeletal muscles can be injured by lengthening contractions, when the muscles are stretched while activated. Lengthening contractions produce structural damage that leads to the degeneration and regeneration of damaged muscle fibers by mechanisms that have not been fully elucidated. Reactive oxygen species (ROS) generated at the time of injury may initiate degenerative or regenerative processes. In the present study we hypothesized that lengthening contractions that damage the muscle would generate more ROS than isometric contractions that do not cause damage. To test our hypothesis, we subjected muscles of mice to lengthening contractions or isometric contractions and simultaneously monitored intracellular ROS generation with the fluorescent indicator 5-(and-6)-chloromethyl-2',7'-dichlorodihydrofluorescein (CM-DCFH), which is oxidized by ROS to form the fluorescent product CM-DCF. We found that CM-DCF fluorescence was not different during or shortly after lengthening contractions compared with isometric controls, regardless of the amount of stretch and damage that occurred during the lengthening contractions. The only exception was that after severe stretches, the increase in CM-DCF fluorescence was impaired. We conclude that lengthening contractions that damage the muscle do not generate more ROS than isometric contractions that do not cause damage. The implication is that ROS generated at the time of injury are not the initiating signals for subsequent degenerative or regenerative processes.

  1. Toward Optimizing Vestibular Evoked Myogenic Potentials: Normalization Reduces the Need for Strong Neck Muscle Contraction.

    PubMed

    Noij, Kimberley S; Herrmann, Barbara S; Rauch, Steven D; Guinan, John J

    2017-01-01

    The cervical vestibular evoked myogenic potential (cVEMP) represents an inhibitory reflex of the saccule measured in the ipsilateral sternocleidomastoid muscle (SCM) in response to acoustic or vibrational stimulation. Since the cVEMP is a modulation of SCM electromyographic (EMG) activity, cVEMP amplitude is proportional to muscle EMG amplitude. We sought to evaluate muscle contraction influences on cVEMP peak-to-peak amplitudes (VEMPpp), normalized cVEMP amplitudes (VEMPn), and inhibition depth (VEMPid). cVEMPs at 500 Hz were measured in 25 healthy subjects for 3 SCM EMG contraction ranges: 45-65, 65-105, and 105-500 μV root mean square (r.m.s.). For each range, we measured cVEMP sound level functions (93-123 dB peSPL) and sound off, meaning that muscle contraction was measured without acoustic stimulation. The effect of muscle contraction amplitude on VEMPpp, VEMPn, and VEMPid and the ability to distinguish cVEMP presence/absence were evaluated. VEMPpp amplitudes were significantly greater at higher muscle contractions. In contrast, VEMPn and VEMPid showed no significant effect of muscle contraction. Cohen's d indicated that for all 3 cVEMP metrics contraction amplitude variations produced little change in the ability to distinguish cVEMP presence/absence. VEMPid more clearly indicated saccular output because when no acoustic stimulus was presented the saccular inhibition estimated by VEMPid was zero, unlike those by VEMPpp and VEMPn. Muscle contraction amplitude strongly affects VEMPpp amplitude, but contractions 45-300 μV r.m.s. produce stable VEMPn and VEMPid values. Clinically, there may be no need for subjects to exert high contraction effort. This is especially beneficial in patients for whom maintaining high SCM contraction amplitudes is challenging. © 2018 S. Karger AG, Basel.

  2. Sonomyographic responses during voluntary isometric ramp contraction of the human rectus femoris muscle.

    PubMed

    Chen, Xin; Zheng, Yong-Ping; Guo, Jing-Yi; Zhu, Zhenyu; Chan, Shing-Chow; Zhang, Zhiguo

    2012-07-01

    This paper aims to investigate the relationship between torque and muscle morphological change, which is derived from ultrasound image sequence and termed as sonomyography (SMG), during isometric ramp contraction of the rectus femoris (RF) muscle, and to further compare SMG with the electromyography (EMG) and mechanomyography (MMG), which represent the electrical and mechanical activities of the muscle. Nine subjects performed isometric ramp contraction of knee up to 90% of the maximal voluntary contraction (MVC) at speeds of 45, 22.5 and 15% MVC/s, and EMG, MMG and ultrasonography were simultaneously recorded from the RF muscle. Cross-sectional area, which was referred to as SMG, was automatically extracted from continuously captured ultrasound images using a newly developed image tracking algorithm. Polynomial regression analyses were applied to fit the EMG/MMG/SMG-to-torque relationships, and the regression coefficients of EMG, MMG, and SMG were compared. Moreover, the effect of contraction speed on SMG/EMG/MMG-to-torque relationships was tested by pair-wise comparisons of the mean relationship curves at different speeds for EMG, MMG and SMG. The results show that continuous SMG could provide important morphological parameters of continuous muscle contraction. Compared with EMG and MMG, SMG exhibits different changing patterns with the increase of torque during voluntary isometric ramp contraction, and it is less influenced by the contraction speed.

  3. Leucine-enriched essential amino acids attenuate inflammation in rat muscle and enhance muscle repair after eccentric contraction.

    PubMed

    Kato, Hiroyuki; Miura, Kyoko; Nakano, Sayako; Suzuki, Katsuya; Bannai, Makoto; Inoue, Yoshiko

    2016-09-01

    Eccentric exercise results in prolonged muscle damage that may lead to muscle dysfunction. Although inflammation is essential to recover from muscle damage, excessive inflammation may also induce secondary damage, and should thus be suppressed. In this study, we investigated the effect of leucine-enriched essential amino acids on muscle inflammation and recovery after eccentric contraction. These amino acids are known to stimulate muscle protein synthesis via mammalian target of rapamycin (mTOR), which, is also considered to alleviate inflammation. Five sets of 10 eccentric contractions were induced by electrical stimulation in the tibialis anterior muscle of male SpragueDawley rats (8-9 weeks old) under anesthesia. Animals received a 1 g/kg dose of a mixture containing 40 % leucine and 60 % other essential amino acids or distilled water once a day throughout the experiment. Muscle dysfunction was assessed based on isometric dorsiflexion torque, while inflammation was evaluated by histochemistry. Gene expression of inflammatory cytokines and myogenic regulatory factors was also measured. We found that leucine-enriched essential amino acids restored full muscle function within 14 days, at which point rats treated with distilled water had not fully recovered. Indeed, muscle function was stronger 3 days after eccentric contraction in rats treated with amino acids than in those treated with distilled water. The amino acid mix also alleviated expression of interleukin-6 and impeded infiltration of inflammatory cells into muscle, but did not suppress expression of myogenic regulatory factors. These results suggest that leucine-enriched amino acids accelerate recovery from muscle damage by preventing excessive inflammation.

  4. Histone deacetylase 8 regulates cortactin deacetylation and contraction in smooth muscle tissues

    PubMed Central

    Li, Jia; Chen, Shu; Cleary, Rachel A.; Wang, Ruping; Gannon, Olivia J.; Seto, Edward

    2014-01-01

    Histone deacetylases (HDACs) are a family of enzymes that mediate nucleosomal histone deacetylation and gene expression. Some members of the HDAC family have also been implicated in nonhistone protein deacetylation, which modulates cell-cycle control, differentiation, and cell migration. However, the role of HDACs in smooth muscle contraction is largely unknown. Here, HDAC8 was localized both in the cytoplasm and the nucleus of mouse and human smooth muscle cells. Knockdown of HDAC8 by lentivirus-encoding HDAC8 shRNA inhibited force development in response to acetylcholine. Treatment of smooth muscle tissues with HDAC8 inhibitor XXIV (OSU-HDAC-44) induced relaxation of precontracted smooth muscle tissues. In addition, cortactin is an actin-regulatory protein that undergoes deacetylation during migration of NIH 3T3 cells. In this study, acetylcholine stimulation induced cortactin deacetylation in mouse and human smooth muscle tissues, as evidenced by immunoblot analysis using antibody against acetylated lysine. Knockdown of HDAC8 by RNAi or treatment with the inhibitor attenuated cortactin deacetylation and actin polymerization without affecting myosin activation. Furthermore, expression of a charge-neutralizing cortactin mutant inhibited contraction and actin dynamics during contractile activation. These results suggest a novel mechanism for the regulation of smooth muscle contraction. In response to contractile stimulation, HDAC8 may mediate cortactin deacetylation, which subsequently promotes actin filament polymerization and smooth muscle contraction. PMID:24920679

  5. Regulation of phosphorylase kinase by low concentrations of Ca ions upon muscle contraction: the connection between metabolism and muscle contraction and the connection between muscle physiology and Ca-dependent signal transduction

    PubMed Central

    OZAWA, Eijiro

    2011-01-01

    It had long been one of the crucial questions in muscle physiology how glycogenolysis is regulated in connection with muscle contraction, when we found the answer to this question in the last half of the 1960s. By that time, the two principal currents of muscle physiology, namely, the metabolic flow starting from glycogen and the mechanisms of muscle contraction, had already been clarified at the molecular level thanks to our senior researchers. Thus, the final question we had to answer was how to connect these two currents. We found that low concentrations of Ca ions (10−7–10−4 M) released from the sarcoplasmic reticulum for the regulation of muscle contraction simultaneously reversibly activate phosphorylase kinase, the enzyme regulating glycogenolysis. Moreover, we found that adenosine 3′,5′-monophosphate (cyclic AMP), which is already known to activate muscle phosphorylase kinase, is not effective in the absence of such concentrations of Ca ions. Thus, cyclic AMP is not effective by itself alone and only modifies the activation process in the presence of Ca ions (at that time, cyclic AMP-dependent protein kinase had not yet been identified). After a while, it turned out that our works have not only provided the solution to the above problem on muscle physiology, but have also been considered as the first report of Ca-dependent protein phosphorylation, which is one of the central problems in current cell biology. Phosphorylase kinase is the first protein kinase to phosphorylate a protein resulting in the change in the function of the phosphorylated protein, as shown by Krebs and Fischer. Our works further showed that this protein kinase is regulated in a Ca-dependent manner. Accordingly, our works introduced the concept of low concentrations of Ca ions, which were first identified as the regulatory substance of muscle contraction, to the vast field of Ca biology including signal transduction. PMID:21986313

  6. Implantable power generation system utilizing muscle contractions excited by electrical stimulation.

    PubMed

    Sahara, Genta; Hijikata, Wataru; Tomioka, Kota; Shinshi, Tadahiko

    2016-06-01

    An implantable power generation system driven by muscle contractions for supplying power to active implantable medical devices, such as pacemakers and neurostimulators, is proposed. In this system, a muscle is intentionally contracted by an electrical stimulation in accordance with the demands of the active implantable medical device for electrical power. The proposed system, which comprises a small electromagnetic induction generator, electrodes with an electrical circuit for stimulation and a transmission device to convert the linear motion of the muscle contractions into rotational motion for the magneto rotor, generates electrical energy. In an ex vivo demonstration using the gastrocnemius muscle of a toad, which was 28 mm in length and weighed 1.3 g, the electrical energy generated by the prototype exceeded the energy consumed for electrical stimulation, with the net power being 111 µW. It was demonstrated that the proposed implantable power generation system has the potential to replace implantable batteries for active implantable medical devices. © IMechE 2016.

  7. Mechanical and histological characterization of the abdominal muscle. A previous step to modelling hernia surgery.

    PubMed

    Hernández, B; Peña, E; Pascual, G; Rodríguez, M; Calvo, B; Doblaré, M; Bellón, J M

    2011-04-01

    The aims of this study are to experimentally characterize the passive elastic behaviour of the rabbit abdominal wall and to develop a mechanical constitutive law which accurately reproduces the obtained experimental results. For this purpose, tissue samples from New Zealand White rabbits 2150±50 (g) were mechanically tested in vitro. Mechanical tests, consisting of uniaxial loading on tissue samples oriented along the craneo-caudal and the perpendicular directions, respectively, revealed the anisotropic non-linear mechanical behaviour of the abdominal tissues. Experiments were performed considering the composite muscle (including external oblique-EO, internal oblique-IO and transverse abdominis-TA muscle layers), as well as separated muscle layers (i.e., external oblique, and the bilayer formed by internal oblique and transverse abdominis). Both the EO muscle layer and the IO-TA bilayer demonstrated a stiffer behaviour along the transversal direction to muscle fibres than along the longitudinal one. The fibre arrangement was measured by means of a histological study which confirmed that collagen fibres are mainly responsible for the passive mechanical strength and stiffness. Furthermore, the degree of anisotropy of the abdominal composite muscle turned out to be less pronounced than those obtained while studying the EO and IO-TA separately. Moreover, a phenomenological constitutive law was used to capture the measured experimental curves. A Levenberg-Marquardt optimization algorithm was used to fit the model constants to reproduce the experimental curves. Copyright © 2010 Elsevier Ltd. All rights reserved.

  8. Chloride channel blockers promote relaxation of TEA-induced contraction in airway smooth muscle

    PubMed Central

    Yim, Peter D.; Gallos, George; Perez-zoghbi, Jose F.; Trice, Jacquelyn; Zhang, Yi; Siviski, Matthew; Sonett, Joshua; Emala, Charles W.

    2014-01-01

    Enhanced airway smooth muscle (ASM) contraction is an important component in the pathophysiology of asthma. We have shown that ligand gated chloride channels modulate ASM contractile tone during the maintenance phase of an induced contraction, however the role of chloride flux in depolarization-induced contraction remains incompletely understood. To better understand the role of chloride flux under these conditions, muscle force (human ASM, guinea pig ASM), peripheral small airway luminal area (rat ASM) and airway smooth muscle plasma membrane electrical potentials (human cultured ASM) were measured. We found ex vivo guinea pig airway rings, human ASM strips and small peripheral airways in rat lungs slices relaxed in response to niflumic acid following depolarization-induced contraction induced by K+ channel blockade with tetraethylammonium chloride (TEA). In isolated human airway smooth muscle cells TEA induce depolarization as measured by a fluorescent indicator or whole cell patch clamp and this depolarization was reversed by niflumic acid. These findings demonstrate that ASM depolarization induced contraction is dependent on chloride channel activity. Targeting of chloride channels may be a novel approach to relax hypercontractile airway smooth muscle in bronchoconstrictive disorders. PMID:24662476

  9. Chloride channel blockers promote relaxation of TEA-induced contraction in airway smooth muscle.

    PubMed

    Yim, Peter D; Gallos, George; Perez-Zoghbi, Jose F; Trice, Jacquelyn; Zhang, Yi; Siviski, Matthew; Sonett, Joshua; Emala, Charles W

    2013-01-01

    Enhanced airway smooth muscle (ASM) contraction is an important component in the pathophysiology of asthma. We have shown that ligand gated chloride channels modulate ASM contractile tone during the maintenance phase of an induced contraction, however the role of chloride flux in depolarization-induced contraction remains incompletely understood. To better understand the role of chloride flux under these conditions, muscle force (human ASM, guinea pig ASM), peripheral small airway luminal area (rat ASM) and airway smooth muscle plasma membrane electrical potentials (human cultured ASM) were measured. We found ex vivo guinea pig airway rings, human ASM strips and small peripheral airways in rat lungs slices relaxed in response to niflumic acid following depolarization-induced contraction induced by K(+) channel blockade with tetraethylammonium chloride (TEA). In isolated human airway smooth muscle cells TEA induce depolarization as measured by a fluorescent indicator or whole cell patch clamp and this depolarization was reversed by niflumic acid. These findings demonstrate that ASM depolarization induced contraction is dependent on chloride channel activity. Targeting of chloride channels may be a novel approach to relax hypercontractile airway smooth muscle in bronchoconstrictive disorders.

  10. Behavior of human gastrocnemius muscle fascicles during ramped submaximal isometric contractions.

    PubMed

    Héroux, Martin E; Stubbs, Peter W; Herbert, Robert D

    2016-09-01

    Precise estimates of muscle architecture are necessary to understand and model muscle mechanics. The primary aim of this study was to estimate continuous changes in fascicle length and pennation angle in human gastrocnemius muscles during ramped plantar flexor contractions at two ankle angles. The secondary aim was to determine whether these changes differ between proximal and distal fascicles. Fifteen healthy subjects performed ramped contractions (0-25% MVC) as ultrasound images were recorded from the medial (MG, eight sites) and lateral (LG, six sites) gastrocnemius muscle with the ankle at 90° and 120° (larger angles correspond to shorter muscle lengths). In all subjects, fascicles progressively shortened with increasing torque. MG fascicles shortened 5.8 mm (11.1%) at 90° and 4.5 mm (12.1%) at 120°, whereas LG muscle fascicles shortened 5.1 mm (8.8%) at both ankle angles. MG pennation angle increased 1.4° at 90° and 4.9° at 120°, and LG pennation angle decreased 0.3° at 90° and increased 2.6° at 120°. Muscle architecture changes were similar in proximal and distal fascicles at both ankle angles. This is the first study to describe continuous changes in fascicle length and pennation angle in the human gastrocnemius muscle during ramped isometric contractions. Very similar changes occurred in proximal and distal muscle regions. These findings are relevant to studies modeling active muscle mechanics. © 2016 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society.

  11. Fragmented esophageal smooth muscle contraction segments on high resolution manometry: a marker of esophageal hypomotility.

    PubMed

    Porter, R F; Kumar, N; Drapekin, J E; Gyawali, C P

    2012-08-01

    Esophageal peristalsis consists of a chain of contracting striated and smooth muscle segments on high resolution manometry (HRM). We compared smooth muscle contraction segments in symptomatic subjects with reflux disease to healthy controls. High resolution manometry Clouse plots were analyzed in 110 subjects with reflux disease (50 ± 1.4 years, 51.5% women) and 15 controls (27 ± 2.1 years, 60.0% women). Using the 30 mmHg isobaric contour tool, sequences were designated fragmented if either smooth muscle contraction segment was absent or if the two smooth muscle segments were separated by a pressure trough, and failed if both smooth muscle contraction segments were absent. The discriminative value of contraction segment analysis was assessed. A total of 1115 swallows were analyzed (reflux group: 965, controls: 150). Reflux subjects had lower peak and averaged contraction amplitudes compared with controls (P < 0.0001 for all comparisons). Fragmented sequences followed 18.4% wet swallows in the reflux group, compared with 7.5% in controls (P < 0.0001), and were seen more frequently than failed sequences (7.9% and 2.5%, respectively). Using a threshold of 30% in individual subjects, a composite of failed and/or fragmented sequences was effective in segregating reflux subjects from control subjects (P = 0.04). Evaluation of smooth muscle contraction segments adds value to HRM analysis. Specifically, fragmented smooth muscle contraction segments may be a marker of esophageal hypomotility. © 2012 Blackwell Publishing Ltd.

  12. Electromyographic analysis of traditional and nontraditional abdominal exercises: implications for rehabilitation and training.

    PubMed

    Escamilla, Rafael F; Babb, Eric; DeWitt, Ryan; Jew, Patrick; Kelleher, Patrick; Burnham, Toni; Busch, Juliann; D'Anna, Kristen; Mowbray, Ryan; Imamura, Rodney T

    2006-05-01

    Performing nontraditional abdominal exercises with devices such as abdominal straps, the Power Wheel, and the Ab Revolutionizer has been suggested as a way to activate abdominal and extraneous (nonabdominal) musculature as effectively as more traditional abdominal exercises, such as the crunch and bent-knee sit-up. The purpose of this study was to test the effectiveness of traditional and nontraditional abdominal exercises in activating abdominal and extraneous musculature. Twenty-one men and women who were healthy and between 23 and 43 years of age were recruited for this study. Surface electromyography (EMG) was used to assess muscle activity from the upper and lower rectus abdominis, external and internal oblique, rectus femoris, latissimus dorsi, and lumbar paraspinal muscles while each exercise was performed. The EMG data were normalized to maximum voluntary muscle contractions. Differences in muscle activity were assessed by a 1-way, repeated-measures analysis of variance. Upper and lower rectus abdominis, internal oblique, and latissimus dorsi muscle EMG activity were highest for the Power Wheel (pike, knee-up, and roll-out), hanging knee-up with straps, and reverse crunch inclined 30 degrees. External oblique muscle EMG activity was highest for the Power Wheel (pike, knee-up, and roll-out) and hanging knee-up with straps. Rectus femoris muscle EMG activity was highest for the Power Wheel (pike and knee-up), reverse crunch inclined 30 degrees, and bent-knee sit-up. Lumbar paraspinal muscle EMG activity was low and similar among exercises. The Power Wheel (pike, knee-up, and roll-out), hanging knee-up with straps, and reverse crunch inclined 30 degrees not only were the most effective exercises in activating abdominal musculature but also were the most effective in activating extraneous musculature. The relatively high rectus femoris muscle activity obtained with the Power Wheel (pike and knee-up), reverse crunch inclined 30 degrees, and bent-knee sit-up may

  13. Treatment of abdominal cellulite and circumference reduction with radiofrequency and dynamic muscle activation.

    PubMed

    Wanitphakdeedecha, Rungsima; Iamphonrat, Thanawan; Thanomkitti, Kanchalit; Lektrakul, Nittaya; Manuskiatti, Woraphong

    2015-01-01

    Cellulite is a frequent skin condition for which treatment remains a challenge. A wide variety of treatments are available but most procedures offer suboptimal clinical effect and/or delayed therapeutic outcome. Only few therapeutic options have proven efficacy in the treatment of cellulite. To determine the efficacy and the safety profiles of radiofrequency and dynamic muscle activation technology in treatment of abdominal cellulite and circumference reduction. Twenty-five females with abdominal cellulite received 6 weekly radiofrequency and dynamic muscle activation treatments. Treatment areas included the abdomen and both sides of flanks. Subjects were evaluated using standardized photographs, and measurements of body weight and abdominal circumference at baseline, before every treatment visit, and 1 week and four weeks after the final treatment. Subcutaneous tissue thickness was recorded by ultrasound at baseline and 4 weeks after completion of treatment protocol. Physicians' evaluation and patient's satisfaction of clinical improvement were also measured. All subjects completed the treatment protocol and attended every follow-up visits. There was significant abdominal circumference reduction of 2.96 and 2.52 cm at 1-, and 4-week follow-up visits (p < 0.05), respectively. At four weeks after the last treatment, the average circumferential reduction was sustained. Most of the patients were rated to have 25-49% improvement at 5th treatment, and 1- and 4-week follow-up visits. Ninety-two percent of the patients were satisfied with the treatment outcome. Radiofrequency provided beneficial effects on the reduction of abdomen and cellulite appearance. The benefit of muscle activation is yet to be determined.

  14. Improved Cell Culture Method for Growing Contracting Skeletal Muscle Models

    NASA Technical Reports Server (NTRS)

    Marquette, Michele L.; Sognier, Marguerite A.

    2013-01-01

    An improved method for culturing immature muscle cells (myoblasts) into a mature skeletal muscle overcomes some of the notable limitations of prior culture methods. The development of the method is a major advance in tissue engineering in that, for the first time, a cell-based model spontaneously fuses and differentiates into masses of highly aligned, contracting myotubes. This method enables (1) the construction of improved two-dimensional (monolayer) skeletal muscle test beds; (2) development of contracting three-dimensional tissue models; and (3) improved transplantable tissues for biomedical and regenerative medicine applications. With adaptation, this method also offers potential application for production of other tissue types (i.e., bone and cardiac) from corresponding precursor cells.

  15. Characterization of muscarinic receptors mediating relaxation and contraction in the rat iris dilator muscle.

    PubMed Central

    Masuda, Y; Yamahara, N S; Tanaka, M; Ryang, S; Kawai, T; Imaizumi, Y; Watanabe, M

    1995-01-01

    1. The characteristics of muscarinic receptors mediating relaxation and/or contraction in the rat iris dilator muscle were examined. 2. Relaxation was induced in a dilator muscle by application of acetylcholine (ACh) at low doses (3 microM or less) and contraction was induced by high doses. Methacholine and carbachol also showed biphasic effects similar to those of ACh; in contrast, bethanechol, arecoline, pilocarpine and McN-A-343 induced mainly relaxation but no substantial contraction. 3. After parasympathetic denervation by ciliary ganglionectomy, the relaxant response to muscarinic agonists disappeared upon nerve stimulation. Application of McN-A-343 and pilocarpine induced only small contractions in denervated dilator muscles, indicating that these are partial agonists for contraction. 4. pA2 values of pirenzepine, methoctramine, AF-DX 116, himbacine, and 4-DAMP for antagonism to pilocarpine-induced relaxation in normal dilator muscles and those for antagonism to ACh-induced contraction in denervated dilator muscles were determined. The pA2 values for antagonism to relaxation of all these antagonists were most similar to those for M3-type muscarinic receptors. 5. Although pA2 values for contraction of these antagonists, except for methoctramine, were very close to those for relaxation, contraction was not significantly antagonized by methoctramine. Contraction might be mediated by M3-like receptors which have a very low affinity for methoctramine. 6. In conclusion, ACh-induced biphasic responses in rat iris dilator muscles were clearly distinguished from each other by specific muscarinic agonists and parasympathetic denervation, whereas muscarinic receptors could not be subclassified according to the pA2 values of 5 specific antagonists only. PMID:7539696

  16. FKBP12 deficiency reduces strength deficits after eccentric contraction-induced muscle injury

    PubMed Central

    Corona, Benjamin T.; Rouviere, Clement; Hamilton, Susan L.; Ingalls, Christopher P.

    2008-01-01

    Strength deficits associated with eccentric contraction-induced muscle injury stem, in part, from excitation-contraction uncoupling. FKBP12 is a 12-kDa binding protein known to bind to the skeletal muscle sarcoplasmic reticulum Ca2+ release channel [ryanodine receptor (RyR1)] and plays an important role in excitation-contraction coupling. To assess the effects of FKBP12 deficiency on muscle injury and recovery, we measured anterior crural muscle (tibialis anterior and extensor digitorum longus muscles) strength in skeletal muscle-specific FKBP12-deficient and wild-type (WT) mice before and after a single bout of 150 eccentric contractions, as well as before and after the performance of six injury bouts. Histological damage of the tibialis anterior muscle was assessed after injury. Body weight and peak isometric and eccentric torques were lower in FKBP12-deficient mice compared with WT mice. There were no differences between FKBP12-deficient and WT mice in preinjury peak isometric and eccentric torques when normalized to body weight, and no differences in the relative decreases in eccentric torque with a single or multiple injury bouts. After a single injury bout, FKBP12-deficient mice had less initial strength deficits and recovered faster (especially females) than WT mice, despite no differences in the degree of histological damage. After multiple injury bouts, FKBP12-deficient mice recovered muscle strength faster than WT mice and exhibited significantly less histological muscle damage than WT mice. In summary, FKBP12 deficiency results in less initial strength deficits and enhanced recovery from single (especially females) and repeated bouts of injury than WT mice. PMID:18511525

  17. Leucine-Enriched Essential Amino Acids Augment Muscle Glycogen Content in Rats Seven Days after Eccentric Contraction

    PubMed Central

    Kato, Hiroyuki; Miura, Kyoko; Suzuki, Katsuya; Bannai, Makoto

    2017-01-01

    Eccentric contractions induce muscle damage, which impairs recovery of glycogen and adenosine tri-phosphate (ATP) content over several days. Leucine-enriched essential amino acids (LEAAs) enhance the recovery in muscles that are damaged after eccentric contractions. However, the role of LEAAs in this process remains unclear. We evaluated the content in glycogen and high energy phosphates molecules (phosphocreatine (PCr), adenosine di-phosphate (ADP) and ATP) in rats that were following electrically stimulated eccentric contractions. Muscle glycogen content decreased immediately after the contraction and remained low for the first three days after the stimulation, but increased seven days after the eccentric contraction. LEAAs administration did not change muscle glycogen content during the first three days after the contraction. Interestingly, however, it induced a further increase in muscle glycogen seven days after the stimulation. Contrarily, ATP content decreased immediately after the eccentric contraction, and remained lower for up to seven days after. Additionally, LEAAs administration did not affect the ATP content over the experimental period. Finally, ADP and PCr levels did not significantly change after the contractions or LEAA administration. LEAAs modulate the recovery of glycogen content in muscle after damage-inducing exercise. PMID:29065533

  18. Leucine-Enriched Essential Amino Acids Augment Muscle Glycogen Content in Rats Seven Days after Eccentric Contraction.

    PubMed

    Kato, Hiroyuki; Miura, Kyoko; Suzuki, Katsuya; Bannai, Makoto

    2017-10-23

    Eccentric contractions induce muscle damage, which impairs recovery of glycogen and adenosine tri-phosphate (ATP) content over several days. Leucine-enriched essential amino acids (LEAAs) enhance the recovery in muscles that are damaged after eccentric contractions. However, the role of LEAAs in this process remains unclear. We evaluated the content in glycogen and high energy phosphates molecules (phosphocreatine (PCr), adenosine di-phosphate (ADP) and ATP) in rats that were following electrically stimulated eccentric contractions. Muscle glycogen content decreased immediately after the contraction and remained low for the first three days after the stimulation, but increased seven days after the eccentric contraction. LEAAs administration did not change muscle glycogen content during the first three days after the contraction. Interestingly, however, it induced a further increase in muscle glycogen seven days after the stimulation. Contrarily, ATP content decreased immediately after the eccentric contraction, and remained lower for up to seven days after. Additionally, LEAAs administration did not affect the ATP content over the experimental period. Finally, ADP and PCr levels did not significantly change after the contractions or LEAA administration. LEAAs modulate the recovery of glycogen content in muscle after damage-inducing exercise.

  19. Activation amplitude and temporal synchrony among back extensor and abdominal muscles during a controlled transfer task: comparison of men and women.

    PubMed

    Hubley-Kozey, Cheryl L; Butler, Heather L; Kozey, John W

    2012-08-01

    Muscle synergies are important for spinal stability, but few studies examine temporal responses of spinal muscles to dynamic perturbations. This study examined activation amplitudes and temporal synergies among compartments of the back extensor and among abdominal wall muscles in response to dynamic bidirectional moments of force. We further examined whether responses were different between men and women. 19 women and 18 men performed a controlled transfer task. Surface electromyograms from bilateral sites over 6 back extensor compartments and 6 abdominal wall muscle sites were analyzed using principal component analysis. Key features were extracted from the measured electromyographic waveforms capturing amplitude and temporal variations among muscle sites. Three features explained 97% of the variance. Scores for each feature were computed for each measured waveform and analysis of variance found significant (p<.05) muscle main effects and a sex by muscle interaction. For the back extensors, post hoc analysis revealed that upper and more medial sites were recruited to higher amplitudes, medial sites responded to flexion moments, and the more lateral sites responded to lateral flexion moments. Women had more differences among muscle sites than men for the lateral flexion moment feature. For the abdominal wall muscles the oblique muscles responded with synergies related to fiber orientation, with women having higher amplitudes and more responsiveness to the lateral flexion moment than men. Synergies between the abdominal and back extensor sites as the moment demands change are discussed. These findings illustrate differential activation among erector spinae compartments and abdominal wall muscle sites supporting a highly organized pattern of response to bidirectional external moments with asynchronies more apparent in women. Copyright © 2012 Elsevier B.V. All rights reserved.

  20. Altered response of the anterolateral abdominal muscles to simulated weight-bearing in subjects with low back pain.

    PubMed

    Hides, Julie A; Belavý, Daniel L; Cassar, Lana; Williams, Michelle; Wilson, Stephen J; Richardson, Carolyn A

    2009-03-01

    An important aspect of neuromuscular control at the lumbo-pelvic region is stabilization. Subjects with low back pain (LBP) have been shown to exhibit impairments in motor control of key muscles which contribute to stabilization of the lumbo-pelvic region. However, a test of automatic recruitment that relates to function has been lacking. A previous study used ultrasound imaging to show that healthy subjects automatically recruited the transversus abdominis (TrA) and internal oblique (IO) muscles in response to a simulated weight-bearing task. This task has not been investigated in subjects with LBP. The aim of this study was to compare the automatic recruitment of the abdominal muscles among subjects with and without LBP in response to the simulated weight-bearing task. Twenty subjects with and without LBP were tested. Real-time ultrasound imaging was used to assess changes in thickness of the TrA and internal oblique IO muscles as well as lateral movement ("slide") of the anterior fascial insertion of the TrA muscle. Results showed that subjects with LBP showed significantly less shortening of the TrA muscle (P < 0.0001) and greater increases in thickness of the IO muscle (P = 0.002) with the simulated weight-bearing task. There was no significant difference between groups for changes in TrA muscle thickness (P = 0.055). This study provides evidence of changes in motor control of the abdominal muscles in subjects with LBP. This test may provide a functionally relevant and non-invasive method to investigate the automatic recruitment of the abdominal muscles in people with and without LBP.

  1. Abdominal muscle function and incisional hernia: a systematic review.

    PubMed

    Jensen, K K; Kjaer, M; Jorgensen, L N

    2014-08-01

    Although ventral incisional hernia (VIH) repair in patients is often evaluated in terms of hernia recurrence rate and health-related quality of life, there is no clear consensus regarding optimal operative treatment based on these parameters. It was proposed that health-related quality of life depends largely on abdominal muscle function (AMF), and the present review thus evaluates to what extent AMF is influenced by VIH and surgical repair. The PubMed and EMBASE databases were searched for articles following a systematic strategy for inclusion. A total of seven studies described AMF in relation to VIH. Five studies examined AMF using objective isokinetic dynamometers to determine muscle strength, and two studies examined AMF by clinical examination-based muscle tests. Both equipment-related and functional muscle tests exist for use in patients with VIH, but very few studies have evaluated AMF in VIH. There are no randomized controlled studies to describe the impact of VIH repair on AMF, and no optimal surgical treatment in relation to AMF after VIH repair can be advocated for at this time.

  2. Oblique abdominal muscle activity in response to external perturbations when pushing a cart.

    PubMed

    Lee, Yun-Ju; Hoozemans, Marco J M; van Dieën, Jaap H

    2010-05-07

    Cyclic activation of the external and internal oblique muscles contributes to twisting moments during normal gait. During pushing while walking, it is not well understood how these muscles respond to presence of predictable (cyclic push-off forces) and unpredictable (external) perturbations that occur in pushing tasks. We hypothesized that the predictable perturbations due to the cyclic push-off forces would be associated with cyclic muscle activity, while external perturbations would be counteracted by cocontraction of the oblique abdominal muscles. Eight healthy male subjects pushed at two target forces and two handle heights in a static condition and while walking without and with external perturbations. For all pushing tasks, the median, the static (10th percentile) and the peak levels (90th percentile) of the electromyographic amplitudes were determined. Linear models with oblique abdominal EMGs and trunk angles as input were fit to the twisting moments, to estimate trunk stiffness. There was no significant difference between the static EMG levels in pushing while walking compared to the peak levels in pushing while standing. When pushing while walking, the additional dynamic activity was associated with the twisting moments, which were actively modulated by the pairs of oblique muscles as in normal gait. The median and static levels of trunk muscle activity and estimated trunk stiffness were significantly higher when perturbations occurred than without perturbations. The increase baseline of muscle activity indicated cocontraction of the antagonistic muscle pairs. Furthermore, this cocontraction resulted in an increased trunk stiffness around the longitudinal axis. Copyright 2010 Elsevier Ltd. All rights reserved.

  3. Trigeminal Proprioception Evoked by Strong Stretching of the Mechanoreceptors in Müller's Muscle Induces Reflex Contraction of the Orbital Orbicularis Oculi Slow-Twitch Muscle Fibers.

    PubMed

    Matsuo, Kiyoshi; Ban, Ryokuya; Ban, Midori; Yuzuriha, Shunsuke

    2014-01-01

    The mixed orbicularis oculi muscle lacks an intramuscular proprioceptive system such as muscle spindles, to induce reflex contraction of its slow-twitch fibers. We evaluated whether the mechanoreceptors in Müller's muscle function as extrinsic mechanoreceptors to induce reflex contraction of the slow-twitch fibers of the orbicularis oculi in addition to those of the levator and frontalis muscles. We evaluated in patients with aponeurosis-disinserted blepharoptosis whether strong stretching of the mechanoreceptors in Müller's muscle from upgaze with unilateral lid load induced reflex contraction of the orbicularis oculi slow-twitch fibers and whether anesthesia of Müller's muscle precluded the contraction. We compared the electromyographic responses of the bilateral orbicularis oculi muscles to unilateral intraoperative direct stimulation of the trigeminal proprioceptive nerve with those to unilateral transcutaneous electrical stimulation of the supraorbital nerve. Upgaze with a unilateral 3-g lid load induced reflex contraction of the bilateral orbicularis oculi muscles with ipsilateral dominance. Anesthesia of Müller's muscle precluded the reflex contraction. The orbicularis oculi reflex evoked by stimulation of the trigeminal proprioceptive nerve differed from that by electrical stimulation of the supraorbital nerve in terms of the intensity of current required to induce the reflex, the absence of R1, and duration. The mechanoreceptors in Müller's muscle functions as an extramuscular proprioceptive system to induce reflex contraction of the orbital orbicularis oculi slow-twitch fibers. Whereas reflex contraction of the pretarsal orbicularis fast-twitch fibers functions in spontaneous or reflex blinking, that of the orbital orbicularis oculi slow-twitch fibers may factor in grimacing and blepharospasm.

  4. The interrelation between aPKC and glucose uptake in the skeletal muscle during contraction and insulin stimulation.

    PubMed

    Santos, J M; Benite-Ribeiro, S A; Queiroz, G; Duarte, J A

    2014-12-01

    Contraction and insulin increase glucose uptake in skeletal muscle. While the insulin pathway, better characterized, requires activation of phosphoinositide 3-kinase (PI3K) and atypical protein kinase (aPKC), muscle contraction seems to share insulin-activated components to increase glucose uptake. This study aimed to investigate the interrelation between the pathway involved in glucose uptake evoked by insulin and muscle contraction. Isolated muscle of rats was treated with solvent (control), insulin, wortmannin (PI3K inhibitor) and the combination of insulin plus wortmannin. After treatment, muscles were electrically stimulated (contracted) or remained at rest. Glucose transporter 4 (GLUT4) localization, glucose uptake and phospho-aPKC (aPKC activated form) were assessed. Muscle contraction and insulin increased glucose uptake in all conditions when compared with controls not stimulating an effect that was accompanied by an increase in GLUT4 and of phospho-aPKC at the muscle membrane. Contracted muscles treated with insulin did not show additive effects on glucose uptake or aPKC activity compared with the response when these stimuli were applied alone. Inhibition of PI3K blocked insulin effect on glucose uptake and aPKC but not in the contractile response. Thus, muscle contraction seems to stimulate aPKC and glucose uptake independently of PI3K. Therefore, aPKC may be a convergence point and a rate limit step in the pathway by which, insulin and contraction, increase glucose uptake in skeletal muscle. Copyright © 2014 John Wiley & Sons, Ltd.

  5. Optical induction of muscle contraction at the tissue scale through intrinsic cellular amplifiers.

    PubMed

    Yoon, Jonghee; Choi, Myunghwan; Ku, Taeyun; Choi, Won Jong; Choi, Chulhee

    2014-08-01

    The smooth muscle cell is the principal component responsible for involuntary control of visceral organs, including vascular tonicity, secretion, and sphincter regulation. It is known that the neurotransmitters released from nerve endings increase the intracellular Ca(2+) level in smooth muscle cells followed by muscle contraction. We herein report that femtosecond laser pulses focused on the diffraction-limited volume can induce intracellular Ca(2+) increases in the irradiated smooth muscle cell without neurotransmitters, and locally increased intracellular Ca(2+) levels are amplified by calcium-induced calcium-releasing mechanisms through the ryanodine receptor, a Ca(2+) channel of the endoplasmic reticulum. The laser-induced Ca(2+) increases propagate to adjacent cells through gap junctions. Thus, ultrashort-pulsed lasers can induce smooth muscle contraction by controlling Ca(2+), even with optical stimulation of the diffraction-limited volume. This optical method, which leads to reversible and reproducible muscle contraction, can be used in research into muscle dynamics, neuromuscular disease treatment, and nanorobot control. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Comparison of the sonographic features of the abdominal wall muscles and connective tissues in individuals with and without lumbopelvic pain.

    PubMed

    Whittaker, Jackie L; Warner, Martin B; Stokes, Maria

    2013-01-01

    Cross-sectional, case-control study. To measure and compare the resting thickness of the 4 abdominal wall muscles, their associated perimuscular connective tissue (PMCT), and interrecti distance (IRD) in persons with and without lumbopelvic pain (LPP), using ultrasound imaging. The muscles and PMCT of the abdominal wall assist in controlling the spine. Functional deficits of the abdominal wall muscles have been detected in populations with LPP. Investigations of the abdominal wall in those with LPP are primarily concerned with muscle, most commonly the transversus abdominis (TrA) and internal oblique (IO). Because the abdominal wall functions as a unit, all 4 abdominal muscles and their associated connective tissues should be considered concurrently. B-mode ultrasound imaging was used to measure the resting thickness of the rectus abdominis (RA), external oblique, IO, and TrA muscles; the PMCT planes; and IRD in 50 male and female subjects, 25 with and 25 without LPP (mean ± SD age, 36.3 ± 9.4 and 46.6 ± 8.0 years, respectively). Univariate correlation analysis was used to identify covariates. Analyses of covariance (ANCOVAs) and the Kruskal-Wallis test (IRD) were used to compare cohorts (α = .05). The LPP cohort had less total abdominal muscle thickness (LPP mean ± SD, 18.9 ± 3.0 mm; control, 20.3 ± 3.0 mm; ANCOVA adjusted for body mass index, P = .03), thicker PMCT (LPP, 5.5 ± 0.2 mm; control, 4.3 ± 0.2 mm; ANCOVA adjusted for body mass index, P = .007), and wider IRD (LPP, 11.5 ± 2.0 mm; control, 8.4 ± 1.8 mm; Kruskal-Wallis, P = .005). Analysis of individual muscle thickness revealed no difference in the external oblique, IO, and TrA, but a thinner RA in the LPP cohort (LPP mean ± SD, 7.8 ± 1.5 mm; control, 9.1 ± 1.2 mm; ANCOVA adjusted for body mass index, P<.001). To our knowledge, this is the first study to investigate the morphological characteristics of all 4 abdominal muscles and PMCT in individuals with LPP. The results suggest that there

  7. Illusion caused by vibration of muscle spindles reveals an involvement of muscle spindle inputs in regulating isometric contraction of masseter muscles.

    PubMed

    Tsukiboshi, Taisuke; Sato, Hajime; Tanaka, Yuto; Saito, Mitsuru; Toyoda, Hiroki; Morimoto, Toshifumi; Türker, Kemal Sitki; Maeda, Yoshinobu; Kang, Youngnam

    2012-11-01

    Spindle Ia afferents may be differentially involved in voluntary isometric contraction, depending on the pattern of synaptic connections in spindle reflex pathways. We investigated how isometric contraction of masseter muscles is regulated through the activity of their muscle spindles that contain the largest number of intrafusal fibers among skeletal muscle spindles by examining the effects of vibration of muscle spindles on the voluntary isometric contraction. Subjects were instructed to hold the jaw at resting position by counteracting ramp loads applied on lower molar teeth. In response to the increasing-ramp load, the root mean square (RMS) of masseter EMG activity almost linearly increased under no vibration, while displaying a steep linear increase followed by a slower increase under vibration. The regression line of the relationship between the load and RMS was significantly steeper under vibration than under no vibration, suggesting that the subjects overestimated the ramp load and excessively counteracted it as reflected in the emergence of bite pressure. In response to the decreasing-ramp load applied following the increasing one, the RMS hardly decreased under vibration unlike under no vibration, leading to a generation of bite pressure even after the offset of the negative-ramp load until the vibration was ceased. Thus the subjects overestimated the increasing rate of the load while underestimating the decreasing rate of the load, due to the vibration-induced illusion of jaw opening. These observations suggest that spindle Ia/II inputs play crucial roles both in estimating the load and in controlling the isometric contraction of masseter muscles in the jaw-closed position.

  8. Abdominothoracic mechanisms of functional abdominal distension and correction by biofeedback.

    PubMed

    Barba, Elizabeth; Burri, Emanuel; Accarino, Anna; Cisternas, Daniel; Quiroga, Sergi; Monclus, Eva; Navazo, Isabel; Malagelada, Juan-R; Azpiroz, Fernando

    2015-04-01

    In patients with functional gut disorders, abdominal distension has been associated with descent of the diaphragm and protrusion of the anterior abdominal wall. We investigated mechanisms of abdominal distension in these patients. We performed a prospective study of 45 patients (42 women, 24-71 years old) with functional intestinal disorders (27 with irritable bowel syndrome with constipation, 15 with functional bloating, and 3 with irritable bowel syndrome with alternating bowel habits) and discrete episodes of visible abdominal distension. Subjects were assessed by abdominothoracic computed tomography (n = 39) and electromyography (EMG) of the abdominothoracic wall (n = 32) during basal conditions (without abdominal distension) and during episodes of severe abdominal distension. Fifteen patients received a median of 2 sessions (range, 1-3 sessions) of EMG-guided, respiratory-targeted biofeedback treatment; 11 received 1 control session before treatment. Episodes of abdominal distension were associated with diaphragm contraction (19% ± 3% increase in EMG score and 12 ± 2 mm descent; P < .001 vs basal values) and intercostal contraction (14% ± 3% increase in EMG scores and 6 ± 1 mm increase in thoracic antero-posterior diameter; P < .001 vs basal values). They were also associated with increases in lung volume (501 ± 93 mL; P < .001 vs basal value) and anterior abdominal wall protrusion (32 ± 3 mm increase in girth; P < .001 vs basal). Biofeedback treatment, but not control sessions, reduced the activity of the intercostal muscles (by 19% ± 2%) and the diaphragm (by 18% ± 4%), activated the internal oblique muscles (by 52% ± 13%), and reduced girth (by 25 ± 3 mm) (P ≤ .009 vs pretreatment for all). In patients with functional gut disorders, abdominal distension is a behavioral response that involves activity of the abdominothoracic wall. This distension can be reduced with EMG-guided, respiratory-targeted biofeedback therapy. Copyright © 2015 AGA

  9. Spatial interaction between tissue pressure and skeletal muscle perfusion during contraction.

    PubMed

    van Donkelaar, C C; Huyghe, J M; Vankan, W J; Drost, M R

    2001-05-01

    The vascular waterfall theory attributes decreased muscle perfusion during contraction to increased intramuscular pressure (P(IM)) and concomitant increase in venous resistance. Although P(IM) is distributed during contractions, this theory does not account for heterogeneity. This study hypothesises that pressure heterogeneity could affect the interaction between P(IM) rise and perfusion. Regional tissue perfusion during submaximum (100kPa) tetanic contraction is studied, using a finite element model of perfused contracting skeletal muscle. Capillary flow in muscles with one proximal artery and vein (SIM(1)) and with an additional distal artery and vein (SIM(2)) is compared. Blood flow and pressures at rest and P(IM) during contraction ( approximately 25kPa maximally) are similar between simulations, but capillary flow and venous pressure differ. In SIM(2), venous pressure and capillary flow correspond to P(IM) distribution, whereas capillary flow in SIM(1) is less than 10% of flow in SIM(2), in the muscle half without draining vein. This difference is caused by a high central P(IM), followed by central venous pressure rise, in agreement with the waterfall theory. The high central pressure (SIM(1)), obstructs outflow from the distal veins. Distal venous pressure rises until central blood pressure is reached, although local P(IM) is low. Adding a distal vein (SIM(2)) restores the perfusion. It is concluded that regional effects contribute to the interaction between P(IM) and perfusion during contraction. Unlike stated by the vascular waterfall theory, venous pressure may locally exceed P(IM). Although this can be explained by the principles of this theory, the theory does not include this phenomenon as such.

  10. Connective tissue regeneration in skeletal muscle after eccentric contraction-induced injury.

    PubMed

    Mackey, Abigail L; Kjaer, Michael

    2017-03-01

    Human skeletal muscle has the potential to regenerate completely after injury induced under controlled experimental conditions. The events inside the myofibers as they undergo necrosis, followed closely by satellite cell-mediated myogenesis, have been mapped in detail. Much less is known about the adaptation throughout this process of both the connective tissue structures surrounding the myofibers and the fibroblasts, the cells responsible for synthesizing this connective tissue. However, the few studies investigating muscle connective tissue remodeling demonstrate a strong response that appears to be sustained for a long time after the major myofiber responses have subsided. While the use of electrical stimulation to induce eccentric contractions vs. voluntary eccentric contractions appears to lead to a greater extent of myofiber necrosis and regenerative response, this difference is not apparent when the muscle connective tissue responses are compared, although further work is required to confirm this. Pharmacological agents (growth hormone and angiotensin II type I receptor blockers) are considered in the context of accelerating the muscle connective tissue adaptation to loading. Cautioning against this, however, is the association between muscle matrix protein remodeling and protection against reinjury, which suggests that a (so far undefined) period of vulnerability to reinjury may exist during the remodeling phases. The role of individual muscle matrix components and their spatial interaction during adaptation to eccentric contractions is an unexplored field in human skeletal muscle and may provide insight into the optimal timing of rest vs. return to activity after muscle injury. Copyright © 2017 the American Physiological Society.

  11. Muscle contraction controls skeletal morphogenesis through regulation of chondrocyte convergent extension.

    PubMed

    Shwartz, Yulia; Farkas, Zsuzsanna; Stern, Tomer; Aszódi, Attila; Zelzer, Elazar

    2012-10-01

    Convergent extension driven by mediolateral intercalation of chondrocytes is a key process that contributes to skeletal growth and morphogenesis. While progress has been made in deciphering the molecular mechanism that underlies this process, the involvement of mechanical load exerted by muscle contraction in its regulation has not been studied. Using the zebrafish as a model system, we found abnormal pharyngeal cartilage morphology in both chemically and genetically paralyzed embryos, demonstrating the importance of muscle contraction for zebrafish skeletal development. The shortening of skeletal elements was accompanied by prominent changes in cell morphology and organization. While in control the cells were elongated, chondrocytes in paralyzed zebrafish were smaller and exhibited a more rounded shape, confirmed by a reduction in their length-to-width ratio. The typical columnar organization of cells was affected too, as chondrocytes in various skeletal elements exhibited abnormal stacking patterns, indicating aberrant intercalation. Finally, we demonstrate impaired chondrocyte intercalation in growth plates of muscle-less Sp(d) mouse embryos, implying the evolutionary conservation of muscle force regulation of this essential morphogenetic process.Our findings provide a new perspective on the regulatory interaction between muscle contraction and skeletal morphogenesis by uncovering the role of muscle-induced mechanical loads in regulating chondrocyte intercalation in two different vertebrate models. Copyright © 2012 Elsevier Inc. All rights reserved.

  12. Acetyl group availability influences phosphocreatine degradation even during intense muscle contraction

    PubMed Central

    Timmons, James A; Constantin-Teodosiu, Dumitru; Poucher, Simon M; Greenhaff, Paul L

    2004-01-01

    We previously established that activation of the pyruvate dehydrogenase complex (PDC) using dichloroacetate (DCA) reduced the reliance on substrate-level phosphorylation (SLP) at the onset of exercise, with normal and reduced blood flow. PDC activation also reduced fatigue development during contraction with reduced blood flow. Since these observations, several studies have re-evaluated our observations. One study demonstrated a performance benefit without a reduction in SLP, raising a question mark over PDC's role in the regulation of ATP regeneration and our interpretation of fatigue mechanisms. Using a model of muscle contraction similar to the conflicting study (i.e. tetanic rather than twitch stimulation), we re-examined this question. Using canine skeletal muscle, one group was infused with saline while the other was pretreated with 300 mg (kg body mass)−1 DCA. Muscle biopsies were taken at rest, peak tension (1 min) and after 6 min of tetanic electrical stimulation (75 ms on−925 ms off per second) and blood flow was limited to 25% of normal values observed during contraction. DCA reduced phosphocreatine (PCr) degradation by 40% during the first minute of contraction, but did not prevent the almost complete depletion of PCr stores at 6 min, while muscle fatigue did not differ between the two groups. During intermittent tetanic stimulation PCr degradation was 75% greater than with our previous 3 Hz twitch contraction protocol, despite a similar rate of oxygen consumption at 6 min. Thus, in the present study enhanced acetyl group availability altered the time course of PCr utilization but did not prevent the decline towards depletion. Consistent with our earlier conclusions, DCA pretreatment reduces muscle fatigue only when SLP is attenuated. The present study and our met-analysis indicates that enhanced acetyl group availability results in a readily measurable reduction in SLP when the initial rate of PCr utilization is ∼1 mmol (kg dry mass)−1 s−1 or

  13. Nonlinear deformation of skeletal muscles in a passive state and in isotonic contraction

    NASA Astrophysics Data System (ADS)

    Shil'ko, S. V.; Chernous, D. A.; Pleskachevskii, Yu. M.

    2012-07-01

    A procedure for a two-level modeling of deformation of skeletal muscles is offered. Based on a phenomenological model of an individual muscle fiber, consisting of a viscous, a contractive, and two nonlinearly elastic elements (the first level), various means for describing a skeletal muscle as a whole (the second, macroscopic level) are considered. A method for identification of a muscle model by utilizing experimental elongation diagrams in a passive state and in isotonic contraction is put forward. The results of a biomechanical analysis are compared with known experimental data for the isotonic and isometric activation regimes of tailor's muscle of a frog. It is established that preferable is the description of a muscle that takes into account the different lengths of muscle fibers and their twist.

  14. The association of cortactin with profilin-1 is critical for smooth muscle contraction.

    PubMed

    Wang, Ruping; Cleary, Rachel A; Wang, Tao; Li, Jia; Tang, Dale D

    2014-05-16

    Profilin-1 (Pfn-1) is an actin-regulatory protein that has a role in modulating smooth muscle contraction. However, the mechanisms that regulate Pfn-1 in smooth muscle are not fully understood. Here, stimulation with acetylcholine induced an increase in the association of the adapter protein cortactin with Pfn-1 in smooth muscle cells/tissues. Furthermore, disruption of the protein/protein interaction by a cell-permeable peptide (CTTN-I peptide) attenuated actin polymerization and smooth muscle contraction without affecting myosin light chain phosphorylation at Ser-19. Knockdown of cortactin by lentivirus-mediated RNAi also diminished actin polymerization and smooth muscle force development. However, cortactin knockdown did not affect myosin activation. In addition, cortactin phosphorylation has been implicated in nonmuscle cell migration. In this study, acetylcholine stimulation induced cortactin phosphorylation at Tyr-421 in smooth muscle cells. Phenylalanine substitution at this position impaired cortactin/Pfn-1 interaction in response to contractile activation. c-Abl is a tyrosine kinase that is necessary for actin dynamics and contraction in smooth muscle. Here, c-Abl silencing inhibited the agonist-induced cortactin phosphorylation and the association of cortactin with Pfn-1. Finally, treatment with CTTN-I peptide reduced airway resistance and smooth muscle hyperreactivity in a murine model of asthma. These results suggest that the interaction of cortactin with Pfn-1 plays a pivotal role in regulating actin dynamics, smooth muscle contraction, and airway hyperresponsiveness in asthma. The association of cortactin with Pfn-1 is regulated by c-Abl-mediated cortactin phosphorylation. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

  15. The Association of Cortactin with Profilin-1 Is Critical for Smooth Muscle Contraction*

    PubMed Central

    Wang, Ruping; Cleary, Rachel A.; Wang, Tao; Li, Jia; Tang, Dale D.

    2014-01-01

    Profilin-1 (Pfn-1) is an actin-regulatory protein that has a role in modulating smooth muscle contraction. However, the mechanisms that regulate Pfn-1 in smooth muscle are not fully understood. Here, stimulation with acetylcholine induced an increase in the association of the adapter protein cortactin with Pfn-1 in smooth muscle cells/tissues. Furthermore, disruption of the protein/protein interaction by a cell-permeable peptide (CTTN-I peptide) attenuated actin polymerization and smooth muscle contraction without affecting myosin light chain phosphorylation at Ser-19. Knockdown of cortactin by lentivirus-mediated RNAi also diminished actin polymerization and smooth muscle force development. However, cortactin knockdown did not affect myosin activation. In addition, cortactin phosphorylation has been implicated in nonmuscle cell migration. In this study, acetylcholine stimulation induced cortactin phosphorylation at Tyr-421 in smooth muscle cells. Phenylalanine substitution at this position impaired cortactin/Pfn-1 interaction in response to contractile activation. c-Abl is a tyrosine kinase that is necessary for actin dynamics and contraction in smooth muscle. Here, c-Abl silencing inhibited the agonist-induced cortactin phosphorylation and the association of cortactin with Pfn-1. Finally, treatment with CTTN-I peptide reduced airway resistance and smooth muscle hyperreactivity in a murine model of asthma. These results suggest that the interaction of cortactin with Pfn-1 plays a pivotal role in regulating actin dynamics, smooth muscle contraction, and airway hyperresponsiveness in asthma. The association of cortactin with Pfn-1 is regulated by c-Abl-mediated cortactin phosphorylation. PMID:24700464

  16. Na(+)-K (+) pump location and translocation during muscle contraction in rat skeletal muscle.

    PubMed

    Kristensen, Michael; Rasmussen, Martin Krøyer; Juel, Carsten

    2008-08-01

    Muscle contraction may up-regulate the number of Na(+)-K(+) pumps in the plasma membrane by translocation of subunits. Since there is still controversy about where this translocation takes place from and if it takes place at all, the present study used different techniques to characterize the translocation. Electrical stimulation and biotin labeling of rat muscle revealed a 40% and 18% increase in the amounts of the Na(+)-K(+) pump alpha(2) subunit and caveolin-3 (Cav-3), respectively, in the sarcolemma. Exercise induced a 36% and 19% increase in the relative amounts of the alpha(2) subunit and Cav-3, respectively, in an outer-membrane-enriched fraction and a 41% and 17% increase, respectively, in sarcolemma giant vesicles. The Na(+)-K(+) pump activity measured with the 3-O-MFPase assay was increased by 37% in giant vesicles from exercised rats. Immunoprecipitation with Cav-3 antibody showed that 17%, 11% and 14% of the alpha(1) subunits were associated with Cav-3 in soleus, extensor digitorum longus, and mixed muscles, respectively. For the alpha(2), the corresponding values were 17%, 5% and 16%. In conclusion; muscle contraction induces translocation of the alpha subunits, which is suggested to be caused partly by structural changes in caveolae and partly by translocation from an intracellular pool.

  17. Smooth muscle contraction: mechanochemical formulation for homogeneous finite strains.

    PubMed

    Stålhand, J; Klarbring, A; Holzapfel, G A

    2008-01-01

    Chemical kinetics of smooth muscle contraction affect mechanical properties of organs that function under finite strains. In an effort to gain further insight into organ physiology, we formulate a mechanochemical finite strain model by considering the interaction between mechanical and biochemical components of cell function during activation. We propose a new constitutive framework and use a mechanochemical device that consists of two parallel elements: (i) spring for the cell stiffness; (ii) contractile element for the sarcomere. We use a multiplicative decomposition of cell elongation into filament contraction and cross-bridge deformation, and suggest that the free energy be a function of stretches, four variables (free unphosphorylated myosin, phosphorylated cross-bridges, phosphorylated and dephosphorylated cross-bridges attached to actin), chemical state variable driven by Ca2+-concentration, and temperature. The derived constitutive laws are thermodynamically consistent. Assuming isothermal conditions, we specialize the mechanical phase such that we recover the linear model of Yang et al. [2003a. The myogenic response in isolated rat cerebrovascular arteries: smooth muscle cell. Med. Eng. Phys. 25, 691-709]. The chemical phase is also specialized so that the linearized chemical evolution law leads to the four-state model of Hai and Murphy [1988. Cross-bridge phosphorylation and regulation of latch state in smooth muscle. Am. J. Physiol. 254, C99-C106]. One numerical example shows typical mechanochemical effects and the efficiency of the proposed approach. We discuss related parameter identification, and illustrate the dependence of muscle contraction (Ca2+-concentration) on active stress and related stretch. Mechanochemical models of this kind serve the mathematical basis for analyzing coupled processes such as the dependency of tissue properties on the chemical kinetics of smooth muscle.

  18. Trigeminal Proprioception Evoked by Strong Stretching of the Mechanoreceptors in Müller's Muscle Induces Reflex Contraction of the Orbital Orbicularis Oculi Slow-Twitch Muscle Fibers

    PubMed Central

    Ban, Ryokuya; Ban, Midori; Yuzuriha, Shunsuke

    2014-01-01

    Objective: The mixed orbicularis oculi muscle lacks an intramuscular proprioceptive system such as muscle spindles, to induce reflex contraction of its slow-twitch fibers. We evaluated whether the mechanoreceptors in Müller's muscle function as extrinsic mechanoreceptors to induce reflex contraction of the slow-twitch fibers of the orbicularis oculi in addition to those of the levator and frontalis muscles. Methods: We evaluated in patients with aponeurosis-disinserted blepharoptosis whether strong stretching of the mechanoreceptors in Müller's muscle from upgaze with unilateral lid load induced reflex contraction of the orbicularis oculi slow-twitch fibers and whether anesthesia of Müller's muscle precluded the contraction. We compared the electromyographic responses of the bilateral orbicularis oculi muscles to unilateral intraoperative direct stimulation of the trigeminal proprioceptive nerve with those to unilateral transcutaneous electrical stimulation of the supraorbital nerve. Results: Upgaze with a unilateral 3-g lid load induced reflex contraction of the bilateral orbicularis oculi muscles with ipsilateral dominance. Anesthesia of Müller's muscle precluded the reflex contraction. The orbicularis oculi reflex evoked by stimulation of the trigeminal proprioceptive nerve differed from that by electrical stimulation of the supraorbital nerve in terms of the intensity of current required to induce the reflex, the absence of R1, and duration. Conclusions: The mechanoreceptors in Müller's muscle functions as an extramuscular proprioceptive system to induce reflex contraction of the orbital orbicularis oculi slow-twitch fibers. Whereas reflex contraction of the pretarsal orbicularis fast-twitch fibers functions in spontaneous or reflex blinking, that of the orbital orbicularis oculi slow-twitch fibers may factor in grimacing and blepharospasm. PMID:25210572

  19. Time to Maximal Voluntary Isometric Contraction (MVC) for Five Different Muscle Groups in College Adults.

    ERIC Educational Resources Information Center

    Morris, A. F.; And Others

    1983-01-01

    College men and women were studied to ascertain the force-time components of a rapid voluntary muscle contraction for five muscle groups. Researchers found that the time required for full contraction differs: (1) in men and women; and (2) among the five muscle groups. (Authors/PP)

  20. Acoustic myography as an indicator of force during sustained contractions of a small hand muscle.

    PubMed

    Goldenberg, M S; Yack, H J; Cerny, F J; Burton, H W

    1991-01-01

    To test the hypothesis that muscle sound amplitudes would remain constant during sustained submaximal isometric contractions, we recorded acoustic myograms from the abductor digiti minimi muscle in 12 subjects at 15, 25, 50, and 75% of a maximum voluntary contraction (MVC). Muscle sounds were detected with an omni-directional electret microphone encased in closed-cell foam and attached to the skin over the muscle. Acoustic amplitudes from the middle and end of the sustained contractions were compared with the amplitudes from the beginning of contractions to determine whether acoustic amplitudes varied in magnitude as force remained constant. Physiological tremor was eliminated from the acoustic signal by use of a Fourier truncation at 14 Hz. The amplitudes of the acoustic signal at a contraction intensity of 75% MVC remained constant, reflecting force production over time. At 50% MVC, the root-mean-square amplitude decreased from the beginning to the end of the contraction (P less than 0.05). Acoustic amplitudes increased over time at 15 and 25% MVC and were significantly higher at the end of the contractions than at the beginning (P less than 0.05). Alterations in the acoustic amplitude, which reflect changes in the lateral vibrations of the muscle, may be indicative of the different recruitment strategies used to maintain force during sustained isometric contractions.

  1. Impact of Cricothyroid Muscle Contraction on Vocal Fold Vibration: Experimental Study with High-Speed Videoendoscopy.

    PubMed

    Ishikawa, Camila Cristina; Pinheiro, Thais Gonçalves; Hachiya, Adriana; Montagnoli, Arlindo Neto; Tsuji, Domingos Hiroshi

    2017-05-01

    The aim of this study was to evaluate the effects of cricothyroid muscle contraction on vocal fold vibration, as evaluated with high-speed videoendoscopy, and to identify one or more aspects of vocal fold vibration that could be used as an irrefutable indicator of unilateral cricothyroid muscle paralysis. This was an experimental study employing excised human larynges. Twenty freshly excised human larynges were evaluated during artificially produced vibration. Each larynx was assessed in three situations: bilateral cricothyroid muscle contraction, unilateral cricothyroid muscle contraction, and no contraction of either cricothyroid muscle. The following parameters were evaluated by high-speed videoendoscopy: fundamental frequency, periodicity, amplitude of vocal fold vibration, and phase symmetry between the vocal folds. Although neither unilateral nor bilateral cricothyroid muscle contraction altered the periodicity of vibration or the occurrence of phase asymmetry, there was a significant decrease in fundamental frequency in parallel with decreasing longitudinal tension. We also found an increase in vibration amplitude of right and left vocal folds, which were similar in terms of their behavior for this parameter in the various situations studied. Our results suggest that differences in vibration amplitude and phase symmetry between vocal folds are not reliable indicators of unilateral cricothyroid muscle paralysis. Copyright © 2017 The Voice Foundation. Published by Elsevier Inc. All rights reserved.

  2. Comparison of Lateral Abdominal Muscle Thickness and Cross Sectional Area of Multifidus in Adolescent Soccer Players with and without Low Back Pain: A Case Control Study.

    PubMed

    Noormohammadpour, Pardis; Hosseini Khezri, Alireza; Linek, Paweł; Mansournia, Mohammad Ali; Hassannejad, Alireza; Younesian, Ali; Farahbakhsh, Farzin; Kordi, Ramin

    2016-12-01

    Low back pain (LBP) is a common complaint amongst adolescent athletes. While different studies have shown association between LBP and trunk muscle thickness in the general population, few articles have studied it in adolescent athletes. The aim of this study is to compare lateral abdominal muscle thickness and function, and cross sectional area (CSA) of lumbar multifidus (LM) in adolescent soccer players with and without LBP. In total, 28 adolescent soccer players with and without LBP, from the premier league participated in this study. The thickness of external oblique, internal oblique and transversus abdominis and the CSA of the LM muscles at L4 level on both sides were measured at rest and contraction via ultrasound imaging (USI). In addition, leg length discrepancy, hamstring flexibility, active lumbar forward flexion, and isometric muscle endurance of trunk extensors were measured in both groups. (study design/setting: case control study). The mean (SD) age in LBP group and non-LBP group were 14.0 (1.1) and 14.1 (0.9) years, respectively. There was no significant difference in baseline characteristics of participants between groups. Findings showed no significant difference between LBP and non-LBP groups comparing all measured variables. The data obtained support that there is not a correlation between abdominal muscle thickness and CSA of the lumbar multifidi and LBP in adolescent soccer players. These findings suggest that other factors rather than the thickness of deep trunk muscles may play a more significant role in the etiology of LBP in adolescent soccer players.

  3. Comparison of the thickness of lateral abdominal muscles between pregnant women with and without low back pain.

    PubMed

    Rostami, Mohsen; Noormohammadpour, Pardis; Mansournia, Mohammad Ali; Hantoushzadeh, Sedigheh; Farahbakhsh, Farzin; Nourian, Ruhollah; Kordi, Ramin

    2015-05-01

    To compare the thickness of the external oblique, internal oblique, and transversus abdominis muscles in pregnant subjects with and without low back pain (LBP) by the use of ultrasound to measure thickness. A case-control study. An academic and tertiary care referral spine and sports medicine center. Fifty pregnant women with LBP during pregnancy and 54 pregnant control subjects. Case and control subjects were matched for body mass index, gestational age, and number of previous pregnancies. A multiple linear regression model with adjustment for the gestational age of the subjects, as the potential confounder of the primary outcomes, was used to evaluate the association between LBP appearance and abdominal muscles thickness of the subjects. The thickness of lateral abdominal muscles was measured by ultrasound with the subject in a hook-lying position on the examination table. We found that there was no significant difference between pregnant subjects with and without LBP in terms of the thickness of external oblique, internal oblique, and transversus abdominis muscles. These findings suggest that other factors rather than the thickness of core stabilizing muscles are influential in the etiology of LBP during pregnancy. We hypothesize that enlargement of uterus during pregnancy might influence the thickness of the lateral abdominal muscles. Copyright © 2015 American Academy of Physical Medicine and Rehabilitation. Published by Elsevier Inc. All rights reserved.

  4. Genome-Wide Association Study for Muscle Fat Content and Abdominal Fat Traits in Common Carp (Cyprinus carpio)

    PubMed Central

    Zheng, Xianhu; Kuang, Youyi; Lv, Weihua; Cao, Dingchen; Sun, Zhipeng; Sun, Xiaowen

    2016-01-01

    Muscle fat content is an important phenotypic trait in fish, as it affects the nutritional, technical and sensory qualities of flesh. To identify loci and candidate genes associated with muscle fat content and abdominal fat traits, we performed a genome-wide association study (GWAS) using the common carp 250 K SNP assay in a common carp F2 resource population. A total of 18 loci surpassing the genome-wide suggestive significance level were detected for 4 traits: fat content in dorsal muscle (MFdo), fat content in abdominal muscle (MFab), abdominal fat weight (AbFW), and AbFW as a percentage of eviscerated weight (AbFP). Among them, one SNP (carp089419) affecting both AbFW and AbFP reached the genome-wide significance level. Ten of those loci were harbored in or near known genes. Furthermore, relative expressions of 5 genes related to MFdo were compared using dorsal muscle samples with high and low phenotypic values. The results showed that 4 genes were differentially expressed between the high and low phenotypic groups. These genes are, therefore, prospective candidate genes for muscle fat content: ankyrin repeat domain 10a (ankrd10a), tetratricopeptide repeat, ankyrin repeat and coiled-coil containing 2 (tanc2), and four jointed box 1 (fjx1) and choline kinase alpha (chka). These results offer valuable insights into the complex genetic basis of fat metabolism and deposition. PMID:28030623

  5. Microprocessor Controlled Isometric Contractions of Cat Gastrocnemius Muscle.

    DTIC Science & Technology

    1981-12-01

    A-A15 504 AIR FORCE INST OF TECH WRIGHT-PATTERSON AFS OH 5CHOO--ETC F/6 6/2 MICROPROCESSOR CONTROLLED ISOMETRIC CONTRACTIONS OF CAT GASTROC-ETC(U) D...CONTROLLED ISOMETRIC CONTRACTIONS OF CAT GASTROCNEMIUS MUSCLE THESIS Presented to the Faculty of the School of Engineering of the Air Force Institute of...1981 Appzoved for public release; distribution unlimited. AFIT/GE/EE/81D-4O \\ MICROPROCESSOR CONTROLLED ISOMETRIC COMUtCTIONS OF CAT GASTfOCNEMIUS i

  6. A peripheral governor regulates muscle contraction.

    PubMed

    MacIntosh, Brian R; Shahi, M Reza S

    2011-02-01

    Active skeletal muscles are capable of keeping the global [adenosine triphosphate (ATP)] reasonably constant during exercise, whether it is mild exercise, activating a few motor units, or all-out exercise using a substantial mass of muscle. This could only be accomplished if there were regulatory processes in place not only to replenish ATP as quickly as possible, but also to modulate the rate of ATP use when that rate threatens to exceed the rate of ATP replenishment, a situation that could lead to metabolic catastrophe. This paper proposes that there is a regulatory process or "peripheral governor" that can modulate activation of muscle to avoid metabolic catastrophe. A peripheral governor, working at the cellular level, should be able to reduce the cellular rate of ATP hydrolysis associated with muscle contraction by attenuating activation. This would necessarily cause something we call peripheral fatigue (i.e., reduced contractile response to a given stimulation). There is no doubt that peripheral fatigue occurs. It has been demonstrated in isolated muscles, in muscles in situ with no central nervous system input, and in intact human subjects performing voluntary exercise with small muscle groups or doing whole-body exercise. The regulation of muscle activation is achieved in at least 3 ways (decreasing membrane excitability, inhibiting Ca2+ release through ryanodine receptors, and decreasing the availability of Ca2+ in the sarcoplasmic reticulum), making this a highly redundant control system. The peripheral governor attenuates cellular activation to reduce the metabolic demand, thereby preserving ATP and the integrity of the cell.

  7. Prostaglandins induce vasodilatation of the microvasculature during muscle contraction and induce vasodilatation independent of adenosine

    PubMed Central

    Murrant, Coral L; Dodd, Jason D; Foster, Andrew J; Inch, Kristin A; Muckle, Fiona R; Ruiz, Della A; Simpson, Jeremy A; Scholl, Jordan H P

    2014-01-01

    Blood flow data from contracting muscle in humans indicates that adenosine (ADO) stimulates the production of nitric oxide (NO) and vasodilating prostaglandins (PG) to produce arteriolar vasodilatation in a redundant fashion such that when one is inhibited the other can compensate. We sought to determine whether these redundant mechanisms are employed at the microvascular level. First, we determined whether PGs were involved in active hyperaemia at the microvascular level. We stimulated four to five skeletal muscle fibres in the anaesthetized hamster cremaster preparation in situ and measured the change in diameter of 2A arterioles (maximum diameter 40 μm, third arteriolar level up from the capillaries) at a site of overlap with the stimulated muscle fibres before and after 2 min of contraction [stimulus frequencies: 4, 20 and 60 Hz at 15 contractions per minute (CPM) or contraction frequencies of 6, 15 or 60 CPM at 20 Hz; 250 ms train duration]. Muscle fibres were stimulated in the absence and presence of the phospholipase A2 inhibitor quinacrine. Further, we applied a range of concentrations of ADO (10−7–10−5 m) extraluminally, (to mimic muscle contraction) in the absence and presence of l-NAME (NO synthase inhibitor), indomethacin (INDO, cyclooxygenase inhibitor) and l-NAME + INDO and observed the response of 2A arterioles. We repeated the latter experiment on a different level of the cremaster microvasculature (1A arterioles) and on the microvasculature of a different skeletal muscle (gluteus maximus, 2A arterioles). We observed that quinacrine inhibited vasodilatation during muscle contraction at intermediate and high contraction frequencies (15 and 60 CPM). l-NAME, INDO and l-NAME + INDO were not effective at inhibiting vasodilatation induced by any concentration of ADO tested in 2A and 1A arterioles in the cremaster muscle or 2A arterioles in the gluteus maximus muscle. Our data show that PGs are involved in the vasodilatation of the microvasculature

  8. Prostaglandins induce vasodilatation of the microvasculature during muscle contraction and induce vasodilatation independent of adenosine.

    PubMed

    Murrant, Coral L; Dodd, Jason D; Foster, Andrew J; Inch, Kristin A; Muckle, Fiona R; Ruiz, Della A; Simpson, Jeremy A; Scholl, Jordan H P

    2014-03-15

    Blood flow data from contracting muscle in humans indicates that adenosine (ADO) stimulates the production of nitric oxide (NO) and vasodilating prostaglandins (PG) to produce arteriolar vasodilatation in a redundant fashion such that when one is inhibited the other can compensate. We sought to determine whether these redundant mechanisms are employed at the microvascular level. First, we determined whether PGs were involved in active hyperaemia at the microvascular level. We stimulated four to five skeletal muscle fibres in the anaesthetized hamster cremaster preparation in situ and measured the change in diameter of 2A arterioles (maximum diameter 40 μm, third arteriolar level up from the capillaries) at a site of overlap with the stimulated muscle fibres before and after 2 min of contraction [stimulus frequencies: 4, 20 and 60 Hz at 15 contractions per minute (CPM) or contraction frequencies of 6, 15 or 60 CPM at 20 Hz; 250 ms train duration]. Muscle fibres were stimulated in the absence and presence of the phospholipase A2 inhibitor quinacrine. Further, we applied a range of concentrations of ADO (10(-7)-10(-5) M) extraluminally, (to mimic muscle contraction) in the absence and presence of L-NAME (NO synthase inhibitor), indomethacin (INDO, cyclooxygenase inhibitor) and L-NAME + INDO and observed the response of 2A arterioles. We repeated the latter experiment on a different level of the cremaster microvasculature (1A arterioles) and on the microvasculature of a different skeletal muscle (gluteus maximus, 2A arterioles). We observed that quinacrine inhibited vasodilatation during muscle contraction at intermediate and high contraction frequencies (15 and 60 CPM). L-NAME, INDO and L-NAME + INDO were not effective at inhibiting vasodilatation induced by any concentration of ADO tested in 2A and 1A arterioles in the cremaster muscle or 2A arterioles in the gluteus maximus muscle. Our data show that PGs are involved in the vasodilatation of the microvasculature in

  9. {beta}-Catenin regulates airway smooth muscle contraction.

    PubMed

    Jansen, Sepp R; Van Ziel, Anna M; Baarsma, Hoeke A; Gosens, Reinoud

    2010-08-01

    beta-Catenin is an 88-kDa member of the armadillo family of proteins that is associated with the cadherin-catenin complex in the plasma membrane. This complex interacts dynamically with the actin cytoskeleton to stabilize adherens junctions, which play a central role in force transmission by smooth muscle cells. Therefore, in the present study, we hypothesized a role for beta-catenin in the regulation of smooth muscle force production. beta-Catenin colocalized with smooth muscle alpha-actin (sm-alpha-actin) and N-cadherin in plasma membrane fractions and coimmunoprecipitated with sm-alpha-actin and N-cadherin in lysates of bovine tracheal smooth muscle (BTSM) strips. Moreover, immunocytochemistry of cultured BTSM cells revealed clear and specific colocalization of sm-alpha-actin and beta-catenin at the sites of cell-cell contact. Treatment of BTSM strips with the pharmacological beta-catenin/T cell factor-4 (TCF4) inhibitor PKF115-584 (100 nM) reduced beta-catenin expression in BTSM whole tissue lysates and in plasma membrane fractions and reduced maximal KCl- and methacholine-induced force production. These changes in force production were not accompanied by changes in the expression of sm-alpha-actin or sm-myosin heavy chain (MHC). Likewise, small interfering RNA (siRNA) knockdown of beta-catenin in BTSM strips reduced beta-catenin expression and attenuated maximal KCl- and methacholine-induced contractions without affecting sm-alpha-actin or sm-MHC expression. Conversely, pharmacological (SB-216763, LiCl) or insulin-induced inhibition of glycogen synthase kinase-3 (GSK-3) enhanced the expression of beta-catenin and augmented maximal KCl- and methacholine-induced contractions. We conclude that beta-catenin is a plasma membrane-associated protein in airway smooth muscle that regulates active tension development, presumably by stabilizing cell-cell contacts and thereby supporting force transmission between neighboring cells.

  10. Characterizing rapid-onset vasodilation to single muscle contractions in the human leg

    PubMed Central

    Credeur, Daniel P.; Holwerda, Seth W.; Restaino, Robert M.; King, Phillip M.; Crutcher, Kiera L.; Laughlin, M. Harold; Padilla, Jaume

    2014-01-01

    Rapid-onset vasodilation (ROV) following single muscle contractions has been examined in the forearm of humans, but has not yet been characterized in the leg. Given known vascular differences between the arm and leg, we sought to characterize ROV following single muscle contractions in the leg. Sixteen healthy men performed random ordered single contractions at 5, 10, 20, 40, and 60% of their maximum voluntary contraction (MVC) using isometric knee extension made with the leg above and below heart level, and these were compared with single isometric contractions of the forearm (handgrip). Single thigh cuff compressions (300 mmHg) were utilized to estimate the mechanical contribution to leg ROV. Continuous blood flow was determined by duplex-Doppler ultrasound and blood pressure via finger photoplethysmography (Finometer). Single isometric knee extensor contractions produced intensity-dependent increases in peak leg vascular conductance that were significantly greater than the forearm in both the above- and below-heart level positions (e.g., above heart level: leg 20% MVC, +138 ± 28% vs. arm 20% MVC, +89 ± 17%; P < 0.05). Thigh cuff compressions also produced a significant hyperemic response, but these were brief and smaller in magnitude compared with single isometric contractions in the leg. Collectively, these data demonstrate the presence of a rapid and robust vasodilation to single muscle contractions in the leg that is largely independent of mechanical factors, thus establishing the leg as a viable model to study ROV in humans. PMID:25539935

  11. Role of medullary astroglial glutamine synthesis in tooth pulp hypersensitivity associated with frequent masseter muscle contraction.

    PubMed

    Watase, Tetsuro; Shimizu, Kohei; Ohara, Kinuyo; Komiya, Hiroki; Kanno, Kohei; Hatori, Keisuke; Noma, Noboru; Honda, Kuniya; Tsuboi, Yoshiyuki; Katagiri, Ayano; Shinoda, Masamichi; Ogiso, Bunnai; Iwata, Koichi

    2018-01-01

    Background The mechanisms underlying tooth pulp hypersensitivity associated with masseter muscle hyperalgesia remain largely underinvestigated. In the present study, we aimed to determine whether masseter muscle contraction induced by daily electrical stimulation influences the mechanical head-withdrawal threshold and genioglossus electromyography activity caused by the application of capsaicin to the upper first molar tooth pulp. We further investigated whether astroglial glutamine synthesis is involved in first molar tooth pulp hypersensitivity associated with masseter muscle contraction. Methods The first molar tooth pulp was treated with capsaicin or vehicle in masseter muscle contraction or sham rats, following which the astroglial glutamine synthetase inhibitor methionine sulfoximine or Phosphate buffered saline (PBS) was applied. Astroglial activation was assessed via immunohistochemistry. Results The mechanical head-withdrawal threshold of the ipsilateral masseter muscle was significantly decreased in masseter muscle contraction rats than in sham rats. Genioglossus electromyography activity was significantly higher in masseter muscle contraction rats than sham rats. Glial fibrillary acidic protein-immunoreactive cell density was significantly higher in masseter muscle contraction rats than in sham rats. Administration of methionine sulfoximine induced no significant changes in the density of glial fibrillary acidic protein-immunoreactive cells relative to PBS treatment. However, mechanical head-withdrawal threshold was significantly higher in masseter muscle contraction rats than PBS-treated rats after methionine sulfoximine administration. Genioglossus electromyography activity following first molar tooth pulp capsaicin treatment was significantly lower in methionine sulfoximine-treated rats than in PBS-treated rats. In the ipsilateral region, the total number of phosphorylated extracellular signal-regulated protein kinase immunoreactive cells in the

  12. Co-contraction behaviour of masticatory and neck muscles during tooth grinding.

    PubMed

    Giannakopoulos, N N; Schindler, H J; Hellmann, D

    2018-07-01

    The objective of this study was to analyse the co-contraction behaviour of jaw and neck muscles during force-controlled experimental grinding in the supine position. Twelve symptom-free subjects were enrolled in the experimental study. Electromyographic (EMG) activity of semispinalis capitis, splenius capitis and levator scapulae muscles was recorded bilaterally with intramuscular fine-wire electrodes, whereas that of sternocleidomastoideus, infrahyoidal, suprahyoidal, masseter and anterior temporalis muscles were registered with surface electrodes. EMG and force measurements were performed during tasks simulating tooth grinding on custom-made intraoral metal splints. The mean EMG activity normalised by maximum voluntary contraction (% MVC) of each of the neck muscles studied during grinding was analysed and compared with previous data from jaw clenching at identical force (100 N) and (supine) position. The occurrence of low-level, long-lasting tonic activation (LLTA) of motor units was also documented. The mean three-dimensional force vector of the grinding forces was 106 ± 74 N. In the frontal plane, the incline to the midsagittal plane ranged between 10° and 15°. In the midsagittal plane, the incline to the frontal plane was negligibly small. Posterior neck muscle activity during grinding ranged between 4.5% and 12% MVC and during clenching with 100 N between 1.8% and 9.9% MVC. Masticatory muscle activity during grinding ranged between 17% and 21% MVC for contralateral masseter and ipsilateral temporalis and between 4% and 6.5% for ipsilateral masseter and contralateral temporalis. LLTA had an average duration of 195 ± 10 seconds. The findings from this study do not support pathophysiological muscle chain theories postulating simple biomechanical coupling of neck and jaw muscles. Co-contractions of neck and masticatory muscles may instead occur as a result of complex neurophysiological interactions. © 2018 John Wiley & Sons Ltd.

  13. Comparison of EMG activity on abdominal muscles during plank exercise with unilateral and bilateral additional isometric hip adduction.

    PubMed

    Kim, Soo-Yong; Kang, Min-Hyeok; Kim, Eui-Ryong; Jung, In-Gui; Seo, Eun-Young; Oh, Jae-Seop

    2016-10-01

    The aim of this study was to investigate the effects of additional isometric hip adduction during the plank exercise on the abdominal muscles. Twenty healthy young men participated in this study. Surface electromyography (EMG) was used to monitor the activity of the bilateral rectus abdominis (RA), the internal oblique (IO), and the external oblique (EO) muscles. The participants performed three types of plank exercise; the standard plank exercise, the plank exercise with bilateral isometric hip adduction, and the plank exercise with unilateral isometric hip adduction. All abdominal muscle activity was significantly increased during the plank exercise combined with the bilateral and unilateral isometric hip adduction compared with the standard plank exercise (p<0.05). Bilateral IO, EO, and left RA muscle activity was significantly increased during the unilateral isometric hip adduction compared with the bilateral isometric hip adduction (p<0.05). These findings suggest that additional isometric hip adduction during the plank exercise could be a useful method to enhance abdominal muscle activity. In particular, the unilateral isometric hip adduction is a more beneficial exercise than the bilateral isometric hip adduction. Copyright © 2016 Elsevier Ltd. All rights reserved.

  14. Evidence for postsynaptic modulation of muscle contraction by a Drosophila neuropeptide.

    PubMed

    Clark, Julie; Milakovic, Maja; Cull, Amanda; Klose, Markus K; Mercier, A Joffre

    2008-07-01

    DPKQDFMRFamide, the most abundant FMRFamide-like peptide in Drosophila melanogaster, has been shown previously to enhance contractions of larval body wall muscles elicited by nerve stimulation and to increase excitatory junction potentials (EJPs). The present work investigated the possibility that this peptide can also stimulate muscle contraction by a direct action on muscle fibers. DPKQDFMRFamide induced slow contractions and increased tonus in body wall muscles of Drosophila larvae from which the central nervous system had been removed. The threshold for this effect was approximately 10(-8)M. The increase in tonus persisted in the presence of 7x10(-3)M glutamate, which desensitized postsynaptic glutamate receptors. Thus, the effect on tonus could not be explained by enhanced release of glutamate from synaptic terminals and, thus, may represent a postsynaptic effect. The effect on tonus was abolished in calcium-free saline and by treatment with L-type calcium channel blockers, nifedipine and nicardipine, but not by T-type blockers, amiloride and flunarizine. The present results provide evidence that this Drosophila peptide can act postsynaptically in addition to its apparent presynaptic effects, and that the postsynaptic effect requires influx through L-type calcium channels.

  15. Drebrin-like protein DBN-1 is a sarcomere component that stabilizes actin filaments during muscle contraction.

    PubMed

    Butkevich, Eugenia; Bodensiek, Kai; Fakhri, Nikta; von Roden, Kerstin; Schaap, Iwan A T; Majoul, Irina; Schmidt, Christoph F; Klopfenstein, Dieter R

    2015-07-06

    Actin filament organization and stability in the sarcomeres of muscle cells are critical for force generation. Here we identify and functionally characterize a Caenorhabditis elegans drebrin-like protein DBN-1 as a novel constituent of the muscle contraction machinery. In vitro, DBN-1 exhibits actin filament binding and bundling activity. In vivo, DBN-1 is expressed in body wall muscles of C. elegans. During the muscle contraction cycle, DBN-1 alternates location between myosin- and actin-rich regions of the sarcomere. In contracted muscle, DBN-1 is accumulated at I-bands where it likely regulates proper spacing of α-actinin and tropomyosin and protects actin filaments from the interaction with ADF/cofilin. DBN-1 loss of function results in the partial depolymerization of F-actin during muscle contraction. Taken together, our data show that DBN-1 organizes the muscle contractile apparatus maintaining the spatial relationship between actin-binding proteins such as α-actinin, tropomyosin and ADF/cofilin and possibly strengthening actin filaments by bundling.

  16. Stimulation of abdominal and upper thoracic muscles with surface electrodes for respiration and cough: Acute studies in adult canines.

    PubMed

    Walter, James S; Posluszny, Joseph; Dieter, Raymond; Dieter, Robert S; Sayers, Scott; Iamsakul, Kiratipath; Staunton, Christine; Thomas, Donald; Rabbat, Mark; Singh, Sanjay

    2018-05-01

    To optimize maximal respiratory responses with surface stimulation over abdominal and upper thorax muscles and using a 12-Channel Neuroprosthetic Platform. Following instrumentation, six anesthetized adult canines were hyperventilated sufficiently to produce respiratory apnea. Six abdominal tests optimized electrode arrangements and stimulation parameters using bipolar sets of 4.5 cm square electrodes. Tests in the upper thorax optimized electrode locations, and forelimb moment was limited to slight-to-moderate. During combined muscle stimulation tests, the upper thoracic was followed immediately by abdominal stimulation. Finally, a model of glottal closure for cough was conducted with the goal of increased peak expiratory flow. Optimized stimulation of abdominal muscles included three sets of bilateral surface electrodes located 4.5 cm dorsal to the lateral line and from the 8 th intercostal space to caudal to the 13 th rib, 80 or 100 mA current, and 50 Hz stimulation frequency. The maximal expired volume was 343 ± 23 ml (n=3). Optimized upper thorax stimulation included a single bilateral set of electrodes located over the 2 nd interspace, 60 to 80 mA, and 50 Hz. The maximal inspired volume was 304 ± 54 ml (n=4). Sequential stimulation of the two muscles increased the volume to 600 ± 152 ml (n=2), and the glottal closure maneuver increased the flow. Studies in an adult canine model identified optimal surface stimulation methods for upper thorax and abdominal muscles to induce sufficient volumes for ventilation and cough. Further study with this neuroprosthetic platform is warranted.

  17. Surgical desensitisation of the mechanoreceptors in Müller's muscle relieves chronic tension-type headache caused by tonic reflexive contraction of the occipitofrontalis muscle in patients with aponeurotic blepharoptosis.

    PubMed

    Matsuo, Kiyoshi; Ban, Ryokuya

    2013-02-01

    Proprioceptively innervated intramuscular connective tissues in Müller's muscle function as exterior mechanoreceptors to induce reflex contraction of the levator and occipitofrontalis muscles. In aponeurotic blepharoptosis, since the levator aponeurosis is disinserted from the tarsus, stretching of the mechanoreceptors in Müller's muscle is increased even on primary gaze to induce phasic and tonic reflexive contraction of the occipitofrontalis muscle. It was hypothesised that in certain patients with aponeurotic blepharoptosis, the presence of tonic reflexive contraction of the occipitofrontalis muscle due to the sensitised mechanoreceptors in Müller's muscle, can cause chronic tension-type headache (CTTH) associated with occipitofrontalis tenderness. To verify this hypothesis, this study evaluated (1) what differentiates patients with CTTH from patients without CTTH, (2) how pharmacological contraction of Müller's smooth muscle fibres as a method for desensitising the mechanoreceptors in Müller's muscle affects electromyographic activity of the frontalis muscle, and (3) how surgical aponeurotic reinsertion to desensitise the mechanoreceptors in Müller's muscle electromyographically or subjectively affects activities of the occipitofrontalis muscle or CTTH. It was found that patients had sustained CTTH when light eyelid closure did not markedly reduce eyebrow elevation. However, pharmacological contraction of Müller's smooth muscle fibres or surgery to desensitise the mechanoreceptor electromyographically reduced the tonic contraction of the occipitofrontalis muscle on primary gaze and subjectively relieved aponeurotic blepharoptosis-associated CTTH. Over-stretching of the mechanoreceptors in Müller's muscle on primary gaze may induce CTTH due to tonic reflexive contraction of the occipitofrontalis muscle. Therefore, surgical desensitisation of the mechanoreceptors in Müller's muscle appears to relieve CTTH.

  18. Ketamine relaxes airway smooth muscle contracted by endothelin.

    PubMed

    Sato, T; Matsuki, A; Zsigmond, E K; Rabito, S F

    1997-04-01

    Endothelins (ETs) are synthesized not only in vascular endothelial cells but also in airway epithelial cells. Increased ET-1 has been demonstrated in bronchial epithelium of asthmatic patients, and, in severe asthma attacks, ET-1 increases in plasma and bronchoalveolar lavage fluid. In this study, we investigated whether ketamine (KET) relaxes ET-induced tracheal contractions. Female guinea pigs were killed with an overdose of pentobarbital. The trachea was removed and cut spirally into two strips that were mounted in an organ bath filled with Krebs-bicarbonate buffer. The response of each strip to 10(-7) M carbachol was taken as 100% contraction to which the response to ET was referred. The contribution of the epithelium to the relaxant effect of KET was studied in denuded tracheae or in the presence of 5 x 10(-5) M indomethacin. ET-1 (3 x 10(-8) M) induced contractions that were 76 +/- 3% of those induced by carbachol. KET reversed the response to ET-1 in a dose-dependent fashion. Similarly, ET-2 (3 x 10(-8) M) induced contractions that were 74 +/- 5% of those induced by carbachol, and KET also reversed this response in a dose-dependent manner. In epithelium-denuded strips, ET-1 induced contractions that were 104 +/- 3% of those induced by carbachol, and KET still reversed this response. The tonic phase of the response to ET-1 was equal (100 +/- 6%) to the response to carbachol, and KET did not affect it significantly. In the presence of ryanodine, KET reduced the ET-1-induced contraction from 67 +/- 2% to 36 +/- 3.%, P < 0.01. In the presence of nicardipine, KET also inhibited the ET-1-induced contraction. We conclude that KET relaxes the tracheal smooth muscle contracted by ETs via a mechanism that is independent of the tracheal epithelium. The relaxant effect of KET on the ET-induced contraction of the trachealis muscle is not dependent upon blockade of 1) sarcolemma influx of Ca2+ through the dihydropyridine Ca2+ channel or 2) the release of intracellular Ca2

  19. Capacity of Rectified Vestibular Evoked Myogenic Potential in Correcting Asymmetric Muscle Contraction Power

    PubMed Central

    Kim, Kun Woo; Jung, Jae Yun; Lee, Jeong Hyun

    2013-01-01

    Objectives Rectified vestibular evoked myogenic potential (rVEMP) is new method that simultaneously measures the muscle contraction power during VEMP recordings. Although there are a few studies that have evaluated the effect of the rVEMP, there is no study that has evaluated the capacity of rVEMP during asymmetrical muscle contraction. Methods Thirty VEMP measurements were performed among 20 normal subjects (mean age, 28.2±2.1 years; male, 16). VEMP was measured in the supine position. The head was turned to the right side by 0°, 15°, 30°, and 45° and the VEMPs were recorded in each position. The interaural amplitude difference (IAD) ratio was calculated by the conventional non-rectified VEMP (nVEMP) and rVEMP. Results The nVEMP IAD increased significantly according to increasing neck rotation. The IAD in rVEMP was almost similar from 0° to 30°. However, the IAD was significantly larger than the other positions when the neck was rotated 45°. When IAD during 0° was set as a standard, the IAD of the rVEMP was significantly smaller that the nVEMP only during the 30°rotaion. Conclusion Rectified VEMP is capable of correcting asymmetrical muscle contraction power. In contrast, it cannot correct the asymmetry if muscle contraction power asymmetry is 44.8% or larger. Also, it is not necessary if muscle contraction power asymmetry is 22.5% or smaller. PMID:24353859

  20. Smooth muscle neurokinin-2 receptors mediate contraction in human saphenous veins.

    PubMed

    Mechiche, Hakima; Grassin-Delyle, Stanislas; Pinto, Francisco M; Buenestado, Amparo; Candenas, Luz; Devillier, Philippe

    2011-05-01

    Substance P (SP) and neurokinin A (NKA) are members of the tachykinin peptides family. SP causes endothelial-dependant relaxation but the contractile response to tachykinins in human vessels remains unknown. The objective was to assess the expression and the contractile effects of tachykinins and their receptors in human saphenous veins (SV). Tachykinin expression was assessed with RT-PCR, tachykinin receptors expression with RT-PCR and immunohistochemistry, and functional studies were performed in organ bath. Transcripts of all tachykinin and tachykinin receptor genes were found in SV. NK(1)-receptors were localized in both endothelial and smooth muscle layers of undistended SV, whereas they were only found in smooth muscle layers of varicose SV. The expression of NK(2)- and NK(3)-receptors was limited to the smooth muscle in both preparations. NKA induced concentration-dependent contractions in about half the varicose SV. Maximum effect reached 27.6±5.5% of 90 mM KCl and the pD(2) value was 7.3±0.2. NKA also induced the contraction of undistended veins from bypass and did not cause the relaxation of these vessels after precontraction. The NK(2)-receptor antagonist SR48968 abolished the contraction induced by NKA, and a rapid desensitization of the NK(2)-receptor was observed. In varicose SV, the agonists specific to NK(1)- or NK(3)-receptors did not cause either contraction or relaxation. The stimulation of smooth muscle NK(2)-receptors can induce the contraction of human SV. As SV is richly innervated, tachykinins may participate in the regulation of the tone in this portion of the low pressure vascular system. Copyright © 2011 Elsevier Ltd. All rights reserved.

  1. Electromyographic analysis of upper body, lower body, and abdominal muscles during advanced Swiss ball exercises.

    PubMed

    Marshall, Paul W M; Desai, Imtiaz

    2010-06-01

    Although there is now some evidence examining the use of a Swiss ball during core stability and resistance exercises, this has commonly been performed using basic or isometric exercises. There is currently no evidence examining more advanced Swiss ball exercises. The purpose of this study was to determine whether or not muscle activity measured during advanced Swiss ball exercises was at an approximate intensity recommended for strength or endurance training in advanced, or novice individuals. After a familiarization session, 14 recreationally active subjects performed 6 different "advanced" Swiss ball exercises in a randomized order. The primary dependent variables in this study were the activity levels collected from anterior deltoid, pectoralis major, rectus abdominis (RA), external obliques, lumbar erector spinae, vastus lateralis (VL), and biceps femoris using surface electromyography. All signals were normalized to maximal voluntary isometric contractions performed before testing for each muscle. The results of this study showed that the Swiss ball roll elicited muscle activity in triceps brachii (72.5+/-32.4%) and VL (83.6+/-44.2%) commensurate with the intensity recommended for strength exercises in advanced trainers. Rectus abdominis activity was greatest during the bridge exercise (61.3+/-28.5%, pmuscle activity commensurate with a strength training effect. The remainder of the exercises elicited abdominal activity that would require a higher number of repetitions to be performed for an endurance training adaptation. Although this study has provided evidence for one advanced Swiss ball exercise providing a significant whole-body stimulus, the practical difficulty and risks of performing these more complicated Swiss ball exercises may outweigh potential benefits.

  2. A Novel Soft Pneumatic Artificial Muscle with High-Contraction Ratio.

    PubMed

    Han, Kwanghyun; Kim, Nam-Ho; Shin, Dongjun

    2018-06-20

    There is a growing interest in soft actuators for human-friendly robotic applications. However, it is very challenging for conventional soft actuators to achieve both a large working distance and high force. To address this problem, we present a high-contraction ratio pneumatic artificial muscle (HCRPAM), which has a novel actuation concept. The HCRPAM can contract substantially while generating a large force suitable for a wide range of robotic applications. Our proposed prototyping method allows for an easy and quick fabrication, considering various design variables. We derived a mathematical model using a virtual work principle, and validated the model experimentally. We conducted simulations for the design optimization using this model. Our experimental results show that the HCRPAM has a 183.3% larger contraction ratio and 37.1% higher force output than the conventional pneumatic artificial muscle (McKibben muscle). Furthermore, the actuator has a compatible position tracking performance of 1.0 Hz and relatively low hysteresis error of 4.8%. Finally, we discussed the controllable bending characteristics of the HCRPAM, which uses heterogeneous materials and has an asymmetrical structure to make it comfortable for a human to wear.

  3. Characterization of muscle contraction with second harmonic generation microscopy

    NASA Astrophysics Data System (ADS)

    Prent, Nicole

    Muscle cells have the ability to change length and generate force due to orchestrated action of myosin nanomotors that cause sliding of actin filaments along myosin filaments in the sarcomeres, the fundamental contractile units, of myocytes. The correlated action of hundreds of sarcomeres is needed to produce the myocyte contractions. This study probes the molecular structure of the myofilaments and investigates the movement correlations between sarcomeres during contraction. In this study, second harmonic generation (SHG) microscopy is employed for imaging striated myocytes. Myosin filaments in striated myocytes inherently have a nonzero second-order susceptibility, [special characters omitted] and therefore generate efficient SHG. Employing polarization-in polarization-out (PIPO) SHG microscopy allows for the accurate determination of the characteristic ratio, [special characters omitted] in birefringent myocytes, which describes the structure of the myosin filament. Analysis shows that the b value at the centre of the myosin filament, where the nonlinear dipoles are better aligned, is slightly lower than the value at the edges of the filament, where there is more disorder in orientation of the nonlinear dipoles from the myosin heads. Forced stretching of myocytes resulted in an SHG intensity increase with the elongation of the sarcomere. SHG microscopy captured individual sarcomeres during contraction, allowing for the measurement of sarcomere length (SL) and SHG intensity (SI) fluctuations. The fluctuations also revealed higher SHG intensity in elongated sarcomeres. The sarcomere synchronization model (SSM) for contracting and quiescent myocytes was developed, and experimentally verified for three cases (isolated cardiomyocyte, embryonic chicken cardiomyocyte, and larva myocyte). During contraction, the action of SLs and SIs between neighbouring sarcomeres partially correlated, whereas in quiescent myocytes the SLs show an anti-correlation and the SIs have no

  4. Evaluation of innate immune stimulating activity of polysaccharides using a silkworm (Bombyx mori) muscle contraction assay.

    PubMed

    Fujiyuki, T; Hamamoto, H; Ishii, K; Urai, M; Kataoka, K; Takeda, T; Shibata, S; Sekimizu, K

    2012-04-01

    In silkworm larvae, the mature form of paralytic peptide (PP), an insect cytokine, is produced from pro-PP in association with activation of innate immune responses, resulting in slow muscle contraction. We utilized this reaction, muscle contraction in silkworms coupled with innate immunity stimulation, to quantitatively measure the innate immune stimulating activity of various natural polysaccharides. β-Glucan of Gyrophora esculenta (GE-3), fucoidan from sporophyll of Undaria pinnatifida, and curldan induced silkworm muscle contraction. We further demonstrated that GE-3 had therapeutic effects on silkworms infected by baculovirus. Based on these findings, we propose that the silkworm muscle contraction assay is useful for screening substances that stimulate innate immunity before evaluating therapeutic effectiveness in mammals.

  5. Grounding after moderate eccentric contractions reduces muscle damage

    PubMed Central

    Brown, Richard; Chevalier, Gaétan; Hill, Michael

    2015-01-01

    Grounding a human to the earth has resulted in changes in the physiology of the body. A pilot study on grounding and eccentric contractions demonstrated shortened duration of pain, reduced creatine kinase (CK), and differences in blood parameters. This follow-up study was conducted to investigate the effects of grounding after moderate eccentric contractions on pain, CK, and complete blood counts. Thirty-two healthy young men were randomly divided into grounded (n=16) and sham-grounded (n=16) groups. On days 1 through 4, visual analog scale for pain evaluations and blood draws were accomplished. On day 1, the participants performed eccentric contractions of 200 half-knee bends. They were then grounded or sham-grounded to the earth for 4 hours on days 1 and 2. Both groups experienced pain on all posttest days. On day 2, the sham-grounded group experienced significant CK increase (P<0.01) while the CK of the grounded group did not increase significantly; the between-group difference was significant (P=0.04). There was also an increase in the neutrophils of the grounded group on day 3 (P=0.05) compared to the sham-grounded group. There was a significant increase in platelets in the grounded group on days 2 through 4. Grounding produced changes in CK and complete blood counts that were not shared by the sham-grounded group. Grounding significantly reduced the loss of CK from the injured muscles indicating reduced muscle damage. These results warrant further study on the effects of earthing on delayed onset muscle damage. PMID:26443876

  6. Muscle function and fatigability of trunk flexors in males and females.

    PubMed

    Deering, Rita E; Senefeld, Jonathon W; Pashibin, Tatyana; Neumann, Donald A; Hunter, Sandra K

    2017-01-01

    Optimal function of the abdominal muscles is necessary for several life functions including lifting and carrying tasks. Sex differences in strength and fatigability are established for many limb muscles and back extensor muscles, but it is unknown if sex differences exist for the abdominal muscles despite their functional importance. Eighteen females (24.3 ± 4.8 years) and 15 males (24.1 ± 6.6 years) performed (1) isometric trunk flexion maximal voluntary contractions (MVCs) in a range of trunk positions to establish a torque-angle curve and (2) submaximal (50% MVC), intermittent isometric contraction (6 s on, 4 s off) until task failure to determine fatigability of the trunk flexor muscles. Dual X-ray absorptiometry quantified body fat and lean mass. Physical activity levels were quantified with a questionnaire. Torque-angle curves, electromyography (EMG), MVC torque, and torque steadiness were compared with repeated measures ANOVA with sex as a between-subjects factor. For the torque-angle curve, MVC torque was reduced as the trunk angle increased toward flexion ( p  < 0.001). Males had greater MVC torque than females at the extended positions (31% difference), with no sex differences in torque in upright sitting ( p >  0.05). Time-to-task failure for the submaximal fatigability task in upright sitting was similar between males and females (12.4 ± 7 vs 10.5 ± 6 min). Time-to-task failure was positively associated with strength ( r  = 0.473, p  = 0.005) and self-reported physical activity ( r  = 0.456, p  = 0.030). Lean mass in the trunk was positively associated with trunk flexor strength ( r  = 0.378, p  = 0.011) and self-reported physical activity ( r  = 0.486, p  = 0.007). Finally, torque steadiness [coefficient of variation of torque (CV)] during submaximal isometric contractions decreased with contraction intensity and was similar for males and females across all intensities. Unlike many limb

  7. Skeletal muscle contractions uncoupled from gravitational loading directly increase cortical bone blood flow rates in vivo.

    PubMed

    Caulkins, Carrie; Ebramzadeh, Edward; Winet, Howard

    2009-05-01

    The direct and indirect effects of muscle contraction on bone microcirculation and fluid flow are neither well documented nor explained. However, skeletal muscle contractions may affect the acquisition and maintenance of bone via stimulation of bone circulatory and interstitial fluid flow parameters. The purposes of this study were to assess the effects of transcutaneous electrical neuromuscular stimulation (TENS)-induced muscle contractions on cortical bone blood flow and bone mineral content, and to demonstrate that alterations in blood flow could occur independently of mechanical loading and systemic circulatory mechanisms. Bone chamber implants were used in a rabbit model to observe real-time blood flow rates and TENS-induced muscle contractions. Video recording of fluorescent microspheres injected into the blood circulation was used to calculate changes in cortical blood flow rates. TENS-induced repetitive muscle contractions uncoupled from mechanical loading instantaneously increased cortical microcirculatory flow, directly increased bone blood flow rates by 130%, and significantly increased bone mineral content over 7 weeks. Heart rates and blood pressure did not significantly increase due to TENS treatment. Our findings suggest that muscle contraction therapies have potential clinical applications for improving blood flow to cortical bone in the appendicular skeleton. Copyright 2008 Orthopaedic Research Society

  8. Dynamic equilibration of airway smooth muscle contraction during physiological loading.

    PubMed

    Latourelle, Jeanne; Fabry, Ben; Fredberg, Jeffrey J

    2002-02-01

    Airway smooth muscle contraction is the central event in acute airway narrowing in asthma. Most studies of isolated muscle have focused on statically equilibrated contractile states that arise from isometric or isotonic contractions. It has recently been established, however, that muscle length is determined by a dynamically equilibrated state of the muscle in which small tidal stretches associated with the ongoing action of breathing act to perturb the binding of myosin to actin. To further investigate this phenomenon, we describe in this report an experimental method for subjecting isolated muscle to a dynamic microenvironment designed to closely approximate that experienced in vivo. Unlike previous methods that used either time-varying length control, force control, or time-invariant auxotonic loads, this method uses transpulmonary pressure as the controlled variable, with both muscle force and muscle length free to adjust as they would in vivo. The method was implemented by using a servo-controlled lever arm to load activated airway smooth muscle strips with transpulmonary pressure fluctuations of increasing amplitude, simulating the action of breathing. The results are not consistent with classical ideas of airway narrowing, which rest on the assumption of a statically equilibrated contractile state; they are consistent, however, with the theory of perturbed equilibria of myosin binding. This experimental method will allow for quantitative experimental evaluation of factors that were previously outside of experimental control, including sensitivity of muscle length to changes of tidal volume, changes of lung volume, shape of the load characteristic, loss of parenchymal support and inflammatory thickening of airway wall compartments.

  9. Size, History-Dependent, Activation and Three-Dimensional Effects on the Work and Power Produced During Cyclic Muscle Contractions.

    PubMed

    Ross, Stephanie A; Ryan, David S; Dominguez, Sebastian; Nigam, Nilima; Wakeling, James M

    2018-05-03

    Muscles undergo cycles of length change and force development during locomotion, and these contribute to their work and power production to drive body motion. Muscle fibres are typically considered to be linear actuators whose stress depends on their length, velocity, and activation state, and whose properties can be scaled up to explain the function of whole muscles. However, experimental and modelling studies have shown that a muscle's stress additionally depends on inactive and passive tissues within the muscle, the muscle's size, and its previous contraction history. These effects have not been tested under common sets of contraction conditions, especially the cyclic contractions that are typical of locomotion. Here we evaluate the relative effects of size, history-dependent, activation and three-dimensional effects on the work and power produced during cyclic contractions of muscle models. Simulations of muscle contraction were optimized to generate high power outputs: this resulted in the muscle models being largely active during shortening, and inactive during lengthening. As such, the history-dependent effects were dominated by force depression during simulated active shortening rather than force enhancement during active stretch. Internal work must be done to deform the muscle tissue, and to accelerate the internal muscle mass, resulting in reduced power and work that can be done on an external load. The effect of the muscle mass affects the scaling of muscle properties, with the inertial costs of contraction being relatively greater at larger sizes and lower activation levels.

  10. Different cortical activation patterns during voluntary eccentric and concentric muscle contractions: an fMRI study.

    PubMed

    Kwon, Yong-Hyun; Park, Ji-Won

    2011-01-01

    Concentric and eccentric muscle contractions have distinct differences in their neuromuscular and neurophysiologic characteristics. However, although many evidences regarding the features of these types of muscle contraction have emerged, there have been few neuroimaging studies to compare the two types of contractions. Therefore, we investigated whether cortical activity associated with eccentric contraction of the wrist extensors differed from that of concentric contraction, using functional MRI (fMRI). Fifteen right-handed healthy subjects were enrolled in this study. During 4 repeating blocks of eccentric and concentric muscle contraction paradigms, the brain was scanned with fMRI. The differences in the BOLD signal intensities during the performance of eccentric and concentric exercise were compared in the predetermined regions of interest. Our findings revealed that many cortical areas associated with motor performance were activated, including the primary motor area, the inferior parietal lobe, the pre-supplementary area (pre-SMA), the anterior cingulate cortex, the prefrontal area, and the cerebellum. In addition, lower signal intensities were seen in the right primary motor cortex and right cerebellum during eccentric contractions compared with concentric contractions, whereas higher signal intensities were detected in other cortical areas during eccentric contractions. In the study, we demonstrated that eccentric and concentric muscle contractions induced quite different patterns of cortical activity respectively. These findings might be attributed to different strategy of neuro-motor processing and a higher level of cognitive demand for the performance of motor task with a higher degree of difficulty such as that required during eccentric contractions in comparison of concentric contractions.

  11. Impact of Isometric Contraction of Anterior Cervical Muscles on Cervical Lordosis.

    PubMed

    Fedorchuk, Curtis A; McCoy, Matthew; Lightstone, Douglas F; Bak, David A; Moser, Jacque; Kubricht, Brett; Packer, John; Walton, Dustin; Binongo, Jose

    2016-09-01

    This study investigates the impact of isometric contraction of anterior cervical muscles on cervical lordosis. 29 volunteers were randomly assigned to an anterior head translation (n=15) or anterior head flexion (n=14) group. Resting neutral lateral cervical x-rays were compared to x-rays of sustained isometric contraction of the anterior cervical muscles producing anterior head translation or anterior head flexion. Paired sample t-tests indicate no significant difference between pre and post anterior head translation or anterior head flexion. Analysis of variance suggests that gender and peak force were not associated with change in cervical lordosis. Chamberlain's to atlas plane line angle difference was significantly associated with cervical lordosis difference during anterior head translation (p=0.01). This study shows no evidence that hypertonicity, as seen in muscle spasms, of the muscles responsible for anterior head translation and anterior head flexion have a significant impact on cervical lordosis.

  12. Eccentric Contraction-Induced Muscle Injury: Reproducible, Quantitative, Physiological Models to Impair Skeletal Muscle’s Capacity to Generate Force

    PubMed Central

    Call, Jarrod A.; Lowe, Dawn A.

    2018-01-01

    In order to investigate the molecular and cellular mechanisms of muscle regeneration an experimental injury model is required. Advantages of eccentric contraction-induced injury are that it is a controllable, reproducible, and physiologically relevant model to cause muscle injury, with injury being defined as a loss of force generating capacity. While eccentric contractions can be incorporated into conscious animal study designs such as downhill treadmill running, electrophysiological approaches to elicit eccentric contractions and examine muscle contractility, for example before and after the injurious eccentric contractions, allows researchers to circumvent common issues in determining muscle function in a conscious animal (e.g., unwillingness to participate). Herein, we describe in vitro and in vivo methods that are reliable, repeatable, and truly maximal because the muscle contractions are evoked in a controlled, quantifiable manner independent of subject motivation. Both methods can be used to initiate eccentric contraction-induced injury and are suitable for monitoring functional muscle regeneration hours to days to weeks post-injury. PMID:27492161

  13. Role of the medial medullary reticular formation in relaying vestibular signals to the diaphragm and abdominal muscles

    NASA Technical Reports Server (NTRS)

    Mori, R. L.; Bergsman, A. E.; Holmes, M. J.; Yates, B. J.

    2001-01-01

    Changes in posture can affect the resting length of respiratory muscles, requiring alterations in the activity of these muscles if ventilation is to be unaffected. Recent studies have shown that the vestibular system contributes to altering respiratory muscle activity during movement and changes in posture. Furthermore, anatomical studies have demonstrated that many bulbospinal neurons in the medial medullary reticular formation (MRF) provide inputs to phrenic and abdominal motoneurons; because this region of the reticular formation receives substantial vestibular and other movement-related input, it seems likely that medial medullary reticulospinal neurons could adjust the activity of respiratory motoneurons during postural alterations. The objective of the present study was to determine whether functional lesions of the MRF affect inspiratory and expiratory muscle responses to activation of the vestibular system. Lidocaine or muscimol injections into the MRF produced a large increase in diaphragm and abdominal muscle responses to vestibular stimulation. These vestibulo-respiratory responses were eliminated following subsequent chemical blockade of descending pathways in the lateral medulla. However, inactivation of pathways coursing through the lateral medulla eliminated excitatory, but not inhibitory, components of vestibulo-respiratory responses. The simplest explanation for these data is that MRF neurons that receive input from the vestibular nuclei make inhibitory connections with diaphragm and abdominal motoneurons, whereas a pathway that courses laterally in the caudal medulla provides excitatory vestibular inputs to these motoneurons.

  14. Slipping rib syndrome: a place for sonography in the diagnosis of a frequently overlooked cause of abdominal or low thoracic pain.

    PubMed

    Meuwly, Jean-Yves; Wicky, Stephan; Schnyder, Pierre; Lepori, Domenico

    2002-03-01

    To describe the sonographic appearance of a poorly recognized cause of low thoracic or upper abdominal pain. Three sonographic descriptions of slipping rib syndrome are presented. The 3 patients had abnormal mobility of a cartilaginous rib, which could slip over an adjacent rib during abdominal muscle contraction. Slipping rib syndrome should be considered in patients with histories of upper abdominal or low thoracic pain of unknown origin. We suggest that high-resolution sonography of the costal margin should be added to abdominal sonography in cases of nonspecific abdominal pain.

  15. Role of reactive oxygen species in contraction-mediated glucose transport in mouse skeletal muscle

    PubMed Central

    Sandström, Marie E; Zhang, Shi-Jin; Bruton, Joseph; Silva, José P; Reid, Michael B; Westerblad, Håkan; Katz, Abram

    2006-01-01

    Exercise increases glucose transport into skeletal muscle via a pathway that is poorly understood. We investigated the role of endogenously produced reactive oxygen species (ROS) in contraction-mediated glucose transport. Repeated contractions increased 2-deoxyglucose (2-DG) uptake roughly threefold in isolated, mouse extensor digitorum longus (fast-twitch) muscle. N-Acetylcysteine (NAC), a non-specific antioxidant, inhibited contraction-mediated 2-DG uptake by ∼50% (P < 0.05 versus control values), but did not significantly affect basal 2-DG uptake or the uptake induced by insulin, hypoxia or 5-aminoimidazole-4-carboxamide-1-β-d-ribofuranoside (AICAR, which mimics AMP-mediated activation of AMP-activated protein kinase, AMPK). Ebselen, a glutathione peroxidase mimetic, also inhibited contraction-mediated 2-DG uptake (by almost 60%, P < 0.001 versus control values). Muscles from mice overexpressing Mn2+-dependent superoxide dismutase, which catalyses H2O2 production from superoxide anions, exhibited a ∼25% higher rate of contraction-mediated 2-DG uptake versus muscles from wild-type control mice (P < 0.05). Exogenous H2O2 induced oxidative stress, as judged by an increase in the [GSSG]/[GSH + GSSG] (reduced glutathione + oxidized glutathione) ratio to 2.5 times control values, and this increase was substantially blocked by NAC. Similarly, NAC significantly attenuated contraction-mediated oxidative stress as judged by measurements of glutathione status and the intracellular ROS level with the fluorescent indicator 5-(and-6)-chloromethyl-2′,7′-dichlorodihydrofluorescein (P < 0.05). Finally, contraction increased AMPK activity and phosphorylation ∼10-fold, and NAC blocked ∼50% of these changes. These data indicate that endogenously produced ROS, possibly H2O2 or its derivatives, play an important role in contraction-mediated activation of glucose transport in fast-twitch muscle. PMID:16777943

  16. Effects of magnesium sulfate on airway smooth muscle contraction in rats.

    PubMed

    Betul Altinisik, Hatice; Kirdemir, Pakize; Altinisik, Ugur; Gokalp, Osman

    2016-08-01

    Aim To investigate the effect of magnesium sulfate (MgSO4) at different doses on isolated tracheal smooth muscle contraction in rats induced by different mechanisms. Methods Twelve rats' tracheas were placed into organ bath. Consecutively, acetylcholine (10-6,10-5,10-4 M), histamine(10-8,10-5,10-3 M) and KCl (30,60 mM) solutions was administered for contractions. MgSO4 from 10-4 to 10-1 M concentrations were subsequently administered after each constrictive agent and relaxation degrees were recorded. Results In the acetylcholine and KCl groups, dose dependent strong contractions were observed, but not in the histamine group and that group was excluded. Significant relaxation occurred with gradually increasing doses of MgSO4. In the high dose KCl group, a slight increase in contractions after the administration of 10-4 and 10-3 M MgSO4 was recorded. Conclusion We suggest that MgSO4 is effective in relaxing airway smooth muscle contractions caused by different factors; however, it must be considered that low doses of MgSO4 may only lead to a slight increase in contractions. Copyright© by the Medical Assotiation of Zenica-Doboj Canton.

  17. Muscle shear elastic modulus is linearly related to muscle torque over the entire range of isometric contraction intensity.

    PubMed

    Ateş, Filiz; Hug, François; Bouillard, Killian; Jubeau, Marc; Frappart, Thomas; Couade, Mathieu; Bercoff, Jeremy; Nordez, Antoine

    2015-08-01

    Muscle shear elastic modulus is linearly related to muscle torque during low-level contractions (<60% of Maximal Voluntary Contraction, MVC). This measurement can therefore be used to estimate changes in individual muscle force. However, it is not known if this relationship remains valid for higher intensities. The aim of this study was to determine: (i) the relationship between muscle shear elastic modulus and muscle torque over the entire range of isometric contraction and (ii) the influence of the size of the region of interest (ROI) used to average the shear modulus value. Ten healthy males performed two incremental isometric little finger abductions. The joint torque produced by Abductor Digiti Minimi was considered as an index of muscle torque and elastic modulus. A high coefficient of determination (R(2)) (range: 0.86-0.98) indicated that the relationship between elastic modulus and torque can be accurately modeled by a linear regression over the entire range (0% to 100% of MVC). The changes in shear elastic modulus as a function of torque were highly repeatable. Lower R(2) values (0.89±0.13 for 1/16 of ROI) and significantly increased absolute errors were observed when the shear elastic modulus was averaged over smaller ROI, half, 1/4 and 1/16 of the full ROI) than the full ROI (mean size: 1.18±0.24cm(2)). It suggests that the ROI should be as large as possible for accurate measurement of muscle shear modulus. Copyright © 2015 Elsevier Ltd. All rights reserved.

  18. Inhibition of RhoA/Rho kinase pathway and smooth muscle contraction by hydrogen sulfide.

    PubMed

    Nalli, Ancy D; Wang, Hongxia; Bhattacharya, Sayak; Blakeney, Bryan A; Murthy, Karnam S

    2017-10-01

    Hydrogen sulfide (H 2 S) plays an important role in smooth muscle relaxation. Here, we investigated the expression of enzymes in H 2 S synthesis and the mechanism regulating colonic smooth muscle function by H 2 S. Expression of cystathionine-γ-lyase (CSE), but not cystathionine-β-synthase (CBS), was identified in the colonic smooth muscle of rabbit, mouse, and human. Carbachol (CCh)-induced contraction in rabbit muscle strips and isolated muscle cells was inhibited by l-cysteine (substrate of CSE) and NaHS (an exogenous H 2 S donor) in a concentration-dependent fashion. H 2 S induced S-sulfhydration of RhoA that was associated with inhibition of RhoA activity. CCh-induced Rho kinase activity also was inhibited by l-cysteine and NaHS in a concentration-dependent fashion. Inhibition of CCh-induced contraction by l-cysteine was blocked by the CSE inhibitor, dl-propargylglycine (DL-PPG) in dispersed muscle cells. Inhibition of CCh-induced Rho kinase activity by l-cysteine was blocked by CSE siRNA in cultured cells and DL-PPG in dispersed muscle cells. Stimulation of Rho kinase activity and muscle contraction in response to CCh was also inhibited by l-cysteine or NaHS in colonic muscle cells from mouse and human. Collectively, our studies identified the expression of CSE in colonic smooth muscle and determined that sulfhydration of RhoA by H 2 S leads to inhibition of RhoA and Rho kinase activities and muscle contraction. The mechanism identified may provide novel therapeutic approaches to mitigate gastrointestinal motility disorders. © 2017 The Authors. Pharmacology Research & Perspectives published by John Wiley & Sons Ltd, British Pharmacological Society and American Society for Pharmacology and Experimental Therapeutics.

  19. Effect of neuromuscular electrical stimulation on motor cortex excitability upon release of tonic muscle contraction.

    PubMed

    Sugawara, Kenichi; Tanabe, Shigeo; Suzuki, Tomotaka; Higashi, Toshio

    The aim of the present study was to investigate the neurophysiological triggers underlying muscle relaxation from the contracted state, and to examine the mechanisms involved in this process and their subsequent modification by neuromuscular electrical stimulation (NMES). Single-pulse transcranial magnetic stimulation (TMS) was used to produce motor-evoked potentials (MEPs) and short-interval intracortical inhibition (SICI) in 23 healthy participants, wherein motor cortex excitability was examined at the onset of voluntary muscle relaxation following a period of voluntary tonic muscle contraction. In addition, the effects of afferent input on motor cortex excitability, as produced by NMES during muscle contraction, were examined. In particular, two NMES intensities were used for analysis: 1.2 times the sensory threshold and 1.2 times the motor threshold (MT). Participants were directed to execute constant wrist extensions and to release muscle contraction in response to an auditory "GO" signal. MEPs were recorded from the flexor carpi radialis (FCR) and extensor carpi radialis (ECR) muscles, and TMS was applied at three different time intervals (30, 60, and 90 ms) after the "GO" signal. Motor cortex excitability was greater during voluntary ECR and FCR relaxation using high-intensity NMES, and relaxation time was decreased. Each parameter differed significantly between 30 and 60 ms. Moreover, in both muscles, SICI was larger in the presence than in the absence of NMES. Therefore, the present findings suggest that terminating a muscle contraction triggers transient neurophysiological mechanisms that facilitate the NMES-induced modulation of cortical motor excitability in the period prior to muscle relaxation. High-intensity NMES might facilitate motor cortical excitability as a function of increased inhibitory intracortical activity, and therefore serve as a transient trigger for the relaxation of prime mover muscles in a therapeutic context.

  20. Dynamic contraction behaviour of pneumatic artificial muscle

    NASA Astrophysics Data System (ADS)

    Doumit, Marc D.; Pardoel, Scott

    2017-07-01

    The development of a dynamic model for the Pneumatic Artificial Muscle (PAM) is an imperative undertaking for understanding and analyzing the behaviour of the PAM as a function of time. This paper proposes a Newtonian based dynamic PAM model that includes the modeling of the muscle geometry, force, inertia, fluid dynamic, static and dynamic friction, heat transfer and valve flow while ignoring the effect of bladder elasticity. This modeling contribution allows the designer to predict, analyze and optimize PAM performance prior to its development. Thus advancing successful implementations of PAM based powered exoskeletons and medical systems. To date, most muscle dynamic properties are determined experimentally, furthermore, no analytical models that can accurately predict the muscle's dynamic behaviour are found in the literature. Most developed analytical models adequately predict the muscle force in static cases but neglect the behaviour of the system in the transient response. This could be attributed to the highly challenging task of deriving such a dynamic model given the number of system elements that need to be identified and the system's highly non-linear properties. The proposed dynamic model in this paper is successfully simulated through MATLAB programing and validated the pressure, contraction distance and muscle temperature with experimental testing that is conducted with in-house built prototype PAM's.

  1. Heat production during contraction in skeletal muscle of hypothyroid mice

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Leijendekker, W.J.; van Hardeveld, C.; Elzinga, G.

    1987-08-01

    The effect of hypothyroidism on tension-independent and -dependent heat produced during a twitch and a tetanic contraction of extensor digitorum longus (EDL) and soleus muscle of mice was examined. The amount of heat produced during a twitch and the rate of heat development during a tetanus of EDL and soleus were measured at and above optimal length. The effect of hypothyroidism on force production was <30%. Straight lines were used to fit the relation between heat production and force. Hypothyroidism significantly decreases tension-independent heat during contraction of EDL and soleus muscle. Because the tension-independent heat is considered to be relatedmore » to the Ca{sup 2+} cycling, these findings suggest that ATP splitting due to the Ca{sup 2+} cycling is reduced in hypothyroid mice. This conclusion was strengthened by the observation that the oxalate-supported {sup 45}Ca{sup 2+}-uptake activity and {sup 45}Ca{sup 2+}-loading capacity of muscle homogenates from hypothyroid mice were reduced, respectively, to 51 and to 65% in soleus and to 63 and 73% in EDL muscle as compared with euthyroid mice. The tension-dependent rate of heat development during a tetanus was also decreased in soleus muscle of hypothyroid mice. This suggests a lower rate of ATP hydrolysis related to cross-bridge cycling in this muscle due to the hypothyroid state.« less

  2. Analysis of Two Methods of Isometric Muscle Contractions During the Anti-G Straining Maneuver

    DTIC Science & Technology

    2003-05-01

    contractions were not statistically different with regards to MAP and CO. Therefore, both forms of isometric contractions may be potentially useful when performing the muscle contraction portion of the AGSM.

  3. Fatigue and recovery from dynamic contractions in men and women differ for arm and leg muscles.

    PubMed

    Senefeld, Jonathon; Yoon, Tejin; Bement, Marie Hoeger; Hunter, Sandra K

    2013-09-01

    Whether there is a gender difference in fatigue and recovery from maximal velocity fatiguing contractions and across muscles is not understood. Sixteen men and 19 women performed 90 isotonic contractions at maximal voluntary shortening velocity (maximal velocity concentric contractions, MVCC) with the elbow flexor and knee extensor muscles (separate days) at a load equivalent to 20% maximal voluntary isometric contraction (MVIC). Power (from MVCCs) decreased similarly for men and women for both muscles (P > 0.05). Men and women had similar declines in MVIC of elbow flexors, but men had greater reductions in knee extensor MVIC force and MVIC electromyogram activity than women (P < 0.05). The decline in MVIC and power was greater, and force recovery was slower for the elbow flexors compared with knee extensors. The gender difference in muscle fatigue often observed during isometric tasks was diminished during fast dynamic contractions for upper and lower limb muscles. Copyright © Published 2013 by Wiley Periodicals, Inc. This article is a US Government wmusork and, as such, is in the public domain in the United States of America.

  4. Increase in endothelial cell Ca2+ in response to mouse cremaster muscle contraction

    PubMed Central

    Duza, Tasmia; Sarelius, Ingrid H

    2004-01-01

    We addressed the role of endothelial cells (ECs) in metabolic dilatation of skeletal muscle arterioles in anaesthetized mice in situ. Electrical field stimulation was used to contract the cremaster muscle for 15 s at 30 Hz. Diameter was observed using bright field microscopy. In controls, muscle contraction produced a 15.7 ± 1.5 μm dilatation from a baseline of 17.4 ± 1.6 μm. Endothelial denudation (−EC) via intraluminal perfusion of air abolished this response (1.6 ± 1.2 μm in −EC, P < 0.05), identifying endothelium as the primary vascular cell type initiating the dilatation. To investigate the role of EC Ca2+ in metabolic dilatation, arteriolar ECs were loaded with Fluo-4 AM or BAPTA AM by intraluminal perfusion, after which blood flow was re-established. Ca2+ activity of individual ECs was monitored as a function of change from baseline fluorescence using confocal microscopy. In ECs, whole cell Ca2+ increased (>10%, P < 0.05) during muscle contraction, and localized Ca2+ transients were increased (>20%, P < 0.05) during the first minute after contraction. Chelation of EC Ca2+ abolished the dilatations in response to muscle contraction (1.1 ± 0.7 μm, P < 0.05). Inhibition of P1 purinergic receptors (with xanthine amine congener) did not alter the rate of onset of the dilatation (P > 0.05) but decreased its magnitude immediately post stimulation (7.1 ± 0.9 μm, P < 0.05) and during recovery. These findings demonstrate obligatory roles for endothelium and EC Ca2+ during metabolic dilatation in intact arterioles. Furthermore, they suggest that at least two separate pathways mediate the local response, one of which involves stimulation of endothelial P1 purinergic receptors via endogenous adenosine produced during muscle activity. PMID:14694141

  5. The effect of muscle contraction level on the cervical vestibular evoked myogenic potential (cVEMP): usefulness of amplitude normalization.

    PubMed

    Bogle, Jamie M; Zapala, David A; Criter, Robin; Burkard, Robert

    2013-02-01

    The cervical vestibular evoked myogenic potential (cVEMP) is a reflexive change in sternocleidomastoid (SCM) muscle contraction activity thought to be mediated by a saccular vestibulo-collic reflex. CVEMP amplitude varies with the state of the afferent (vestibular) limb of the vestibulo-collic reflex pathway, as well as with the level of SCM muscle contraction. It follows that in order for cVEMP amplitude to reflect the status of the afferent portion of the reflex pathway, muscle contraction level must be controlled. Historically, this has been accomplished by volitionally controlling muscle contraction level either with the aid of a biofeedback method, or by an a posteriori method that normalizes cVEMP amplitude by the level of muscle contraction. A posteriori normalization methods make the implicit assumption that mathematical normalization precisely removes the influence of the efferent limb of the vestibulo-collic pathway. With the cVEMP, however, we are violating basic assumptions of signal averaging: specifically, the background noise and the response are not independent. The influence of this signal-averaging violation on our ability to normalize cVEMP amplitude using a posteriori methods is not well understood. The aims of this investigation were to describe the effect of muscle contraction, as measured by a prestimulus electromyogenic estimate, on cVEMP amplitude and interaural amplitude asymmetry ratio, and to evaluate the benefit of using a commonly advocated a posteriori normalization method on cVEMP amplitude and asymmetry ratio variability. Prospective, repeated-measures design using a convenience sample. Ten healthy adult participants between 25 and 61 yr of age. cVEMP responses to 500 Hz tone bursts (120 dB pSPL) for three conditions describing maximum, moderate, and minimal muscle contraction. Mean (standard deviation) cVEMP amplitude and asymmetry ratios were calculated for each muscle-contraction condition. Repeated measures analysis of variance

  6. Enkephalinase inhibitor potentiates substance P- and capsaicin-induced bronchial smooth muscle contractions in humans.

    PubMed

    Honda, I; Kohrogi, H; Yamaguchi, T; Ando, M; Araki, S

    1991-06-01

    To determine the roles of endogenously released tachykinins (substance P, neurokinins A and B) in human bronchial tissues, and to determine the roles of enkephalinase (neutral endopeptidase, E.C. 3.4.24.11) in regulating the effects of the tachykinins, we studied the effects of substance P and capsaicin, which releases tachykinins, on human bronchial smooth muscle contraction in the presence or absence of enkephalinase inhibitor phosphoramidon in vitro. Substance P alone caused human bronchial smooth muscle contraction at 10(-6) M or more. Phosphoramidon (10(-7) to 10(-5) M) potentiated the substance P-induced contraction in a dose-dependent fashion, and phosphoramidon shifted the dose-response curve to lower concentrations. Capsaicin (10(-5) or 10(-4) M) alone caused bronchial smooth muscle contraction in four tissues from nine patients. After the contraction by capsaicin reached a plateau, phosphoramidon (10(-5) M) increased and prolonged the contraction significantly. Furthermore, pretreatment of bronchial tissues with phosphoramidon (10(-5) M) potentiated capsaicin-induced contraction in all tissues from five patients. Phosphoramidon (10(-5) M) shifted the dose-response curve to capsaicin to lower concentrations more than 1 log unit. Captopril did not alter the contractile response to substance P, suggesting that angiotensin-converting enzyme does not regulate the contractile response to substance P in human bronchial smooth muscle in vitro. These results suggest that enkephalinase regulates the contractile effects of exogenous substance P and endogenous substances, probably tachykinins, released by capsaicin in the human bronchus.

  7. Mechanical effects of muscle contraction increase intravascular ATP draining quiescent and active skeletal muscle in humans

    PubMed Central

    Crecelius, Anne R.; Kirby, Brett S.; Richards, Jennifer C.

    2013-01-01

    Intravascular adenosine triphosphate (ATP) evokes vasodilation and is implicated in the regulation of skeletal muscle blood flow during exercise. Mechanical stresses to erythrocytes and endothelial cells stimulate ATP release in vitro. How mechanical effects of muscle contractions contribute to increased plasma ATP during exercise is largely unexplored. We tested the hypothesis that simulated mechanical effects of muscle contractions increase [ATP]venous and ATP effluent in vivo, independent of changes in tissue metabolic demand, and further increase plasma ATP when superimposed with mild-intensity exercise. In young healthy adults, we measured forearm blood flow (FBF) (Doppler ultrasound) and plasma [ATP]v (luciferin-luciferase assay), then calculated forearm ATP effluent (FBF×[ATP]v) during rhythmic forearm compressions (RFC) via a blood pressure cuff at three graded pressures (50, 100, and 200 mmHg; Protocol 1; n = 10) and during RFC at 100 mmHg, 5% maximal voluntary contraction rhythmic handgrip exercise (RHG), and combined RFC + RHG (Protocol 2; n = 10). [ATP]v increased from rest with each cuff pressure (range 144–161 vs. 64 ± 13 nmol/l), and ATP effluent was graded with pressure. In Protocol 2, [ATP]v increased in each condition compared with rest (RFC: 123 ± 33; RHG: 51 ± 9; RFC + RHG: 96 ± 23 vs. Mean Rest: 42 ± 4 nmol/l; P < 0.05), and ATP effluent was greatest with RFC + RHG (RFC: 5.3 ± 1.4; RHG: 5.3 ± 1.1; RFC + RHG: 11.6 ± 2.7 vs. Mean Rest: 1.2 ± 0.1 nmol/min; P < 0.05). We conclude that the mechanical effects of muscle contraction can 1) independently elevate intravascular ATP draining quiescent skeletal muscle without changes in local metabolism and 2) further augment intravascular ATP during mild exercise associated with increases in metabolism and local deoxygenation; therefore, it is likely one stimulus for increasing intravascular ATP during exercise in humans. PMID:23429876

  8. Advancing age produces sex differences in vasomotor kinetics during and after skeletal muscle contraction.

    PubMed

    Bearden, Shawn E

    2007-09-01

    Little is known of the vasomotor responses of skeletal muscle arterioles during and following muscle contraction. We hypothesized that aging leads to impaired arteriolar responses to muscle contraction and recovery. Nitric oxide (NO) availability, which is age dependent, has been implicated in components of these kinetics. Therefore, we also hypothesized that changes in the kinetics of vascular responses are associated with the NO pathway. Groups were young (3 mo), old (24 mo), endothelial NO synthase knockout (eNOS-/-), and N(G)-nitro-L-arginine (L-NA)-treated male and female C57BL/6 mice. The kinetics of vasodilation during and following 1 min of contractions of the gluteus maximus muscle were recorded in second-order (regional distribution) and third-order (local control) arterioles. Baseline, peak (during contraction), and maximal diameters (pharmacological) were not affected by age or sex. The kinetics of dilation and recovery were not different between males and females at the young age. There was a significant slowing of vasodilation at the onset of contractions (approximately 2-fold; P < 0.05) and a significant speeding of recovery ( approximately 5-fold; P < 0.05) in old males vs. old females and vs. young eNOS-/-, and L-NA did not affect the kinetics at the onset of muscle contraction. eNOS-/- mimicked the rapid recovery of old males in second-order arterioles; acute NO production (L-NA) explained approximately 50% of this effect. These data demonstrate fundamental age-related differences between the sexes in the dynamic function of skeletal muscle arterioles. Understanding how youthful function persists in females but not males may provide therapeutic insight into clinical interventions to maintain dynamic microvascular control of nutrient supply with age.

  9. Fatiguing contractions increase protein S-glutathionylation occupancy in mouse skeletal muscle.

    PubMed

    Kramer, Philip A; Duan, Jicheng; Gaffrey, Matthew J; Shukla, Anil K; Wang, Lu; Bammler, Theo K; Qian, Wei-Jun; Marcinek, David J

    2018-05-23

    Protein S-glutathionylation is an important reversible post-translational modification implicated in redox signaling. Oxidative modifications to protein thiols can alter the activity of metabolic enzymes, transcription factors, kinases, phosphatases, and the function of contractile proteins. However, the extent to which muscle contraction induces oxidative modifications in redox sensitive thiols is not known. The purpose of this study was to determine the targets of S-glutathionylation redox signaling following fatiguing contractions. Anesthetized adult male CB6F1 (BALB/cBy × C57BL/6) mice were subjected to acute fatiguing contractions for 15 min using in vivo stimulations. The right (stimulated) and left (unstimulated) gastrocnemius muscleswere collected 60 min after the last stimulation and processed for redox proteomics assay of S-glutathionylation. Using selective reduction with a glutaredoxin enzyme cocktail and resin-assisted enrichment technique, we quantified the levels of site-specific protein S-glutathionylation at rest and following fatiguing contractions. Redox proteomics revealed over 2200 sites of S-glutathionylation modifications, of which 1290 were significantly increased after fatiguing contractions. Muscle contraction leads to the greatest increase in S-glutathionylation in the mitochondria (1.03%) and the smallest increase in the nucleus (0.47%). Regulatory cysteines were significantly S-glutathionylated on mitochondrial complex I and II, GAPDH, MDH1, ACO2, and mitochondrial complex V among others. Similarly, S-glutathionylation of RYR1, SERCA1, titin, and troponin I2 are known to regulate muscle contractility and were significantly S-glutathionylated after just 15 min of fatiguing contractions. The largest fold changes (> 1.6) in the S-glutathionylated proteome after fatigue occurred on signaling proteins such as 14-3-3 protein gamma and MAP2K4, as well as proteins like SERCA1, and NDUV2 of mitochondrial complex I, at previously unknown

  10. Abdominal muscle response to a simulated weight-bearing task by elite Australian Rules football players.

    PubMed

    Hyde, Jodie; Stanton, Warren R; Hides, Julie A

    2012-02-01

    The aim of this study was to examine the automatic recruitment of the deep abdominal muscles during a unilateral simulated weight-bearing task by elite Australian Rules football (AFL) players with and without low back pain (LBP). An observational cross-sectional study was conducted using ultrasound imaging to measure the thickness of the internal oblique (IO) and transversus abdominis (TrA) muscles. Thirty-seven elite male AFL players participated. Repeated measures factors included 'force level' (rest, 25% and 45% of body weight), 'leg' (dominant or non-dominant kicking leg) and 'side' (ultrasound side ipsilateral or contralateral to the leg used for the weight-bearing task). The dependent variables were thickness of the IO and TrA muscles. The results of this study showed that thickness of the IO (p<.0001) and TrA (p<.0001) muscles increased in response to 'force level'. During the task, the thickness of the IO muscle on the contralateral side of the trunk relative to the leg being tested, increased more in participants with current LBP (p=.034). This pattern was more distinct on the non-dominant kicking leg. Altered abdominal muscle recruitment in elite athletes with low back pain may be an attempt by the central nervous system (CNS) to compensate for inadequate lumbo-pelvic stability. Copyright © 2011 Elsevier B.V. All rights reserved.

  11. Estimation of elbow flexion force during isometric muscle contraction from mechanomyography and electromyography.

    PubMed

    Youn, Wonkeun; Kim, Jung

    2010-11-01

    Mechanomyography (MMG) is the muscle surface oscillations that are generated by the dimensional change of the contracting muscle fibers. Because MMG reflects the number of recruited motor units and their firing rates, just as electromyography (EMG) is influenced by these two factors, it can be used to estimate the force exerted by skeletal muscles. The aim of this study was to demonstrate the feasibility of MMG for estimating the elbow flexion force at the wrist under an isometric contraction by using an artificial neural network in comparison with EMG. We performed experiments with five subjects, and the force at the wrist and the MMG from the contributing muscles were recorded. It was found that MMG could be utilized to accurately estimate the isometric elbow flexion force based on the values of the normalized root mean square error (NRMSE = 0.131 ± 0.018) and the cross-correlation coefficient (CORR = 0.892 ± 0.033). Although MMG can be influenced by the physical milieu/morphology of the muscle and EMG performed better than MMG, these experimental results suggest that MMG has the potential to estimate muscle forces. These experimental results also demonstrated that MMG in combination with EMG resulted in better performance estimation in comparison with EMG or MMG alone, indicating that a combination of MMG and EMG signals could be used to provide complimentary information on muscle contraction.

  12. Multiple Causes of Fatigue during Shortening Contractions in Rat Slow Twitch Skeletal Muscle

    PubMed Central

    Hortemo, Kristin Halvorsen; Munkvik, Morten; Lunde, Per Kristian; Sejersted, Ole M.

    2013-01-01

    Fatigue in muscles that shorten might have other causes than fatigue during isometric contractions, since both cross-bridge cycling and energy demand are different in the two exercise modes. While isometric contractions are extensively studied, the causes of fatigue in shortening contractions are poorly mapped. Here, we investigate fatigue mechanisms during shortening contractions in slow twitch skeletal muscle in near physiological conditions. Fatigue was induced in rat soleus muscles with maintained blood supply by in situ shortening contractions at 37°C. Muscles were stimulated repeatedly (1 s on/off at 30 Hz) for 15 min against a constant load, allowing the muscle to shorten and perform work. Fatigue and subsequent recovery was examined at 20 s, 100 s and 15 min exercise. The effects of prior exercise were investigated in a second exercise bout. Fatigue developed in three distinct phases. During the first 20 s the regulatory protein Myosin Light Chain-2 (slow isoform, MLC-2s) was rapidly dephosphorylated in parallel with reduced rate of force development and reduced shortening. In the second phase there was degradation of high-energy phosphates and accumulation of lactate, and these changes were related to slowing of muscle relengthening and relaxation, culminating at 100 s exercise. Slowing of relaxation was also associated with increased leak of calcium from the SR. During the third phase of exercise there was restoration of high-energy phosphates and elimination of lactate, and the slowing of relaxation disappeared, whereas dephosphorylation of MLC-2s and reduced shortening prevailed. Prior exercise improved relaxation parameters in a subsequent exercise bout, and we propose that this effect is a result of less accumulation of lactate due to more rapid onset of oxidative metabolism. The correlation between dephosphorylation of MLC-2s and reduced shortening was confirmed in various experimental settings, and we suggest MLC-2s as an important regulator of

  13. Intracellular oxygen tension limits muscle contraction-induced change in muscle oxygen consumption under hypoxic conditions during Hb-free perfusion.

    PubMed

    Takakura, Hisashi; Ojino, Minoru; Jue, Thomas; Yamada, Tatsuya; Furuichi, Yasuro; Hashimoto, Takeshi; Iwase, Satoshi; Masuda, Kazumi

    2017-01-01

    Under acute hypoxic conditions, the muscle oxygen uptake (mV˙O 2 ) during exercise is reduced by the restriction in oxygen-supplied volume to the mitochondria within the peripheral tissue. This suggests the existence of a factor restricting the mV˙O 2 under hypoxic conditions at the peripheral tissue level. Therefore, this study set out to test the hypothesis that the restriction in mV˙O 2 is regulated by the net decrease in intracellular oxygen tension equilibrated with myoglobin oxygen saturation (∆P mb O 2 ) during muscle contraction under hypoxic conditions. The hindlimb of male Wistar rats (8 weeks old, n = 5) was perfused with hemoglobin-free Krebs-Henseleit buffer equilibrated with three different fractions of O 2 gas: 95.0%O 2 , 71.3%O 2 , and 47.5%O 2 The deoxygenated myoglobin (Mb) kinetics during muscle contraction were measured under each oxygen condition with a near-infrared spectroscopy. The ∆[deoxy-Mb] kinetics were converted to oxygen saturation of myoglobin (S mb O 2 ), and the P mb O 2 was then calculated based on the S mb O 2 and the O 2 dissociation curve of the Mb. The S mb O 2 and P mb O 2 at rest decreased with the decrease in O 2 supply, and the muscle contraction caused a further decrease in S mb O 2 and P mb O 2 under all O 2 conditions. The net increase in mV˙O 2 from the muscle contraction (∆mV˙O 2 ) gradually decreased as the ∆P mb O 2 decreased during muscle contraction. The results of this study suggest that ΔP mb O 2 is a key determinant of the ΔmV˙O 2 . © 2017 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

  14. Fractal based complexity measure and variation in force during sustained isometric muscle contraction: effect of aging.

    PubMed

    Arjunan, Sridhar P; Kumar, Dinesh K; Bastos, Teodiano

    2012-01-01

    This study has investigated the effect of age on the fractal based complexity measure of muscle activity and variance in the force of isometric muscle contraction. Surface electromyogram (sEMG) and force of muscle contraction were recorded from 40 healthy subjects categorized into: Group 1: Young - age range 20-30; 10 Males and 10 Females, Group 2: Old - age range 55-70; 10 Males and 10 Females during isometric exercise at Maximum Voluntary contraction (MVC). The results show that there is a reduction in the complexity of surface electromyogram (sEMG) associated with aging. The results demonstrate that there is an increase in the coefficient of variance (CoV) of the force of muscle contraction and a decrease in complexity of sEMG for the Old age group when compared with the Young age group.

  15. Rho Kinase (ROCK) collaborates with Pak to Regulate Actin Polymerization and Contraction in Airway Smooth Muscle.

    PubMed

    Zhang, Wenwu; Bhetwal, Bhupal P; Gunst, Susan J

    2018-05-10

    The mechanisms by which Rho kinase (ROCK) regulates airway smooth muscle contraction were determined in tracheal smooth muscle tissues. ROCK may mediate smooth muscle contraction by inhibiting myosin regulatory light chain (RLC) phosphatase. ROCK can also regulate F-actin dynamics during cell migration, and actin polymerization is critical for airway smooth muscle contraction. Our results show that ROCK does not regulate airway smooth muscle contraction by inhibiting myosin RLC phosphatase or by stimulating myosin RLC phosphorylation. We find that ROCK regulates airway smooth muscle contraction by activating the serine-threonine kinase Pak, which mediates the activation of Cdc42 and Neuronal-Wiskott-Aldrich Syndrome protein (N-WASp). N-WASP transmits signals from cdc42 to the Arp2/3 complex for the nucleation of actin filaments. These results demonstrate a novel molecular function for ROCK in the regulation of Pak and cdc42 activation that is critical for the processes of actin polymerization and contractility in airway smooth muscle. Rho kinase (ROCK), a RhoA GTPase effector, can regulate the contraction of airway and other smooth muscle tissues. In some tissues, ROCK can inhibit myosin regulatory light chain (RLC) phosphatase, which increases the phosphorylation of myosin RLC and promotes smooth muscle contraction. ROCK can also regulate cell motility and migration by affecting F-actin dynamics. Actin polymerization is stimulated by contractile agonists in airway smooth muscle tissues and is required for contractile tension development in addition to myosin RLC phosphorylation. We investigated the mechanisms by which ROCK regulates the contractility of tracheal smooth muscle tissues by expressing a kinase inactive mutant of ROCK, ROCK-K121G, in the tissues or by treating them with the ROCK inhibitor, H-1152P. Our results show no role for ROCK in the regulation of non-muscle or smooth muscle myosin RLC phosphorylation during contractile stimulation in this tissue

  16. Detection of the electromechanical delay and its components during voluntary isometric contraction of the quadriceps femoris muscle.

    PubMed

    Begovic, Haris; Zhou, Guang-Quan; Li, Tianjie; Wang, Yi; Zheng, Yong-Ping

    2014-01-01

    Electromechanical delay (EMD) was described as a time elapsed between first trigger and force output. Various results have been reported based on the measurement method with observed inconsistent results when the trigger is elicited by voluntary contraction. However, mechanomyographic (MMG) sensor placed far away on the skin from the contracting muscle was used to detect muscle fiber motion and excitation-contraction (EC) coupling which may give unreliable results. On this basis, the purpose of this study was to detect EMD during active muscle contraction whilst introducing an ultrafast ultrasound (US) method to detect muscle fiber motion from a certain depth of the muscle. Time delays between onsets of EMG-MMG, EMG-US, MMG-FORCE, US-FORCE, and EMG-FORCE were calculated as 20.5 ± 4.73, 28.63 ± 6.31, 19.21 ± 6.79, 30.52 ± 8.85, and 49.73 ± 6.99 ms, respectively. Intrarater correlation coefficient (ICC) was higher than MMG when ultrafast US was used for detecton of the Δt EMG-US and Δt US-FORCE, ICC values of 0.75 and 0.70, respectively. Synchronization of the ultrafast ultrasound with EMG and FORCE sensors can reveal reliable and clinically useful results related to the EMD and its components when muscle is voluntarily contracted. With ultrafast US, we detect onset from the certain depth of the muscle excluding the tissues above the muscle acting as a low-pass filter which can lead to inaccurate time detection about the onset of the contracting muscle fibers. With this non-invasive technique, understanding of the muscle dynamics can be facilitated.

  17. Role of dystroglycan in limiting contraction-induced injury to the sarcomeric cytoskeleton of mature skeletal muscle.

    PubMed

    Rader, Erik P; Turk, Rolf; Willer, Tobias; Beltrán, Daniel; Inamori, Kei-Ichiro; Peterson, Taylor A; Engle, Jeffrey; Prouty, Sally; Matsumura, Kiichiro; Saito, Fumiaki; Anderson, Mary E; Campbell, Kevin P

    2016-09-27

    Dystroglycan (DG) is a highly expressed extracellular matrix receptor that is linked to the cytoskeleton in skeletal muscle. DG is critical for the function of skeletal muscle, and muscle with primary defects in the expression and/or function of DG throughout development has many pathological features and a severe muscular dystrophy phenotype. In addition, reduction in DG at the sarcolemma is a common feature in muscle biopsies from patients with various types of muscular dystrophy. However, the consequence of disrupting DG in mature muscle is not known. Here, we investigated muscles of transgenic mice several months after genetic knockdown of DG at maturity. In our study, an increase in susceptibility to contraction-induced injury was the first pathological feature observed after the levels of DG at the sarcolemma were reduced. The contraction-induced injury was not accompanied by increased necrosis, excitation-contraction uncoupling, or fragility of the sarcolemma. Rather, disruption of the sarcomeric cytoskeleton was evident as reduced passive tension and decreased titin immunostaining. These results reveal a role for DG in maintaining the stability of the sarcomeric cytoskeleton during contraction and provide mechanistic insight into the cause of the reduction in strength that occurs in muscular dystrophy after lengthening contractions.

  18. Normal Weight but Low Muscle Mass and Abdominally Obese: Implications for the Cardiometabolic Risk Profile in Chronic Obstructive Pulmonary Disease.

    PubMed

    Beijers, Rosanne J H C G; van de Bool, Coby; van den Borst, Bram; Franssen, Frits M E; Wouters, Emiel F M; Schols, Annemie M W J

    2017-06-01

    It is well established that low muscle mass affects physical performance in chronic obstructive pulmonary disease (COPD). We hypothesize that combined low muscle mass and abdominal obesity may also adversely influence the cardiometabolic risk profile in COPD, even in those with normal weight. The cardiometabolic risk profile and the responsiveness to 4 months high-intensity exercise training was assessed in normal-weight patients with COPD with low muscle mass stratified by abdominal obesity. This is a cross-sectional study including 81 clinically stable patients with COPD (age 62.5 ± 8.2 years; 50.6% males; forced expiratory volume in 1 second 55.1 ± 19.5 percentage predicted) with fat-free mass index <25th percentile eligible for outpatient pulmonary rehabilitation. Body composition, blood biomarkers, blood pressure, physical activity level, dietary intake, and physical performance were assessed at baseline and in a subgroup after 4 months of exercise training. Mean body mass index was 22.7 ± 2.7 kg/m 2 , and 75% of patients had abdominal obesity. Abdominally obese patients had higher glucose, insulin, homeostatic model assessment for insulin resistance (HOMA-IR), branched chain amino acids and a higher prevalence of metabolic syndrome compared with those without abdominal obesity. Exercise training improved cycling endurance time and quadriceps strength, but did not yield a clinically meaningful improvement of the cardiometabolic risk profile. Triglycerides showed a significant decrease, while the HOMA-IR increased. Abdominal obesity is highly prevalent in normal-weight patients with COPD with low muscle mass who showed an increased cardiometabolic risk compared with patients without abdominal obesity. This cardiometabolic risk profile was not altered after 4 months of exercise training. Copyright © 2017 AMDA – The Society for Post-Acute and Long-Term Care Medicine. Published by Elsevier Inc. All rights reserved.

  19. Direct optical activation of skeletal muscle fibres efficiently controls muscle contraction and attenuates denervation atrophy

    PubMed Central

    Magown, Philippe; Shettar, Basavaraj; Zhang, Ying; Rafuse, Victor F.

    2015-01-01

    Neural prostheses can restore meaningful function to paralysed muscles by electrically stimulating innervating motor axons, but fail when muscles are completely denervated, as seen in amyotrophic lateral sclerosis, or after a peripheral nerve or spinal cord injury. Here we show that channelrhodopsin-2 is expressed within the sarcolemma and T-tubules of skeletal muscle fibres in transgenic mice. This expression pattern allows for optical control of muscle contraction with comparable forces to nerve stimulation. Force can be controlled by varying light pulse intensity, duration or frequency. Light-stimulated muscle fibres depolarize proportionally to light intensity and duration. Denervated triceps surae muscles transcutaneously stimulated optically on a daily basis for 10 days show a significant attenuation in atrophy resulting in significantly greater contractile forces compared with chronically denervated muscles. Together, this study shows that channelrhodopsin-2/H134R can be used to restore function to permanently denervated muscles and reduce pathophysiological changes associated with denervation pathologies. PMID:26460719

  20. Polo-like Kinase 1 Regulates Vimentin Phosphorylation at Ser-56 and Contraction in Smooth Muscle*

    PubMed Central

    Li, Jia; Wang, Ruping; Gannon, Olivia J.; Rezey, Alyssa C.; Jiang, Sixin; Gerlach, Brennan D.; Liao, Guoning

    2016-01-01

    Polo-like kinase 1 (Plk1) is a serine/threonine-protein kinase that has been implicated in mitosis, cytokinesis, and smooth muscle cell proliferation. The role of Plk1 in smooth muscle contraction has not been investigated. Here, stimulation with acetylcholine induced Plk1 phosphorylation at Thr-210 (an indication of Plk1 activation) in smooth muscle. Contractile stimulation also activated Plk1 in live smooth muscle cells as evidenced by changes in fluorescence resonance energy transfer signal of a Plk1 sensor. Moreover, knockdown of Plk1 in smooth muscle attenuated force development. Smooth muscle conditional knock-out of Plk1 also diminished contraction of mouse tracheal rings. Plk1 knockdown inhibited acetylcholine-induced vimentin phosphorylation at Ser-56 without affecting myosin light chain phosphorylation. Expression of T210A Plk1 inhibited the agonist-induced vimentin phosphorylation at Ser-56 and contraction in smooth muscle. However, myosin light chain phosphorylation was not affected by T210A Plk1. Ste20-like kinase (SLK) is a serine/threonine-protein kinase that has been implicated in spindle orientation and microtubule organization during mitosis. In this study knockdown of SLK inhibited Plk1 phosphorylation at Thr-210 and activation. Finally, asthma is characterized by airway hyperresponsiveness, which largely stems from airway smooth muscle hyperreactivity. Here, smooth muscle conditional knock-out of Plk1 attenuated airway resistance and airway smooth muscle hyperreactivity in a murine model of asthma. Taken together, these findings suggest that Plk1 regulates smooth muscle contraction by modulating vimentin phosphorylation at Ser-56. Plk1 activation is regulated by SLK during contractile activation. Plk1 contributes to the pathogenesis of asthma. PMID:27662907

  1. Dystrophin restoration therapy improves both the reduced excitability and the force drop induced by lengthening contractions in dystrophic mdx skeletal muscle.

    PubMed

    Roy, Pauline; Rau, Fredérique; Ochala, Julien; Messéant, Julien; Fraysse, Bodvael; Lainé, Jeanne; Agbulut, Onnik; Butler-Browne, Gillian; Furling, Denis; Ferry, Arnaud

    2016-01-01

    The greater susceptibility to contraction-induced skeletal muscle injury (fragility) is an important dystrophic feature and tool for testing preclinic dystrophin-based therapies for Duchenne muscular dystrophy. However, how these therapies reduce the muscle fragility is not clear. To address this question, we first determined the event(s) of the excitation-contraction cycle which is/are altered following lengthening (eccentric) contractions in the mdx muscle. We found that the immediate force drop following lengthening contractions, a widely used measure of muscle fragility, was associated with reduced muscle excitability. Moreover, the force drop can be mimicked by an experimental reduction in muscle excitation of uninjured muscle. Furthermore, the force drop was not related to major neuromuscular transmission failure, excitation-contraction uncoupling, and myofibrillar impairment. Secondly, and importantly, the re-expression of functional truncated dystrophin in the muscle of mdx mice using an exon skipping strategy partially prevented the reductions in both force drop and muscle excitability following lengthening contractions. We demonstrated for the first time that (i) the increased susceptibility to contraction-induced muscle injury in mdx mice is mainly attributable to reduced muscle excitability; (ii) dystrophin-based therapy improves fragility of the dystrophic skeletal muscle by preventing reduction in muscle excitability.

  2. Mechanical influences on skeletal muscle vascular tone in humans: insight into contraction-induced rapid vasodilatation

    PubMed Central

    Kirby, Brett S; Carlson, Rick E; Markwald, Rachel R; Voyles, Wyatt F; Dinenno, Frank A

    2007-01-01

    We tested the hypothesis that mechanical deformation of forearm blood vessels via acute increases in extravascular pressure elicits rapid vasodilatation in humans. In healthy adults, we measured forearm blood flow (Doppler ultrasound) and calculated forearm vascular conductance (FVC) responses to whole forearm compressions and isometric muscle contractions with the arm above heart level. We used several experimental protocols to gain insight into how mechanical factors contribute to contraction-induced rapid vasodilatation. The findings from the present study clearly indicate that acute increases in extravascular pressure (200 mmHg for 2 s) elicit a significant rapid vasodilatation in the human forearm (peak ΔFVC∼155%). Brief, 6 s sustained compressions evoked the greatest vasodilatation (ΔFVC∼260%), whereas the responses to single (2 s) and repeated compressions (five repeated 2 s compressions) were not significantly different (ΔFVC∼155%versus∼115%, respectively). This mechanically induced vasodilatation peaks within 1–2 cardiac cycles, and thus is dissociated from the temporal pattern normally observed in response to brief muscle contractions (∼4–7 cardiac cycles). A non-linear relation was found between graded increases in extravascular pressure and both the immediate and peak rapid vasodilatory response, such that the responses increased sharply from 25 to 100 mmHg, with no significant further dilatation until 300 mmHg (maximal ΔFVC∼185%). This was in contrast to the linear intensity-dependent relation observed with muscle contractions. Our collective findings indicate that mechanical influences contribute largely to the immediate vasodilatation (first cardiac cycle) observed in response to a brief, single contraction. However, it is clear that there are additional mechanisms related to muscle activation that continue to cause and sustain vasodilatation for several more cardiac cycles after contraction. Additionally, the potential

  3. [Urothelium-dependent modulation of urinary bladder smooth muscle contractions by menthol].

    PubMed

    Paduraru, O M; Filippov, I B; Boldyriev, O I; Vladymyrova, I A; Naĭd'onov, V H; Shuba, Ia M

    2011-01-01

    TRPM8 cold receptor/channel is considered amongst the variety of receptors that support and modulate sensory function of urothelium, although the information regarding this is still quite contradictory. Here we have studied the effects of nonspecific TRPM8 activator menthol on the contractions of the smooth muscle strips of the rat bladder with intact and removed urothelium, and assessed the expression in them of TRPM8 mRNA using semi-quantitative RT-PCR. Menthol (100 microM) decreased the basal tone and the amplitude of spontaneous contractions only in the strips with intact urothelium. Irrespective of the presence of urothelium it similarly inhibited (by approximately 45 %) the contractions evoked by high-potassium depolarization. Contractions induced by muscarinic agonist carbachol (1 microM) were inhibited by menthol much stronger (by approximately 63%) if the urothelium was present than without it (by approximately 12%). Expression of TRPM8 mRNA in urothelium was not detected, whilst in detrusor smooth muscle it was found very low. We conclude that modulation of contractile responses by menthol is most likely explained by its blocking action on voltage-gated calcium channels ofdetrusor smooth muscle cells (SMC) and by menthol-stimulated release from urothelium of some factor(s) with relaxant effects on SMCs. Stimulation of the secretion of these factors from urothelial cells most likely involves menthol-induced, TRPM8-independent mobilization of calcium.

  4. The generalized Hill model: A kinematic approach towards active muscle contraction

    NASA Astrophysics Data System (ADS)

    Göktepe, Serdar; Menzel, Andreas; Kuhl, Ellen

    2014-12-01

    Excitation-contraction coupling is the physiological process of converting an electrical stimulus into a mechanical response. In muscle, the electrical stimulus is an action potential and the mechanical response is active contraction. The classical Hill model characterizes muscle contraction though one contractile element, activated by electrical excitation, and two non-linear springs, one in series and one in parallel. This rheology translates into an additive decomposition of the total stress into a passive and an active part. Here we supplement this additive decomposition of the stress by a multiplicative decomposition of the deformation gradient into a passive and an active part. We generalize the one-dimensional Hill model to the three-dimensional setting and constitutively define the passive stress as a function of the total deformation gradient and the active stress as a function of both the total deformation gradient and its active part. We show that this novel approach combines the features of both the classical stress-based Hill model and the recent active-strain models. While the notion of active stress is rather phenomenological in nature, active strain is micro-structurally motivated, physically measurable, and straightforward to calibrate. We demonstrate that our model is capable of simulating excitation-contraction coupling in cardiac muscle with its characteristic features of wall thickening, apical lift, and ventricular torsion.

  5. Abdominal Muscle Activity during Mechanical Ventilation Increases Lung Injury in Severe Acute Respiratory Distress Syndrome

    PubMed Central

    Zhang, Xianming; Wu, Weiliang; Zhu, Yongcheng; Jiang, Ying; Du, Juan; Chen, Rongchang

    2016-01-01

    Objective It has proved that muscle paralysis was more protective for injured lung in severe acute respiratory distress syndrome (ARDS), but the precise mechanism is not clear. The purpose of this study was to test the hypothesis that abdominal muscle activity during mechanically ventilation increases lung injury in severe ARDS. Methods Eighteen male Beagles were studied under mechanical ventilation with anesthesia. Severe ARDS was induced by repetitive oleic acid infusion. After lung injury, Beagles were randomly assigned into spontaneous breathing group (BIPAPSB) and abdominal muscle paralysis group (BIPAPAP). All groups were ventilated with BIPAP model for 8h, and the high pressure titrated to reached a tidal volume of 6ml/kg, the low pressure was set at 10 cmH2O, with I:E ratio 1:1, and respiratory rate adjusted to a PaCO2 of 35–60 mmHg. Six Beagles without ventilator support comprised the control group. Respiratory variables, end-expiratory volume (EELV) and gas exchange were assessed during mechanical ventilation. The levels of Interleukin (IL)-6, IL-8 in lung tissue and plasma were measured by qRT-PCR and ELISA respectively. Lung injury scores were determined at end of the experiment. Results For the comparable ventilator setting, as compared with BIPAPSB group, the BIPAPAP group presented higher EELV (427±47 vs. 366±38 ml) and oxygenation index (293±36 vs. 226±31 mmHg), lower levels of IL-6(216.6±48.0 vs. 297.5±71.2 pg/ml) and IL-8(246.8±78.2 vs. 357.5±69.3 pg/ml) in plasma, and lower express levels of IL-6 mRNA (15.0±3.8 vs. 21.2±3.7) and IL-8 mRNA (18.9±6.8 vs. 29.5±7.9) in lung tissues. In addition, less lung histopathology injury were revealed in the BIPAPAP group (22.5±2.0 vs. 25.2±2.1). Conclusion Abdominal muscle activity during mechanically ventilation is one of the injurious factors in severe ARDS, so abdominal muscle paralysis might be an effective strategy to minimize ventilator-induce lung injury. PMID:26745868

  6. Abdominal Muscle Activity during Mechanical Ventilation Increases Lung Injury in Severe Acute Respiratory Distress Syndrome.

    PubMed

    Zhang, Xianming; Wu, Weiliang; Zhu, Yongcheng; Jiang, Ying; Du, Juan; Chen, Rongchang

    2016-01-01

    It has proved that muscle paralysis was more protective for injured lung in severe acute respiratory distress syndrome (ARDS), but the precise mechanism is not clear. The purpose of this study was to test the hypothesis that abdominal muscle activity during mechanically ventilation increases lung injury in severe ARDS. Eighteen male Beagles were studied under mechanical ventilation with anesthesia. Severe ARDS was induced by repetitive oleic acid infusion. After lung injury, Beagles were randomly assigned into spontaneous breathing group (BIPAPSB) and abdominal muscle paralysis group (BIPAPAP). All groups were ventilated with BIPAP model for 8h, and the high pressure titrated to reached a tidal volume of 6ml/kg, the low pressure was set at 10 cmH2O, with I:E ratio 1:1, and respiratory rate adjusted to a PaCO2 of 35-60 mmHg. Six Beagles without ventilator support comprised the control group. Respiratory variables, end-expiratory volume (EELV) and gas exchange were assessed during mechanical ventilation. The levels of Interleukin (IL)-6, IL-8 in lung tissue and plasma were measured by qRT-PCR and ELISA respectively. Lung injury scores were determined at end of the experiment. For the comparable ventilator setting, as compared with BIPAPSB group, the BIPAPAP group presented higher EELV (427±47 vs. 366±38 ml) and oxygenation index (293±36 vs. 226±31 mmHg), lower levels of IL-6(216.6±48.0 vs. 297.5±71.2 pg/ml) and IL-8(246.8±78.2 vs. 357.5±69.3 pg/ml) in plasma, and lower express levels of IL-6 mRNA (15.0±3.8 vs. 21.2±3.7) and IL-8 mRNA (18.9±6.8 vs. 29.5±7.9) in lung tissues. In addition, less lung histopathology injury were revealed in the BIPAPAP group (22.5±2.0 vs. 25.2±2.1). Abdominal muscle activity during mechanically ventilation is one of the injurious factors in severe ARDS, so abdominal muscle paralysis might be an effective strategy to minimize ventilator-induce lung injury.

  7. Potentiation of carbachol-induced detrusor smooth muscle contractions by beta-adrenoceptor activation.

    PubMed

    Klausner, Adam P; Rourke, Keith F; Miner, Amy S; Ratz, Paul H

    2009-03-15

    In strips of rabbit bladder free of urothelium, the beta-adrenoceptor agonist, isoproterenol, significantly reduced basal detrusor smooth muscle tone and inhibited contractions produced by low concentrations of the muscarinic receptor agonist, carbachol. During a carbachol concentration-response curve, instead of inhibiting, isoproterenol strengthened contractions produced by high carbachol concentrations. Thus, the carbachol concentration-response curve was shifted by isoproterenol from a shallow, graded relationship, to a steep, switch-like relationship. The tyrosine kinase inhibitor, genistein, inhibited carbachol-induced contractions only in the presence of isoproterenol. Contraction produced by a single high carbachol concentration (1 microM) displayed 1 fast and 1 slow peak. In the presence of isoproterenol, the slow peak was not strengthened, but was delayed, and U-0126 (mitogen-activated protein kinase kinase inhibitor) selectively inhibited this delay concomitantly with inhibition of extracellular signal-regulated kinase (ERK) phosphorylation. Isoproterenol reduced ERK phosphorylation only in the absence of carbachol. These data support the concept that, by inhibiting weak contractions, potentiating strong contractions, and producing a more switch-like concentration-response curve, beta-adrenoceptor stimulation enhanced the effectiveness of muscarinic receptor-induced detrusor smooth muscle contraction. Moreover, beta-adrenoceptor stimulation changed the cellular mechanism by which carbachol produced contraction. The potential significance of multi-receptor and multi-cell crosstalk is discussed.

  8. Recruitment and plasticity in diaphragm, intercostal, and abdominal muscles in unanesthetized rats

    PubMed Central

    Navarrete-Opazo, A.

    2014-01-01

    Although rats are a frequent model for studies of plasticity in respiratory motor control, the relative capacity of rat accessory respiratory muscles to express plasticity is not well known, particularly in unanesthetized animals. Here, we characterized external intercostal (T2, T4, T5, T6, T7, T8, T9 EIC) and abdominal muscle (external oblique and rectus abdominis) electromyogram (EMG) activity in unanesthetized rats via radiotelemetry during normoxia (Nx: 21% O2) and following acute intermittent hypoxia (AIH: 10 × 5-min, 10.5% O2; 5-min intervals). Diaphragm and T2–T5 EIC EMG activity, and ventilation were also assessed during maximal chemoreceptor stimulation (MCS: 7% CO2, 10.5% O2) and sustained hypoxia (SH: 10.5% O2). In Nx, T2 EIC exhibits prominent inspiratory activity, whereas T4, T5, T6, and T7 EIC inspiratory activity decreases in a caudal direction. T8 and T9 EIC and abdominal muscles show only tonic or sporadic activity, without consistent respiratory activity. MCS increases diaphragm and T2 EIC EMG amplitude and tidal volume more than SH (0.94 ± 0.10 vs. 0.68 ± 0.05 ml/100 g; P < 0.001). Following AIH, T2 EIC EMG amplitude remained above baseline for more than 60 min post-AIH (i.e., EIC long-term facilitation, LTF), and was greater than diaphragm LTF (41.5 ± 1.3% vs. 19.1 ± 2.0% baseline; P < 0.001). We conclude that 1) diaphragm and rostral T2–T5 EIC muscles exhibit inspiratory activity during Nx; 2) MCS elicits greater ventilatory, diaphragm, and rostral T2–T5 EIC muscle activity vs. SH; and 3) AIH induces greater rostral EIC LTF than diaphragm LTF. PMID:24833779

  9. Do Differences in Levels, Types, and Duration of Muscle Contraction Have an Effect on the Degree of Post-exercise Depression?

    PubMed

    Miyaguchi, Shota; Kojima, Sho; Kirimoto, Hikari; Tamaki, Hiroyuki; Onishi, Hideaki

    2016-01-01

    We conducted two experiments to determine how differences in muscle contraction levels, muscle contraction types, and movement duration affect degree of post-exercise depression (PED) after non-exhaustive, repetitive finger movement. Twelve healthy participants performed repetitive abduction movements of the right index finger at 2 Hz. In experiment 1, we examined the effects of muscle contraction levels at 10, 20, and 30% maximum voluntary contraction and the effects of muscle contraction types at isotonic and isometric contraction. In experiment 2, we examined the effects of movement duration at 2 and 6 min. Motor-evoked potentials (MEPs) were recorded from the right first dorsal interosseous muscle before movement tasks and 1-10 min after movement tasks. MEP amplitudes after isotonic contraction tasks were significantly smaller than those after isometric contraction tasks and decreased with increasing contraction levels, but were independent of movement duration. This study demonstrated that the degree of PED after non-exhaustive repetitive finger movement depended on muscle contraction levels and types. Thus, the degree of PED may depend on the levels of activity in the motor cortex during a movement task. This knowledge will aid in the design of rehabilitation protocols.

  10. Examination of contraction-induced muscle pain as a behavioral correlate of physical activity in women with and without fibromyalgia.

    PubMed

    Umeda, Masataka; Corbin, Lisa W; Maluf, Katrina S

    2015-01-01

    This study aimed to compare muscle pain intensity during a sustained isometric contraction in women with and without fibromyalgia (FM), and examine the association between muscle pain and self-reported levels of physical activity. Fourteen women with FM and 14 healthy women completed the study, where muscle pain ratings (MPRs) were obtained every 30 s during a 3 min isometric handgrip task at 25% maximal strength, and self-reported physical activity was quantified using the Baecke Physical Activity Questionnaire. Women with FM were less physically active than healthy controls. During the isometric contraction, MPR progressively increased in both groups at a comparable rate, but women with FM generally reported a greater intensity of muscle pain than healthy controls. Among all women, average MPR scores were inversely associated with self-reported physical activity levels. Women with FM exhibit augmented muscle pain during isometric contractions and reduced physical activity than healthy controls. Furthermore, contraction-induced muscle pain is inversely associated with physical activity levels. These observations suggest that augmented muscle pain may serve as a behavioral correlate of reduced physical activity in women with FM. Implications for Rehabilitation Women with fibromyalgia experience a greater intensity of localized muscle pain in a contracting muscle compared to healthy women. The intensity of pain during muscle contraction is inversely associated with the amount of physical activity in women with and without fibromyalgia. Future studies should determine whether exercise adherence can be improved by considering the relationship between contraction-induced muscle pain and participation in routine physical activity.

  11. Abdominal rectus muscle pyomyositis: Report of a case and review of the literature

    PubMed Central

    Fountoukis, Tilemachos; Tsatsanidis, Nikolaos; Tilkeridou, Maria; Konstantinou, Ioannis; Fytas, Pantelis; Skandalos, Ioannis

    2018-01-01

    Pyomyositis is an uncommon primary bacterial infection of skeletal muscles, usually caused by Staphylococcus aureus. Predisposing factors for pyomyositis include immunodeficiency, trauma, injection drug use, concurrent infection and malnutrition. The diagnosis, staging of the disease and differential diagnosis are established by ultrasound, CT and MRI. Treatment involves surgical drainage and antibiotic therapy. We report a case of abdominal rectus muscle pyomyositis, which constitutes, as far as we know, the second reported in bibliography, while Prevotella disiens is firstly reported as causative agent. PMID:29721242

  12. Ultrasound evaluation of muscle thickness changes in the external oblique, internal oblique, and transversus abdominis muscles considering the influence of posture and muscle contraction.

    PubMed

    Sugaya, Tomoaki; Abe, Yota; Sakamoto, Masaaki

    2014-09-01

    [Purpose] The aim of this study was to investigate muscle thickness changes in the external oblique (EO), internal oblique (IO), and transversus abdominis (TrA) muscles between the neutral position and trunk rotation, under a state of rest without voluntary contractions, and isometric contractions to both sides with resistance of 50% of the maximum trunk rotation strength. [Subjects] The subjects of this study were 21 healthy young men. [Methods] Muscle thickness changes in the EO, IO, and TrA in each position and state were evaluated by ultrasound. The range of motion at maximum trunk rotation and the maximum strength of trunk rotation were measured using a hand-held dynamometer. [Results] In the neutral position and at 50% trunk rotation to the right side, the thicknesses of the IO and TrA significantly increased with resistance. In both states, the thicknesses of the IO and TrA significantly increased at 50% trunk rotation to the right side. [Conclusion] The muscular contractions of the IO and TrA were stronger during ipsilateral rotation than in the neutral position and with resistance than at rest. Moreover, the muscular contraction was strongest in the resistive state during ipsilateral rotation.

  13. The importance of a normal breathing pattern for an effective abdominal-hollowing maneuver in healthy people: an experimental study.

    PubMed

    Ha, Sung-min; Kwon, Oh-yun; Kim, Su-jung; Choung, Sung-dae

    2014-02-01

    A normal breathing pattern while performing the abdominal-hollowing (AH) maneuver or spinal-stabilization exercise is essential for the success of rehabilitation programs and exercises. In previous studies, subjects were given standardized instructions to control the influence of respiration during the AH maneuver. However, the effect of breathing pattern on abdominal-muscle thickness during the AH maneuver has not been investigated. To compare abdominal-muscle thickness in subjects performing the AH maneuver under normal and abnormal breathing-pattern conditions and to investigate the effect of breathing pattern on the preferential contraction ratio (PCR) of the transverse abdominis. Comparative, repeated-measures experimental study. University research laboratory. 16 healthy subjects (8 male, 8 female) from a university population. A real-time ultrasound scanner was used to measure abdominal-muscle thickness during normal and abnormal breathing patterns. A paired t test was used to assess the effect of breathing pattern on abdominal-muscle thickness and PCR. Muscle thickness in the transverse abdominis and internal oblique muscles was significantly greater under the normal breathing pattern than under the abnormal pattern (P < .05). The PCR of the transverse abdominis was significantly higher under the normal breathing pattern compared with the abnormal pattern (P < .05). The results indicate that a normal breathing pattern is essential for performance of an effective AH maneuver. Thus, clinicians should ensure that patients adopt a normal breathing pattern before performing the AH maneuver and monitor transverse abdominis activation during the maneuver.

  14. Comparison between maximal lengthening and shortening contractions for biceps brachii muscle oxygenation and hemodynamics.

    PubMed

    Muthalib, Makii; Lee, Hoseong; Millet, Guillaume Y; Ferrari, Marco; Nosaka, Kazunori

    2010-09-01

    Eccentric contractions (ECC) require lower systemic oxygen (O2) and induce greater symptoms of muscle damage than concentric contractions (CON); however, it is not known if local muscle oxygenation is lower in ECC than CON during and following exercise. This study compared between ECC and CON for changes in biceps brachii muscle oxygenation [tissue oxygenation index (TOI)] and hemodynamics [total hemoglobin volume (tHb)=oxygenated-Hb+deoxygenated-Hb], determined by near-infrared spectroscopy over 10 sets of 6 maximal contractions of the elbow flexors of 10 healthy subjects. This study also compared between ECC and CON for changes in TOI and tHb during a 10-s sustained and 30-repeated maximal isometric contraction (MVC) task measured immediately before and after and 1-3 days following exercise. The torque integral during ECC was greater (P<0.05) than that during CON by approximately 30%, and the decrease in TOI was smaller (P<0.05) by approximately 50% during ECC than CON. Increases in tHb during the relaxation phases were smaller (P<0.05) by approximately 100% for ECC than CON; however, the decreases in tHb during the contraction phases were not significantly different between sessions. These results suggest that ECC utilizes a lower muscle O2 relative to O2 supply compared with CON. Following exercise, greater (P<0.05) decreases in MVC strength and increases in plasma creatine kinase activity and muscle soreness were evident 1-3 days after ECC than CON. Torque integral, TOI, and tHb during the sustained and repeated MVC tasks decreased (P<0.01) only after ECC, suggesting that muscle O2 demand relative to O2 supply during the isometric tasks was decreased after ECC. This could mainly be due to a lower maximal muscle mass activated as a consequence of muscle damage; however, an increase in O2 supply due to microcirculation dysfunction and/or inflammatory vasodilatory responses after ECC is recognized.

  15. A novel pattern of longitudinal muscle contraction with subthreshold pharyngeal stimulus: a possible mechanism of lower esophageal sphincter relaxation.

    PubMed

    Leslie, Eric; Bhargava, Valmik; Mittal, Ravinder K

    2012-03-01

    A subthreshold pharyngeal stimulus induces lower esophageal sphincter (LES) relaxation and inhibits progression of ongoing peristaltic contraction in the esophagus. Recent studies show that longitudinal muscle contraction of the esophagus may play a role in LES relaxation. Our goal was to determine whether a subthreshold pharyngeal stimulus induces contraction of the longitudinal muscle of the esophagus and to determine the nature of this contraction. Studies were conducted in 16 healthy subjects. High resolution manometry (HRM) recorded pressures, and high frequency intraluminal ultrasound (HFIUS) images recorded longitudinal muscle contraction at various locations in the esophagus. Subthreshold pharyngeal stimulation was induced by injection of minute amounts of water in the pharynx. A subthreshold pharyngeal stimulus induced strong contraction and caudal descent of the upper esophageal sphincter (UES) along with relaxation of the LES. HFIUS identified longitudinal muscle contraction of the proximal (3-5 cm below the UES) but not the distal esophagus. Pharyngeal stimulus, following a dry swallow, blocked the progression of dry swallow-induced peristalsis; this was also associated with UES contraction and descent along with the contraction of longitudinal muscle of the proximal esophagus. We identify a unique pattern of longitudinal muscle contraction of the proximal esophagus in response to subthreshold pharyngeal stimulus, which we propose may be responsible for relaxation of the distal esophagus and LES through the stretch sensitive activation of myenteric inhibitory motor neurons.

  16. A novel pattern of longitudinal muscle contraction with subthreshold pharyngeal stimulus: a possible mechanism of lower esophageal sphincter relaxation

    PubMed Central

    Leslie, Eric; Bhargava, Valmik

    2012-01-01

    A subthreshold pharyngeal stimulus induces lower esophageal sphincter (LES) relaxation and inhibits progression of ongoing peristaltic contraction in the esophagus. Recent studies show that longitudinal muscle contraction of the esophagus may play a role in LES relaxation. Our goal was to determine whether a subthreshold pharyngeal stimulus induces contraction of the longitudinal muscle of the esophagus and to determine the nature of this contraction. Studies were conducted in 16 healthy subjects. High resolution manometry (HRM) recorded pressures, and high frequency intraluminal ultrasound (HFIUS) images recorded longitudinal muscle contraction at various locations in the esophagus. Subthreshold pharyngeal stimulation was induced by injection of minute amounts of water in the pharynx. A subthreshold pharyngeal stimulus induced strong contraction and caudal descent of the upper esophageal sphincter (UES) along with relaxation of the LES. HFIUS identified longitudinal muscle contraction of the proximal (3–5 cm below the UES) but not the distal esophagus. Pharyngeal stimulus, following a dry swallow, blocked the progression of dry swallow-induced peristalsis; this was also associated with UES contraction and descent along with the contraction of longitudinal muscle of the proximal esophagus. We identify a unique pattern of longitudinal muscle contraction of the proximal esophagus in response to subthreshold pharyngeal stimulus, which we propose may be responsible for relaxation of the distal esophagus and LES through the stretch sensitive activation of myenteric inhibitory motor neurons. PMID:22173917

  17. Effect of endothelin-1 on the serotonin-induced contraction of smooth muscle in the guinea pig trachea.

    PubMed

    Yoshida, M; Aizawa, H; Hara, N

    1999-01-01

    Endothelin (ET), a potent constrictor of smooth muscle including that of the airways, may contribute to the development of airway hyperresponsiveness. To investigate the role of ET-1 on the airway smooth muscle, we examined the effects of ET-1 on the serotonin-induced contraction of guinea pig tracheal smooth muscle. The changes in isometric tension evoked by serotonin were measured before and after the application of a subthreshold dose (a dose which did not induce smooth muscle contraction by itself) of ET-1. Serotonin caused smooth muscle contraction in a dose-dependent manner. The subthreshold doses of ET-1 (1 pM) and sarafotoxin 6c (1 pM), a selective ETB receptor agonist, were found to potentiate significantly the contraction induced by serotonin. A potentiating effect of ET-1 was not altered by indomethacin or calphostin C, a protein kinase C inhibitor. These results suggest that a subthreshold concentration of ET-1 can potentiate serotonin-induced contraction of smooth muscle through the activation of ETB receptor, while in contrast cyclooxygenase and protein kinase C were found not to be involved in this mechanism.

  18. Calcium influx through L-type channels attenuates skeletal muscle contraction via inhibition of adenylyl cyclases.

    PubMed

    Menezes-Rodrigues, Francisco Sandro; Pires-Oliveira, Marcelo; Duarte, Thiago; Paredes-Gamero, Edgar Julian; Chiavegatti, Tiago; Godinho, Rosely Oliveira

    2013-11-15

    Skeletal muscle contraction is triggered by acetylcholine induced release of Ca(2+) from sarcoplasmic reticulum. Although this signaling pathway is independent of extracellular Ca(2+), L-type voltage-gated calcium channel (Cav) blockers have inotropic effects on frog skeletal muscles which occur by an unknown mechanism. Taking into account that skeletal muscle fiber expresses Ca(+2)-sensitive adenylyl cyclase (AC) isoforms and that cAMP is able to increase skeletal muscle contraction force, we investigated the role of Ca(2+) influx on mouse skeletal muscle contraction and the putative crosstalk between extracellular Ca(2+) and intracellular cAMP signaling pathways. The effects of Cav blockers (verapamil and nifedipine) and extracellular Ca(2+) chelator EGTA were evaluated on isometric contractility of mouse diaphragm muscle under direct electrical stimulus (supramaximal voltage, 2 ms, 0.1 Hz). Production of cAMP was evaluated by radiometric assay while Ca(2+) transients were assessed by confocal microscopy using L6 cells loaded with fluo-4/AM. Ca(2+) channel blockers verapamil and nifedipine had positive inotropic effect, which was mimicked by removal of extracellular Ca(+2) with EGTA or Ca(2+)-free Tyrode. While phosphodiesterase inhibitor IBMX potentiates verapamil positive inotropic effect, it was abolished by AC inhibitors SQ22536 and NYK80. Finally, the inotropic effect of verapamil was associated with increased intracellular cAMP content and mobilization of intracellular Ca(2+), indicating that positive inotropic effects of Ca(2+) blockers depend on cAMP formation. Together, our results show that extracellular Ca(2+) modulates skeletal muscle contraction, through inhibition of Ca(2+)-sensitive AC. The cross-talk between extracellular calcium and cAMP-dependent signaling pathways appears to regulate the extent of skeletal muscle contraction responses. © 2013 Published by Elsevier B.V.

  19. Effect of 3-substituted 1,4-benzodiazepin-2-ones on bradykinin-induced smooth muscle contraction.

    PubMed

    Virych, P A; Shelyuk, O V; Kabanova, T A; Khalimova, E I; Martynyuk, V S; Pavlovsky, V I; Andronati, S A

    2017-01-01

    Biochemical properties of 3-substituted 1,4-benzodiazepine determined by the characteristics of their chemical structure. Influence of 3-substituted 1,4-benzodiazepin-2-ones on maximal normalized rate and amplitudes of isometric smooth muscle contraction in rats was investigated. Compounds MX-1775 and MX-1828 demonstrated the similar inhibition effect on bradykinin-induced contraction of smooth muscle like competitive inhibitor des-arg9-bradykinin-acetate to bradykinin B2-receptors. MX-1626 demonstrated unidirectional changes of maximal normalized rate and force of smooth muscle that proportionally depended on bradykinin concentration in the range 10-10-10-6 M. MX-1828 has statistically significant decrease of normalized rate of smooth muscle contraction for bradykinin concentrations 10-10 and 10-9 M by 20.7 and 8.6%, respectively, but for agonist concentration 10-6 M, this parameter increased by 10.7% and amplitude was reduced by 29.5%. Compounds MX-2011, MX-1785 and MX-2004 showed no natural effect on bradykinin-induced smooth muscle contraction. Compounds MX-1775, MX-1828, MX-1626 were selected for further research of their influence on kinin-kallikrein system and pain perception.

  20. Operative correction of abdominal rectus diastasis (ARD) reduces pain and improves abdominal wall muscle strength: A randomized, prospective trial comparing retromuscular mesh repair to double-row, self-retaining sutures.

    PubMed

    Emanuelsson, Peter; Gunnarsson, Ulf; Dahlstrand, Ursula; Strigård, Karin; Stark, Birgit

    2016-11-01

    The primary aim of this prospective, randomized, clinical, 2-armed trial was to evaluate the risk for recurrence using 2 different operative techniques for repair of abdominal rectus diastasis. Secondary aims were comparison of pain, abdominal muscle strength, and quality of life and to compare those outcomes to a control group receiving physical training only. Eighty-six patients were enrolled. Twenty-nine patients were allocated to retromuscular polypropylene mesh and 27 to double-row plication with Quill technology. Thirty-two patients participated in a 3-month training program. Diastasis was evaluated with computed tomography scan and clinically. Pain was assessed using the ventral hernia pain questionnaire, a quality-of-life survey, SF-36, and abdominal muscle strength using the Biodex System-4. One early recurrence occurred in the Quill group, 2 encapsulated seromas in the mesh group, and 3 in the suture group. Significant improvements in perceived pain, the ventral hernia pain questionnaire, and quality of life appeared at the 1-year follow-up with no difference between the 2 operative groups. Significant muscular improvement was obtained in all groups (Biodex System-4). Patient perceived gain in muscle strength assessed with a visual analog scale improved similarly in both operative groups. This improvement was significantly greater than that seen in the training group. Patients in the training group still experienced bodily pain at follow-up. There was no difference between the Quill technique and retromuscular mesh in the effect on abdominal wall stability, with a similar complication rate 1 year after operation. An operation improves functional ability and quality of life. Training strengthens the abdominal muscles, but patients still experience discomfort and pain. Copyright © 2016 Elsevier Inc. All rights reserved.

  1. Nanosecond electric pulses modulate skeletal muscle calcium dynamics and contraction

    NASA Astrophysics Data System (ADS)

    Valdez, Chris; Jirjis, Michael B.; Roth, Caleb C.; Barnes, Ronald A.; Ibey, Bennett L.

    2017-02-01

    Irreversible electroporation therapy is utilized to remove cancerous tissues thru the delivery of rapid (250Hz) and high voltage (V) (1,500V/cm) electric pulses across microsecond durations. Clinical research demonstrated that bipolar (BP) high voltage microsecond pulses opposed to monophasic waveforms relieve muscle contraction during electroporation treatment. Our group along with others discovered that nanosecond electric pulses (nsEP) can activate second messenger cascades, induce cytoskeletal rearrangement, and depending on the nsEP duration and frequency, initiate apoptotic pathways. Of high interest across in vivo and in vitro applications, is how nsEP affects muscle physiology, and if nuances exist in comparison to longer duration electroporation applications. To this end, we exposed mature skeletal muscle cells to monopolar (MP) and BP nsEP stimulation across a wide range of electric field amplitudes (1-20 kV/cm). From live confocal microscopy, we simultaneously monitored intracellular calcium dynamics along with nsEP-induced muscle movement on a single cell level. In addition, we also evaluated membrane permeability with Yo-PRO-1 and Propidium Iodide (PI) across various nsEP parameters. The results from our findings suggest that skeletal muscle calcium dynamics, and nsEP-induced contraction exhibit exclusive responses to both MP and BP nsEP exposure. Overall the results suggest in vivo nsEP application may elicit unique physiology and field applications compared to longer pulse duration electroporation.

  2. Decreased Respiratory Muscle Function Is Associated with Impaired Trunk Balance among Chronic Stroke Patients: A Cross-sectional Study.

    PubMed

    Lee, Kyeongbong; Cho, Ji-Eun; Hwang, Dal-Yeon; Lee, WanHee

    2018-06-01

    The abdominal muscles play a role in trunk balance. Abdominal muscle thickness is asymmetrical in stroke survivors, who also have decreased respiratory muscle function. We compared the thickness of the abdominal muscles between the affected and less affected sides in stroke survivors. In addition, the relationship between respiratory muscle function and trunk balance was evaluated. Chronic stroke patients (18 men, 15 women; mean age, 58.94 ± 12.30 years; Mini-Mental Status Examination score ≥ 24) who could sit without assist were enrolled. Abdominal muscle thickness during rest and contraction was measured with ultrasonography, and the thickening ratio was calculated. Respiratory muscle function assessment included maximum respiratory pressure, peak flow, and air volume. Trunk function was evaluated using the Trunk Impairment Scale, and trunk balance was estimated based on the center of pressure velocity and path length within the limit of stability in sitting posture. Abdominal muscles were significantly thinner on the affected side, and the thickening ratio was lower in the affected side (P < 0.05). In addition, the higher thickening ratio of the affected side showed significant relationship with higher trunk function. Moreover, higher respiratory muscle function was significantly correlated with higher level of trunk function and balance in stroke patients (P < 0.05). Thus, chronic stroke survivors have decreased abdominal muscle thickness on the affected side, and respiratory muscle function has positive correlation with trunk function and balance. We propose that respiratory muscle training should be included as part of trunk balance training in chronic stroke patients.

  3. Caffeine and contraction synergistically stimulate 5′-AMP-activated protein kinase and insulin-independent glucose transport in rat skeletal muscle

    PubMed Central

    Tsuda, Satoshi; Egawa, Tatsuro; Kitani, Kazuto; Oshima, Rieko; Ma, Xiao; Hayashi, Tatsuya

    2015-01-01

    5′-Adenosine monophosphate-activated protein kinase (AMPK) has been identified as a key mediator of contraction-stimulated insulin-independent glucose transport in skeletal muscle. Caffeine acutely stimulates AMPK in resting skeletal muscle, but it is unknown whether caffeine affects AMPK in contracting muscle. Isolated rat epitrochlearis muscle was preincubated and then incubated in the absence or presence of 3 mmol/L caffeine for 30 or 120 min. Electrical stimulation (ES) was used to evoke tetanic contractions during the last 10 min of the incubation period. The combination of caffeine plus contraction had additive effects on AMPKα Thr172 phosphorylation, α-isoform-specific AMPK activity, and 3-O-methylglucose (3MG) transport. In contrast, caffeine inhibited basal and contraction-stimulated Akt Ser473 phosphorylation. Caffeine significantly delayed muscle fatigue during contraction, and the combination of caffeine and contraction additively decreased ATP and phosphocreatine contents. Caffeine did not affect resting tension. Next, rats were given an intraperitoneal injection of caffeine (60 mg/kg body weight) or saline, and the extensor digitorum longus muscle was dissected 15 min later. ES of the sciatic nerve was performed to evoke tetanic contractions for 5 min before dissection. Similar to the findings from isolated muscles incubated in vitro, the combination of caffeine plus contraction in vivo had additive effects on AMPK phosphorylation, AMPK activity, and 3MG transport. Caffeine also inhibited basal and contraction-stimulated Akt phosphorylation in vivo. These findings suggest that caffeine and contraction synergistically stimulate AMPK activity and insulin-independent glucose transport, at least in part by decreasing muscle fatigue and thereby promoting energy consumption during contraction. PMID:26471759

  4. Contraction Sensing with Smart Braid McKibben Muscles

    PubMed Central

    Felt, Wyatt; Chin, Khai Yi; Remy, C. David

    2016-01-01

    The inherent compliance of soft fluidic actuators makes them attractive for use in wearable devices and soft robotics. Their flexible nature permits them to be used without traditional rotational or prismatic joints. Without these joints, however, measuring the motion of the actuators is challenging. Actuator-level sensors could improve the performance of continuum robots and robots with compliant or multi-degree-of-freedom joints. We make the reinforcing braid of a pneumatic artificial muscle (PAM or McKibben muscle) “smart” by weaving it from conductive, insulated wires. These wires form a solenoid-like circuit with an inductance that more than doubles over the PAM contraction. The reinforcing and sensing fibers can be used to measure the contraction of a PAM actuator with a simple, linear function of the measured inductance. Whereas other proposed self-sensing techniques rely on the addition of special elastomers or transducers, the technique presented in this work can be implemented without modifications of this kind. We present and experimentally validate two models for Smart Braid sensors based on the long solenoid approximation and the Neumann formula, respectively. We test a McKibben muscle made from a Smart Braid in quasistatic conditions with various end-loads and in dynamic conditions. We also test the performance of the Smart Braid sensor alongside steel. PMID:28503062

  5. The muscle contraction mode determines lymphangiogenesis differentially in rat skeletal and cardiac muscles by modifying local lymphatic extracellular matrix microenvironments.

    PubMed

    Greiwe, L; Vinck, M; Suhr, F

    2016-05-01

    Lymphatic vessels are of special importance for tissue homeostasis, and increases of their density may foster tissue regeneration. Exercise could be a relevant tool to increase lymphatic vessel density (LVD); however, a significant lack of knowledge remains to understand lymphangiogenesis in skeletal muscles upon training. Interestingly, training-induced lymphangiogenesis has never been studied in the heart. We studied lymphangiogenesis and LVD upon chronic concentric and chronic eccentric muscle contractions in both rat skeletal (Mm. Edl and Sol) and cardiac muscles. We found that LVD decreased in both skeletal muscles specifically upon eccentric training, while this contraction increased LVD in cardiac tissue. These observations were supported by opposing local remodelling of lymphatic vessel-specific extracellular matrix components in skeletal and cardiac muscles and protein levels of lymphatic markers (Lyve-1, Pdpn, Vegf-C/D). Confocal microscopy further revealed transformations of lymphatic vessels into vessels expressing both blood (Cav-1) and lymphatic (Vegfr-3) markers upon eccentric training specifically in skeletal muscles. In addition and phenotype supportive, we found increased inflammation (NF-κB/p65, Il-1β, Ifn-γ, Tnf-α and MPO(+) cells) in eccentrically stressed skeletal, but decreased levels in cardiac muscles. Our data provide novel mechanistic insights into lymphangiogenic processes in skeletal and cardiac muscles upon chronic muscle contraction modes and demonstrate that both tissues adapt in opposing manners specifically to eccentric training. These data are highly relevant for clinical applications, because eccentric training serves as a sufficient strategy to increase LVD and to decrease inflammation in cardiac tissue, for example in order to reduce tissue abortion in transplantation settings. © 2015 Scandinavian Physiological Society. Published by John Wiley & Sons Ltd.

  6. Non-muscle (NM) myosin heavy chain phosphorylation regulates the formation of NM myosin filaments, adhesome assembly and smooth muscle contraction.

    PubMed

    Zhang, Wenwu; Gunst, Susan J

    2017-07-01

    Non-muscle (NM) and smooth muscle (SM) myosin II are both expressed in smooth muscle tissues, however the role of NM myosin in SM contraction is unknown. Contractile stimulation of tracheal smooth muscle tissues stimulates phosphorylation of the NM myosin heavy chain on Ser1943 and causes NM myosin filament assembly at the SM cell cortex. Expression of a non-phosphorylatable NM myosin mutant, NM myosin S1943A, in SM tissues inhibits ACh-induced NM myosin filament assembly and SM contraction, and also inhibits the assembly of membrane adhesome complexes during contractile stimulation. NM myosin regulatory light chain (RLC) phosphorylation but not SM myosin RLC phosphorylation is regulated by RhoA GTPase during ACh stimulation, and NM RLC phosphorylation is required for NM myosin filament assembly and SM contraction. NM myosin II plays a critical role in airway SM contraction that is independent and distinct from the function of SM myosin. The molecular function of non-muscle (NM) isoforms of myosin II in smooth muscle (SM) tissues and their possible role in contraction are largely unknown. We evaluated the function of NM myosin during contractile stimulation of canine tracheal SM tissues. Stimulation with ACh caused NM myosin filament assembly, as assessed by a Triton solubility assay and a proximity ligation assay aiming to measure interactions between NM myosin monomers. ACh stimulated the phosphorylation of NM myosin heavy chain on Ser1943 in tracheal SM tissues, which can regulate NM myosin IIA filament assembly in vitro. Expression of the non-phosphorylatable mutant NM myosin S1943A in SM tissues inhibited ACh-induced endogenous NM myosin Ser1943 phosphorylation, NM myosin filament formation, the assembly of membrane adhesome complexes and tension development. The NM myosin cross-bridge cycling inhibitor blebbistatin suppressed adhesome complex assembly and SM contraction without inhibiting NM myosin Ser1943 phosphorylation or NM myosin filament assembly. Rho

  7. AMPKα2 deficiency uncovers time dependency in the regulation of contraction-induced palmitate and glucose uptake in mouse muscle.

    PubMed

    Abbott, Marcia J; Bogachus, Lindsey D; Turcotte, Lorraine P

    2011-07-01

    AMP-activated protein kinase (AMPK) is a fuel sensor in skeletal muscle with multiple downstream signaling targets that may be triggered by increases in intracellular Ca(2+) concentration ([Ca(2+)]). The purpose of this study was to determine whether increases in intracellular [Ca(2+)] induced by caffeine act solely via AMPKα(2) and whether AMPKα(2) is essential to increase glucose uptake, fatty acid (FA) uptake, and FA oxidation in contracting skeletal muscle. Hindlimbs from wild-type (WT) or AMPKα(2) dominant-negative (DN) transgene mice were perfused during rest (n = 11), treatment with 3 mM caffeine (n = 10), or muscle contraction (n = 11). Time-dependent effects on glucose and FA uptake were uncovered throughout the 20-min muscle contraction perfusion period (P < 0.05). Glucose uptake rates did not increase in DN mice during muscle contraction until the last 5 min of the protocol (P < 0.05). FA uptake rates were elevated at the onset of muscle contraction and diminished by the end of the protocol in DN mice (P < 0.05). FA oxidation rates were abolished in the DN mice during muscle contraction (P < 0.05). The DN transgene had no effect on caffeine-induced FA uptake and oxidation (P > 0.05). Glucose uptake rates were blunted in caffeine-treated DN mice (P < 0.05). The DN transgene resulted in a greater use of intramuscular triglycerides as a fuel source during muscle contraction. The DN transgene did not alter caffeine- or contraction-mediated changes in the phosphorylation of Ca(2+)/calmodulin-dependent protein kinase I or ERK1/2 (P > 0.05). These data suggest that AMPKα(2) is involved in the regulation of substrate uptake in a time-dependent manner in contracting muscle but is not necessary for regulation of FA uptake and oxidation during caffeine treatment.

  8. A threshold-based approach for muscle contraction detection from surface EMG signals

    NASA Astrophysics Data System (ADS)

    Morantes, Gaudi; Fernández, Gerardo; Altuve, Miguel

    2013-11-01

    Surface electromyographic (SEMG) signals are commonly used as control signals in prosthetic and orthotic devices. Super cial electrodes are placed on the skin of the subject to acquire its muscular activity through this signal. The muscle contraction episode is then in charge of activating and deactivating these devices. Nevertheless, there is no gold standard" to detect muscle contraction, leading to delayed responses and false and missed detections. This fact motivated us to propose a new approach that compares a smoothed version of the SEMG signal with a xed threshold, in order to detect muscle contraction episodes. After preprocessing the SEMG signal, the smoothed version is obtained using a moving average lter, where three di erent window lengths has been evaluated. The detector was tuned by maximizing sensitivity and speci city and evaluated using SEMG signals obtained from the anterior tibial and gastrocnemius muscles, taken during the walking of ve subjects. Compared with traditional detection methods, we obtain a reduction of 3 ms in the detection delay, an increase of 8% in sensitivity but a decrease of 15% in speci city. Future work is directed to the inclusion of a temporal threshold (a double-threshold approach) to minimize false detections and reduce detection delays.

  9. Role of rho-kinase (ROCK) in tonic but not phasic contraction in the frog stomach smooth muscle.

    PubMed

    Sahin, Leyla; Cevik, Ozge Selin; Koyuncu, Dilan Deniz; Buyukafsar, Kansu

    2018-04-01

    Rho/Rho-kinase (ROCK) signaling has extensively been shown to take part in mammalian smooth muscle contractions in response to diverse agents yet its role in the contraction of amphibian smooth muscle has not been investigated. Therefore, we aimed to explore any role of this pathway in the contractions of frog stomach smooth. The strips were prepared and suspended in organ baths filled with Ringer solution. Changes in the circular strips of the frog stomach muscle length were recorded isotonically with a force transducer in organ baths. Carbachol (CCh) exerted both phasic and tonic contractions. In contrast, atropin abolished all types of contractions by CCh. The phasic contractions were suppressed by a Ca 2+ channel blocker, nifedipine but not by the ROCK inhibitor, Y-27632. However, the tonic contractions were markedly attenuated by Y-27632. Selective M 1 receptor blocker, pirenzepin, selective M 3 receptor blocker and DAMP had no effects on CCh-elicited contractions. On the other hand, selective M 2 receptor blocker, AF-DX suppressed all types of contractile activity by CCh. These data suggest that M 2 receptor activation could mainly mediate CCh-induced phasic and tonic contractions, and ROCK seems to be involved in the CCh-induced tonic but not phasic contractions of the frog stomach smooth muscle. Copyright © 2018 Elsevier Inc. All rights reserved.

  10. Differences in time to peak carbachol-induced contractions between circular and longitudinal smooth muscles of mouse ileum.

    PubMed

    Azuma, Yasu-Taka; Samezawa, Nanako; Nishiyama, Kazuhiro; Nakajima, Hidemitsu; Takeuchi, Tadayoshi

    2016-01-01

    The muscular layer in the GI tract consists of an inner circular muscular layer and an outer longitudinal muscular layer. Acetylcholine (ACh) is the representative neurotransmitter that causes contractions in the gastrointestinal tracts of most animal species. There are many reports of muscarinic receptor-mediated contraction of longitudinal muscles, but few studies discuss circular muscles. The present study detailed the contractile response in the circular smooth muscles of the mouse ileum. We used small muscle strips (0.2 mm × 1 mm) and large muscle strips (4 × 4 mm) isolated from the circular and longitudinal muscle layers of the mouse ileum to compare contraction responses in circular and longitudinal smooth muscles. The time to peak contractile responses to carbamylcholine (CCh) were later in the small muscle strips (0.2 × 1 mm) of circular muscle (5.7 min) than longitudinal muscles (0.4 min). The time to peak contractile responses to CCh in the large muscle strips (4 × 4 mm) were also later in the circular muscle (3.1 min) than the longitudinal muscle (1.4 min). Furthermore, a muscarinic M2 receptor antagonist and gap junction inhibitor significantly delayed the time to peak contraction of the large muscle strips (4 × 4 mm) from the circular muscular layer. Our findings indicate that muscarinic M2 receptors in the circular muscular layer of mouse ileum exert a previously undocumented function in gut motility via the regulation of gap junctions.

  11. Functional difference in short- and long-latency interhemispheric inhibitions from active to resting hemisphere during a unilateral muscle contraction.

    PubMed

    Uehara, Kazumasa; Morishita, Takuya; Kubota, Shinji; Hirano, Masato; Funase, Kozo

    2014-01-01

    The aim of the present study was to investigate whether there is a functional difference in short-latency (SIHI) and long-latency (LIHI) interhemispheric inhibition from the active to the resting primary motor cortex (M1) with paired-pulse transcranial magnetic stimulation during a unilateral muscle contraction. In nine healthy right-handed participants, IHI was tested from the dominant to the nondominant M1 and vice versa under resting conditions or during performance of a sustained unilateral muscle contraction with the right or left first dorsal interosseous muscle at 10% and 30% maximum voluntary contraction. To obtain measurements of SIHI and LIHI, a conditioning stimulus (CS) was applied over the M1 contralateral to the muscle contraction, followed by a test stimulus over the M1 ipsilateral to the muscle contraction at short (10 ms) and long (40 ms) interstimulus intervals. We used four CS intensities to investigate SIHI and LIHI from the active to the resting M1 systematically. The amount of IHI during the unilateral muscle contractions showed a significant difference between SIHI and LIHI, but the amount of IHI during the resting condition did not. In particular, SIHI during the muscle contractions, but not LIHI, significantly increased with increase in CS intensity compared with the resting condition. Laterality of IHI was not detected in any of the experimental conditions. The present study provides novel evidence that a functional difference between SIHI and LIHI from the active to the resting M1 exists during unilateral muscle contractions.

  12. Effect of muscle mass and intensity of isometric contraction on heart rate.

    PubMed

    Gálvez, J M; Alonso, J P; Sangrador, L A; Navarro, G

    2000-02-01

    The purpose of this study was to determine the effect of muscle mass and the level of force on the contraction-induced rise in heart rate. We conducted an experimental study in a sample of 28 healthy men between 20 and 30 yr of age (power: 95%, alpha: 5%). Smokers, obese subjects, and those who performed regular physical activity over a certain amount of energetic expenditure were excluded from the study. The participants exerted two types of isometric contractions: handgrip and turning a 40-cm-diameter wheel. Both were sustained to exhaustion at 20 and 50% of maximal force. Twenty-five subjects finished the experiment. Heart rate increased a mean of 15.1 beats/min [95% confidence interval (CI): 5.5-24.6] from 20 to 50% handgrip contractions, and 20.7 beats/min (95% CI: 11.9-29.5) from 20 to 50% wheel-turn contractions. Heart rate also increased a mean of 13.3 beats/min (95% CI: 10.4-16.1) from handgrip to wheel-turn contractions at 20% maximal force, and 18.9 beats/min (95% CI: 9. 8-28.0) from handgrip to wheel-turn contractions at 50% maximal force. We conclude that the magnitude of the heart rate increase during isometric exercise is related to the intensity of the contraction and the mass of the contracted muscle.

  13. EMG-force relationship during static contraction: effects on sensor placement locations on biceps brachii muscle.

    PubMed

    Ahamed, Nizam Uddin; Sundaraj, Kenneth; Alqahtani, Mahdi; Altwijri, Omar; Ali, Md Asraf; Islam, Md Anamul

    2014-01-01

    The relationship between surface electromyography (EMG) and force have been the subject of ongoing investigations and remain a subject of controversy. Even under static conditions, the relationships at different sensor placement locations in the biceps brachii (BB) muscle are complex. The aim of this study was to compare the activity and relationship between surface EMG and static force from the BB muscle in terms of three sensor placement locations. Twenty-one right hand dominant male subjects (age 25.3±1.2 years) participated in the study. Surface EMG signals were detected from the subject's right BB muscle. The muscle activation during force was determined as the root mean square (RMS) electromyographic signal normalized to the peak RMS EMG signal of isometric contraction for 10 s. The statistical analysis included linear regression to examine the relationship between EMG amplitude and force of contraction [40-100% of maximal voluntary contraction (MVC)], repeated measures ANOVA to assess differences among the sensor placement locations, and coefficient of variation (CoV) for muscle activity variation. The results demonstrated that when the sensor was placed on the muscle belly, the linear slope coefficient was significantly greater for EMG versus force testing (r2=0.62, P<0.05) than when placed on the lower part (r2=0.31, P>0.05) and upper part of the muscle belly (r2=0.29, P<0.05). In addition, the EMG signal activity on the muscle belly had less variability than the upper and lower parts (8.55% vs. 15.12% and 12.86%, respectively). These findings indicate the importance of applying the surface EMG sensor at the appropriate locations that follow muscle fiber orientation of the BB muscle during static contraction. As a result, EMG signals of three different placements may help to understand the difference in the amplitude of the signals due to placement.

  14. Assessment of pelvic floor muscle contraction with palpation, perineometry and transperineal ultrasound: a cross-sectional study.

    PubMed

    Volløyhaug, I; Mørkved, S; Salvesen, Ø; Salvesen, K Å

    2016-06-01

    To study the correlation between palpation, perineometry and transperineal ultrasound for assessment of pelvic floor muscle contraction and to define a contraction scale for ultrasound measurements. This was a cross-sectional study of 608 women examined with palpation of pelvic floor muscle contraction, using the Modified Oxford Scale, and measurement of the vaginal squeeze pressure with a vaginal balloon connected to a fiber-optic microtip transducer (perineometry). Transperineal ultrasound was used for measurements of levator hiatal area and anteroposterior (AP) diameter in the plane of minimal hiatal dimensions, at rest and on contraction. The pelvic floor muscle contraction was expressed as the percentage difference between values at rest and on contraction. Spearman's rank was used to test for correlation between the different methods of assessment. Significant correlations were found between all assessment methods (P < 0.001). Palpation correlated with perineometry (rs = 0.74) and with proportional change in hiatal area (rs = 0.67) and AP diameter (rs = 0.69) on ultrasound. Perineometry correlated with proportional change in hiatal area (rs = 0.60) and AP diameter (rs = 0.66) on ultrasound. We defined a contraction scale based on the proportional change in AP diameter. In this population, a change in AP diameter of < 7% corresponded to absence of contractions, 7-18% corresponded to weak contractions, 18-35% corresponded to normal contractions and > 35% corresponded to strong contractions. We found moderate to strong correlation between ultrasound measurements, palpation and perineometry for assessing pelvic floor muscle contraction. The proportional change in levator hiatal AP diameter was the ultrasound measurement with strongest correlation to palpation and perineometry and formed the basis for the contraction scale for ultrasound measurements. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd. Copyright © 2015 ISUOG. Published by John Wiley

  15. Distinct Skeletal Muscle Gene Regulation from Active Contraction, Passive Vibration, and Whole Body Heat Stress in Humans

    PubMed Central

    Petrie, Michael A.; Kimball, Amy L.; McHenry, Colleen L.; Suneja, Manish; Yen, Chu-Ling; Sharma, Arpit; Shields, Richard K.

    2016-01-01

    Skeletal muscle exercise regulates several important metabolic genes in humans. We know little about the effects of environmental stress (heat) and mechanical stress (vibration) on skeletal muscle. Passive mechanical stress or systemic heat stress are often used in combination with many active exercise programs. We designed a method to deliver a vibration stress and systemic heat stress to compare the effects with active skeletal muscle contraction. Purpose: The purpose of this study is to examine whether active mechanical stress (muscle contraction), passive mechanical stress (vibration), or systemic whole body heat stress regulates key gene signatures associated with muscle metabolism, hypertrophy/atrophy, and inflammation/repair. Methods: Eleven subjects, six able-bodied and five with chronic spinal cord injury (SCI) participated in the study. The six able-bodied subjects sat in a heat stress chamber for 30 minutes. Five subjects with SCI received a single dose of limb-segment vibration or a dose of repetitive electrically induced muscle contractions. Three hours after the completion of each stress, we performed a muscle biopsy (vastus lateralis or soleus) to analyze mRNA gene expression. Results: We discovered repetitive active muscle contractions up regulated metabolic transcription factors NR4A3 (12.45 fold), PGC-1α (5.46 fold), and ABRA (5.98 fold); and repressed MSTN (0.56 fold). Heat stress repressed PGC-1α (0.74 fold change; p < 0.05); while vibration induced FOXK2 (2.36 fold change; p < 0.05). Vibration similarly caused a down regulation of MSTN (0.74 fold change; p < 0.05), but to a lesser extent than active muscle contraction. Vibration induced FOXK2 (p < 0.05) while heat stress repressed PGC-1α (0.74 fold) and ANKRD1 genes (0.51 fold; p < 0.05). Conclusion: These findings support a distinct gene regulation in response to heat stress, vibration, and muscle contractions. Understanding these responses may assist in developing regenerative

  16. Distinct Skeletal Muscle Gene Regulation from Active Contraction, Passive Vibration, and Whole Body Heat Stress in Humans.

    PubMed

    Petrie, Michael A; Kimball, Amy L; McHenry, Colleen L; Suneja, Manish; Yen, Chu-Ling; Sharma, Arpit; Shields, Richard K

    2016-01-01

    Skeletal muscle exercise regulates several important metabolic genes in humans. We know little about the effects of environmental stress (heat) and mechanical stress (vibration) on skeletal muscle. Passive mechanical stress or systemic heat stress are often used in combination with many active exercise programs. We designed a method to deliver a vibration stress and systemic heat stress to compare the effects with active skeletal muscle contraction. The purpose of this study is to examine whether active mechanical stress (muscle contraction), passive mechanical stress (vibration), or systemic whole body heat stress regulates key gene signatures associated with muscle metabolism, hypertrophy/atrophy, and inflammation/repair. Eleven subjects, six able-bodied and five with chronic spinal cord injury (SCI) participated in the study. The six able-bodied subjects sat in a heat stress chamber for 30 minutes. Five subjects with SCI received a single dose of limb-segment vibration or a dose of repetitive electrically induced muscle contractions. Three hours after the completion of each stress, we performed a muscle biopsy (vastus lateralis or soleus) to analyze mRNA gene expression. We discovered repetitive active muscle contractions up regulated metabolic transcription factors NR4A3 (12.45 fold), PGC-1α (5.46 fold), and ABRA (5.98 fold); and repressed MSTN (0.56 fold). Heat stress repressed PGC-1α (0.74 fold change; p < 0.05); while vibration induced FOXK2 (2.36 fold change; p < 0.05). Vibration similarly caused a down regulation of MSTN (0.74 fold change; p < 0.05), but to a lesser extent than active muscle contraction. Vibration induced FOXK2 (p < 0.05) while heat stress repressed PGC-1α (0.74 fold) and ANKRD1 genes (0.51 fold; p < 0.05). These findings support a distinct gene regulation in response to heat stress, vibration, and muscle contractions. Understanding these responses may assist in developing regenerative rehabilitation interventions to improve muscle cell

  17. The mechanical and chemical equations of motion of muscle contraction

    NASA Astrophysics Data System (ADS)

    Shiner, J. S.; Sieniutycz, Stanislaw

    1997-11-01

    Up to now no formulation of muscle contraction has provided both the chemical kinetic equations for the reactions responsible for the contraction and the mechanical equation of motion for the muscle. This has most likely been due to the lack of general formalisms for nonlinear systems with chemical-nonchemical coupling valid under the far from equilibrium conditions under which muscle operates physiologically. We have recently developed such formalisms and apply them here to the formulation of muscle contraction to obtain both the chemical and the mechanical equations. The standard formulation up to now has yielded only the dynamic equations for the chemical variables and has considered these to be functions of both time and an appropriate mechanical variable. The macroscopically observable quantities were then obtained by averaging over the mechanical variable. When attempting to derive the dynamics equations for both the chemistry and mechanics this choice of variables leads to conflicting results for the mechanical equation of motion when two different general formalisms are applied. The conflict can be resolved by choosing the variables such that both the chemical variables and the mechanical variables are considered to be functions of time alone. This adds one equation to the set of differential equations to be solved but is actually a simplification of the problem, since these equations are ordinary differential equations, not the partial differential equations of the now standard formulation, and since in this choice of variables the variables themselves are the macroscopic observables the procedure of averaging over the mechanical variable is eliminated. Furthermore, the parameters occurring in the equations at this level of description should be accessible to direct experimental determination.

  18. The relationship between cough-specific quality of life and abdominal muscle endurance, fatigue, and depression in patients with COPD.

    PubMed

    Arikan, Hulya; Savci, Sema; Calik-Kutukcu, Ebru; Vardar-Yagli, Naciye; Saglam, Melda; Inal-Ince, Deniz; Coplu, Lutfi

    2015-01-01

    Cough is a prevalent symptom that impacts quality of life in COPD. The aim of this study was to assess the relationship between cough-specific quality of life, abdominal muscle endurance, fatigue, and depression in stable patients with COPD. Twenty-eight patients with COPD (mean age 60.6±8.7 years) referred for pulmonary rehabilitation participated in this cross-sectional study. Sit-ups test was used for assessing abdominal muscle endurance. Leicester Cough Questionnaire (LCQ) was used to evaluate symptom-specific quality of life. Fatigue perception was evaluated with Fatigue Impact Scale (FIS). Beck Depression Inventory (BDI) was used for assessing depression level. The LCQ total score was significantly associated with number of sit-ups; BDI score; FIS total; physical, cognitive, and psychosocial scores (P<0.05). Scores of the LCQ physical, social, and psychological domains were also significantly related with number of sit-ups, FIS total score, and BDI score (P<0.05). FIS total score and number of sit-ups explained 58% of the variance in LCQ total score (r=0.76, r (2)=0.577, F(2-20)=12.296, P<0.001). Chronic cough may adversely affect performance in daily life due to its negative effect on fatigue and decrease abdominal muscle endurance in patients with COPD. Decreased cough-related quality of life is related with increased level of depression in COPD patients. Effects of increased abdominal muscle endurance and decreased fatigue in COPD patients with chronic cough need further investigation.

  19. Effects of hypoxia and glucose-removal condition on muscle contraction of the smooth muscles of porcine urinary bladder

    PubMed Central

    NAGAI, Yuta; KANEDA, Takeharu; MIYAMOTO, Yasuyuki; NURUKI, Takaomi; KANDA, Hidenori; URAKAWA, Norimoto; SHIMIZU, Kazumasa

    2015-01-01

    To elucidate the dependence of aerobic energy metabolism and utilization of glucose in contraction of urinary bladder smooth muscle, we investigated the changes in the reduced pyridine nucleotide (PNred) fluorescence, representing glycolysis activity, and determined the phosphocreatine (PCr) and ATP contents of the porcine urinary bladder during contractions induced by high K+ or carbachol (CCh) and with and without hypoxia (achieved by bubbling N2 instead of O2) or in a glucose-free condition. Hyperosmotic addition of 65 mM KCl (H-65K+) and 1 µM CCh induced a phasic contraction followed by a tonic contraction. A glucose-free physiological salt solution (PSS) did not change the subsequent contractile responses to H-65K+ and CCh. However, hypoxia significantly attenuated H-65K+- and CCh-induced contraction. H-65K+ and CCh induced a sustained increase in PNred fluorescence, representing glycolysis activity. Hypoxia enhanced H-65K+- and CCh-induced increases in PNred fluorescence, whereas glucose-free PSS decreased these increases, significantly. In the presence of H-65K+, hypoxia decreased the PCr and ATP contents; however, the glucose-free PSS did not change the PCr contents. In conclusion, we demonstrated that high K+- and CCh-induced contractions depend on aerobic metabolism and that an endogenous substrate may be utilized to maintain muscle contraction in a glucose-free PSS in the porcine urinary bladder. PMID:26369431

  20. Effects of hypoxia and glucose-removal condition on muscle contraction of the smooth muscles of porcine urinary bladder.

    PubMed

    Nagai, Yuta; Kaneda, Takeharu; Miyamoto, Yasuyuki; Nuruki, Takaomi; Kanda, Hidenori; Urakawa, Norimoto; Shimizu, Kazumasa

    2016-01-01

    To elucidate the dependence of aerobic energy metabolism and utilization of glucose in contraction of urinary bladder smooth muscle, we investigated the changes in the reduced pyridine nucleotide (PNred) fluorescence, representing glycolysis activity, and determined the phosphocreatine (PCr) and ATP contents of the porcine urinary bladder during contractions induced by high K(+) or carbachol (CCh) and with and without hypoxia (achieved by bubbling N2 instead of O2) or in a glucose-free condition. Hyperosmotic addition of 65 mM KCl (H-65K(+)) and 1 µM CCh induced a phasic contraction followed by a tonic contraction. A glucose-free physiological salt solution (PSS) did not change the subsequent contractile responses to H-65K(+) and CCh. However, hypoxia significantly attenuated H-65K(+)- and CCh-induced contraction. H-65K(+) and CCh induced a sustained increase in PNred fluorescence, representing glycolysis activity. Hypoxia enhanced H-65K(+)- and CCh-induced increases in PNred fluorescence, whereas glucose-free PSS decreased these increases, significantly. In the presence of H-65K(+), hypoxia decreased the PCr and ATP contents; however, the glucose-free PSS did not change the PCr contents. In conclusion, we demonstrated that high K(+)- and CCh-induced contractions depend on aerobic metabolism and that an endogenous substrate may be utilized to maintain muscle contraction in a glucose-free PSS in the porcine urinary bladder.

  1. Evoked EMG versus Muscle Torque during Fatiguing Functional Electrical Stimulation-Evoked Muscle Contractions and Short-Term Recovery in Individuals with Spinal Cord Injury

    PubMed Central

    Estigoni, Eduardo H.; Fornusek, Che; Hamzaid, Nur Azah; Hasnan, Nazirah; Smith, Richard M.; Davis, Glen M.

    2014-01-01

    This study investigated whether the relationship between muscle torque and m-waves remained constant after short recovery periods, between repeated intervals of isometric muscle contractions induced by functional electrical stimulation (FES). Eight subjects with spinal cord injury (SCI) were recruited for the study. All subjects had their quadriceps muscles group stimulated during three sessions of isometric contractions separated by 5 min of recovery. The evoked-electromyographic (eEMG) signals, as well as the produced torque, were synchronously acquired during the contractions and during short FES bursts applied during the recovery intervals. All analysed m-wave variables changed progressively throughout the three contractions, even though the same muscle torque was generated. The peak to peak amplitude (PtpA), and the m-wave area (Area) were significantly increased, while the time between the stimulus artefact and the positive peak (PosT) were substantially reduced when the muscles became fatigued. In addition, all m-wave variables recovered faster and to a greater extent than did torque after the recovery intervals. We concluded that rapid recovery intervals between FES-evoked exercise sessions can radically interfere in the use of m-waves as a proxy for torque estimation in individuals with SCI. This needs to be further investigated, in addition to seeking a better understanding of the mechanisms of muscle fatigue and recovery. PMID:25479324

  2. Evoked EMG versus muscle torque during fatiguing functional electrical stimulation-evoked muscle contractions and short-term recovery in individuals with spinal cord injury.

    PubMed

    Estigoni, Eduardo H; Fornusek, Che; Hamzaid, Nur Azah; Hasnan, Nazirah; Smith, Richard M; Davis, Glen M

    2014-12-03

    This study investigated whether the relationship between muscle torque and m-waves remained constant after short recovery periods, between repeated intervals of isometric muscle contractions induced by functional electrical stimulation (FES). Eight subjects with spinal cord injury (SCI) were recruited for the study. All subjects had their quadriceps muscles group stimulated during three sessions of isometric contractions separated by 5 min of recovery. The evoked-electromyographic (eEMG) signals, as well as the produced torque, were synchronously acquired during the contractions and during short FES bursts applied during the recovery intervals. All analysed m-wave variables changed progressively throughout the three contractions, even though the same muscle torque was generated. The peak to peak amplitude (PtpA), and the m-wave area (Area) were significantly increased, while the time between the stimulus artefact and the positive peak (PosT) were substantially reduced when the muscles became fatigued. In addition, all m-wave variables recovered faster and to a greater extent than did torque after the recovery intervals. We concluded that rapid recovery intervals between FES-evoked exercise sessions can radically interfere in the use of m-waves as a proxy for torque estimation in individuals with SCI. This needs to be further investigated, in addition to seeking a better understanding of the mechanisms of muscle fatigue and recovery.

  3. Contraction-induced changes in acetyl-CoA carboxylase and 5'-AMP-activated kinase in skeletal muscle.

    PubMed

    Vavvas, D; Apazidis, A; Saha, A K; Gamble, J; Patel, A; Kemp, B E; Witters, L A; Ruderman, N B

    1997-05-16

    The concentration of malonyl-CoA, a negative regulator of fatty acid oxidation, diminishes acutely in contracting skeletal muscle. To determine how this occurs, the activity and properties of acetyl-CoA carboxylase beta (ACC-beta), the skeletal muscle isozyme that catalyzes malonyl-CoA formation, were examined in rat gastrocnemius-soleus muscles at rest and during contractions induced by electrical stimulation of the sciatic nerve. To avoid the problem of contamination of the muscle extract by mitochondrial carboxylases, an assay was developed in which ACC-beta was first purified by immunoprecipitation with a monoclonal antibody. ACC-beta was quantitatively recovered in the immunopellet and exhibited a high sensitivity to citrate (12-fold activation) and a Km for acetyl-CoA (120 microM) similar to that reported for ACC-beta purified by other means. After 5 min of contraction, ACC-beta activity was decreased by 90% despite an apparent increase in the cytosolic concentration of citrate, a positive regulator of ACC. SDS-polyacrylamide gel electrophoresis of both homogenates and immunopellets from these muscles showed a decrease in the electrophoretic mobility of ACC, suggesting that phosphorylation could account for the decrease in ACC activity. In keeping with this notion, citrate activation of ACC purified from contracting muscle was markedly depressed. In addition, homogenization of the muscles in a buffer free of phosphatase inhibitors and containing the phosphatase activators glutamate and MgCl2 or treatment of immunoprecipitated ACC-beta with purified protein phosphatase 2A abolished the decreases in both ACC-beta activity and electrophoretic mobility caused by contraction. The rapid decrease in ACC-beta activity after the onset of contractions (50% by 20 s) and its slow restoration to initial values during recovery (60-90 min) were paralleled temporally by reciprocal changes in the activity of the alpha2 but not the alpha1 isoform of 5'-AMP-activated protein

  4. The work of titin protein folding as a major driver in muscle contraction

    PubMed Central

    Eckels, Edward C.; Tapia-Rojo, Rafael; Rivas-Pardo, Jamie Andrés; Fernández, Julio M.

    2018-01-01

    Single molecule atomic force microscopy and magnetic tweezers experiments have demonstrated that titin Ig domains are capable of folding against a pulling force, generating mechanical work which exceeds that produced by a myosin motor. We hypothesize that upon muscle activation, formation of actomyosin crossbridges reduces the force on titin causing entropic recoil of the titin polymer and triggering the folding of the titin Ig domains. In the physiological force range of 4–15 pN under which titin operates in muscle, the folding contraction of a single Ig domain can generate 200% of the work of entropic recoil, and occurs at forces which exceed the maximum stalling force of single myosin motors. Thus titin operates like a mechanical battery storing elastic energy efficiently by unfolding Ig domains, and delivering the charge back by folding when the motors are activated during a contraction. We advance the hypothesis that titin folding and myosin activation act as inextricable partners during muscle contraction. PMID:29433413

  5. Effect of oxidative stress on Rho kinase II and smooth muscle contraction in rat stomach.

    PubMed

    Al-Shboul, Othman; Mustafa, Ayman

    2015-06-01

    Recent studies have shown that both Rho kinase signaling and oxidative stress are involved in the pathogenesis of a number of human diseases, such as diabetes mellitus, hypertension, and atherosclerosis. However, very little is known about the effect of oxidative stress on the gastrointestinal (GI) smooth muscle Rho kinase pathway. The aim of the current study was to investigate the effect of oxidative stress on Rho kinase II and muscle contraction in rat stomach. The peroxynitrite donor 3-morpholinosydnonimine (SIN-1), hydrogen peroxide (H2O2), and peroxynitrite were used to induce oxidative stress. Rho kinase II expression and ACh-induced activity were measured in control and oxidant-treated cells via specifically designed enzyme-linked immunosorbent assay (ELISA) and activity assay kits, respectively. Single smooth muscle cell contraction was measured via scanning micrometry in the presence or absence of the Rho kinase blocker, Y-27632 dihydrochloride. All oxidant agents significantly increased ACh-induced Rho kinase II activity without affecting its expression level. Most important, oxidative stress induced by all three agents augmented ACh-stimulated muscle cell contraction, which was significantly inhibited by Y-27632. In conclusion, oxidative stress activates Rho kinase II and enhances contraction in rat gastric muscle, suggesting an important role in GI motility disorders associated with oxidative stress.

  6. Passive mechanical properties of rat abdominal wall muscles suggest an important role of the extracellular connective tissue matrix.

    PubMed

    Brown, Stephen H M; Carr, John Austin; Ward, Samuel R; Lieber, Richard L

    2012-08-01

    Abdominal wall muscles have a unique morphology suggesting a complex role in generating and transferring force to the spinal column. Studying passive mechanical properties of these muscles may provide insights into their ability to transfer force among structures. Biopsies from rectus abdominis (RA), external oblique (EO), internal oblique (IO), and transverse abdominis (TrA) were harvested from male Sprague-Dawley rats, and single muscle fibers and fiber bundles (4-8 fibers ensheathed in their connective tissue matrix) were isolated and mechanically stretched in a passive state. Slack sarcomere lengths were measured and elastic moduli were calculated from stress-strain data. Titin molecular mass was also measured from single muscle fibers. No significant differences were found among the four abdominal wall muscles in terms of slack sarcomere length or elastic modulus. Interestingly, across all four muscles, slack sarcomere lengths were quite long in individual muscle fibers (>2.4 µm), and demonstrated a significantly longer slack length in comparison to fiber bundles (p < 0.0001). Also, the extracellular connective tissue matrix provided a stiffening effect and enhanced the resistance to lengthening at long muscle lengths. Titin molecular mass was significantly less in TrA compared to each of the other three muscles (p < 0.0009), but this difference did not correspond to hypothesized differences in stiffness. Copyright © 2012 Orthopaedic Research Society.

  7. Electromechanical delay components during skeletal muscle contraction and relaxation in patients with myotonic dystrophy type 1.

    PubMed

    Esposito, Fabio; Cè, Emiliano; Rampichini, Susanna; Limonta, Eloisa; Venturelli, Massimo; Monti, Elena; Bet, Luciano; Fossati, Barbara; Meola, Giovanni

    2016-01-01

    The electromechanical delay during muscle contraction and relaxation can be partitioned into mainly electrochemical and mainly mechanical components by an EMG, mechanomyographic, and force combined approach. Component duration and measurement reliability were investigated during contraction and relaxation in a group of patients with myotonic dystrophy type 1 (DM1, n = 13) and in healthy controls (n = 13). EMG, mechanomyogram, and force were recorded in DM1 and in age- and body-matched controls from tibialis anterior (distal muscle) and vastus lateralis (proximal muscle) muscles during maximum voluntary and electrically-evoked isometric contractions. The electrochemical and mechanical components of the electromechanical delay during muscle contraction and relaxation were calculated off-line. Maximum strength was significantly lower in DM1 than in controls under both experimental conditions. All electrochemical and mechanical components were significantly longer in DM1 in both muscles. Measurement reliability was very high in both DM1 and controls. The high reliability of the measurements and the differences between DM1 patients and controls suggest that the EMG, mechanomyographic, and force combined approach could be utilized as a valid tool to assess the level of neuromuscular dysfunction in this pathology, and to follow the efficacy of pharmacological or non-pharmacological interventions. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. QUADRICEPS LOW FREQUENCY FATIGUE AND MUSCLE PAIN ARE CONTRACTION TYPE DEPENDENT

    PubMed Central

    Iguchi, Masaki; Shields, Richard K.

    2010-01-01

    Introduction Eccentric contractions are thought to induce greater low frequency fatigue (LFF) and delayed onset muscle soreness (DOMS) than concentric contractions. This study induced a similar amount of eccentric quadriceps muscle fatigue during either a concentric or eccentric fatigue task to compare LFF and DOMS. Methods Subjects (n=22) performed concentric or eccentric fatigue tasks using 75% of the pre-fatigue maximal voluntary contraction (MVC) torque, and both tasks ended when the MVC eccentric torque decreased by 25% pre-fatigue. Results When subjects reached the failure criterion during the eccentric and concentric tasks, the concentric MVC was 78 ± 9.8% and 64 ± 8.4% of initial, respectively. LFF was greater after the concentric than the eccentric protocols (22 ± 12.4% and 15 ± 7.6% increase, respectively; p < 0.01). DOMS was over 100% greater for the eccentric protocol. Discussion These results indicate that DOMS is not dependent on the events that contribute to LFF. PMID:20544933

  9. Role of the adapter protein Abi1 in actin-associated signaling and smooth muscle contraction.

    PubMed

    Wang, Tao; Cleary, Rachel A; Wang, Ruping; Tang, Dale D

    2013-07-12

    Actin filament polymerization plays a critical role in the regulation of smooth muscle contraction. However, our knowledge regarding modulation of the actin cytoskeleton in smooth muscle just begins to accumulate. In this study, stimulation with acetylcholine (ACh) induced an increase in the association of the adapter protein c-Abl interactor 1 (Abi1) with neuronal Wiskott-Aldrich syndrome protein (N-WASP) (an actin-regulatory protein) in smooth muscle cells/tissues. Furthermore, contractile stimulation activated N-WASP in live smooth muscle cells as evidenced by changes in fluorescence resonance energy transfer efficiency of an N-WASP sensor. Abi1 knockdown by lentivirus-mediated RNAi inhibited N-WASP activation, actin polymerization, and contraction in smooth muscle. However, Abi1 silencing did not affect myosin regulatory light chain phosphorylation at Ser-19 in smooth muscle. In addition, c-Abl tyrosine kinase and Crk-associated substrate (CAS) have been shown to regulate smooth muscle contraction. The interaction of Abi1 with c-Abl and CAS has not been investigated. Here, contractile activation induced formation of a multiprotein complex including c-Abl, CAS, and Abi1. Knockdown of c-Abl and CAS attenuated the activation of Abi1 during contractile activation. More importantly, Abi1 knockdown inhibited c-Abl phosphorylation at Tyr-412 and the interaction of c-Abl with CAS. These results suggest that Abi1 is an important component of the cellular process that regulates N-WASP activation, actin dynamics, and contraction in smooth muscle. Abi1 is activated by the c-Abl-CAS pathway, and Abi1 reciprocally controls the activation of its upstream regulator c-Abl.

  10. Role of the Adapter Protein Abi1 in Actin-associated Signaling and Smooth Muscle Contraction*

    PubMed Central

    Wang, Tao; Cleary, Rachel A.; Wang, Ruping; Tang, Dale D.

    2013-01-01

    Actin filament polymerization plays a critical role in the regulation of smooth muscle contraction. However, our knowledge regarding modulation of the actin cytoskeleton in smooth muscle just begins to accumulate. In this study, stimulation with acetylcholine (ACh) induced an increase in the association of the adapter protein c-Abl interactor 1 (Abi1) with neuronal Wiskott-Aldrich syndrome protein (N-WASP) (an actin-regulatory protein) in smooth muscle cells/tissues. Furthermore, contractile stimulation activated N-WASP in live smooth muscle cells as evidenced by changes in fluorescence resonance energy transfer efficiency of an N-WASP sensor. Abi1 knockdown by lentivirus-mediated RNAi inhibited N-WASP activation, actin polymerization, and contraction in smooth muscle. However, Abi1 silencing did not affect myosin regulatory light chain phosphorylation at Ser-19 in smooth muscle. In addition, c-Abl tyrosine kinase and Crk-associated substrate (CAS) have been shown to regulate smooth muscle contraction. The interaction of Abi1 with c-Abl and CAS has not been investigated. Here, contractile activation induced formation of a multiprotein complex including c-Abl, CAS, and Abi1. Knockdown of c-Abl and CAS attenuated the activation of Abi1 during contractile activation. More importantly, Abi1 knockdown inhibited c-Abl phosphorylation at Tyr-412 and the interaction of c-Abl with CAS. These results suggest that Abi1 is an important component of the cellular process that regulates N-WASP activation, actin dynamics, and contraction in smooth muscle. Abi1 is activated by the c-Abl-CAS pathway, and Abi1 reciprocally controls the activation of its upstream regulator c-Abl. PMID:23740246

  11. Yuji Tonomura: a pioneer in the field of energy transduction in muscle contraction.

    PubMed

    Onishi, Hirofumi

    2009-07-01

    Late Professor Yuji Tonomura has made a great contribution in the study of energy transduction in muscle contraction. He was the investigator who first proposed that a myosin-phosphate intermediate is produced subsequently to the Michaelis-Menten complex in the pre-steady state of the myosin ATPase reaction and that it is a key intermediate for muscle contraction. Here, his proposed intermediate will be viewed from the prospective of today's understanding of actomyosin ATPase kinetics and in the context of myosin motor domain crystal structures.

  12. Intra-abdominal pedicled rectus abdominis muscle flap for treatment of high-output enterocutaneous fistulae: case reports and review of literature.

    PubMed

    Carey, Joseph N; Sheckter, Clifford C; Watt, Andrew J; Lee, Gordon K

    2013-08-01

    Despite advances in nutritional supplementation, sepsis management, percutaneous drainage and surgical technique, enterocutaneous fistulae remain a considerable source of morbidity and mortality. Use of adjunctive modalities including negative pressure wound therapy and fibrin glue have been shown to improve the rapidity of fistula closure; however, the overall rate of closure remains poor. The challenge of managing chronic, high-output proximal enterocutaneous fistulae can be successfully achieved with appropriate medical management and intra-abdominal placement of pedicled rectus abdominis muscle flaps. We report two cases of recalcitrant high output enterocutaneous fistulae that were treated successfully with pedicled intra-abdominal rectus muscle flaps. Indications for pedicled intra-abdominal rectus muscle flaps include persistent patency despite a reasonable trial of non-operative intervention, failure of traditional operative interventions (serosal patch, Graham patch), and persistent electrolyte and nutritional abnormalities in the setting of a high-output fistula. Copyright © 2013 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.

  13. Capillary response to skeletal muscle contraction: evidence that redundancy between vasodilators is physiologically relevant during active hyperaemia.

    PubMed

    Lamb, Iain R; Novielli, Nicole M; Murrant, Coral L

    2018-04-15

    The current theory behind matching blood flow to metabolic demand of skeletal muscle suggests redundant interactions between metabolic vasodilators. Capillaries play an important role in blood flow control given their ability to respond to muscle contraction by causing conducted vasodilatation in upstream arterioles that control their perfusion. We sought to determine whether redundancies occur between vasodilators at the level of the capillary by stimulating the capillaries with muscle contraction and vasodilators relevant to muscle contraction. We identified redundancies between potassium and both adenosine and nitric oxide, between nitric oxide and potassium, and between adenosine and both potassium and nitric oxide. During muscle contraction, we demonstrate redundancies between potassium and nitric oxide as well as between potassium and adenosine. Our data show that redundancy is physiologically relevant and involved in the coordination of the vasodilator response during muscle contraction at the level of the capillaries. We sought to determine if redundancy between vasodilators is physiologically relevant during active hyperaemia. As inhibitory interactions between vasodilators are indicative of redundancy, we tested whether vasodilators implicated in mediating active hyperaemia (potassium (K + ), adenosine (ADO) and nitric oxide (NO)) inhibit one another's vasodilatory effects through direct application of pharmacological agents and during muscle contraction. Using the hamster cremaster muscle and intravital microscopy, we locally stimulated capillaries with one vasodilator in the absence and the presence of a second vasodilator (10 -7 m S-nitroso-N-acetylpenicillamine (SNAP), 10 -7 m ADO, 10 mm KCl) applied sequentially and simultaneously, and observed the response in the associated upstream 4A arteriole controlling the perfusion of the stimulated capillary. We found that KCl significantly attenuated SNAP- and ADO-induced vasodilatations by ∼49.7% and

  14. Classical and adaptive control of ex vivo skeletal muscle contractions using Functional Electrical Stimulation (FES)

    PubMed Central

    Shoemaker, Adam; Grange, Robert W.; Abaid, Nicole; Leonessa, Alexander

    2017-01-01

    Functional Electrical Stimulation is a promising approach to treat patients by stimulating the peripheral nerves and their corresponding motor neurons using electrical current. This technique helps maintain muscle mass and promote blood flow in the absence of a functioning nervous system. The goal of this work is to control muscle contractions from FES via three different algorithms and assess the most appropriate controller providing effective stimulation of the muscle. An open-loop system and a closed-loop system with three types of model-free feedback controllers were assessed for tracking control of skeletal muscle contractions: a Proportional-Integral (PI) controller, a Model Reference Adaptive Control algorithm, and an Adaptive Augmented PI system. Furthermore, a mathematical model of a muscle-mass-spring system was implemented in simulation to test the open-loop case and closed-loop controllers. These simulations were carried out and then validated through experiments ex vivo. The experiments included muscle contractions following four distinct trajectories: a step, sine, ramp, and square wave. Overall, the closed-loop controllers followed the stimulation trajectories set for all the simulated and tested muscles. When comparing the experimental outcomes of each controller, we concluded that the Adaptive Augmented PI algorithm provided the best closed-loop performance for speed of convergence and disturbance rejection. PMID:28273101

  15. Trunk muscle activity increases with unstable squat movements.

    PubMed

    Anderson, Kenneth; Behm, David G

    2005-02-01

    The objective of this study was to determine differences in electromyographic (EMG) activity of the soleus (SOL), vastus lateralis (VL), biceps femoris (BF), abdominal stabilizers (AS), upper lumbar erector spinae (ULES), and lumbo-sacral erector spinae (LSES) muscles while performing squats of varied stability and resistance. Stability was altered by doing the squat movement on a Smith machine, a free squat, and while standing on two balance discs. Fourteen male subjects performed the movements. Activities of the SOL, AS, ULES, and LSES were highest during the unstable squat and lowest with the Smith machine protocol (p < 0.05). Increased EMG activity of these muscles may be attributed to their postural and stabilization role. Furthermore, EMG activity was higher during concentric contractions compared to eccentric contractions. Performing squats on unstable surfaces may permit a training adaptation of the trunk muscles responsible for supporting the spinal column (i.e., erector spinae) as well as the muscles most responsible for maintaining posture (i.e., SOL).

  16. Potassium Channels in Regulation of Vascular Smooth Muscle Contraction and Growth

    PubMed Central

    Jackson, William F.

    2017-01-01

    Potassium channels importantly contribute to the regulation of vascular smooth muscle (VSM) contraction and growth. They are the dominant ion conductance of the VSM cell membrane and importantly determine and regulate membrane potential. Membrane potential, in turn, regulates the open-state probability of voltage-gated Ca2+ channels (VGCC), Ca2+ influx through VGCC, intracellular Ca2+ and VSM contraction. Membrane potential also affects release of Ca2+ from internal stores and the Ca2+ sensitivity of the contractile machinery such that K+ channels participate in all aspects of regulation of VSM contraction. Potassium channels also regulate proliferation of VSM cells through membrane potential-dependent and membrane potential-independent mechanisms. Vascular smooth muscle cells express multiple isoforms of at least five classes of K+ channels contribute to the regulation of contraction and cell proliferation (growth). This review will examine the structure, expression and function of large-conductance, Ca2+-activated K+ (BKCa) channels, intermediate-conductance Ca2+-activated K+ (KCa3.1) channels, multiple isoforms of voltage-gated K+ (KV) channels, ATP-sensitive K+ (KATP) channels, and inward-rectifier K+ (KIR) channels in both contractile and proliferating VSM cells. PMID:28212804

  17. Wet needling of myofascial trigger points in abdominal muscles for treatment of primary dysmenorrhoea.

    PubMed

    Huang, Qiang-Min; Liu, Lin

    2014-08-01

    To evaluate the effect of wet needling (related to acupuncture) and home stretching exercises on myofascial trigger points (MTrPs) in abdominal muscles for the treatment of dysmenorrhoea. The effect of wet needing of MTrPs in abdominal muscles, supplemented by home stretching exercises, was observed in 65 patients with moderate and severe primary dysmenorrhoea. The MTrPs in the abdominal region were localised and repeatedly needled with lidocaine injection. Menstrual pain was evaluated with a Visual Analogue Scale (VAS) score after every treatment, with the final evaluation made at a 1-year follow-up. Treatment was stopped when the VAS pain score reduced to ≤3. Symptoms scores were analysed with one-way analysis of variance. The mean VAS pain score before treatment was 7.49±1.16. After a single wet needling session, 41 patients had a reduction in their VAS pain score to <3 during their following menstrual cycle, with a mean of 1.63±0.49. Twenty-four patients who needed two treatments showed a reduction in menstrual pain scores to 0.58±0.50. After 1 year, the mean VAS pain score among all patients was 0.28±0.45, with a response rate of 100%. Primary dysmenorrhoea was significantly reduced 1 year after wet needling to MTrPs in the abdominal region and home stretching exercises, justifying further research with controlled trials. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

  18. Muscle contraction phenotypic analysis enabled by optogenetics reveals functional relationships of sarcomere components in Caenorhabditis elegans.

    PubMed

    Hwang, Hyundoo; Barnes, Dawn E; Matsunaga, Yohei; Benian, Guy M; Ono, Shoichiro; Lu, Hang

    2016-01-29

    The sarcomere, the fundamental unit of muscle contraction, is a highly-ordered complex of hundreds of proteins. Despite decades of genetics work, the functional relationships and the roles of those sarcomeric proteins in animal behaviors remain unclear. In this paper, we demonstrate that optogenetic activation of the motor neurons that induce muscle contraction can facilitate quantitative studies of muscle kinetics in C. elegans. To increase the throughput of the study, we trapped multiple worms in parallel in a microfluidic device and illuminated for photoactivation of channelrhodopsin-2 to induce contractions in body wall muscles. Using image processing, the change in body size was quantified over time. A total of five parameters including rate constants for contraction and relaxation were extracted from the optogenetic assay as descriptors of sarcomere functions. To potentially relate the genes encoding the sarcomeric proteins functionally, a hierarchical clustering analysis was conducted on the basis of those parameters. Because it assesses physiological output different from conventional assays, this method provides a complement to the phenotypic analysis of C. elegans muscle mutants currently performed in many labs; the clusters may provide new insights and drive new hypotheses for functional relationships among the many sarcomere components.

  19. Muscle contraction phenotypic analysis enabled by optogenetics reveals functional relationships of sarcomere components in Caenorhabditis elegans

    NASA Astrophysics Data System (ADS)

    Hwang, Hyundoo; Barnes, Dawn E.; Matsunaga, Yohei; Benian, Guy M.; Ono, Shoichiro; Lu, Hang

    2016-01-01

    The sarcomere, the fundamental unit of muscle contraction, is a highly-ordered complex of hundreds of proteins. Despite decades of genetics work, the functional relationships and the roles of those sarcomeric proteins in animal behaviors remain unclear. In this paper, we demonstrate that optogenetic activation of the motor neurons that induce muscle contraction can facilitate quantitative studies of muscle kinetics in C. elegans. To increase the throughput of the study, we trapped multiple worms in parallel in a microfluidic device and illuminated for photoactivation of channelrhodopsin-2 to induce contractions in body wall muscles. Using image processing, the change in body size was quantified over time. A total of five parameters including rate constants for contraction and relaxation were extracted from the optogenetic assay as descriptors of sarcomere functions. To potentially relate the genes encoding the sarcomeric proteins functionally, a hierarchical clustering analysis was conducted on the basis of those parameters. Because it assesses physiological output different from conventional assays, this method provides a complement to the phenotypic analysis of C. elegans muscle mutants currently performed in many labs; the clusters may provide new insights and drive new hypotheses for functional relationships among the many sarcomere components.

  20. Involvement of the Tyr kinase/JNK pathway in carbachol-induced bronchial smooth muscle contraction in the rat.

    PubMed

    Sakai, Hiroyasu; Watanabe, Yu; Honda, Mai; Tsuiki, Rika; Ueda, Yusuke; Nagai, Yuki; Narita, Minoru; Misawa, Miwa; Chiba, Yoshihiko

    2013-05-01

    Tyrosine (Tyr) kinases and mitogen-activated protein kinases have been thought to participate in the contractile response in various smooth muscles. The aim of the current study was to investigate the involvement of the Tyr kinase pathway in the contraction of bronchial smooth muscle. Ring preparations of bronchi isolated from rats were suspended in an organ bath. Isometric contraction of circular smooth muscle was measured. Immunoblotting was used to examine the phosphorylation of c-Jun N-terminal kinasess (JNKs) in bronchial smooth muscle. To examine the role of mitogen-activated protein kinase(s) in bronchial smooth muscle contraction, the effects of MPAK inhibitors were investigated in this study. The contraction induced by carbachol (CCh) was significantly inhibited by pretreatment with selective Tyr kinase inhibitors (genistein and ST638, n = 6, respectively), and a JNK inhibitor (SP600125, n = 6). The contractions induced by high K depolarization (n = 4), orthovanadate (a potent Tyr phosphatase inhibitor) and sodium fluoride (a G protein activator; NaF) were also significantly inhibited by selective Tyr kinase inhibitors and a JNK inhibitor (n = 4, respectively). However, the contraction induced by calyculin-A was not affected by SP600125. On the other hand, JNKs were phosphorylated by CCh (2.2 ± 0,4 [mean±SEM] fold increase). The JNK phosphorylation induced by CCh was significantly inhibited by SP600125 (n = 4). These findings suggest that the Tyr kinase/JNK pathway may play a role in bronchial smooth muscle contraction. Strategies to inhibit JNK activation may represent a novel therapeutic approach for diseases involving airway obstruction, such as asthma and chronic obstructive pulmonary disease.

  1. Contraction-induced injury to single permeabilized muscle fibers from normal and congenitally-clefted goat palates.

    PubMed

    Rader, Erik P; Cederna, Paul S; Weinzweig, Jeffrey; Panter, Kip E; Yu, Deborah; Buchman, Steven R; Larkin, Lisa M; Faulkner, John A

    2007-03-01

    Levator veli palatini muscles from normal palates of adult humans and goats are predominantly slow oxidative (type 1) fibers. However, 85% of levator veli palatini fibers from cleft palates of adult goats are physiologically fast (type 2). This fiber composition difference between cleft and normal palates may have implications in palatal function. For limb muscles, type 2 muscle fibers are more susceptible to lengthening contraction-induced injury than are type 1 fibers. We tested the hypothesis that, compared with single permeabilized levator veli palatini muscle fibers from normal palates of adult goats, those from cleft palates are more susceptible to lengthening contraction-induced injury. Congenital cleft palates were the result of chemically-induced decreased movement of the fetal head and tongue causing obstruction of palatal closure. Each muscle fiber was maximally activated and lengthened. Fiber type was determined by contractile properties and gel electrophoresis. Susceptibility to injury was assessed by measuring the decrease in maximum force following the lengthening contraction, expressed as a percentage of the initial force. Compared with fibers from normal palates that were all type 1 and had force deficits of 23 +/- 1%, fibers from cleft palates were all type 2 and sustained twofold greater deficits, 40 +/- 1% (p = .001). Levator veli palatini muscles from cleft palates of goats contain predominantly type 2 fibers that are highly susceptible to lengthening contraction-induced injury. This finding may have implications regarding palatal function and the incidence of velopharyngeal incompetence.

  2. Impact of cell-free hemoglobin on contracting skeletal muscle microvascular oxygen pressure dynamics.

    PubMed

    Ferguson, Scott K; Harral, Julie W; Pak, David I; Redinius, Katherine M; Stenmark, Kurt R; Schaer, Dominik J; Buehler, Paul W; Irwin, David C

    2018-06-01

    Free hemoglobin (Hb) associated with hemolysis extravasates into vascular tissue and depletes nitric oxide (NO), which leads to impaired vascular function and could impair skeletal muscle metabolic control during exercise. We tested the hypothesis that: 1) free Hb would extravasate into skeletal muscle tissue, reducing the contracting skeletal muscle O 2 delivery/O 2 utilization ratio (microvascular PO 2 , PO 2 mv) to a similar extent as that observed following NO synthase (NOS) blockade, and 2) that the Hb scavenging protein haptoglobin (Hp) would prevent Hb extravasation and inhibit these skeletal muscle tissue effects. PO 2 mv was measured in eight rats (phosphorescence quenching) at rest and during 180 s of electrically induced (1-Hz) twitch spinotrapezius muscle contractions (experiment 1). A second group of seven rats was also used to investigate the effects of Hb + Hp (experiment 2). For both experiments, measurements were made: 1) during control conditions, 2) following a bolus infusion of either Hb (50 mg/kg) or Hb + Hp (50 mg/kg), and 3) following local superfusion of NG-nitro-l-arginine methyl ester (L-NAME; 10 mg/kg). Additional experiments were completed to visualize Hb extravasation into the muscular tissue using Click chemistry techniques. There were no significant differences in the PO 2 mv observed at rest for any condition in either experiment (p > 0.05 for all). In experiment 1, both Hb and L-NAME reduced the PO 2 mv significantly during the steady-state of muscle contractions when compared to control conditions with no differences between Hb and L-NAME (control: 24 ± 1, Hb: 21 ± 1, L-NAME: 20 ± 1 mmHg, p < 0.05). In experiment 2, only L-NAME resulted in a significantly lower PO 2 mv during the steady-state of muscle contractions (control: 25 ± 1, Hb + Hp: 22 ± 2, L-NAME: 18 ± 1 mmHg, p < 0.05). Free Hb lowered the blood-myocyte O 2 driving force to a level not significantly different from L

  3. Age-related differences in muscle fatigue vary by contraction type: a meta-analysis.

    PubMed

    Avin, Keith G; Law, Laura A Frey

    2011-08-01

    During senescence, despite the loss of strength (force-generating capability) associated with sarcopenia, muscle endurance may improve for isometric contractions. The purpose of this study was to perform a systematic meta-analysis of young versus older adults, considering likely moderators (ie, contraction type, joint, sex, activity level, and task intensity). A 2-stage systematic review identified potential studies from PubMed, CINAHL, PEDro, EBSCOhost: ERIC, EBSCOhost: Sportdiscus, and The Cochrane Library. Studies reporting fatigue tasks (voluntary activation) performed at a relative intensity in both young (18-45 years of age) and old (≥ 55 years of age) adults who were healthy were considered. Sample size, mean and variance outcome data (ie, fatigue index or endurance time), joint, contraction type, task intensity (percentage of maximum), sex, and activity levels were extracted. Effect sizes were (1) computed for all data points; (2) subgrouped by contraction type, sex, joint or muscle group, intensity, or activity level; and (3) further subgrouped between contraction type and the remaining moderators. Out of 3,457 potential studies, 46 publications (with 78 distinct effect size data points) met all inclusion criteria. A lack of available data limited subgroup analyses (ie, sex, intensity, joint), as did a disproportionate spread of data (most intensities ≥ 50% of maximum voluntary contraction). Overall, older adults were able to sustain relative-intensity tasks significantly longer or with less force decay than younger adults (effect size=0.49). However, this age-related difference was present only for sustained and intermittent isometric contractions, whereas this age-related advantage was lost for dynamic tasks. When controlling for contraction type, the additional modifiers played minor roles. Identifying muscle endurance capabilities in the older adult may provide an avenue to improve functional capabilities, despite a clearly established decrement in

  4. Age-Related Differences in Muscle Fatigue Vary by Contraction Type: A Meta-analysis

    PubMed Central

    Avin, Keith G.

    2011-01-01

    Background During senescence, despite the loss of strength (force-generating capability) associated with sarcopenia, muscle endurance may improve for isometric contractions. Purpose The purpose of this study was to perform a systematic meta-analysis of young versus older adults, considering likely moderators (ie, contraction type, joint, sex, activity level, and task intensity). Data Sources A 2-stage systematic review identified potential studies from PubMed, CINAHL, PEDro, EBSCOhost: ERIC, EBSCOhost: Sportdiscus, and The Cochrane Library. Study Selection Studies reporting fatigue tasks (voluntary activation) performed at a relative intensity in both young (18–45 years of age) and old (≥55 years of age) adults who were healthy were considered. Data Extraction Sample size, mean and variance outcome data (ie, fatigue index or endurance time), joint, contraction type, task intensity (percentage of maximum), sex, and activity levels were extracted. Data Synthesis Effect sizes were (1) computed for all data points; (2) subgrouped by contraction type, sex, joint or muscle group, intensity, or activity level; and (3) further subgrouped between contraction type and the remaining moderators. Out of 3,457 potential studies, 46 publications (with 78 distinct effect size data points) met all inclusion criteria. Limitations A lack of available data limited subgroup analyses (ie, sex, intensity, joint), as did a disproportionate spread of data (most intensities ≥50% of maximum voluntary contraction). Conclusions Overall, older adults were able to sustain relative-intensity tasks significantly longer or with less force decay than younger adults (effect size=0.49). However, this age-related difference was present only for sustained and intermittent isometric contractions, whereas this age-related advantage was lost for dynamic tasks. When controlling for contraction type, the additional modifiers played minor roles. Identifying muscle endurance capabilities in the older

  5. Contraction dynamics and function of the muscle-tendon complex depend on the muscle fibre-tendon length ratio: a simulation study.

    PubMed

    Mörl, Falk; Siebert, Tobias; Häufle, Daniel

    2016-02-01

    Experimental studies show different muscle-tendon complex (MTC) functions (e.g. motor or spring) depending on the muscle fibre-tendon length ratio. Comparing different MTC of different animals examined experimentally, the extracted MTC functions are biased by, for example, MTC-specific pennation angle and fibre-type distribution or divergent experimental protocols (e.g. influence of temperature or stimulation on MTC force). Thus, a thorough understanding of variation of these inner muscle fibre-tendon length ratios on MTC function is difficult. In this study, we used a hill-type muscle model to simulate MTC. The model consists of a contractile element (CE) simulating muscle fibres, a serial element (SE) as a model for tendon, and a parallel elastic element (PEE) modelling tissue in parallel to the muscle fibres. The simulation examines the impact of length variations of these components on contraction dynamics and MTC function. Ensuring a constant overall length of the MTC by L(MTC) = L(SE) + L(CE), the SE rest length was varied over a broad physiological range from 0.1 to 0.9 MTC length. Five different MTC functions were investigated by simulating typical physiological experiments: the stabilising function with isometric contractions, the motor function with contractions against a weight, the capability of acceleration with contractions against a small inertial mass, the braking function by decelerating a mass, and the spring function with stretch-shortening cycles. The ratio of SE and CE mainly determines the MTC function. MTC with comparably short tendon generates high force and maximal shortening velocity and is able to produce maximal work and power. MTC with long tendon is suitable to store and release a maximum amount of energy. Variation of muscle fibre-tendon ratio yielded two peaks for MTC's force response for short and long SE lengths. Further, maximum work storage capacity of the SE is at long relL(SE,0). Impact of fibre-tendon length ratio on MTC

  6. Muscle Fatigue Affects the Interpolated Twitch Technique When Assessed Using Electrically-Induced Contractions in Human and Rat Muscles.

    PubMed

    Neyroud, Daria; Cheng, Arthur J; Bourdillon, Nicolas; Kayser, Bengt; Place, Nicolas; Westerblad, Håkan

    2016-01-01

    The interpolated twitch technique (ITT) is the gold standard to assess voluntary activation and central fatigue. Yet, its validity has been questioned. Here we studied how peripheral fatigue can affect the ITT. Repeated contractions at submaximal frequencies were produced by supramaximal electrical stimulations of the human adductor pollicis muscle in vivo and of isolated rat soleus fiber bundles; an extra stimulation pulse was given during contractions to induce a superimposed twitch. Human muscles fatigued by repeated 30-Hz stimulation trains (3 s on-1 s off) showed an ~80% reduction in the superimposed twitch force accompanied by a severely reduced EMG response (M-wave amplitude), which implies action potential failure. Subsequent experiments combined a less intense stimulation protocol (1.5 s on-3 s off) with ischemia to cause muscle fatigue, but which preserved M-wave amplitude. However, the superimposed twitch force still decreased markedly more than the potentiated twitch force; with ITT this would reflect increased "voluntary activation." In contrast, the superimposed twitch force was relatively spared when a similar protocol was performed in rat soleus bundles. Force relaxation was slowed by >150% in fatigued human muscles, whereas it was unchanged in rat soleus bundles. Accordingly, results similar to those in the human muscle were obtained when relaxation was slowed by cooling the rat soleus muscles. In conclusion, our data demonstrate that muscle fatigue can confound the quantification of central fatigue using the ITT.

  7. Muscle activity during leg strengthening exercise using free weights and elastic resistance: effects of ballistic vs controlled contractions.

    PubMed

    Jakobsen, Markus Due; Sundstrup, Emil; Andersen, Christoffer H; Aagaard, Per; Andersen, Lars L

    2013-02-01

    The present study's aim was to evaluate muscle activity during leg exercises using elastic vs. isoinertial resistance at different exertion and loading levels, respectively. Twenty-four women and eighteen men aged 26-67 years volunteered to participate in the experiment. Electromyographic (EMG) activity was recorded in nine muscles during a standardized forward lunge movement performed with dumbbells and elastic bands during (1) ballistic vs. controlled exertion, and (2) at low, medium and high loads (33%, 66% and 100% of 10 RM, respectively). The recorded EMG signals were normalized to MVC EMG. Knee joint angle was measured using electronic inclinometers. The following results were obtained. Loading intensity affected EMG amplitude in the order: lowcontractions always produced greater EMG activity than slow controlled contractions, and for most muscles ballistic contractions with medium load showed similar EMG amplitude as controlled contractions with high load. At flexed knee joint positions with elastic resistance, quadriceps and gluteus EMG amplitude during medium-load ballistic contractions exceeded that recorded during high-load controlled contractions. Quadriceps and gluteus EMG amplitude increased at flexed knee positions. In contrast, hamstrings EMG amplitude remained constant throughout ROM during dumbbell lunge, but increased at more extended knee joint positions during lunges using elastic resistance. Based on these results, it can be concluded that lunges performed using medium-load ballistic muscle contractions may induce similar or even higher leg muscle activity than lunges using high-load slow-speed contractions. Consequently, lunges using elastic resistance appear to be equally effective in inducing high leg muscle activity as traditional lunges using isoinertial resistance. Copyright © 2012 Elsevier B.V. All rights reserved.

  8. Age-dependent contribution of Rho kinase in carbachol-induced contraction of human detrusor smooth muscle in vitro

    PubMed Central

    Kirschstein, Timo; Protzel, Chris; Porath, Katrin; Sellmann, Tina; Köhling, Rüdiger; Hakenberg, Oliver W

    2014-01-01

    Aim: Activation of muscarinic receptors on the detrusor smooth muscle is followed by contraction, which involves both myosin light chain kinase (MLCK) and Rho kinase (ROCK). The aim of this study was to determine the relative contributions of MLCK and ROCK to carbachol-induced contraction of human detrusor smooth muscle in vitro. Methods: Detrusor smooth muscle strips were prepared from the macroscopically unaffected bladder wall of patients underwent cystectomy. The strips were fixed in an organ bath, and carbachol or KCl-induced isometric contractions were measured by force transducers. Results: Addition of carbachol (0.4-4 μmol/L) into the bath induced concentration-dependent contractions of detrusor specimens, which was completely abolished by atropine (1 μmol/L). Pre-incubation of detrusor specimens with either the MLCK inhibitor ML-9 or the ROCK inhibitors HA1100 and Y-27632 (each at 10 μmol/L) significantly blocked carbachol-induced contractions as compared to the time-control experiments. Moreover, MLCK and ROCK inhibition were equally effective in reducing carbachol-induced contractions. The residual carbachol-induced contractions in the presence of both MLCK and ROCK inhibitors were significantly smaller than the contractions obtained when only one enzyme (either MLCK or ROCK) was inhibited, suggesting an additive effect of the two kinases. Interestingly, ROCK-mediated carbachol-induced contractions were positively correlated to the age of patients (r=o.52, P<0.05). Conclusion: Both MLCK and ROCK contribute to carbachol-induced contractions of human detrusor smooth muscle. ROCK inhibitors may be a new pharmacological approach to modulate human bladder hyperactivity. PMID:24122009

  9. Age-dependent contribution of Rho kinase in carbachol-induced contraction of human detrusor smooth muscle in vitro.

    PubMed

    Kirschstein, Timo; Protzel, Chris; Porath, Katrin; Sellmann, Tina; Köhling, Rüdiger; Hakenberg, Oliver W

    2014-01-01

    Activation of muscarinic receptors on the detrusor smooth muscle is followed by contraction, which involves both myosin light chain kinase (MLCK) and Rho kinase (ROCK). The aim of this study was to determine the relative contributions of MLCK and ROCK to carbachol-induced contraction of human detrusor smooth muscle in vitro. Detrusor smooth muscle strips were prepared from the macroscopically unaffected bladder wall of patients underwent cystectomy. The strips were fixed in an organ bath, and carbachol or KCl-induced isometric contractions were measured by force transducers. Addition of carbachol (0.4-4 μmol/L) into the bath induced concentration-dependent contractions of detrusor specimens, which was completely abolished by atropine (1 μmol/L). Pre-incubation of detrusor specimens with either the MLCK inhibitor ML-9 or the ROCK inhibitors HA1100 and Y-27632 (each at 10 μmol/L) significantly blocked carbachol-induced contractions as compared to the time-control experiments. Moreover, MLCK and ROCK inhibition were equally effective in reducing carbachol-induced contractions. The residual carbachol-induced contractions in the presence of both MLCK and ROCK inhibitors were significantly smaller than the contractions obtained when only one enzyme (either MLCK or ROCK) was inhibited, suggesting an additive effect of the two kinases. Interestingly, ROCK-mediated carbachol-induced contractions were positively correlated to the age of patients (r=o.52, P<0.05). Both MLCK and ROCK contribute to carbachol-induced contractions of human detrusor smooth muscle. ROCK inhibitors may be a new pharmacological approach to modulate human bladder hyperactivity.

  10. Reversal of asynchrony between circular and longitudinal muscle contraction in nutcracker esophagus by atropine.

    PubMed

    Korsapati, Hariprasad; Bhargava, Valmik; Mittal, Ravinder K

    2008-09-01

    Patients with high-amplitude esophageal contractions (nutcracker esophagus [NCE]) show asynchrony of circular muscle (CM) and longitudinal muscle (LM) contraction during peristalsis. The goal of our study was to determine if this asynchrony is related to an increase in the cholinergic receptor activity. High-frequency intraluminal ultrasound images and pressures of the esophagus were recorded simultaneously in 10 normal subjects and 10 patients with NCE. Recordings were obtained at 2 cm above the lower esophageal sphincter under 2 study conditions in normal subjects (before and after 80 microgm/kg of edrophonium), and under 3 study conditions in the NCE patients (control, 5 microgm and 10 microgm/kg of atropine). In normal subjects, edrophonium induced an increase in the CM and LM contraction amplitude, an increase in the contraction duration, and asynchrony of LM and CM contraction during peristalsis. On the other hand, increased contraction amplitude, duration, and asynchrony of LM and CM contraction observed at the baseline in the NCE patients were reversed by atropine in a dose-dependent fashion. These data prove that the esophageal motor abnormalities in patients with nutcracker esophagus, including asynchrony of CM and LM contraction, are related to a hypercholinergic state.

  11. EMG-force relationship during static contraction: Effects on sensor placement locations on biceps brachii muscle.

    PubMed

    Ahamed, Nizam Uddin; Sundaraj, Kenneth; Alqahtani, Mahdi; Altwijri, Omar; Ali, Md Asraf; Islam, Md Anamul

    2014-10-15

    The relationship between surface electromyography (EMG) and force have been the subject of ongoing investigations and remain a subject of controversy. Even under static conditions, the relationships at different sensor placement locations in the biceps brachii (BB) muscle are complex. The aim of this study was to compare the activity and relationship between surface EMG and static force from the BB muscle in terms of three sensor placement locations. Twenty-one right hand dominant male subjects (age 25.3 ± 1.2 years) participated in the study. Surface EMG signals were detected from the subject's right BB muscle. The muscle activation during force was determined as the root mean square (RMS) electromyographic signal normalized to the peak RMS EMG signal of isometric contraction for 10 s. The statistical analysis included linear regression to examine the relationship between EMG amplitude and force of contraction [40-100% of maximal voluntary contraction (MVC)], repeated measures ANOVA to assess differences among the sensor placement locations, and coefficient of variation (CoV) for muscle activity variation. The results demonstrated that when the sensor was placed on the muscle belly, the linear slope coefficient was significantly greater for EMG versus force testing (r^{2} = 0.61, P > 0.05) than when placed on the lower part (r^{2}=0.31, P< 0.05) and upper part of the muscle belly (r^{2}=0.29, P > 0.05). In addition, the EMG signal activity on the muscle belly had less variability than the upper and lower parts (8.55% vs. 15.12% and 12.86%, respectively). These findings indicate the importance of applying the surface EMG sensor at the appropriate locations that follow muscle fiber orientation of the BB muscle during static contraction. As a result, EMG signals of three different placements may help to understand the difference in the amplitude of the signals due to placement.

  12. Noninvasive observation of skeletal muscle contraction using near-infrared time-resolved reflectance and diffusing-wave spectroscopy

    NASA Astrophysics Data System (ADS)

    Belau, Markus; Ninck, Markus; Hering, Gernot; Spinelli, Lorenzo; Contini, Davide; Torricelli, Alessandro; Gisler, Thomas

    2010-09-01

    We introduce a method for noninvasively measuring muscle contraction in vivo, based on near-infrared diffusing-wave spectroscopy (DWS). The method exploits the information about time-dependent shear motions within the contracting muscle that are contained in the temporal autocorrelation function g(1)(τ,t) of the multiply scattered light field measured as a function of lag time, τ, and time after stimulus, t. The analysis of g(1)(τ,t) measured on the human M. biceps brachii during repetitive electrical stimulation, using optical properties measured with time-resolved reflectance spectroscopy, shows that the tissue dynamics giving rise to the speckle fluctuations can be described by a combination of diffusion and shearing. The evolution of the tissue Cauchy strain e(t) shows a strong correlation with the force, indicating that a significant part of the shear observed with DWS is due to muscle contraction. The evolution of the DWS decay time shows quantitative differences between the M. biceps brachii and the M. gastrocnemius, suggesting that DWS allows to discriminate contraction of fast- and slow-twitch muscle fibers.

  13. A model of muscle contraction based on the Langevin equation with actomyosin potentials.

    PubMed

    Tamura, Youjiro; Ito, Akira; Saito, Masami

    2017-02-01

    We propose a muscle contraction model that is essentially a model of the motion of myosin motors as described by a Langevin equation. This model involves one-dimensional numerical calculations wherein the total force is the sum of a viscous force proportional to the myosin head velocity, a white Gaussian noise produced by random forces and other potential forces originating from the actomyosin structure and intra-molecular charges. We calculate the velocity of a single myosin on an actin filament to be 4.9-49 μm/s, depending on the viscosity between the actomyosin molecules. A myosin filament with a hundred myosin heads is used to simulate the contractions of a half-sarcomere within the skeletal muscle. The force response due to a quick release in the isometric contraction is simulated using a process wherein crossbridges are changed forcibly from one state to another. In contrast, the force response to a quick stretch is simulated using purely mechanical characteristics. We simulate the force-velocity relation and energy efficiency in the isotonic contraction and adenosine triphosphate consumption. The simulation results are in good agreement with the experimental results. We show that the Langevin equation for the actomyosin potentials can be modified statistically to become an existing muscle model that uses Maxwell elements.

  14. Heart rate at the onset of muscle contraction and during passive muscle stretch in humans: a role for mechanoreceptors

    PubMed Central

    Gladwell, V F; Coote, J H

    2002-01-01

    Previous evidence suggests that the heart rate (HR) increase observed with isometric exercise is dependent on different afferent mechanisms to those eliciting the increase in blood pressure (BP). Central command and muscle metaboreceptors have been shown to contribute to this differential effect. However, in experimental animals passive stretch of the hindlimb increases HR suggesting that small fibre mechanoreceptors could also have a role. This has not been previously shown in humans and was investigated in this study. Healthy human volunteers were instrumented to record BP, ECG, respiration, EMG of rectus femoris and gastrocnemius and contraction force of triceps surae. Voluntary isometric contraction of triceps surae elicited a significant HR change in the first three respiratory cycles at 40 % of maximum voluntary contraction whereas BP did not change significantly until after 30 s. This suggests that different mechanisms are involved in the initiation of the cardiovascular changes. Sustained passive stretch of triceps surae for 1 min, by dorsiflexion of the foot, caused a significant (P < 0.05) increase in HR (5 ± 2.6 beats min−1) with no significant change in BP. A time domain measure of cardiac vagal activity was reduced significantly during passive stretch from 69.7 ± 12.9 to 49.6 ± 8.9 ms. Rapid rhythmic passive stretch (0.5 Hz for 1 min) was without significant effect suggesting that large muscle proprioreceptors are not involved. We conclude that in man small fibre muscle mechanoreceptors responding to stretch, inhibit cardiac vagal activity and thus increase HR. These afferents could contribute to the initial cardiac acceleration in response to muscle contraction. PMID:11986394

  15. Structural Changes in Isometrically Contracting Insect Flight Muscle Trapped following a Mechanical Perturbation

    PubMed Central

    Wu, Shenping; Liu, Jun; Perz-Edwards, Robert J.; Tregear, Richard T.; Winkler, Hanspeter; Franzini-Armstrong, Clara; Sasaki, Hiroyuki; Goldman, Yale E.; Reedy, Michael K.; Taylor, Kenneth A.

    2012-01-01

    The application of rapidly applied length steps to actively contracting muscle is a classic method for synchronizing the response of myosin cross-bridges so that the average response of the ensemble can be measured. Alternatively, electron tomography (ET) is a technique that can report the structure of the individual members of the ensemble. We probed the structure of active myosin motors (cross-bridges) by applying 0.5% changes in length (either a stretch or a release) within 2 ms to isometrically contracting insect flight muscle (IFM) fibers followed after 5–6 ms by rapid freezing against a liquid helium cooled copper mirror. ET of freeze-substituted fibers, embedded and thin-sectioned, provides 3-D cross-bridge images, sorted by multivariate data analysis into ∼40 classes, distinct in average structure, population size and lattice distribution. Individual actin subunits are resolved facilitating quasi-atomic modeling of each class average to determine its binding strength (weak or strong) to actin. ∼98% of strong-binding acto-myosin attachments present after a length perturbation are confined to “target zones” of only two actin subunits located exactly midway between successive troponin complexes along each long-pitch helical repeat of actin. Significant changes in the types, distribution and structure of actin-myosin attachments occurred in a manner consistent with the mechanical transients. Most dramatic is near disappearance, after either length perturbation, of a class of weak-binding cross-bridges, attached within the target zone, that are highly likely to be precursors of strong-binding cross-bridges. These weak-binding cross-bridges were originally observed in isometrically contracting IFM. Their disappearance following a quick stretch or release can be explained by a recent kinetic model for muscle contraction, as behaviour consistent with their identification as precursors of strong-binding cross-bridges. The results provide a detailed model

  16. Torque decrease during submaximal evoked contractions of the quadriceps muscle is linked not only to muscle fatigue.

    PubMed

    Matkowski, Boris; Lepers, Romuald; Martin, Alain

    2015-05-01

    The aim of this study was to analyze the neuromuscular mechanisms involved in the torque decrease induced by submaximal electromyostimulation (EMS) of the quadriceps muscle. It was hypothesized that torque decrease after EMS would reflect the fatigability of the activated motor units (MUs), but also a reduction in the number of MUs recruited as a result of changes in axonal excitability threshold. Two experiments were performed on 20 men to analyze 1) the supramaximal twitch superimposed and evoked at rest during EMS (Experiment 1, n = 9) and 2) the twitch response and torque-frequency relation of the MUs activated by EMS (Experiment 2, n = 11). Torque loss was assessed by 15 EMS-evoked contractions (50 Hz; 6 s on/6 s off), elicited at a constant intensity that evoked 20% of the maximal voluntary contraction (MVC) torque. The same stimulation intensity delivered over the muscles was used to induce the torque-frequency relation and the single electrical pulse evoked after each EMS contraction (Experiment 2). In Experiment 1, supramaximal twitch was induced by femoral nerve stimulation. Torque decreased by ~60% during EMS-evoked contractions and by only ~18% during MVCs. This was accompanied by a rightward shift of the torque-frequency relation of MUs activated and an increase of the ratio between the superimposed and posttetanic maximal twitch evoked during EMS contraction. These findings suggest that the torque decrease observed during submaximal EMS-evoked contractions involved muscular mechanisms but also a reduction in the number of MUs recruited due to changes in axonal excitability. Copyright © 2015 the American Physiological Society.

  17. Muscle architecture and fibre characteristics of rat gastrocnemius and semimembranosus muscles during isometric contractions.

    PubMed

    Huijing, P A; van Lookeren Campagne, A A; Koper, J F

    1989-01-01

    Rat gastrocnemius medialis (GM) and semimembranosus (SM) muscles have a very different morphology. GM is a very pennate muscle, combining relatively short muscle fibre length with sizable fibre angles and long muscle and aponeurosis lengths. SM is a more parallel-fibred muscle, combining a relatively long fibre length with a small fibre angle and short aponeurosis length. The mechanisms of fibre shortening as well as angle increase are operational in GM as well as SM. However, as a consequence of isometric contraction, changes of fibre length and angle are greater for GM than for SM at any relative muscle length. These differences are particularly notable at short muscle lengths: at 80% of optimum muscle length, fibre length changes of approximately 30% are coupled to fibre angle changes of 15 degrees in GM, while for SM these changes are 4% and 0.6 degrees, respectively. A considerable difference was found for normalized active slack muscle length (GM approximately 80 and SM approximately 45%). This is explained by differences of degree of pennation as well as factors related to differences found for estimated fibre length-force characteristics. Estimated normalized active fibre slack length was considerably smaller for SM than for GM (approximately 40 and 60%, respectively). The most likely explanation of these findings are differences of distribution of optimum fibre lengths, possibly in combination with differences of myofilament lengths and/or fibre length distributions.

  18. Postural adjustments associated with voluntary contraction of leg muscles in standing man.

    PubMed

    Nardone, A; Schieppati, M

    1988-01-01

    The postural adjustments associated with a voluntary contraction of the postural muscles themselves have been studied in the legs of normal standing men. We focussed on the following questions. Do postural adjustments precede the focal movement as in the case of movements of the upper limb? Which muscle(s) are involved in the task of stabilizing posture? Can the same postural muscle be activated in postural stabilization and in voluntary movement at the same time, in spite of the opposite changes in activity possibly required by these conditions? Six subjects standing on a dynamometric platform were asked to rise onto the tips their toes by contracting their soleus muscles, or to rock on their heels by contracting their tibialis anterior muscles. The tasks were made in a reaction time (RT) situation or in a self-paced mode, standing either freely or holding onto a stable structure. Surface EMGs of leg and thigh muscles, and the foot-floor reaction forces were recorded. The following results were obtained in the RT mode, standing freely. 1. Rising onto toe tips: a striking silent period in soleus preceded its voluntary activation; during this silent period, a tibialis anterior burst could be observed in three subjects; these anticipatory activities induced a forward sway, as monitored by a change in the force exerted along the x axis of the platform. 2. Rocking on heels: an enhancement in tonic EMG of soleus was observed before tibialis anterior voluntary burst, at a mean latency from the go-signal similar to that of the silent period; this anticipatory activity induced a backward body sway. 3. Choice RT conditions showed that the above anticipatory patterns in muscle activity were pre-programmed, specific for the intended tasks, and closely associated with the focal movement. When both tasks were performed in a self-paced mode, all the above EMG and mechanical features were more pronounced and unfolded in time. If the subjects held onto the frame, the early

  19. [Clinical profile of persistent generalized muscle contraction following the insult of developing brain].

    PubMed

    Maruyama, Koichi; Iai, Mizue; Arai, Hiroshi; Yokochi, Kenji

    2014-01-01

    Persons with severe motor and intellectual disabilities (SMID) caused by injury to the developing brain sometimes present generalized hypertonia in a specific position with extreme muscle overactivity persisting for most of the time during wakefulness. This "persistent generalized muscle contraction" is often associated with bad humor, sleep disturbance, hyperhidrosis, wasting, elevation of serum creatine kinase levels, regular daytime use of hypnotic or sedative medication, and the necessity to maintain the neck or hip in a flexed position manually. The aim of this study is to elucidate the clinical profile of this condition. We retrospectively examined the medical records and brain imaging data of 66 SMID patients in the state of persistent generalized muscle contraction. Most patients could be classified into 2 major categories on the basis of clinical presentation and brain imaging: (A) those with premature birth and bilateral lesion of globus pallidus interna (kernicterus) (n = 16), and (B) those with various widespread bilateral basal ganglia/thalamic and/or cerebral lesions such as hypoxia-ischemia, acute encephalopathy, malformation, etc (n = 50). Group A assumed an asymmetrical tonic-neck-reflex-like position, torsion of the trunk, fluctuation of hypertonia, and better mental development. Three of them exhibited extreme hypertonia resembling status dystonicus. Group B often exhibited persistent and fixed retroflexion of the neck and trunk or opisthotonus. Drugs such as oral muscular relaxants were ineffective in both groups. Injection of botulinum toxin into the cervical and paravertebral muscles partially alleviated symptoms. Persistent generalized muscle contraction in SMID has at least two different types. Group A has characteristics of severe dystonic hypertonia that could lead to status dystonicus. Group B might have peculiar characteristics of muscle overactivity triggered by wakefulness or discomfort, which probably results from inability to achieve

  20. Gender differences in the regulation of MLC20 phosphorylation and smooth muscle contraction in rat stomach

    PubMed Central

    Al-Shboul, Othman A.; Al-Dwairi, Ahmed N.; Alqudah, Mohammad A.; Mustafa, Ayman G.

    2018-01-01

    Evidence of sex-related differences in gastrointestinal (GI) functions has been reported in the literature. In addition, various GI disorders have disproportionate prevalence between the sexes. An essential step in the initiation of smooth muscle contraction is the phosphorylation of the 20-kDa regulatory myosin light chain (MLC20) by the Ca2+/calmodulin-dependent myosin light chain kinase (MLCK). However, whether male stomach smooth muscle inherits different contractile signaling mechanisms for the regulation of MLC20 phosphorylation from that in females has not been established. The present study was designed to investigate sex-associated differences in the regulation of MLC20 phosphorylation and thus muscle contraction in gastric smooth muscle cells (GSMCs). Experiments were performed on GSMCs freshly isolated from male and female rats. Contraction of the GSMCs in response to acetylcholine (ACh), a muscarinic agonist, was measured via scanning micrometry in the presence or absence of the MLCK inhibitor, ML-7. Additionally, the protein levels of MLC20, MLCK and phosphorylated MLC20 were measured by ELISA. The protein levels of MLC20 and MLCK were indifferent between the sexes. ACh induced greater contraction (P<0.05) as well as greater MLC20 phosphorylation (P<0.05) in male GSMCs compared with female. Pretreatment of GSMCs with ML-7 significantly reduced the ACh-induced contraction (P<0.05) and MLC20 phosphorylation (P<0.05) in the male and female cells, and notably, abolished the contractile differences between the sexes. In conclusion, MLC20 phosphorylation and thus muscle contraction may be activated to a greater extent in male rat stomach compared with that in females. PMID:29599980

  1. Comparison in muscle damage between maximal voluntary and electrically evoked isometric contractions of the elbow flexors.

    PubMed

    Jubeau, Marc; Muthalib, Makii; Millet, Guillaume Y; Maffiuletti, Nicola A; Nosaka, Kazunori

    2012-02-01

    This study compared between maximal voluntary (VOL) and electrically stimulated (ES) isometric contractions of the elbow flexors for changes in indirect markers of muscle damage to investigate whether ES would induce greater muscle damage than VOL. Twelve non-resistance-trained men (23-39 years) performed VOL with one arm and ES with the contralateral arm separated by 2 weeks in a randomised, counterbalanced order. Both VOL and ES (frequency 75 Hz, pulse duration 250 μs, maximally tolerated intensity) exercises consisted of 50 maximal isometric contractions (4-s on, 15-s off) of the elbow flexors at a long muscle length (160°). Changes in maximal voluntary isometric contraction torque (MVC), range of motion, muscle soreness, pressure pain threshold and serum creatine kinase (CK) activity were measured before, immediately after and 1, 24, 48, 72 and 96 h following exercise. The average peak torque over the 50 isometric contractions was greater (P < 0.05) for VOL (32.9 ± 9.8 N m) than ES (16.9 ± 6.3 N m). MVC decreased greater and recovered slower (P < 0.05) after ES (15% lower than baseline at 96 h) than VOL (full recovery). Serum CK activity increased (P < 0.05) only after ES, and the muscles became more sore and tender after ES than VOL (P < 0.05). These results showed that ES induced greater muscle damage than VOL despite the lower torque output during ES. It seems likely that higher mechanical stress imposed on the activated muscle fibres, due to the specificity of motor unit recruitment in ES, resulted in greater muscle damage.

  2. Brain-derived neurotrophic factor enhances cholinergic contraction of longitudinal muscle of rabbit intestine via activation of phospholipase C

    PubMed Central

    Al-Qudah, M.; Anderson, C. D.; Mahavadi, S.; Bradley, Z. L.; Akbarali, H. I.; Murthy, K. S.

    2013-01-01

    Brain-derived neurotrophic factor (BDNF) belongs to the neurotrophin family of proteins best known for its role in neuronal survival, differentiation, migration, and synaptic plasticity in central and peripheral neurons. BDNF is also widely expressed in nonneuronal tissues including the gastrointestinal tract. The role of BDNF in intestinal smooth muscle contractility is not well defined. The aim of this study was to identify the role of BDNF in carbachol (CCh)- and substance P (SP)-induced contraction of intestinal longitudinal smooth muscle. BDNF, selective tropomyosin-related kinase B (TrkB) receptor agonists, and pharmacological inhibitors of signaling pathways were examined for their effects on contraction of rabbit intestinal longitudinal muscle strips induced by CCh and SP. BDNF activation of intracellular signaling pathways was examined by Western blot in homogenates of muscle strips and isolated muscle cells. One-hour preincubation with BDNF enhanced intestinal muscle contraction induced by CCh but not by SP. The selective synthetic TrkB agonists LM 22A4 and 7,8-dihydroxyflavone produced similar effects to BDNF. The Trk antagonist K-252a, a TrkB antibody but not p75NTR antibody, blocked the effect of BDNF. The enhancement of CCh-induced contraction by BDNF was blocked by the phospholipase C (PLC) antagonist U73122, but not by ERK1/2 or Akt antagonists. Direct measurement in muscle strips and isolated muscle cells showed that BDNF caused phosphorylation of TrkB receptors and PLC-γ, but not ERK1/2 or Akt. We conclude that exogenous BDNF augments the CCh-induced contraction of longitudinal muscle from rabbit intestine by activating TrkB receptors and subsequent PLC activation. PMID:24356881

  3. Brain-derived neurotrophic factor enhances cholinergic contraction of longitudinal muscle of rabbit intestine via activation of phospholipase C.

    PubMed

    Al-Qudah, M; Anderson, C D; Mahavadi, S; Bradley, Z L; Akbarali, H I; Murthy, K S; Grider, J R

    2014-02-15

    Brain-derived neurotrophic factor (BDNF) belongs to the neurotrophin family of proteins best known for its role in neuronal survival, differentiation, migration, and synaptic plasticity in central and peripheral neurons. BDNF is also widely expressed in nonneuronal tissues including the gastrointestinal tract. The role of BDNF in intestinal smooth muscle contractility is not well defined. The aim of this study was to identify the role of BDNF in carbachol (CCh)- and substance P (SP)-induced contraction of intestinal longitudinal smooth muscle. BDNF, selective tropomyosin-related kinase B (TrkB) receptor agonists, and pharmacological inhibitors of signaling pathways were examined for their effects on contraction of rabbit intestinal longitudinal muscle strips induced by CCh and SP. BDNF activation of intracellular signaling pathways was examined by Western blot in homogenates of muscle strips and isolated muscle cells. One-hour preincubation with BDNF enhanced intestinal muscle contraction induced by CCh but not by SP. The selective synthetic TrkB agonists LM 22A4 and 7,8-dihydroxyflavone produced similar effects to BDNF. The Trk antagonist K-252a, a TrkB antibody but not p75NTR antibody, blocked the effect of BDNF. The enhancement of CCh-induced contraction by BDNF was blocked by the phospholipase C (PLC) antagonist U73122, but not by ERK1/2 or Akt antagonists. Direct measurement in muscle strips and isolated muscle cells showed that BDNF caused phosphorylation of TrkB receptors and PLC-γ, but not ERK1/2 or Akt. We conclude that exogenous BDNF augments the CCh-induced contraction of longitudinal muscle from rabbit intestine by activating TrkB receptors and subsequent PLC activation.

  4. ALUMINUM CHLORIDE EFFECT ON Ca2+,Mg(2+)-ATPase ACTIVITY AND DYNAMIC PARAMETERS OF SKELETAL MUSCLE CONTRACTION.

    PubMed

    Nozdrenko, D M; Abramchuk, O M; Soroca, V M; Miroshnichenko, N S

    2015-01-01

    We studied enzymatic activity and measured strain-gauge contraction properties of the frog Rana temporaria m. tibialis anterior muscle fascicles during the action of aluminum chloride solution. It was shown that AlCl3 solutions did not affect the dynamic properties of skeletal muscle preparation in concentrations less than 10(-4) M Increasing the concentration of AlCl3 to 10(-2) M induce complete inhibition of muscle contraction. A linear correlation between decrease in Ca2+,Mg(2+)-ATPase activity of sarcoplasmic reticulum and the investigated concentrations range of aluminum chloride was observed. The reduction in the dynamic contraction performance and the decrease Ca2+,Mg(2+)-ATPase activity of the sarcoplasmic reticulum under the effect of the investigated AlCl3 solution were minimal in pre-tetanus period of contraction.

  5. Characterization of the mechanomyographic signal of three different muscles and at different levels of isometric contractions.

    PubMed

    Jotta, Bruno; Cavalcanti Garcia, Marco Antonio; Visintainer Pino, Alexandre; De Souza, Marcio Nogueira

    2015-01-01

    Lateral (X) and longitudinal (Y) mechanical oscillations of muscle fibers that take place during muscular contraction seem to contain information additionally to the myoelectric activity, which can contribute to the interpretation of some muscle gradation force mechanisms. However, no previous study was found that had investigated the relationship between the muscle force and features associated to the mechanomyographic (MMG) signal obtained by means of a biaxial accelerometer in three different muscles. Therefore, the aim of this study was to evaluate the relationship between the force output at different load levels (20% to 100%) of the maximum voluntary isometric contraction (%MVIC) and the two signals supplied by a biaxial accelerometer and, in addition, the so-called resultant (R) acceleration signal derived from the two signals mentioned previously. Twenty seven male volunteers participated in this study. The force output related to the right biceps brachii, soleus and gastrocnemius medialis muscles was studied by means of linear regression models fit to log-transformed of the root mean square (RMS) values of the MMG signals in X, Y, and R axes versus each %MVIC. The phase angle of R acceleration (PhaseR) and anthropometric data were also considered. The angular coefficient a and the antilog of y-intercept b from the log-transformed of MMG data values versus force output were able to distinguish partially motor unit strategies during isometric contractions in the three muscles studied. The findings suggest that biaxial accelerometer seems to be an interesting approach in the assessment of muscle contraction properties.

  6. Muscle contraction and the elasticity-mediated crosstalk effect

    NASA Astrophysics Data System (ADS)

    Dharan, Nadiv; Farago, Oded

    2013-05-01

    Cooperative action of molecular motors is essential for many cellular processes. One possible regulator of motor coordination is the elasticity-mediated crosstalk (EMC) coupling between myosin II motors whose origin is the tensile stress that they collectively generate in actin filaments. Here, we use a statistical mechanical analysis to investigate the influence of the EMC effect on the sarcomere — the basic contractile unit of skeletal muscles. We demonstrate that the EMC effect leads to an increase in the attachment probability of motors located near the end of the sarcomere while simultaneously decreasing the attachment probability of the motors in the central part. Such a polarized attachment probability would impair the motors' ability to cooperate efficiently. Interestingly, this undesired phenomenon becomes significant only when the system size exceeds that of the sarcomere in skeletal muscles, which provides an explanation for the remarkable lack of sarcomere variability in vertebrates. Another phenomenon that we investigate is the recently observed increase in the duty ratio of the motors with the tension in muscle. We reveal that the celebrated Hill's equation for muscle contraction is very closely related to this observation.

  7. No effect of NOS inhibition on skeletal muscle glucose uptake during in situ hindlimb contraction in healthy and diabetic Sprague-Dawley rats.

    PubMed

    Hong, Yet Hoi; Betik, Andrew C; Premilovac, Dino; Dwyer, Renee M; Keske, Michelle A; Rattigan, Stephen; McConell, Glenn K

    2015-05-15

    Nitric oxide (NO) has been shown to be involved in skeletal muscle glucose uptake during contraction/exercise, especially in individuals with Type 2 diabetes (T2D). To examine the potential mechanisms, we examined the effect of local NO synthase (NOS) inhibition on muscle glucose uptake and muscle capillary blood flow during contraction in healthy and T2D rats. T2D was induced in Sprague-Dawley rats using a combined high-fat diet (23% fat wt/wt for 4 wk) and low-dose streptozotocin injections (35 mg/kg). Anesthetized animals had one hindlimb stimulated to contract in situ for 30 min (2 Hz, 0.1 ms, 35 V) with the contralateral hindlimb rested. After 10 min, the NOS inhibitor, N(G)-nitro-l-arginine methyl ester (l-NAME; 5 μM) or saline was continuously infused into the femoral artery of the contracting hindlimb until the end of contraction. Surprisingly, there was no increase in skeletal muscle NOS activity during contraction in either group. Local NOS inhibition had no effect on systemic blood pressure or muscle contraction force, but it did cause a significant attenuation of the increase in femoral artery blood flow in control and T2D rats. However, NOS inhibition did not attenuate the increase in muscle capillary recruitment during contraction in these rats. Muscle glucose uptake during contraction was significantly higher in T2D rats compared with controls but, unlike our previous findings in hooded Wistar rats, NOS inhibition had no effect on glucose uptake during contraction. In conclusion, NOS inhibition did not affect muscle glucose uptake during contraction in control or T2D Sprague-Dawley rats, and this may have been because there was no increase in NOS activity during contraction. Copyright © 2015 the American Physiological Society.

  8. The effects of age and muscle contraction on AMPK activity and heterotrimer composition.

    PubMed

    Hardman, Shalene E; Hall, Derrick E; Cabrera, Alyssa J; Hancock, Chad R; Thomson, David M

    2014-07-01

    Sarcopenia is characterized by increased skeletal muscle atrophy due in part to alterations in muscle metabolism. AMP-activated protein kinase (AMPK) is a master regulator of skeletal muscle metabolic pathways which regulate many cellular processes that are disrupted in old-age. Functional AMPK is a heterotrimer composed of α, β and γ subunits, and each subunit can be represented in the heterotrimer by one of two (α1/α2, β1/β2) or three (γ1/γ2/γ3) isoforms. Altered isoform composition affects AMPK localization and function. Previous work has shown that overall AMPK activation with endurance-type exercise is blunted in old vs. young skeletal muscle. However, details regarding the activation of the specific isoforms of AMPK, as well as the heterotrimeric composition of AMPK in old skeletal muscle, are unknown. Our purpose here, therefore, was to determine the effect of old-age on 1) the activation of the α1 and α2 catalytic subunits of AMPK in skeletal muscle by a continuous contraction bout, and 2) the heterotrimeric composition of skeletal muscle AMPK. We studied gastrocnemius (GAST) and tibialis anterior (TA) muscles from young adult (YA; 8months old) and old (O; 30months old) male Fischer344×Brown Norway F1 hybrid rats after an in situ bout of endurance-type contractions produced via electrical stimulation of the sciatic nerve (STIM). AMPKα phosphorylation and AMPKα1 and α2 activities were unaffected by age at rest. However, AMPKα phosphorylation and AMPKα2 protein content and activity were lower in O vs. YA after STIM. Conversely, AMPKα1 content was greater in O vs. YA muscle, and α1 activity increased with STIM in O but not YA muscles. AMPKγ3 overall concentration and its association with AMPKα1 and α2 were lower in O vs. YA GAST. We conclude that activation of AMPKα1 is enhanced, while activation of α2 is suppressed immediately after repeated skeletal muscle contractions in O vs. YA skeletal muscle. These changes are associated with

  9. Extracellular formation and uptake of adenosine during skeletal muscle contraction in the rat: role of adenosine transporters

    PubMed Central

    Lynge, J; Juel, C; Hellsten, Y

    2001-01-01

    The existence of adenosine transporters in plasma membrane giant vesicles from rat skeletal muscles and in primary skeletal muscle cell cultures was investigated. In addition, the contribution of intracellularly or extracellularly formed adenosine to the overall extracellular adenosine concentration during muscle contraction was determined in primary skeletal muscle cell cultures. In plasma membrane giant vesicles, the carrier-mediated adenosine transport demonstrated saturation kinetics with Km= 177 ± 36 μm and Vmax= 1.9 ± 0.2 nmol ml−1 s−1 (0.7 nmol (mg protein)−1 s−1). The existence of an adenosine transporter was further evidenced by the inhibition of the carrier-mediated adenosine transport in the presence of NBMPR (nitrobenzylthioinosine; 72 % inhibition) or dipyridamol (64 % inhibition; P < 0.05). In primary skeletal muscle cells, the rate of extracellular adenosine accumulation was 5-fold greater (P < 0.05) with electrical stimulation than without electrical stimulation. Addition of the adenosine transporter inhibitor NBMPR led to a 57 % larger (P < 0.05) rate of extracellular adenosine accumulation in the electro-stimulated muscle cells compared with control cells, demonstrating that adenosine is taken up by the skeletal muscle cells during contractions. Inhibition of ecto-5′-nucleotidase with AOPCP in electro-stimulated cells resulted in a 70 % lower (P < 0.05) rate of extracellular adenosine accumulation compared with control cells, indicating that adenosine to a large extent is formed in the extracellular space during contraction. The present study provides evidence for the existence of an NBMPR-sensitive adenosine transporter in rat skeletal muscle. Our data furthermore demonstrate that the increase in extracellular adenosine observed during electro-stimulation of skeletal muscle is due to production of adenosine in the extracellular space of skeletal muscle and that adenosine is taken up rather than released by the skeletal muscle cells

  10. Muscle contraction is required to maintain the pool of muscle progenitors via YAP and NOTCH during fetal myogenesis.

    PubMed

    Esteves de Lima, Joana; Bonnin, Marie-Ange; Birchmeier, Carmen; Duprez, Delphine

    2016-08-24

    The importance of mechanical activity in the regulation of muscle progenitors during chick development has not been investigated. We show that immobilization decreases NOTCH activity and mimics a NOTCH loss-of-function phenotype, a reduction in the number of muscle progenitors and increased differentiation. Ligand-induced NOTCH activation prevents the reduction of muscle progenitors and the increase of differentiation upon immobilization. Inhibition of NOTCH ligand activity in muscle fibers suffices to reduce the progenitor pool. Furthermore, immobilization reduces the activity of the transcriptional co-activator YAP and the expression of the NOTCH ligand JAG2 in muscle fibers. YAP forced-activity in muscle fibers prevents the decrease of JAG2 expression and the number of PAX7+ cells in immobilization conditions. Our results identify a novel mechanism acting downstream of muscle contraction, where YAP activates JAG2 expression in muscle fibers, which in turn regulates the pool of fetal muscle progenitors via NOTCH in a non-cell-autonomous manner.

  11. Role of intrinsic nitrergic neurones on vagally mediated striated muscle contractions in the hamster oesophagus

    PubMed Central

    Izumi, Noriaki; Matsuyama, Hayato; Ko, Mifa; Shimizu, Yasutake; Takewaki, Tadashi

    2003-01-01

    Oesophageal peristalsis is controlled by vagal motor neurones, and intrinsic neurones have been identified in the striated muscle oesophagus. However, the effect(s) of intrinsic neurones on vagally mediated contractions of oesophageal striated muscles has not been defined. The present study was designed to investigate the role of intrinsic neurones on vagally evoked contractions of oesophageal striated muscles, using hamster oesophageal strips maintained in an organ bath. Stimulation (30 μs, 20 V) of the vagus nerve trunk produced twitch contractions. Piperine inhibited vagally evoked contractions, while capsaicin and NG-nitro-L-arginine methyl ester (L-NAME) abolished the inhibitory effect of piperine. The effect of L-NAME was reversed by subsequent addition of L-arginine, but not by D-arginine. L-NAME did not have any effect on the vagally mediated contractions and presumed 3H-ACh release. NONOate, a nitric oxide donor, and dibutyryl cyclic GMP inhibited twitch contractions. Inhibition of vagally evoked contractions by piperine and NONOate was fully reversed by ODQ, an inhibitor of guanylate cyclase. Immunohistochemical staining showed immunoreactivity for nitric oxide synthase (NOS) in nerve cell bodies and fibres in the myenteric plexus and the presence of choline acetyltransferase and NOS in the motor endplates. Only a few NOS-immunoreactive portions in the myenteric plexus showed vanilloid receptor 1 (VR1) immunoreactivity. Our results suggest that there is a local neural reflex that involves capsaicin-sensitive neurones, nitrergic myenteric neurones and vagal motor neurones. PMID:12813149

  12. The effect of SIRT1 protein knock down on PGC-1α acetylation during skeletal muscle contraction.

    PubMed

    Park, Dae Ryoung; Kim, Jeong Seok; Kim, Chang Keun

    2014-03-01

    The purpose of this study was to investigate the effect of Sirtuin 1 (SIRT1) and General control nonderepressible 5 (GCN5) knock down on peroxisome proliferator- activated receptor gamma coactivator 1-alpha (PGC-1α) deacetylation during electrical stimulated skeletal muscle contraction. Skeletal muscle primary cell were isolated from C57BL/6 mice gastrocnemius and transfected lentiviral SIRT1 and GCN5 shRNA. Knock downed muscle cell were stimulated by electrical stimulation (1Hz, 3min) and collected for PGC-1α deceatylation assays. Immunoprecipitation performed for PGC-1α deacetylation, acetyl-lysine level was measured. Our resulted showed SIRT1 knock down not influenced to PGC-1α deacetylation during electrical stimulation induced muscle contraction while GCN5 knock down decreased PGC-1α deacetylation significantly (p<0.05). This study can be concluded that GCN5 is a critical factor for muscle contraction induced PGC-1α deacetylation.

  13. Impact of Different Body Positions on Bioelectrical Activity of the Pelvic Floor Muscles in Nulliparous Continent Women

    PubMed Central

    Chmielewska, Daria; Stania, Magdalena; Sobota, Grzegorz; Kwaśna, Krystyna; Błaszczak, Edward; Taradaj, Jakub; Juras, Grzegorz

    2015-01-01

    We examined pelvic floor muscles (PFM) activity (%MVC) in twenty nulliparous women by body position during exercise as well as the activation of abdominal muscles and the gluteus maximus during voluntary contractions of the PFMs. Pelvic floor muscle activity was recorded using a vaginal probe during five experimental trials. Activation of transversus abdominis, rectus abdominis, and gluteus maximus during voluntary PFM contractions was also assessed. Significant differences in mean normalized amplitudes of baseline PFM activity were revealed between standing and lying (P < 0.00024) and lying and ball-sitting positions (P < 0.0053). Average peak, average time before peak, and average time after peak did not differ significantly during the voluntary contractions of the PFMs. Baseline PFM activity seemed to depend on the body position and was the highest in standing. Pelvic floor muscles activity during voluntary contractions did not differ by position in continent women. Statistically significant differences between the supine lying and sitting positions were only observed during a sustained 60-second contraction of the PFMs. PMID:25793212

  14. Cervical Muscle Strength and Muscle Coactivation During Isometric Contractions in Patients With Migraine: A Cross-Sectional Study.

    PubMed

    Florencio, Lidiane Lima; de Oliveira, Anamaria Siriani; Carvalho, Gabriela Ferreira; Tolentino, Gabriella de Almeida; Dach, Fabiola; Bigal, Marcelo Eduardo; Fernández-de-las-Peñas, César; Bevilaqua Grossi, Débora

    2015-01-01

    This cross-sectional study investigated potential differences in cervical musculature in groups of migraine headaches vs. non-headache controls. Differences in cervical muscle strength and antagonist coactivation during maximal isometric voluntary contraction (MIVC) were analyzed between individuals with migraine and non-headache subjects and relationships between force with migraine and neck pain clinical aspects. A customized hand-held dynamometer was used to assess cervical flexion, extension, and bilateral lateral flexion strength in subjects with episodic migraine (n=31), chronic migraine (n = 21) and healthy controls (n = 31). Surface electromyography (EMG) from sternocleidomastoid, anterior scalene, and splenius capitis muscles were recorded during MIVC to evaluate antagonist coactivation. Comparison of main outcomes among groups was conducted with one-way analysis of covariance with the presence of neck pain as covariable. Correlations between peak force and clinical variables were demonstrated by Spearman's coefficient. Chronic migraine subjects exhibited lower cervical extension force (mean diff. from controls: 4.4 N/kg; mean diff from episodic migraine: 3.7 N/kg; P = .006) and spent significantly more time to generate peak force during cervical flexion (mean diff. from controls: 0.5 seconds; P = .025) and left lateral-flexion (mean diff. from controls: 0.4 seconds; mean diff. from episodic migraine: 0.5 seconds; P = .007). Both migraine groups showed significantly higher antagonist muscle coactivity of the splenius capitis muscle (mean diff. from controls: 20%MIVC, P = .03) during cervical flexion relative to healthy controls. Cervical extension peak force was moderately associated with the migraine frequency (rs: -0.30, P = .034), neck pain frequency (rs: -0.26, P = .020), and neck pain intensity (rs: -0.27, P = .012). Patients with chronic migraine exhibit altered muscle performance, took longer to reach peak of

  15. The impact of extracellular and intracellular Ca2+ on ethanol-induced smooth muscle contraction.

    PubMed

    Döndaş, Naciye Yaktubay; Kaplan, Mahir; Kaya, Derya; Singirik, Ergin

    2009-10-01

    To evaluate the impact of extracellular and intracellular Ca2+ on contractions induced by ethanol in smooth muscle. Longitudinal smooth muscle strips were prepared from the gastric fundi of mice. The contractions of smooth muscle strips were recorded with an isometric force displacement transducer. Ethanol (164 mmol/L) produced reproducible contractions in isolated gastric fundal strips of mice. Although lidocaine (50 and 100 micromol/L), a local anesthetic agent, and hexamethonium (100 and 500 micromol/L), a ganglionic blocking agent, failed to affect these contractions, verapamil (1-50 micromol/L) and nifedipine (1-50 micromol/L), selective blockers of L-type Ca2+ channels, significantly inhibited the contractile responses of ethanol. Using a Ca(2+)-free medium nearly eliminated these contractions in the same tissue. Ryanodine (1-50 micromol/L) and ruthenium red (10-100 micromol/L), selective blockers of intracellular Ca2+ channels/ryanodine receptors; cyclopiazonic acid (CPA; 1-10 mumol/L), a selective inhibitor of sarcoplasmic reticulum (SR) Ca(2+)-ATPase; and caffeine (0.5-5 mmol/L), a depleting agent of intracellular Ca2+ stores, significantly inhibited the contractile responses induced by ethanol. In addition, the combination of caffeine (5 mmol/L) plus CPA (10 micromol/L), and ryanodine (10 micromol/L) plus CPA (10 micromol/L), caused further inhibition of contractions in response to ethanol. This inhibition was significantly different from those associated with caffeine, ryanodine or CPA. Furthermore the combination of caffeine (5 mmol/L), ryanodine (10 micromol/L) and CPA(10 micromol/L) eliminated the contractions induced by ethanol in isolated gastric fundal strips of mice. Both extracellular and intracellular Ca2+ may have important roles in regulating contractions induced by ethanol in the mouse gastric fundus.

  16. Relative changes with contraction in the central excitability state of the tibialis anterior and calf muscles.

    PubMed Central

    Fisher, M A

    1980-01-01

    F responses were recorded from the surface of the tibialis muscle and medial aspect of the soleus muscle in 14 normal subjects. The persistence (that is the fraction of measurable F responses found with a series of supramaximal stimuli) and average F amplitudes (measured peak-to-peak and based on at least five F responses) were determined both at rest and with isometric contraction with the ankle maintained at 90 degrees. Although the persistence at rest was significantly less in the tibialis anterior soleus than the (p less than 0.001), no significant difference was found with the muscles contracted. This was associated with a significant increase in both average F amplitudes and average F amplitude/direct motor response ratios in the tibialis anterior in comparison to the soleus. In four of the subjects, studies were also performed when the H reflex in the soleus muscle was eliminated by thigh compression. Comparable changes in both F response persistence and average F amplitude were found with and without an H reflex. These data indicate that, in contrast to the situation at rest, with isometric contraction the "central excitatory state" of the tibialis anterior is at least as great as in its antagonist antigravity muscles and that this is not due simply to increased large fiber reflex input associated with agonist contraction. PMID:7373321

  17. Analysis of concentric and eccentric contractions in biceps brachii muscles using surface electromyography signals and multifractal analysis.

    PubMed

    Marri, Kiran; Swaminathan, Ramakrishnan

    2016-06-23

    Muscle contractions can be categorized into isometric, isotonic (concentric and eccentric) and isokinetic contractions. The eccentric contractions are very effective for promoting muscle hypertrophy and produce larger forces when compared to the concentric or isometric contractions. Surface electromyography signals are widely used for analyzing muscle activities. These signals are nonstationary, nonlinear and exhibit self-similar multifractal behavior. The research on surface electromyography signals using multifractal analysis is not well established for concentric and eccentric contractions. In this study, an attempt has been made to analyze the concentric and eccentric contractions associated with biceps brachii muscles using surface electromyography signals and multifractal detrended moving average algorithm. Surface electromyography signals were recorded from 20 healthy individuals while performing a single curl exercise. The preprocessed signals were divided into concentric and eccentric cycles and in turn divided into phases based on range of motion: lower (0°-90°) and upper (>90°). The segments of surface electromyography signal were subjected to multifractal detrended moving average algorithm, and multifractal features such as strength of multifractality, peak exponent value, maximum exponent and exponent index were extracted in addition to conventional linear features such as root mean square and median frequency. The results show that surface electromyography signals exhibit multifractal behavior in both concentric and eccentric cycles. The mean strength of multifractality increased by 15% in eccentric contraction compared to concentric contraction. The lowest and highest exponent index values are observed in the upper concentric and lower eccentric contractions, respectively. The multifractal features are observed to be helpful in differentiating surface electromyography signals along the range of motion as compared to root mean square and median

  18. Evaluation of the innate immune-stimulating activity of amazake using a silkworm muscle contraction assay.

    PubMed

    Maruki-Uchida, Hiroko; Sai, Masahiko; Sekimizu, Kazuhisa

    2017-11-22

    We evaluated the innate immune-stimulating activity of amazake using a silkworm muscle contraction assay. Sake cake, a raw material used to make amazake, had high innate immunity-stimulating activity, whereas rice malt, another raw material used to make amazake, did not, even after fermentation. These results suggest that the silkworm muscle contraction assay is a useful tool to screen foods with high innate immune-stimulating activity and that amazake made from sake cake has immunomodulatory potential.

  19. Differences of muscle co-contraction of the ankle joint between young and elderly adults during dynamic postural control at different speeds.

    PubMed

    Iwamoto, Yoshitaka; Takahashi, Makoto; Shinkoda, Koichi

    2017-08-02

    Agonist and antagonist muscle co-contractions during motor tasks are greater in the elderly than in young adults. During normal walking, muscle co-contraction increases with gait speed in young adults, but not in elderly adults. However, no study has compared the effects of speed on muscle co-contraction of the ankle joint during dynamic postural control in young and elderly adults. We compared muscle co-contractions of the ankle joint between young and elderly subjects during a functional stability boundary test at different speeds. Fifteen young adults and 16 community-dwelling elderly adults participated in this study. The task was functional stability boundary tests at different speeds (preferred and fast). Electromyographic evaluations of the tibialis anterior and soleus were recorded. The muscle co-contraction was evaluated using the co-contraction index (CI). There were no statistically significant differences in the postural sway parameters between the two age groups. Elderly subjects showed larger CI in both speed conditions than did the young subjects. CI was higher in the fast speed condition than in the preferred speed condition in the young subjects, but there was no difference in the elderly subjects. Moreover, after dividing the analytical range into phases (acceleration and deceleration phases), the CI was larger in the deceleration phase than in the acceleration phase in both groups, except for the young subjects in the fast speed conditions. Our results showed a greater muscle co-contraction of the ankle joint during dynamic postural control in elderly subjects than in young subjects not only in the preferred speed condition but also in the fast speed condition. In addition, the young subjects showed increased muscle co-contraction in the fast speed condition compared with that in the preferred speed condition; however, the elderly subjects showed no significant difference in muscle co-contraction between the two speed conditions. This indicates

  20. Electrically induced contraction levels of the quadriceps femoris muscles in healthy men: the effects of three patterns of burst-modulated alternating current and volitional muscle fatigue.

    PubMed

    Parker, Michael G; Broughton, Alex J; Larsen, Ben R; Dinius, Josh W; Cimbura, Mac J; Davis, Matthew

    2011-12-01

    The purpose of this study was to compare electrically induced contraction levels produced by three patterns of alternating current in fatigued and nonfatigued skeletal muscles. Eighteen male volunteers without health conditions, with a mean (SD) age of 24.9 (3.4) yrs were randomly exposed to a fatiguing volitional isometric quadriceps contraction and one of three patterns of 2.5-KHz alternating current; two were modulated at 50 bursts per second (10% burst duty cycle with five cycles per burst and 90% burst duty cycle with 45 cycles per burst), and one pattern was modulated at 100 bursts per second (10% burst duty cycle with 2.5 cycles per burst). The electrically induced contraction levels produced by the three patterns of electrical stimulation were compared before and after the fatiguing contraction. The 10% burst duty cycles produced 42.9% (95% confidence interval, 29.1%-56.7%) and 32.1% (95% confidence interval, 18.2%-45.9%) more muscle force (P < 0.001) than did the 90% burst duty cycle pattern. There was no significant interaction effect (P = 0.392) of electrical stimulation patterns and fatigue on the electrically induced contraction levels. The lower burst duty cycle (10%) patterns of electrical stimulation produced stronger muscle contractions. Furthermore, the stimulation patterns had no influence on the difference in muscle force before and after the fatiguing quadriceps contraction. Consequently, for clinical applications in which high forces are desired, the patterns using the 10% burst duty cycle may be helpful.

  1. Presence and Absence of Muscle Contraction Elicited by Peripheral Nerve Electrical Stimulation Differentially Modulate Primary Motor Cortex Excitability.

    PubMed

    Sasaki, Ryoki; Kotan, Shinichi; Nakagawa, Masaki; Miyaguchi, Shota; Kojima, Sho; Saito, Kei; Inukai, Yasuto; Onishi, Hideaki

    2017-01-01

    Modulation of cortical excitability by sensory inputs is a critical component of sensorimotor integration. Sensory afferents, including muscle and joint afferents, to somatosensory cortex (S1) modulate primary motor cortex (M1) excitability, but the effects of muscle and joint afferents specifically activated by muscle contraction are unknown. We compared motor evoked potentials (MEPs) following median nerve stimulation (MNS) above and below the contraction threshold based on the persistence of M-waves. Peripheral nerve electrical stimulation (PES) conditions, including right MNS at the wrist at 110% motor threshold (MT; 110% MNS condition), right MNS at the index finger (sensory digit nerve stimulation [DNS]) with stimulus intensity approximately 110% MNS (DNS condition), and right MNS at the wrist at 90% MT (90% MNS condition) were applied. PES was administered in a 4 s ON and 6 s OFF cycle for 20 min at 30 Hz. In Experiment 1 ( n = 15), MEPs were recorded from the right abductor pollicis brevis (APB) before (baseline) and after PES. In Experiment 2 ( n = 15), M- and F-waves were recorded from the right APB. Stimulation at 110% MNS at the wrist evoking muscle contraction increased MEP amplitudes after PES compared with those at baseline, whereas DNS at the index finger and 90% MNS at the wrist not evoking muscle contraction decreased MEP amplitudes after PES. M- and F-waves, which reflect spinal cord or muscular and neuromuscular junctions, did not change following PES. These results suggest that muscle contraction and concomitant muscle/joint afferent inputs specifically enhance M1 excitability.

  2. Presence and Absence of Muscle Contraction Elicited by Peripheral Nerve Electrical Stimulation Differentially Modulate Primary Motor Cortex Excitability

    PubMed Central

    Sasaki, Ryoki; Kotan, Shinichi; Nakagawa, Masaki; Miyaguchi, Shota; Kojima, Sho; Saito, Kei; Inukai, Yasuto; Onishi, Hideaki

    2017-01-01

    Modulation of cortical excitability by sensory inputs is a critical component of sensorimotor integration. Sensory afferents, including muscle and joint afferents, to somatosensory cortex (S1) modulate primary motor cortex (M1) excitability, but the effects of muscle and joint afferents specifically activated by muscle contraction are unknown. We compared motor evoked potentials (MEPs) following median nerve stimulation (MNS) above and below the contraction threshold based on the persistence of M-waves. Peripheral nerve electrical stimulation (PES) conditions, including right MNS at the wrist at 110% motor threshold (MT; 110% MNS condition), right MNS at the index finger (sensory digit nerve stimulation [DNS]) with stimulus intensity approximately 110% MNS (DNS condition), and right MNS at the wrist at 90% MT (90% MNS condition) were applied. PES was administered in a 4 s ON and 6 s OFF cycle for 20 min at 30 Hz. In Experiment 1 (n = 15), MEPs were recorded from the right abductor pollicis brevis (APB) before (baseline) and after PES. In Experiment 2 (n = 15), M- and F-waves were recorded from the right APB. Stimulation at 110% MNS at the wrist evoking muscle contraction increased MEP amplitudes after PES compared with those at baseline, whereas DNS at the index finger and 90% MNS at the wrist not evoking muscle contraction decreased MEP amplitudes after PES. M- and F-waves, which reflect spinal cord or muscular and neuromuscular junctions, did not change following PES. These results suggest that muscle contraction and concomitant muscle/joint afferent inputs specifically enhance M1 excitability. PMID:28392766

  3. Pre-operative inspiratory muscle training preserves postoperative inspiratory muscle strength following major abdominal surgery - a randomised pilot study.

    PubMed

    Kulkarni, S R; Fletcher, E; McConnell, A K; Poskitt, K R; Whyman, M R

    2010-11-01

    The aim of this pilot study was to assess the effect of pre-operative inspiratory muscle training (IMT) on respiratory variables in patients undergoing major abdominal surgery. Respiratory muscle strength (maximum inspiratory [MIP] and expiratory [MEP] mouth pressure) and pulmonary functions were measured at least 2 weeks before surgery in 80 patients awaiting major abdominal surgery. Patients were then allocated randomly to one of four groups (Group A, control; Group B, deep breathing exercises; Group C, incentive spirometry; Group D, specific IMT). Patients in groups B, C and D were asked to train twice daily, each session lasting 15 min, for at least 2 weeks up to the day before surgery. Outcome measurements were made immediately pre-operatively and postoperatively. In groups A, B and C, MIP did not increase from baseline to pre-operative assessments. In group D, MIP increased from 51.5 cmH(2)O (median) pre-training to 68.5 cmH(2)O (median) post-training pre-operatively (P < 0.01). Postoperatively, groups A, B and C showed a fall in MIP from baseline (P < 0.01, P < 0.01) and P = 0.06, respectively). No such significant reduction in postoperative MIP was seen in group D (P = 0.36). Pre-operative specific IMT improves MIP pre-operatively and preserves it postoperatively. Further studies are required to establish if this is associated with reduced pulmonary complications.

  4. Abdominal rectus muscle atrophy and midline shift after colostomy creation.

    PubMed

    Timmermans, Lucas; Deerenberg, Eva B; van Dijk, Sven M; Lamme, Bas; Koning, Anton H; Kleinrensink, Gert-Jan; Jeekel, Johannes; Lange, Johan F

    2014-04-01

    Incisional hernia (IH) can be attributed to multiple factors. The presence of a parastomal hernia has shown to be a risk factor for IH after midline laparotomy. Our hypothesis is that this increased risk of IH may be caused by changes in biomechanical forces, such as midline shift to the contralateral side of the colostomy owing to decreased restraining forces at the site of the colostomy, and left abdominal rectus muscle (ARM) atrophy owing to intercostal nerve damage. Patients were selected if they underwent end-colostomy via open operation between 2004 and 2011. Patients were eligible if computed tomography (CT) had been performed postoperatively. If available, preoperative CTs were collected for case-control analyses. Midline shift was measured using V-scope application in the I-space, a CAVE-like virtual reality system. For the ARM atrophy hypothesis, measurements of ARM were performed at the level of colostomy, and 3 and 8 cm cranial and caudal of the colostomy. Postoperative CT were available for 77 patients; of these patients, 30 also had a preoperative CT. Median follow-up was 19 months. A mean shift to the right side was identified after preoperative and postoperative comparison; from -1.3 ± 4.6 to 2.1 ± 9.3 (P = .043). Furthermore, during rectus muscle measurements, a thinner left ARM was observed below the level of colostomy. Creation of a colostomy alters the abdominal wall. Atrophy of the left ARM was seen caudal to the level of the colostomy, and a midline shift to the right side was evident on CT. These changes may explain the increased rate of IH after colostomy creation. Copyright © 2014 Mosby, Inc. All rights reserved.

  5. Mechanisms of Vascular Smooth Muscle Contraction and the Basis for Pharmacologic Treatment of Smooth Muscle Disorders

    PubMed Central

    Brozovich, F.V.; Nicholson, C.J.; Degen, C.V.; Gao, Yuan Z.; Aggarwal, M.

    2016-01-01

    The smooth muscle cell directly drives the contraction of the vascular wall and hence regulates the size of the blood vessel lumen. We review here the current understanding of the molecular mechanisms by which agonists, therapeutics, and diseases regulate contractility of the vascular smooth muscle cell and we place this within the context of whole body function. We also discuss the implications for personalized medicine and highlight specific potential target molecules that may provide opportunities for the future development of new therapeutics to regulate vascular function. PMID:27037223

  6. Contraction produced by intracellular injection of calcium, strontium, and barium in the single crayfish muscle fibers.

    PubMed

    Matsumura, M; Mashima, H

    1976-01-01

    Ca ions were ionophoretically injected through an intracellular microelectrode into the single muscle fiber of a crayfish, and the resulting contraction sphere was observed under a microscope and photographed with a movie camera. The minimum contraction produced by the threshold current involved usually three or four, sometimes two, sarcomers on both sides of the injecting pipette but contraction involving only one sarcomere was not observered. The rheobase of the Ca-injecting current was 3.2 X 10(-9) A. The strength-duration curves were determined for Ca-, Sr-, and Ba-injecting currents; all fitted a similar hyperbolic equation. The threshold amount of Ca above rheobasic injection was 2.1 X 10(-15)mol, and the ratios between threshold amounts were Ca: Sr: Ba=1: 1.9: 3.0. The effects of Ca and Sr were additive for the contraction. More current was required for the Ca-injection to produce the contraction in the K-depolarized-or 15mM-procaine-treated muscle, although less current was sufficient for the muscle treated with 0.5-1.0 mM of caffeine. The participation of the Ca-induced Ca release mechanism in the contraction produced by Ca injection and the role of Sr or Ba as a substitute for Ca were discussed.

  7. ( sup 3 H)QNB binding and contraction of rabbit colonic smooth muscle cells

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ringer, M.J.; Hyman, P.E.; Kao, H.W.

    The authors used radioligand binding and studies of cell contraction to characterize muscarinic receptors on dispersed smooth muscle cells from rabbit proximal and distal colon. Cells obtained after serial incubations in collagenase were used to measure binding of tritiated quinuclidinyl benzilate (({sup 3}H)QNB). At 37{degree}C, specific ({sup 3}H)QNB binding was saturable and linearly related to cell number. Nonlinear regression analysis was used to determine the affinity of ({sup 3}H)QNB for its receptor. The IC{sub 50} for the muscarinic agonists bethanechol and oxotremorine were 80 and 0.57 {mu}M, respectively. Hill coefficients were 0.67 for both, suggesting more complex interaction involving receptorsmore » of different affinities. In studies of cell contraction, bethanechol stimulated a dose-dependent decrease in cell length with half the maximal contraction occurring at 100 pM. These results suggest that (1) contraction is mediated by binding of bethanechol to M{sub 2}-muscarinic receptors and that (2) there are a large number of spare receptors in colonic smooth muscle.« less

  8. Mechanical load plays little role in contraction-mediated glucose transport in mouse skeletal muscle

    PubMed Central

    Sandström, Marie E; Zhang, Shi-Jin; Westerblad, Håkan; Katz, Abram

    2007-01-01

    The factors responsible for control of glucose transport during exercise are not fully understood. We investigated the role of mechanical load in contraction-mediated glucose transport in an isolated muscle preparation. Mouse extensor digitorum longus muscles were stimulated with repeated contractions for 10 min with or without N-benzyl-p-toluene sulphonamide (BTS, an inhibitor of myosin II ATPase) to block crossbridge activity. BTS inhibited force production during repeated contraction to ∼5% of control. In contrast, BTS had little effect on glucose transport in the basal state (control = 0.55 ± 0.04; BTS = 0.47 ± 0.09 μmol (20 min)−1 ml−1) or after contraction (control = 2.27 ± 0.15; BTS = 2.10 ± 0.16 μmol (20 min)−1 ml−1). BTS did not significantly alter the contraction-mediated changes in high-energy phosphates, glutathione status (a measure of oxidant status) or AMP-activated protein kinase activity. In conclusion, these data show that mechanical load plays little role in contraction-mediated glucose transport. Instead, it is likely that the increased glucose transport during contraction is a consequence of the increase in myoplasmic Ca2+ and the subsequent alterations in metabolism, e.g. increased energy turnover and production of reactive oxygen species. PMID:17185338

  9. Regulation of muscle contraction by Drebrin-like protein 1 probed by atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Garces, Renata; Butkevich, Eugenia; Platen, Mitja; Schmidt, Christoph F.; Biophysics Team

    Sarcomeres are the fundamental contractile units of striated muscle cells. They are composed of a variety of structural and regulatory proteins functioning in a precisely orchestrated fashion to enable coordinated force generation in striated muscles. Recently, we have identified a C. elegans drebrin-like protein 1 (DBN-1) as a novel sarcomere component, which stabilizes actin filaments during muscle contraction. To further characterize the function of DBN-1 in muscle cells, we generated a new dbn-1 loss-of-function allele. Absence of DBN-1 resulted in a unique worm movement phenotype, characterized by hyper-bending. It is not clear yet if DBN-1 acts to enhance or reduce the capacity for contraction. We present here an experimental mechanical study on C. elegans muscle mechanics. We measured the stiffness of the worm by indenting living C. eleganswith a micron-sized sphere adhered to the cantilever of an atomic force microscope (AFM). Modeling the worm as a pressurized elastic shell allows us to monitor the axial tension in the muscle through the measured stiffness. We compared responses of wild-type and mutant C. elegans in which DBN-1 is not expressed..

  10. Influence of clove oil and eugenol on muscle contraction of silkworm (Bombyx mori).

    PubMed

    Kheawfu, Kantaporn; Pikulkaew, Surachai; Hamamoto, Hiroshi; Sekimizu, Kazuhisa; Okonogi, Siriporn

    2017-05-30

    Clove oil is used in fish anesthesia and expected to have a mechanism via glutamic receptor. The present study explores the activities of clove oil and its major compound, eugenol, in comparison with L-glutamic acid on glutamic receptor of silkworm muscle and fish anesthesia. It was found that clove oil and eugenol had similar effects to L-glutamic acid on inhibition of silkworm muscle contraction after treated with D-glutamic acid and kainic acid. Anesthetic activity of the test samples was investigated in goldfish. The results demonstrated that L-glutamic acid at 20 and 40 mM could induce the fish to stage 3 of anesthesia that the fish exhibited total loss of equilibrium and muscle tone, whereas clove oil and eugenol at 60 ppm could induce the fish to stage 4 of anesthesia that the reflex activity of the fish was lost. These results suggest that clove oil and eugenol have similar functional activities and mechanism to L-glutamic acid on muscle contraction and fish anesthesia.

  11. Complete resection of a rectus abdominis muscle invaded by desmoid tumors and subsequent management with an abdominal binder: a case report.

    PubMed

    Ogawa, Tatsuhiko

    2018-02-07

    Desmoid-type fibromatosis is characterized by desmoid tumors, which are benign soft tissue tumors that can be locally aggressive but typically do not metastasize. Desmoid tumors can manifest anywhere in the body, and those in the abdominal cavity account for approximately 30 to 50% of all such tumors. Complete resection with free margins has been the standard treatment, but non-surgical therapies have been implemented recently. However, if tumors are strongly invasive and/or persistently recur, radical surgical resection with free margins remains the primary treatment. Unfortunately, radical resection may cause large abdominal defects and hinder reconstruction. Several reports and recommendations have addressed this issue; however, to the best of our knowledge, few reports have described complete resection and the subsequent reconstruction of the rectus abdominis muscle. A 35-year-old Asian woman presented at our hospital with a chief complaint of abdominal pain. She had abdominal desmoid tumors that required complete resection of her rectus abdominis muscle. Due to necrosis in her own reconstructed tissue, we failed to cover her anterior abdominal wall; thus, we used an abdominal binder as a substitute material to avoid exacerbating the incisional hernia and help her generate intra-abdominal pressure. This case report may be informative and helpful for the treatment of patients with desmoid tumors, as managing desmoid-type fibromatosis is difficult.

  12. Finite-element simulation of blood perfusion in muscle tissue during compression and sustained contraction.

    PubMed

    Vankan, W J; Huyghe, J M; Slaaf, D W; van Donkelaar, C C; Drost, M R; Janssen, J D; Huson, A

    1997-09-01

    Mechanical interaction between tissue stress and blood perfusion in skeletal muscles plays an important role in blood flow impediment during sustained contraction. The exact mechanism of this interaction is not clear, and experimental investigation of this mechanism is difficult. We developed a finite-element model of the mechanical behavior of blood-perfused muscle tissue, which accounts for mechanical blood-tissue interaction in maximally vasodilated vasculature. Verification of the model was performed by comparing finite-element results of blood pressure and flow with experimental measurements in a muscle that is subject to well-controlled mechanical loading conditions. In addition, we performed simulations of blood perfusion during tetanic, isometric contraction and maximal vasodilation in a simplified, two-dimensional finite-element model of a rat calf muscle. A vascular waterfall in the venous compartment was identified as the main cause for blood flow impediment both in the experiment and in the finite-element simulations. The validated finite-element model offers possibilities for detailed analysis of blood perfusion in three-dimensional muscle models under complicated loading conditions.

  13. Human skeletal muscle metabolic economy in vivo: effects of contraction intensity, age, and mobility impairment

    PubMed Central

    Christie, Anita D.; Tonson, Anne; Larsen, Ryan G.; DeBlois, Jacob P.

    2014-01-01

    We tested the hypothesis that older muscle has greater metabolic economy (ME) in vivo than young, in a manner dependent, in part, on contraction intensity. Twenty young (Y; 24 ± 1 yr, 10 women), 18 older healthy (O; 73 ± 2, 9 women) and 9 older individuals with mild-to-moderate mobility impairment (OI; 74 ± 1, 7 women) received stimulated twitches (2 Hz, 3 min) and performed nonfatiguing voluntary (20, 50, and 100% maximal; 12 s each) isometric dorsiflexion contractions. Torque-time integrals (TTI; Nm·s) were calculated and expressed relative to maximal fat-free muscle cross-sectional area (cm2), and torque variability during voluntary contractions was calculated as the coefficient of variation. Total ATP cost of contraction (mM) was determined from flux through the creatine kinase reaction, nonoxidative glycolysis and oxidative phosphorylation, and used to calculate ME (Nm·s·cm−2·mM ATP−1). While twitch torque relaxation was slower in O and OI compared with Y (P ≤ 0.001), twitch TTI, ATP cost, and economy were similar across groups (P ≥ 0.15), indicating comparable intrinsic muscle economy during electrically induced isometric contractions in vivo. During voluntary contractions, normalized TTI and total ATP cost did not differ significantly across groups (P ≥ 0.20). However, ME was lower in OI than Y or O at 20% and 50% MVC (P ≤ 0.02), and torque variability was greater in OI than Y or O at 20% MVC (P ≤ 0.05). These results refute the hypothesis of greater muscle ME in old age, and provide support for lower ME in impaired older adults as a potential mechanism or consequence of age-related reductions in functional mobility. PMID:25163917

  14. Changes in power and force generation during coupled eccentric-concentric versus concentric muscle contraction with training and aging.

    PubMed

    Caserotti, Paolo; Aagaard, Per; Puggaard, Lis

    2008-05-01

    Age-related decline in maximal concentric muscle power is associated with frailty and functional impairments in the elderly. Compared to concentric contraction, mechanical muscle output is generally enhanced when muscles are rapidly pre-stretched (eccentric contraction), albeit less pronounced with increasing age. Exercise has been recommended to prevent loss of muscle power and function and recent guidelines indicate training program for increasing muscle power highly relevant for elderly subjects. This study examined the differences in muscle power, force and movement pattern during concentric-alone and coupled eccentric-concentric contraction and selected functional motor performances before and after 36-week multicomponent training including aerobic, strength, balance, flexibility and coordination components in elderly males. Vertical force, excursion, velocity, power and acceleration of the body center of mass were measured in two standardised vertical jumps (squatting jump, SQJ; countermovement jump, CMJ). Pre-stretch enhancement during CMJ did not improve performance [i.e., no enhanced maximal muscle power (Ppeak) and jump height (JH)] compared to concentric-alone muscle contraction (SQJ). Nevertheless, pre-stretch enhancement occurred as for similar SQJ and CMJ maximal performance, elderly people employed lower mechanical work, higher mean muscle power (Pmean), shorter concentric phase duration and shorter body center of mass displacement during CMJ. Post training, CMJ Ppeak, Pmean and JH increased in training group (P<0.05) while Ppeak and JH decreased in control group during the CMJ and SQJ (P<0.05). In conclusion, long-term training counteracted the age-related decline in muscle power and functional performance observed in the control subjects, while substantial gains in muscular performance were observed in the trained elderly.

  15. A new method for the noninvasive determination of abdominal muscle feedforward activity based on tissue velocity information from tissue Doppler imaging.

    PubMed

    Mannion, A F; Pulkovski, N; Schenk, P; Hodges, P W; Gerber, H; Loupas, T; Gorelick, M; Sprott, H

    2008-04-01

    Rapid arm movements elicit anticipatory activation of the deep-lying abdominal muscles; this appears modified in back pain, but the invasive technique used for its assessment [fine-wire electromyography (EMG)] has precluded its widespread investigation. We examined whether tissue-velocity changes recorded with ultrasound (M-mode) tissue Doppler imaging (TDI) provided a viable noninvasive alternative. Fourteen healthy subjects rapidly flexed, extended, and abducted the shoulder; recordings were made of medial deltoid (MD) surface EMG and of fine-wire EMG and TDI tissue-velocity changes of the contralateral transversus abdominis, obliquus internus, and obliquus externus. Muscle onsets were determined by blinded visual analysis of EMG and TDI data. TDI could not distinguish between the relative activation of the three muscles, so in subsequent analyses only the onset of the earliest abdominal muscle activity was used. The latter occurred <50 ms after the onset of medial deltoid EMG (i.e., was feedforward) and correlated with the corresponding EMG onsets (r = 0.47, P < 0.0001). The mean difference between methods was 20 ms and was likely explained by electromechanical delay; limits of agreement were wide (-40 to +80 ms) but no greater than those typical of repeated measurements using either technique. The between-day standard error of measurement of the TDI onsets (examined in 16 further subjects) was 16 ms. TDI yielded reliable and valid measures of the earliest onset of feedforward activity within the anterolateral abdominal muscle group. The method can be used to assess muscle dysfunction in large groups of back-pain patients and may also be suitable for the noninvasive analysis of other deep-lying or small/thin muscles.

  16. Airway smooth muscle contraction - perspectives on past, present and future.

    PubMed

    Mitchell, H W

    2009-10-01

    Past and contemporary views of airway smooth muscle (ASM) have led to a high level of understanding of the control and intracellular regulation of force or shortening of ASM and of its possible role in airway disease. As well as the multitude of cellular mechanisms that regulate ASM contraction, a number of structural and mechanical factors, which are only present at the airway and lung level, provide overriding control over ASM. With new knowledge about the cellular physiology and biology of ASM, there is increasing need to understand how ASM contraction is regulated and expressed at these airway and system levels.

  17. Muscle contraction is required to maintain the pool of muscle progenitors via YAP and NOTCH during fetal myogenesis

    PubMed Central

    Esteves de Lima, Joana; Bonnin, Marie-Ange; Birchmeier, Carmen; Duprez, Delphine

    2016-01-01

    The importance of mechanical activity in the regulation of muscle progenitors during chick development has not been investigated. We show that immobilization decreases NOTCH activity and mimics a NOTCH loss-of-function phenotype, a reduction in the number of muscle progenitors and increased differentiation. Ligand-induced NOTCH activation prevents the reduction of muscle progenitors and the increase of differentiation upon immobilization. Inhibition of NOTCH ligand activity in muscle fibers suffices to reduce the progenitor pool. Furthermore, immobilization reduces the activity of the transcriptional co-activator YAP and the expression of the NOTCH ligand JAG2 in muscle fibers. YAP forced-activity in muscle fibers prevents the decrease of JAG2 expression and the number of PAX7+ cells in immobilization conditions. Our results identify a novel mechanism acting downstream of muscle contraction, where YAP activates JAG2 expression in muscle fibers, which in turn regulates the pool of fetal muscle progenitors via NOTCH in a non-cell-autonomous manner. DOI: http://dx.doi.org/10.7554/eLife.15593.001 PMID:27554485

  18. The influence of confounding factors on the relationship between muscle contraction level and MF and MPF values of EMG signal: a review.

    PubMed

    Roman-Liu, Danuta

    2016-01-01

    The purpose of this article is to gather results of studies on the relationship between median frequency (MF) and mean power frequency (MPF) and the level of muscle contraction, and to use those results to discuss the differences in the trends according to factors related to measurement technique and subject. Twenty-one studies with 63 cases for upper limb muscles and nine studies with 31 cases for lower limb muscles were analysed. Most results showed an increase in parameters with an increased level of muscle contraction, only some studies showed a decrease. The influence on parameters of the level of muscle contraction and factors such as subjects, type of contraction, muscle length and electrodes was analysed for each muscle. It was concluded that when analysing the influence of different factors on MF and MPF, because those factors interact they should be considered together, not separately.

  19. The influence of confounding factors on the relationship between muscle contraction level and MF and MPF values of EMG signal: a review

    PubMed Central

    Roman-Liu, Danuta

    2016-01-01

    The purpose of this article is to gather results of studies on the relationship between median frequency (MF) and mean power frequency (MPF) and the level of muscle contraction, and to use those results to discuss the differences in the trends according to factors related to measurement technique and subject. Twenty-one studies with 63 cases for upper limb muscles and nine studies with 31 cases for lower limb muscles were analysed. Most results showed an increase in parameters with an increased level of muscle contraction, only some studies showed a decrease. The influence on parameters of the level of muscle contraction and factors such as subjects, type of contraction, muscle length and electrodes was analysed for each muscle. It was concluded that when analysing the influence of different factors on MF and MPF, because those factors interact they should be considered together, not separately. PMID:26654476

  20. Recruitment of β-Catenin to N-Cadherin Is Necessary for Smooth Muscle Contraction*

    PubMed Central

    Wang, Tao; Wang, Ruping; Cleary, Rachel A.; Gannon, Olivia J.; Tang, Dale D.

    2015-01-01

    β-Catenin is a key component that connects transmembrane cadherin with the actin cytoskeleton at the cell-cell interface. However, the role of the β-catenin/cadherin interaction in smooth muscle has not been well characterized. Here stimulation with acetylcholine promoted the recruitment of β-catenin to N-cadherin in smooth muscle cells/tissues. Knockdown of β-catenin by lentivirus-mediated shRNA attenuated smooth muscle contraction. Nevertheless, myosin light chain phosphorylation at Ser-19 and actin polymerization in response to contractile activation were not reduced by β-catenin knockdown. In addition, the expression of the β-catenin armadillo domain disrupted the recruitment of β-catenin to N-cadherin. Force development, but not myosin light chain phosphorylation and actin polymerization, was reduced by the expression of the β-catenin armadillo domain. Furthermore, actin polymerization and microtubules have been implicated in intracellular trafficking. In this study, the treatment with the inhibitor latrunculin A diminished the interaction of β-catenin with N-cadherin in smooth muscle. In contrast, the exposure of smooth muscle to the microtubule depolymerizer nocodazole did not affect the protein-protein interaction. Together, these findings suggest that smooth muscle contraction is mediated by the recruitment of β-catenin to N-cadherin, which may facilitate intercellular mechanotransduction. The association of β-catenin with N-cadherin is regulated by actin polymerization during contractile activation. PMID:25713069

  1. The use of real-time ultrasound imaging for biofeedback of lumbar multifidus muscle contraction in healthy subjects.

    PubMed

    Van, Khai; Hides, Julie A; Richardson, Carolyn A

    2006-12-01

    Randomized controlled trial. To determine if the provision of visual biofeedback using real-time ultrasound imaging enhances the ability to activate the multifidus muscle. Increasingly clinicians are using real-time ultrasound as a form of biofeedback when re-educating muscle activation. The effectiveness of this form of biofeedback for the multifidus muscle has not been reported. Healthy subjects were randomly divided into groups that received different forms of biofeedback. All subjects received clinical instruction on how to activate the multifidus muscle isometrically prior to testing and verbal feedback regarding the amount of multifidus contraction, which occurred during 10 repetitions (acquisition phase). In addition, 1 group received visual biofeedback (watched the multifidus muscle contract) using real-time ultrasound imaging. All subjects were reassessed a week later (retention phase). Subjects from both groups improved their voluntary contraction of the multifidus muscle in the acquisition phase (P<.001) and the ability to recruit the multifidus muscle differed between groups (P<.05), with subjects in the group that received visual ultrasound biofeedback achieving greater improvements. In addition, the group that received visual ultrasound biofeedback retained their improvement in performance from week 1 to week 2 (P>.90), whereas the performance of the other group decreased (P<.05). Real-time ultrasound imaging can be used to provide visual biofeedback and improve performance and retention in the ability to activate the multifidus muscle in healthy subjects.

  2. On the mechanism of contraction and desensitization induced by substance P in the intestinal muscle of the guinea-pig.

    PubMed Central

    Holzer, P; Petsche, U

    1983-01-01

    The contractile effect of substance P on the longitudinal muscle of the isolated guinea-pig small intestine and the desensitization of the muscle which occurs on prolonged exposure to the peptide have been investigated. All experiments were performed in the presence of atropine. The response to a substance P concentration which produced a nearly maximal effect was not sustained but faded rapidly. It was found that not elimination of substance P from the bath, but desensitization of the muscle to substance P was the main cause for the fading of contraction. Desensitization of the muscle to substance P only developed if the muscle was exposed to the peptide for a certain time. The degree of and the time needed for recovery from desensitization were directly related to concentration of substance P and contact time. Tetraethylammonium (3 mM), which reduces the membrane conductance for K+, enhanced the potency of substance P in contracting the muscle and reduced the fading of contraction. Noradrenaline (295 nM), which increases the K+ conductance, produced opposite effects. Lowering the extracellular Ca2+ concentration to one-tenth decreased the potency of substance P in contracting the muscle, accelerated the fading of contraction, and reduced the ability of the muscle to respond to a second addition of substance P after the response to the first addition had faded away. Concentrations of substance P (22 nM) and tetraethylammonium (30 mM), which produced nearly maximal contractions, slightly enhanced the efflux of 86Rb from pre-loaded muscle strips. Both substances, however, caused a sustained reduction of 86Rb efflux from strips depolarized by high [K+], the effect of substance P being smaller than that of tetraethylammonium. The effect of substance P and tetraethylammonium on 86Rb efflux appeared independent of the extracellular [Ca2+]. On exposure of the muscle to substance P (22 nM) for 8 min the intracellular uptake of 45Ca was first decreased and then increased

  3. Suppression of Oxidative Stress by Resveratrol After Isometric Contractions in Gastrocnemius Muscles of Aged Mice

    PubMed Central

    Ryan, Michael J.; Jackson, Janna R.; Hao, Yanlei; Williamson, Courtney L.; Dabkowski, Erinne R.; Hollander, John M.

    2010-01-01

    This study tested the hypothesis that resveratrol supplementation would lower oxidative stress in exercised muscles of aged mice. Young (3 months) and aged (27 months) C57BL/6 mice received a control or a 0.05% trans-resveratrol-supplemented diet for 10 days. After 7 days of dietary intervention, 20 maximal electrically evoked isometric contractions were obtained from the plantar flexors of one limb in anesthetized mice. Exercise was conducted for three consecutive days. Resveratrol supplementation blunted the exercise-induced increase in xanthine oxidase activity in muscles from young (25%) and aged (53%) mice. Resveratrol lowered H2O2 levels in control (13%) and exercised (38%) muscles from aged animals, reduced Nox4 protein in both control and exercised muscles of young (30%) and aged mice (40%), and increased the ratio of reduced glutathione to oxidized glutathione in exercised muscles from young (38%) and aged (135%) mice. Resveratrol prevented the increase in lipid oxidation, increased catalase activity, and increased MnSOD activity in exercised muscles from aged mice. These data show that dietary resveratrol suppresses muscle indicators of oxidative stress in response to isometric contractions in aged mice. PMID:20507922

  4. Overexpression of antioxidant enzymes in diaphragm muscle does not alter contraction-induced fatigue or recovery

    PubMed Central

    McClung, Joseph M.; DeRuisseau, Keith C.; Whidden, Melissa A.; Van Remmen, Holly; Richardson, Arlan; Song, Wook; Vrabas, Ioannis S.; Powers, Scott K.

    2010-01-01

    Low levels of reactive oxygen species (ROS) production are necessary to optimize muscle force production in unfatigued muscle. In contrast, sustained high levels of ROS production have been linked to impaired muscle force production and contraction-induced skeletal muscle fatigue. Using genetically engineered mice, we tested the hypothesis that the independent transgenic overexpression of catalase (CAT), copper/zinc superoxide dismutase (CuZnSOD; SOD1) or manganese superoxide dismutase (MnSOD; SOD2) antioxidant enzymes would negatively affect force production in unfatigued diaphragm muscle but would delay the development of muscle fatigue and enhance force recovery after fatiguing contractions. Diaphragm muscle from wild-type littermates (WT) and from CAT, SOD1 and SOD2 overexpressing mice were subjected to an in vitro contractile protocol to investigate the force–frequency characteristics, the fatigue properties and the time course of recovery from fatigue. The CAT, SOD1 and SOD2 overexpressors produced less specific force (in N cm−2) at stimulation frequencies of 20–300 Hz and produced lower maximal tetanic force than WT littermates. The relative development of muscle fatigue and recovery from fatigue were not influenced by transgenic overexpression of any antioxidant enzyme. Morphologically, the mean cross-sectional area (in μm2) of diaphragm myofibres expressing myosin heavy chain type IIA was decreased in both CAT and SOD2 transgenic animals, and the percentage of non-contractile tissue increased in diaphragms from all transgenic mice. In conclusion, our results do not support the hypothesis that overexpression of independent antioxidant enzymes protects diaphragm muscle from contraction-induced fatigue or improves recovery from fatigue. Moreover, our data are consistent with the concept that a basal level of ROS is important to optimize muscle force production, since transgenic overexpression of major cellular antioxidants is associated with

  5. Continuous monitoring of sonomyography, electromyography and torque generated by normal upper arm muscles during isometric contraction: sonomyography assessment for arm muscles.

    PubMed

    Shi, Jun; Zheng, Yong-Ping; Huang, Qing-Hua; Chen, Xin

    2008-03-01

    The aim of this study is to demonstrate the feasibility of using the continuous signals about the thickness and pennation angle changes of muscles detected in real-time from ultrasound images, named as sonomyography (SMG), to characterize muscles under isometric contraction, along with synchronized surface electromyography (EMG) and generated torque signals. The right biceps brachii muscles of seven normal young adult subjects were tested. We observed that exponential functions could well represent the relationships between the normalized EMG root-mean-square (RMS) and the torque, the RMS and the muscle deformation SMG, and the RMS and the pennation angle SMG for the data of the contraction phase, with exponent coefficients of 0.0341 +/- 0.0148 (Mean SD), 0.0619 +/- 0.0273, and 0.0266 +/- 0.0076, respectively. In addition, the preliminary results also demonstrated linear relationships between the normalized torque and the muscle deformation as well as the pennation angle with the ratios of 9 .79 +/- 3.01 and 2.02 +/- 0.53, respectively. The overall mean R2 for the regressions was approximately 0.9 and the overall mean relative root mean square error (RRMSE) smaller than 15%. The potential values of SMG together with EMG to provide a more comprehensive assessment for the muscle functions should be further investigated with more subjects and more muscle groups.

  6. Skeletal muscle PLIN proteins, ATGL and CGI-58, interactions at rest and following stimulated contraction

    PubMed Central

    Ramos, Sofhia V.; Vandenboom, Rene; Roy, Brian D.; Peters, Sandra J.

    2013-01-01

    Evidence indicates that skeletal muscle lipid droplet-associated proteins (PLINs) regulate lipolysis through protein-protein interactions on the lipid droplet surface. In adipocytes, PLIN1 is thought to regulate lipolysis by directly interacting with comparative gene identification-58 (CGI-58), an activator of adipose triglyceride lipase (ATGL). Upon lipolytic stimulation, PLIN1 is phosphorylated, releasing CGI-58 to fully activate ATGL and initiate triglyceride breakdown. The absence of PLIN1 in skeletal muscle leads us to believe that other PLIN family members undertake this role. Our purpose was to examine interactions between PLIN2, PLIN3, and PLIN5, with ATGL and its coactivator CGI-58 at rest and following contraction. Isolated rat solei were incubated for 30 min at rest or during 30 min of intermittent tetanic stimulation [150-ms volleys at 60 Hz with a train rate of 20 tetani/min (25°C)] to maximally stimulate intramuscular lipid breakdown. Results show that the interaction between ATGL and CGI-58 increased 128% following contraction (P = 0.041). Further, ATGL interacts with PLIN2, PLIN3, and PLIN5 at rest and following contraction. The PLIN2-ATGL interaction decreased significantly by 21% following stimulation (P = 0.013). Both PLIN3 and PLIN5 coprecipitated with CGI-58 at rest and following contraction, while there was no detectable interaction between PLIN2 and CGI-58 in either condition. Therefore, our findings indicate that in skeletal muscle, during contraction-induced muscle lipolysis, ATGL and CGI-58 strongly associate and that the PLIN proteins work together to regulate lipolysis, in part, by preventing ATGL and CGI-58 interactions at rest. PMID:23408028

  7. The effect of temperature on basal tension and thyroarytenoid muscle contraction in an isolated rat glottis model.

    PubMed

    Wang, Hsing-Won; Chu, Yueng-Hsiang; Chao, Pin-Zhir; Lee, Fei-Peng

    2014-10-01

    The pitch of voice is closely related to the vocal fold tension, which is the end result of coordinated movement of the intralaryngeal muscles, and especially the thyroarytenoid muscle. It is known that vocal quality may be affected by surrounding temperature; however, the effect of temperature on vocal fold tension is mostly unknown. Thus, the aim of this study was to evaluate the effect of temperature on isolated rat glottis and thyroarytenoid muscle contraction induced by electrical field stimulation. In vitro isometric tension of the glottis ring from 30 Sprague-Dawley rats was continuously recorded by the tissue bath method. Electrical field stimulation was applied to the glottis ring with two wire electrodes placed parallel to the glottis and connected to a direct-current stimulator. The tension changes of the rat glottis rings that were either untreated or treated with electrical field stimulation were recorded continuously at temperatures from 37 to 7 °C or from 7 to 37 °C. Warming from 7 to 37 °C increased the basal tension of the glottis rings and decreased the electrical field stimulation-induced glottis ring contraction, which was chiefly due to thyroarytenoid muscle contraction. In comparison, cooling from 37 to 7 °C decreased the basal tension and enhanced glottis ring contraction by electrical field stimulation. We concluded that warming increased the basal tension of the glottis in vitro and decreased the amplitude of electrical field stimulation-induced thyroarytenoid muscle contraction. Thus, vocal pitch and the fine tuning of vocal fold tension might be affected by temperature in vivo.

  8. Effect of knee joint angle on neuromuscular activation of the vastus intermedius muscle during isometric contraction.

    PubMed

    Watanabe, K; Akima, H

    2011-12-01

    The purpose of this study was to compare the relationship between surface electromyography (EMG) and knee joint angle of the vastus intermedius muscle (VI) with the synergistic muscles in the quadriceps femoris (QF) muscle group. Fourteen healthy men performed maximal voluntary contractions during isometric knee extension at four knee joint angles from 90°, 115°, 140°, and 165° (180° being full extension). During the contractions, surface EMG was recorded at four muscle components of the QF muscle group: the VI, vastus lateralis (VL), vastus medialis (VM), and rectus femoris (RF) muscles. The root mean square of the surface EMG at each knee joint angle was calculated and normalized by that at a knee joint angle of 90° for individual muscles. The normalized RMS of the VI muscle was significantly lower than those of the VL and RF muscles at the knee joint angles of 115° and 165° and those of the VL, VM, and RF muscles at the knee joint angle of 140° (P<0.05). The present results suggest that the neuromuscular activation of the VI muscle is regulated in a manner different from the alteration of the knee joint angle compared with other muscle components of the QF muscle group. © 2011 John Wiley & Sons A/S.

  9. Intracellular calcium movements during excitation–contraction coupling in mammalian slow-twitch and fast-twitch muscle fibers

    PubMed Central

    Hollingworth, Stephen

    2012-01-01

    In skeletal muscle fibers, action potentials elicit contractions by releasing calcium ions (Ca2+) from the sarcoplasmic reticulum. Experiments on individual mouse muscle fibers micro-injected with a rapidly responding fluorescent Ca2+ indicator dye reveal that the amount of Ca2+ released is three- to fourfold larger in fast-twitch fibers than in slow-twitch fibers, and the proportion of the released Ca2+ that binds to troponin to activate contraction is substantially smaller. PMID:22450485

  10. The Effects of Modified Wall Squat Exercises on Average Adults’ Deep Abdominal Muscle Thickness and Lumbar Stability

    PubMed Central

    Cho, Misuk

    2013-01-01

    [Purpose] The purpose of this study was to compare the effects of bridge exercises applying the abdominal drawing-in method and modified wall squat exercises on deep abdominal muscle thickness and lumbar stability. [Subjects] A total of 30 subjects were equally divided into an experimental group and a control group. [Methods] The experimental group completed modified wall squat exercises, and the control group performed bridge exercises. Both did so for 30 minutes three times per week over a six-week period. Both groups’ transversus abdominis (Tra), internal oblique (IO), and multifidus muscle thickness were measured using ultrasonography, while their static lumbar stability and dynamic lumbar stability were measured using a pressure biofeedback unit. [Results] A comparison of the pre-intervention and post-intervention measures of the experimental group and the control group was made; the Tra and IO thicknesses were significantly different in both groups. [Conclusion] The modified wall squat exercise and bridge exercise affected the thicknesses of the Tra and the IO muscles. While the bridge exercise requirs space and a mattress to lie on, the modified wall squat exercise can be conveniently performed anytime. PMID:24259831

  11. Propofol preferentially relaxes neurokinin receptor-2-induced airway smooth muscle contraction in guinea pig trachea.

    PubMed

    Gleason, Neil R; Gallos, George; Zhang, Yi; Emala, Charles W

    2010-06-01

    Propofol is the anesthetic of choice for patients with reactive airway disease and is thought to reduce intubation- or irritant-induced bronchoconstriction by decreasing the cholinergic component of vagal nerve activation. However, additional neurotransmitters, including neurokinins, play a role in irritant-induced bronchoconstriction. We questioned the mechanistic assumption that the clinically recognized protective effect of propofol against irritant-induced bronchoconstriction during intubation was due to attenuation of airway cholinergic reflexes. Muscle force was continuously recorded from isolated guinea pig tracheal rings in organ baths. Rings were subjected to exogenous contractile agonists (acetylcholine, histamine, endothelin-1, substance P, acetyl-substance P, and neurokinin A) or to electrical field stimulation (EFS) to differentiate cholinergic or nonadrenergic, noncholinergic nerve-mediated contraction with or without cumulatively increasing concentrations of propofol, thiopental, etomidate, or ketamine. Propofol did not attenuate the cholinergic component of EFS-induced contraction at clinically relevant concentrations. In contrast, propofol relaxed nonadrenergic, noncholinergic-mediated EFS contraction at concentrations within the clinical range (20-100 mum, n = 9; P < 0.05), and propofol was more potent against an exogenous selective neurokinin-2 receptor versus neurokinin-1 receptor agonist contraction (n = 6, P < 0.001). Propofol, at clinically relevant concentrations, relaxes airway smooth muscle contracted by nonadrenergic, noncholinergic-mediated EFS and exogenous neurokinins but not contractions elicited by the cholinergic component of EFS. These findings suggest that the mechanism of protective effects of propofol against irritant-induced bronchoconstriction involves attenuation of tachykinins released from nonadrenergic, noncholinergic nerves acting at neurokinin-2 receptors on airway smooth muscle.

  12. Motor Unit Activity during Fatiguing Isometric Muscle Contraction in Hemispheric Stroke Survivors

    PubMed Central

    McManus, Lara; Hu, Xiaogang; Rymer, William Z.; Suresh, Nina L.; Lowery, Madeleine M.

    2017-01-01

    Enhanced muscle weakness is commonly experienced following stroke and may be accompanied by increased susceptibility to fatigue. To examine the contributions of central and peripheral factors to isometric muscle fatigue in stroke survivors, this study investigates changes in motor unit (MU) mean firing rate, and action potential duration during, and directly following, a sustained submaximal fatiguing contraction at 30% maximum voluntary contraction (MVC). A series of short contractions of the first dorsal interosseous muscle were performed pre- and post-fatigue at 20% MVC, and again following a 10-min recovery period, by 12 chronic stroke survivors. Individual MU firing times were extracted using surface EMG decomposition and used to obtain the spike-triggered average MU action potential waveforms. During the sustained fatiguing contraction, the mean rate of change in firing rate across all detected MUs was greater on the affected side (-0.02 ± 0.03 Hz/s) than on the less-affected side (-0.004 ± 0.003 Hz/s, p = 0.045). The change in firing rate immediately post-fatigue was also greater on the affected side than less-affected side (-13.5 ± 20 and 0.1 ± 19%, p = 0.04). Mean MU firing rates increased following the recovery period on the less-affected side when compared to the affected side (19.3 ± 17 and 0.5 ± 20%, respectively, p = 0.03). MU action potential duration increased post-fatigue on both sides (10.3 ± 1.2 to 11.2 ± 1.3 ms on the affected side and 9.9 ± 1.7 to 11.2 ± 1.9 ms on the less-affected side, p = 0.001 and p = 0.02, respectively), and changes in action potential duration tended to be smaller in subjects with greater impairment (p = 0.04). This study presents evidence of both central and peripheral fatigue at the MU level during isometric fatiguing contraction for the first time in stroke survivors. Together, these preliminary observations indicate that the response to an isometric fatiguing contraction differs between the affected and less

  13. Anisotropy of human muscle via non invasive impedance measurements. Frequency dependence of the impedance changes during isometric contractions

    NASA Astrophysics Data System (ADS)

    Kashuri, Hektor

    In this thesis we present non invasive muscle impedance measurements using rotatable probes extending the work done by Aaron et al. (1997) by measuring not only the real part of the impedance but the imaginary part as well. The results reveal orientations of underlying muscle fibers via minima in resistance and reactance versus angle curves, suggesting this method as potentially useful for studying muscle properties in clinical and physiological research. Calculations of the current distribution for a slab of material with anisotropic conductivity show that the current distribution depends strongly on the separation of two current electrodes and as well as on its conducting anisotropy. Forearm muscle impedance measurements at 50 kHz done by Shiffman et al. (2003) had shown that both resistance (R) and reactance (X) increase during isometric contraction. We have extended these measurements in the 3 to 100 kHz range and we found that resistance (R) and reactance (X) both increase and their changes increased or decreased at frequency dependent rates. Analysis based on circuit models of changes in R and X during the short contraction pulses showed that the extra cellular fluid resistance increased by 3.9 +/- 1.4 %, while the capacitance increased by 5.6 +/- 2 %. For long contraction pulses at very low frequencies: (1) there was practically no change in R during contraction, which implies that these changes are due to cellular membrane or intracellular effects with the extra cellular water component not participating, and (2) in post contraction stage there were no morphological changes which means that drifts in R can only be due to physiological changes. Following Shiffman et al. (2003) we measured impedance changes of R and X during a triangular shaped pulse of force generated via isometric forearm muscle contraction at 50 kHz. We measured these changes in 3-100 kHz frequency range for a stair case pulse of forces and the results showed that they are frequency

  14. Activity of LKB1 and AMPK-related kinases in skeletal muscle: effects of contraction, phenformin, and AICAR.

    PubMed

    Sakamoto, Kei; Göransson, Olga; Hardie, D Grahame; Alessi, Dario R

    2004-08-01

    Activation of AMP-activated protein kinase (AMPK) by exercise and metformin is beneficial for the treatment of type 2 diabetes. We recently found that, in cultured cells, the LKB1 tumor suppressor protein kinase activates AMPK in response to the metformin analog phenformin and the AMP mimetic drug 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR). We have also reported that LKB1 activates 11 other AMPK-related kinases. The activity of LKB1 or the AMPK-related kinases has not previously been studied in a tissue with physiological relevance to diabetes. In this study, we have investigated whether contraction, phenformin, and AICAR influence LKB1 and AMPK-related kinase activity in rat skeletal muscle. Contraction in situ, induced via sciatic nerve stimulation, significantly increased AMPKalpha2 activity and phosphorylation in multiple muscle fiber types without affecting LKB1 activity. Treatment of isolated skeletal muscle with phenformin or AICAR stimulated the phosphorylation and activation of AMPKalpha1 and AMPKalpha2 without altering LKB1 activity. Contraction, phenformin, or AICAR did not significantly increase activities or expression of the AMPK-related kinases QSK, QIK, MARK2/3, and MARK4 in skeletal muscle. The results of this study suggest that muscle contraction, phenformin, or AICAR activates AMPK by a mechanism that does not involve direct activation of LKB1. They also suggest that the effects of excercise, phenformin, and AICAR on metabolic processes in muscle may be mediated through activation of AMPK rather than activation of LKB1 or the AMPK-related kinases.

  15. Alcohol impairs skeletal muscle protein synthesis and mTOR signaling in a time-dependent manner following electrically stimulated muscle contraction

    PubMed Central

    Lang, Charles H.

    2014-01-01

    Alcohol (EtOH) decreases protein synthesis and mammalian target of rapamycin (mTOR)-mediated signaling and blunts the anabolic response to growth factors in skeletal muscle. The purpose of the current investigation was to determine whether acute EtOH intoxication antagonizes the contraction-induced increase in protein synthesis and mTOR signaling in skeletal muscle. Fasted male mice were injected intraperitoneally with 3 g/kg EtOH or saline (control), and the right hindlimb was electrically stimulated (10 sets of 6 contractions). The gastrocnemius muscle complex was collected 30 min, 4 h, or 12 h after stimulation. EtOH decreased in vivo basal protein synthesis (PS) in the nonstimulated muscle compared with time-matched Controls at 30 min, 4 h, and 12 h. In Control, but not EtOH, PS was decreased 15% after 30 min. In contrast, PS was increased in Control 4 h poststimulation but remained unchanged in EtOH. Last, stimulation increased PS 10% in Control and EtOH at 12 h, even though the absolute rate remained reduced by EtOH. The stimulation-induced increase in the phosphorylation of S6K1 Thr421/Ser424 (20–52%), S6K1 Thr389 (45–57%), and its substrate rpS6 Ser240/244 (37–72%) was blunted by EtOH at 30 min, 4 h, and 12 h. Phosphorylation of 4E-BP1 Ser65 was also attenuated by EtOH (61%) at 4 h. Conversely, phosphorylation of extracellular signal-regulated kinase Thr202/Tyr204 was increased by stimulation in Control and EtOH mice at 30 min but only in Control at 4 h. Our data indicate that acute EtOH intoxication suppresses muscle protein synthesis for at least 12 h and greatly impairs contraction-induced changes in synthesis and mTOR signaling. PMID:25257868

  16. Adenosine A1 receptors link to smooth muscle contraction via CYP4a, PKC-α, and ERK1/2

    PubMed Central

    Kunduri, SS; Mustafa, SJ; Ponnoth, DS; Dick, GM; Nayeem, MA

    2013-01-01

    Adenosine A1 receptor (A1AR) activation contracts smooth muscle, although signaling mechanisms aren’t thoroughly understood. Activation of A1AR leads to metabolism of arachidonic acid, including the production of 20-hydroxyeicosatetraenoic acid (20-HETE) by cytochrome P4504a (CYP4a). 20-HETE can activate protein kinase C-α (PKC-α) which crosstalks with extracellular signal-regulated kinase (ERK1/2) pathway. Both these pathways can regulate smooth muscle contraction, we tested the hypothesis that A1AR contracts smooth muscle through a pathway involving CYP4a, PKC-α, and ERK1/2. Experiments included isometric tension recordings of aortic contraction and Western blots of signaling molecules in wild type (WT) and A1AR knockout (A1KO) mice. Contraction to the A1-selective agonist CCPA was absent in A1KO mice aortae, indicating the contractile role of A1AR. Inhibition of CYP4a (HET0016) abolished CCPA-induced contraction in WT aortae, indicating a critical role for 20-HETE. Both WT and A1KO mice aortae contracted in response to exogenous 20-HETE. Inhibition of PKC-α (Gö6976) or ERK1/2 (PD98059) attenuated 20-HETE-induced contraction equally, suggesting that ERK1/2 is downstream of PKC-α. Contractions to exogenous 20-HETE were significantly less in A1KO mice; reduced protein levels of PKC-α, p-ERK1/2, and total ERK1/2 supported this observation. Our data indicate that A1AR mediates smooth muscle contraction via CYP4a and a PKC-α-ERK1/2 pathway. PMID:23519140

  17. Effects of hand configuration on muscle force coordination, co-contraction and concomitant intermuscular coupling during maximal isometric flexion of the fingers.

    PubMed

    Charissou, Camille; Amarantini, David; Baurès, Robin; Berton, Eric; Vigouroux, Laurent

    2017-11-01

    The mechanisms governing the control of musculoskeletal redundancy remain to be fully understood. The hand is highly redundant, and shows different functional role of extensors according to its configuration for a same functional task of finger flexion. Through intermuscular coherence analysis combined with hand musculoskeletal modelling during maximal isometric hand contractions, our aim was to better understand the neural mechanisms underlying the control of muscle force coordination and agonist-antagonist co-contraction. Thirteen participants performed maximal isometric flexions of the fingers in two configurations: power grip (Power) and finger-pressing on a surface (Press). Hand kinematics and force/moment measurements were used as inputs in a musculoskeletal model of the hand to determine muscular tensions and co-contraction. EMG-EMG coherence analysis was performed between wrist and finger flexors and extensor muscle pairs in alpha, beta and gamma frequency bands. Concomitantly with tailored muscle force coordination and increased co-contraction between Press and Power (mean difference: 48.08%; p < 0.05), our results showed muscle-pair-specific modulation of intermuscular coupling, characterized by pair-specific modulation of EMG-EMG coherence between Power and Press (p < 0.05), and a negative linear association between co-contraction and intermuscular coupling for the ECR/FCR agonist-antagonist muscle pair (r = - 0.65; p < 0.05). This study brings new evidence that pair-specific modulation of EMG-EMG coherence is related to modulation of muscle force coordination during hand contractions. Our results highlight the functional importance of intermuscular coupling as a mechanism contributing to the control of muscle force synergies and agonist-antagonist co-contraction.

  18. Electromyographic analysis of a modified maneuver for quadriceps femoris muscle setting with co-contraction of the hamstrings.

    PubMed

    Nakajima, Masaaki; Kawamura, Kenji; Takeda, Isao

    2003-05-01

    A "quadriceps femoris muscle setting" is isometric quadriceps femoris exercise which can be widely used in early knee rehabilitation. However this exercise cannot obtain enough co-contraction of the hamstrings. Isolated quadriceps femoris contraction in knee extension imposes severe strain to anterior cruciate ligament. We succeeded in developing a simple training maneuver that is effective in obtaining co-contraction of the hamstrings--a modified maneuver for the quadriceps femoris muscle setting with the contralateral lower limb raised (MQS). In this study, we analyzed the effect of this maneuver by EMG quantification. Twenty-eight healthy young adult men performed sequential trials consisting of normal quadriceps femoris muscle setting (NQS) and MQS. Electromyographic activity was recorded from surface electrodes on the gluteus maximus, vastus medialis, rectus femoris, vastus lateralis, semitendinosus and biceps femoris (long head), and normalized to values derived from maximal isometric trials. The % maximal voluntary isometric contraction (%MVIC) of the vastus medialis, vastus lateralis and rectus femoris did not vary in the each maneuver. However, the %MVIC of the hamstrings varied significantly in the MQS. This study suggests that effective co-contraction of the hamstrings can be obtained in MQS by adjusting the load to the raised lower limb.

  19. Inhibition of agonist-induced smooth muscle contraction by picotamide in the male human lower urinary tract outflow region.

    PubMed

    Hennenberg, Martin; Tamalunas, Alexander; Wang, Yiming; Keller, Patrick; Schott, Melanie; Strittmatter, Frank; Herlemann, Annika; Yu, Qingfeng; Rutz, Beata; Ciotkowska, Anna; Stief, Christian G; Gratzke, Christian

    2017-05-15

    Male lower urinary tract symptoms (LUTS) due to bladder outlet obstruction are characterized by abnormal smooth muscle contractions in the lower urinary tract. Alpha 1 -adrenoceptor antagonists may induce smooth muscle relaxation in the outflow region and represent the current gold standard of medical treatment. However, results may be unsatisfactory or inadequate. Apart from α 1 -adrenoceptor agonists, smooth muscle contraction in the outflow region may be induced by thromboxane A 2 (TXA 2 ), endothelins, or muscarinic receptor agonists. Here, we studied effects of the thromboxane A 2 receptor (TP receptor) antagonist picotamide on contraction in the human male bladder trigone and prostate. Carbachol, the α 1 -adrenoceptor agonist phenylephrine, the thromboxane A 2 analog U46619, and electric field stimulation (EFS) induced concentration- or frequency-dependent contractions of trigone tissues in an organ bath. Picotamide (300µM) inhibited carbachol-, phenylephrine-, U46619-, and EFS-induced contractions. Endothelins 1-3 induced concentration-dependent contractions of prostate tissues, which were inhibited by picotamide. Analyses using real time polymerase chain reaction and antibodies suggested expression of thromboxane A 2 receptors and synthase in trigone smooth muscle cells. Thromboxane B 2 (the stable metabolite of thromboxane A 2 ) was detectable by enzyme immune assay in trigone samples, with most values ranging between 50 and 150pg/mg trigone protein. Picotamide inhibits contractions induced by different stimuli in the human lower urinary tract, including cholinergic, adrenergic, thromboxane A 2 - and endothelin-induced, and neurogenic contractions in different locations of the outflow region. This distinguishes picotamide from current medical treatments for LUTS, and suggests that picotamide may induce urodynamic effects in vivo. Copyright © 2017. Published by Elsevier B.V.

  20. Oxidative stress exaggerates skeletal muscle contraction-evoked reflex sympathoexcitation in rats with hypertension induced by angiotensin II.

    PubMed

    Koba, Satoshi; Watanabe, Ryosuke; Kano, Naoko; Watanabe, Tatsuo

    2013-01-01

    Muscle contraction stimulates thin fiber muscle afferents and evokes reflex sympathoexcitation. In hypertension, this reflex is exaggerated. ANG II, which is elevated in hypertension, has been reported to trigger the production of superoxide and other reactive oxygen species. In the present study, we tested the hypothesis that increased ANG II in hypertension exaggerates skeletal muscle contraction-evoked reflex sympathoexcitation by inducing oxidative stress in the muscle. In rats, subcutaneous infusion of ANG II at 450 ng·kg(-1)·min(-1) for 14 days significantly (P < 0.05) elevated blood pressure compared with sham-operated (sham) rats. Electrically induced 30-s hindlimb muscle contraction in decerebrate rats with hypertension evoked larger renal sympathoexcitatory and pressor responses [+1,173 ± 212 arbitrary units (AU) and +35 ± 5 mmHg, n = 10] compared with sham normotensive rats (+419 ± 103 AU and +13 ± 2 mmHg, n = 11). Tempol, a SOD mimetic, injected intra-arterially into the hindlimb circulation significantly reduced responses in hypertensive rats, whereas this compound had no effect on responses in sham rats. Tiron, another SOD mimetic, also significantly reduced reflex renal sympathetic and pressor responses in a subset of hypertensive rats (n = 10). Generation of muscle superoxide, as evaluated by dihydroethidium staining, was increased in hypertensive rats. RT-PCR and immunoblot experiments showed that mRNA and protein for gp91(phox), a NADPH oxidase subunit, in skeletal muscle tissue were upregulated in hypertensive rats. Taken together, hese results suggest that increased ANG II in hypertension induces oxidative stress in skeletal muscle, thereby exaggerating the muscle reflex.

  1. Sonomyography Analysis on Thickness of Skeletal Muscle During Dynamic Contraction Induced by Neuromuscular Electrical Stimulation: A Pilot Study.

    PubMed

    Qiu, Shuang; Feng, Jing; Xu, Jiapeng; Xu, Rui; Zhao, Xin; Zhou, Peng; Qi, Hongzhi; Zhang, Lixin; Ming, Dong

    2017-01-01

    Neuromuscular electrical stimulation (NMES) that stimulates skeletal muscles to induce contractions has been widely applied to restore functions of paralyzed muscles. However, the architectural changes of stimulated muscles induced by NMES are still not well understood. The present study applies sonomyography (SMG) to evaluate muscle architecture under NMES-induced and voluntary movements. The quadriceps muscles of seven healthy subjects were tested for eight cycles during an extension exercise of the knee joint with/without NMES, and SMG and the knee joint angle were recorded during the process of knee extension. A least squares support vector machine (LS-SVM) LS-SVM model was developed and trained using the data sets of six cycles collected under NMES, while the remaining data was used to test. Muscle thickness changes were extracted from ultrasound images and compared between NMES-induced and voluntary contractions, and LS-SVM was used to model a relationship between dynamical knee joint angles and SMG signals. Muscle thickness showed to be significantly correlated with joint angle in NMES-induced contractions, and a significant negative correlation was observed between Vastus intermedius (VI) thickness and rectus femoris (RF) thickness. In addition, there was a significant difference between voluntary and NMES-induced contractions . The LS-SVM model based on RF thickness and knee joint angle provided superior performance compared with the model based on VI thickness and knee joint angle or total thickness and knee joint angle. This suggests that a strong relation exists between the RF thickness and knee joint angle. These results provided direct evidence for the potential application of RF thickness in optimizing NMES system as well as measuring muscle state under NMES.

  2. The simultaneous collapse of both the swinging crossbridge theory of muscle contraction and the in vitro motility essays.

    PubMed

    Oplatka, A

    2005-12-16

    In the early seventies we discovered that isolated, active, myosin fragments can induce movement and tension generation by actin filaments in both in vitro and in vivo systems, employing a variety of techniques. It was not in line with the domineering swinging crossbridge theory of muscle contraction. We then proposed an hydrodynamic mechanism which explained our results and was applied to muscle contraction and to other biological engines. Our discovery has been ignored for a long time until the so-called "in vitro motility essays" appeared. By using this artifact--laden technique the mechanochemical reactivity of the active myosin fragments was re-discovered without giving us any credit. The essays gave continuously changing values for fundamental parameters of muscle contraction; the values were appreciably different in different laboratories and decreased in a continuous fashion in the hands of one scientist. By analyzing recent experiments which derived the rate of ATP hydrolysis of active muscles as function of the applied load I calculated the value of the sliding distance resulting from the breakdown of one ATP molecule by each of the myosin heads in contracting muscle. According to the contemporary theory this should be the same for all muscles under any environmental conditions and determined by length of the myosin head's neck. My examination led to the conclusion that the sliding distance varies from one muscle to another and with different temperatures for the same muscle. This again, contradicts the current theory and should give the final blow to both this theory and the "essays". Furthermore: it can be explained by a hydrodynamic mechanism such as that proposed by us more than 30 years ago.

  3. The change in spatial distribution of upper trapezius muscle activity is correlated to contraction duration.

    PubMed

    Farina, Dario; Leclerc, Frédéric; Arendt-Nielsen, Lars; Buttelli, Olivier; Madeleine, Pascal

    2008-02-01

    The aim of the study was to confirm the hypothesis that the longer a contraction is sustained, the larger are the changes in the spatial distribution of muscle activity. For this purpose, surface electromyographic (EMG) signals were recorded with a 13 x 5 grid of electrodes from the upper trapezius muscle of 11 healthy male subjects during static contractions with shoulders 90 degrees abducted until endurance. The entropy (degree of uniformity) and center of gravity of the EMG root mean square map were computed to assess spatial inhomogeneity in muscle activation and changes over time in EMG amplitude spatial distribution. At the endurance time, entropy decreased (mean+/-SD, percent change 2.0+/-1.6%; P<0.0001) and the center of gravity moved in the cranial direction (shift 11.2+/-6.1mm; P<0.0001) with respect to the beginning of the contraction. The shift in the center of gravity was positively correlated with endurance time (R(2)=0.46, P<0.05), thus subjects with larger shift in the activity map showed longer endurance time. The percent variation in average (over the grid) root mean square was positively correlated with the shift in the center of gravity (R(2)=0.51, P<0.05). Moreover, the shift in the center of gravity was negatively correlated to both initial and final (at the endurance) entropy (R(2)=0.54 and R(2)=0.56, respectively; P<0.01 in both cases), indicating that subjects with less uniform root mean square maps had larger shift of the center of gravity over time. The spatial changes in root mean square EMG were likely due to spatially-dependent changes in motor unit activation during the sustained contraction. It was concluded that the changes in spatial muscle activity distribution play a role in the ability to maintain a static contraction.

  4. Recruitment order of motor units in human vastus lateralis muscle is maintained during fatiguing contractions.

    PubMed

    Adam, Alexander; De Luca, Carlo J

    2003-11-01

    Motor-unit firing patterns were studied in the vastus lateralis muscle of five healthy young men [21.4 +/- 0.9 (SD) yr] during a series of isometric knee extensions performed to exhaustion. Each contraction was held at a constant torque level, set to 20% of the maximal voluntary contraction at the beginning of the experiment. Electromyographic signals, recorded via a quadrifilar fine wire electrode, were processed with the precision decomposition technique to identify the firing times of individual motor units. In repeat experiments, whole-muscle mechanical properties were measured during the fatigue protocol using electrical stimulation. The main findings were a monotonic decrease in the recruitment threshold of all motor units and the progressive recruitment of new units, all without a change of the recruitment order. Motor units from the same subject showed a similar time course of threshold decline, but this decline varied among subjects (mean threshold decrease ranged from 23 to 73%). The mean threshold decline was linearly correlated (R2 >or= 0.96) with a decline in the elicited peak tetanic torque. In summary, the maintenance of recruitment order during fatigue strongly supports the notion that the observed common recruitment adaptations were a direct consequence of an increased excitatory drive to the motor unit pool. It is suggested that the increased central drive was necessary to compensate for the loss in force output from motor units whose muscle fibers were actively contracting. We therefore conclude that the control scheme of motor-unit recruitment remains invariant during fatigue at least in relatively large muscles performing submaximal isometric contractions.

  5. Critical role of actin-associated proteins in smooth muscle contraction, cell proliferation, airway hyperresponsiveness and airway remodeling.

    PubMed

    Tang, Dale D

    2015-10-30

    Asthma is characterized by airway hyperresponsiveness and airway remodeling, which are largely attributed to increased airway smooth muscle contractility and cell proliferation. It is known that both chemical and mechanical stimulation regulates smooth muscle contraction. Recent studies suggest that contractile activation and mechanical stretch induce actin cytoskeletal remodeling in smooth muscle. However, the mechanisms that control actin cytoskeletal reorganization are not completely elucidated. This review summarizes our current understanding regarding how actin-associated proteins may regulate remodeling of the actin cytoskeleton in airway smooth muscle. In particular, there is accumulating evidence to suggest that Abelson tyrosine kinase (Abl) plays a critical role in regulating airway smooth muscle contraction and cell proliferation in vitro, and airway hyperresponsiveness and remodeling in vivo. These studies indicate that Abl may be a novel target for the development of new therapy to treat asthma.

  6. Electrical stimulation to the trigeminal proprioceptive fibres that innervate the mechanoreceptors in Müller's muscle induces involuntary reflex contraction of the frontalis muscles.

    PubMed

    Matsuo, Kiyoshi; Osada, Yoshiro; Ban, Ryokuya

    2013-02-01

    The levator and frontalis muscles lack interior muscle spindles, despite consisting of slow-twitch fibres that involuntarily sustain eyelid-opening and eyebrow-raising against gravity. To compensate for this anatomical defect, this study hypothetically proposes that initial voluntary contraction of the levator fast-twitch muscle fibres stretches the mechanoreceptors in Müller's muscle and evokes proprioception, which continuously induces reflex contraction of slow-twitch fibres of the levator and frontalis muscles. This study sought to determine whether unilateral transcutaneous electrical stimulation to the trigeminal proprioceptive fibres that innervate the mechanoreceptors in Müller's muscle could induce electromyographic responses in the frontalis muscles, with monitoring responses in the orbicularis oculi muscles. The study population included 27 normal subjects and 23 subjects with aponeurotic blepharoptosis, who displayed persistently raised eyebrows on primary gaze and light eyelid closure. The stimulation induced a short-latency response in the ipsilateral frontalis muscle of all subjects and long-latency responses in the bilateral frontalis muscles of normal subjects. However, it did not induce long-latency responses in the bilateral frontalis muscles of subjects with aponeurotic blepharoptosis. The orbicularis oculi muscles showed R1 and/or R2 responses. The stimulation might reach not only the proprioceptive fibres, but also other sensory fibres related to the blink or corneal reflex. The experimental system can provoke a monosynaptic short-latency response in the ipsilateral frontalis muscle, probably through the mesencephalic trigeminal proprioceptive neuron and the frontalis motor neuron, and polysynaptic long-latency responses in the bilateral frontalis muscles through an unknown pathway. The latter neural circuit appeared to be engaged by the circumstances of aponeurotic blepharoptosis.

  7. Physics of muscle contraction

    NASA Astrophysics Data System (ADS)

    Caruel, M.; Truskinovsky, L.

    2018-03-01

    In this paper we report, clarify and broaden various recent efforts to complement the chemistry-centered models of force generation in (skeletal) muscles by mechanics-centered models. The physical mechanisms of interest can be grouped into two classes: passive and active. The main passive effect is the fast force recovery which does not require the detachment of myosin cross-bridges from actin filaments and can operate without a specialized supply of metabolic fuel (ATP). In mechanical terms, it can be viewed as a collective folding-unfolding phenomenon in the system of interacting bi-stable units and modeled by near equilibrium Langevin dynamics. The active force generation mechanism operates at slow time scales, requires detachment and is crucially dependent on ATP hydrolysis. The underlying mechanical processes take place far from equilibrium and are represented by stochastic models with broken time reversal symmetry implying non-potentiality, correlated noise or multiple reservoirs. The modeling approaches reviewed in this paper deal with both active and passive processes and support from the mechanical perspective the biological point of view that phenomena involved in slow (active) and fast (passive) force generation are tightly intertwined. They reveal, however, that biochemical studies in solution, macroscopic physiological measurements and structural analysis do not provide by themselves all the necessary insights into the functioning of the organized contractile system. In particular, the reviewed body of work emphasizes the important role of long-range interactions and criticality in securing the targeted mechanical response in the physiological regime of isometric contractions. The importance of the purely mechanical micro-scale modeling is accentuated at the end of the paper where we address the puzzling issue of the stability of muscle response on the so called ‘descending limb’ of the isometric tetanus.

  8. Physics of muscle contraction.

    PubMed

    Caruel, M; Truskinovsky, L

    2018-03-01

    In this paper we report, clarify and broaden various recent efforts to complement the chemistry-centered models of force generation in (skeletal) muscles by mechanics-centered models. The physical mechanisms of interest can be grouped into two classes: passive and active. The main passive effect is the fast force recovery which does not require the detachment of myosin cross-bridges from actin filaments and can operate without a specialized supply of metabolic fuel (ATP). In mechanical terms, it can be viewed as a collective folding-unfolding phenomenon in the system of interacting bi-stable units and modeled by near equilibrium Langevin dynamics. The active force generation mechanism operates at slow time scales, requires detachment and is crucially dependent on ATP hydrolysis. The underlying mechanical processes take place far from equilibrium and are represented by stochastic models with broken time reversal symmetry implying non-potentiality, correlated noise or multiple reservoirs. The modeling approaches reviewed in this paper deal with both active and passive processes and support from the mechanical perspective the biological point of view that phenomena involved in slow (active) and fast (passive) force generation are tightly intertwined. They reveal, however, that biochemical studies in solution, macroscopic physiological measurements and structural analysis do not provide by themselves all the necessary insights into the functioning of the organized contractile system. In particular, the reviewed body of work emphasizes the important role of long-range interactions and criticality in securing the targeted mechanical response in the physiological regime of isometric contractions. The importance of the purely mechanical micro-scale modeling is accentuated at the end of the paper where we address the puzzling issue of the stability of muscle response on the so called 'descending limb' of the isometric tetanus.

  9. Mechanisms of neurokinin A- and substance P-induced contractions in rat detrusor smooth muscle in vitro.

    PubMed

    Quinn, Teresa; Collins, Colm; Baird, Alan W

    2004-09-01

    To investigate the mechanisms of neurokinin A- and substance P-induced contractions of rat urinary bladder smooth muscle, and to compare them with those of the muscarinic agonist carbachol. Rat urinary bladder strips were suspended under 1 g of tension in a physiological buffer at 37 degrees C, gassed with 95% O(2)/5% CO(2). Mechanical activity was recorded isometrically during exposure to neurokinin A and substance P. Both agents produced concentration-dependent contractions of smooth muscle strips which were unaffected by tetrodotoxin (1 micro mol/L), peptidase inhibitors (captopril, thiorphan and bestatin; 1 micro mol/L each) or piroxicam (10 micro mol/L). The rank order of potency of agonists was neurokinin A > substance P > carbachol. Contractile responses to neurokinin A and substance P, like the contractile responses to carbachol, were abolished in a nominally Ca(2+)-free medium and significantly reduced by nifedipine (1 micro mol/L). SKF-96365 (60 micro mol/L), an inhibitor of receptor-mediated Ca(2+) entry, abolished the nifedipine-resistant response to substance P and carbachol, and significantly attenuated the response to neurokinin A. Depleting intracellular Ca(2+) stores with thapsigargin (1 micro mol/L) significantly attenuated neurokinin A-induced contractions but had no effect on substance P- or carbachol- induced contractions. The Rho-kinase inhibitor, Y-27632 (10 micro mol/L), significantly reduced both phasic and tonic components of the contractile responses to neurokinin A, substance P and carbachol. The contractile responses induced by tachykinins in rat urinary bladder smooth muscle strips involve a direct action on smooth muscle and are not modulated by peptidases or prostanoids. Neurokinin A and substance P, like carbachol-induced contractions, depend on extracellular Ca(2+) influx largely through voltage-operated and partly through receptor-operated Ca(2+) channels. Intracellular Ca(2+) release contributes to the contractile response to

  10. Characterization of the EP receptor types that mediate longitudinal smooth muscle contraction of human colon, mouse colon and mouse ileum.

    PubMed

    Fairbrother, S E; Smith, J E; Borman, R A; Cox, H M

    2011-08-01

    Prostaglandin E(2) (PGE(2) ) is an inflammatory mediator implicated in several gastrointestinal pathologies that affect normal intestinal transit. The aim was to establish the contribution of the four EP receptor types (EP(1-4) ), in human colon, that mediate PGE(2) -induced longitudinal smooth muscle contraction. Changes in isometric muscle tension of human colon, mouse colon and mouse ileum were measured in organ baths in response to receptor-specific agonists and antagonists. In addition, lidocaine was used to block neurogenic activity to investigate whether EP receptors were pre- or post-junctional. PGE(2) contracted longitudinal muscle from human and mouse colon and mouse ileum. These contractions were inhibited by the EP(1) receptor antagonist, EP(1) A in human colon, whereas a combination of EP(1) A and the EP(3) antagonist, L798106 inhibited agonist responses in both mouse preparations. The EP(3) agonist, sulprostone also increased muscle tension in both mouse tissues, and these responses were inhibited by lidocaine in the colon but not in the ileum. Although PGE(2) consistently contracted all three muscle preparations, butaprost decreased tension by activating smooth muscle EP(2) receptors in both colonic tissues. Alternatively, in mouse ileum, butaprost responses were lidocaine-sensitive, suggesting that it was activating prejunctional EP(2) receptors on inhibitory motor neurons. Conversely, EP(4) receptors were not functional in all the intestinal muscle preparations tested. PGE(2) -induced contraction of longitudinal smooth muscle is mediated by EP(1) receptors in human colon and by a combination of EP(1) and EP(3) receptors in mouse intestine, whereas EP(2) receptors modulate relaxation in all three preparations. © 2011 Blackwell Publishing Ltd.

  11. Structural alterations of thin actin filaments in muscle contraction by synchrotron X-ray fiber diffraction.

    PubMed

    Wakabayashi, Katsuzo; Sugimoto, Yasunobu; Takezawa, Yasunori; Ueno, Yutaka; Minakata, Shiho; Oshima, Kanji; Matsuo, Tatsuhito; Kobayashi, Takakazu

    2007-01-01

    Strong evidence has been accumulated that the conformational changes of the thin actin filaments are occurring and playing an important role in the entire process of muscle contraction. The conformational changes and the mechanical properties of the thin actin filaments we have found by X-ray fiber diffraction on skeletal muscle contraction are explored. Recent studies on the conformational changes of regulatory proteins bound to actin filaments upon activation and in the force generation process are also described. Finally, the roles of structural alterations and dynamics of the actin filaments are discussed in conjunction with the regulation mechanism and the force generation mechanism.

  12. Muscle microanatomy and its changes during contraction: the legacy of William Bowman (1816-1892).

    PubMed

    Frixione, Eugenio

    2006-01-01

    Striated muscle fine structure began to be really understood following a comprehensive survey of the matter carried out by William Bowman in the late 1830s. The publications resulting from such a study, the first of which earned for the author a precocious election as Fellow of the Royal Society, are herewith examined in the context of contemporary views on the subject as well as of their subsequent repercussion and current knowledge today. It is shown that not only Bowman succeeded in establishing the true architecture of striated muscle fibres to the extent possible with the most advanced technology available in his day--explaining and eradicating alternative erroneous concepts in the process--but also in correctly describing the basic microstructural changes associated with contraction. In addition, although unrecognized by him or others at the time, his experiments with muscle provided direct evidence for the existence of a selectively permeable cell membrane--in the present meaning of the word--over half a century before its officially accepted discovery. Yet, in spite of these remarkable advances, Bowman arrived at the conclusion that the structure of striated muscle fibres is essentially irrelevant for the mechanism of contraction. Possible reasons behind Bowman's breakthrough accomplishments as a pioneer of modern muscle research, and his failure to understand their significance for muscle physiology, are discussed.

  13. Associations between low back pain, urinary incontinence, and abdominal muscle recruitment as assessed via ultrasonography in the elderly.

    PubMed

    Figueiredo, Vânia F; Amorim, Juleimar S C; Pereira, Aline M; Ferreira, Paulo H; Pereira, Leani S M

    2015-01-01

    Low back pain (LBP) and urinary incontinence (UI) are highly prevalent among elderly individuals. In young adults, changes in trunk muscle recruitment, as assessed via ultrasound imaging, may be associated with lumbar spine stability. To assess the associations between LBP, UI, and the pattern of transversus abdominis (TrA), internal (IO), and external oblique (EO) muscle recruitment in the elderly as evaluated by ultrasound imaging. Fifty-four elderly individuals (mean age: 72±5.2 years) who complained of LBP and/or UI as assessed by the McGill Pain Questionnaire, Incontinence Questionnaire-Short Form, and ultrasound imaging were included in the study. The statistical analysis comprised a multiple linear regression model, and a p-value <0.05 was considered significant. The regression models for the TrA, IO, and EO muscle thickness levels explained 2.0% (R2=0.02; F=0.47; p=0.628), 10.6% (R2=0.106; F=3.03; p=0.057), and 10.1% (R2=0.101; F=2.70; p=0.077) of the variability, respectively. None of the regression models developed for the abdominal muscles exhibited statistical significance. A significant and negative association (p=0.018; β=-0.0343) was observed only between UI and IO recruitment. These results suggest that age-related factors may have interfered with the findings of the study, thus emphasizing the need to perform ultrasound imaging-based studies to measure abdominal muscle recruitment in the elderly.

  14. Does the prevalence of levator ani muscle avulsion differ when assessed using tomographic ultrasound imaging at rest vs on maximum pelvic floor muscle contraction?

    PubMed

    van Delft, K; Thakar, R; Sultan, A H; Kluivers, K B

    2015-07-01

    It has been suggested that transperineal ultrasound images obtained during maximum pelvic floor muscle contraction improve the diagnosis of levator ani muscle (LAM) avulsion by comparison with those obtained at rest. The objective of this study was to establish, using transperineal tomographic ultrasound imaging (TUI), the correlation between LAM avulsion diagnosed at rest and that on contraction. Primiparous women were examined 3 months postpartum by Pelvic Organ Prolapse Quantification (POP-Q) assessment and for LAM avulsion clinically by digital palpation and by transperineal TUI performed at rest and on pelvic floor muscle contraction. LAM avulsion was diagnosed on TUI when the three central slices were abnormal. A comparison was made between LAM avulsion diagnosed at rest and on maximum contraction. Two independent blinded investigators performed the analyses and a third investigator resolved discrepancies. One hundred and ninety primiparae were analyzed providing 380 results for comparison, as right and left LAM were analyzed independently. LAM avulsion was found in 36 (9.5%) images obtained at rest and in 35 (9.2%) on contraction, revealing moderate correlation between the two (ICC, 0.58 (95% CI, 0.51-0.64)). Twenty-two cases of LAM avulsion were identified both at rest and on contraction. One woman had LAM avulsion on palpation, which was seen on TUI as LAM avulsion on contraction, but not at rest. More cases of anterior and posterior compartment prolapse were found in women with LAM avulsion diagnosed on contraction only compared to LAM avulsion observed at rest only (POP-Q assessment point Ba, -1.8 vs -2.5 (P = 0.075) and point Bp, -2.5 vs -2.8 (P = 0.072)). Findings on transperineal TUI performed in women at rest and on contraction correlate reasonably well. However, given the trend towards an association with signs of pelvic floor dysfunction, diagnosis of LAM avulsion on contraction seems to be more reliable. Consistency in technique and

  15. Desensitization of the Mechanoreceptors in Müller's Muscle Reduces the Increased Reflex Contraction of the Orbicularis Oculi Slow-Twitch Fibers in Blepharospasm.

    PubMed

    Matsuo, Kiyoshi; Ban, Ryokuya; Ban, Midori

    2014-01-01

    Although the mixed orbicularis oculi muscle lacks the muscle spindles required to induce reflex contraction of its slow-twitch fibers, the mechanoreceptors in Müller's muscle function as extrinsic mechanoreceptors to induce reflex contraction. We hypothesize that strong stretching of these mechanoreceptors increases reflex contraction of the orbicularis oculi slow-twitch muscle fibers, resulting in blepharospasm. We examined a 71-year-old man with right blepharospasm and bilateral aponeurosis-disinserted blepharoptosis to determine whether the patient's blepharospasm was worsened by increased trigeminal proprioceptive evocation via stretching of the mechanoreceptors in Müller's muscle owing to a 60° upward gaze and serrated eyelid closure, and whether local anesthesia of the mechanoreceptors via lidocaine administration to the upper fornix as well as surgical disinsertion of Müller's muscle from the tarsus and fixation of the disinserted aponeurosis to the tarsus decreased trigeminal proprioceptive evocation and improved patient's blepharospasm. Before pharmacological desensitization, 60° upward gaze and serrated eyelid closure exacerbated the patient's blepharospasm. In contrast, these maneuvers did not worsen his blepharospasm following lidocaine administration. One year after surgical desensitization, the blepharospasm had disappeared and a 60° upward gaze did not induce blepharospasm. Strong stretching of the mechanoreceptors in Müller's muscle appeared to increase reflex contraction of the orbicularis oculi slow-twitch muscle fibers, resulting in blepharospasm. In addition to botulinum neurotoxin injections into the involuntarily contracted orbicularis oculi muscle and myectomy, surgical desensitization of the mechanoreceptors in Müller's muscle may represent an additional procedure to reduce blepharospasm.

  16. Desensitization of the Mechanoreceptors in Müller's Muscle Reduces the Increased Reflex Contraction of the Orbicularis Oculi Slow-Twitch Fibers in Blepharospasm

    PubMed Central

    Ban, Ryokuya; Ban, Midori

    2014-01-01

    Objective: Although the mixed orbicularis oculi muscle lacks the muscle spindles required to induce reflex contraction of its slow-twitch fibers, the mechanoreceptors in Müller's muscle function as extrinsic mechanoreceptors to induce reflex contraction. We hypothesize that strong stretching of these mechanoreceptors increases reflex contraction of the orbicularis oculi slow-twitch muscle fibers, resulting in blepharospasm. Methods: We examined a 71-year-old man with right blepharospasm and bilateral aponeurosis-disinserted blepharoptosis to determine whether the patient's blepharospasm was worsened by increased trigeminal proprioceptive evocation via stretching of the mechanoreceptors in Müller's muscle owing to a 60° upward gaze and serrated eyelid closure, and whether local anesthesia of the mechanoreceptors via lidocaine administration to the upper fornix as well as surgical disinsertion of Müller's muscle from the tarsus and fixation of the disinserted aponeurosis to the tarsus decreased trigeminal proprioceptive evocation and improved patient's blepharospasm. Results: Before pharmacological desensitization, 60° upward gaze and serrated eyelid closure exacerbated the patient's blepharospasm. In contrast, these maneuvers did not worsen his blepharospasm following lidocaine administration. One year after surgical desensitization, the blepharospasm had disappeared and a 60° upward gaze did not induce blepharospasm. Conclusions: Strong stretching of the mechanoreceptors in Müller's muscle appeared to increase reflex contraction of the orbicularis oculi slow-twitch muscle fibers, resulting in blepharospasm. In addition to botulinum neurotoxin injections into the involuntarily contracted orbicularis oculi muscle and myectomy, surgical desensitization of the mechanoreceptors in Müller's muscle may represent an additional procedure to reduce blepharospasm. PMID:25328566

  17. Comparison of deep and superficial abdominal muscle activity between experienced Pilates and resistance exercise instructors and controls during stabilization exercise.

    PubMed

    Moon, Ji-Hyun; Hong, Sang-Min; Kim, Chang-Won; Shin, Yun-A

    2015-06-01

    Pilates and resistance exercises are used for lumbar stabilization training. However, it is unclear which exercise is more effective for lumbar stabilization. In our study, we aimed to compare surface muscle activity and deep muscle thickness during relaxation and spinal stabilization exercise in experienced Pilates and resistance exercise instructors. This study is a retrospective case control study set in the Exercise Prescription Laboratory and Sports Medicine Center. The participants included Pilates instructors (mean years of experience, 3.20±1.76; n=10), resistance exercise instructors (mean years of experience, 2.53±0.63; n=10), and controls (n=10). The participants performed 4 different stabilization exercises: abdominal drawing-in maneuver, bridging, roll-up, and one-leg raise. During the stabilization exercises, surface muscle activity was measured with electromyography, whereas deep muscle thickness was measured by ultrasound imaging. During the 4 stabilization exercises, the thickness of the transverse abdominis (TrA) was significantly greater in the Pilates-trained group than the other 2 other groups. The internal oblique (IO) thickness was significantly greater in the Pilates- and resistance-trained group than the control group, during the 4 exercises. However, the surface muscle activities were similar between the groups. Both Pilates and resistance exercise instructors had greater activation of deep muscles, such as the TrA and IO, than the control subjects. Pilates and resistance exercise are both effective for increasing abdominal deep muscle thickness.

  18. Comparison of deep and superficial abdominal muscle activity between experienced Pilates and resistance exercise instructors and controls during stabilization exercise

    PubMed Central

    Moon, Ji-Hyun; Hong, Sang-Min; Kim, Chang-Won; Shin, Yun-A

    2015-01-01

    Pilates and resistance exercises are used for lumbar stabilization training. However, it is unclear which exercise is more effective for lumbar stabilization. In our study, we aimed to compare surface muscle activity and deep muscle thickness during relaxation and spinal stabilization exercise in experienced Pilates and resistance exercise instructors. This study is a retrospective case control study set in the Exercise Prescription Laboratory and Sports Medicine Center. The participants included Pilates instructors (mean years of experience, 3.20±1.76; n=10), resistance exercise instructors (mean years of experience, 2.53±0.63; n=10), and controls (n=10). The participants performed 4 different stabilization exercises: abdominal drawing-in maneuver, bridging, roll-up, and one-leg raise. During the stabilization exercises, surface muscle activity was measured with electromyography, whereas deep muscle thickness was measured by ultrasound imaging. During the 4 stabilization exercises, the thickness of the transverse abdominis (TrA) was significantly greater in the Pilates-trained group than the other 2 other groups. The internal oblique (IO) thickness was significantly greater in the Pilates- and resistance-trained group than the control group, during the 4 exercises. However, the surface muscle activities were similar between the groups. Both Pilates and resistance exercise instructors had greater activation of deep muscles, such as the TrA and IO, than the control subjects. Pilates and resistance exercise are both effective for increasing abdominal deep muscle thickness. PMID:26171383

  19. Reperfusion response changes induced by repeated, sustained contractions in normal human masseter muscle.

    PubMed

    Aizawa, Shigeru; Tsukiyama, Yoshihiro; Koyano, Kiyoshi; Clark, Glenn T

    2002-07-01

    The purpose was to evaluate the intramuscular reperfusion response characteristics associated with repeated isometric contractions in normal human masseter. Intramuscular blood volume was quantified with a near-infrared spectroscopic device that measured the total haemoglobin (Hb) concentration in the muscle. Electromyographic (EMG) activity from the masseter and total bite forces were also recorded. Sixteen healthy volunteers, eight females and eight males, without masticatory muscle pain participated. They were asked first to clench their teeth for as long as possible at 50% of their maximum voluntary contraction (MVC). This was followed by a 60s rest and then immediately by a standard clenching task (50% MVC for 30s) and a 60s recovery period, immediately after which they were asked to repeat exactly the same procedure, with a final 5 min recovery period after the second 30s contraction. Bite force, EMG and Hb concentration were measured continuously and the duration of the two endurance tasks and the amplitudes of all recorded signals were compared (first trial versus second trial). Specifically, the difference between the lowest Hb (trough) seen during the standardised 30s contractions and the highest (peak) seen just after them was assessed. The trough-to-peak difference in Hb concentration of the second standard contraction task was significantly smaller than that of the first standard task (P<0.05, paired t-test). These data show that with sustained effort the post-contraction vasodilatory reperfusion responses of the human masseter are diminished, suggesting a progressive desensitisation of the vasodilatory system.

  20. Role of muscle mass and mode of contraction in circulatory responses to exercise

    NASA Technical Reports Server (NTRS)

    Lewis, S. F.; Snell, P. G.; Pettinger, W. A.; Blomqvist, C. G.; Taylor, W. F.; Hamra, M.; Graham, R. M.

    1985-01-01

    The roles of the mode of contraction (dynamic or static) and active muscle mass in determining the cardiovascular response to exercise has been investigated experimentally in six normal men. Exercise consisted of static handgrip and dynamic handgrip exercise, and static and dynamic knee extension for a period of six minutes. Observed increases in mean arterial pressure after exercise were similar for each mode of contraction, but larger for knee extension than handgrip exercise. Cardiac output increased more for dynamic than for static exercise and for each mode more for knee exercise than for handgrip exercise. Systemic resistance was found to be lower for dynamic than for static exercise, and to decrease from resisting levels by about one third during dynamic knee extension. It is shown that the magnitude of cardiovascular response is related to active muscle mass, but is independent of the contraction mode. Equalization of cardiovascular response was achieved by proportionately larger increases in cardiac output during dynamic exercise. The complete experimental results are given in a table.

  1. LPA1 receptor-mediated thromboxane A2 release is responsible for lysophosphatidic acid-induced vascular smooth muscle contraction.

    PubMed

    Dancs, Péter Tibor; Ruisanchez, Éva; Balogh, Andrea; Panta, Cecília Rita; Miklós, Zsuzsanna; Nüsing, Rolf M; Aoki, Junken; Chun, Jerold; Offermanns, Stefan; Tigyi, Gábor; Benyó, Zoltán

    2017-04-01

    Lysophosphatidic acid (LPA) has been recognized recently as an endothelium-dependent vasodilator, but several lines of evidence indicate that it may also stimulate vascular smooth muscle cells (VSMCs), thereby contributing to vasoregulation and remodeling. In the present study, mRNA expression of all 6 LPA receptor genes was detected in murine aortic VSMCs, with the highest levels of LPA 1 , LPA 2 , LPA 4 , and LPA 6 In endothelium-denuded thoracic aorta (TA) and abdominal aorta (AA) segments, 1-oleoyl-LPA and the LPA 1-3 agonist VPC31143 induced dose-dependent vasoconstriction. VPC31143-induced AA contraction was sensitive to pertussis toxin (PTX), the LPA 1&3 antagonist Ki16425, and genetic deletion of LPA 1 but not that of LPA 2 or inhibition of LPA 3 , by diacylglycerol pyrophosphate. Surprisingly, vasoconstriction was also diminished in vessels lacking cyclooxygenase-1 [COX1 knockout (KO)] or the thromboxane prostanoid (TP) receptor (TP KO). VPC31143 increased thromboxane A 2 (TXA 2 ) release from TA of wild-type, TP-KO, and LPA 2 -KO mice but not from LPA 1 -KO or COX1-KO mice, and PTX blocked this effect. Our findings indicate that LPA causes vasoconstriction in VSMCs, mediated by LPA 1 -, G i -, and COX1-dependent autocrine/paracrine TXA 2 release and consequent TP activation. We propose that this new-found interaction between the LPA/LPA 1 and TXA 2 /TP pathways plays significant roles in vasoregulation, hemostasis, thrombosis, and vascular remodeling.-Dancs, P. T., Ruisanchez, E., Balogh, A., Panta, C. R., Miklós, Z., Nüsing, R. M., Aoki, J., Chun, J., Offermanns, S., Tigyi, G., Benyó, Z. LPA 1 receptor-mediated thromboxane A 2 release is responsible for lysophosphatidic acid-induced vascular smooth muscle contraction. © FASEB.

  2. Gender influence on fatigability of back muscles during intermittent isometric contractions: a study of neuromuscular activation patterns.

    PubMed

    Larivière, Christian; Gravel, Denis; Gagnon, Denis; Gardiner, Phillip; Bertrand Arsenault, A; Gaudreault, Nathaly

    2006-11-01

    Gender difference in the fatigability of muscles can be attributed to muscle mass (or strength) and associated level of vascular occlusion, substrate utilization, muscle composition, and neuromuscular activation patterns. The purpose of this study was to assess the role of neuromuscular activation patterns to explain gender differences in back muscle fatigability during intermittent isometric tasks. Sixteen males and 15 females performed maximal voluntary contractions (Strength) and a fatigue test to exhaustion (fatigue criterion=time to exhaustion), while standing in a static dynamometer measuring L5/S1 extension moment. The fatigue test consisted of repetitions of an 8-s cycle (1.5 s ramp to reach 40% of maximal voluntary contraction +5s plateau at 40% of maximal voluntary contraction +1.5s rest). Surface electromyography signals were collected bilaterally from 4 back muscles (multifidus at the L5 level, iliocostalis lumborum at L3, and longissimus at L1 and T10). Males were stronger (P<0.05) than females (316, SD 82>196, SD 25 Nm) but showed significantly shorter time-to-exhaustion values (7.1, SD 5.2<13.0, SD 6.1 min.), the latter result being corroborated by electromyographic indices of fatigue. However, the gender effect on time to exhaustion disappeared when accounting for Strength, thus supporting the muscle mass hypothesis. Among the various electromyographic indices computed to assess neuromuscular activation patterns, the amount of alternating activity between homolateral and between contralateral muscles showed a gender effect (females>males). These results support the muscle mass hypothesis as well as the neuromuscular activation hypothesis to explain gender differences in back muscle fatigability.

  3. Sex differences in neuromuscular function after repeated eccentric contractions of the knee extensor muscles.

    PubMed

    Lee, Andrea; Baxter, Jake; Eischer, Claire; Gage, Matt; Hunter, Sandra; Yoon, Tejin

    2017-06-01

    This study examined the mechanisms for force and power reduction during and up to 48 h after maximal eccentric contractions of the knee extensor muscles in young men and women. 13 men (22.8 ± 2.6 years) and 13 women (21.6 ± 2.2 years) performed 150 maximal effort eccentric contractions (5 sets of 30) with the knee extensor muscles at 60° s -1 . Maximal voluntary isometric contractions (MVIC) and maximal voluntary concentric contractions (MVCC) were performed before and after the 150 eccentric contractions. The MVCCs involved a set of two isokinetic contractions at 60° s -1 and sets of isotonic contractions performed at seven different resistance loads (1 N m, 10, 20, 30, 40, 50, and 60% MVIC). Electrical stimulation was used during the MVICs and at rest to determine changes in voluntary activation and contractile properties. At baseline, men were stronger than women (MVIC: 276 ± 48 vs. 133 ± 37 N m) and more powerful (MVCC: 649 ± 77 vs. 346 ± 78 W). At termination of the eccentric contractions, voluntary activation, resting twitch amplitude, and peak power during concentric contractions at the seven loads and at 60° s -1 decreased (P < 0.05) similarly in the men and women. At 48 h post-exercise, the MVIC torque, power (for loads ≥20-60% MVIC), and voluntary activation remained depressed (P < 0.05), but the resting twitch had returned to baseline (P > 0.05) with no sex differences. Central mechanisms were primarily responsible for the depressed maximal force production up to 48 h after repeated eccentric contractions of the knee extensors and these mechanisms were similar in men and women.

  4. Cooling-induced contraction in ovine airways smooth muscle.

    PubMed

    Mustafa, S M; Pilcher, C W; Williams, K I

    1999-02-01

    The mechanism of cold-induced bronchoconstriction is poorly understood. This prompted the present study whose aim was to determine the step-wise direct effect of cooling on smooth muscle of isolated ovine airways and analyse the role of calcium in the mechanisms involved. Isolated tracheal strips and bronchial segments were suspended in organ baths containing Krebs' solution for isometric tension recording. Tissue responses during stepwise cooling from 37 to 5 degrees C were examined. Cooling induced a rapid and reproducible contraction proportional to cooling temperature in ovine tracheal and bronchial preparations which was epithelium-independent. On readjustment to 37 degrees C the tone returned rapidly to basal level. Maximum contraction was achieved at a temperature of 5 degrees C for trachea and 15 degrees C for bronchiole. Cooling-induced contractions (CIC) was resistant to tetrodotoxin (1; 10 micrometer), and not affected by the muscarinic antagonist atropine (1 micrometer) or the alpha-adrenergic antagonist phentolamine (1 micrometer), or the histamine H1-antagonist mepyramine (1 micrometer) or indomethacin (1 micrometer). Ca2+ antagonists (nifedipine and verapamil) and Mn2+ raised tracheal but not bronchiolar tone and augmented CIC. Incubation in Ca2+-free, EGTA-containing Krebs' solution for 5 min had no effect on CIC, although it significantly reduced KCl-induced contraction by up to 75%. Cooling inhibited Ca2+ influx measured using 45Ca2+ uptake. Caffeine (100 micrometer) significantly inhibited CIC. The results show that cooling-induced contractions do not appear to involve activation of nerve endings, all surface reception systems or Ca2+ influx. However, CIC is mainly dependent on release of intracellular Ca2+. Copyright 1999 The Italian Pharmacological Society.

  5. Fatiguing contractions increase protein S-glutathionylation occupancy in mouse skeletal muscle

    DOE PAGES

    Kramer, Philip A.; Duan, Jicheng; Gaffrey, Matthew J.; ...

    2018-05-23

    Protein S-glutathionylation is an important reversible post-translational modification implicated in redox signaling. Oxidative modifications to protein thiols can alter the activity of metabolic enzymes, transcription factors, kinases, phosphatases, and the function of contractile proteins. However, the extent to which muscle contraction induces oxidative modifications in redox sensitive thiols is not known. The purpose of this study was to determine the targets of S-glutathionylation redox signaling following fatiguing contractions. Anesthetized adult male CB6F1 (BALB/cBy × C57BL/6) mice were subjected to acute fatiguing contractions for 15 min using in vivo stimulations. The right (stimulated) and left (unstimulated) gastrocnemius muscleswere collected 60 minmore » after the last stimulation and processed for redox proteomics assay of S-glutathionylation.« less

  6. Fatiguing contractions increase protein S-glutathionylation occupancy in mouse skeletal muscle

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kramer, Philip A.; Duan, Jicheng; Gaffrey, Matthew J.

    Protein S-glutathionylation is an important reversible post-translational modification implicated in redox signaling. Oxidative modifications to protein thiols can alter the activity of metabolic enzymes, transcription factors, kinases, phosphatases, and the function of contractile proteins. However, the extent to which muscle contraction induces oxidative modifications in redox sensitive thiols is not known. The purpose of this study was to determine the targets of S-glutathionylation redox signaling following fatiguing contractions. Anesthetized adult male CB6F1 (BALB/cBy × C57BL/6) mice were subjected to acute fatiguing contractions for 15 min using in vivo stimulations. The right (stimulated) and left (unstimulated) gastrocnemius muscleswere collected 60 minmore » after the last stimulation and processed for redox proteomics assay of S-glutathionylation.« less

  7. Comparison between electrically evoked and voluntary isometric contractions for biceps brachii muscle oxidative metabolism using near-infrared spectroscopy.

    PubMed

    Muthalib, Makii; Jubeau, Marc; Millet, Guillaume Y; Maffiuletti, Nicola A; Nosaka, Kazunori

    2009-09-01

    This study compared voluntary (VOL) and electrically evoked isometric contractions by muscle stimulation (EMS) for changes in biceps brachii muscle oxygenation (tissue oxygenation index, DeltaTOI) and total haemoglobin concentration (DeltatHb = oxygenated haemoglobin + deoxygenated haemoglobin) determined by near-infrared spectroscopy. Twelve men performed EMS with one arm followed 24 h later by VOL with the contralateral arm, consisting of 30 repeated (1-s contraction, 1-s relaxation) isometric contractions at 30% of maximal voluntary contraction (MVC) for the first 60 s, and maximal intensity contractions thereafter (MVC for VOL and maximal tolerable current at 30 Hz for EMS) until MVC decreased approximately 30% of pre-exercise MVC. During the 30 contractions at 30% MVC, DeltaTOI decrease was significantly (P < 0.05) greater and DeltatHb was significantly (P < 0.05) lower for EMS than VOL, suggesting that the metabolic demand for oxygen in EMS is greater than VOL at the same torque level. However, during maximal intensity contractions, although EMS torque (approximately 40% of VOL) was significantly (P < 0.05) lower than VOL, DeltaTOI was similar and tHb was significantly (P < 0.05) lower for EMS than VOL towards the end, without significant differences between the two sessions in the recovery period. It is concluded that the oxygen demand of the activated biceps brachii muscle in EMS is comparable to VOL at maximal intensity.

  8. Inhibition of xanthine oxidase reduces oxidative stress and improves skeletal muscle function in response to electrically stimulated isometric contractions in aged mice

    PubMed Central

    Ryan, Michael J.; Jackson, Janna R.; Hao, Yanlei; Leonard, Stephen S.; Alway, Stephen E.

    2012-01-01

    Oxidative stress is a putative factor responsible for reducing function and increasing apoptotic signaling in skeletal muscle with aging. This study examined the contribution and functional significance of the xanthine oxidase enzyme as a potential source of oxidant production in aged skeletal muscle during repetitive in situ electrically stimulated isometric contractions. Xanthine oxidase activity was inhibited in young adult and aged mice via a subcutaneously placed time release (2.5 mg/day) allopurinol pellet, 7 days prior to the start of in situ electrically stimulated isometric contractions. Gastrocnemius muscles were electrically activated with 20 maximal contractions for three consecutive days. Xanthine oxidase activity was 65% greater in the gastrocnemius muscle of aged mice compared to young mice. Xanthine oxidase activity also increased after in situ electrically stimulated isometric contractions in muscles from both young (33%) and aged (28%) mice, relative to contralateral non-contracted muscles. Allopurinol attenuated the exercise-induced increase in oxidative stress, but it did not affect the elevated basal levels of oxidative stress that was associated with aging. In addition, inhibition of xanthine oxidase activity decreased caspase 3 activity, but it had no effect on other markers of mitochondrial associated apoptosis. Our results show that compared to control conditions, suppression of xanthine oxidase activity by allopurinol reduced xanthine oxidase activity, H2O2 levels, lipid peroxidation and caspase-3 activity, prevented the in situ electrically stimulated isometric contraction-induced loss of glutathione, prevented the increase of catalase and copper-zinc superoxide dismutase activities, and increased maximal isometric force in the plantar flexor muscles of aged mice after repetitive electrically evoked contractions. PMID:21530649

  9. Concordance of the location of the innervation zone of the tibialis anterior muscle using voluntary and imposed contractions by electrostimulation.

    PubMed

    Guzmán-Venegas, R A; Bralic, M P; Cordero, J J; Cavada, G; Araneda, O F

    2016-04-01

    The innervation zone (IZ) corresponds to the location of the neuromuscular junctions. Its location can be determined by using arranged surface linear electrode arrays. Typically, voluntary muscle contractions (VC) are used in this method. However, it also may be necessary to locate the IZ under clinical conditions such as spasticity, in which this type of contraction is difficult to perform. Therefore, contractions imposed by electrostimulation (ES) can be an alternative. There is little background comparing the locations of IZ obtained by two different types of contractions. Evaluate the concordance between using voluntary and imposed contractions from electrostimulation in order to determine the location of the innervation zone of the tibialis anterior muscle in healthy volunteers. The tibialis anterior (TA) muscle of sixteen volunteers (men: 8; women: 8; age: 22.1±1.4years, weight: 61.6±7.5kg, height: 167.1±7.5cm) were evaluated using a linear electrode array. The IZ of the TA muscle was located using two types of muscle contractions, voluntary (10% MVC) and imposed contractions by ES. The concordance between both conditions was evaluated using the Bland-Altman method and the concordance correlation coefficient (CCC). The analyses were applied to the absolute and relative positions to the length of an anatomical landmark frame. CCC for absolute position was 0.98 (p<0.0001, 95% CI [0.98-1.00], and CCC for relative positions also was 0.98 (p<0.0001, 95% CI [0.97-1.00]). The Bland-Altman analysis for absolute data showed an average difference of -0.63mm (SD: 4.1). Whereas, for adjusted data, the average difference was -0.20% (SD: 1.2). The power of the results, based on absolute data, was 98%, whereas for relative data, 82%. In healthy volunteers, there was a substantially concordance between the location of the IZ of the TA muscle derived from using contractions imposed by ES and the location derived from using VC. Copyright © 2016 Elsevier Ltd. All rights

  10. Local Muscle Metabolic Demand Induced by Neuromuscular Electrical Stimulation and Voluntary Contractions at Different Force Levels: A NIRS Study.

    PubMed

    Muthalib, Makii; Kerr, Graham; Nosaka, Kazunori; Perrey, Stephane

    2016-06-13

    Functional Muscle metabolic demand during contractions evoked by neuromuscular electrical stimulation (NMES) has been consistently documented to be greater than voluntary contractions (VOL) at the same force level (10-50% maximal voluntary contraction-MVC). However, we have shown using a near-infrared spectroscopy (NIRS) technique that local muscle metabolic demand is similar between NMES and VOL performed at MVC levels, thus controversy exists. This study therefore compared biceps brachii muscle metabolic demand (tissue oxygenation index-TOI and total hemoglobin volume-tHb) during a 10s isometric contraction of the elbow flexors between NMES (stimulation frequency of 30Hz and current level to evoke 30% MVC) and VOL at 30% MVC (VOL-30%MVC) and MVC (VOL-MVC) level in 8 healthy men (23-33-y). Greater changes in TOI and tHb induced by NMES than VOL-30%MVC confirm previous studies of a greater local metabolic demand for NMES than VOL at the same force level. The same TOI and tHb changes for NMES and VOL-MVC suggest that local muscle metabolic demand and intramuscular pressure were similar between conditions. In conclusion, these findings indicate that NMES induce a similar local muscle metabolic demand as that of maximal VOL.

  11. Local Muscle Metabolic Demand Induced by Neuromuscular Electrical Stimulation and Voluntary Contractions at Different Force Levels: A NIRS Study

    PubMed Central

    Muthalib, Makii; Kerr, Graham; Nosaka, Kazunori; Perrey, Stephane

    2016-01-01

    Functional Muscle metabolic demand during contractions evoked by neuromuscular electrical stimulation (NMES) has been consistently documented to be greater than voluntary contractions (VOL) at the same force level (10-50% maximal voluntary contraction-MVC). However, we have shown using a near-infrared spectroscopy (NIRS) technique that local muscle metabolic demand is similar between NMES and VOL performed at MVC levels, thus controversy exists. This study therefore compared biceps brachii muscle metabolic demand (tissue oxygenation index-TOI and total hemoglobin volume-tHb) during a 10s isometric contraction of the elbow flexors between NMES (stimulation frequency of 30Hz and current level to evoke 30% MVC) and VOL at 30% MVC (VOL-30%MVC) and MVC (VOL-MVC) level in 8 healthy men (23-33-y). Greater changes in TOI and tHb induced by NMES than VOL-30%MVC confirm previous studies of a greater local metabolic demand for NMES than VOL at the same force level. The same TOI and tHb changes for NMES and VOL-MVC suggest that local muscle metabolic demand and intramuscular pressure were similar between conditions. In conclusion, these findings indicate that NMES induce a similar local muscle metabolic demand as that of maximal VOL. PMID:27478574

  12. Electromechanical delay of abdominal muscles is modified by low back pain prevention exercise.

    PubMed

    Szpala, Agnieszka; Rutkowska-Kucharska, Alicja; Drapala, Jaroslaw

    2014-01-01

    The objective of the research was to assess the effect of a 4-week-long training program on selected parameters: electromechanical delay (EMD) and amplitude of electromyographic signal (EMG). Fourteen female students of the University School of Physical Education participated in the study. Torques and surface electromyography were evaluated under static conditions. Surface electrodes were glued to both sides of the rectus abdominis (RA), external oblique (EO), and erector spinae (ES) muscles. The 4-week-long program was aimed at strengthening the abdominal muscles and resulted in increased EMD during maximum torque production by flexors of the trunk, increased amplitudes of the signals of the erector spinae ( p = 0.005), and increased EMG amplitude asymmetry of the lower ( p = 0.013) and upper part ( p = 0.006) of the rectus abdominis muscle. In a training program composed of a large number of repetitions of strength exercises, in which the training person uses their own weight as the load (like in exercises such as curl-ups), the process of recruitment of motor units is similar to that found during fatiguing exercises and plyometric training.

  13. Definite differences between in vitro actin-myosin sliding and muscle contraction as revealed using antibodies to myosin head.

    PubMed

    Sugi, Haruo; Chaen, Shigeru; Kobayashi, Takakazu; Abe, Takahiro; Kimura, Kazushige; Saeki, Yasutake; Ohnuki, Yoshiki; Miyakawa, Takuya; Tanokura, Masaru; Sugiura, Seiryo

    2014-01-01

    Muscle contraction results from attachment-detachment cycles between myosin heads extending from myosin filaments and actin filaments. It is generally believed that a myosin head first attaches to actin, undergoes conformational changes to produce force and motion in muscle, and then detaches from actin. Despite extensive studies, the molecular mechanism of myosin head conformational changes still remains to be a matter for debate and speculation. The myosin head consists of catalytic (CAD), converter (CVD) and lever arm (LD) domains. To give information about the role of these domains in the myosin head performance, we have examined the effect of three site-directed antibodies to the myosin head on in vitro ATP-dependent actin-myosin sliding and Ca2+-activated contraction of muscle fibers. Antibody 1, attaching to junctional peptide between 50K and 20K heavy chain segments in the CAD, exhibited appreciable effects neither on in vitro actin-myosin sliding nor muscle fiber contraction. Since antibody 1 covers actin-binding sites of the CAD, one interpretation of this result is that rigor actin-myosin linkage is absent or at most a transient intermediate in physiological actin-myosin cycling. Antibody 2, attaching to reactive lysine residue in the CVD, showed a marked inhibitory effect on in vitro actin-myosin sliding without changing actin-activated myosin head (S1) ATPase activity, while it showed no appreciable effect on muscle contraction. Antibody 3, attaching to two peptides of regulatory light chains in the LD, had no significant effect on in vitro actin-myosin sliding, while it reduced force development in muscle fibers without changing MgATPase activity. The above definite differences in the effect of antibodies 2 and 3 between in vitro actin-myosin sliding and muscle contraction can be explained by difference in experimental conditions; in the former, myosin heads are randomly oriented on a glass surface, while in the latter myosin heads are regularly

  14. Definite Differences between In Vitro Actin-Myosin Sliding and Muscle Contraction as Revealed Using Antibodies to Myosin Head

    PubMed Central

    Sugi, Haruo; Chaen, Shigeru; Kobayashi, Takakazu; Abe, Takahiro; Kimura, Kazushige; Saeki, Yasutake; Ohnuki, Yoshiki; Miyakawa, Takuya; Tanokura, Masaru; Sugiura, Seiryo

    2014-01-01

    Muscle contraction results from attachment-detachment cycles between myosin heads extending from myosin filaments and actin filaments. It is generally believed that a myosin head first attaches to actin, undergoes conformational changes to produce force and motion in muscle, and then detaches from actin. Despite extensive studies, the molecular mechanism of myosin head conformational changes still remains to be a matter for debate and speculation. The myosin head consists of catalytic (CAD), converter (CVD) and lever arm (LD) domains. To give information about the role of these domains in the myosin head performance, we have examined the effect of three site-directed antibodies to the myosin head on in vitro ATP-dependent actin-myosin sliding and Ca2+-activated contraction of muscle fibers. Antibody 1, attaching to junctional peptide between 50K and 20K heavy chain segments in the CAD, exhibited appreciable effects neither on in vitro actin-myosin sliding nor muscle fiber contraction. Since antibody 1 covers actin-binding sites of the CAD, one interpretation of this result is that rigor actin-myosin linkage is absent or at most a transient intermediate in physiological actin-myosin cycling. Antibody 2, attaching to reactive lysine residue in the CVD, showed a marked inhibitory effect on in vitro actin-myosin sliding without changing actin-activated myosin head (S1) ATPase activity, while it showed no appreciable effect on muscle contraction. Antibody 3, attaching to two peptides of regulatory light chains in the LD, had no significant effect on in vitro actin-myosin sliding, while it reduced force development in muscle fibers without changing MgATPase activity. The above definite differences in the effect of antibodies 2 and 3 between in vitro actin-myosin sliding and muscle contraction can be explained by difference in experimental conditions; in the former, myosin heads are randomly oriented on a glass surface, while in the latter myosin heads are regularly

  15. The excitation-contraction coupling on C2C12 skeletal muscle myotubes was modulated by NO-donor ester of gemfibrozil.

    PubMed

    Maccallini, Cristina; Pietrangelo, Tiziana; Mancinelli, Rosa; Amoroso, Rosa; Bettoni, Giancarlo; Fulle, Stefania

    2008-05-01

    The excitation-contraction coupling in skeletal muscle is modulated by nitric oxide via redox status modification of ryanodine receptor on sarcoplasmic reticulum during events that lead to muscle contraction. We have synthesized a derivative of antilipidemic drug, gemfibrozil, in which a NO-donor furoxan moiety is joined to the fibrate by an ester linkage. Aim of the present study was to determine if the NO released from the above compound is capable of influencing the NO-sensible E-C coupling steps in skeletal muscle and if this effect could be potentially utilised for physiopathological studies and pharmaceutical applications. To obtain this goal we decided to study some of the excitation-contraction mechanisms in the presence of NO-releasing derivative of gemfibrozil in skeletal muscle C2C12 cell line.

  16. Local small airway epithelial injury induces global smooth muscle contraction and airway constriction.

    PubMed

    Zhou, Jian; Alvarez-Elizondo, Martha B; Botvinick, Elliot; George, Steven C

    2012-02-01

    Small airway epithelial cells form a continuous sheet lining the conducting airways, which serves many functions including a physical barrier to protect the underlying tissue. In asthma, injury to epithelial cells can occur during bronchoconstriction, which may exacerbate airway hyperreactivity. To investigate the role of epithelial cell rupture in airway constriction, laser ablation was used to precisely rupture individual airway epithelial cells of small airways (<300-μm diameter) in rat lung slices (∼250-μm thick). Laser ablation of single epithelial cells using a femtosecond laser reproducibly induced airway contraction to ∼70% of the original cross-sectional area within several seconds, and the contraction lasted for up to 40 s. The airway constriction could be mimicked by mechanical rupture of a single epithelial cell using a sharp glass micropipette but not with a blunt glass pipette. These results suggest that soluble mediators released from the wounded epithelial cell induce global airway contraction. To confirm this hypothesis, the lysate of primary human small airway epithelial cells stimulated a similar airway contraction. Laser ablation of single epithelial cells triggered a single instantaneous Ca(2+) wave in the epithelium, and multiple Ca(2+) waves in smooth muscle cells, which were delayed by several seconds. Removal of extracellular Ca(2+) or decreasing intracellular Ca(2+) both blocked laser-induced airway contraction. We conclude that local epithelial cell rupture induces rapid and global airway constriction through release of soluble mediators and subsequent Ca(2+)-dependent smooth muscle shortening.

  17. Cine phase contrast MRI to measure continuum Lagrangian finite strain fields in contracting skeletal muscle.

    PubMed

    Zhou, Hehe; Novotny, John E

    2007-01-01

    To measure the complex mechanics and Lagrangian finite strain of contracting human skeletal muscle in vivo with cine phase contrast MRI (CPC-MRI) applied to the human supraspinatus muscle of the shoulder. Processing techniques are applied to transform velocities from CPC-MRI images to displacements and planar Lagrangian finite strain. An interpolation method describing the continuity of the velocity field and forward-backward and Fourier transform methods were used to track the displacement of regions of interest during a cyclic abduction motion of a subject's arm. The components of the Lagrangian strain tensor were derived during the motion and principal and maximum in-plane shear strain fields calculated. Derived displacement and strain fields are shown that describe the contraction mechanics of the supraspinatus. Strains vary over time during the cyclic motion and are highly nonuniform throughout the muscle. This method presented overcomes the physical resolution of the MRI scanner, which is crucial for the detection of detailed information within muscles, such as the changes that might occur with partial tears of the supraspinatus. These can then be used as input or validation data for modeling human skeletal muscle.

  18. Surface-EMG analysis for the quantification of thigh muscle dynamic co-contractions during normal gait.

    PubMed

    Strazza, Annachiara; Mengarelli, Alessandro; Fioretti, Sandro; Burattini, Laura; Agostini, Valentina; Knaflitz, Marco; Di Nardo, Francesco

    2017-01-01

    The research purpose was to quantify the co-contraction patterns of quadriceps femoris (QF) vs. hamstring muscles during free walking, in terms of onset-offset muscular activation, excitation intensity, and occurrence frequency. Statistical gait analysis was performed on surface-EMG signals from vastus lateralis (VL), rectus femoris (RF), and medial hamstrings (MH), in 16315 strides walked by 30 healthy young adults. Results showed full superimpositions of MH with both VL and RF activity from terminal swing, 80 to 100% of gait cycle (GC), to the successive loading response (≈0-15% of GC), in around 90% of the considered strides. A further superimposition was detected during the push-off phase both between VL and MH activation intervals (38.6±12.8% to 44.1±9.6% of GC) in 21.9±13.6% of strides, and between RF and MH activation intervals (45.9±5.3% to 50.7±9.7 of GC) in 32.7±15.1% of strides. These findings led to identify three different co-contractions among QF and hamstring muscles during able-bodied walking: in early stance (in ≈90% of strides), in push-off (in 25-30% of strides) and in terminal swing (in ≈90% of strides). The co-contraction in terminal swing is the one with the highest levels of muscle excitation intensity. To our knowledge, this analysis represents the first attempt for quantification of QF/hamstring muscles co-contraction in young healthy subjects during normal gait, able to include the physiological variability of the phenomenon. Copyright © 2016 Elsevier B.V. All rights reserved.

  19. Selective inhibition of ATPase activity during contraction alters the activation of p38 MAP kinase isoforms in skeletal muscle

    PubMed Central

    Brault, Jeffrey J.; Pizzimenti, Natalie M.; Dentel, John N.; Wiseman, Robert W.

    2013-01-01

    Muscle contractions strongly activate p38 MAP kinases, but the precise contraction-associated sarcoplasmic event(s) (e.g. force production, energetic demands and/or calcium cycling) that activate these kinases are still unclear. We tested the hypothesis that during contraction the phosphorylation of p38 isoforms is sensitive to the increase in ATP demand relative to ATP supply. Energetic demands were inhibited using N-benzyl-p-toluene sulphonamide (BTS, type II actomyosin) and cyclopiazonic acid (CPA, SERCA). Extensor digitorum longus muscles from Swiss Webster mice were incubated in Ringer’s solution (37°C) with or without inhibitors and then stimulated at 10 Hz for 15 min. Muscles were immediately freeze-clamped for metabolite and western blot analysis. BTS and BTS+CPA treatment decreased force production by 85%, as measured by the tension time integral, while CPA alone potentiated force by 310%. In control muscles, contractions resulted in a 73% loss of ATP content and a concomitant 7-fold increase in IMP content, a measure of sustained energetic imbalance. BTS or CPA treatment lessened the loss of ATP, but BTS+CPA treatment completely eliminated the energetic imbalance since ATP and IMP levels were nearly equal to those of non-stimulated muscles. The independent inhibition of cytosolic ATPase activities had no effect on contraction-induced p38 MAPK phosphorylation, but combined treatment prevented the increase in phosphorylation of the γ isoform while the α/βisoforms unaffected. These observations suggest that an energetic signal may trigger phosphorylation of the p38γ isoform while other factors are involved in activating the α/β isoforms, and also may explain how contractions differentially activate signaling pathways. PMID:23296747

  20. Structural Basis for the Regulation of Muscle Contraction by Troponin and Tropomyosin

    PubMed Central

    Galińska-Rakoczy, Agnieszka; Engel, Patti; Xu, Chen; Jung, HyunSuk; Craig, Roger; Tobacman, Larry S.; Lehman, William

    2008-01-01

    The molecular switching mechanism governing skeletal and cardiac muscle contraction couples the binding of Ca2+ on troponin to the movement of tropomyosin on actin filaments. Despite years of investigation, this mechanism remains unclear because it has not yet been possible to directly assess the structural influence of troponin on tropomyosin that causes actin filaments, and hence myosin-crossbridge cycling and contraction, to switch on and off. A C-terminal domain of troponin I is thought to be intimately involved in inducing tropomyosin movement to an inhibitory position that blocks myosin-crossbridge interaction. Release of this regulatory, latching domain from actin after Ca2+-binding to TnC presumably allows tropomyosin movement away from the inhibitory position on actin, thus initiating contraction. However, the structural interactions of the regulatory domain of TnI with tropomyosin and actin that cause tropomyosin movement are unknown and thus the regulatory process is not well defined. Here, thin filaments were labeled with an engineered construct representing C-terminal TnI and then 3D-EM was used to resolve where troponin is anchored on actin-tropomyosin. EM-reconstruction showed how TnI-binding to both actin and tropomyosin at low-Ca2+ competes with tropomyosin for a common site on actin and drives tropomyosin movement to a constrained, relaxing position to inhibit myosin-crossbridge association. Thus the observations reported reveal the structural mechanism responsible for troponin-tropomyosin-mediated steric-interference of actin-myosin interaction that regulates muscle contraction. PMID:18514658

  1. Role of ROCK expression in gallbladder smooth muscle contraction.

    PubMed

    Wang, Bin; Ding, You-Ming; Wang, Chun-Tao; Wang, Wei-Xing

    2015-08-01

    Cholelithiasis is a common medical condition whose incidence rate is increasing yearly, while its pathogenesis has yet to be elucidated. The present study assessed the expression of Rho-kinase (ROCK) in gallbladder smooth muscles and its effect on the contractile function of gallbladder smooth muscles during gallstone formation. Thirty male guinea pigs were randomly divided into three groups: The control group, the gallstone model group and the fasudil interference group. The fasting volume (FV) and bile capacity of the gallbladder (FB) as well as the total cholesterol (TC) and triglyceride (TG) contents of the gallbladder bile were determined. In addition, the gallbladder was dissected to identify whether any gallstones had formed. Part of the gallbladder tissue specimens were used for immunohistochemical analysis of ROCK expression in gallbladder smooth muscles. The results showed that four guinea pigs in the model group and eight in the fasudil group displayed gallstone formation, while there was no gallstone formation in the control group. The FV and FB were significantly increased in the model and fasudil groups. Similarly, the TC and TG contents of gallbladder bile were increased in these groups. The positive expression rate of ROCK in gallbladder smooth muscles in the model and fasudil groups was significantly reduced compared with that in the control group (P<0.05). The results of the present study indicated that the reduction of ROCK expression in guinea pig gallbladder smooth muscles weakened gallbladder contraction and thereby promoted gallstone formation.

  2. Cytoskeletal tropomyosin Tm5NM1 is required for normal excitation-contraction coupling in skeletal muscle.

    PubMed

    Vlahovich, Nicole; Kee, Anthony J; Van der Poel, Chris; Kettle, Emma; Hernandez-Deviez, Delia; Lucas, Christine; Lynch, Gordon S; Parton, Robert G; Gunning, Peter W; Hardeman, Edna C

    2009-01-01

    The functional diversity of the actin microfilaments relies in part on the actin binding protein tropomyosin (Tm). The muscle-specific Tms regulate actin-myosin interactions and hence contraction. However, there is less known about the roles of the numerous cytoskeletal isoforms. We have shown previously that a cytoskeletal Tm, Tm5NM1, defines a Z-line adjacent cytoskeleton in skeletal muscle. Recently, we identified a second cytoskeletal Tm in this region, Tm4. Here we show that Tm4 and Tm5NM1 define separate actin filaments; the former associated with the terminal sarcoplasmic reticulum (SR) and other tubulovesicular structures. In skeletal muscles of Tm5NM1 knockout (KO) mice, Tm4 localization was unchanged, demonstrating the specificity of the membrane association. Tm5NM1 KO muscles exhibit potentiation of T-system depolarization and decreased force rundown with repeated T-tubule depolarizations consistent with altered T-tubule function. These results indicate that a Tm5NM1-defined actin cytoskeleton is required for the normal excitation-contraction coupling in skeletal muscle.

  3. Cytoskeletal Tropomyosin Tm5NM1 Is Required for Normal Excitation–Contraction Coupling in Skeletal Muscle

    PubMed Central

    Vlahovich, Nicole; Kee, Anthony J.; Van der Poel, Chris; Kettle, Emma; Hernandez-Deviez, Delia; Lucas, Christine; Lynch, Gordon S.; Parton, Robert G.; Gunning, Peter W.

    2009-01-01

    The functional diversity of the actin microfilaments relies in part on the actin binding protein tropomyosin (Tm). The muscle-specific Tms regulate actin-myosin interactions and hence contraction. However, there is less known about the roles of the numerous cytoskeletal isoforms. We have shown previously that a cytoskeletal Tm, Tm5NM1, defines a Z-line adjacent cytoskeleton in skeletal muscle. Recently, we identified a second cytoskeletal Tm in this region, Tm4. Here we show that Tm4 and Tm5NM1 define separate actin filaments; the former associated with the terminal sarcoplasmic reticulum (SR) and other tubulovesicular structures. In skeletal muscles of Tm5NM1 knockout (KO) mice, Tm4 localization was unchanged, demonstrating the specificity of the membrane association. Tm5NM1 KO muscles exhibit potentiation of T-system depolarization and decreased force rundown with repeated T-tubule depolarizations consistent with altered T-tubule function. These results indicate that a Tm5NM1-defined actin cytoskeleton is required for the normal excitation–contraction coupling in skeletal muscle. PMID:19005216

  4. Pennation angle dependency in skeletal muscle tissue doppler strain in dynamic contractions.

    PubMed

    Lindberg, Frida; Öhberg, Fredrik; Granåsen, Gabriel; Brodin, Lars-Åke; Grönlund, Christer

    2011-07-01

    Tissue velocity imaging (TVI) is a Doppler based ultrasound technique that can be used to study regional deformation in skeletal muscle tissue. The aim of this study was to develop a biomechanical model to describe the TVI strain's dependency on the pennation angle. We demonstrate its impact as the subsequent strain measurement error using dynamic elbow contractions from the medial and the lateral part of biceps brachii at two different loadings; 5% and 25% of maximum voluntary contraction (MVC). The estimated pennation angles were on average about 4° in extended position and increased to a maximal of 13° in flexed elbow position. The corresponding relative angular error spread from around 7% up to around 40%. To accurately apply TVI on skeletal muscles, the error due to angle changes should be compensated for. As a suggestion, this could be done according to the presented model. Copyright © 2011 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  5. A Simple, Inexpensive Model to Demonstrate How Contraction of GI Longitudinal Smooth Muscle Promotes Propulsion

    ERIC Educational Resources Information Center

    Lujan, Heidi L.; DiCarlo, Stephen E.

    2015-01-01

    Peristalis is a propulsive activity that involves both circular and longitudinal muscle layers of the esophagus, distal stomach, and small and large intestines. During peristalsis, the circular smooth muscle contracts behind (on the orad side) the bolus and relaxes in front (on the aborad side) of the bolus. At the same time, the longitudinal…

  6. Calibration of EMG to force for knee muscles is applicable with submaximal voluntary contractions.

    PubMed

    Doorenbosch, Caroline A M; Joosten, Annemiek; Harlaar, Jaap

    2005-08-01

    In this study, the influence of using submaximal isokinetic contractions about the knee compared to maximal voluntary contractions as input to obtain the calibration of an EMG-force model for knee muscles is investigated. Isokinetic knee flexion and extension contractions were performed by healthy subjects at five different velocities and at three contraction levels (100%, 75% and 50% of MVC). Joint angle, angular velocity, joint moment and surface EMG of five knee muscles were recorded. Individual calibration values were calculated according to [C.A.M. Doorenbosch, J. Harlaar, A clinically applicable EMG-force model to quantify active stabilization of the knee after a lesion of the anterior cruciate ligament, Clinical Biomechanics 18 (2003) 142-149] for each contraction level. First, the output of the model, calibrated with the 100% MVC was compared to the actually exerted net knee moment at the dynamometer. Normalized root mean square errors were calculated [A.L. Hof, C.A.N. Pronk, J.A. van Best, Comparison between EMG to force processing and kinetic analysis for the calf muscle moment in walking and stepping, Journal of Biomechanics 20 (1987) 167-187] to compare the estimated moments with the actually exerted moments. Mean RMSD errors ranged from 0.06 to 0.21 for extension and from 0.12 to 0.29 for flexion at the 100% trials. Subsequently, the calibration results of the 50% and 75% MVC calibration procedures were used. A standard signal, representing a random EMG level was used as input in the EMG force model, to compare the three models. Paired samples t-tests between the 100% MVC and the 75% MVC and 50% MVC, respectively, showed no significant differences (p>0.05). The application of submaximal contractions of larger than 50% MVC is suitable to calibrate a simple EMG to force model for knee extension and flexion. This means that in clinical practice, the EMG to force model can be applied by patients who cannot exert maximal force.

  7. Motor Force Homeostasis in Skeletal Muscle Contraction

    PubMed Central

    Chen, Bin; Gao, Huajian

    2011-01-01

    In active biological contractile processes such as skeletal muscle contraction, cellular mitosis, and neuronal growth, an interesting common observation is that multiple motors can perform coordinated and synchronous actions, whereas individual myosin motors appear to randomly attach to and detach from actin filaments. Recent experiment has demonstrated that, during skeletal muscle shortening at a wide range of velocities, individual myosin motors maintain a force of ∼6 pN during a working stroke. To understand how such force-homeostasis can be so precisely regulated in an apparently chaotic system, here we develop a molecular model within a coupled stochastic-elastic theoretical framework. The model reveals that the unique force-stretch relation of myosin motor and the stochastic behavior of actin-myosin binding cause the average number of working motors to increase in linear proportion to the filament load, so that the force on each working motor is regulated at ∼6 pN, in excellent agreement with experiment. This study suggests that it might be a general principle to use catch bonds together with a force-stretch relation similar to that of myosin motors to regulate force homeostasis in many biological processes. PMID:21767492

  8. CD4 T Cells and Major Histocompatibility Complex Class II Expression Influence Worm Expulsion and Increased Intestinal Muscle Contraction during Trichinella spiralis Infection

    PubMed Central

    Vallance, Bruce A.; Galeazzi, Francesca; Collins, Stephen M.; Snider, Denis P.

    1999-01-01

    Expulsion of intestinal nematode parasites and the associated increased contraction by intestinal muscle are T cell dependent, since both are attenuated in athymic rodents. The CD4 T-cell subset has been strongly associated with worm expulsion; however, the relationship between these cells, antigen presentation, and worm expulsion is not definitive and the role of these factors in intestinal muscle hypercontractility has not been defined. We infected C57BL/6, athymic, CD4-deficient, CD8α-deficient, and major histocompatibility complex class II (MHC II)-deficient (C2d) mice with Trichinella spiralis larvae. We examined intestinal worm numbers, longitudinal muscle contraction, and MHC II expression. Numerous MHC II-positive cells were identified within the muscularis externa of infected but not uninfected C57BL/6 mice. C57BL/6 and CD8α-deficient mice developed large increases in muscle contraction, expelling the parasite by day 21. Athymic and C2d mice exhibited much smaller increases in muscle contraction and delayed parasite expulsion. CD4-deficient mice exhibited intermediate levels of muscle contraction and delayed parasite expulsion. To further examine the role of MHC II and CD4 T cells, we irradiated C2d mice and reconstituted them with C57BL/6 bone marrow alone or with C57BL/6 CD4 T cells. C57BL/6 bone marrow alone did not affect muscle function or worm expulsion in recipient C2d mice. Partial CD4 T-cell reconstitution was sufficient to restore increased muscle contraction but not worm expulsion. Thus, hematopoietic MHC II expression alone is insufficient for the development of muscle hypercontractility and worm expulsion, but the addition of even small numbers of CD4 T cells was sufficient to induce intestinal muscle pathophysiology. PMID:10531271

  9. Cannabinoid signalling inhibits sarcoplasmic Ca2+ release and regulates excitation–contraction coupling in mammalian skeletal muscle

    PubMed Central

    Oláh, Tamás; Bodnár, Dóra; Tóth, Adrienn; Vincze, János; Fodor, János; Reischl, Barbara; Kovács, Adrienn; Ruzsnavszky, Olga; Dienes, Beatrix; Szentesi, Péter; Friedrich, Oliver

    2016-01-01

    Key points Marijuana was found to cause muscle weakness, although the exact regulatory role of its receptors (CB1 cannabinoid receptor; CB1R) in the excitation–contraction coupling (ECC) of mammalian skeletal muscle remains unknown.We found that CB1R activation or its knockout did not affect muscle force directly, whereas its activation decreased the Ca2+‐sensitivity of the contractile apparatus and made the muscle fibres more prone to fatigue.We demonstrate that CB1Rs are not connected to the inositol 1,4,5‐trisphosphate pathway either in myotubes or in adult muscle fibres.By contrast, CB1Rs constitutively inhibit sarcoplasmic Ca2+ release and sarcoplasmic reticulum Ca2+ ATPase during ECC in a Gi/o protein‐mediated way in adult skeletal muscle fibres but not in myotubes.These results help with our understanding of the physiological effects and pathological consequences of CB1R activation in skeletal muscle and may be useful in the development of new cannabinoid drugs. Abstract Marijuana was found to cause muscle weakness, although it is unknown whether it affects the muscles directly or modulates only the motor control of the central nervous system. Although the presence of CB1 cannabinoid receptors (CB1R), which are responsible for the psychoactive effects of the drug in the brain, have recently been demonstrated in skeletal muscle, it is unclear how CB1R‐mediated signalling affects the contraction and Ca²⁺ homeostasis of mammalian skeletal muscle. In the present study, we demonstrate that in vitro CB1R activation increased muscle fatigability and decreased the Ca2+‐sensitivity of the contractile apparatus, whereas it did not alter the amplitude of single twitch contractions. In myotubes, CB1R agonists neither evoked, nor influenced inositol 1,4,5‐trisphosphate (IP3)‐mediated Ca2+ transients, nor did they alter excitation–contraction coupling. By contrast, in isolated muscle fibres of wild‐type mice, although CB1R agonists did not evoke IP3

  10. 8-Bromo-cAMP decreases the Ca2+ sensitivity of airway smooth muscle contraction through a mechanism distinct from inhibition of Rho-kinase.

    PubMed

    Endou, Katsuaki; Iizuka, Kunihiko; Yoshii, Akihiro; Tsukagoshi, Hideo; Ishizuka, Tamotsu; Dobashi, Kunio; Nakazawa, Tsugio; Mori, Masatomo

    2004-10-01

    To clarify whether cyclic AMP (cAMP)/cAMP-dependent protein kinase (PKA) activation and Rho-kinase inhibition share a common mechanism to decrease the Ca2+ sensitivity of airway smooth muscle contraction, we examined the effects of 8-bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP), a stable cAMP analog, and (+)-(R)-trans-4-(1-aminoethyl)-N-(4-pyridyl) cyclohexane carboxamide dihydrochloride, monohydrate (Y-27632), a Rho-kinase inhibitor, on carbachol (CCh)-, guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS)-, 4beta-phorbol 12,13-dibutyrate (PDBu)-, and leukotriene D4 (LTD4)-induced Ca2+ sensitization in alpha-toxin-permeabilized rabbit tracheal and human bronchial smooth muscle. In rabbit trachea, CCh-induced smooth muscle contraction was inhibited by 8-BrcAMP and Y-27632 to a similar extent. However, GTPgammaS-induced smooth muscle contraction was resistant to 8-BrcAMP. In the presence of a saturating concentration of Y-27632, PDBu-induced smooth muscle contraction was completely reversed by 8-BrcAMP. Conversely, PDBu-induced smooth muscle contraction was resistant to Y-27632. In the presence of a saturating concentration of 8-BrcAMP, GTPgammaS-induced Ca2+ sensitization was also reversed by Y-27632. The 8-BrcAMP had no effect on the ATP-triggered contraction of tracheal smooth muscle that had been treated with calyculin A in rigor solutions. The 8-BrcAMP and Y-27632 additively accelerated the relaxation rate of PDBu- and GTPgammaS-treated smooth muscle under myosin light chain kinase-inhibited conditions. In human bronchus, LTD4-induced smooth muscle contraction was inhibited by both 8-BrcAMP and Y-27632. We conclude that cAMP/PKA-induced Ca2+ desensitization contains at least two mechanisms: 1) inhibition of the muscarinic receptor signaling upstream from Rho activation and 2) cAMP/PKA's preferential reversal of PKC-mediated Ca2+ sensitization in airway smooth muscle.

  11. Trunk extensor muscle fatigue influences trunk muscle activities.

    PubMed

    Hoseinpoor, Tahere Seyed; Kahrizi, Sedighe; Mobini, Bahram

    2015-01-01

    Trunk muscles fatigue is one of the risk factors in workplaces and daily activities. Loads would be redistributed among active and passive tissues in a non-optimal manner in fatigue conditions. Therefore, a single tissue might be overloaded with minimal loads and as a result the risk of injury would increase. The goal of this paper was to assess the electromyographic response of trunk extensor and abdominal muscles after trunk extensor muscles fatigue induced by cyclic lifting task. This was an experimental study that twenty healthy women participated. For assessing automatic response of trunk extensor and abdominal muscles before and after the fatigue task, electromyographic activities of 6 muscles: thorasic erector spine (TES), lumbar erector spine (LES), lumbar multifidus (LMF), transverse abdominis/ internal oblique (TrA/IO), rectus abdominis (RA) and external oblique (EO) were recorded in standing position with no load and symmetric axial loads equal to 25% of their body weights. Statistical analysis showed that all the abdominal muscles activity decreased with axial loads after performing fatigue task but trunk extensor activity remained constant. Results of the current study indicated that muscle recruitment strategies changed with muscle fatigue and load bearing, therefore risks of tissue injury may increase in fatigue conditions.

  12. Effects of Duchenne muscular dystrophy on muscle stiffness and response to electrically-induced muscle contraction: A 12-month follow-up.

    PubMed

    Lacourpaille, Lilian; Gross, Raphaël; Hug, François; Guével, Arnaud; Péréon, Yann; Magot, Armelle; Hogrel, Jean-Yves; Nordez, Antoine

    2017-03-01

    The present study aimed to assess the ability of muscle stiffness (shear modulus) and response to electrically-induced muscle contraction to detect changes in muscle properties over a 12-month period in children with Duchenne muscular dystrophy (DMD). Ten children with DMD and nine age-matched healthy male controls participated in two experimental sessions (T 0 and T +12months ) separated by 12.4 ± 0.9 months. Two contractions of the biceps brachii were electrically-induced during which an ultrasound probe was placed over the muscle. The resting shear modulus was measured using elastography from six muscles. Evoked maximal torque was increased at T +12months in controls (+11.2 ± 7.6%, P <0.001) but was not modified in children with DMD (P = 0.222). Electromechanical delay (+12.9 ± 11.3%, P <0.001) and its force transmission component (+10.1 ± 21.6%, P = 0.003) were significantly longer at T +12months than T 0 for children with DMD. The results revealed an increase in muscle stiffness at T +12months in children with DMD for tibialis anterior (+75.1 ± 93.5%, P= 0.043), gastrocnemius medialis (+144.8 ± 180.6%, P= 0.050) and triceps brachii (+35.5 ± 32.2%, P= 0.005). This 12-month follow-up study demonstrates that electromechanical delay and elastography may help detect subtle muscle impairments in patients with DMD. These sensitive outcomes may improve the follow-up of innovative therapeutic interventions within the field of DMD. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Influence of voluntary pelvic floor muscle contraction and pelvic floor muscle training on urethral closure pressures: a systematic literature review.

    PubMed

    Zubieta, Maria; Carr, Rebecca L; Drake, Marcus J; Bø, Kari

    2016-05-01

    Stress urinary incontinence (SUI) is managed with pelvic floor muscle training (PFMT), but the mechanism of treatment action is unclear. Resting maximal urethral closure pressure (MUCP) is lower in women with SUI, but it is unknown whether PFMT can alter resting MUCP. This systematic review evaluated whether voluntary pelvic floor muscle (PFM) contraction increases MUCP above its resting value (augmented MUCP) and the effect of PFMT on resting and augmented MUCP. Experimental and effect studies were identified using PubMed and PEDro. The PEDro scale was used to assess internal validity of interventional studies. We identified 21 studies investigating the influence of voluntary PFM contraction in women. Comparison was hindered by varying demographics, antecedent history, reporting of confirmed correct PFM contraction, and urethral pressure profilometry (UPP) techniques. Mean incremental increase in MUCP during PFM contraction in healthy women was 8-47.3 cm H2O; in women with urinary incontinence (UI), it was 6-24 cm H2O. Nine trials reporting MUCP as an outcome of PFMT were found. Wide variation in PFMT regimes affected the findings. Two studies found significant improvement in MUCP of 5-18 cm H20. Seven studies assessed augmentation of MUCP with PFM contraction; mean increase was -0.1 to 25 cm H20. There is no definitive evidence that PFMT increases resting MUCP as its mechanism of action in managing SUI. The degree to which a voluntary PFM contraction augments MUCP varies widely. There was evidence to suggest PFMT increases augmented MUCP. Drawing firm conclusions was hampered by study methodologies.

  14. Carbachol-induced rabbit bladder smooth muscle contraction: roles of protein kinase C and Rho kinase.

    PubMed

    Wang, Tanchun; Kendig, Derek M; Smolock, Elaine M; Moreland, Robert S

    2009-12-01

    Smooth muscle contraction is regulated by phosphorylation of the myosin light chain (MLC) catalyzed by MLC kinase and dephosphorylation catalyzed by MLC phosphatase. Agonist stimulation of smooth muscle results in the inhibition of MLC phosphatase activity and a net increase in MLC phosphorylation and therefore force. The two pathways believed to be primarily important for inhibition of MLC phosphatase activity are protein kinase C (PKC)-catalyzed CPI-17 phosphorylation and Rho kinase (ROCK)-catalyzed myosin phosphatase-targeting subunit (MYPT1) phosphorylation. The goal of this study was to determine the roles of PKC and ROCK and their downstream effectors in regulating MLC phosphorylation levels and force during the phasic and sustained phases of carbachol-stimulated contraction in intact bladder smooth muscle. These studies were performed in the presence and absence of the PKC inhibitor bisindolylmaleimide-1 (Bis) or the ROCK inhibitor H-1152. Phosphorylation levels of Thr(38)-CPI-17 and Thr(696)/Thr(850)-MYPT1 were measured at different times during carbachol stimulation using site-specific antibodies. Thr(38)-CPI-17 phosphorylation increased concurrently with carbachol-stimulated force generation. This increase was reduced by inhibition of PKC during the entire contraction but was only reduced by ROCK inhibition during the sustained phase of contraction. MYPT1 showed high basal phosphorylation levels at both sites; however, only Thr(850) phosphorylation increased with carbachol stimulation; the increase was abolished by the inhibition of either ROCK or PKC. Our results suggest that during agonist stimulation, PKC regulates MLC phosphatase activity through phosphorylation of CPI-17. In contrast, ROCK phosphorylates both Thr(850)-MYPT1 and CPI-17, possibly through cross talk with a PKC pathway, but is only significant during the sustained phase of contraction. Last, our results demonstrate that there is a constitutively activate pool of ROCK that phosphorylates

  15. EMG parameters and EEG α Index change at fatigue period during different types of muscle contraction

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Zhou, Bin; Song, Gaoqing

    2010-10-01

    The purpose of this study is to measure and analyze the characteristics in change of EMG and EEG parameters at muscle fatigue period in participants with different exercise capacity. Twenty participants took part in the tests. They were divided into two groups, Group A (constant exerciser) and Group B (seldom-exerciser). MVC dynamic and 1/3 isometric exercises were performed; EMG and EEG signals were recorded synchronously during different type of muscle contraction. Results indicated that values of MVC, RMS and IEMG in Group A were greater than Group B, but isometric exercise time was shorter than the time of dynamic exercise although its intensity was light. Turning point of IEMG and α Index occurred synchronously during constant muscle contraction of isometric or dynamic exercise. It is concluded that IEMG turning point may be an indication to justify muscle fatigue. Synchronization of EEG and EMG reflects its common characteristics on its bio-electric change.

  16. EMG parameters and EEG α Index change at fatigue period during different types of muscle contraction

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Zhou, Bin; Song, Gaoqing

    2011-03-01

    The purpose of this study is to measure and analyze the characteristics in change of EMG and EEG parameters at muscle fatigue period in participants with different exercise capacity. Twenty participants took part in the tests. They were divided into two groups, Group A (constant exerciser) and Group B (seldom-exerciser). MVC dynamic and 1/3 isometric exercises were performed; EMG and EEG signals were recorded synchronously during different type of muscle contraction. Results indicated that values of MVC, RMS and IEMG in Group A were greater than Group B, but isometric exercise time was shorter than the time of dynamic exercise although its intensity was light. Turning point of IEMG and α Index occurred synchronously during constant muscle contraction of isometric or dynamic exercise. It is concluded that IEMG turning point may be an indication to justify muscle fatigue. Synchronization of EEG and EMG reflects its common characteristics on its bio-electric change.

  17. Mapping of spatial and temporal heterogeneity of plantar flexor muscle activity during isometric contraction: correlation of velocity-encoded MRI with EMG

    PubMed Central

    Csapo, Robert; Malis, Vadim; Sinha, Usha

    2015-01-01

    The aim of this study was to assess the correlation between contraction-associated muscle kinematics as measured by velocity-encoded phase-contrast (VE-PC) magnetic resonance imaging (MRI) and activity recorded via electromyography (EMG), and to construct a detailed three-dimensional (3-D) map of the contractile behavior of the triceps surae complex from the MRI data. Ten axial-plane VE-PC MRI slices of the triceps surae and EMG data were acquired during submaximal isometric contractions in 10 subjects. MRI images were analyzed to yield the degree of contraction-associated muscle displacement on a voxel-by-voxel basis and determine the heterogeneity of muscle movement within and between slices. Correlational analyses were performed to determine the agreement between EMG data and displacements. Pearson's coefficients demonstrated good agreement (0.84 < r < 0.88) between EMG data and displacements. Comparison between different slices in the gastrocnemius muscle revealed significant heterogeneity in displacement values both in-plane and along the cranio-caudal axis, with highest values in the mid-muscle regions. By contrast, no significant differences between muscle regions were found in the soleus muscle. Substantial differences among displacements were also observed within slices, with those in static areas being only 17–39% (maximum) of those in the most mobile muscle regions. The good agreement between EMG data and displacements suggests that VE-PC MRI may be used as a noninvasive, high-resolution technique for quantifying and modeling muscle activity over the entire 3-D volume of muscle groups. Application to the triceps surae complex revealed substantial heterogeneity of contraction-associated muscle motion both within slices and between different cranio-caudal positions. PMID:26112239

  18. The central nervous system (CNS)-independent anti-bone-resorptive activity of muscle contraction and the underlying molecular and cellular signatures.

    PubMed

    Qin, Weiping; Sun, Li; Cao, Jay; Peng, Yuanzhen; Collier, Lauren; Wu, Yong; Creasey, Graham; Li, Jianhua; Qin, Yiwen; Jarvis, Jonathan; Bauman, William A; Zaidi, Mone; Cardozo, Christopher

    2013-05-10

    Mechanisms by which muscle regulates bone are poorly understood. Electrically stimulated muscle contraction reversed elevations in bone resorption and increased Wnt signaling in bone-derived cells after spinal cord transection. Muscle contraction reduced resorption of unloaded bone independently of the CNS, through mechanical effects and, potentially, nonmechanical signals (e.g. myokines). The study provides new insights regarding muscle-bone interactions. Muscle and bone work as a functional unit. Cellular and molecular mechanisms underlying effects of muscle activity on bone mass are largely unknown. Spinal cord injury (SCI) causes muscle paralysis and extensive sublesional bone loss and disrupts neural connections between the central nervous system (CNS) and bone. Muscle contraction elicited by electrical stimulation (ES) of nerves partially protects against SCI-related bone loss. Thus, application of ES after SCI provides an opportunity to study the effects of muscle activity on bone and roles of the CNS in this interaction, as well as the underlying mechanisms. Using a rat model of SCI, the effects on bone of ES-induced muscle contraction were characterized. The SCI-mediated increase in serum C-terminal telopeptide of type I collagen (CTX) was completely reversed by ES. In ex vivo bone marrow cell cultures, SCI increased the number of osteoclasts and their expression of mRNA for several osteoclast differentiation markers, whereas ES significantly reduced these changes; SCI decreased osteoblast numbers, but increased expression in these cells of receptor activator of NF-κB ligand (RANKL) mRNA, whereas ES increased expression of osteoprotegerin (OPG) and the OPG/RANKL ratio. A microarray analysis revealed that ES partially reversed SCI-induced alterations in expression of genes involved in signaling through Wnt, FSH, parathyroid hormone (PTH), oxytocin, and calcineurin/nuclear factor of activated T-cells (NFAT) pathways. ES mitigated SCI-mediated increases in m

  19. Model-based inverse estimation for active contraction stresses of tongue muscles using 3D surface shape in speech production.

    PubMed

    Koike, Narihiko; Ii, Satoshi; Yoshinaga, Tsukasa; Nozaki, Kazunori; Wada, Shigeo

    2017-11-07

    This paper presents a novel inverse estimation approach for the active contraction stresses of tongue muscles during speech. The proposed method is based on variational data assimilation using a mechanical tongue model and 3D tongue surface shapes for speech production. The mechanical tongue model considers nonlinear hyperelasticity, finite deformation, actual geometry from computed tomography (CT) images, and anisotropic active contraction by muscle fibers, the orientations of which are ideally determined using anatomical drawings. The tongue deformation is obtained by solving a stationary force-equilibrium equation using a finite element method. An inverse problem is established to find the combination of muscle contraction stresses that minimizes the Euclidean distance of the tongue surfaces between the mechanical analysis and CT results of speech production, where a signed-distance function represents the tongue surface. Our approach is validated through an ideal numerical example and extended to the real-world case of two Japanese vowels, /ʉ/ and /ɯ/. The results capture the target shape completely and provide an excellent estimation of the active contraction stresses in the ideal case, and exhibit similar tendencies as in previous observations and simulations for the actual vowel cases. The present approach can reveal the relative relationship among the muscle contraction stresses in similar utterances with different tongue shapes, and enables the investigation of the coordination of tongue muscles during speech using only the deformed tongue shape obtained from medical images. This will enhance our understanding of speech motor control. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Management of complex abdominal wall defects associated with penetrating abdominal trauma.

    PubMed

    Arul, G Suren; Sonka, B J; Lundy, J B; Rickard, R F; Jeffery, S L A

    2015-03-01

    The paradigm of Damage Control Surgery (DCS) has radically improved the management of abdominal trauma, but less well described are the options for managing the abdominal wall itself in an austere environment. This article describes a series of patients with complex abdominal wall problems managed at the UK-led Role 3 Medical Treatment Facility (MTF) in Camp Bastion, Afghanistan. Contemporaneous review of a series of patients with complex abdominal wall injuries who presented to the Role 3 MTF between July and November 2012. Five patients with penetrating abdominal trauma associated with significant damage to the abdominal wall were included. All patients were managed using DCS principles, leaving the abdominal wall open at the end of the first procedure. Subsequent management of the abdominal wall was determined by a multidisciplinary team of general and plastic surgeons, intensivists and specialist nurses. The principles of management identified included minimising tissue loss on initial laparotomy by joining adjacent wounds and marginal debridement of dead tissue; contraction of the abdominal wall was minimised by using topical negative pressure dressing and dermal-holding sutures. Definitive closure was timed to allow oedema to settle and sepsis to be controlled. Closure techniques include delayed primary closure with traction sutures, components separation, and mesh closure with skin grafting. A daily multidisciplinary team discussion was invaluable for optimal decision making regarding the most appropriate means of abdominal closure. Dermal-holding sutures were particularly useful in preventing myostatic contraction of the abdominal wall. A simple flow chart was developed to aid decision making in these patients. This flow chart may prove especially useful in a resource-limited environment in which returning months or years later for closure of a large ventral hernia may not be possible. Published by the BMJ Publishing Group Limited. For permission to use

  1. p21-Activated kinase (Pak) regulates airway smooth muscle contraction by regulating paxillin complexes that mediate actin polymerization.

    PubMed

    Zhang, Wenwu; Huang, Youliang; Gunst, Susan J

    2016-09-01

    In airway smooth muscle, tension development caused by a contractile stimulus requires phosphorylation of the 20 kDa myosin light chain (MLC), which activates crossbridge cycling and the polymerization of a pool of submembraneous actin. The p21-activated kinases (Paks) can regulate the contractility of smooth muscle and non-muscle cells, and there is evidence that this occurs through the regulation of MLC phosphorylation. We show that Pak has no effect on MLC phosphorylation during the contraction of airway smooth muscle, and that it regulates contraction by mediating actin polymerization. We find that Pak phosphorylates the adhesion junction protein, paxillin, on Ser273, which promotes the formation of a signalling complex that activates the small GTPase, cdc42, and the actin polymerization catalyst, neuronal Wiskott-Aldrich syndrome protein (N-WASP). These studies demonstrate a novel role for Pak in regulating the contractility of smooth muscle by regulating actin polymerization. The p21-activated kinases (Pak) can regulate contractility in smooth muscle and other cell and tissue types, but the mechanisms by which Paks regulate cell contractility are unclear. In airway smooth muscle, stimulus-induced contraction requires phosphorylation of the 20 kDa light chain of myosin, which activates crossbridge cycling, as well as the polymerization of a small pool of actin. The role of Pak in airway smooth muscle contraction was evaluated by inhibiting acetylcholine (ACh)-induced Pak activation through the expression of a kinase inactive mutant, Pak1 K299R, or by treating tissues with the Pak inhibitor, IPA3. Pak inhibition suppressed actin polymerization and contraction in response to ACh, but it did not affect myosin light chain phosphorylation. Pak activation induced paxillin phosphorylation on Ser273; the paxillin mutant, paxillin S273A, inhibited paxillin Ser273 phosphorylation and inhibited actin polymerization and contraction. Immunoprecipitation analysis of

  2. Isoflavones isolated from red clover (Trifolium pratense) inhibit smooth muscle contraction of the isolated rat prostate gland.

    PubMed

    Brandli, A; Simpson, J S; Ventura, S

    2010-09-01

    This study investigated whether red clover contains any bioactive constituents which may affect contractility of rat prostatic smooth muscle in an attempt to determine whether its medicinal use in the treatment of benign prostatic hyperplasia is supported by pharmacological effects. A commercially available red clover extract was chemically fractionated and various isoflavones (genistein, formononetin and biochanin A) were isolated from these fractions and their effects on contractility were examined on preparations of the isolated rat prostate gland. Contractile effects of the isolated fractions were compared with commercially available isoflavones (genistein, formononetin and biochanin A). Pharmacological tools were used to investigate the mechanism of action modifying smooth muscle contraction. Crude red clover extract (Trinovin) inhibited electrical field stimulation induced contractions of the rat prostate across a range of frequencies with an IC(50) of approximately 68 microg/ml. Contractions of the rat prostate elicited by exogenous administration of acetylcholine, noradrenaline or adenosine 5'-triphosphate (ATP) were also inhibited. Chromatographic separation, and final purification by high performance liquid chromatography (HPLC) permitted the isolation of the isoflavones: daidzein, calycosin, formononetin, prunetin, pratensin, biochanin A and genistein. Genistein, formononetin and biochanin A (100 microM) from either commercial sources or isolated from red clover extract inhibited electrical field stimulation induced contractions of the isolated rat prostate. It is concluded that isoflavones contained in red clover are able to inhibit prostatic smooth muscle contractions in addition to their antiproliferative effects. However, the high concentrations required to observe these smooth muscle relaxant effects mean that a therapeutic benefit from this mechanism is unlikely at doses used clinically. Crown Copyright 2010. Published by Elsevier GmbH. All rights

  3. Rho-kinase inhibitors augment the inhibitory effect of propofol on rat bronchial smooth muscle contraction.

    PubMed

    Hanazaki, Motohiko; Yokoyama, Masataka; Morita, Kiyoshi; Kohjitani, Atsushi; Sakai, Hiroyasu; Chiba, Yoshihiko; Misawa, Miwa

    2008-06-01

    Airway smooth muscle contraction is not caused by the increase in intracellular Ca(2+) ([Ca(2+)](i)) alone because agonist stimulation increases tension at the same [Ca(2+)](i) (increase in Ca(2+) sensitivity). The small G protein Rho A and Rho-kinase (ROCK) play important roles in the regulation of Ca(2+) sensitivity. In this study, we investigated the effects of three ROCK inhibitors (fasudil, Y-27632, and H-1152) on rat airway smooth muscle contraction and the effects of ROCK inhibitors on propofol-induced bronchodilatory effects. Ring strips from intrapulmonary bronchus of male Wistar rats were placed in 400-microL organ baths containing Krebs-Henseleit solution. After obtaining stable contraction with 30 microM acetylcholine, (1) propofol (1 microM-1 mM) was cumulatively applied; (2) cumulative doses of Y-27632 (0.01-300 microM), fasudil (0.01-100 microM), or H-1152 (0.01-100 microM) were applied; (3) propofol (1 microM-1 mM), with Y-27632, fasudil or H-1152 (0.03 microM or 0.1 microM), was cumulatively applied. (1) Propofol produced concentration-dependent relaxation of rat bronchial smooth muscle. (2) All ROCK inhibitors produced concentration-dependent relaxation. (3) 0.03 microM Y-27632 and fasudil had no significant effect on the concentration-response curve for propofol, while 0.1 microM of both agents significantly shifted concentration-response curves to the left and decreased EC(50). H-1152 (both 0.03 microM and 0.1 microM) significantly sifted the concentration-response curve for propofol to the left and decreased EC(50). ROCK inhibitors, especially H-1152, can attenuate the contraction of rat airway smooth muscle. The combined use of ROCK inhibitors and propofol causes greater relaxation.

  4. Endothelium-dependent vasodilatory signalling modulates α1 -adrenergic vasoconstriction in contracting skeletal muscle of humans.

    PubMed

    Hearon, Christopher M; Kirby, Brett S; Luckasen, Gary J; Larson, Dennis G; Dinenno, Frank A

    2016-12-15

    'Functional sympatholysis' describes the ability of contracting skeletal muscle to attenuate sympathetic vasoconstriction, and is critical to ensure proper blood flow and oxygen delivery to metabolically active skeletal muscle. The signalling mechanism responsible for sympatholysis in healthy humans is unknown. Evidence from animal models has identified endothelium-derived hyperpolarization (EDH) as a potential mechanism capable of attenuating sympathetic vasoconstriction. In this study, increasing endothelium-dependent signalling during exercise significantly enhanced the ability of contracting skeletal muscle to attenuate sympathetic vasoconstriction in humans. This is the first study in humans to identify endothelium-dependent regulation of sympathetic vasoconstriction in contracting skeletal muscle, and specifically supports a role for EDH-like vasodilatory signalling. Impaired functional sympatholysis is a common feature of cardiovascular ageing, hypertension and heart failure, and thus identifying fundamental mechanisms responsible for sympatholysis is clinically relevant. Stimulation of α-adrenoceptors elicits vasoconstriction in resting skeletal muscle that is blunted during exercise in an intensity-dependent manner. In humans, the underlying mechanisms remain unclear. We tested the hypothesis that stimulating endothelium-dependent vasodilatory signalling will enhance the ability of contracting skeletal muscle to blunt α 1 -adrenergic vasoconstriction. Changes in forearm vascular conductance (FVC; Doppler ultrasound, brachial intra-arterial pressure via catheter) to local intra-arterial infusion of phenylephrine (PE; α 1 -adrenoceptor agonist) were calculated during (1) infusion of the endothelium-dependent vasodilators acetylcholine (ACh) and adenosine triphosphate (ATP), the endothelium-independent vasodilator (sodium nitroprusside, SNP), or potassium chloride (KCl) at rest; (2) mild or moderate intensity handgrip exercise; and (3) combined mild

  5. Adenosine A1 receptors link to smooth muscle contraction via CYP4a, protein kinase C-α, and ERK1/2.

    PubMed

    Kunduri, Swati S; Mustafa, S Jamal; Ponnoth, Dovenia S; Dick, Gregory M; Nayeem, Mohammed A

    2013-07-01

    Adenosine A1 receptor (A1AR) activation contracts smooth muscle, although signaling mechanisms are not thoroughly understood. Activation of A1AR leads to metabolism of arachidonic acid, including the production of 20-hydroxyeicosatetraenoic acid (20-HETE) by cytochrome P4504a (CYP4a). The 20-HETE can activate protein kinase C-α (PKC-α), which crosstalks with extracellular signal-regulated kinase (ERK1/2) pathway. Both these pathways can regulate smooth muscle contraction, we tested the hypothesis that A1AR contracts smooth muscle through a pathway involving CYP4a, PKC-α, and ERK1/2. Experiments included isometric tension recordings of aortic contraction and Western blots of signaling molecules in wild type (WT) and A1AR knockout (A1KO) mice. Contraction to the A1-selective agonist 2-chloro-N cyclopentyladenosine (CCPA) was absent in A1KO mice aortae, indicating the contractile role of A1AR. Inhibition of CYP4a (HET0016) abolished 2-chloro-N cyclopentyladenosine-induced contraction in WT aortae, indicating a critical role for 20-HETE. Both WT and A1KO mice aortae contracted in response to exogenous 20-HETE. Inhibition of PKC-α (Gö6976) or ERK1/2 (PD98059) attenuated 20-HETE-induced contraction equally, suggesting that ERK1/2 is downstream of PKC-α. Contractions to exogenous 20-HETE were significantly less in A1KO mice; reduced protein levels of PKC-α, p-ERK1/2, and total ERK1/2 supported this observation. Our data indicate that A1AR mediates smooth muscle contraction via CYP4a and a PKC-α-ERK1/2 pathway.

  6. Neuronally mediated contraction responses of guinea-pig stomach smooth muscle preparations: modification by benzamide derivatives does not reflect a dopamine antagonist action.

    PubMed

    Costall, B; Naylor, R J; Tan, C C

    1984-06-15

    The actions of the substituted benzamide derivatives metoclopramide, clebopride, YM-09151-2, tiapride, (+)- and (-)-sulpiride and (+)- and (-)-sultopride, and the dopamine antagonists haloperidol and domperidone, were studied on the responses to field stimulation (0.125-10 Hz) of smooth muscle strips taken from cardia, fundus, body and antral regions of the longitudinal and circular muscle of guinea-pig stomach. Field stimulation of the longitudinal strips caused contraction responses which were antagonised by atropine (but not by prazosin, yohimbine, propranolol or methysergide) to indicate a muscarinic cholinergic involvement. Antagonism of the contractions revealed or enhanced relaxation responses mediated via unidentified mechanisms (resistant to cholinergic and adrenergic antagonists). Metoclopramide enhanced the field stimulation-induced contractions of the stomach smooth muscle preparations via atropine sensitive mechanisms but failed to attenuate the field stimulation-induced relaxation responses. Clebopride's action closely followed that of metoclopramide but YM-09151-2 only enhanced the contraction responses of the longitudinal muscle preparations. Other dopamine antagonists, (+)- and (-)-sulpiride, (+)- and (-)-sultopride, tiapride, haloperidol and domperidone failed to facilitate contraction to field stimulation of any stomach tissue. Thus, the actions of metoclopramide, clebopride and YM-09151-2 to facilitate contraction to field stimulation of stomach smooth muscle are mediated via a muscarinic cholinergic mechanism and are not the consequence of an antagonism at any recognisable dopamine receptor.

  7. Local small airway epithelial injury induces global smooth muscle contraction and airway constriction

    PubMed Central

    Zhou, Jian; Alvarez-Elizondo, Martha B.; Botvinick, Elliot

    2012-01-01

    Small airway epithelial cells form a continuous sheet lining the conducting airways, which serves many functions including a physical barrier to protect the underlying tissue. In asthma, injury to epithelial cells can occur during bronchoconstriction, which may exacerbate airway hyperreactivity. To investigate the role of epithelial cell rupture in airway constriction, laser ablation was used to precisely rupture individual airway epithelial cells of small airways (<300-μm diameter) in rat lung slices (∼250-μm thick). Laser ablation of single epithelial cells using a femtosecond laser reproducibly induced airway contraction to ∼70% of the original cross-sectional area within several seconds, and the contraction lasted for up to 40 s. The airway constriction could be mimicked by mechanical rupture of a single epithelial cell using a sharp glass micropipette but not with a blunt glass pipette. These results suggest that soluble mediators released from the wounded epithelial cell induce global airway contraction. To confirm this hypothesis, the lysate of primary human small airway epithelial cells stimulated a similar airway contraction. Laser ablation of single epithelial cells triggered a single instantaneous Ca2+ wave in the epithelium, and multiple Ca2+ waves in smooth muscle cells, which were delayed by several seconds. Removal of extracellular Ca2+ or decreasing intracellular Ca2+ both blocked laser-induced airway contraction. We conclude that local epithelial cell rupture induces rapid and global airway constriction through release of soluble mediators and subsequent Ca2+-dependent smooth muscle shortening. PMID:22114176

  8. Assessment of bioelectrical activity of synergistic muscles during pelvic floor muscles activation in postmenopausal women with and without stress urinary incontinence: a preliminary observational study

    PubMed Central

    Ptaszkowski, Kuba; Paprocka-Borowicz, Małgorzata; Słupska, Lucyna; Bartnicki, Janusz; Dymarek, Robert; Rosińczuk, Joanna; Heimrath, Jerzy; Dembowski, Janusz; Zdrojowy, Romuald

    2015-01-01

    Objective Muscles such as adductor magnus (AM), gluteus maximus (GM), rectus abdominis (RA), and abdominal external and internal oblique muscles are considered to play an important role in the treatment of stress urinary incontinence (SUI), and the relationship between contraction of these muscles and pelvic floor muscles (PFM) has been established in previous studies. Synergistic muscle activation intensifies a woman’s ability to contract the PFM. In some cases, even for continent women, it is not possible to fully contract their PFM without involving the synergistic muscles. The primary aim of this study was to assess the surface electromyographic activity of synergistic muscles to PFM (SPFM) during resting and functional PFM activation in postmenopausal women with and without SUI. Materials and methods This study was a preliminary, prospective, cross-sectional observational study and included volunteers and patients who visited the Department and Clinic of Urology, University Hospital in Wroclaw, Poland. Forty-two patients participated in the study and were screened for eligibility criteria. Thirty participants satisfied the criteria and were categorized into two groups: women with SUI (n=16) and continent women (n=14). The bioelectrical activity of PFM and SPFM (AM, RA, GM) was recorded with a surface electromyographic instrument in a standing position during resting and functional PFM activity. Results Bioelectrical activity of RA was significantly higher in the incontinent group than in the continent group. These results concern the RA activity during resting and functional PFM activity. The results for other muscles showed no significant difference in bioelectrical activity between groups. Conclusion In women with SUI, during the isolated activation of PFM, an increased synergistic activity of RA muscle was observed; however, this activity was not observed in asymptomatic women. This may indicate the important accessory contribution of these muscles in the

  9. Assessment of bioelectrical activity of synergistic muscles during pelvic floor muscles activation in postmenopausal women with and without stress urinary incontinence: a preliminary observational study.

    PubMed

    Ptaszkowski, Kuba; Paprocka-Borowicz, Małgorzata; Słupska, Lucyna; Bartnicki, Janusz; Dymarek, Robert; Rosińczuk, Joanna; Heimrath, Jerzy; Dembowski, Janusz; Zdrojowy, Romuald

    2015-01-01

    Muscles such as adductor magnus (AM), gluteus maximus (GM), rectus abdominis (RA), and abdominal external and internal oblique muscles are considered to play an important role in the treatment of stress urinary incontinence (SUI), and the relationship between contraction of these muscles and pelvic floor muscles (PFM) has been established in previous studies. Synergistic muscle activation intensifies a woman's ability to contract the PFM. In some cases, even for continent women, it is not possible to fully contract their PFM without involving the synergistic muscles. The primary aim of this study was to assess the surface electromyographic activity of synergistic muscles to PFM (SPFM) during resting and functional PFM activation in postmenopausal women with and without SUI. This study was a preliminary, prospective, cross-sectional observational study and included volunteers and patients who visited the Department and Clinic of Urology, University Hospital in Wroclaw, Poland. Forty-two patients participated in the study and were screened for eligibility criteria. Thirty participants satisfied the criteria and were categorized into two groups: women with SUI (n=16) and continent women (n=14). The bioelectrical activity of PFM and SPFM (AM, RA, GM) was recorded with a surface electromyographic instrument in a standing position during resting and functional PFM activity. Bioelectrical activity of RA was significantly higher in the incontinent group than in the continent group. These results concern the RA activity during resting and functional PFM activity. The results for other muscles showed no significant difference in bioelectrical activity between groups. In women with SUI, during the isolated activation of PFM, an increased synergistic activity of RA muscle was observed; however, this activity was not observed in asymptomatic women. This may indicate the important accessory contribution of these muscles in the mechanism of continence.

  10. Muscle force loss and soreness subsequent to maximal eccentric contractions depend on the amount of fascicle strain in vivo.

    PubMed

    Guilhem, G; Doguet, V; Hauraix, H; Lacourpaille, L; Jubeau, M; Nordez, A; Dorel, S

    2016-06-01

    Defining the origins of muscle injury has important rehabilitation and exercise applications. However, current knowledge of muscle damage mechanics in human remains unclear in vivo. This study aimed to determine the relationships between muscle-tendon unit mechanics during maximal eccentric contractions and the extent of subsequent functional impairments induced by muscle damage. The length of the muscle-tendon unit, fascicles and tendinous tissues was continuously measured on the gastrocnemius medialis using ultrasonography, in time with torque, during 10 sets of 30 maximal eccentric contractions of plantar flexors at 45°s(-1) , in seventeen participants. Muscle-tendon unit, fascicles and tendinous tissues were stretched up to 4.44 ± 0.33 cm, 2.31 ± 0.64 cm and 1.92 ± 0.61 cm respectively. Fascicle stretch length, lengthening amplitude and negative fascicle work beyond slack length were significantly correlated with the force decrease 48 h post-exercise (r = 0.51, 0.47 and 0.68, respectively; P < 0.05). This study demonstrates that the strain applied to human muscle fibres during eccentric contractions strongly influences the magnitude of muscle damage in vivo. Achilles tendon compliance decreases the amount of strain, while architectural gear ratio may moderately contribute to attenuating muscle fascicle lengthening and hence muscle damage. Further studies are necessary to explore the impact of various types of task to fully understand the contribution of muscle-tendon interactions during active lengthening to muscle damage. © 2016 Scandinavian Physiological Society. Published by John Wiley & Sons Ltd.

  11. Voluntary physical activity protects from susceptibility to skeletal muscle contraction-induced injury but worsens heart function in mdx mice.

    PubMed

    Hourdé, Christophe; Joanne, Pierre; Medja, Fadia; Mougenot, Nathalie; Jacquet, Adeline; Mouisel, Etienne; Pannerec, Alice; Hatem, Stéphane; Butler-Browne, Gillian; Agbulut, Onnik; Ferry, Arnaud

    2013-05-01

    It is well known that inactivity/activity influences skeletal muscle physiological characteristics. However, the effects of inactivity/activity on muscle weakness and increased susceptibility to muscle contraction-induced injury have not been extensively studied in mdx mice, a murine model of Duchenne muscular dystrophy with dystrophin deficiency. In the present study, we demonstrate that inactivity (ie, leg immobilization) worsened the muscle weakness and the susceptibility to contraction-induced injury in mdx mice. Inactivity also mimicked these two dystrophic features in wild-type mice. In contrast, we demonstrate that these parameters can be improved by activity (ie, voluntary wheel running) in mdx mice. Biochemical analyses indicate that the changes induced by inactivity/activity were not related to fiber-type transition but were associated with altered expression of different genes involved in fiber growth (GDF8), structure (Actg1), and calcium homeostasis (Stim1 and Jph1). However, activity reduced left ventricular function (ie, ejection and shortening fractions) in mdx, but not C57, mice. Altogether, our study suggests that muscle weakness and susceptibility to contraction-induced injury in dystrophic muscle could be attributable, at least in part, to inactivity. It also suggests that activity exerts a beneficial effect on dystrophic skeletal muscle but not on the heart. Copyright © 2013 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.

  12. Structural basis for the regulation of muscle contraction by troponin and tropomyosin.

    PubMed

    Galińska-Rakoczy, Agnieszka; Engel, Patti; Xu, Chen; Jung, Hyunsuk; Craig, Roger; Tobacman, Larry S; Lehman, William

    2008-06-20

    The molecular switching mechanism governing skeletal and cardiac muscle contraction couples the binding of Ca2+ on troponin to the movement of tropomyosin on actin filaments. Despite years of investigation, this mechanism remains unclear because it has not yet been possible to directly assess the structural influence of troponin on tropomyosin that causes actin filaments, and hence myosin-crossbridge cycling and contraction, to switch on and off. A C-terminal domain of troponin I is thought to be intimately involved in inducing tropomyosin movement to an inhibitory position that blocks myosin-crossbridge interaction. Release of this regulatory, latching domain from actin after Ca2+ binding to TnC (the Ca2+ sensor of troponin that relieves inhibition) presumably allows tropomyosin movement away from the inhibitory position on actin, thus initiating contraction. However, the structural interactions of the regulatory domain of TnI (the "inhibitory" subunit of troponin) with tropomyosin and actin that cause tropomyosin movement are unknown, and thus, the regulatory process is not well defined. Here, thin filaments were labeled with an engineered construct representing C-terminal TnI, and then, 3D electron microscopy was used to resolve where troponin is anchored on actin-tropomyosin. Electron microscopy reconstruction showed how TnI binding to both actin and tropomyosin at low Ca2+ competes with tropomyosin for a common site on actin and drives tropomyosin movement to a constrained, relaxing position to inhibit myosin-crossbridge association. Thus, the observations reported reveal the structural mechanism responsible for troponin-tropomyosin-mediated steric interference of actin-myosin interaction that regulates muscle contraction.

  13. Bulgarian propolis induces analgesic and anti-inflammatory effects in mice and inhibits in vitro contraction of airway smooth muscle.

    PubMed

    Paulino, Niraldo; Dantas, Andreia Pires; Bankova, Vassya; Longhi, Daniela Taggliari; Scremin, Amarilis; de Castro, Solange Lisboa; Calixto, João Batista

    2003-11-01

    Propolis is a bee product, which has long been used in folk medicine for the management of different diseases. In this study we evaluated the analgesic and anti-inflammatory effects of a standard ethanolic extract of Bulgarian propolis (Et-Blg) in mice and its in vitro effect on airway smooth muscle. Et-Blg inhibited acetic acid-induced abdominal contortions with an ID(50) = 7.4 +/- 0.7 mg. kg(-1). In the formalin test, the extract caused a significant reduction in pain in mice treated with 100 mg. kg(-1) Et-Blg during the neurogenic phase and for the inflammatory phase with all doses of the extract, with an ID(50) = 2.5 +/- 0.4 mg. kg(-1). Et-Blg inhibited also the capsaicin-induced ear edema in mice; however, this extract was ineffective when assessed in the tail-flick and hot-plate thermal assays. The analgesic effect of Et-Blg was associated with the inhibition of inflammatory responses and not to a simple irritation of nervous terminals. In vitro, this extract inhibited the contraction of trachea smooth muscle induced by histamine (IC(50) = 50 +/- 5 microg. mL(-1)), capsaicin (IC(50) = 26.8 +/- 3 microg. mL(-1)), 80 mM KCl (IC(50) = 27.8 +/- 3 microg. mL(-1)), and carbachol (IC(50) = 54 +/- 2 microg. mL(-1)).

  14. Mechanism of soman-induced contractions in canine tracheal smooth muscle. (Reannouncement with new availability information)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Adler, M.; Moore, D.H.; Filbert, M.G.

    1992-12-31

    The actions of the irreversible organophosphorus cholinesterase (ChE) inhibitor soman were investigated on canine trachea smooth muscle in vitro. Concentrations of soman > or - 1 nM increased the amplitude and decay of contractions elicited by electric field stimulation. The effect on decay showed a marked dependence on stimulation frequency, undergoing a 2.4-fold increase between 3 and 60 Hz. Soman also potentiated tensions due to bath applied acetylcholine (ACh). Little or no potentiation was observed for contractions elicited by carbamylcholine, an agonist that is not hydrolyzed by ChE. Concentration of soman > or - 3 nM led to the appearancemore » of sustained contractures. These contractures developed with a delayed onset and were well correlated with ChE activity. Alkylation of muscarinic receptors by propylbenzilylcholine mustard antagonized the actions of soman on both spontaneous and electrically-evoked muscle contractions. The results are consistent with a mechanism in which the toxic actions of soman are mediated by accumulation of neurally-released ACh secondary to inhibition of ChE activity. An important factor in this accumulation is suggested to be the buffering effect of the muscarinic receptors on the efflux of ACh from the neuroeffector junction. Tracheal smooth muscle, Cholinesterase inhibitors, Muscarinic receptor, Soman, Organophosphate.« less

  15. Influence of ovarian muscle contraction and oocyte growth on egg chamber elongation in Drosophila.

    PubMed

    Andersen, Darcy; Horne-Badovinac, Sally

    2016-04-15

    Organs are formed from multiple cell types that make distinct contributions to their shape. The Drosophila egg chamber provides a tractable model to dissect such contributions during morphogenesis. Egg chambers consist of 16 germ cells (GCs) surrounded by a somatic epithelium. Initially spherical, these structures elongate as they mature. This morphogenesis is thought to occur through a 'molecular corset' mechanism, whereby structural elements within the epithelium become circumferentially organized perpendicular to the elongation axis and resist the expansive growth of the GCs to promote elongation. Whether this epithelial organization provides the hypothesized constraining force has been difficult to discern, however, and a role for GC growth has not been demonstrated. Here, we provide evidence for this mechanism by altering the contractile activity of the tubular muscle sheath that surrounds developing egg chambers. Muscle hypo-contraction indirectly reduces GC growth and shortens the egg, which demonstrates the necessity of GC growth for elongation. Conversely, muscle hyper-contraction enhances the elongation program. Although this is an abnormal function for this muscle, this observation suggests that a corset-like force from the egg chamber's exterior could promote its lengthening. These findings highlight how physical contributions from several cell types are integrated to shape an organ. © 2016. Published by The Company of Biologists Ltd.

  16. Influence of ovarian muscle contraction and oocyte growth on egg chamber elongation in Drosophila

    PubMed Central

    Andersen, Darcy; Horne-Badovinac, Sally

    2016-01-01

    Organs are formed from multiple cell types that make distinct contributions to their shape. The Drosophila egg chamber provides a tractable model to dissect such contributions during morphogenesis. Egg chambers consist of 16 germ cells (GCs) surrounded by a somatic epithelium. Initially spherical, these structures elongate as they mature. This morphogenesis is thought to occur through a ‘molecular corset’ mechanism, whereby structural elements within the epithelium become circumferentially organized perpendicular to the elongation axis and resist the expansive growth of the GCs to promote elongation. Whether this epithelial organization provides the hypothesized constraining force has been difficult to discern, however, and a role for GC growth has not been demonstrated. Here, we provide evidence for this mechanism by altering the contractile activity of the tubular muscle sheath that surrounds developing egg chambers. Muscle hypo-contraction indirectly reduces GC growth and shortens the egg, which demonstrates the necessity of GC growth for elongation. Conversely, muscle hyper-contraction enhances the elongation program. Although this is an abnormal function for this muscle, this observation suggests that a corset-like force from the egg chamber's exterior could promote its lengthening. These findings highlight how physical contributions from several cell types are integrated to shape an organ. PMID:26952985

  17. Comparison of gel contraction mediated by airway smooth muscle cells from patients with and without asthma.

    PubMed

    Matsumoto, Hisako; Moir, Lyn M; Oliver, Brian G G; Burgess, Janette K; Roth, Michael; Black, Judith L; McParland, Brent E

    2007-10-01

    Exaggerated bronchial constriction is the most significant and life threatening response of patients with asthma to inhaled stimuli. However, few studies have investigated the contractility of airway smooth muscle (ASM) from these patients. The purpose of this study was to establish a method to measure contraction of ASM cells by embedding them into a collagen gel, and to compare the contraction between subjects with and without asthma. Gel contraction to histamine was examined in floating gels containing cultured ASM cells from subjects with and without asthma following overnight incubation while unattached (method 1) or attached (method 2) to casting plates. Smooth muscle myosin light chain kinase protein levels were also examined. Collagen gels containing ASM cells reduced in size when stimulated with histamine in a concentration-dependent manner and reached a maximum at a mean (SE) of 15.7 (1.2) min. This gel contraction was decreased by inhibitors for phospholipase C (U73122), myosin light chain kinase (ML-7) and Rho kinase (Y27632). When comparing the two patient groups, the maximal decreased area of gels containing ASM cells from patients with asthma was 19 (2)% (n = 8) using method 1 and 22 (3)% (n = 6) using method 2, both of which were greater than that of cells from patients without asthma: 13 (2)% (n = 9, p = 0.05) and 10 (4)% (n = 5, p = 0.024), respectively. Smooth muscle myosin light chain kinase levels were not different between the two groups. The increased contraction of asthmatic ASM cells may be responsible for exaggerated bronchial constriction in asthma.

  18. Tissue-engineering with muscle fiber fragments improves the strength of a weak abdominal wall in rats.

    PubMed

    Jangö, Hanna; Gräs, Søren; Christensen, Lise; Lose, Gunnar

    2017-02-01

    Alternative approaches to reinforce the native tissue in patients with pelvic organ prolapse (POP) are needed to improve surgical outcome. Our aims were to develop a weakened abdominal wall in a rat model to mimic the weakened vaginal wall in women with POP and then evaluate the regenerative potential of a quickly biodegradable synthetic scaffold, methoxypolyethylene glycol polylactic-co-glycolic acid (MPEG-PLGA), seeded with autologous muscle fiber fragments (MFFs) using this model. In an initial pilot study with 15 animals, significant weakening of the abdominal wall and a feasible technique was established by creating a partial defect with removal of one abdominal muscle layer. Subsequently, 18 rats were evenly divided into three groups: (1) unrepaired partial defect; (2) partial defect repaired with MPEG-PLGA; (3) partial defect repaired with MPEG-PLGA and MFFs labeled with PKH26-fluorescence dye. After 8 weeks, we performed histopathological and immunohistochemical testing, fluorescence analysis, and uniaxial biomechanical testing. Both macroscopically and microscopically, the MPEG-PLGA scaffold was fully degraded, with no signs of an inflammatory or foreign-body response. PKH26-positive cells were found in all animals from the group with added MFFs. Analysis of variance (ANOVA) showed a significant difference between groups with respect to load at failure (p = 0.028), and post hoc testing revealed that the group with MPEG-PLGA and MFFs showed a significantly higher strength than the group with MPEG-PLGA alone (p = 0.034). Tissue-engineering with MFFs seeded on a scaffold of biodegradable MPEG-PLGA might be an interesting adjunct to future POP repair.

  19. Gated /sup 31/P NMR study of tetanic contraction in rat muscle depleted of phosphocreatine

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Shoubridge, E.A.; Radda, G.K.

    1987-05-01

    Rats were fed a diet containing 1% ..beta..-guanidino-propionic acid (GPA) for 6-12 wk to deplete their muscles of phosphocreatine (PCr). Gated /sup 31/P nuclear magnetic resonance (NMR) spectra were obtained from the gastrocnemius-plantaris muscle at various time points during either a 1- or 3-s isometric tetanic contraction using a surface coil. The energy cost of a 1-s tetanus in unfatigued control rat muscle was 48.4 ..mu..mol ATP x g dry wt/sup -1/ x s/sup -1/ and was largely supplied by PCr; anaerobic glycogenolysis was negligible. In GPA-fed rats PCr was undetectable after 400 ms. This had no effect on initialmore » force generated per gram, which was not significantly different from controls. Developed tension in a 3-s tetanus in GPA-fed rats could be divided into a peak phase (duration 0.8-0.9 s) and a plateau phase (65% peak tension) in which PCr was undetectable and the (ATP) was < 20% of that in control muscle. Energy from glycogenolysis was sufficient to maintain force generation at this submaximal level. Mean net glycogen utilization per 3-s tetanus was 78% greater than in control muscle. However, the observed decrease in intracellular pH was less than that expected from energy budget calculations, suggesting either increased buffering capacity or modulation of ATP hydrolysis in the muscles of GPA-fed rats. The results demonstrate that the transport role of PCr is not essential in contracting muscle in GPA-fed rats. PCr is probably important in this regard in the larger fibers of control muscle. Although fast-twitch muscles depleted of PCr have nearly twice the glycogen reserves of control muscle, glycogenolysis is limited in its capacity to fill the role of PCr as an energy buffer under conditions of maximum ATP turnover.« less

  20. Genetic screen in Drosophila muscle identifies autophagy-mediated T-tubule remodeling and a Rab2 role in autophagy.

    PubMed

    Fujita, Naonobu; Huang, Wilson; Lin, Tzu-Han; Groulx, Jean-Francois; Jean, Steve; Nguyen, Jen; Kuchitsu, Yoshihiko; Koyama-Honda, Ikuko; Mizushima, Noboru; Fukuda, Mitsunori; Kiger, Amy A

    2017-01-07

    Transverse (T)-tubules make-up a specialized network of tubulated muscle cell membranes involved in excitation-contraction coupling for power of contraction. Little is known about how T-tubules maintain highly organized structures and contacts throughout the contractile system despite the ongoing muscle remodeling that occurs with muscle atrophy, damage and aging. We uncovered an essential role for autophagy in T-tubule remodeling with genetic screens of a developmentally regulated remodeling program in Drosophila abdominal muscles. Here, we show that autophagy is both upregulated with and required for progression through T-tubule disassembly stages. Along with known mediators of autophagosome-lysosome fusion, our screens uncovered an unexpected shared role for Rab2 with a broadly conserved function in autophagic clearance. Rab2 localizes to autophagosomes and binds to HOPS complex members, suggesting a direct role in autophagosome tethering/fusion. Together, the high membrane flux with muscle remodeling permits unprecedented analysis both of T-tubule dynamics and fundamental trafficking mechanisms.