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Sample records for abdominal muscle contraction

  1. Assessment of Abdominal Muscle's Maximal Force of Contraction Using Surface EMG in Inguinal Hernia Patients

    PubMed Central

    Sreenath, G. S.; Subramanian, Senthil Kumar

    2016-01-01

    Introduction Reduction in abdominal muscle’s strength has been implicated in the development of inguinal hernia. Patients with inguinal hernia on one side are shown to be at higher risk of developing inguinal hernia on the other side. Aim To assess the abdominal muscle strength in inguinal hernia subjects using surface Electromyography (EMG) and compare it with healthy controls. Materials and Methods This is a cross-sectional study involving only male subjects. Abdominal (Inguinal) hernia subjects without any known complications were recruited from surgery department and the accompanying healthy individuals were taken as control (Control, n=44, inguinal hernia subjects, n=43). The subjects were asked to perform maximal contraction for three seconds targeting external and internal oblique muscles of right and left sides separately. Motor unit potentials were recorded using surface EMG for individual muscles on both sides during maximal contraction. The maximum amplitude of the motor unit potentials obtained was considered as the strength of the respective muscle. Results In control group, there was no significant difference in strength of external and internal oblique muscles between the two sides. Strength of external and internal oblique muscles of both herniated and unaffected side was reduced in inguinal hernia subjects as compared to healthy controls. Further, the muscle strength of herniated side was less as compared to unaffected side in the inguinal hernia subjects. Conclusion Abdominal muscle strength is reduced in hernia subjects and even the apparently normal side strength is less as compared to controls. This should be considered while performing corrective surgeries in inguinal hernia subjects. PMID:28208924

  2. Comparison of changes in the contraction of the lateral abdominal muscles between the abdominal drawing-in maneuver and breathe held at the maximum expiratory level.

    PubMed

    Ishida, Hiroshi; Hirose, Ryohei; Watanabe, Susumu

    2012-10-01

    The abdominal drawing-in maneuver (ADIM) is commonly used as a fundamental component of lumbar stabilization training programs. One potential limitation of lumbar stabilization programs is that it can be difficult and time consuming to train people to perform the ADIM. The transverse abdominis (TrA), internal oblique (IO), and external oblique (EO) muscles are the most powerful muscles involved in expiration. However, little is known about the differences in the recruitment of the abdominal muscles between the ADIM and breathe held at maximum expiratory level (maximum expiration). The thickness of the TrA and IO muscles was measured by ultrasound imaging, and the activity of the EO muscle was measured by electromyography (EMG) in 33 healthy male performing the ADIM and maximum expiration. Maximum expiration produced a significant increase in the thickness of the TrA and IO muscles compared to the ADIM (p < 0.001). The EMG activity of the EO muscle was significantly higher during maximum expiration than during the ADIM (p < 0.001). The intensity of the EMG activity of the EO muscle was approximately 30% of the maximal voluntary contraction during maximum expiration. Thus, maximum expiration may be an effective method for training of co-activation of the lateral abdominal muscles.

  3. 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

  4. The effects of upper extremity task training with symmetric abdominal muscle contraction on trunk stability and balance in chronic stroke patients

    PubMed Central

    Lee, Je-hyeok; Choi, Jong-duk

    2017-01-01

    [Purpose] The purpose of this study is to examine the effects of upper extremity task training employing the bracing method on the trunk control and balance of stroke patients. [Subjects and Methods] The subjects were 46 stroke patients whose strokes had occurred six months or more prior to the study. The subjects were divided into two groups. One group underwent upper extremity task training with symmetric abdominal muscle contraction (bracing) applied. The other group simply underwent upper extremity task training, without bracing. [Results] The experimental group’s Trunk Impairment Scale (TIS) significantly increased after the intervention, whereas the control group did not see any significant difference. There was significant improvement in balance after the intervention in both the experimental group and the control group. According to the between-group comparisons, the improvements in the experimental group were significantly greater in the control group, except in the Postural Assessment Scale (PASS). [Conclusion] Based on the results of this study, upper extremity task exercises with symmetric abdominal muscle contraction, conducted as part of adult hemiplegic patients’ trunk stabilization exercises, can be applied to a diverse range of hemiplegic patients and implemented as an exercise program after discharge from hospital. PMID:28356639

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

    PubMed Central

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

    2017-01-01

    [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. PMID:28265140

  6. Ultrasound assessment of transversus abdominis muscle contraction ratio during abdominal hollowing: a useful tool to distinguish between patients with chronic low back pain and healthy controls?

    PubMed

    Pulkovski, N; Mannion, A F; Caporaso, F; Toma, V; Gubler, D; Helbling, D; Sprott, H

    2012-08-01

    Spine stabilisation exercises, in which patients are taught to preferentially activate the transversus abdominus (TrA) during "abdominal hollowing" (AH), are a popular treatment for chronic low back pain (cLBP). The present study investigated whether performance during AH differed between cLBP patients and controls to an extent that would render it useful diagnostic tool. 50 patients with cLBP (46.3 ± 12.5 years) and 50 healthy controls (43.6 ± 12.7 years) participated in this case-control study. They performed AH in hook-lying. Using M-mode ultrasound, thicknesses of TrA, and obliquus internus and externus were determined at rest and during 5 s AH (5 measures each body side). The TrA contraction-ratio (TrA-CR) (TrA contracted/rest) and the ability to sustain the contraction [standard deviation (SD) of TrA thickness during the stable phase of the hold] were investigated. There were no significant group differences for the absolute muscle thicknesses at rest or during AH, or for the SD of TrA thickness. There was a small but significant difference between the groups for TrA-CR: cLBP 1.35 ± 0.14, controls 1.44 ± 0.24 (p < 0.05). However, Receiver Operator Characteristics (ROC) analysis revealed a poor and non-significant ability of TrA-CR to discriminate between cLBP patients and controls on an individual basis (ROC area under the curve, 0.60 [95% CI 0.495; 0.695], p = 0.08). In the patient group, TrA-CR showed a low but significant correlation with Roland Morris score (Spearman Rho = 0.328; p = 0.02). In conclusion, the difference in group mean values for TrA-CR was small and of uncertain clinical relevance. Moreover, TrA-CR showed a poor ability to discriminate between control and cLBP subjects on an individual basis. We conclude that the TrA-CR during abdominal hollowing does not distinguish well between patients with chronic low back pain and healthy controls.

  7. Trunk Muscle Activities During Abdominal Bracing: Comparison Among Muscles and Exercises

    PubMed Central

    Maeo, Sumiaki; Takahashi, Takumi; Takai, Yohei; Kanehisa, Hiroaki

    2013-01-01

    Abdominal bracing is often adopted in fitness and sports conditioning programs. However, there is little information on how muscular activities during the task differ among the muscle groups located in the trunk and from those during other trunk exercises. The present study aimed to quantify muscular activity levels during abdominal bracing with respect to muscle- and exercise-related differences. Ten healthy young adult men performed five static (abdominal bracing, abdominal hollowing, prone, side, and supine plank) and five dynamic (V- sits, curl-ups, sit-ups, and back extensions on the floor and on a bench) exercises. Surface electromyogram (EMG) activities of the rectus abdominis (RA), external oblique (EO), internal oblique (IO), and erector spinae (ES) muscles were recorded in each of the exercises. The EMG data were normalized to those obtained during maximal voluntary contraction of each muscle (% EMGmax). The % EMGmax value during abdominal bracing was significantly higher in IO (60%) than in the other muscles (RA: 18%, EO: 27%, ES: 19%). The % EMGmax values for RA, EO, and ES were significantly lower in the abdominal bracing than in some of the other exercises such as V-sits and sit-ups for RA and EO and back extensions for ES muscle. However, the % EMGmax value for IO during the abdominal bracing was significantly higher than those in most of the other exercises including dynamic ones such as curl-ups and sit-ups. These results suggest that abdominal bracing is one of the most effective techniques for inducing a higher activation in deep abdominal muscles, such as IO muscle, even compared to dynamic exercises involving trunk flexion/extension movements. Key Points Trunk muscle activities during abdominal bracing was examined with regard to muscle- and exercise-related differences. Abdominal bracing preferentially activates internal oblique muscles even compared to dynamic exercises involving trunk flexion/extension movements. Abdominal bracing should be

  8. Insertional action of the abdominal muscles in rabbits and dogs.

    PubMed

    D'Angelo, E; Prandi, E; Robatto, F; Petitjean, M; Bellemare, F

    1996-07-01

    The insertional action of the abdominal muscles was studied in supine anesthetized, apneic rabbits and dogs by comparing the changes in esophageal pressure (Pes), upper and lower rib cage circumference (Cru,u and Crc,I) and lung volume (VL) in response to electrical stimulation of all abdominal muscles before and after evisceration. In eviscerated animals, abdominal muscle contraction increased Pes and decreased both VL and Cre,I, but had no effect on Crc,u. Maximal responses were obtained at submaximal intensities of stimulation, and became larger with increasing lung volume. Relative to the vital capacity in intact animals, maximal delta VL for stimulation performed at FRC and TLC were 7.2 +/- 2.9(SD) and 39.5 +/- 7% in rabbits, and 6.3 +/- 0.8 and 18.3 +/- 5.9% in dogs, respectively. Relative to the changes in lung volume occurring with maximal contraction of the abdominal muscles in intact animals, the values of delta VL observed in the eviscerated animals amounted to approximately 35 and approximately 45% for stimulation performed at FRC and TLC, respectively. Hence, abdominal muscles exert substantial insertional action on the lower rib cage that can result in appreciable lung deflationary effects, particularly at elevated lung volumes.

  9. Acting Out Muscle Contraction.

    ERIC Educational Resources Information Center

    Hudson, Margaret

    2003-01-01

    Describes a science activity that can be implemented into anatomy and physiology courses that demonstrates the interactions between action and myosin, the roles of sodium and calcium ions in the regulation of contraction, and the functions of the plasma membrane and the sarcoplasmic reticulum. (YDS)

  10. 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…

  11. Fiber architecture of canine abdominal muscles.

    PubMed

    Boriek, Aladin M; Ortize, Jaime; Zhu, Deshen

    2002-02-01

    During respiration, abdominal muscles experience loads, not only in the muscle-fiber direction but also transverse to the fibers. We wondered whether the abdominal muscles exhibit a fiber architecture that is similar to the diaphragm muscle, and, therefore, we chose two adjacent muscles: the internal oblique (IO), with about the same muscle length as the diaphragm, and the transverse abdominis (TA), which is twice as long as the diaphragm. First, we used acetylcholinesterase staining to examine the distribution of neuromuscular junctions on both surfaces of the TA and IO muscles in six dogs. A maximum of four irregular bands of neuromuscular junctions crossed the IO, and as many as six bands crossed the TA, which is consistent with a discontinuous fiber architecture. In six additional dogs, we examined fiber architecture of these muscles by microdissecting 103 fascicles from the IO and 139 from the TA. Each fascicle contained between 20 and 30 muscle fibers. The mean length of nonspanning fibers (NSF) ranged from 2.8 +/- 0.3 cm in the IO to 4.3 +/- 0.5 cm in the TA, and the mean length of spanning fibers ranged from 4.3 +/- 0.5 cm in the IO to 7.6 +/- 1.4 cm in the TA. NSF accounted for 89.6 +/- 1.5% of all fibers dissected from the IO and 99.1 +/- 0.2% of all fibers dissected from the TA. The percentage of NSF with both ends tapered was 6.2 +/- 1.0 and 41.0 +/- 2.3% for IO and TA, respectively. These data show that fiber architecture in either IO or TA is discontinuous, with much more short-tapered fibers in the TA than in the IO. When abdominal muscles are submaximally activated, as during both normal expiration and maximal expiratory efforts, muscle force could be transmitted to the cell membrane and to the extracellular intramuscular connective tissue by shear linkage, presumably via structural transmembrane proteins.

  12. Calcium regulation of muscle contraction.

    PubMed Central

    Szent-Györgyi, A G

    1975-01-01

    Calcium triggers contraction by reaction with regulatory proteins that in the absence of calcium prevent interaction of actin and myosin. Two different regulatory systems are found in different muscles. In actin-linked regulation troponin and tropomyosin regulate actin by blocking sites on actin required for complex formation with myosin; in myosin-linked regulation sites on myosin are blocked in the absence of calcium. The major features of actin control are as follows: there is a requirement for tropomyosin and for a troponin complex having three different subunits with different functions; the actin displays a cooperative behavior; and a movement of tropomyosin occurs controlled by the calcium binding on troponin. Myosin regulation is controlled by a regulatory subunit that can be dissociated in scallop myosin reversibly by removing divalent cations with EDTA. Myosin control can function with pure actin in the absence of tropomyosin. Calcium binding and regulation of molluscan myosins depend on the presence of regulatory light chains. It is proposed that the light chains function by sterically blocking myosin sites in the absence of calcium, and that the "off" state of myosin requires cooperation between the two myosin heads. Both myosin control and actin control are widely distributed in different organisms. Many invertebrates have muscles with both types of regulation. Actin control is absent in the muscles of molluscs and in several minor phyla that lack troponin. Myosin control is not found in striated vertebrate muscles and in the fast muscles of crustacean decapods, although regulatory light chains are present. While in vivo myosin control may not be excluded from vertebrate striated muscles, myosin control may be absent as a result of mutations of the myosin heavy chain. PMID:806311

  13. Innovative exercise device for the abdominal trunk muscles: An early validation study

    PubMed Central

    Murakami, Hideki; Inaki, Anri; Mochizuki, Takafumi; Demura, Satoru; Nakase, Junsuke; Yoshioka, Katsuhito; Yokogawa, Noriaki; Igarashi, Takashi; Takahashi, Naoki; Yonezawa, Noritaka; Kinuya, Seigo; Tsuchiya, Hiroyuki

    2017-01-01

    Background Exercise is one of the few treatments that provide significant improvements in chronic low back pain (CLBP). We developed an innovative exercise device for abdominal trunk muscles. This device can be used in a sitting or standing position and contains a built-in system to measure abdominal trunk muscle strength. We examined whether subjects can adequately use the device to perform the exercises and measure their abdominal trunk muscle strength. Methods We collected data on the body height, body weight, body mass index, and girth of 30 healthy male volunteers, and measured their grip power and trunk extensor muscle strength using a dynamometer. The volunteers performed a sit-up test as an indicator of trunk flexor muscle strength, and we measured their abdominal muscle strength using the device. We then evaluated the correlations between abdominal trunk muscle strength and anthropometric parameters as well as the strength of other muscles. In subsequent tests, 5 of the 30 subjects participated in two positron emission tomography (PET) series consisting of examinations after a resting period (control study) and during exercise (exercise study). For the exercise study, the subjects performed 2 sets of exercises for 20 minutes using the device before and after an injection of 18F-fluorodeoxyglucose (FDG). PET-computed tomography images were obtained 60 minutes after FDG injection in each study. We compared the skeletal muscle metabolism of the participants in both studies using the standardized uptake value. Results The muscle strength measured by the device and the 30-second sit-up frequency were correlated. FDG accumulation within the diaphragm and abdominal rectus muscles was significantly higher in the exercise study. Conclusion Our innovative exercise device facilitates a coordinated contraction of the abdominal trunk muscles at the anterior aspect and the roof of the core, and enables subjects to measure the strength of these muscles. PMID:28235060

  14. Why Do Abdominal Muscles Sometimes Separate during Pregnancy?

    MedlinePlus

    ... Lifestyle Pregnancy week by week Why do abdominal muscles sometimes separate during pregnancy? Answers from Roger W. ... D. During pregnancy, the growing uterus stretches the muscles in the abdomen. This can cause the two ...

  15. Load compensating responses of human abdominal muscles

    PubMed Central

    Lansing, R. W.; Meyerink, L.

    1981-01-01

    1. We studied abdominal muscle responses to positive pressure loads applied suddenly to the external airway while subjects held a constant lung volume against steady pressure. The pre-loading holding pressure was 6 cm H2O, and the loading pressures were 6 or 12 cm H2O lasting for 2 sec. 2. Surface electromyograms (e.m.g.) were recorded over the internal oblique, external oblique, and rectus abdominis muscles. The latency and pattern of the e.m.g. reactions were studied by measuring the raw record for each loading trial, and by averaging the rectified e.m.g. for many trials. 3. No responses were obtained if subjects were instructed not to respond to the loads. When instructed and trained to maintain their pre-load position in spite of the load, a two-phase compensatory response was found. The initial response (phase I) was 100-300 msec in duration; it was followed by a continuous e.m.g. discharge (phase II) which continued to the offset of the pressure load. Subjects were also trained to make a single respiratory effort as quickly as possible after the load onset or after just an auditory stimulus. These were simple reaction time tasks of a traditional kind and the e.m.g. responses elicited were single, brief bursts. 4. For all subjects and experimental conditions the e.m.g. response of the internal oblique occurred first, followed by the external oblique and then the rectus abdominis. For the `maintain position' task, phase I latencies (internal oblique) averaged 66-90 msec for individual subjects, but for single trials with optimal conditions of practice and preparatory intervals these ranged from 42 to 110 msec with a third of the reactions occurring within 50-60 msec. 5. The latencies for reaction time responses to loading were about 6 msec shorter than the phase I latencies. The latency distributions for the two types of responses were similar, and both were affected to the same degree by practice, and changing the length and variability of the preparatory

  16. Abdominal muscle activity according to knee joint angle during sit-to-stand

    PubMed Central

    Eom, Juri; Rhee, Min-Hyung; Kim, Laurentius Jongsoon

    2016-01-01

    [Purpose] This study assessed the activity of the abdominal muscles according to the angle of the knee joints during sit-to-stand. [Subjects and Methods] Thirty healthy adult males participated in this study. Subjects initiated sit-to-stand at knee joint angles of 60°, 90°, or 120°. An electromyography system was used to measure the maximum voluntary isometric contraction of the rectus abdominis, external oblique, and internal oblique and transverse abdominis muscles. [Results] Percent contraction differed significantly among the three knee joint angles, most notably for the internal oblique and transverse abdominis muscles. [Conclusion] Wider knee joint angles more effectively activate the abdominal muscles, especially those in the deep abdomen, than do narrower angles. PMID:27390431

  17. Lateral abdominal muscle size at rest and during abdominal drawing-in manoeuvre in healthy adolescents.

    PubMed

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

    2015-02-01

    Lateral abdominal wall muscles in children and adolescents have not been characterised to date. In the present report, we examined the reliability of the ultrasound measurement and thickness of the oblique external muscle (OE), oblique internal muscle (OI) and transverse abdominal muscle (TrA) at rest and during abdominal drawing-in manoeuvre (ADIM) on both sides of the body in healthy adolescents. We also determined possible differences between boys and girls and defined any factors-such as body mass, height and BMI-that may affect the thickness of the abdominal muscles. B-mode ultrasound was used to assess OE, OI and TrA on both sides of the body in the supine position. Ultrasound measurements at rest and during ADIM were reliable in this age group (ICC3,3 > 0.92). OI was always the thickest and TrA the thinnest muscle on both sides of the body. In this group, an identical pattern of the contribution of the individual muscles to the structure of the lateral abdominal wall (OI > OE > TrA) was observed. At rest and during ADIM, no statistically significant side-to-side differences were demonstrated in either gender. The body mass constitutes between 30% and <50% of the thickness differences in all muscles under examination at rest and during ADIM. The structure of lateral abdominal wall in adolescents is similar to that of adults. During ADIM, the abdominal muscles in adolescents react similarly to those in adults. This study provided extensive information regarding the structure of the lateral abdominal wall in healthy adolescents.

  18. Cobalt contraction of vascular smooth muscle

    SciTech Connect

    Dominiczak, A.; Clyde, E.; Bohr, D. )

    1991-03-11

    Although it has been reported that cobalt causes contraction of vascular smooth muscle, the mechanism responsible for this contraction has not been defined. The authors studied these contractions in rat aortic rings. Concentration-response studies indicated that the threshold for contraction was 10{sup {minus}8}M, maximum contraction occurred at 3 {times} 10{sup 7}M and relaxation began at 10{sup {minus}6}M. No contraction occurred in a calcium-free physiological salt solution and the contraction was not inhibited by H-7, a protein kinase C inhibitor. The authors conclude the cobalt in low concentrations causes contraction by activating calcium channels and that in high concentrations it causes relaxation by inactivating these same channels.

  19. In vivo ultrasound assessment of respiratory function of abdominal muscles in normal subjects.

    PubMed

    Misuri, G; Colagrande, S; Gorini, M; Iandelli, I; Mancini, M; Duranti, R; Scano, G

    1997-12-01

    Ultrasonography has recently been proposed for assessing changes in thickness and motion of the diaphragm during contraction in humans. Data on ultrasound assessment of abdominal muscles in humans are scarce. We therefore investigated the changes in thickness and the relevant mechanical effects of abdominal muscles using this technique during respiratory manoeuvres in normal subjects. We evaluated the thickness of the abdominal muscle layers in six normal male subjects (aged 26-36 yrs) using a 7.5 MHz B-mode ultrasound transducer. Gastric (Pg) and mouth pressures, muscle thickness of external oblique (EO), internal oblique (IO), transversus abdominis (TA) and rectus abdominis (RA) were assessed at functional residual capacity (FRC), residual volume (RV), total lung capacity (TLC), during progressive (PEEs) and maximal expiratory efforts (MEEs) against a closed airway and during homolateral (HTR) and contralateral (CTR) trunk rotation. Abdominal muscle thickness was found to be reproducible (coefficient of variation and two-way analysis of variance). Compared to FRC, the thickness of IO, TA and RA significantly increased at RV and during MEEs, whereas EO remained unchanged; at TLC, the thickness of IO and TA significantly decreased. During PEEs, a significant relationship between increase in Pg and TA thickness was observed in all subjects, the thickness of the other abdominal muscles being inconsistently related to Pg. Finally, a significant increase in the thickness of IO and EO was found during HTR and CTR, respectively. We conclude that during maximal expiratory manoeuvres, transversus abdominis, internal oblique and rectus abdominis thickened similarly. Transversus abdominis seems to be the major contributor in generating abdominal expiratory pressure during progressive expiratory efforts. External oblique seems to be preferentially involved during trunk rotation. These results suggest the possible value of studying the abdominal muscles by ultrasonography in

  20. A new paradigm for muscle contraction

    PubMed Central

    Herzog, Walter; Powers, Krysta; Johnston, Kaleena; Duvall, Mike

    2015-01-01

    For the past 60 years, muscle contraction had been thought to be governed exclusively by the contractile filaments, actin, and myosin. This thinking explained most observations for concentric and isometric, but not for eccentric muscle contractions. Just over a decade ago, we discovered that eccentric contractions were associated with a force that could not be assigned to actin and myosin, but was at least in part associated with the filamentous protein titin. Titin was found to bind calcium upon activation, thereby increasing its structural stability, and thus its stiffness and force. Furthermore, there is increasing evidence that the proximal part of titin binds to actin in an activation- and force-dependent manner, thereby shortening its free length, thus increasing its stiffness and force. Therefore, we propose that muscle contraction involves three filaments, actin, myosin and titin, and that titin regulates force by binding calcium and by shortening its spring length by binding to actin. PMID:26113821

  1. The effect of resistance exercise direction for hip joint stabilization on lateral abdominal muscle thickness

    PubMed Central

    Jung, Ju-Hyeon; Lee, Sang-Yeol

    2016-01-01

    The aim of this study was to determine the effects of resistance direction in hip joint stabilization exercise on change in lateral abdominal muscle thickness in healthy adults. Twenty-six healthy adults were randomly allocated to either a hip stabilization exercise by hip straight resistance group (n=12) or a hip diagonal resistance group (n=14). The outcome measures included contraction thickness ratio in transversus abdominis (TrA), internal oblique (IO) and external oblique, and TrA lateral slide were assessed during the abdominal drawing-in maneuver by b-mode ultrasound. The researcher measured the abdominal muscle thickness of each participant before the therapist began the intervention and at the moment intervention was applied. There was a significant difference in lateral abdominal muscle thickness between the straight resistance exercise of hip joint group and the diagonal resistance exercise of hip joint group. Significant differences were found between the two groups in the percentage of change of muscle thickness of the TrA (P=0.018) and in the thickness ratio of the TrA (P=0.018). Stability exercise accompanied by diagonal resistance on the hip joint that was applied in this study can induce automatic contraction of the IO and TrA, which provides stability to the lumbar spine. PMID:27807520

  2. Abdominal muscle and quadriceps strength in chronic obstructive pulmonary disease

    PubMed Central

    Man, W; Hopkinson, N; Harraf, F; Nikoletou, D; Polkey, M; Moxham, J

    2005-01-01

    Background: Quadriceps muscle weakness is common in chronic obstructive pulmonary disease (COPD) but is not observed in a small hand muscle (adductor pollicis). Although this could be explained by reduced activity in the quadriceps, the observation could also be explained by anatomical location of the muscle or fibre type composition. However, the abdominal muscles are of a similar anatomical and fibre type distribution to the quadriceps, although they remain active in COPD. Cough gastric pressure is a recently described technique that assesses abdominal muscle (and hence expiratory muscle) strength more accurately than traditional techniques. A study was undertaken to test the hypothesis that more severe weakness exists in the quadriceps than in the abdominal muscles of patients with COPD compared with healthy elderly controls. Methods: Maximum cough gastric pressure and quadriceps isometric strength were measured in 43 patients with stable COPD and 25 healthy elderly volunteers matched for anthropometric variables. Results: Despite a significant reduction in mean quadriceps strength (29.9 kg v 41.2 kg; 95% CI –17.9 to –4.6; p = 0.001), cough gastric pressure was preserved in patients with COPD (227.3 cm H2O v 204.8 cm H2O; 95% CI –5.4 to 50.6; p = 0.11). Conclusions: Abdominal muscle strength is preserved in stable COPD outpatients in the presence of quadriceps weakness. This suggests that anatomical location and fibre type cannot explain quadriceps weakness in COPD. By inference, we conclude that disuse and consequent deconditioning are important factors in the development of quadriceps muscle weakness in COPD patients, or that activity protects the abdominal muscles from possible systemic myopathic processes. PMID:15923239

  3. Lumbo-pelvic stability and electromyography of abdominal muscles in ballet dancers.

    PubMed

    Negrão Filho, R de Faria; Silva, L Alves; Monteiro, T Lombardi; Alves, N; de Carvalho, A Cesinando; de Azevedo, F Mícolis

    2009-01-01

    Evaluating the ability to rectify and maintain lumbar adjustment can contribute toward the understanding of the behavior of abdominal muscles and their participation in the stability of pelvic muscles in dancers during the posterior pelvic tilt and double straight leg lowering tests. Nine healthy volunteers (male and female ballet dancers; age mean: 25.9 +/- 7.37 years) underwent maximal isometric voluntary contraction (MIVC), isometric voluntary contraction at 50% of MIVC, posterior pelvic tilt (PPT) and double straight leg lowering (DSLL) tests. The tests were carried out in a single day, with 3 repetitions each. During the tests, electromygraphic signals of the rectus abdominis, obliquus internus and obliquus externus were recorded. The signal acquisition system was made up of bipolar surface electrodes, electrogoniometer and an electromechanic device (pressure sensor), which were connected to a signal conditioner module. Root mean square values of each muscle during the DSLL and PPT were converted into percentage of activation of 50% MIVC. Lower back pressure was submitted to the same process. ANOVA with repeated measures was performed, with the level of significance set at p < 0.05. The results revealed that all dancers were able to maintain posterior pelvic tilt and there was trend toward greater activation of the bilateral obliquus internus muscle. In an attempt to keep the pelvic region stabilized during DSLL, there was a greater contribution from the obliquus externus muscle in relation to other abdominal muscles.

  4. ABDOMINAL MUSCLE ACTIVATION INCREASES LUMBAR SPINAL STABILITY: ANALYSIS OF CONTRIBUTIONS OF DIFFERENT MUSCLE GROUPS

    PubMed Central

    Stokes, Ian A.F.; Gardner-Morse, Mack G.; Henry, Sharon M.

    2011-01-01

    Background Antagonistic activation of abdominal muscles and raised intra-abdominal pressure are associated with both spinal unloading and spinal stabilization. Rehabilitation regimens have been proposed to improve spinal stability via selective recruitment of certain trunk muscle groups. This biomechanical study used an analytical model to address whether lumbar spinal stability is increased by selective activation of abdominal muscles. Methods The biomechanical model included anatomically realistic three-layers of curved abdominal musculature connected by fascia, rectus abdominis and 77 symmetrical pairs of dorsal muscles. The muscle activations were calculated with the model loaded with either flexion, extension, lateral bending or axial rotation moments up to 60 Nm, along with intra-abdominal pressure up to 5 or 10 kPa (37.5 or 75 mm Hg) and partial bodyweight. After solving for muscle forces, a buckling analysis quantified spinal stability. Subsequently, different patterns of muscle activation were studied by forcing activation of selected abdominal muscles to at least 10% or 20% of maximum. Findings The spinal stability increased by an average factor of 1.8 with doubling of intra-abdominal pressure. Forced activation of obliques or transversus abdominis muscles to at least 10% of maximum increased stability slightly for efforts other than flexion, but forcing at least 20% activation generally did not produce further increase in stability. Forced activation of rectus abdominis did not increase stability. Interpretation Based on predictions from an analytical spinal buckling model, the degree of stability was not substantially influenced by selective forcing of muscle activation. This casts doubt on the supposed mechanism of action of specific abdominal muscle exercise regimens that have been proposed for low back pain rehabilitation. PMID:21571410

  5. Asymmetric deformation of contracting human gastrocnemius muscle.

    PubMed

    Kinugasa, Ryuta; Hodgson, John A; Edgerton, V Reggie; Sinha, Shantanu

    2012-02-01

    Muscle fiber deformation is related to its cellular structure, as well as its architectural arrangement within the musculoskeletal system. While playing an important role in aponeurosis displacement, and efficiency of force transmission to the tendon, such deformation also provides important clues about the underlying mechanical structure of the muscle. We hypothesized that muscle fiber cross section would deform asymmetrically to satisfy the observed constant volume of muscle during a contraction. Velocity-encoded, phase-contrast, and morphological magnetic resonance imaging techniques were used to measure changes in fascicle length, pinnation angle, and aponeurosis separation of the human gastrocnemius muscle during passive and active eccentric ankle joint movements. These parameters were then used to subsequently calculate the in-plane muscle area subtended by the two aponeuroses and fascicles and to calculate the in-plane (dividing area by fascicle length), and through-plane (dividing muscle volume by area) thicknesses. Constant-volume considerations of the whole-muscle geometry require that, as fascicle length increases, the muscle fiber cross-sectional area must decrease in proportion to the length change. Our empirical findings confirm the definition of a constant-volume rule that dictates that changes in the dimension perpendicular to the plane, i.e., through-plane thickness, (-6.0% for passive, -3.3% for eccentric) equate to the reciprocal of the changes in area (6.8% for passive, 3.7% for eccentric) for both exercise paradigms. The asymmetry in fascicle cross-section deformation for both passive and active muscle fibers is established in this study with a ∼22% in-plane and ∼6% through-plane fascicle thickness change. These fiber deformations have functional relevance, not only because they affect the force production of the muscle itself, but also because they affect the characteristics of adjacent muscles by deflecting their line of pull.

  6. Effect of craniocervical posture on abdominal muscle activities

    PubMed Central

    Su, Jung Gil; Won, Shin Ji; Gak, Hwangbo

    2016-01-01

    [Purpose] The aim of this study was to investigate the influence of the craniocervical posture on abdominal muscle activities in hook-lying position. [Subjects] This study recruited 12 healthy young adults. [Methods] Each subject was asked to adopt a supine position with the hip and knee flexed at 60°. Surface electromyographic signals of transversus abdominis/internal oblique, rectus abdominis, and external oblique in different craniocervical postures (extension, neutral, and flexion) were compared. [Results] The transversus abdominis and rectus abdominis showed increased muscle activities in craniocervical flexion compared to craniocervical extension and neutral position. Greater muscle activities of the external oblique were seen in craniocervical flexion than in craniocervical extension. [Conclusion] Craniocervical flexion was found to be effective to increase the abdominal muscle activities. Consideration of craniocervical posture is recommended when performing trunk stabilization exercises. PMID:27065558

  7. 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.

  8. The effect of tonic contraction of the finger muscle on the motor cortical representation of the contracting adjacent muscle.

    PubMed

    Jono, Yasutomo; Chujo, Yuta; Nomura, Yoshifumi; Tani, Keisuke; Nikaido, Yasutaka; Hatanaka, Ryota; Hiraoka, Koichi

    2015-01-01

    This study examined the effect of tonic contraction of the finger muscle on the motor cortical representation of the contracting adjacent muscle. A representation map of the motor evoked potential (MEP) in the first dorsal interosseous (FDI) and abductor digiti minimi (ADM) muscles was obtained with the subject at rest or during tonic contraction of the ADM muscle while the FDI muscle was tonically contracted. The center of gravity (COG) of the MEP map in the FDI muscle shifted medially during contraction of the ADM muscle. Motor cortical excitability in the motor cortical representation of the FDI muscle that did not overlap with the motor cortical representation of the ADM muscle was suppressed, but motor cortical excitability in the motor cortical representation of the FDI muscle overlapping with the motor cortical representation of the ADM muscle was not suppressed during contraction of the ADM muscle. The motor cortical representation of the FDI muscle not overlapping with the motor cortical representation of the ADM muscle was located lateral to that of the FDI muscle that did overlap with the motor cortical representation of the ADM muscle. Medial shift of the COG of the motor cortical representation of the contracting finger muscle induced by tonic contraction of the adjacent finger muscle must be due to suppression of motor cortical excitability in the lateral part of the representation, which is not shared by the adjacent representation.

  9. Skeletal muscle transverse strain during isometric contraction at different lengths.

    PubMed

    van Donkelaar, C C; Willems, P J; Muijtjens, A M; Drost, M R

    1999-08-01

    An important assumption in 2D numerical models of skeletal muscle contraction involves deformation in the third dimension of the included muscle section. The present paper studies the often used plane strain description. Therefore, 3D muscle surface deformation is measured from marker displacements during isometric contractions at various muscle lengths. Longitudinal strains at superficial muscle fibers ( - 14 +/- 2.6% at L0, n = 57) and aponeurosis (0.8 +/- 0.9% at L0) decrease with increasing muscle length. The same holds for transverse muscle surface strains in superficial muscle fibers and aponeurosis, which are comparable at intermediate muscle length, but differ at long and short muscle length. Because transverse strains during isometric contraction change with initial muscle length, it is concluded that the effect of muscle length on muscle deformation cannot be studied in plane strain models. These results do not counteract the use of these models to study deformation in contractions with approximately - 9 % longitudinal muscle fiber strain, as transverse strain in superficial muscle fibers and in aponeurosis tissue is minimal in that case. Aponeurosis surface area change decreases with increasing initial muscle length, but muscle fiber surface area change is - 11%, independent of muscle length. Assuming incompressible muscle material, this means that strain perpendicular to the muscle surface equals 11%. Taking the relationship between transverse and longitudinal muscle fiber strain into account, it is hypothesized that superficial muscle fibers flatten during isometric contractions.

  10. Progressive Muscle Relaxation and Pain Perception in Abdominal Surgery Patients

    DTIC Science & Technology

    1989-05-01

    subjects (36%) had cholecystectomies, one subject (9%) had an appendectomy, one subject (9%) had a hysterectomy, four subjects (36%) had tubal ligations ...hysterectomies, three subjects (30%) had tubal ligations or fulgarations, five subjects (50%) had diagnostic laparoscopies, and one subject (10%) was classified...muscle relaxation could decrease pain perception, analgesic use, and anxiety in post -operative abdominal surgery patients. Review of demographic data

  11. Localization of motoneurons innervating individual abdominal muscles of the cat

    NASA Technical Reports Server (NTRS)

    Miller, Alan D.

    1987-01-01

    The paper presents the results of a systematic investigation of the innervation of the cat's individual abdominal muscles. The segmental distribution of the different motor pools was determined by using electrical microstimulation of the ventral horn to produce visible localized muscle twitches and by retrograde transport of horseradish peroxidase injected into individual muscles. The segmental distribution of each motor pool was as follows: rectus abdominis, T4-L3; external oblique, T6-L3; transverse abdominis, T9-L3; and internal oblique, T13-L3.

  12. 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

  13. Influence of pelvis position on the activation of abdominal and hip flexor muscles.

    PubMed

    Workman, J Chad; Docherty, David; Parfrey, Kevin C; Behm, David G

    2008-09-01

    A pelvic position has been sought that optimizes abdominal muscle activation while diminishing hip flexor activation. Thus, the objective of the study was to investigate the effect of pelvic position and the Janda sit-up on trunk muscle activation. Sixteen male volunteers underwent electromyographic (EMG) testing of their abdominal and hip flexor muscles during a supine isometric double straight leg lift (DSLL) with the feet held approximately 5 cm above a board. The second exercise (Janda sit-up) was a sit-up action where participants simultaneously contracted the hamstrings and the abdominal musculature while holding an approximately 45 degrees angle at the knee. Root mean square surface electromyography was calculated for the Janda sit-up and DSLL under 3 pelvic positions: anterior, neutral, and posterior pelvic tilt. The selected muscles were the upper and lower rectus abdominis (URA, LRA), external obliques, lower abdominal stabilizers (LAS), rectus femoris, and biceps femoris. The Janda sit-up position demonstrated the highest URA and LRA activation and the lowest rectus femoris activation. The Janda sit-up and the posterior tilt were significantly greater (p < 0.01 and p < 0.05, respectively) than the anterior tilt for the URA and LRA muscles. Activation levels of the URA and LRA in neutral pelvis were significantly (p < 0.01 and p < 0.05, respectively) less than the Janda sit-up position, but not significantly different from the posterior tilt. No significant differences in EMG activity were found for the external obliques or LAS. No rectus femoris differences were found in the 3 pelvis positions. The results of this study indicate that pelvic position had a significant effect on the activation of selected trunk and hip muscles during isometric exercise, and the activation of the biceps femoris during the Janda sit-up reduced the activation of the rectus femoris while producing high levels of activation of the URA and LRA.

  14. Expiratory abdominal muscle activity during ventilatory chemostimulation in piglets.

    PubMed

    Watchko, J F; O'Day, T L; Brozanski, B S; Guthrie, R D

    1990-04-01

    We examined abdominal muscle minute electromyographic (EMG) activity (peak moving time average EMG x respiratory rate) during eupnea, hyperoxic hypercapnia (8% CO2-40% O2-balance N2), and hypoxia (13% O2) in 12 anesthetized (0.5% halothane) newborn piglets. In addition, we assessed the role of vagal afferent pathways in the abdominal muscles' response to ventilatory chemostimulation by examining abdominal EMG activity (EMGab) before and after bilateral cervical vagotomy in five animals. Phasic expiratory EMGab was observed in 11 of 12 piglets during eupnea. Hypercapnia was associated with a sustained augmentation of minute EMGab (444 +/- 208% control). In contrast, hypoxia consistently augmented (1 min, 193 +/- 33% control) then diminished (5 min, 126 +/- 39% control) minute EMGab. Vagotomy resulted in a decline in peak moving time average EMGab by approximately one-half (48 +/- 18% control); the abdominal muscles' response to ventilatory chemostimulation, however, was qualitatively unchanged. We conclude that 1) expiration during eupnea in anesthetized newborn piglets is associated with phasic EMGab; 2) both hypercapnia and hypoxia augment minute EMGab; however, only hypercapnia is associated with sustained augmentation; and 3) although vagal afferents have a role in modulating the base-line level of EMGab, other extravagal mechanisms appear to determine the pattern of EMGab in response to ventilatory chemostimulation.

  15. Contractile properties of the rat external abdominal oblique and diaphragm muscles during development.

    PubMed

    Watchko, J F; Brozanski, B S; O'Day, T L; Guthrie, R D; Sieck, G C

    1992-04-01

    We studied the in vitro contractile and fatigue properties of the rat external abdominal oblique (EAO) and costal diaphragm (DIA) muscles during postnatal development. Isometric twitch contraction (CT) and half-relaxation (RT1/2) times were longer in both the EAO and DIA muscles during the early postnatal period and decreased with age. In the first postnatal week, the CT and RT1/2 were longer in the EAO than the DIA muscle. At 14 days of age and thereafter, the CT and RT1/2 were shorter in the EAO than in the DIA muscle. Force-frequency relationships of the EAO and DIA muscles changed during postnatal development such that the relative force (percent maximum) generated at lower frequencies (less than 15 pulses/s) decreased with age. Moreover the relative force generated by the EAO muscle at lower frequencies was greater than that of the DIA muscle during the early postnatal period but less than that of the DIA muscle in adults. The specific force of both the EAO and DIA muscles increased progressively with age. There were no differences in specific force between the EAO and DIA muscles at any age. The fatigability of the EAO and DIA muscles was comparable during the early postnatal period and increased in both muscles with postnatal development. In adults the EAO muscle was more fatigable than the DIA muscle. We conclude that the contractile and fatigue properties of the EAO and DIA muscles undergo significantly different postnatal transitions, which may reflect their functional involvement in sustaining ventilation.

  16. Independent Active Contraction of Extraocular Muscle Compartments

    PubMed Central

    Shin, Andrew; Yoo, Lawrence; Demer, Joseph L.

    2015-01-01

    Purpose. Intramuscular innervation of horizontal rectus extraocular muscle (EOMs) is segregated into superior and inferior (transverse) compartments, whereas all EOMs are also divided into global (GL) and orbital (OL) layers with scleral and pulley insertions, respectively. Mechanical independence between both types of compartments has been demonstrated during passive tensile loading. We examined coupling between EOM compartments during active, ex vivo contraction. Methods. Fresh bovine EOMs were removed, and one compartment of each was coated with hydrophobic petrolatum. Contraction of the uncoated compartment was induced by immersion in a solution of 50 mM CaCl2 at 38°C labeled with sodium fluorescein dye, whereas tensions in both compartments were monitored by strain gauges. Control experiments omitted petrolatum so that the entire EOM contracted. After physiological experiments, EOMs were sectioned transversely to demonstrate specificity of CaCl2 permeation by yellow fluorescence dye excited by blue light. Results. In control experiments without petrolatum, both transverse and GL and OL compartments contracted similarly. Selective compartmental omission of petrolatum caused markedly independent compartmental contraction whether measured at the GL or the OL insertions or for transverse compartments at the scleral insertion. Although some CaCl2 spread occurred, mean (±SD) tension in the coated compartments averaged only 10.5 ± 3.3% and 6.0 ± 1.5% in GL/OL and transverse compartments, respectively relative to uncoated compartments. Fluorescein penetration confirmed selective CaCl2 permeation. Conclusions. These data confirm passive tensile findings of mechanical independence of EOM compartments and extend results to active contraction. EOMs behave actively as if composed of mechanically independent parallel fiber bundles having different insertional targets, consistent with the active pulley and transverse compartmental hypotheses. PMID:25503460

  17. Lung-deflating ability of rib cage and abdominal muscles in rabbits.

    PubMed

    D'Angelo, Edgardo; Prandi, Edi; D'Angelo, Emanuela; Pecchiari, Matteo

    2003-04-15

    Anesthetized, apneic, mechanically ventilated rabbits were placed into a tilting plethysmograph that a rubber diaphragm, tightly fitting the animal's body just below the xiphoid process, separated into a rib cage and abdominal chamber. Expired volumes (DeltaV) and abdominal pressure changes (DeltaPab) were assessed in supine and upright posture during maximal rib cage (RCC) and/or abdominal compression (ABC) by pressurizing either or both chambers, and during maximal stimulations of abdominal muscles (ABS). With RCC, DeltaV supine and upright amounted to 16+/-4.9 (mean+/-S.D.) and 20.9+/-7% of the vital capacity in supine posture (VCs) and to 75.8+/-14.5 and 44.8+/-13.9% of the expiratory reserve volume (ERV) in corresponding posture, DeltaPab being negligible. With ABC, DeltaV was 13.7+/-2 and 38.9+/-7.3% VCs and 68.4+/-14.8 and 84.4+/-10.5% ERV, respectively. Both DeltaV and DeltaPab were similar with ABC and ABS, independent of posture. If this applies also to RCC and expiratory rib cage muscle contraction, maximal expiratory effects of the latter (a) are larger in upright than supine posture; (b) contribute to ERV more in supine than upright posture; and (c) are similar to those caused by ABS in supine, but substantially smaller in upright posture.

  18. MALDI imaging mass spectrometry of Pacific White Shrimp L. vannamei and identification of abdominal muscle proteins.

    PubMed

    Schey, Kevin L; Hachey, Amanda J; Rose, Kristie L; Grey, Angus C

    2016-06-01

    MALDI imaging mass spectrometry (IMS) has been applied to whole animal tissue sections of Pacific White Shrimp, Litopenaeus vannamei, in an effort to identify and spatially localize proteins in specific organ systems. Frozen shrimp were sectioned along the ventral-dorsal axis and methods were optimized for matrix application. In addition, tissue microextraction and homogenization was conducted followed by top-down LC-MS/MS analysis of intact proteins and searches of shrimp EST databases to identify imaged proteins. IMS images revealed organ system specific protein signals that highlighted the hepatopancreas, heart, nervous system, musculature, and cuticle. Top-down proteomics identification of abdominal muscle proteins revealed the sequence of the most abundant muscle protein that has no sequence homology to known proteins. Additional identifications of abdominal muscle proteins included titin, troponin-I, ubiquitin, as well as intact and multiple truncated forms of flightin; a protein known to function in high frequency contraction of insect wing muscles. The combined use of imaging mass spectrometry and top-down proteomics allowed for identification of novel proteins from the sparsely populated shrimp protein databases.

  19. Some effects of vagal blockade on abdominal muscle activation and shortening in awake dogs.

    PubMed Central

    Leevers, A M; Road, J D

    1995-01-01

    1. The mechanisms of abdominal muscle activation are thought to be different during expiratory threshold loading (ETL) compared with hypercapnia. Our objectives in the present study were to determine the effects of removing excitatory vagal feedback on abdominal muscle activation, shortening and pattern of recruitment during ETL and hypercapnia. Six tracheotomized dogs were chronically implanted with sonomicrometer transducers and fine wire EMG electrodes in each of the four abdominal muscles. Muscle length changes and EMG activity were studied in the awake dog during ETL (6 dogs) and CO2 rebreathing (3 dogs), before and after vagal blockade. 2. Following vagal blockade, the change in volume (increase in functional residual capacity, FRC) during ETL was greater and active phasic shortening of all the abdominal muscles was reduced, when shortening was compared with a similar change in lung volume. Similarly, at comparable minute ventilation, abdominal muscle active shortening was also reduced during hypercapnia. The internal muscle layer was recruited preferentially in both control and vagally blocked dogs during both ETL and hypercapnia. 3. The degree of recruitment of the abdominal muscles during ETL and hypercapnia in awake dogs is influenced by vagal feedback, but less so than in anaesthetized dogs. These results illustrate the importance of the vagi and abdominal muscle activation in load compensation. However, vagal reflexes are apparently not contributing to the preferential recruitment of the internal muscle layer. In awake dogs during vagal blockade abdominal muscle recruitment still occurs by extravagal mechanisms. PMID:8568685

  20. Contraction stimulates muscle glucose uptake independent of atypical PKC.

    PubMed

    Yu, Haiyan; Fujii, Nobuharu L; Toyoda, Taro; An, Ding; Farese, Robert V; Leitges, Michael; Hirshman, Michael F; Mul, Joram D; Goodyear, Laurie J

    2015-11-01

    Exercise increases skeletal muscle glucose uptake, but the underlying mechanisms are only partially understood. The atypical protein kinase C (PKC) isoforms λ and ζ (PKC-λ/ζ) have been shown to be necessary for insulin-, AICAR-, and metformin-stimulated glucose uptake in skeletal muscle, but not for treadmill exercise-stimulated muscle glucose uptake. To investigate if PKC-λ/ζ activity is required for contraction-stimulated muscle glucose uptake, we used mice with tibialis anterior muscle-specific overexpression of an empty vector (WT), wild-type PKC-ζ (PKC-ζ(WT)), or an enzymatically inactive T410A-PKC-ζ mutant (PKC-ζ(T410A)). We also studied skeletal muscle-specific PKC-λ knockout (MλKO) mice. Basal glucose uptake was similar between WT, PKC-ζ(WT), and PKC-ζ(T410A) tibialis anterior muscles. In contrast, in situ contraction-stimulated glucose uptake was increased in PKC-ζ(T410A) tibialis anterior muscles compared to WT or PKC-ζ(WT) tibialis anterior muscles. Furthermore, in vitro contraction-stimulated glucose uptake was greater in soleus muscles of MλKO mice than WT controls. Thus, loss of PKC-λ/ζ activity increases contraction-stimulated muscle glucose uptake. These data clearly demonstrate that PKC-λζ activity is not necessary for contraction-stimulated glucose uptake.

  1. Muscle contraction increases carnitine uptake via translocation of OCTN2.

    PubMed

    Furuichi, Yasuro; Sugiura, Tomoko; Kato, Yukio; Takakura, Hisashi; Hanai, Yoshiteru; Hashimoto, Takeshi; Masuda, Kazumi

    2012-02-24

    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. The tissue uptake clearance (CL(uptake)) of l-[(3)H]carnitine during muscle contraction was examined in vivo using integration plot analysis. The CL(uptake) of [(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(uptake) of l-[(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(uptake) of [(14)C]IAP was much higher than that of l-[(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, possibly via the contraction-induced translocation of its specific transporter OCTN2 to the plasma membrane.

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

    PubMed Central

    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. PMID:27242537

  3. Muscle contraction increases carnitine uptake via translocation of OCTN2

    SciTech Connect

    Furuichi, Yasuro; Sugiura, Tomoko; Kato, Yukio; Takakura, Hisashi; Hanai, Yoshiteru; Hashimoto, Takeshi; Masuda, Kazumi

    2012-02-24

    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. 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, possibly

  4. Glucose uptake and transport in contracting, perfused rat muscle with different pre-contraction glycogen concentrations.

    PubMed Central

    Hespel, P; Richter, E A

    1990-01-01

    1. Glucose uptake and transport, muscle glycogen, free glucose and glucose-6-phosphate concentrations were studied in perfused resting and contracting rat skeletal muscle with different pre-contraction glycogen concentrations. Rats were pre-conditioned by a combination of swimming exercise and diet, resulting in either low (glycogen-depleted rats), normal (control rats) or high (supercompensated rats) muscle glycogen concentrations at the time their hindlimbs were perfused. 2. Compared with control rats, pre-contraction muscle glycogen concentration was approximately 40% lower in glycogen-depleted rats, whereas it was 40% higher in supercompensated rats. Muscle glycogen break-down correlated positively (r = 0.76; P less than 0.001) with pre-contraction muscle glycogen concentration. 3. Glucose uptake during contractions was approximately 50% higher in glycogen-depleted hindquarters than in control hindquarters; in supercompensated hindquarters it was 30% lower. When rats with similar muscle glycogen concentrations were compared, glucose uptake in hindquarters from rats that had exercised on the preceding day was approximately 20% higher than in hindquarters from rats that had not exercised on the preceding day. 4. Muscle membrane glucose transport, as measured by the rate of accumulation of 14C-3-O-methylglucose in the contracting muscles, was 25% lower in supercompensated than in glycogen-depleted muscles at the onset as well as at the end of the 15 min contraction period. 5. Intracellular concentrations of free glucose and glucose-6-phosphate were higher at rest and during the entire 15-min stimulation period in supercompensated muscles than in glycogen-depleted muscles, and glucose uptake during contractions correlated negatively with free glucose (r = -0.52; P less than 0.01) as well as with glucose-6-phosphate (r = -0.49; P less than 0.01) concentrations. 6. It is concluded that: (a) The rate of glucose uptake in contracting skeletal muscle is dependent on the

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

    PubMed Central

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

    2017-01-01

    [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. PMID:28356636

  6. 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.

  7. 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.

  8. Work done by titin protein folding assists muscle contraction

    PubMed Central

    Popa, Ionel; Kosuri, Pallav; Linke, Wolfgang A.; Fernández, Julio M.

    2016-01-01

    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 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 so far unrecognized contributor to the force generated by a contracting muscle. PMID:26854230

  9. The effect of food consumption on the thickness of abdominal muscles, employing ultrasound measurements.

    PubMed

    Kordi, Ramin; Rostami, Mohsen; Noormohammadpour, Pardis; Mansournia, Mohammad Ali

    2011-08-01

    Recently, the roles of transabdominal muscles particularly TrA (transverse abdominis) muscle in spinal stability leading to treatment of low back pain have been suggested. Both in clinical setting and follow up studies, abdominal muscle thickness measurements need to be repeated at a later point in time to demonstrate efficacy of a therapeutic intervention. Different issues have been suggested as source of error in the repeated measurements of abdominal muscle thickness in different days such as patient position and stability of probe location. The level of stomach fullness has not been investigated as a source of error in ultrasonic measurements of transabdominal muscles thickness. This study was performed to evaluate the effect of food consumption on thickness of lateral abdominal muscles. Lateral abdominal muscles thicknesses of 63 healthy volunteer men were measured before and after food consumption. All the measurements were performed in two transducer positions and both sides. Waist circumference and body weight of participants were also measured before and post-food consumption. The thickness measures of all three muscles layers of lateral abdominal muscles (external oblique, internal oblique and transversus abdominis) in both sides and measured positions were significantly reduced after food consumption. We found no correlation between the increase of waist circumference and reduction of muscle layer thicknesses after food consumption. In case of comparison between the values of transabdominal muscle thicknesses over the time, the effect of food consumption on muscle thickness might be assumed as a potential source of error.

  10. 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

  11. Eccentric contractions disrupt FKBP12 content in mouse skeletal muscle.

    PubMed

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

    2014-07-16

    Strength deficits associated with eccentric contraction-induced muscle injury stem, in part, from impaired voltage-gated sarcoplasmic reticulum (SR) Ca(2+) release. FKBP12 is a 12-kD immunophilin known to bind to the SR Ca(2+) 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; R(2) = 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.

  12. Contraction induced muscle injury: towards personalized training and recovery programs.

    PubMed

    Givli, Sefi

    2015-02-01

    Skeletal muscles can be injured by their own contractions. Such contraction-induced injury, often accompanied by delayed onset of muscle soreness, is a leading cause of the loss of mobility in the rapidly increasing population of elderly people. Unlike other types of muscle injuries which hurt almost exclusively those who are subjected to intensive exercise such as professional athletes and soldiers in training, contraction induced injury is a phenomenon which may be experienced by people of all ages while performing a variety of daily-life activities. Subjects that experience contraction induced injury report on soreness that usually increases in intensity in the first 24 h after the activity, peaks from 24 to 72 h, and then subsides and disappears in a few days. Despite their clinical importance and wide influence, there are almost no studies, clinical, experimental or computational, that quantitatively relate between the extent of contraction induced injury and activity factors, such as number of repetitions, their frequency and magnitude. The lack of such quantitative information is even more emphasized by the fact that contraction induced injury can be used, if moderate and controlled, to improve muscle performance in the long term. Thus, if properly understood and carefully implemented, contraction induced injury can be used for the purpose of personalized training and recovery programs. In this paper, we review experimental, clinical, and theoretical works, attempting towards drawing a more quantitative description of contraction induced injury and related phenomena.

  13. 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.

  14. 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

  15. 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.

  16. Ultrafast imaging of in vivo muscle contraction using ultrasound

    NASA Astrophysics Data System (ADS)

    Deffieux, Thomas; Gennisson, Jean-Luc; Tanter, Mickaël; Fink, Mathias; Nordez, Antoine

    2006-10-01

    In this letter, an innovative way of imaging transient and local shear vibrations of an in vivo contracting muscle is proposed. The principle is to use an ultrafast ultrasound scanner (up to 5000framess-1) able to follow with a submillimeter resolution the motion of the muscle tissue in a two dimensional plane. This ultrafast echographic imaging technique leads to both local and transient in vivo studies of the contraction of a muscle as reported by these first experiments done on the biceps brachii.

  17. The architecture and contraction time of intrinsic foot muscles.

    PubMed

    Tosovic, Danijel; Ghebremedhin, Estifanos; Glen, Christopher; Gorelick, Mark; Mark Brown, J

    2012-12-01

    Although critical for effective human locomotion and posture, little data exists regarding the segmentation, architecture and contraction time of the human intrinsic foot muscles. To address this issue, the Abductor Hallucis (AH), Abductor Digiti Minimi (ADM), Flexor Digitorum Brevis (FDB) and Extensor Digitorum Brevis (EDB) were investigated utilizing a cadaveric dissection and a non-invasive whole muscle mechanomyographic (wMMG) technique. The segmental structure and architecture of formaldehyde-fixed foot specimens were determined in nine cadavers aged 60-80 years. The wMMG technique was used to determine the contraction time (Tc) of individual muscle segments, within each intrinsic foot muscle, in 12 volunteers of both genders aged between 19 and 24 years. While the pattern of segmentation and segmental -architecture (e.g. fibre length) and -Tc of individual muscle segments within the same muscle were similar, they varied between muscles. Also, the average whole muscle Tc of FDB was significantly (p < 0.05) shorter (faster) (Tc = 58 ms) than in all other foot muscles investigated (ADM Tc = 72 ms, EDB Tc = 72 ms and ABH Tc = 69 ms). The results suggest that the architecture and contraction time of the FDB reflect its unique direct contribution, through toe flexion, to postural stability and the rapid development of ground reaction forces during forceful activities such as running and jumping.

  18. Castration alters protein balance after high-frequency muscle contraction.

    PubMed

    Steiner, Jennifer L; Fukuda, David H; Rossetti, Michael L; Hoffman, Jay R; Gordon, Bradley S

    2017-02-01

    Resistance exercise increases muscle mass by shifting protein balance in favor of protein accretion. Androgens independently alter protein balance, but it is unknown whether androgens alter this measure after resistance exercise. To answer this, male mice were subjected to sham or castration surgery 7-8 wk before undergoing a bout of unilateral, high-frequency, electrically induced muscle contractions in the fasted or refed state. Puromycin was injected 30 min before euthanasia to measure protein synthesis. The tibialis anterior was analyzed 4 h postcontraction. In fasted mice, neither basal nor stimulated rates of protein synthesis were affected by castration despite lower phosphorylation of mechanistic target of rapamycin in complex 1 (mTORC1) substrates [p70S6K1 (Thr389) and 4E-BP1 (Ser65)]. Markers of autophagy (LC3 II/I ratio and p62 protein content) were elevated by castration, and these measures remained elevated above sham values after contractions. Furthermore, in fasted mice, the protein content of Regulated in Development and DNA Damage 1 (REDD1) was correlated with LC3 II/I in noncontracted muscle, whereas phosphorylation of uncoordinated like kinase 1 (ULK1) (Ser757) was correlated with LC3 II/I in the contracted muscle. When mice were refed before contractions, protein synthesis and mTORC1 signaling were not affected by castration in either the noncontracted or contracted muscle. Conversely, markers of autophagy remained elevated in the muscles of refed, castrated mice even after contractions. These data suggest the castration-mediated elevation in baseline autophagy reduces the absolute positive shift in protein balance after muscle contractions in the refed or fasted states.

  19. 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.

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

    PubMed Central

    Kou, Wenjun; Pandolfino, John E.; Kahrilas, Peter J.

    2015-01-01

    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. PMID:26113296

  1. Peak power of muscles injured by lengthening contractions.

    PubMed

    Widrick, Jeffrey J; Barker, Tyler

    2006-10-01

    Excessive or extreme lengthening contractions have a well-characterized depressive effect on skeletal muscle isometric force. In addition to producing force, active muscles must often shorten in order to meet the power requirements of locomotion and other physical activities. However, the impact of lengthening contractions on muscle power is poorly understood. We evaluated the effect of 20 isometric contractions or 20 lengthening contractions (20% strain at 1.5 fiber lengths/s) on the force-velocity-power relationships of mouse soleus muscles in vitro at 35 degrees C. Pre- and posttreatment data were obtained as the muscles shortened through their optimal length (Lo). The isometric treatment did not alter Lo, the curvature of the force-velocity relationship (a/Po), or soleus maximal shortening velocity (Vmax), whereas peak force (Po) displayed a slow, time-dependent decline of 10% across the experiments. Following the lengthening treatment, Lo increased by 6%, a/Po increased by 22%, and Vmax and Po fell by 24% and 26%, respectively. Under optimal conditions for producing power, muscles damaged by lengthening contractions attained 22% less force and shortened 20% more slowly than before damage. Consequently, soleus peak power fell 37% after lengthening, a 2.5-fold greater decline than noted for the isometric treatment. Under the conditions studied here, the excessive power loss following lengthening contractions was due to force and velocity deficits of approximately equal relative magnitude. Because power represents the ability of the muscle to perform work, reductions in both force and shortening velocity should be considered when evaluating and treating lengthening-induced skeletal muscle injuries.

  2. Characteristics of tetanic muscle contraction in Parkinson patients.

    PubMed

    Pedersen, S W; Bäckman, E; Oberg, B

    1991-09-01

    The aim of this study was to examine contraction characteristics in striated muscles from Parkinson patients and to measure any changes in characteristics based on changes in medication. Fifteen patients, 9 men and 6 women, mean age 61.6 (range 43-70) with mild to moderate parkinsonism, (Hoehn and Yahr I-III) were investigated, and the results were compared with a group of 8 normal controls (mean age 59.6, range 50-70). Twelve of the patients (7 men and 5 women) were also tested after a 24-h period without medication. Using supramaximal electrical stimulation of the ulnary nerve at the wrist contraction, characteristics in the m. adductor pollicis muscle can be recorded. Stimulation results were printed on a fast paper writer. The following characteristics were recorded: 1) electromechanical delay of contraction EMDc; 2) contraction time to half tetanus CTT1/2; 3) electromechanical delay of relaxation EMDr; 4) relaxation rate RR for 10 ms RR-10; 5) the force produced in the tetanic contraction at stimulus frequencies 5, 10, 20, 50 Hz. The results showed that the in initiation of contraction (EMDc) was normal compared with controls. CTT1/2 was shorter (p less than 0.001) in the group of Parkinson patients compared with normals. EMDr was not changed when compared with normals, but RR-10 was increased, p less than 0.05. Force levels at the different stimulation rates were not significantly changed. After withdrawal of medication all parameters were unchanged. Muscle contraction characteristics in tetanic contraction were found to be abnormal indicating either a possible preactivation in the muscle contraction or a secondary change in the muscles of patients with Parkinson's disease.

  3. 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.

  4. Therapeutic effects of massage and electrotherapy on muscle tone, stiffness and muscle contraction following gastrocnemius muscle fatigue

    PubMed Central

    Wang, Joong-San

    2017-01-01

    [Purpose] This study aimed to examine the effects of a combined intervention consisting of massage therapy and transcutaneous electrical nerve stimulation on gastrocnemius muscle fatigue, assessing whether the intervention improved muscle tone, stiffness, and muscle contraction. [Subjects and Methods] The subjects were 20 healthy males in their 20s who were equally divided into a transcutaneous electrical nerve stimulation group and a combined therapy group that received a combination of massage therapy and transcutaneous electrical nerve stimulation. Muscle fatigue was triggered on the gastrocnemius muscle, and the effects of intervention method on muscle tone, stiffness, and muscle contraction were examined over time. [Results] Lateral and medial gastrocnemius muscle tone and stiffness significantly increased and gastrocnemius muscle contraction significantly decreased in each group immediately after fatigue was triggered on the gastrocnemius muscle. There was no difference in the effects of the two intervention methods over time. [Conclusion] This study verified that a combined therapy of massage therapy and transcutaneous electrical nerve stimulation was able to be used effectively in improving muscle tone, stiffness, muscle contraction, thereby reducing gastrocnemius muscle fatigue. PMID:28210061

  5. Unilateral muscle contractions enhance creative thinking.

    PubMed

    Goldstein, Abraham; Revivo, Ketty; Kreitler, Michal; Metuki, Nili

    2010-12-01

    Following the notion of relative importance of the right hemisphere (RH) in creative thinking, we explored the possibility of enhancing creative problem solving by artificially activating the RH ahead of time using unilateral hand contractions. Participants attempted to complete the Remote Associates Test after squeezing a ball with either their left or right hand. As predicted, participants who contracted their left hand (thus activating the RH) achieved higher scores than those who used their right hand and those who did not contract either hand. Our findings indicate that tilting the hemispheric balance toward the processing mode of one hemisphere by motor activation can greatly influence the outcome of thought processes. Regardless of the specific mechanism involved, this technique has the potential for acting as a therapeutic or remedial manipulation and could have wide applications in aiding individuals with language impairments or other disorders that are believed to be related to hemispheric imbalances.

  6. 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

  7. Redox state changes in human skeletal muscle after isometric contraction.

    PubMed Central

    Henriksson, J; Katz, A; Sahlin, K

    1986-01-01

    Subjects maintained an isometric contraction of the quadriceps femoris muscle at two-thirds maximal voluntary contraction (m.v.c.) force for 5 s (5.0 +/- 0.3 s; mean +/- S.E. of mean; n = 6) or until fatigue (52 +/- 4 s; n = 13). Muscle biopsies were obtained at rest, immediately after the contractions and also at 1 and 4 min of recovery after contraction to fatigue. In all subjects 5 s isometric contraction resulted in an increase of muscle NADH (0.084 +/- 0.012 at rest to 0.203 +/- 0.041 mmol/kg dry wt.) and a decrease of phosphocreatine (PC; change in concentration = -17.3 +/- 3.8 mmol/kg dry wt.). Glucose-6-phosphate concentration was more than doubled whereas lactate increased in only four of the six subjects. The two subjects who did not show any increase in lactate also had the lowest increase in NADH. At fatigue NADH increased to 0.226 +/- 0.032 mmol/kg dry wt. which was not significantly different from the value after 5 s contraction. Muscle PC was nearly depleted and lactate increased 12-fold above resting levels. The major part (65%) of the NADH increase at fatigue had reverted after 1 min recovery but only a slight further decrease occurred between 1 and 4 min of recovery. In relative terms the time course of the changes in muscle NADH during the first minute of recovery was similar to that of PC resynthesis, suggesting a common regulator such as O2 availability. In contrast to the delayed return of NADH concentration, PC resynthesis continued during the later part of the recovery period and PC concentration was almost fully restored after 4 min of recovery. It is concluded that muscle NADH is already maximally increased in the first seconds of muscle contraction at two-thirds m.v.c. Indirect evidence indicates that this increase reflects a reduction of the mitochondrial NAD-NADH redox couple. The rapid establishment of a reduced mitochondrial redox state at the start of muscle contraction will probably lead to a reduction of the redox state in the

  8. High-speed cinematography of muscle contraction.

    PubMed

    HAUPT, R E; WALL, D M

    1962-07-13

    Motion pictures of the "twitch" of an excised frog gastrocnemius muscle taken at rates of 6000 frames per second provide a means of very accurately timing the phases. The extreme "slow motion" reveals surface phenomena not observable by other techniques. Evidence of "active relaxation" is suggested by results of frame-by-frame analysis.

  9. 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.

  10. Tomographic elastography of contracting skeletal muscles from their natural vibrations

    NASA Astrophysics Data System (ADS)

    Sabra, Karim G.; Archer, Akibi

    2009-11-01

    Conventional elastography techniques require an external mechanical or radiation excitation to measure noninvasively the viscoelastic properties of skeletal muscles and thus monitor human motor functions. We developed instead a passive elastography technique using only an array of skin-mounted accelerometers to record the low-frequency vibrations of the biceps brachii muscle naturally generated during voluntary contractions and to determine their two-dimensional directionality. Cross-correlating these recordings provided travel-times measurements of these muscle vibrations between multiple sensor pairs. Travel-time tomographic inversions yielded spatial variations of their propagation velocity during isometric elbow flexions which indicated a nonuniform longitudinal stiffening of the biceps.

  11. Modeling the contraction of the pelvic floor muscles.

    PubMed

    Brandão, Fernanda Sofia Quintela da Silva; Parente, Marco Paulo Lages; Rocha, Paulo Alexandre Gomes Gonçalves; Saraiva, Maria Teresa da Quinta E Costa de Mascarenhas; Ramos, Isabel Maria Amorim Pereira; Natal Jorge, Renato Manuel

    2016-01-01

    We performed numerical simulation of voluntary contraction of the pelvic floor muscles to evaluate the resulting displacements of the organs and muscles. Structures were segmented in Magnetic Resonance (MR) images. Different material properties and constitutive models were attributed. The Finite Element Method was applied, and displacements were compared with dynamic MRI findings. Numerical simulation showed muscle magnitude displacement ranging from 0 to 7.9 mm, more evident in the posterior area. Accordingly, the anorectum moved more than the uterus and bladder. Dynamic MRI showed less 0.2 mm and 4.1 mm muscle dislocation in the anterior and cranial directions, respectively. Applications of this model include evaluating muscle impairment, subject-specific mesh implant planning, or effectiveness of rehabilitation.

  12. Direct observations of muscle arterioles and venules following contraction of skeletal muscle fibres in the rat.

    PubMed Central

    Marshall, J M; Tandon, H C

    1984-01-01

    Direct observations have been made of responses of individual arterioles and venules of rat spinotrapezius muscle to contraction of the skeletal muscle fibres. Stimuli of 4-6 V intensity, 0.1 ms duration, delivered via a micro-electrode inserted into the spinotrapezius, evoked contraction of a small bundle of skeletal muscle fibres, followed by vasodilatation which was limited to all those arterioles and venules which crossed or ran alongside activated muscle fibres. Since venules outside the region of contraction, but supplied by dilating arterioles, were not passively distended by the attendant rise in intravascular pressure, it is concluded that both the arterioles and venules dilated actively in response to muscle contraction. All arterioles responded to a single twitch contraction, the terminal arterioles (7-13 micron i.d.) showing the largest increase in diameter. Collecting venules (9-18 micron i.d.) responded to just two twitches in 1 s and larger venules to five twitches in 1 s. When twitch contractions were continuously evoked for 10 s, the responses in individual arterioles and venules were graded with twitch frequency, the fastest and largest response occurring at 6-8 Hz. Tetanic contraction, at 40 Hz for 1 s, produced faster responses in all vessels, a maximum 55% increase from resting internal diameter being attained in only 8 s in some terminal arterioles. In all vessels the responses to tetanic contraction were equal to the maximal dilatation induced by papaverine. These results, in contrast with conclusions drawn from indirect estimates of venous responses, show that venules, like arterioles, dilate actively in response to muscle contraction. Venule dilatation may reduce the rise in capillary hydrostatic pressure, thereby limiting the outward filtration of fluid. PMID:6747856

  13. 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.

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

    PubMed

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

    2015-10-13

    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.

  15. Excitation-contraction coupling in voltage clamped uterine smooth muscle

    PubMed Central

    Mironneau, Jean

    1973-01-01

    1. The relationship between ionic currents and contraction has been investigated in uterine strips of pregnant rat by means of a double sucrose gap apparatus combined with an optical method which permits the measurement of the contraction of the small muscular bundle where potential and current are recorded. 2. Effects of duration, size and frequency of imposed potentials upon contraction have been studied. The uterine muscle shows summation and tetanus phenomena. Tension elicited by depolarizing pulses of different durations and amplitudes can be considered as made of two components. 3. The first component of the contraction evoked by short depolarizing steps (about 50 ms) depends on the slow inward current. This contraction is abolished by manganese and lanthanum ions and by compound D 600. The amplitude of the tension can be related to the external calcium concentration and consequently to the calcium influx. The slow inward current is supposed to release a part of the bound calcium without excluding, however, a direct activation of myofibrils. 4. The second component of the contraction is observed in manganese containing solution with depolarizations longer than 200 ms and without inward current. Such a component of tension suggests the possibility of release of calcium from intracellular stores which could be located in the sarcoplasmic membrane of the uterine smooth muscle. PMID:4796671

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

    SciTech Connect

    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 related 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.

  17. 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.

  18. 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.

  19. Muscle force estimation with surface EMG during dynamic muscle contractions: a wavelet and ANN based approach.

    PubMed

    Bai, Fengjun; Chew, Chee-Meng

    2013-01-01

    Human muscle force estimation is important in biomechanics studies, sports and assistive devices fields. Therefore, it is essential to develop an efficient algorithm to estimate force exerted by muscles. The purpose of this study is to predict force/torque exerted by muscles under dynamic muscle contractions based on continuous wavelet transform (CWT) and artificial neural networks (ANN) approaches. Mean frequency (MF) of the surface electromyography (EMG) signals power spectrum was calculated from CWT. ANN models were trained to derive the MF-force relationships from the subset of EMG signals and the measured forces. Then we use the networks to predict the individual muscle forces for different muscle groups. Fourteen healthy subjects (10 males and 4 females) were voluntarily recruited in this study. EMG signals were collected from the biceps brachii, triceps, hamstring and quadriceps femoris muscles to evaluate the proposed method. Root mean square errors (RMSE) and correlation coefficients between the predicted forces and measured actual forces were calculated.

  20. 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.

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

    PubMed Central

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

    2006-01-01

    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. PMID:16849250

  2. Modulation effects of cordycepin on the skeletal muscle contraction of toad gastrocnemius muscle.

    PubMed

    Yao, Li-Hua; Meng, Wei; Song, Rong-Feng; Xiong, Qiu-Ping; Sun, Wei; Luo, Zhi-Qiang; Yan, Wen-Wen; Li, Yu-Ping; Li, Xin-Ping; Li, Hai-Hang; Xiao, Peng

    2014-03-05

    Isolated toad gastrocnemius muscle is a typical skeletal muscle tissue that is frequently used to study the motor system because it is an important component of the motor system. This study investigates the effects of cordycepin on the skeletal muscle contractile function of isolated toad gastrocnemius muscles by electrical field stimulation. Results showed that cordycepin (20 mg/l to 100 mg/l) significantly decreased the contractile responses in a concentration-dependent manner. Cordycepin (50 mg/l) also produced a rightward shift of the contractile amplitude-stimulation intensity relationship, as indicated by the increases in the threshold stimulation intensity and the saturation stimulation intensity. However, the most notable result was that the maximum amplitude of the muscle contractile force was significantly increased under cordycepin application (122±3.4% of control). This result suggests that the skeletal muscle contractile function and muscle physical fitness to the external stimulation were improved by the decreased response sensitivity in the presence of cordycepin. Moreover, cordycepin also prevented the repetitive stimulation-induced decrease in muscle contractile force and increased the recovery amplitude and recovery ratio of muscle contraction. However, these anti-fatigue effects of cordycepin on muscle contraction during long-lasting muscle activity were absent in Ca2+-free medium or in the presence of all Ca2+ channels blocker (0.4 mM CdCl2). These results suggest that cordycepin can positively affect muscle performance and provide ergogenic and prophylactic benefits in decreasing skeletal muscle fatigue. The mechanisms involving excitation-coupled Ca2+ influxes are strongly recommended.

  3. Abdominal Closure after TRAM Flap Breast Reconstruction with Transversus Abdominis Muscle Release and Mesh

    PubMed Central

    Avendano-Peza, Héctor; Novitsky, Yuri W.

    2016-01-01

    Summary: Breast reconstruction with a pedicled transverse rectus abdominis muscle (TRAM) flap can result in significant abdominal wall donor-site morbidity. Although the pedicled TRAM flap donor area reinforced with mesh results in decreased rates of postoperative abdominal bulging and hernias, the best technique to accomplish that is yet to be elucidated. We present our novel technique of posterior components separation with transversus abdominis muscle release and retromuscular mesh reinforcement for donor-area closure during pedicled TRAM flap breast reconstruction. PMID:27757337

  4. Quantitative model for predicting lymph formation and muscle compressibility in skeletal muscle during contraction and stretch

    PubMed Central

    Causey, Laura; Cowin, Stephen C.; Weinbaum, Sheldon

    2012-01-01

    Skeletal muscle is widely perceived as nearly incompressible despite the fact that blood and lymphatic vessels within the endomysial and perimysial spaces undergo significant changes in diameter and length during stretch and contraction. These fluid shifts between fascicle and interstitial compartments have proved extremely difficult to measure. In this paper, we propose a theoretical framework based on a space-filling hexagonal fascicle array to provide predictions of the displacement of blood and lymph into and out of the muscle’s endomysium and perimysium during stretch and contraction. We also use this model to quantify the distribution of blood and initial lymphatic (IL) vessels within a fascicle and its perimysial space using data for the rat spinotrapezius muscle. On average, there are 11 muscle fibers, 0.4 arteriole/venule pairs, and 0.2 IL vessels per fascicle. The model predicts that the blood volume in the endomysial space increases 24% and decreases 22% for a 20% contraction and stretch, respectively. However, these significant changes in blood volume in the endomysium produce a change of only ∼2% in fascicle cross-sectional area. In contrast, the entire muscle deviates from isovolumetry by 7% and 6% for a 20% contraction and stretch, respectively, largely attributable to the significantly larger blood volume changes that occur in the perimysial space. This suggests that arcade blood vessels in the perimysial space provide the primary pumping action required for the filling and emptying of ILs during muscular contraction and stretch. PMID:22615376

  5. From depolarization-dependent contractions in gastrointestinal smooth muscle to aortic pulse-synchronized contractions.

    PubMed

    Marion, Sarah B; Mangel, Allen W

    2014-01-01

    For decades, it was believed that the diameter of gastrointestinal smooth muscle cells is sufficiently narrow, and that the diffusion of calcium across the plasma membrane is sufficient, to support contractile activity. Thus, depolarization-triggered release of intracellular calcium was not believed to be operative in gastrointestinal smooth muscle. However, after the incubation of muscle segments in solutions devoid of calcium and containing the calcium chelator ethylene glycol tetraacetic acid, an alternative electrical event occurred that was distinct from normal slow waves and spikes. Subsequently, it was demonstrated in gastrointestinal smooth muscle segments that membrane depolarization associated with this alternative electrical event triggered rhythmic contractions by release of intracellular calcium. Although this concept of depolarization-triggered calcium release was iconoclastic, it has now been demonstrated in multiple gastrointestinal smooth muscle preparations. On the basis of these observations, we investigated whether a rhythmic electrical and mechanical event would occur in aortic smooth muscle under the same calcium-free conditions. The incubation of aortic segments in a solution with no added calcium plus ethylene glycol tetraacetic acid induced a fast electrical event without corresponding tension changes. On the basis of the frequency of these fast electrical events, we pursued, contrary to what has been established dogma for more than three centuries, the question of whether the smooth muscle wall of the aorta undergoes rhythmic activation during the cardiac cycle. As with depolarization-triggered contractile activity in gastrointestinal smooth muscle, it was "well known" that rhythmic activation of the aorta does not occur in synchrony with the heartbeat. In a series of experiments, however, it was demonstrated that rhythmic contractions occur in the aortic wall in synchrony with the heartbeat and share a common pacemaker with the heart. We

  6. Fluctuations in tension during contraction of single muscle fibers.

    PubMed Central

    Borejdo, J; Morales, M F

    1977-01-01

    We have searched for fluctuations in the steady-state tension developed by stimulated single muscle fibers. Such tension "noise" is expected to be present as a result of the statistical fluctuations in the number and/or state of myosin cross-bridges interacting with thin filament sites at any time. A sensitive electro-optical tension transducer capable of resolving the expected fluctuations in magnitude and frequency was constructed to search for the fluctuations. The noise was analyzed by computing the power spectra and amplitude of stochastic fluctuations in the photomultiplier counting rate, which was made proportional to muscle force. The optical system and electronic instrumentation together with the minicomputer software are described. Tensions were measured in single skinned glycerinated rabbit psoas muscle fibers in rigor and during contraction and relaxation. The results indicate the presence of fluctuations in contracting muscles and a complete absence of tension noise in eith rigor or relaxation. Also, a numerical method was developed to simulate the power spectra and amplitude of fluctuations, given the rate constants for association and dissociation of the cross-bridges and actin. The simulated power spectra and the frequency distributions observed experimentally are similar. PMID:922123

  7. [Effect of thyroidectomy on energetics of isometric muscle contraction in white rats].

    PubMed

    Soboliev, V I; Moskalets', T V

    2007-01-01

    The effect of thyroidactomia on parameters of energetics of isometric contractions of front shin--bone muscle of white rats is studied in in situ experiments. It is shown that experimental atiriosis lengthen considerably the latent period of muscle contractions (+95%) considerably reduce (in 5.5 times) the speed of it contraction in first phase of contraction act and also considerably increase the time (+37%), which necessery for developing maximum strength of contraction. Thyroidactomia with general negative influence on ergothropic characteristics of isometric muscle contraction decrease considerably the expenditure of thermal energy on maximum strength of contraction unit (-17%) or on middle isometric tension unit (-9.3%).

  8. 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

  9. Rectus abdominis muscle resection and fascial reconstruction for the treatment of uterine leiomyosarcoma invading the abdominal wall: a case report.

    PubMed

    Yoon, B S; Seong, S J; Song, T; Kim, M L; Kim, M K

    2014-01-01

    The authors present a case of intra-abdominal recurrent leiomyosarcoma invading a large area of the abdominal wall. The patient underwent cytoreductive surgery, including resection of the rectus abdominis muscle, followed by reconstruction of the defect using synthetic mesh. The tumor was surgically removed by en bloc resection, including most of the rectus abdominis muscle and ileum. The abdominal wall defect was repaired using synthetic mesh. The patient underwent radiotherapy and chemotherapy after the surgery and was healthy one year later.

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

    PubMed Central

    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. PMID:28293331

  11. 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.

  12. 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.

  13. β-Adrenergic modulation of skeletal muscle contraction: key role of excitation-contraction coupling.

    PubMed

    Cairns, Simeon P; Borrani, Fabio

    2015-11-01

    Our aim is to describe the acute effects of catecholamines/β-adrenergic agonists on contraction of non-fatigued skeletal muscle in animals and humans, and explain the mechanisms involved. Adrenaline/β-agonists (0.1-30 μm) generally augment peak force across animal species (positive inotropic effect) and abbreviate relaxation of slow-twitch muscles (positive lusitropic effect). A peak force reduction also occurs in slow-twitch muscles in some conditions. β2 -Adrenoceptor stimulation activates distinct cyclic AMP-dependent protein kinases to phosphorylate multiple target proteins. β-Agonists modulate sarcolemmal processes (increased resting membrane potential and action potential amplitude) via enhanced Na(+) -K(+) pump and Na(+) -K(+) -2Cl(-) cotransporter function, but this does not increase force. Myofibrillar Ca(2+) sensitivity and maximum Ca(2+) -activated force are unchanged. All force potentiation involves amplified myoplasmic Ca(2+) transients consequent to increased Ca(2+) release from sarcoplasmic reticulum (SR). This unequivocally requires phosphorylation of SR Ca(2+) release channels/ryanodine receptors (RyR1) which sensitize the Ca(2+) -induced Ca(2+) release mechanism. Enhanced trans-sarcolemmal Ca(2+) influx through phosphorylated voltage-activated Ca(2+) channels contributes to force potentiation in diaphragm and amphibian muscle, but not mammalian limb muscle. Phosphorylation of phospholamban increases SR Ca(2+) pump activity in slow-twitch fibres but does not augment force; this process accelerates relaxation and may depress force. Greater Ca(2+) loading of SR may assist force potentiation in fast-twitch muscle. Some human studies show no significant force potentiation which appears to be related to the β-agonist concentration used. Indeed high-dose β-agonists (∼0.1 μm) enhance SR Ca(2+) -release rates, maximum voluntary contraction strength and peak Wingate power in trained humans. The combined findings can explain how adrenaline

  14. The effects of deep abdominal muscle strengthening exercises on respiratory function and lumbar stability.

    PubMed

    Kim, Eunyoung; Lee, Hanyong

    2013-06-01

    [Purpose] The purpose of this study was to examine the effects of deep abdominal muscle strengthening exercises on respiratory function and lumbar stability. [Subjects] From among 120 male and female students, 22 whose thoraxes opened no more than 5 cm during inspiration and expiration and whose forced expiratory flow rates were around 300 m/L were recruited. The subjects were randomly divided into an experimental group of eleven, who performed deep abdominal muscle strengthening exercises, and a control group of eleven, who received no particular intervention. [Methods] The subjects were instructed to perform normal breathing in the hook-lying position. They were then directed to hold their breath for ten seconds at the end of inspiration. Ten repetitions of this breathing comprised a set of respiratory training, and a total of five sets were performed by the subjects. [Results] Deep abdominal muscle training was effective at enhancing respiratory function and lumbar stabilization. [Conclusion] The clinical application of deep abdominal muscle strengthening exercises along with lumbar stabilization exercises should be effective for lower back pain patients in need of lumbar stabilization.

  15. Activation and intermuscular coherence of distal arm muscles during proximal muscle contraction.

    PubMed

    Lee, Sang Wook; Landers, Katlin; Harris-Love, Michelle L

    2014-03-01

    In the human upper extremity (UE), unintended effects of proximal muscle activation on muscles controlling the hand could be an important aspect of motor control due to the necessary coordination of distal and proximal segments during functional activities. This study aimed to elucidate the effects of concurrent activation of elbow muscles on the coordination between hand muscles performing a grip task. Eleven healthy subjects performed precision grip tasks while a constant extension or flexion moment was applied to their elbow joints, inducing a sustained submaximal contraction of elbow muscles to counter the applied torque. Activation of four hand muscles was measured during each task condition using surface electromyography (EMG). When concurrent activation of elbow muscles was induced, significant changes in the activation levels of the hand muscles were observed, with greater effects on the extrinsic finger extensor (23.2 % increase under 30 % elbow extensor activation; p = 0.003) than extrinsic finger flexor (14.2 % increase under 30 % elbow flexor activation; p = 0.130). Elbow muscle activation also induced involuntary changes in the intrinsic thumb flexor activation (44.6 % increase under 30 % elbow extensor activation; p = 0.005). EMG-EMG coherence analyses revealed that elbow muscle activation significantly reduced intermuscular coherence between distal muscle pairs, with its greatest effects on coherence in the β-band (13-25 Hz) (average of 17 % decrease under 30 % elbow flexor activation). The results of this study provide evidence for involuntary, muscle-specific interactions between distal and proximal UE muscles, which may contribute to UE motor performance in health and disease.

  16. Contractions

    MedlinePlus

    ... feel tightening of your uterus muscles at irregular intervals or a squeezing sensation in your lower abdomen ... beginning of childbirth. These contractions come at regular intervals, usually move from the back to the lower ...

  17. 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.

  18. Rac1 is a novel regulator of contraction-stimulated glucose uptake in skeletal muscle.

    PubMed

    Sylow, Lykke; Jensen, Thomas E; Kleinert, Maximilian; Mouatt, Joshua R; Maarbjerg, Stine J; Jeppesen, Jacob; Prats, Clara; Chiu, Tim T; Boguslavsky, Shlomit; Klip, Amira; Schjerling, Peter; Richter, Erik A

    2013-04-01

    In skeletal muscle, the actin cytoskeleton-regulating GTPase, Rac1, is necessary for insulin-dependent GLUT4 translocation. Muscle contraction increases glucose transport and represents an alternative signaling pathway to insulin. Whether Rac1 is activated by muscle contraction and regulates contraction-induced glucose uptake is unknown. Therefore, we studied the effects of in vivo exercise and ex vivo muscle contractions on Rac1 signaling and its regulatory role in glucose uptake in mice and humans. Muscle Rac1-GTP binding was increased after exercise in mice (~60-100%) and humans (~40%), and this activation was AMP-activated protein kinase independent. Rac1 inhibition reduced contraction-stimulated glucose uptake in mouse muscle by 55% in soleus and by 20-58% in extensor digitorum longus (EDL; P < 0.01). In agreement, the contraction-stimulated increment in glucose uptake was decreased by 27% (P = 0.1) and 40% (P < 0.05) in soleus and EDL muscles, respectively, of muscle-specific inducible Rac1 knockout mice. Furthermore, depolymerization of the actin cytoskeleton decreased contraction-stimulated glucose uptake by 100% and 62% (P < 0.01) in soleus and EDL muscles, respectively. These are the first data to show that Rac1 is activated during muscle contraction in murine and human skeletal muscle and suggest that Rac1 and possibly the actin cytoskeleton are novel regulators of contraction-stimulated glucose uptake.

  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. 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

  1. Reflex changes in muscle spindle discharge during a voluntary contraction.

    PubMed

    Aniss, A M; Gandevia, S C; Burke, D

    1988-03-01

    1. This study was undertaken to determine whether low-threshold cutaneous and muscle afferents from mechanoreceptors in the foot reflexly affect fusimotor neurons innervating the plantar and dorsiflexors of the ankle during voluntary contractions. 2. Recordings were made from 29 identified muscle spindle afferents innervating triceps surae and the pretibial flexors. Trains of electrical stimuli (5 stimuli, 300 impulses per second) were delivered to the sural nerve at the ankle (intensity: 2-4 times sensory threshold) and to the posterior tibial nerve at the ankle (intensity: 1.5-3 times motor threshold for the small muscles of the foot). The stimuli were delivered while the subject maintained an isometric voluntary contraction of the receptor-bearing muscle, sufficient to accelerate the discharge of each spindle ending. This ensured that the fusimotor neurons directed to the ending were active and influencing the spindle discharge. The effects of these stimuli on muscle spindle discharge were assessed using raster displays, frequencygrams, poststimulus time histograms (PSTHs) and cumulative sums ("CUSUMs") of the PSTHs. Reflex effects onto alpha-motoneurons were determined from poststimulus changes in the averaged rectified electromyogram (EMG). Reflex effects of these stimuli onto single-motor units were assessed in separate experiments using PSTHs and CUSUMs. 3. Electrical stimulation of the sural or posterior tibial nerves at nonnoxious levels had no significant effect on the discharge of the 14 spindle endings in the pretibial flexor muscles. The electrical stimuli also produced no significant change in discharge of 11 of 15 spindle endings in triceps surae. With the remaining four endings in triceps surae, the overall change in discharge appeared to be an increase for two endings (at latencies of 60 and 68 ms) and a decrease for two endings (at latencies of 110 and 150 ms). The difference in the incidence of the responses of spindle endings in tibialis

  2. 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.

  3. 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.

  4. NIRS monitoring of muscle contraction to control a prosthetic device

    NASA Astrophysics Data System (ADS)

    Bianchi, Thomas; Zambarbieri, Daniela; Beltrami, Giorgio; Verni, Gennaro

    1999-01-01

    The fitting of upper-extremity amputees requires special efforts, and its significance has been increased by the development of the myoelectrically controlled prosthetic arm. This solution is not free of problems due to the nature of the amputation, to the electromagnetic noise affecting the myelectrical signal and to the perspiration due to the contact between socket and the residual limb. Starting from the fact that NIRS and electromyographic signals are similar during a muscle contraction, we have first studied the NIRS signal during forearm muscle contractions in normal and amputee subjects. Then a new system to interface the NIRS unit and the myoelectrical prosthetic hand has been developed. The NIRS unit has been used as optical sensor and all the operations (I/O and signal processing) are performed via software. This system has been tested on normal and amputee subjects performing hand grasping using a visual biofeedback control scheme. All the subjects have been able to perform these operations demonstrating the NIRS technique. This could represent an alternative solution for controlling a prosthetic device.

  5. Ultrasound evaluation of the symmetry of abdominal muscles in mild adolescent idiopathic scoliosis

    PubMed Central

    Linek, Paweł; Saulicz, Edward; Wolny, Tomasz; Myśliwiec, Andrzej; Gogola, Anna

    2015-01-01

    [Purpose] The objective of the study was to evaluate the symmetry of the thickness of the abdominal muscles at rest and while standing in patients with adolescent idiopathic scoliosis. [Subjects and Methods] An ultrasound assessment was performed of the side-to-side differences of the external oblique (EO), internal oblique (IO), and transversus abdominalis (TrA) muscles in the supine and standing positions in adolescent idiopathic scoliosis (AIS) and control groups. [Results] In the AIS group, 64.3% of the patients had left scoliosis with a mean Cobb angle of 10.7°, and 35.7% of the patients had right scoliosis with a mean Cobb angle of 10°. In the supine position, the thickness asymmetry of the TrA was greater in the AIS compared with the control group by an average of 14% (95% CI 3.9–24.2). [Conclusion] Among the abdominal muscles examined, patients with AIS exhibited more asymmetry only for the TrA. In the standing position, the TrA was as symmetric in the patients as in the control group. Mild scoliosis has no impact on the symmetry of the thickness of the OE and OI in the supine and standing positions. The direction of curvature had no effect on the symmetry of the abdominal muscles studied. PMID:25729192

  6. 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

  7. Contraction of gut smooth muscle cells assessed by fluorescence imaging.

    PubMed

    Tokita, Yohei; Akiho, Hirotada; Nakamura, Kazuhiko; Ihara, Eikichi; Yamamoto, Masahiro

    2015-03-01

    Here we discuss the development of a novel cell imaging system for the evaluation of smooth muscle cell (SMC) contraction. SMCs were isolated from the circular and longitudinal muscular layers of mouse small intestine by enzymatic digestion. SMCs were stimulated by test agents, thereafter fixed in acrolein. Actin in fixed SMCs was stained with phalloidin and cell length was determined by measuring diameter at the large end of phalloidin-stained strings within the cells. The contractile response was taken as the decrease in the average length of a population of stimulated-SMCs. Various mediators and chemically identified compounds of daikenchuto (DKT), pharmaceutical-grade traditional Japanese prokinetics, were examined. Verification of the integrity of SMC morphology by phalloidin and DAPI staining and semi-automatic measurement of cell length using an imaging analyzer was a reliable method by which to quantify the contractile response. Serotonin, substance P, prostaglandin E2 and histamine induced SMC contraction in concentration-dependent manner. Two components of DKT, hydroxy-α-sanshool and hydroxy-β-sanshool, induced contraction of SMCs. We established a novel cell imaging technique to evaluate SMC contractility. This method may facilitate investigation into SMC activity and its role in gastrointestinal motility, and may assist in the discovery of new prokinetic agents.

  8. Role of excitation-contraction coupling in muscle fatigue.

    PubMed

    Allen, D G; Westerblad, H; Lee, J A; Lännergren, J

    1992-02-01

    The force produced by muscles declines during prolonged activity and this decline arises largely from processes within the muscle. At a cellular level the reduced force could be caused by: (a) reduced intracellular calcium release during activity; (b) reduced sensitivity of the myofilaments to calcium; or (c) reduced maximal force development. Experiments involving intracellular calcium measurements in isolated single fibres show that all 3 of the above contribute to the decline of force during fatigue. Metabolic changes associated with fatigue are probably involved in each of the 3 factors. Thus the accumulation of phosphate and protons which occur during fatigue cause a reduction in calcium sensitivity and a decline in maximal force. The cause of the reduced intracellular calcium during contractions in fatigue is less clear. During prolonged tetani the conduction of the action potential in the T-tubules appears to fail leading to reduced intracellular calcium in the central part of the muscle fibre. However, during repeated tetani there is a uniform decline of intracellular calcium across the fibre and this remains one of the least understood processes which contribute to fatigue.

  9. Effects of acidification and increased extracellular potassium on dynamic muscle contractions in isolated rat muscles.

    PubMed

    Overgaard, Kristian; Højfeldt, Grith Westergaard; Nielsen, Ole Bækgaard

    2010-12-15

    Since accumulation of both H(+) and extracellular K(+) have been implicated in the reduction in dynamic contractile function during intense exercise, we investigated the effects of acidification and high K(+) on muscle power and the force-velocity relation in non-fatigued rat soleus muscles. Contractions were elicited by supramaximal electrical stimulation at 60 Hz. Force-velocity (FV) curves were obtained by fitting data on force and shortening velocity at different loads to the Hill equation. Acidification of the muscles by incubation with up to 24 mm lactic acid produced no significant changes in maximal power (P(max)) at 30 °C. More pronounced acidification, obtained by increasing CO(2) levels in the equilibration gas from 5% to 53%, markedly decreased P(max) and maximal isometric force (F(max)), increased the curvature of the FV relation, but left maximal shortening velocity (V(max)) unchanged. Increase of extracellular K(+) from 4 to 10 mm caused a depression of 58% in P(max) and 52% in F(max), but had no significant effect on V(max) or curvature of the FV curve. When muscles at 10 mM K(+) were acidified by 20 mm lactic acid, P(max) and F(max) recovered completely to the initial control level at 4 mm K(+). CO(2) acidification also induced significant recovery of dynamic contractions, but not entirely to control levels. These results demonstrate that in non-fatigued muscles severe acidification can be detrimental to dynamic contractile function, but in muscles depolarised by exposure to high extracellular [K(+)], approaching the [K(+)] level seen during intense fatiguing exercise, acidification can have positive protective effects on dynamic muscle function.

  10. Preparation and execution of teeth clenching and foot muscle contraction influence on corticospinal hand-muscle excitability.

    PubMed

    Komeilipoor, Naeem; Ilmoniemi, Risto J; Tiippana, Kaisa; Vainio, Martti; Tiainen, Mikko; Vainio, Lari

    2017-01-24

    Contraction of a muscle modulates not only the corticospinal excitability (CSE) of the contracting muscle but also that of different muscles. We investigated to what extent the CSE of a hand muscle is modulated during preparation and execution of teeth clenching and ipsilateral foot dorsiflexion either separately or in combination. Hand-muscle CSE was estimated based on motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) and recorded from the first dorsal interosseous (FDI) muscle. We found higher excitability during both preparation and execution of all the motor tasks than during mere observation of a fixation cross. As expected, the excitability was greater during the execution phase than the preparation one. Furthermore, both execution and preparation of combined motor tasks led to higher excitability than individual tasks. These results extend our current understanding of the neural interactions underlying simultaneous contraction of muscles in different body parts.

  11. Preparation and execution of teeth clenching and foot muscle contraction influence on corticospinal hand-muscle excitability

    PubMed Central

    Komeilipoor, Naeem; Ilmoniemi, Risto J.; Tiippana, Kaisa; Vainio, Martti; Tiainen, Mikko; Vainio, Lari

    2017-01-01

    Contraction of a muscle modulates not only the corticospinal excitability (CSE) of the contracting muscle but also that of different muscles. We investigated to what extent the CSE of a hand muscle is modulated during preparation and execution of teeth clenching and ipsilateral foot dorsiflexion either separately or in combination. Hand-muscle CSE was estimated based on motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) and recorded from the first dorsal interosseous (FDI) muscle. We found higher excitability during both preparation and execution of all the motor tasks than during mere observation of a fixation cross. As expected, the excitability was greater during the execution phase than the preparation one. Furthermore, both execution and preparation of combined motor tasks led to higher excitability than individual tasks. These results extend our current understanding of the neural interactions underlying simultaneous contraction of muscles in different body parts. PMID:28117368

  12. Short-term effect of crunch exercise frequency on abdominal muscle endurance.

    PubMed

    Juan-Recio, C; López-Vivancos, A; Moya, M; Sarabia, J M; Vera-Garcia, F J

    2015-04-01

    Despite core exercise programs are broadly used to increase muscle function and to promote low back health, there is a lack of scientific evidence on some of the most important characteristics of trunk exercise programs, as for example training frequency. This study aimed to compare the short-term effect of training frequencies of 1, 2 and 3 days per week (d/wk) on abdominal muscle endurance in untrained adolescents. One hundred and eighteen high-school students (59 men and 59 women) with no previous experience in structured abdominal exercise programs were assigned randomly to groups that trained 1 d/wk (G1; N.=21), 2 d/wk (G2; N.=27), 3 d/wk (G3; N.=23), or to a control group (CG; N.=47) that did not train. The training groups performed crunch and cross-crunch exercises 1, 2 or 3 d/wk during six weeks. Before and after the training period, the bench trunk-curl test (BTC test) was carried out to assess abdominal muscle endurance. Men obtained higher BTC test scores than women before and after training. Training frequencies of 1, 2 and 3 d/wk provided a significant increase in BTC test scores; however, no significant differences between the three groups' scores were found after training. Therefore, a small dose of crunch exercise training (1 d/wk) may be sufficient stimulus to increase abdominal endurance in untrained male and female adolescents, at least during the first weeks of an abdominal exercise program, which seems a very relevant finding in terms of time-cost efficiency.

  13. Muscle injury induced by different types of contractions in dystrophic mdx mice.

    PubMed

    Lou, Jianwei; Bi, Wenbo; Li, Wei; Zhao, Yuying; Liu, Shuping; Zheng, Jinfan; Yan, Chuanzhu

    2012-03-01

    Studies on comparing the effect of lengthening, isometric and shortening contractions on dystrophin-deficient muscles are unavailable. We hypothesized that different types of contractions lead to different extents to which dystrophin-deficient muscles are injured. For this purpose, we developed protocols for different types of contraction-induced injury to mdx muscles in vitro. Force deficits and percentages of procion orange dye positive fibers were employed to assess the extent of injury to each muscle. Our results revealed that both the lengthening and isometric contractions resulted in significantly greater injury to extensor digitorum longus (EDL) muscles of mdx mice than to that of control (C57BL/6) mice. In contrast, the shortening contractions induced very mild and identical injury to EDL muscles of mdx and C57BL/6 mice. Then another protocol was carried out in vivo to ascertain the effect of shortening contractions on mdx muscles by achillotenotomy. Histological assessment revealed that the triceps surae muscles with excised Achilles tendon (EAT) displayed little and significantly milder injury than the normal ones did. In conclusions, the unloaded shortening contractions induce little injury to mdx muscles. The in vitro protocol for different types of contraction-induced injury is sensitive and reliable.

  14. Transcranial magnetic stimulation with the maximum voluntary muscle contraction facilitates motor neuron excitability and muscle force.

    PubMed

    Touge, Tetsuo; Urai, Yoshiteru; Ikeda, Kazuyo; Kume, Kodai; Deguchi, Kazushi

    2012-01-01

    Three trials of transcranial magnetic stimulation (TMS) during the maximum voluntary muscle contraction (MVC) were repeated at 15-minute intervals for 1 hour to examine the effects on motor evoked potentials (MEPs) in the digital muscles and pinching muscle force before and after 4 high-intensity TMSs (test 1 condition) or sham TMS (test 2 condition) with MVC. Under the placebo condition, real TMS with MVC was administered only before and 1 hour after the sham TMS with MVC. Magnetic stimulation at the foramen magnum level (FMS) with MVC was performed by the same protocol as that for the test 2 condition. As a result, MEP sizes in the digital muscles significantly increased after TMS with MVC under test conditions compared with the placebo conditions (P < 0.05). Pinching muscle force was significantly larger 45 minutes and 1 hour after TMS with MVC under the test conditions than under the placebo condition (P < 0.05). FMS significantly decreased MEP amplitudes 60 minutes after the sham TMS with MVC (P < 0.005). The present results suggest that intermittently repeated TMS with MVC facilitates motor neuron excitabilities and muscle force. However, further studies are needed to confirm the effects of TMS with MVC and its mechanism.

  15. Expiratory activation of abdominal muscle is associated with improved respiratory stability and an increase in minute ventilation in REM epochs of adult rats

    PubMed Central

    Andrews, Colin G.

    2015-01-01

    Breathing is more vulnerable to apneas and irregular breathing patterns during rapid eye movement (REM) sleep in both humans and rodents. We previously reported that robust and recurrent recruitment of expiratory abdominal (ABD) muscle activity is present in rats during REM epochs despite ongoing REM-induced muscle atonia in skeletal musculature. To develop a further understanding of the characteristics of ABD recruitment during REM epochs and their relationship with breathing patterns and irregularities, we sought to compare REM epochs that displayed ABD muscle recruitment with those that did not, within the same rats. Specifically, we investigated respiratory characteristics that preceded and followed recruitment. We hypothesized that ABD muscle recruitment would be likely to occur following respiratory irregularities and would subsequently contribute to respiratory stability and the maintenance of good ventilation following recruitment. Our data demonstrate that epochs of REM sleep containing ABD recruitments (REMABD+) were characterized by increased respiratory rate variability and increased presence of spontaneous brief central apneas. Within these epochs, respiratory events that displayed ABD muscle activation were preceded by periods of increased respiratory rate variability. Onset of ABD muscle activity increased tidal volume, amplitude of diaphragmatic contractions, and minute ventilation compared with the periods preceding ABD muscle activation. These results show that expiratory muscle activity is more likely recruited when respiration is irregular and its recruitment is subsequently associated with an increase in minute ventilation and a more regular respiratory rhythm. PMID:26338455

  16. Co-contraction modifies the stretch reflex elicited in muscles shortened by a joint perturbation

    PubMed Central

    Lewis, Gwyn N.; MacKinnon, Colum D.; Trumbower, Randy; Perreault, Eric J.

    2011-01-01

    Simultaneous contraction of agonist and antagonist muscles acting about a joint influences joint stiffness and stability. Although several studies have shown that reflexes in the muscle lengthened by a joint perturbation are modulated during co-contraction, little attention has been given to reflex regulation in the antagonist (shortened) muscle. The goal of the present study was to determine whether co-contraction gives rise to altered reflex regulation across the joint by examining reflexes in the muscle shortened by a joint perturbation. Reflexes were recorded from electromyographic activity in elbow flexors and extensors while positional perturbations to the elbow joint were applied. Perturbations were delivered during isolated activation of the flexor or extensor muscles as well as during flexor and extensor co-contraction. Across the group, the shortening reflex in the elbow extensor switched from suppression during isolated extensor muscle activation to facilitation during co-contraction. The shortening reflex in the elbow flexor remained suppressive during co-contraction but was significantly smaller compared to the response obtained during isolated elbow flexor activation. This response in the shortened muscle was graded by the level of activation in the lengthened muscle. The lengthening reflex did not change during co-contraction. These results support the idea that reflexes are regulated across multiple muscles around a joint. We speculate that the facilitatory response in the shortened muscle arises through a fast-conducting oligosynaptic pathway involving Ib interneurons. PMID:20878148

  17. Co-contraction modifies the stretch reflex elicited in muscles shortened by a joint perturbation.

    PubMed

    Lewis, Gwyn N; MacKinnon, Colum D; Trumbower, Randy; Perreault, Eric J

    2010-11-01

    Simultaneous contraction of agonist and antagonist muscles acting about a joint influences joint stiffness and stability. Although several studies have shown that reflexes in the muscle lengthened by a joint perturbation are modulated during co-contraction, little attention has been given to reflex regulation in the antagonist (shortened) muscle. The goal of the present study was to determine whether co-contraction gives rise to altered reflex regulation across the joint by examining reflexes in the muscle shortened by a joint perturbation. Reflexes were recorded from electromyographic activity in elbow flexors and extensors while positional perturbations to the elbow joint were applied. Perturbations were delivered during isolated activation of the flexor or extensor muscles as well as during flexor and extensor co-contraction. Across the group, the shortening reflex in the elbow extensor switched from suppression during isolated extensor muscle activation to facilitation during co-contraction. The shortening reflex in the elbow flexor remained suppressive during co-contraction but was significantly smaller compared to the response obtained during isolated elbow flexor activation. This response in the shortened muscle was graded by the level of activation in the lengthened muscle. The lengthening reflex did not change during co-contraction. These results support the idea that reflexes are regulated across multiple muscles around a joint. We speculate that the facilitatory response in the shortened muscle arises through a fast-conducting oligosynaptic pathway involving Ib interneurons.

  18. Skeletal muscle glucose uptake during contraction is regulated by nitric oxide and ROS independently of AMPK.

    PubMed

    Merry, Troy L; Steinberg, Gregory R; Lynch, Gordon S; McConell, Glenn K

    2010-03-01

    Reactive oxygen species (ROS) and nitric oxide (NO) have been implicated in the regulation of skeletal muscle glucose uptake during contraction, and there is evidence that they do so via interaction with AMP-activated protein kinase (AMPK). In this study, we tested the hypothesis that ROS and NO regulate skeletal muscle glucose uptake during contraction via an AMPK-independent mechanism. Isolated extensor digitorum longus (EDL) and soleus muscles from mice that expressed a muscle-specific kinase dead AMPKalpha2 isoform (AMPK-KD) and wild-type litter mates (WT) were stimulated to contract, and glucose uptake was measured in the presence or absence of the antioxidant N-acetyl-l-cysteine (NAC) or the nitric oxide synthase (NOS) inhibitor N(G)-monomethyl-l-arginine (l-NMMA). Contraction increased AMPKalpha2 activity in WT but not AMPK-KD EDL muscles. However, contraction increased glucose uptake in the EDL and soleus muscles of AMPK-KD and WT mice to a similar extent. In EDL muscles, NAC and l-NMMA prevented contraction-stimulated increases in oxidant levels (dichloroflourescein fluorescence) and NOS activity, respectively, and attenuated contraction-stimulated glucose uptake in both genotypes to a similar extent. In soleus muscles of AMPK-KD and WT mice, NAC prevented contraction-stimulated glucose uptake and l-NMMA had no effect. This is likely attributed to the relative lack of neuronal NOS in the soleus muscles compared with EDL muscles. Contraction increased AMPKalpha Thr(172) phosphorylation in EDL and soleus muscles of WT but not AMPK-KD mice, and this was not affected by NAC or l-NMMA treatment. In conclusion, ROS and NO are involved in regulating skeletal muscle glucose uptake during contraction via an AMPK-independent mechanism.

  19. Glucose uptake during contraction in isolated skeletal muscles from neuronal nitric oxide synthase μ knockout mice.

    PubMed

    Hong, Yet Hoi; Frugier, Tony; Zhang, Xinmei; Murphy, Robyn M; Lynch, Gordon S; Betik, Andrew C; Rattigan, Stephen; McConell, Glenn K

    2015-05-01

    Inhibition of nitric oxide synthase (NOS) significantly attenuates the increase in skeletal muscle glucose uptake during contraction/exercise, and a greater attenuation is observed in individuals with Type 2 diabetes compared with healthy individuals. Therefore, NO appears to play an important role in mediating muscle glucose uptake during contraction. In this study, we investigated the involvement of neuronal NOSμ (nNOSμ), the main NOS isoform activated during contraction, on skeletal muscle glucose uptake during ex vivo contraction. Extensor digitorum longus muscles were isolated from nNOSμ(-/-) and nNOSμ(+/+) mice. Muscles were contracted ex vivo in a temperature-controlled (30°C) organ bath with or without the presence of the NOS inhibitor N(G)-monomethyl-l-arginine (L-NMMA) and the NOS substrate L-arginine. Glucose uptake was determined by radioactive tracers. Skeletal muscle glucose uptake increased approximately fourfold during contraction in muscles from both nNOSμ(-/-) and nNOSμ(+/+) mice. L-NMMA significantly attenuated the increase in muscle glucose uptake during contraction in both genotypes. This attenuation was reversed by L-arginine, suggesting that L-NMMA attenuated the increase in muscle glucose uptake during contraction by inhibiting NOS and not via a nonspecific effect of the inhibitor. Low levels of NOS activity (~4%) were detected in muscles from nNOSμ(-/-) mice, and there was no evidence of compensation from other NOS isoform or AMP-activated protein kinase which is also involved in mediating muscle glucose uptake during contraction. These results indicate that NO regulates skeletal muscle glucose uptake during ex vivo contraction independently of nNOSμ.

  20. Axial disposition of myosin heads in isometrically contracting muscles.

    PubMed

    Juanhuix, J; Bordas, J; Campmany, J; Svensson, A; Bassford, M L; Narayanan, T

    2001-03-01

    Meridional x-ray diffraction diagrams, recorded with high angular resolution, from muscles contracting at the plateau of isometric tension show that the myosin diffraction orders are clusters of peaks. These clusters are due to pronounced interference effects between the myosin diffracting units on either side of the M-line. A theoretical analysis based on the polarity of the myosin (and actin) filaments shows that it is possible to extract phase information from which the axial disposition of the myosin heads can be determined. The results show that each head in a crown pair has a distinct structural disposition. It appears that only one of the heads in the pair stereospecifically interacts with the thin filament at any one time.

  1. Axial disposition of myosin heads in isometrically contracting muscles.

    PubMed Central

    Juanhuix, J; Bordas, J; Campmany, J; Svensson, A; Bassford, M L; Narayanan, T

    2001-01-01

    Meridional x-ray diffraction diagrams, recorded with high angular resolution, from muscles contracting at the plateau of isometric tension show that the myosin diffraction orders are clusters of peaks. These clusters are due to pronounced interference effects between the myosin diffracting units on either side of the M-line. A theoretical analysis based on the polarity of the myosin (and actin) filaments shows that it is possible to extract phase information from which the axial disposition of the myosin heads can be determined. The results show that each head in a crown pair has a distinct structural disposition. It appears that only one of the heads in the pair stereospecifically interacts with the thin filament at any one time. PMID:11222303

  2. Mechanistic role of movement and strain sensitivity in muscle contraction

    PubMed Central

    Davis, Julien S.; Epstein, Neal D.

    2009-01-01

    Tension generation can be studied by applying step perturbations to contracting muscle fibers and subdividing the mechanical response into exponential phases. The de novo tension-generating isomerization is associated with one of these phases. Earlier work has shown that a temperature jump perturbs the equilibrium constant directly to increase tension. Here, we show that a length jump functions quite differently. A step release (relative movement of thick and thin filaments) appears to release a steric constraint on an ensemble of noncompetent postphosphate release actomyosin cross-bridges, enabling them to generate tension, a concentration jump in effect. Structural studies [Taylor KA, et al. (1999) Tomographic 3D reconstruction of quick-frozen, Ca2+-activated contracting insect flight muscle. Cell 99:421–431] that map to these kinetics indicate that both catalytic and lever arm domains of noncompetent myosin heads change angle on actin, whereas lever arm movement alone mediates the power stroke. Together, these kinetic and structural observations show a 13-nm overall interaction distance of myosin with actin, including a final 4- to 6-nm power stroke when the catalytic domain is fixed on actin. Raising fiber temperature with both perturbation techniques accelerates the forward, but slows the reverse rate constant of tension generation, kinetics akin to the unfolding/folding of small proteins. Decreasing strain, however, causes both forward and reverse rate constants to increase. Despite these changes in rate, the equilibrium constant is strain-insensitive. Activation enthalpy and entropy data show this invariance to be the result of enthalpy–entropy compensation. Reaction amplitudes confirm a strain-invariant equilibrium constant and thus a strain-insensitive ratio of pretension- to tension-generating states as work is done. PMID:19325123

  3. Aging interferes central control mechanism for eccentric muscle contraction.

    PubMed

    Yao, Wan X; Li, Jinqi; Jiang, Zhiguo; Gao, Jia-Hong; Franklin, Crystal G; Huang, Yufei; Lancaster, Jack L; Yue, Guang H

    2014-01-01

    Previous studies report greater activation in the cortical motor network in controlling eccentric contraction (EC) than concentric contraction (CC) despite lower muscle activation level associated with EC vs. CC in healthy, young individuals. It is unknown, however, whether elderly people exhibiting increased difficulties in performing EC than CC possess this unique cortical control mechanism for EC movements. To address this question, we examined functional magnetic resonance imaging (fMRI) data acquired during EC and CC of the first dorsal interosseous (FDI) muscle in 11 young (20-32 years) and 9 old (67-73 years) individuals. During the fMRI experiment, all subjects performed 20 CC and 20 EC of the right FDI with the same angular distance and velocity. The major findings from the behavioral and fMRI data analysis were that (1) movement stability was poorer in EC than CC in the old but not the young group; (2) similar to previous electrophysiological and fMRI reports, the EC resulted in significantly stronger activation in the motor control network consisting of primary, secondary and association motor cortices than CC in the young and old groups; (3) the biased stronger activation towards EC was significantly greater in the old than the young group especially in the secondary and association cortices such as supplementary and premotor motor areas and anterior cingulate cortex; and (4) in the primary motor and sensory cortices, the biased activation towards EC was significantly greater in the young than the old group. Greater activation in higher-order cortical fields for controlling EC movement by elderly adults may reflect activities in these regions to compensate for aging-related impairments in the ability to control complex EC movements. Our finding is useful for potentially guiding the development of targeted therapies to counteract age-related movement deficits and to prevent injury.

  4. Relationships of Muscular Endurance Among Specific Muscle Groups for Continuous and Intermittent Static Contractions.

    ERIC Educational Resources Information Center

    Hoshizaki, Thomas B.; Massey, B. H.

    1986-01-01

    The static contraction endurance characteristics of five muscle groups were investigated in 38 normal, health, college-aged men. Four parameters of continuous and intermittent contractions were examined. Results support the hypothesis that endurance is unique to each muscle group and specific to the task performed. (Author/MT)

  5. Effect of muscle contraction strength on gating of somatosensory magnetic fields.

    PubMed

    Sugawara, Kazuhiro; Onishi, Hideaki; Yamashiro, Koya; Kotan, Shinichi; Kojima, Sho; Miyaguchi, Shota; Tsubaki, Atsuhiro; Kirimoto, Hikari; Tamaki, Hiroyuki; Shirozu, Hiroshi; Kameyama, Shigeki

    2016-11-01

    Afferent somatosensory information is modulated before the afferent input arrives at the primary somatosensory cortex during voluntary movement. The aim of the present study was to clarify the effect of muscular contraction strength on somatosensory evoked fields (SEFs) during voluntary movement. In addition, we examined the differences in gating between innervated and non-innervated muscle during contraction. We investigated the changes in gating effect by muscular contraction strength and innervated and non-innervated muscles in human using 306-channel magnetoencephalography. SEFs were recorded following the right median nerve stimulation in a resting condition and during isometric muscular contractions from 10 % electromyographic activity (EMG), 20 and 30 % EMG of the right extensor indicis muscle and abductor pollicis brevis muscle. Our results showed that the equivalent current dipole (ECD) strength for P35m decreased with increasing strength of muscular contraction of the right abductor pollicis brevis muscle. However, changes were observed only at 30 % EMG contraction level of the right extensor indicis muscle, which was not innervated by the median nerve. There were no significant changes in the peak latencies and ECD locations of each component in all conditions. The ECD strength did not differ significantly for N20m and P60m regardless of the strength of muscular contraction and innervation. Therefore, we suggest that the gating of SEF waveforms following peripheral nerve stimulation was affected by the strength of muscular contraction and innervation of the contracting muscle.

  6. Generation of Electrical Power from Stimulated Muscle Contractions Evaluated

    NASA Technical Reports Server (NTRS)

    Lewandowski, Beth; Kilgore, Kevin; Ercegovic, David B.

    2004-01-01

    This project is a collaborative effort between NASA Glenn Research Center's Revolutionary Aeropropulsion Concepts (RAC) Project, part of the NASA Aerospace Propulsion and Power Program of the Aerospace Technology Enterprise, and Case Western Reserve University's Cleveland Functional Electrical Stimulation (FES) Center. The RAC Project foresees implantable power requirements for future applications such as organically based sensor platforms and robotics that can interface with the human senses. One of the goals of the FES Center is to develop a totally implantable neural prosthesis. This goal is based on feedback from patients who would prefer a system with an internal power source over the currently used system with an external power source. The conversion system under investigation would transform the energy produced from a stimulated muscle contraction into electrical energy. We hypothesize that the output power of the system will be greater than the input power necessary to initiate, sustain, and control the electrical conversion system because of the stored potential energy of the muscle. If the system can be made biocompatible, durable, and with the potential for sustained use, then the biological power source will be a viable solution.

  7. The mechanism of spontaneous oscillatory contractions in skeletal muscle.

    PubMed

    Smith, D A; Stephenson, D G

    2009-05-06

    Most striated muscles generate steady contractile tension when activated, but some preparations, notably cardiac myocytes and slow-twitch fibers, may show spontaneous oscillatory contractions (SPOC) at low levels of activation. We have provided what we believe is new evidence that SPOC is a property of the contractile system at low actin-myosin affinity, whether caused by a thin-filament regulatory system or by other means. We present a quantitative single-sarcomere model for isotonic SPOC in skeletal muscle with three basic ingredients: i), actin and myosin filaments initially in partial overlap, ii), stretch activation by length-dependent changes in the lattice spacing, and iii), viscoelastic passive tension. Modeling examples are given for slow-twitch and fast-twitch fibers, with periods of 10 s and 4 s respectively. Isotonic SPOC occurs in a narrow domain of parameter values, with small minimum and maximum values for actin-myosin affinity, a minimum amount of passive tension, and a maximum transient response rate that explains why SPOC is favored in slow-twitch fibers. The model also predicts the contractile, relaxed and SPOC phases as a function of phosphate and ADP levels. The single-sarcomere model can also be applied to a whole fiber under auxotonic and fixed-end conditions if the remaining sarcomeres are treated as a viscoelastic load. Here the model predicts an upper limit for the load stiffness that leads to SPOC; this limit lies above the equivalent loads expected from the rest of the fiber.

  8. 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.

  9. Postnatal expression of myosin isoforms in an expiratory muscle--external abdominal oblique.

    PubMed

    Watchko, J F; Daood, M J; Vazquez, R L; Brozanski, B S; LaFramboise, W A; Guthrie, R D; Sieck, G C

    1992-11-01

    We studied the postnatal expression of heavy-chain (MHC) and native myosin isoforms in an expiratory abdominal muscle of the rat, the external abdominal oblique (EO). Moreover, we contrasted EO myosin expression with that of the costal diaphragm (DIA) to draw inspiratory vs. expiratory muscle comparisons during development. Examination of MHC gels demonstrated a mature phenotype of slow and adult fast myosin isoforms at an earlier age in the EO (day 60) than in the DIA [day > 115 (adult)]. The mature MHC phenotype of the EO was characterized by a preponderance of MHC 2B, whereas the DIA was characterized by approximately equal portions of MHC slow, MHC 2A, and MHC 2X. During early postnatal development, there was a delay in the expression of MHC 2A in the EO compared with the DIA. However, MHC 2B, expressed later in development in both muscles, was noted in the EO before the DIA. We conclude that 1) the EO mature myosin phenotype is characterized by a preponderance of fast myosin isoforms and 2) the EO and DIA muscles are subject to different temporal patterns of isoform expression during postnatal development.

  10. 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

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

    PubMed

    Crecelius, Anne R; Kirby, Brett S; Richards, Jennifer C; Dinenno, Frank A

    2013-04-01

    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.

  12. [Study of diaphragmatic muscle function during abdominal weight in normal subjects].

    PubMed

    Monteiro, Sergio G; Pessolano, Fernando A; Suárez, Adrián A; De Vito, Eduardo L

    2012-01-01

    The effects of the abdominal weight with the intention of producing training of the diaphragm, have not been sufficiently evaluated. We studied the function of the diaphragm during the abdominal weight training and during associated changes in the respiratory pattern. Six normal volunteers were studied. Flow at the mouth at functional residual capacity (FRC) was obtained as well as gastric pressure (Pga), esophageal pressure (Pes), thoracic and abdominal movements, maximal inspiratory pressure and mean and maximal transdiaphragmatic pressure (Pdi and Pdi max). Pdi/Pdimax and the diaphragm tension-time index (TTdi) were calculated. Studied steps: normal pattern (NP), abdominal pattern (AP) and weight of 1, 2, 4 and 6 kg with NP and AP as well. We found 1) The AP was facilitated by the abdominal weight, 2) Only with 6 kg (NP and AP) the Pga at FRC increased significantly (p 0.001), 3) the Pdi followed the variations of the Pga and increased with all the AP (p < 0.001), 4) The index TTdi load reached a value of 0.05 ± 0.02 (p < 0.001). The charges did not increase this rate more than did the AP alone. Our findings suggest abdominal weight increases propioception related to the respiratory movements and descent of the diaphragm. The loads on the abdomen produce minor changes in mechanics of the diaphragm (1/3 of the load required to develop fatigue in normal subjects). Al least in normal subjects these changes appear to be insufficient to produce respiratory muscle training.

  13. Laser-detected lateral muscle displacement is correlated with force fluctuations during voluntary contractions in humans.

    PubMed

    Yoshitake, Yasuhide; Masani, Kei; Shinohara, Minoru

    2008-08-30

    Fluctuations in muscle force during steady voluntary contractions result from the summation of twitch forces produced by asynchronous activation of multiple motor units. We hypothesized that oscillatory lateral muscle displacement, measured with a non-contact high-resolution laser displacement sensor, is correlated with force fluctuations during steady, voluntary contractions with a human muscle. Eight healthy young adults (20-33 yrs) performed steady isometric contractions with the first dorsal interosseus muscle. Contraction intensity ranged from 2.5% to 60% of the maximal voluntary contraction force. Oscillatory lateral displacement of the muscle surface was measured with a high-resolution laser displacement sensor (0.5 microm resolution), concurrently with abduction force of the index finger. In the time-domain analysis, there was a significant positive peak in the cross-correlation function between lateral muscle displacement and force fluctuations. In addition, the amplitude increased linearly with contraction intensity in both signals. In the frequency-domain analysis, frequency content was similar in both signals, and there was significant coherence between signals for the major frequency range of the signals (<5 Hz). In conclusion, laser-detected lateral displacement of a hand muscle is correlated with force fluctuations across a wide range of contraction intensity during steady voluntary contractions in humans.

  14. Weakness in mouse masticatory muscles by repetitive contractions with forced lengthening.

    PubMed

    Hutchins, M O; Skjonsby, H S; Brazeau, G A; Parikh, U K; Jenkins, R M

    1995-02-01

    The etiology of myofascial tenderness and pain of masticatory muscles in humans is difficult to understand. Parafunctional oral habits such as tooth grinding or vigorous chewing are thought to be factors. The objective of this study was to determine if masticatory muscles are susceptible to weakness and injury induced by repetitive, dynamic, forced-lengthening contractions. Results would support the hypothesis that contraction-induced injuries could occur in hyperactive masticatory muscles of humans in response to parafunctional oral habits. Mice were anesthetized and randomly assigned to three groups: non-treated controls, treated by repetitive passive jaw opening, or treated by repetitive isometric tetanic contractions with lengthening by jaw opening. In each treatment group, masticatory muscle injury was evaluated by contractile tension, plasma creatine kinase, and muscle glycogen. Contractile tension was determined at different stimulation frequencies and was significantly decreased 5 min, 4 h, and 72 h after repetitive contraction/lengthening. Plasma creatine kinase was significantly elevated at 4 but not at 72 h post-treatment in mice subjected to repetitive contraction/lengthening. Masticatory muscle glycogen was not significantly different in any groups at 4 or 72 h post-treatment. These results indicate that contraction injuries can be induced in masticatory muscle of mice by forced lengthening contractions which simulate eccentric contractions.

  15. 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.

  16. Abdominal lean muscle is associated with lower mortality among kidney waitlist candidates.

    PubMed

    Locke, Jayme E; Carr, J Jeffrey; Nair, Sangeeta; Terry, James G; Reed, Rhiannon D; Smith, Grant D; Segev, Dorry L; Kumar, Vineeta; Lewis, Cora E

    2017-03-01

    Morphometric assessments, such as muscle density and body fat distribution, have emerged as strong predictors of cardiovascular risk and postoperative morbidity and mortality. To date, no study has examined morphometric mortality risk prediction among kidney transplant (KT) candidates. KT candidates, waitlisted 2008-2009, were identified (n=96) and followed to the earliest of transplant, death, or administrative end of study. Morphometric measures, including abdominal adipose tissue, paraspinous and psoas muscle composition, and aortic calcification, were measured from CTs. Risk of waitlist mortality was examined using Cox proportional hazard regression. On adjusted analyses, radiologic measures remained independently and significantly associated with lower waitlist mortality; the addition of radiologic measures significantly improved model predictive ability over models containing traditional risk factors alone (net reclassification index: 0.56, 95% CI: 0.31-0.75). Higher psoas muscle attenuation (indicative of leaner muscle) was associated with decreased risk of death (aHR: 0.93, 95% CI: 0.91-0.96, P<.001), and for each unit increase in lean paraspinous volume, there was an associated 2% decreased risk for death (aHR: 0.98, 95% CI: 0.96-0.99, P=.03). Radiologic measures of lean muscle mass, such as psoas muscle attenuation and paraspinous lean volume, may improve waitlist mortality risk prediction and candidate selection.

  17. Effects of bridge exercises with a sling and vibrations on abdominal muscle thickness in healthy adults.

    PubMed

    Gong, Won-tae

    2015-01-01

    In the present study, we aimed to examine the changes in the thickness of the transversus abdominis (TrA) and internal oblique (Io) muscles using ultrasonography in adults who performed bridge exercises with the abdominal drawing-in maneuver and a sling and received micro vibrations. In total, 32 subjects were divided into a therapy (n= 16) and control (n= 16) groups. The therapy group completed nine sets, with four repetitions, of bridge exercises with the sling and received vibrations. The control group completed nine sets, with four repetitions, of bridge exercises with the sling and did not receive vibrations. The thicknesses of the TrA and Io muscles were measured in both groups using ultrasonography before and after therapy. According to the pressure applied to the biofeedback unit, both groups showed significant changes in the thicknesses of the TrA and Io muscles after therapy (P< 0.05). The change in the thickness of the TrA muscle after therapy was significantly different between the 2 groups when the pressures applied at 38, 42, and 46 mmHg (P< 0.05). Moreover, the change in the thickness of the Io muscle did not significantly different between the 2 groups at any of the pressures applied (P> 0.05). These findings indicate that approximately 15 minutes of vibrations during bridge exercises on unstable surfaces with a sling facilitates the activation of the deep trunk muscles and further enhances the activation of the TrA.

  18. Smooth muscle-selective CPI-17 expression increases vascular smooth muscle contraction and blood pressure

    PubMed Central

    Su, Wen; Xie, Zhongwen; Liu, Shu; Calderon, Lindsay E.; Guo, Zhenheng

    2013-01-01

    Recent data revealed that protein kinase C-potentiated myosin phosphatase inhibitor of 17 kDa (CPI-17), a myosin phosphatase inhibitory protein preferentially expressed in smooth muscle, is upregulated/activated in several diseases but whether this CPI-17 increase plays a causal role in pathologically enhanced vascular smooth muscle contractility and blood pressure remains unclear. To address this possibility, we generated a smooth muscle-specific CPI-17 transgenic mouse model (CPI-17-Tg) and demonstrated that the CPI-17 transgene was selectively expressed in smooth muscle-enriched tissues, including mesenteric arteries. The isometric contractions in the isolated second-order branch of mesenteric artery helical strips from CPI-17-Tg mice were significantly enhanced compared with controls in response to phenylephrine, U-46619, serotonin, ANG II, high potassium, and calcium. The perfusion pressure increases in isolated perfused mesenteric vascular beds in response to norepinephrine were also enhanced in CPI-17-Tg mice. The hypercontractility was associated with increased phosphorylation of CPI-17 and 20-kDa myosin light chain under basal and stimulated conditions. Surprisingly, the protein levels of rho kinase 2 and protein kinase Cα/δ were significantly increased in CPI-17-Tg mouse mesenteric arteries. Radiotelemetry measurements demonstrated that blood pressure was significantly increased in CPI-17-Tg mice. However, no vascular remodeling was detected by morphometric analysis. Taken together, our results demonstrate that increased CPI-17 expression in smooth muscle promotes vascular smooth muscle contractility and increases blood pressure, implicating a pathological significant role of CPI-17 upregulation. PMID:23604714

  19. Some Effects of Hypertonic Solutions on Contraction and Excitation-Contraction Coupling in Frog Skeletal Muscles

    PubMed Central

    Gordon, A. M.; Godt, R. E.

    1970-01-01

    In frog fast skeletal muscle, we find a decline of twitch, tetanus, and maximum K and caffeine contracture tensions as tonicity of the bathing solution is increased. The decline of tension independent of the method of producing contraction indicates that the major effect of hypertonicity is directly on contractile tension probably because of the increased internal ionic strength. However, there is some apparent disruption of excitation-contraction (E-C) coupling in solutions made three times the normal tonicity (3T solutions) since: (a) in 3T solutions tetanic and K contracture tensions decline to zero from a value near the average maximum caffeine contracture tension at this tonicity (10% of 1T tetanic tension). At this time, caffeine contractures of 10% of 1T tetanic tension can be elicited; (b) once the K contracture tension has declined, elevated [Ca++]o, 19.8 mM, restores K contracture tension to 13% of 1T tetanic tension. This probable disruption is not caused by changes in mechanical threshold since in 2T solutions the mechanical threshold is shifted by 12 mv in the hyperpolarizing direction. This is consistent with neutralization of fixed negative charges on the inside of the membrane. The repriming curve is also shifted in the hyperpolarizing direction in 2T solutions. Shifts of the repriming curve coupled with membrane depolarizations in 3T solutions (about 20 mv) may produce loss of repriming ability at the resting potential and disruption of E-C coupling. PMID:5415044

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

    PubMed

    Call, Jarrod A; Lowe, Dawn A

    2016-01-01

    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.

  1. Muscle shortening velocity depends on tissue inertia and level of activation during submaximal contractions.

    PubMed

    Ross, Stephanie A; Wakeling, James M

    2016-06-01

    In order to perform external work, muscles must do additional internal work to deform their tissue, and in particular, to overcome the inertia due to their internal mass. However, the contribution of the internal mass within a muscle to the mechanical output of that muscle has only rarely been studied. Here, we use a dynamic, multi-element Hill-type muscle model to examine the effects of the inertial mass within muscle on its contractile performance. We find that the maximum strain-rate of muscle is slower for lower activations and larger muscle sizes. As muscle size increases, the ability of the muscle to overcome its inertial load will decrease, as muscle tension is proportional to cross-sectional area and inertial load is proportional to mass. Thus, muscles that are larger in size will have a higher inertial cost to contraction. Similarly, when muscle size and inertial load are held constant, decreasing muscle activation will increase inertial cost to contraction by reducing muscle tension. These results show that inertial loads within muscle contribute to a slowing of muscle contractile velocities (strain-rates), particularly at the submaximal activations that are typical during animal locomotion.

  2. The phenomenological model of muscle contraction with a controller to simulate the excitation-contraction (E-C) coupling.

    PubMed

    Tamura, Youjiro; Saito, Masami; Ito, Akira

    2009-02-09

    We previously proposed a systematic motor model for muscle with two parallel Maxwell elements and a force generator P. The motor model showed the non-linear behavior of a muscle, such as the force-velocity relation and the force depression and enhancement, by using weight functions. Our newly proposed muscle model is based on the molecular mechanism of myosin cross-bridges. We assume that each parallel Maxwell element represents the mechanical properties of weak and strong binding of the myosin head to actin. Furthermore, we introduce a controller to simulate the excitation-contraction coupling of the muscle. The new muscle model satisfies all the properties obtained in our previous model and reduces the wasted energy of the viscous component to less than 5% of the total energy. The controller enables us to simulate contractions of slow and fast twitch muscles, which are driven by an artificial action potential or a processing electromyography signal despite their same mechanical components. The maximum velocities are calculated to be 3.4L(0)m/s for the fast twitch muscle model and 2.5L(0)m/s for the slow twitch muscle model, where L(0) is the initial length of the muscle model.

  3. The Mechanism of Spontaneous Oscillatory Contractions in Skeletal Muscle

    PubMed Central

    Smith, D.A.; Stephenson, D.G.

    2009-01-01

    Most striated muscles generate steady contractile tension when activated, but some preparations, notably cardiac myocytes and slow-twitch fibers, may show spontaneous oscillatory contractions (SPOC) at low levels of activation. We have provided what we believe is new evidence that SPOC is a property of the contractile system at low actin-myosin affinity, whether caused by a thin-filament regulatory system or by other means. We present a quantitative single-sarcomere model for isotonic SPOC in skeletal muscle with three basic ingredients: i), actin and myosin filaments initially in partial overlap, ii), stretch activation by length-dependent changes in the lattice spacing, and iii), viscoelastic passive tension. Modeling examples are given for slow-twitch and fast-twitch fibers, with periods of 10 s and 4 s respectively. Isotonic SPOC occurs in a narrow domain of parameter values, with small minimum and maximum values for actin-myosin affinity, a minimum amount of passive tension, and a maximum transient response rate that explains why SPOC is favored in slow–twitch fibers. The model also predicts the contractile, relaxed and SPOC phases as a function of phosphate and ADP levels. The single-sarcomere model can also be applied to a whole fiber under auxotonic and fixed-end conditions if the remaining sarcomeres are treated as a viscoelastic load. Here the model predicts an upper limit for the load stiffness that leads to SPOC; this limit lies above the equivalent loads expected from the rest of the fiber. PMID:19413973

  4. Force depression following muscle shortening in sub-maximal voluntary contractions of human adductor pollicis.

    PubMed

    Rousanoglou, Elissavet N; Oskouei, Ali E; Herzog, Walter

    2007-01-01

    Mechanical properties of skeletal muscles are often studied for controlled, electrically induced, maximal, or supra-maximal contractions. However, many mechanical properties, such as the force-length relationship and force enhancement following active muscle stretching, are quite different for maximal and sub-maximal, or electrically induced and voluntary contractions. Force depression, the loss of force observed following active muscle shortening, has been observed and is well documented for electrically induced and maximal voluntary contractions. Since sub-maximal voluntary contractions are arguably the most important for everyday movement analysis and for biomechanical models of skeletal muscle function, it is important to study force depression properties under these conditions. Therefore, the purpose of this study was to examine force depression following sub-maximal, voluntary contractions. Sets of isometric reference and isometric-shortening-isometric test contractions at 30% of maximal voluntary effort were performed with the adductor pollicis muscle. All reference and test contractions were executed by controlling force or activation using a feedback system. Test contractions included adductor pollicis shortening over 10 degrees, 20 degrees, and 30 degrees of thumb adduction. Force depression was assessed by comparing the steady-state isometric forces (activation control) or average electromyograms (EMGs) (force control) following active muscle shortening with those obtained in the corresponding isometric reference contractions. Force was decreased by 20% and average EMG was increased by 18% in the shortening test contractions compared to the isometric reference contractions. Furthermore, force depression was increased with increasing shortening amplitudes, and the relative magnitudes of force depression were similar to those found in electrically stimulated and maximal contractions. We conclude from these results that force depression occurs in sub

  5. The origin of activity in the biceps brachii muscle during voluntary contractions of the contralateral elbow flexor muscles.

    PubMed

    Zijdewind, Inge; Butler, Jane E; Gandevia, Simon C; Taylor, Janet L

    2006-11-01

    During strong voluntary contractions, activity is not restricted to the target muscles. Other muscles, including contralateral muscles, often contract. We used transcranial magnetic stimulation (TMS) to analyse the origin of these unintended contralateral contractions (termed "associated" contractions). Subjects (n = 9) performed maximal voluntary contractions (MVCs) with their right elbow-flexor muscles followed by submaximal contractions with their left elbow flexors. Electromyographic activity (EMG) during the submaximal contractions was matched to the associated EMG in the left biceps brachii during the right MVC. During contractions, TMS was delivered to the motor cortex of the right or left hemisphere and excitatory motor evoked potentials (MEPs) and inhibitory (silent period) responses recorded from left biceps. Changes at a spinal level were investigated using cervicomedullary stimulation to activate corticospinal paths (n = 5). Stimulation of the right hemisphere produced silent periods of comparable duration in associated and voluntary contractions (218 vs 217 ms, respectively), whereas left hemisphere stimulation caused a depression of EMG but no EMG silence in either contraction. Despite matched EMG, MEPs elicited by right hemisphere stimulation were approximately 1.5-2.5 times larger during associated compared to voluntary contractions (P < 0.005). Similar inhibition of the associated and matched voluntary activity during the silent period suggests that associated activity comes from the contralateral hemisphere and that motor areas in this (right) hemisphere are activated concomitantly with the motor areas in the left hemisphere. Comparison of the MEPs and subcortically evoked potentials implies that cortical excitability was greater in associated contractions than in the matched voluntary efforts.

  6. The effect of lumbar-pelvic alignment and abdominal muscle thickness on primary dysmenorrhea

    PubMed Central

    Kim, Moon-jeong; Baek, Il-hun; Goo, Bong-oh

    2016-01-01

    [Purpose] The purpose of this study was to identify effects of malalignment of the lumbar pelvis, as a passive element, and the thicknesses of abdominal muscles, as active elements, on primary dysmenorrhea. [Subjects and Methods] The subjects were divided into a primary dysmenorrhea group and normal group according to Visual Analogue Scale, and ultimately there were 28 subjects in the dysmenorrhea group and 22 subjects in the normal group. Alignment of the lumbar pelvis was measured by using a Formetric 4D analysis system, and the thicknesses of abdominal muscles were measured by using ultrasound imaging. [Result] Scoliosis was 6.7 ± 4.3° in the primary dysmenorrhea group and 3.8 ± 2.0° in the normal group, and the lordotic angles of the two groups were 0.6 ± 0.5° and 0.1 ± 0.3°, respectively. The thickness of the internal oblique was 3.8 ± 1.3 mm in the primary dysmenorrhea group and 6.0 ± 1.9 mm in the thicknesses of the transverse abdominis in the two groups were 2.6 ± 6.8 mm and 3.5 ± 6.1 mm, respectively. Furthermore, the thickness of the normal group, and the external oblique was 4.0 ± 0.8 mm in the primary dysmenorrhea group and 5.4 ± 1.4 mm in the normal group. [Conclusion] This study showed significant differences between the primary dysmenorrhea group and the normal group in lumbar-pelvic alignment and thicknesses of abdominal muscles. PMID:27821975

  7. Regulation of oscillatory contraction in insect flight muscle by troponin.

    PubMed

    Krzic, Uros; Rybin, Vladimir; Leonard, Kevin R; Linke, Wolfgang A; Bullard, Belinda

    2010-03-19

    Insect indirect flight muscle is activated by sinusoidal length change, which enables the muscle to work at high frequencies, and contracts isometrically in response to Ca(2+). Indirect flight muscle has two TnC isoforms: F1 binding a single Ca(2+) in the C-domain, and F2 binding Ca(2+) in the N- and C-domains. Fibres substituted with F1 produce delayed force in response to a single rapid stretch, and those with F2 produce isometric force in response to Ca(2+). We have studied the effect of TnC isoforms on oscillatory work. In native Lethocerus indicus fibres, oscillatory work was superimposed on a level of isometric force that depended on Ca(2+) concentration. Maximum work was produced at pCa 6.1; at higher concentrations, work decreased as isometric force increased. In fibres substituted with F1 alone, work continued to rise as Ca(2+) was increased up to pCa 4.7. Fibres substituted with various F1:F2 ratios produced maximal work at a ratio of 100:1 or 50:1; a higher proportion of F2 increased isometric force at the expense of oscillatory work. The F1:F2 ratio was 9.8:1 in native fibres, as measured by immunofluorescence, using isoform-specific antibodies. The small amount of F2 needed to restore work to levels obtained for the native fibre is likely to be due to the relative affinity of F1 and F2 for TnH, the Lethocerus homologue of TnI. Affinity of TnC isoforms for a TnI fragment of TnH was measured by isothermal titration calorimetry. The K(d) was 1.01 muM for F1 binding and 22.7 nM for F2. The higher affinity of F2 can be attributed to two TnH binding sites on F2 and a single site on F1. Stretch may be sensed by an extended C-terminal domain of TnH, resulting in reversible dissociation of the inhibitory sequence from actin during the oscillatory cycle.

  8. Slow expiration reduces sternocleidomastoid activity and increases transversus abdominis and internal oblique muscle activity during abdominal curl-up.

    PubMed

    Yoon, Tae-Lim; Kim, Ki-Song; Cynn, Heon-Seock

    2014-04-01

    The aim of this study was to investigate the effects of quiet inspiration versus slow expiration on sternocleidomastoid (SCM) and abdominal muscle activity during abdominal curl-up in healthy subjects. Twelve healthy subjects participated in this study. Surface electromyography (EMG) was used to collect activity of bilateral SCM, rectus abdominis (RA), external oblique (EO), and transversus abdominis/internal oblique (TrA/IO) muscles. A paired t-test was used to determine significant differences in the bilateral SCM, RF, EO, and TrA/IO muscles between abdominal curl-up with quiet inspiration and slow expiration. There were significantly lower EMG activity of both SCMs and greater EMG activity of both IOs during abdominal curl-up with slow expiration, compared with the EMG activity of both SCMs and IOs during abdominal curl-up with quiet inspiration (p<.05). The results of this study suggest that slow expiration would be recommended during abdominal curl-up for reduced SCM activation and selective activation of TrA/IO in healthy subjects compared with those in abdominal curl up with quiet inspiration.

  9. Effect of conditioning contraction intensity on postactivation potentiation is muscle dependent.

    PubMed

    Fukutani, Atsuki; Hirata, Kosuke; Miyamoto, Naokazu; Kanehisa, Hiroaki; Yanai, Toshimasa; Kawakami, Yasuo

    2014-04-01

    We aimed to examine whether the influence of conditioning contraction intensity on the extent of postactivation potentiation (PAP) is muscle dependent. Eleven healthy males performed both thumb adduction and plantar flexion as a conditioning contraction. The conditioning contraction intensities were set at 20%, 40%, 60%, 80%, or 100% of the maximal voluntary isometric contraction (MVC). Before and after the conditioning contraction, twitch torque was measured for the respective joint to calculate the extent of PAP. In plantar flexion, the extent of PAP became significantly larger as the conditioning contraction intensity increased up to 80% MVC (p<0.05). In contrast, the extent of PAP in thumb adduction increased significantly only up to 60% MVC (p<0.05), but not at higher intensities. These results indicate that the influence of the conditioning contraction intensity on the extent of PAP is muscle dependent. Our results suggest that a conditioning contraction with submaximal intensity can sufficiently evoke sizable PAP in the muscle where most of muscle fibers are recruited at submaximal intensities, thereby attenuating muscle fatigue induced by the conditioning contraction.

  10. 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.

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

    PubMed

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

    2011-12-01

    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/cm(2), 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.

  12. 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%.

  13. Changes in glucose 1,6-bisphosphate content in rat skeletal muscle during contraction.

    PubMed Central

    Bassols, A M; Carreras, J; Cussó, R

    1986-01-01

    Glucose 1,6-bisphosphate, fructose 2,6-bisphosphate, glycogen, lactate and other glycolytic metabolites were measured in rat gastrocnemius muscle, which was electrically stimulated in situ via the sciatic nerve. Both the frequency and the duration of stimulation were varied to obtain different rates of glycolysis. There was no apparent relationship between fructose 2,6-bisphosphate content and lactate accumulation in contracting muscle. In contrast, glucose 1,6-bisphosphate content increased with lactate concentration during contraction. It is suggested that the increase in glucose 1,6-bisphosphate could play a role in phosphofructokinase stimulation and in the activation of the glycolytic flux during muscle contraction. PMID:3827864

  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. The effects of isometric contraction of shoulder muscles on cervical multifidus muscle dimensions in healthy office workers.

    PubMed

    Rahnama, Leila; Rezasoltani, Asghar; Khalkhali Zavieh, Minoo; Noori Kochi, Farhang; Akbarzadeh Baghban, Alireza

    2014-07-01

    It is argued that cervical multifidus muscles (CMM) are responsible for providing neck stability. However, whether they are actually activated during the tasks performed by the upper extremities to the neck is still unknown. Therefore, the aim of this study was to examine the effects of isometric contraction of shoulder muscles on the dimensions of CMM. Twenty three healthy males voluntarily participated in this study. Ultrasonography imaging of CMM was conducted at rest and at 25%, 50%, 75%, and 100% of maximal voluntary contraction of shoulder muscles in 6 directions of shoulder movements. Anterior-posterior dimension (APD), lateral dimension (LD), shape ratio and multiplied linear dimension (MLD) of cervical multifidus were measured. The APD of CMM was increased while LD and shape ratio were decreased by shoulder muscles contraction (P < 0.01).

  16. 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.

  17. Muscle co-contraction modulates damping and joint stability in a three-link biomechanical limb.

    PubMed

    Heitmann, Stewart; Ferns, Norm; Breakspear, Michael

    2011-01-01

    Computational models of neuromotor control require forward models of limb movement that can replicate the natural relationships between muscle activation and joint dynamics without the burdens of excessive anatomical detail. We present a model of a three-link biomechanical limb that emphasizes the dynamics of limb movement within a simplified two-dimensional framework. Muscle co-contraction effects were incorporated into the model by flanking each joint with a pair of antagonist muscles that may be activated independently. Muscle co-contraction is known to alter the damping and stiffness of limb joints without altering net joint torque. Idealized muscle actuators were implemented using the Voigt muscle model which incorporates the parallel elasticity of muscle and tendon but omits series elasticity. The natural force-length-velocity relationships of contractile muscle tissue were incorporated into the actuators using ideal mathematical forms. Numerical stability analysis confirmed that co-contraction of these simplified actuators increased damping in the biomechanical limb consistent with observations of human motor control. Dynamic changes in joint stiffness were excluded by the omission of series elasticity. The analysis also revealed the unexpected finding that distinct stable (bistable) equilibrium positions can co-exist under identical levels of muscle co-contraction. We map the conditions under which bistability arises and prove analytically that monostability (equifinality) is guaranteed when the antagonist muscles are identical. Lastly we verify these analytic findings in the full biomechanical limb model.

  18. Muscle Co-Contraction Modulates Damping and Joint Stability in a Three-Link Biomechanical Limb

    PubMed Central

    Heitmann, Stewart; Ferns, Norm; Breakspear, Michael

    2012-01-01

    Computational models of neuromotor control require forward models of limb movement that can replicate the natural relationships between muscle activation and joint dynamics without the burdens of excessive anatomical detail. We present a model of a three-link biomechanical limb that emphasizes the dynamics of limb movement within a simplified two-dimensional framework. Muscle co-contraction effects were incorporated into the model by flanking each joint with a pair of antagonist muscles that may be activated independently. Muscle co-contraction is known to alter the damping and stiffness of limb joints without altering net joint torque. Idealized muscle actuators were implemented using the Voigt muscle model which incorporates the parallel elasticity of muscle and tendon but omits series elasticity. The natural force-length-velocity relationships of contractile muscle tissue were incorporated into the actuators using ideal mathematical forms. Numerical stability analysis confirmed that co-contraction of these simplified actuators increased damping in the biomechanical limb consistent with observations of human motor control. Dynamic changes in joint stiffness were excluded by the omission of series elasticity. The analysis also revealed the unexpected finding that distinct stable (bistable) equilibrium positions can co-exist under identical levels of muscle co-contraction. We map the conditions under which bistability arises and prove analytically that monostability (equifinality) is guaranteed when the antagonist muscles are identical. Lastly we verify these analytic findings in the full biomechanical limb model. PMID:22275897

  19. Soleus muscle in glycosylation-deficient muscular dystrophy is protected from contraction-induced injury.

    PubMed

    Gumerson, Jessica D; Kabaeva, Zhyldyz T; Davis, Carol S; Faulkner, John A; Michele, Daniel E

    2010-12-01

    The glycosylation of dystroglycan is required for its function as a high-affinity laminin receptor, and loss of dystroglycan glycosylation results in congenital muscular dystrophy. The purpose of this study was to investigate the functional defects in slow- and fast-twitch muscles of glycosylation-deficient Large(myd) mice. While a partial alteration in glycosylation of dystroglycan in heterozygous Large(myd/+) mice was not sufficient to alter muscle function, homozygous Large(myd/myd) mice demonstrated a marked reduction in specific force in both soleus and extensor digitorum longus (EDL) muscles. Although EDL muscles from Large(myd/myd) mice were highly susceptible to lengthening contraction-induced injury, Large(myd/myd) soleus muscles surprisingly showed no greater force deficit compared with wild-type soleus muscles even after five lengthening contractions. Despite no increased susceptibility to injury, Large(myd/myd) soleus muscles showed loss of dystroglycan glycosylation and laminin binding activity and dystrophic pathology. Interestingly, we show that soleus muscles have a markedly higher sarcolemma expression of β(1)-containing integrins compared with EDL and gastrocnemius muscles. Therefore, we conclude that β(1)-containing integrins play an important role as matrix receptors in protecting muscles containing slow-twitch fibers from contraction-induced injury in the absence of dystroglycan function, and that contraction-induced injury appears to be a separable phenotype from the dystrophic pathology of muscular dystrophy.

  20. Consistency of rapid muscle force characteristics: influence of muscle contraction onset detection methodology.

    PubMed

    Thompson, Brennan J; Ryan, Eric D; Herda, Trent J; Costa, Pablo B; Walter, Ashley A; Sobolewski, Eric J; Cramer, Joel T

    2012-12-01

    The purpose of this study was to investigate the consistency of commonly reported rapid force characteristics utilizing both automated and manual muscle contraction onset detection methods. Twenty-four healthy volunteers performed isometric strength testing of the plantar flexor muscle group on two nonconsecutive days. Test-retest reliability was evaluated using intraclass correlation coefficients (ICCs), standard errors of measurement (SEM), and the SEM as a percentage of the mean (SEM%) for rate of force development (RFD), relative RFD, contractile impulse, and absolute force-time values at various epoch durations using automated and manual onset detection methods. For all rapid force variables, ICC and SEM% values ranged from 0.52 to 0.96 and 7.56% to 37.56%, respectively. For the majority of these variables (20 of 23), the automated onset detection method resulted in higher ICC and lower SEM% values compared to the manual onset detection method. Regardless of onset detection methodology, the consistency of relative RFD values declined following 50% of MVC. Collectively, these findings indicated that commonly evaluated rapid muscle force variables demonstrated acceptable relative and absolute consistency values. However, these values were generally superior for the automated onset detection methodology. Additionally, the consistency of relative RFD values declines following 50% MVC and therefore should be evaluated with caution.

  1. The vestibular system does not modulate fusimotor drive to muscle spindles in contracting leg muscles of seated subjects.

    PubMed

    Bent, L R; Sander, M; Bolton, P S; Macefield, V G

    2013-06-01

    We previously showed that sinusoidal galvanic vestibular stimulation (GVS) does not modulate the firing of spontaneously active muscle spindles in relaxed human leg muscles. However, given that there is little, if any, fusimotor drive to relaxed human muscles, we tested the hypothesis that vestibular modulation of muscle spindles becomes apparent during volitional contractions at levels that engage the fusimotor system. Unitary recordings were made from 28 muscle spindle afferents via tungsten microelectrodes inserted percutaneously into the common peroneal nerve of seated awake human subjects. Twenty-one of the spindle afferents were spontaneously active at rest and each increased its firing rate during a weak static contraction; seven were silent at rest and were recruited during the contraction. Sinusoidal bipolar binaural galvanic vestibular stimulation (±2 mA, 100 cycles) was applied to the mastoid processes at 0.8 Hz. This continuous stimulation produced a sustained illusion of "rocking in a boat" or "swinging in a hammock" but no entrainment of EMG. Despite these robust vestibular illusions, none of the fusimotor-driven muscle spindles exhibited phase-locked modulation of firing during sinusoidal GVS. We conclude that this dynamic vestibular input was not sufficient to modulate the firing of fusimotor neurones recruited during a voluntary steady-state contraction, arguing against a significant role of the vestibular system in adjusting the sensitivity of muscle spindles via fusimotor neurones.

  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 Central

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

    2016-01-01

    Background 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. Objectives 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. Methods 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). Results 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. Conclusions 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. PMID:28144414

  3. 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.

  4. 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

  5. Sources of calcium for contraction of distal circular muscle or taenia coli in the rabbit.

    PubMed

    Sevy, N; Snape, W J

    1988-06-01

    Studies were performed on proximal taenia coli and distal circular muscle from the rabbit to determine if the source of Ca2+ required for bethanechol stimulation of contraction was similar after permeabilizing the tissues with saponin. The EC50 for Ca2+ stimulation of contraction was pCa 6.1 +/- 0.1 for both tissues. The peak response occurred at pCa 4.5. The addition of 1 microM calmodulin did not alter the Ca2+ EC50 or the peak response. Caffeine (20 mM) stimulated contraction of both taenia coli and distal circular muscle. The caffeine-stimulated contractile response was threefold greater in the taenia than in the distal circular muscle (P less than 0.05). Perfusion of thin strips of colonic muscle with buffer, containing 10(-7) M Ca2+, reduced the amplitude of bethanechol-stimulated contraction. The perfusion time to reduce the contraction by 50% was greater in the proximal muscle (2.4 +/- 0.1 min) than in the distal muscle (1.1 +/- 0.5 min) (P less than 0.001). These data suggest that 1) the intracellular Ca2+ concentration necessary for contraction is similar in the proximal and distal colon and 2) the intracellular Ca2+ stores appear to be greater in proximal taenia coli compared with distal circular muscle.

  6. A continuum model for excitation-contraction of smooth muscle under finite deformations.

    PubMed

    Sharifimajd, Babak; Stålhand, Jonas

    2014-08-21

    The main focus in most of the continuum based muscle models is the mechanics of muscle contraction while other physiological processes governing muscle contraction, e.g., cell membrane excitation and activation, are ignored. These latter processes are essential to initiate contraction and to determine the amount of generated force, and by excluding them, the developed model cannot replicate the true behavior of the muscle in question. The aim of this study is to establish a thermodynamically and physiologically consistent framework which allows us to model smooth muscle contraction by including cell membrane excitability and kinetics of myosin phosphorylation, along with dynamics of smooth muscle contraction. The model accounts for these processes through a set of coupled dissipative constitutive equations derived by applying first principles. To show the performance of the derived model, it is evaluated for two different cases: a chemo-mechanical study of pig taenia coli cells where the excitation process is excluded, and an electro-chemo-mechanical study of rat myometrium. The results show that the model is able to replicate important aspects of the smooth muscle excitation-contraction process.

  7. Influence of Hamstring and Abdominal Muscle Activation on a Positive Ober's Test in People with Lumbopelvic Pain

    PubMed Central

    Tenney, H. Rich; DeBord, Aaron

    2013-01-01

    ABSTRACT Purpose: To assess the immediate effect of hamstring and abdominal activation on pain levels as measured by the Numeric Pain Scale (NPS) and hip range of motion as measured by Ober's Test in people with lumbopelvic pain. Methods: Thirteen participants with lumbopelvic pain and positive Ober's Tests completed an exercise developed by the Postural Restoration Institute™ to recruit hamstrings and abdominal muscles. Results: There was a significant increase in passive hip-adduction angles (p<0.01) and decrease in pain (p<0.01) immediately after the intervention. Conclusion: Specific exercises that activate hamstrings and abdominal muscles appear to immediately improve Ober's Test measurements and reduce pain as measured by the NPS in people with lumbo-pelvic pain. Hamstring/abdominal activation, rather than iliotibial band stretching, may be an effective intervention for addressing lumbopelvic pain and a positive Ober's Test. PMID:24381375

  8. Ballistic contractions in fast or slow human muscles; discharge patterns of single motor units

    PubMed Central

    Desmedt, John E.; Godaux, Emile

    1978-01-01

    1. Single motor units were recorded from the masseter, soleus and first dorsal interosseous muscles of normal adult man. An analysis of discharge patterns was carried out either during slow ramp voluntary contractions, or during self-initiated isolated ballistic voluntary contractions. The isometric myogram was simultaneously recorded. 2. Each motor unit was only recruited when the peak force of a brisk contraction exceeded a certain value and a `ballistic force threshold' (in kg) was estimated for the unit from a large series of brisk contractions of different strengths. For each muscle, the ranking order for recruitment of different motor units recorded from one electrode position was virtually identical in slow ramp versus brisk ballistic contractions of different force (Kendall rank correlation coefficient = 0·91-1·0). There was no evidence for any consistent selective activation of fast twitch motor units in ballistic contractions. 3. The ballistic force threshold is considerably reduced with respect to the slow ramp force threshold for the motor units of the soleus muscle. This drop is also marked for the units of the first interosseous and tibialis anterior muscles, whereas it is only small for the units of the masseter muscle. These data have been validated after consideration of the complicating factor related to the possible differential involvement of synergic muscles in ramp or ballistic contractions. 4. In the masseter and first interosseous muscles, the time to peak is about 80 msec in small ballistic voluntary contractions and it increases to about 150 msec in strong contractions. This effect appears related to repetitive discharges of single motor units when their force threshold is exceeded. By contrast, in the soleus muscle, the time to peak remains at about 150 msec both in small and in strong ballistic contractions and most soleus motor units fire only one spike in the ballistic burst. 5. Brisk ballistic contractions are graded in force by the

  9. 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

  10. 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.

  11. An ionic-chemical-mechanical model for muscle contraction.

    PubMed

    Manning, Gerald S

    2016-12-01

    The dynamic process underlying muscle contraction is the parallel sliding of thin actin filaments along an immobile thick myosin fiber powered by oar-like movements of protruding myosin cross bridges (myosin heads). The free energy for functioning of the myosin nanomotor comes from the hydrolysis of ATP bound to the myosin heads. The unit step of translational movement is based on a mechanical-chemical cycle involving ATP binding to myosin, hydrolysis of the bound ATP with ultimate release of the hydrolysis products, stress-generating conformational changes in the myosin cross bridge, and relief of built-up stress in the myosin power stroke. The cycle is regulated by a transition between weak and strong actin-myosin binding affinities. The dissociation of the weakly bound complex by addition of salt indicates the electrostatic basis for the weak affinity, while structural studies demonstrate that electrostatic interactions among negatively charged amino acid residues of actin and positively charged residues of myosin are involved in the strong binding interface. We therefore conjecture that intermediate states of increasing actin-myosin engagement during the weak-to-strong binding transition also involve electrostatic interactions. Methods of polymer solution physics have shown that the thin actin filament can be regarded in some of its aspects as a net negatively charged polyelectrolyte. Here we employ polyelectrolyte theory to suggest how actin-myosin electrostatic interactions might be of significance in the intermediate stages of binding, ensuring an engaged power stroke of the myosin motor that transmits force to the actin filament, and preventing the motor from getting stuck in a metastable pre-power stroke state. We provide electrostatic force estimates that are in the pN range known to operate in the cycle.

  12. Electromyography of superficial and deep neck muscles during isometric, voluntary, and reflex contractions.

    PubMed

    Siegmund, Gunter P; Blouin, Jean-Sébastien; Brault, John R; Hedenstierna, Sofia; Inglis, J Timothy

    2007-02-01

    Increasingly complex models of the neck neuromusculature need detailed muscle and kinematic data for proper validation. The goal of this study was to measure the electromyographic activity of superficial and deep neck muscles during tasks involving isometric, voluntary, and reflexively evoked contractions of the neck muscles. Three male subjects (28-41 years) had electromyographic (EMG) fine wires inserted into the left sternocleidomastoid, levator scapulae, trapezius, splenius capitis, semispinalis capitis, semispinalis cervicis, and multifidus muscles. Surface electrodes were placed over the left sternohyoid muscle. Subjects then performed: (i) maximal voluntary contractions (MVCs) in the eight directions (45 deg intervals) from the neutral posture; (ii) 50 N isometric contractions with a slow sweep of the force direction through 720 deg; (iii) voluntary oscillatory head movements in flexion and extension; and (iv) initially relaxed reflex muscle activations to a forward acceleration while seated on a sled. Isometric contractions were performed against an overhead load cell and movement dynamics were measured using six-axis accelerometry on the head and torso. In all three subjects, the two anterior neck muscles had similar preferred activation directions and acted synergistically in both dynamic tasks. With the exception of splenius capitis, the posterior and posterolateral neck muscles also showed consistent activation directions and acted synergistically during the voluntary motions, but not during the sled perturbations. These findings suggest that the common numerical-modeling assumption that all anterior muscles act synergistically as flexors is reasonable, but that the related assumption that all posterior muscles act synergistically as extensors is not. Despite the small number of subjects, the data presented here can be used to inform and validate a neck model at three levels of increasing neuromuscular-kinematic complexity: muscles generating forces

  13. The difference between standing and sitting in 3 different seat inclinations on abdominal muscle activity and chest and abdominal expansion in woodwind and brass musicians

    PubMed Central

    Ackermann, Bronwen J.; O'Dwyer, Nicholas; Halaki, Mark

    2014-01-01

    Wind instrumentalists require a sophisticated functioning of their respiratory system to control their air stream, which provides the power for optimal musical performance. The air supply must be delivered into the instrument in a steady and controlled manner and with enough power by the action of the expiratory musculature to produce the desired level of sound at the correct pitch. It is suggested that playing posture may have an impact on the abdominal muscle activity controlling this expired air, but there is no research on musicians to support this theory. This study evaluated chest and abdominal expansion, via respiratory inductive plethysmography, as well as activation patterns of lower and upper abdominal musculature, using surface electromyography, during performance of a range of typical orchestral repertoire by 113 woodwind and brass players. Each of the five orchestral excerpts was played in one of four randomly allocated postures: standing; sitting flat; sitting inclined forwards; and sitting inclined backwards. Musicians showed a clear preference for playing in standing rather than sitting. In standing, the chest expansion range and maximum values were greater (p < 0.01), while the abdominal expansion was less than in all sitting postures (p < 0.01). Chest expansion patterns did not vary between the three sitting postures, while abdominal expansion was reduced in the forward inclined posture compared to the other sitting postures (p < 0.05). There was no significant variation in abdominal muscle activation between the sitting postures, but the level of activation in sitting was only 2/3 of the significantly higher level observed in standing (p < 0.01). This study has demonstrated significant differences in respiratory mechanics between sitting and standing postures in wind musicians during playing of typical orchestral repertoire. Further research is needed to clarify the complex respiratory mechanisms supporting musical performance. PMID:25202290

  14. The difference between standing and sitting in 3 different seat inclinations on abdominal muscle activity and chest and abdominal expansion in woodwind and brass musicians.

    PubMed

    Ackermann, Bronwen J; O'Dwyer, Nicholas; Halaki, Mark

    2014-01-01

    Wind instrumentalists require a sophisticated functioning of their respiratory system to control their air stream, which provides the power for optimal musical performance. The air supply must be delivered into the instrument in a steady and controlled manner and with enough power by the action of the expiratory musculature to produce the desired level of sound at the correct pitch. It is suggested that playing posture may have an impact on the abdominal muscle activity controlling this expired air, but there is no research on musicians to support this theory. This study evaluated chest and abdominal expansion, via respiratory inductive plethysmography, as well as activation patterns of lower and upper abdominal musculature, using surface electromyography, during performance of a range of typical orchestral repertoire by 113 woodwind and brass players. Each of the five orchestral excerpts was played in one of four randomly allocated postures: standing; sitting flat; sitting inclined forwards; and sitting inclined backwards. Musicians showed a clear preference for playing in standing rather than sitting. In standing, the chest expansion range and maximum values were greater (p < 0.01), while the abdominal expansion was less than in all sitting postures (p < 0.01). Chest expansion patterns did not vary between the three sitting postures, while abdominal expansion was reduced in the forward inclined posture compared to the other sitting postures (p < 0.05). There was no significant variation in abdominal muscle activation between the sitting postures, but the level of activation in sitting was only 2/3 of the significantly higher level observed in standing (p < 0.01). This study has demonstrated significant differences in respiratory mechanics between sitting and standing postures in wind musicians during playing of typical orchestral repertoire. Further research is needed to clarify the complex respiratory mechanisms supporting musical performance.

  15. 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.

  16. Finite element model of intramuscular pressure during isometric contraction of skeletal muscle.

    PubMed

    Jenkyn, Thomas R; Koopman, Bart; Huijing, Peter; Lieber, Richard L; Kaufman, Kenton R

    2002-11-21

    The measurement of in vivo intramuscular pressure (IMP) has recently become practical and IMP appears well correlated with muscle tension. A numerical model of skeletal muscle was developed to examine the mechanisms producing IMP. Unipennate muscle is modelled as a two-dimensional material continuum that is incompressible and nonlinearly anisotropic. The finite element technique is used to calculate IMP and muscle stress during passive stretch and during isometric contraction. A novel element models the contractile portion of muscle, incorporating sarcomere length-force and velocity-force relations. A range of unipennate muscle geometries can be modelled. The model was configured to simulate the rabbit tibialis anterior muscle over a range of lengths. Simulated IMP and stress results were validated against animal experimentation data. The simulation agreed well with the experimental data over the range of 0.8-1.1 of the optimal length. Severe pressure gradients were produced near the musculo-tendinous junctions while IMP was more uniform in the central muscle belly. IMP and muscle stress in relaxed (unstimulated) muscle increased nonlinearly with muscle length. IMP and stress in isometrically contracting muscle showed a local maximum at optimal length and were reduced at shorter lengths. At muscle lengths longer than optimal, stress and IMP increased predominately due to tension in the passive elastic structures.

  17. 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.

  18. Reconstruction of Abdominal Wall Defects Using a Pedicled Anterolateral Thigh Flap including the Vastus Lateralis Muscle: A Report of Two Cases

    PubMed Central

    Fujioka, Masaki; Ishiyama, Satoko

    2016-01-01

    The purpose of abdominal wall reconstruction is to prevent hernias and protect the abdominal viscera. In cases involving full-thickness defects of the rectus abdominis muscle, the muscle layer should be repaired. We present 2 cases in which full-thickness lower rectus abdominis muscle defects were reconstructed using vastus lateralis-anterolateral thigh flaps. The pedicled vastus lateralis-anterolateral thigh flap provides skin, fascia, and muscle tissue. Furthermore, it has a long neurovascular pedicle and can reach up to the periumbilical area and cover large defects. We consider that this muscle flap is a good option for repairing full-thickness lower abdominal defects. PMID:28074168

  19. From action potential to contraction: neural control and excitation-contraction coupling in larval muscles of Drosophila.

    PubMed

    Peron, Samantha; Zordan, Mauro A; Magnabosco, Anna; Reggiani, Carlo; Megighian, Aram

    2009-10-01

    The neuromuscular system of Drosophila melanogaster has been studied for many years for its relative simplicity and because of the genetic and molecular versatilities. Three main types of striated muscles are present in this dipteran: fibrillar muscles, tubular muscles and supercontractile muscles. The visceral muscles in adult flies and the body wall segmental muscles in embryos and larvae belong to the group of supercontractile muscles. Larval body wall muscles have been the object of detailed studies as a model for neuromuscular junction function but have received much less attention with respect to their mechanical properties and to the control of contraction. In this review we wish to assess available information on the physiology of the Drosophila larval muscular system. Our aim is to establish whether this system has the requisites to be considered a good model in which to perform a functional characterization of Drosophila genes, with a known muscular expression, as well as Drosophila homologs of human genes, the dysfunction of which, is known to be associated with human hereditary muscle pathologies.

  20. [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.

  1. [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.

  2. PPARδ agonism inhibits skeletal muscle PDC activity, mitochondrial ATP production and force generation during prolonged contraction

    PubMed Central

    Constantin-Teodosiu, Dumitru; Baker, David J; Constantin, Despina; Greenhaff, Paul L

    2009-01-01

    We have recently shown that PPARδ agonism, used clinically to treat insulin resistance, increases fat oxidation and up-regulates mitochondrial PDK4 mRNA and protein expression in resting skeletal muscle. We hypothesized that PDK4 up-regulation, which inhibits pyruvate dehydrogenase complex (PDC)-dependent carbohydrate (CHO) oxidation, would negatively affect muscle function during sustained contraction where the demand on CHO is markedly increased. Three groups of eight male Wistar rats each received either vehicle or a PPARδ agonist (GW610742X) at two doses (5 and 100 mg (kg body mass (bm))−1 orally for 6 days. On the seventh day, the gastrocnemius–soleus–plantaris muscle group was isolated and snap frozen, or underwent 30 min of electrically evoked submaximal intensity isometric contraction using a perfused hindlimb model. During contraction, the rate of muscle PDC activation was significantly lower at 100 mg (kg bm)−1 compared with control (P < 0.01). Furthermore, the rates of muscle PCr hydrolysis and lactate accumulation were significantly increased at 100 mg (kg bm)−1 compared with control, reflecting lower mitochondrial ATP generation. Muscle tension development during contraction was significantly lower at 100 mg (kg bm)−1 compared with control (25%; P < 0.05). The present data demonstrate that PPARδ agonism inhibits muscle CHO oxidation at the level of PDC during prolonged contraction, and is paralleled by the activation of anaerobic metabolism, which collectively impair contractile function. PMID:19001043

  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. 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.

  5. 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.

  6. Simulating the activation, contraction and movement of skeletal muscles using the bidomain model.

    PubMed

    Lopez Rincon, A; Cantu, C; Soto, R; Shimoda, S

    2016-08-01

    A simulation of the muscle activation, contraction and movement is here presented. This system was developed based on the Bidomain mathematical model of the electrical propagation in muscles. This study shows an electrical stimuli input to a muscle and how this behave. The comparison between healthy subject and patient with muscle activation impairment is depicted, depending on whether the signal reaches a threshold. A 3D model of a bicep muscle and a forearm bone connected was constructed using OpenGL. This platform could be used for development of controllers for biomechatronic systems in future works. This kind of bioinspired model could be used for a better understanding of the neuromotor system.

  7. 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…

  8. AICAR stimulation metabolome widely mimics electrical contraction in isolated rat epitrochlearis muscle.

    PubMed

    Miyamoto, Licht; Egawa, Tatsuro; Oshima, Rieko; Kurogi, Eriko; Tomida, Yosuke; Tsuchiya, Koichiro; Hayashi, Tatsuya

    2013-12-15

    Physical exercise has potent therapeutic and preventive effects against metabolic disorders. A number of studies have suggested that 5'-AMP-activated protein kinase (AMPK) plays a pivotal role in regulating carbohydrate and lipid metabolism in contracting skeletal muscles, while several genetically manipulated animal models revealed the significance of AMPK-independent pathways. To elucidate significance of AMPK and AMPK-independent signals in contracting skeletal muscles, we conducted a metabolomic analysis that compared the metabolic effects of 5-aminoimidazole-4-carboxamide-1-β-D-ribonucleoside (AICAR) stimulation with the electrical contraction ex vivo in isolated rat epitrochlearis muscles, in which both α1- and α2-isoforms of AMPK and glucose uptake were equally activated. The metabolomic analysis using capillary electrophoresis time-of-flight mass spectrometry detected 184 peaks and successfully annotated 132 small molecules. AICAR stimulation exhibited high similarity to the electrical contraction in overall metabolites. Principal component analysis (PCA) demonstrated that the major principal component characterized common effects whereas the minor principal component distinguished the difference. PCA and a factor analysis suggested a substantial change in redox status as a result of AMPK activation. We also found a decrease in reduced glutathione levels in both AICAR-stimulated and contracting muscles. The muscle contraction-evoked influences related to the metabolism of amino acids, in particular, aspartate, alanine, or lysine, are supposed to be independent of AMPK activation. Our results substantiate the significance of AMPK activation in contracting skeletal muscles and provide novel evidence that AICAR stimulation closely mimics the metabolomic changes in the contracting skeletal muscles.

  9. Quantification of muscle co-contraction using supersonic shear wave imaging.

    PubMed

    Raiteri, Brent J; Hug, François; Cresswell, Andrew G; Lichtwark, Glen A

    2016-02-08

    Muscle stiffness estimated using shear wave elastography can provide an index of individual muscle force during isometric contraction and may therefore be a promising method for quantifying co-contraction. We estimated the shear modulus of the lateral gastrocnemius (LG) muscle using supersonic shear wave imaging and measured its myoelectrical activity using surface electromyography (sEMG) during graded isometric contractions of plantar flexion and dorsiflexion (n=7). During dorsiflexion, the average shear modulus was 26 ± 6 kPa at peak sEMG amplitude, which was significantly less (P=0.02) than that measured at the same sEMG level during plantar flexion (42 ± 10 kPa). The passive tension during contraction was estimated using the passive LG muscle shear modulus during a passive ankle rotation measured at an equivalent ankle angle to that measured during contraction. The passive shear modulus increased significantly (P<0.01) from the plantar flexed position (16 ± 5 kPa) to the dorsiflexed position (26 ± 9 kPa). Once this change in passive tension from joint rotation was accounted for, the average LG muscle shear modulus due to active contraction was significantly greater (P<0.01) during plantar flexion (26 ± 8 kPa) than at sEMG-matched levels of dorsiflexion (0 ± 4 kPa). The negligible shear modulus estimated during isometric dorsiflexion indicates negligible active force contribution by the LG muscle, despite measured sEMG activity of 19% of maximal voluntary plantar flexion contraction. This strongly suggests that the sEMG activity recorded from the LG muscle during isometric dorsiflexion was primarily due to cross-talk. However, it is clear that passive muscle tension changes can contribute to joint torque during isometric dorsiflexion.

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

    PubMed

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

    2017-12-01

    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 Ca(2+) 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.

  11. 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.

  12. Individuals with chronic low back pain do not modulate the level of transversus abdominis muscle contraction across different postures.

    PubMed

    Miura, Takuya; Yamanaka, Masanori; Ukishiro, Kengo; Tohyama, Harukazu; Saito, Hiroshi; Samukawa, Mina; Kobayashi, Takumi; Ino, Takumi; Takeda, Naoki

    2014-12-01

    The aim of this study was to evaluate the thickness of the transversus abdominis (TrA) muscle in three basic postures in subjects with and without chronic low back pain. Subjects were classified into a chronic low back pain group (n = 27) and a healthy control group (n = 23). The thickness of the TrA muscle was measured at rest and during the abdominal drawing-in manoeuvre (ADIM) in supine, sitting and standing postures using B-mode ultrasound imaging. Contraction ratio (TrA thickness during the ADIM/TrA thickness at rest) was calculated for each posture. At rest, the TrA thickness in the sitting and standing postures was significantly greater than in the supine posture (p < 0.017) in the control group, but similar in all three postures in the low back pain group. TrA thickness was similar in the low back pain and control group in all three postures. During the ADIM, TrA thickness was significantly greater in the control group than in the chronic low back pain group in all three postures. The contraction ratio was also significantly higher in the control group than in the chronic low back pain group in all three postures. These results indicate that the automatic postural contraction of the TrA observed in the control subjects in the sitting and standing postures was not demonstrated in subjects with chronic low back pain. The present study revealed the one aspect of different response of the TrA muscle to changing posture between two groups.

  13. Effects of divergent resistance exercise contraction mode and dietary supplementation type on anabolic signalling, muscle protein synthesis and muscle hypertrophy.

    PubMed

    Rahbek, Stine Klejs; Farup, Jean; Møller, Andreas Buch; Vendelbo, Mikkel Holm; Holm, Lars; Jessen, Niels; Vissing, Kristian

    2014-10-01

    Greater force produced with eccentric (ECC) compared to concentric (CONC) contractions, may comprise a stronger driver of muscle growth, which may be further augmented by protein supplementation. We investigated the effect of differentiated contraction mode with either whey protein hydrolysate and carbohydrate (WPH + CHO) or isocaloric carbohydrate (CHO) supplementation on regulation of anabolic signalling, muscle protein synthesis (MPS) and muscle hypertrophy. Twenty-four human participants performed unilateral isolated maximal ECC versus CONC contractions during exercise habituation, single-bout exercise and 12 weeks of training combined with WPH + CHO or CHO supplements. In the exercise-habituated state, p-mTOR, p-p70S6K, p-rpS6 increased by approximately 42, 206 and 213 %, respectively, at 1 h post-exercise, with resistance exercise per se; whereas, the phosphorylation was exclusively maintained with ECC at 3 and 5 h post-exercise. This acute anabolic signalling response did not differ between the isocaloric supplement types, neither did protein fractional synthesis rate differ between interventions. Twelve weeks of ECC as well as CONC resistance training augmented hypertrophy with WPH + CHO group compared to the CHO group (7.3 ± 1.0 versus 3.4 ± 0.8 %), independently of exercise contraction type. Training did not produce major changes in basal levels of Akt-mTOR pathway components. In conclusion, maximal ECC contraction mode may constitute a superior driver of acute anabolic signalling that may not be mirrored in the muscle protein synthesis rate. Furthermore, with prolonged high-volume resistance training, contraction mode seems less influential on the magnitude of muscle hypertrophy, whereas protein and carbohydrate supplementation augments muscle hypertrophy as compared to isocaloric carbohydrate supplementation .

  14. Position sense at the human forearm after conditioning elbow muscles with isometric contractions.

    PubMed

    Tsay, A; Allen, T J; Proske, U

    2015-09-01

    These experiments were designed to test the idea that, in a forearm position-matching task, it is the difference in afferent signals coming from the antagonist muscles of the forearm that determines the perceived position of the arm. In one experiment, flexor and then extensor muscles of the reference arm were conditioned by isometric voluntary contractions while the arm was held at the test angle, approximately 45° from the horizontal. At the same time, indicator arm flexor muscles were contracted while the arm was flexed, or extensors were contracted while it was extended. After an indicator flexor contraction, during matching, subjects made large errors in the direction of flexion, by 9.3° relative to the reference arm and after an indicator extensor contraction by 7.4° in the direction of extension. In the second experiment, with reference muscles conditioned as before, slack was introduced in indicator muscles by a combination of muscle contraction and stretch. This was expected to lower levels of afferent activity in indicator muscles. The subsequent matching experiment yielded much smaller errors than before, 1.4° in the direction of flexion. In both experiments, signal levels coming from the reference arm remained the same and what changed was the level of indicator signal. The fact that matching errors were small when slack was introduced in indicator muscles supported the view that the signal coming from reference muscles was also small. It was concluded that the brain is concerned with the signal difference from the antagonist pair of each arm and with the total signal difference between the two arms.

  15. Eccentric exercise slows in vivo microvascular reactivity during brief contractions in human skeletal muscle.

    PubMed

    Larsen, Ryan G; Hirata, Rogerio P; Madzak, Adnan; Frøkjær, Jens B; Graven-Nielsen, Thomas

    2015-12-01

    Unaccustomed exercise involving eccentric contractions results in muscle soreness and an overall decline in muscle function, however, little is known about the effects of eccentric exercise on microvascular reactivity in human skeletal muscle. Fourteen healthy men and women performed eccentric contractions of the dorsiflexor muscles in one leg, while the contralateral leg served as a control. At baseline, and 24 and 48 h after eccentric exercise, the following were acquired bilaterally in the tibialis anterior muscle: 1) transverse relaxation time (T2)-weighted magnetic resonance images to determine muscle cross-sectional area (mCSA) and T2; 2) blood oxygen level-dependent (BOLD) images during and following brief, maximal voluntary contractions (MVC) to monitor the hyperemic responses with participants positioned supine in a 3T magnet; 3) muscle strength; and 4) pain pressure threshold. Compared with the control leg, eccentric exercise resulted in soreness, decline in strength (∼20%), increased mCSA (∼7%), and prolonged T2 (∼7%) at 24 and 48 h (P < 0.05). The BOLD response to a brief MVC was altered 24 and 48 h after eccentric exercise, such that time-to-peak (∼35%, P < 0.05) and time-to-half-recovery (∼23%, P < 0.05) were prolonged. The altered contraction-induced hyperemic response suggests slowed microvascular reactivity and altered matching of O2 delivery to O2 utilization within muscle tissue showing signs of muscle damage. These changes in microvascular regulation after eccentric exercise may impede rapid adjustments in muscle blood flow at exercise onset and during activities involving brief bursts of muscle activation, which may impair O2 delivery and contribute to reduced muscle function after eccentric exercise.

  16. Downstream mechanisms of nitric oxide-mediated skeletal muscle glucose uptake during contraction.

    PubMed

    Merry, Troy L; Lynch, Gordon S; McConell, Glenn K

    2010-12-01

    There is evidence that nitric oxide (NO) is required for the normal increases in skeletal muscle glucose uptake during contraction, but the mechanisms involved have not been elucidated. We examined whether NO regulates glucose uptake during skeletal muscle contractions via cGMP-dependent or cGMP-independent pathways. Isolated extensor digitorum longus (EDL) muscles from mice were stimulated to contract ex vivo, and potential NO signaling pathways were blocked by the addition of inhibitors to the incubation medium. Contraction increased (P < 0.05) NO synthase (NOS) activity (∼40%) and dichlorofluorescein (DCF) fluorescence (a marker of oxidant levels; ∼95%), which was prevented with a NOS inhibitor N(G)-monomethyl-L-arginine (L-NMMA), and antioxidants [nonspecific antioxidant, N-acetylcysteine (NAC); thiol-reducing agent, DTT], respectively. L-NMMA and NAC both attenuated glucose uptake during contraction by ∼50% (P < 0.05), and their effects were not additive. Neither the guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one, which prevents the formation of cGMP, the cGMP-dependent protein (PKG) inhibitor Rp-8-bromo-β-phenyl-1,N2-ethenoguanosine 3',5'-cyclic monophosphorothioate sodium salt nor white light, which breaks S-nitrosylated bonds, affects glucose uptake during contraction; however, DTT attenuated (P < 0.05) contraction-stimulated glucose uptake (by 70%). NOS inhibition and antioxidant treatment reduced contraction-stimulated increases in protein S-glutathionylation and tyrosine nitration (P < 0.05), without affecting AMPK or p38 MAPK phosphorylation. In conclusion, we provide evidence to suggest that NOS-derived oxidants regulate skeletal muscle glucose uptake during ex vivo contractions via a cGMP/PKG-, AMPK-, and p38 MAPK-independent pathway. In addition, it appears that NO and ROS may regulate skeletal muscle glucose uptake during contraction through a similar pathway.

  17. Distribution of forces between synergistics and antagonistics muscles using an optimization criterion depending on muscle contraction behavior.

    PubMed

    Rengifo, Carlos; Aoustin, Yannick; Plestan, Franck; Chevallereau, Christine

    2010-04-01

    In this paper, a new neuromusculoskeletal simulation strategy is proposed. It is based on a cascade control approach with an inner muscular-force control loop and an outer joint-position control loop. The originality of the work is located in the optimization criterion used to distribute forces between synergistic and antagonistic muscles. The cost function and the inequality constraints depend on an estimation of the muscle fiber length and its time derivative. The advantages of a such criterion are exposed by theoretical analysis and numerical tests. The simulation model used in the numerical tests consists in an anthropomorphic arm model composed by two joints and six muscles. Each muscle is modeled as a second-order dynamical system including activation and contraction dynamics. Contraction dynamics is represented using a classical Hill's model.

  18. 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.

  19. Tetanic contractions impair sarcomeric Z-disk of atrophic soleus muscle via calpain pathway.

    PubMed

    Ma, Xiao-Wu; Li, Quan; Xu, Peng-Tao; Zhang, Lin; Li, Hui; Yu, Zhi-Bin

    2011-08-01

    The aim of this study was to determine whether or not over-activation of calpains during running exercise or tetanic contractions was a major factor to induce sarcomere lesions in atrophic soleus muscle. Relationship between the degrees of desmin degradation and sarcomere lesions was also elucidated. We observed ultrastructural changes in soleus muscle fibers after 4-week unloading with or without running exercise. Calpain activity and desmin degradation were measured in atrophic soleus muscles before or after repeated tetani in vitro. Calpain-1 activity was progressively increased and desmin degradation was correspondingly elevated in 1-, 2-, and 4-week of unloaded soleus muscles. Calpain-1 activity and desmin degradation had an additional increase in unloaded soleus muscles after repeated tetani in vitro. PD150606, an inhibitor of calpains, reduced calpain activity and desmin degradation during tetanic contractions in unloaded soleus muscles. The 4-week unloading decreased the width of myofibrils and Z-disk in soleus fibers. After running exercise in unloaded group, Z-disks of adjacent myofibrils were not well in register but instead were longitudinally displaced. Calpain inhibition compromised exercise-induced misalignment of the Z-disks in atrophic soleus muscle. These results suggest that tetanic contractions induce an over-activation of calpains which lead to higher degrees of desmin degradation in unloaded soleus muscle. Desmin degradation may loose connections between adjacent myofibrils, whereas running exercise results in sarcomere injury in unloaded soleus muscle.

  20. Monitoring of variations in the speed of sound in contracting and relaxing muscle

    NASA Astrophysics Data System (ADS)

    Hossain, M. Zakir; Voigt, Horst; Grill, Wolfgang

    2009-03-01

    Beside of changes in the shape of contracting and relaxing muscle, which can be monitored with ultrasound, also changes in the velocity of ultrasound are expected. To observe such changes with high resolution for the gastrocnemius muscle of athletes a novel detection scheme has been developed. As already introduced for the detection of sideways expansion of the muscle, ultrasonic transducers are mounted sideways on opposing positions of the skin. To detect variations of the speed of sound, the expansion of the muscle is suppressed by mechanical clamping. Under this condition, any variation in the time-of-flight of ultrasonic signals can only be introduced by a variation of the speed of sound along the path of the ultrasound transit signal. The observed rather small variations of the speed of sound are compared to the signals obtained by ultrasound monitoring for the extension and contraction observed for free sideways motion (unclamped muscle). Opposite to the general behavior of a free muscle the clamped muscle shows a diminishing time-of-flight under contraction relating to an increase in the sound velocity. Since clamping also reduces effects of inertia, the influence of inertia on muscle dynamics can be illustrated by comparison of measurements on clamped and free muscle.

  1. Captopril augments acetylcholine-induced bronchial smooth muscle contractions in vitro via kinin-dependent mechanisms.

    PubMed

    Agrawal, Naman; Akella, Aparna; Deshpande, Shripad B

    2016-06-01

    Angiotensin converting enzyme (ACE) inhibitors therapy is aassociated with bothersome dry cough as an adverse effect. The mechanisms underlying this adverse effect are not clear. Therefore, influence of captopril (an ACE inhibitor) on acetylcholine (ACh)-induced bronchial smooth muscle contractions was investigated. Further, the mechanisms underlying the captopril-induced changes were also explored. In vitro contractions of rat bronchial smooth muscle to cumulative concentrations of ACh were recorded before and after exposure to captopril. Further, the involvement of kinin and inositol triphosphate (IP₃) pathways for captopril-induced alterations were explored. ACh produced concentration-dependent (5-500 µM) increase in bronchial smooth muscle contractions. Pre-treatment with captopril augmented the ACh-induced contractions at each concentration significantly. Pre-treatment with aprotinin (kinin synthesis inhibitor) or heparin (inositol triphosphate, IP₃-inhibitor), blocked the captopril-induced augmentation of bronchial smooth muscle contractions evoked by ACh. Further, captopril-induced augmentation was absent in calcium-free medium. These results suggest that captopril sensitizes bronchial smooth muscles to ACh-induced contractions. This sensitization may be responsible for dry cough associated with captopril therapy.

  2. Different motor learning effects on excitability changes of motor cortex in muscle contraction state.

    PubMed

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

    2013-09-01

    We aimed to investigate whether motor learning induces different excitability changes in the human motor cortex (M1) between two different muscle contraction states (before voluntary contraction [static] or during voluntary contraction [dynamic]). For the same, using motor evoked potentials (MEPs) obtained by transcranial magnetic stimulation (TMS), we compared excitability changes during these two states after pinch-grip motor skill learning. The participants performed a force output tracking task by pinch grip on a computer screen. TMS was applied prior to the pinch grip (static) and after initiation of voluntary contraction (dynamic). MEPs of the following muscles were recorded: first dorsal interosseous (FDI), thenar muscle (Thenar), flexor carpi radialis (FCR), and extensor carpi radialis (ECR) muscles. During both the states, motor skill training led to significant improvement of motor performance. During the static state, MEPs of the FDI muscle were significantly facilitated after motor learning; however, during the dynamic state, MEPs of the FDI, Thenar, and FCR muscles were significantly decreased. Based on the results of this study, we concluded that excitability changes in the human M1 are differentially influenced during different voluntary contraction states (static and dynamic) after motor learning.

  3. Akt activation prevents the force drop induced by eccentric contractions in dystrophin-deficient skeletal muscle.

    PubMed

    Blaauw, Bert; Mammucari, Cristina; Toniolo, Luana; Agatea, Lisa; Abraham, Reimar; Sandri, Marco; Reggiani, Carlo; Schiaffino, Stefano

    2008-12-01

    Skeletal muscles of the mdx mouse, a model of Duchenne Muscular Dystrophy, show an excessive reduction in the maximal tetanic force following eccentric contractions. This specific sign of the susceptibility of dystrophin-deficient muscles to mechanical stress can be used as a quantitative test to measure the efficacy of therapeutic interventions. Using inducible transgenesis in mice, we show that when Akt activity is increased the force drop induced by eccentric contractions in mdx mice becomes similar to that of wild-type mice. This effect is not correlated with muscle hypertrophy and is not blocked by rapamycin treatment. The force drop induced by eccentric contractions is similar in skinned muscle fibers from mdx and Akt-mdx mice when stretch is applied directly to skinned fibers. However, skinned fibers isolated from mdx muscles exposed to eccentric contractions in vivo develop less isometric force than wild-type fibers and this force depression is completely prevented by Akt activation. These experiments indicate that the myofibrillar-cytoskeletal system of dystrophin-deficient muscle is highly susceptible to a damage caused by eccentric contraction when elongation is applied in vivo, and this damage can be prevented by Akt activation. Microarray and PCR analyses indicate that Akt activation induces up-regulation of genes coding for proteins associated with Z-disks and costameres, and for proteins with anti-oxidant or chaperone function. The protein levels of utrophin and dysferlin are also increased by Akt activation.

  4. Effect of eccentric contraction on satellite cell activation in human vastus lateralis muscle.

    PubMed

    Imaoka, Yoko; Kawai, Minako; Mori, Futoshi; Miyata, Hirofumi

    2015-09-01

    We compared the time-course of satellite cell (SC) activation between eccentric and concentric contractions in the vastus lateralis (VL) muscle after step exercise. Young adults participated in a 30-min step up/down exercise which mainly involved concentric contractions with the right VL muscle and eccentric contractions with the left VL muscle. The concentric and eccentric contraction phases of the VL muscles were identified by changes in the electromyogram (EMG) and knee joint angle. Biopsy samples were taken from both VL muscles at three time periods: before the exercise and 2 and 5 days after the exercise. We found that the numbers of SCs were significantly increased in the type IIa fibers of the left VL at 2 and 5 days after the exercise. The expression of both hepatocyte growth factor (HGF) and myogenic differentiation 1 (MyoD) mRNA had significantly increased in the left VL at 2 and 5 days after the exercise and in the right VL at 5 days after the exercise. The expression of transient receptor potential canonical (TRPC) 1 mRNA also increased in the left VL at 2 days after exercise. These results indicate that eccentric contraction can effectively activate SC proliferation for up to 5 days after exercise. Similar changes in HGF, MyoD and TRPC1 mRNA expression suggest that HGF/c-Met signal activation through cation influx has a major impact on skeletal muscle SC activation in response to eccentric exercise.

  5. A Case of Pulmonary Paragonimiasis with Involvement of the Abdominal Muscle in a 9-Year-Old Girl

    PubMed Central

    Cho, Ah-Rum; Lee, Hae-Ran; Lee, Kwan-Sub; Lee, Sang-Eun

    2011-01-01

    In Korea, many people enjoy eating raw or underkooked freshwater crayfish and crabs which unfortunately may cause paragonimiasis. Here, we describe a case of pulmonary and abdominal paragonimiasis in a 9-year-old girl, who presented with a 1-month history of abdominal pain, especially in the right flank and the right inguinal area, with anorexia. A chest radiograph revealed pleural effusion in both lungs, and her abdominal sonography indicated an inflammatory lesion in the right psoas muscle. Peripheral blood analysis of the patient showed hypereosinophilia (66.0%) and an elevated total serum IgE level (>2,500 IU/ml). The pleural effusion tested by ELISA were also positive for antibodies against paragonimiasis. Her dietary history stated that she had ingested raw freshwater crab, 4 months previously. The diagnosis was pulmonary paragonimiasis accompanied by abdominal muscle involvement. She was improved after 5 cycles of praziquantel treatment and 2 times of pleural effusion drainage. In conclusion, herein, we report a case of pulmonary and abdominal paragonimiasis in a girl who presented with abdominal pain and tenderness in the inguinal area. PMID:22355209

  6. 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

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

    PubMed

    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.

  8. Effects of contraction path and velocity on the coordination of hand muscles during a three-digit force production task.

    PubMed

    Jiayuan He; Xinjun Sheng; Dingguo Zhang; Xiangyang Zhu

    2014-01-01

    Though many studies indicated that the behavior of single muscle was different between contraction and relaxation, the effect of contraction history profile on multiple muscles has not been investigated. In this study, we analyzed the influence of contraction history on the coordination patterns of hand muscles during a three-digit force production task. The effects of the contraction and relaxation paths with two contraction velocities (5% and 10% maximum voluntary contraction per second) were investigated. The results showed that the force-independent characteristic of muscle coordination patterns still held regardless of the contraction history profiles. In addition, the effect of contraction path was more significant than that of velocity. The study provides a potential way to overcome the impact of contraction disturbance for improving the robustness of the human-machine interface (HMI) based on electromyographic (EMG) pattern recognition.

  9. Pathways of Ca2+ entry and cytoskeletal damage following eccentric contractions in mouse skeletal muscle

    PubMed Central

    Zhang, Bao-Ting; Whitehead, Nicholas P.; Gervasio, Othon L.; Reardon, Trent F.; Vale, Molly; Fatkin, Diane; Dietrich, Alexander; Yeung, Ella W.

    2012-01-01

    Muscles that are stretched during contraction (eccentric contractions) show deficits in force production and a variety of structural changes, including loss of antibody staining of cytoskeletal proteins. Extracellular Ca2+ entry and activation of calpains have been proposed as mechanisms involved in these changes. The present study used isolated mouse extensor digitorum longus (EDL) muscles subjected to 10 eccentric contractions and monitored force production, immunostaining of cytoskeletal proteins, and resting stiffness. Possible pathways for Ca2+ entry were tested with streptomycin (200 μM), a blocker of stretch-activated channels, and with muscles from mice deficient in the transient receptor potential canonical 1 gene (TRPC1 KO), a candidate gene for stretch-activated channels. At 30 min after the eccentric contractions, the isometric force was decreased to 75 ± 3% of initial control and this force loss was reduced by streptomycin but not in the TRPC1 KO. Desmin, titin, and dystrophin all showed patchy loss of immunostaining 30 min after the eccentric contractions, which was substantially reduced by streptomycin and in the TRPC1 KO muscles. Muscles showed a reduction of resting stiffness following eccentric contractions, and this reduction was eliminated by streptomycin and absent in the TRPC1 KO muscles. Calpain activation was determined by the appearance of a lower molecular weight autolysis product and μ-calpain was activated at 30 min, whereas the muscle-specific calpain-3 was not. To test whether the loss of stiffness was caused by titin cleavage, protein gels were used but no significant titin cleavage was detected. These results suggest that Ca2+ entry following eccentric contractions is through a stretch-activated channel that is blocked by streptomycin and encoded or modulated by TRPC1. PMID:22461447

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

    PubMed

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

    2014-08-01

    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.

  11. 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.

  12. [Caerulein-induced contraction of the ileal longitudinal smooth muscle isolated from various animal species].

    PubMed

    Shimizu, K; Horiuchi, T; Tamiya, K; Nakajyo, S

    1983-04-01

    An effect of caerulein was studied on a contractile response of the ileal longitudinal smooth muscle isolated from seven animal species, monkey, dog, rabbit, guinea-pig, rat, vole and mouse. In isotonic recording, caerulein induced a contraction in the muscle isolated from all animal species. Sensitivities of ileal strips to caerulein in the contractile response was divided into three groups. That is, a high sensitive group; dog and guinea-pig, a middle sensitive group; rabbit and vole, a low sensitive group; monkey, rat and mouse. In another series of experiment, effect of several antagonists was examined on the caerulein-induced contraction in ileal muscle of dog, rabbit or guinea-pig. TTX inhibited the contractions in all the ilea. As the contraction was inhibited by atropine and scopolamine in dog ileum but not in rabbit one, the contraction may be due to an excitation of the cholinergic neuron or an excitation of non-cholinergic excitatory neuron, respectively. On the other hand, it is supposed that the contraction in guinea-pig ileum is involved to both the neurons because the contraction was inhibited partially by scopolamine and not by atropine. In conclusion, the ilea isolated from seven animal species showed species differences in sensitivity to caerulein in contractile response, and caerulein seems induces the contractions involving to different nervous systems in dog, rabbit or guinea-pig ileum, respectively.

  13. 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

  14. 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.

  15. Leucine-enriched essential amino acids attenuate muscle soreness and improve muscle protein synthesis after eccentric contractions in rats.

    PubMed

    Kato, Hiroyuki; Suzuki, Hiromi; Mimura, Masako; Inoue, Yoshiko; Sugita, Mayu; Suzuki, Katsuya; Kobayashi, Hisamine

    2015-06-01

    Eccentric exercise results in prolonged muscle weakness and muscle soreness, which are typical symptoms of muscle damage. Recovery from muscle damage is related to mammalian target of rapamycin (mTOR) activity. Leucine-enriched essential amino acids (LEAAs) stimulate muscle protein synthesis via activation of the mTOR pathway. Therefore, we investigated the effect of LEAAs on muscle protein synthesis and muscle soreness after eccentric contractions (EC). Male Sprague-Dawley rats (9-11 weeks old) were administered an LEAA solution (AminoL40; containing 40 % leucine and 60 % other essential amino acids) at 1 g/kg body weight or distilled water (control) 30 min before and 10 min after EC. Tibialis anterior (TA) muscle was exposed to 500 EC by electrical stimulation under anesthesia. The fractional synthesis rate (FSR; %/h) in the TA muscle was measured by incorporating L-[ring-(2)H5] phenylalanine into skeletal muscle protein. Muscle soreness was evaluated by the paw withdrawal threshold using the Randal-Selitto test with some modifications from 1 to 3 days after EC. The FSR in the EC-control group (0.147 ± 0.016 %/h) was significantly lower than in the sedentary group (0.188 ± 0.016 %/h, p < 0.05). AminoL40 administration significantly mitigated the EC-induced impairment of the FSR (0.172 ± 0.018 %/h). EC decreased the paw withdrawal threshold at 1 and 2 days after EC, which indicated that EC induced muscle soreness. Furthermore, AminoL40 administration alleviated the decreased paw withdrawal threshold. These findings suggest that LEAA supplementation improves the rate of muscle protein synthesis and ameliorates muscle soreness after eccentric exercise.

  16. The intracellular pathway of the acetylcholine-induced contraction in cat detrusor muscle cells

    PubMed Central

    An, J Y; Yun, H S; Lee, Y P; Yang, S J; Shim, J O; Jeong, J H; Shin, C Y; Kim, J H; Kim, D S; Sohn, U D

    2002-01-01

    The present study was aimed to investigate intracellular pathways involved in acetylcholine (ACh)-induced contraction in cat detrusor muscle cells Contraction was expressed as per cent shortening of length of individually isolated smooth muscle cells obtained by enzymatic digestion. Dispersed intact and permeabilized cells were prepared for the treatment of drugs and antibody to enzymes, respectively. Using Western blot, we confirmed the presence of related proteins. The maximal contraction to ACh was generated at 10−11 M. This response was preferentially antagonized by M3 muscarinic receptor antagonist ρ-fluoro-hexahydrosiladifenidol (ρF-HSD) but not by the M1 antagonist pirenzepine and the M2 muscarinic receptor antagonist methoctramine. We identified G-proteins Gq/11, Gs, G0, Gi1, Gi2 and Gi3 in the bladder detrusor muscle. ACh-induced contraction was selectively inhibited by Gq/11 antibody but not to other G subunit. The phosphatidylinositol-specific phospholipase C (PI-PLC) inhibitor neomycin reduced ACh-induced contraction. However, the inhibitors of the phospholipase D, the phospholipase A2 and protein kinase C did not attenuate the ACh-induced contraction. ACh-induced contraction was inhibited by antibody to PLC-β1 but not PLC-β3 and PLC-γ. Thapsigargin or strontium, which depletes or blocks intracellular calcium release, inhibited ACh-induced contraction. Inositol 1,4,5-triphosphate (IP3) receptor inhibitor heparin reduced ACh-induced contraction. These results suggest that in cat detrusor muscle contraction induced by ACh is mediated via M3 muscarinic receptor-dependent activation of Gq/11 and PLC-β1 and IP3-dependent Ca2+ release. PMID:12429572

  17. Net calcium fluxes in anterior byssus retractor muscle with phasic and catch contraction.

    PubMed

    Bloomquist, E; Curtis, B A

    1975-11-01

    Calcium in the artificial seawater bathing whole Mytilus anterior byssus retractor muscles (ABRM) was measured by a specific Ca electrode under various conditions of activation, catch, and catch relaxation. Activation in response to ACh was associated with uptake of Ca by the muscles. Phasic contractions produced a small Ca uptake; catch contractions produced a larger and sustained Ca uptake. After tension relaxation, the muscle lost an amount of Ca roughly equal to that gained. Catch relaxation by 5-hydroxytryptamine (5HT) was associated with Ca release. ACh at identical concentrations, applied to the muscle for increasingly longer times, produced increasing amounts of Ca uptake. Regardless of the previous gain of Ca by the muscle, 5HT applied for a constant interval caused release of the same amount of Ca. A model for the Ca control system in ABRM based on this and previously obtained 45Ca efflux data is proposed.

  18. Temporal muscle activation assessment by ultrasound imaging during flexor withdrawal reflex and voluntary contraction.

    PubMed

    Jose, Gomez-Tames; Shuto, Nakamura; Jose, Gonzalez; Wenwei, Yu

    2013-01-01

    Activating flexor reflexes by electrical stimulation has been used as a mechanism to initiate the swing phase or to enhance it for spinal cord injured patients. However, it is necessary to know their contraction dynamics in order to artificially induce them at the right moment of a walking cycle. This requires understanding the temporal activation pattern of both surface and deep muscles simultaneously. This study aimed at developing a system to measure and analyze the temporal activation of both surface and deep muscles during voluntary contraction and flexor reflexes (also called withdrawal reflexes) using ultrasound imaging. A set of experiments were done to verify the validity of the system, while exploring the temporal pattern of muscle activation during flexor reflexes. As a result, we were able to quantify the surface and deep muscle activity by measuring the muscle thickness, pennation angle and long-axis displacement, from the ultrasound images.

  19. 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.

  20. Adaptations to exercise training and contraction-induced muscle injury in animal models of muscular dystrophy.

    PubMed

    Carter, Gregory T; Abresch, R Ted; Fowler, William M

    2002-11-01

    This article reviews the current status of exercise training and contraction-induced muscle-injury investigations in animal models of muscular dystrophy. Most exercise-training studies have compared the adaptations of normal and dystrophic muscles with exercise. Adaptation of diseased muscle to exercise occurs at many levels, starting with the extracellular matrix, but also involves cytoskeletal architecture, muscle contractility, repair mechanisms, and gene regulation. The majority of exercise-injury investigations have attempted to determine the susceptibility of dystrophin-deficient muscles to contraction-induced injury. There is some evidence in animal models that diseased muscle can adapt and respond to mechanical stress. However, exercise-injury studies show that dystrophic muscles have an increased susceptibility to high mechanical forces. Most of the studies involving exercise training have shown that muscle adaptations in dystrophic animals were qualitatively similar to the adaptations observed in control muscle. Deleterious effects of the dystrophy usually occur only in older animals with advanced muscle fiber degeneration or after high-resistive eccentric training. The main limitations in applying these conclusions to humans are the differences in phenotypic expression between humans and genetically homologous animal models and in the significant biomechanical differences between humans and these animal models.

  1. Muscle Fatigue Affects the Interpolated Twitch Technique When Assessed Using Electrically-Induced Contractions in Human and Rat Muscles

    PubMed Central

    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. PMID:27445844

  2. 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.

  3. Muscle activity and co-contraction of musculoskeletal model during steering maneuver.

    PubMed

    Gao, Zhen-hai; Fan, Da; Wang, Deping; Zhao, Hui; Zhao, Kaishu; Chen, Chaoyang

    2014-01-01

    In this study a musculoskeletal model of driver steering maneuver was established. The model was driven by the steering angle and steering torque when performing typical steering test. The simulation was calculated using inverse dynamics. Maximum muscle activity and the muscle activity of each muscle were studied afterwards. The key muscles that generated steering torque were scapular portion of deltoid, infraspinatus, latissimus dorsi, subscapularis, triceps long head and triceps lateral head. Muscle co-contraction was analyzed quantitatively and was significantly different from muscle activity. This paper presents a preliminary research on the mechanical properties of upper limb muscles during steering maneuver. The results can serve as references for vehicle design and performance evaluation using the physiological characteristics of drivers.

  4. 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

  5. Mechanisms underlying stabilization of temporally summated muscle contractions in the lobster (Panulirus) pyloric system.

    PubMed

    Morris, L G; Hooper, S L

    2001-01-01

    Muscles are the final effectors of behavior. The neural basis of behavior therefore cannot be completely understood without a description of the transfer function between neural output and muscle contraction. To this end, we have been studying muscle contraction in the well-investigated lobster pyloric system. We report here the mechanisms underlying stabilization of temporally summating contractions of the very slow dorsal dilator muscle in response to motor nerve stimulation with trains of rhythmic shock bursts at a physiological intraburst spike frequency (60 Hz), physiological cycle periods (0.5-2 s), and duty cycles from 0.1 to 0.8. For temporal summation to stabilize, the rise and relaxation amplitudes of the phasic contractions each burst induces must equalize as the rhythmic train continues. Stabilization could occur by changes in rise duration, rise slope, plateau duration, and/or relaxation slope. We demonstrate a generally applicable method for quantifying the relative contribution changes in these characteristics make to contraction stabilization. Our data show that all characteristics change as contractions stabilize, but their relative contribution differs depending on stimulation cycle period and duty cycle. The contribution of changes in rise duration did not depend on period or duty cycle for the 1-, 1.5-, and 2-s period regimes, contributing approximately 30% in all cases; but for the 0.5-s period regime, changes in rise duration increased from contributing 25% to contributing 50% as duty cycle increased from 0.1 to 0.8. At all cycle periods decreases in rise slope contributed little to stabilization at small duty cycles but increased to contributing approximately 80% at high duty cycles. The contribution of changes in plateau duration decreased in all cases as duty cycle increased; but this decrease was greater in long cycle period regimes. The contribution of changes in relaxation slope also decreased in all cases as duty cycle increased; but

  6. Effect of eccentric contraction velocity on muscle damage in repeated bouts of elbow flexor exercise.

    PubMed

    Barroso, Renato; Roschel, Hamilton; Ugrinowitsch, Carlos; Araújo, Rubens; Nosaka, Kazunori; Tricoli, Valmor

    2010-08-01

    Eccentric exercise induces muscle damage, but controversy exists concerning the effect of contraction velocity on the magnitude of muscle damage, and little is known about the effect of contraction velocity on the repeated-bout effect. This study examined slow (60 degrees.s(-1)) and fast (180 degrees.s(-1)) velocity eccentric exercises for changes in indirect markers of muscle damage following 3 exercise bouts that were performed every 2 weeks. Fifteen young men were divided into 2 groups based on the velocity of eccentric exercise: 7 in the Ecc60 (60 degrees.s(-1)) group, and 8 in the Ecc180 (180 degrees.s(-1)) group. The exercise consisted of 30 maximal eccentric contractions of the elbow flexors at each velocity, in which the elbow joint was forcibly extended from 60 degrees to 180 degrees (full extension) on an isokinetic dynamometer. Changes in maximal voluntary isometric contraction strength, range of motion, muscle soreness, and plasma creatine kinase activity before and for 4 days after the exercise were compared in the 2 groups using a mixed-model analysis (groupxboutxtime). No significant differences between groups were evident for changes in any variables following exercise bouts; however, the changes were significantly smaller (p<0.05) after the second and third bouts than after the first bout. These results indicate that the contraction velocity does not influence muscle damage or the repeated-bout effect.

  7. Synthesis of Facial Image with Expression Based on Muscular Contraction Parameters Using Linear Muscle and Sphincter Muscle

    NASA Astrophysics Data System (ADS)

    Ahn, Seonju; Ozawa, Shinji

    We aim to synthesize individual facial image with expression based on muscular contraction parameters. We have proposed a method of calculating the muscular contraction parameters from arbitrary face image without using learning for each individual. As a result, we could generate not only individual facial expression, but also the facial expressions of various persons. In this paper, we propose the muscle-based facial model; the facial muscles define both the linear and the novel sphincter. Additionally, we propose a method of synthesizing individual facial image with expression based on muscular contraction parameters. First, the individual facial model with expression is generated by fitting using the arbitrary face image. Next, the muscular contraction parameters are calculated that correspond to the expression displacement of the input face image. Finally, the facial expression is synthesized by the vertex displacements of a neutral facial model based on calculated muscular contraction parameters. Experimental results reveal that the novel sphincter muscle can synthesize facial expressions of the facial image, which corresponds to the actual face image with arbitrary and mouth or eyes expression.

  8. MYOPOTENTIAL RESPONSE AND THE FORCE OF MUSCLE CONTRACTION.

    DTIC Science & Technology

    of the study included the effect of five different loads on six muscle sites in both elbow and shoulder flexion. The data were rendered into tables and into position-torque charts called isomyols. (Author)

  9. Effects of muscle contraction on the load-strain properties of frog aponeurosis and tendon.

    PubMed

    Lieber, R L; Leonard, M E; Brown-Maupin, C G

    2000-01-01

    The mechanical properties of the frog semitendinosus (ST) tendon and aponeurosis were measured during passive tensile loading to a force equal to ST maximum tetanic tension and during active isometric muscle contraction. During active contraction, both the tendon and aponeurosis regions initially strained at rates exceeding 400%/s while near the end of the muscle contraction, strain rates were nearly zero. At this point, the strain in the tendon region was equal to that observed during slow passive loading to the same tension level. However, for the aponeurosis, even near the zero strain rate, strain at the end of the active contraction was significantly below that observed during slow passive loading (p < 0. 001). Specifically, when aponeurosis strain rate was almost zero, aponeurosis strain was 13.8 +/- 3% (means +/- SEM, n = 10), which was significantly below that measured during passive loading (23.7 +/- 5%) suggesting that active contraction actually altered aponeurosis material properties. These data demonstrate that, while the tendon and aponeurosis regions have different passive biomechanical properties and both demonstrate viscosity typical of other connective tissues, the aponeurosis region of the frog ST actually changed its intrinsic properties during muscle contraction. Thus, extrapolation of biomechanical data obtained at nonphysiological strain rates or under conditions where the muscle-tendon junction has been interrupted should be made with caution.

  10. 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.

  11. 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.

  12. Further observations on the facilitation of muscle responses to cortical stimulation by voluntary contraction.

    PubMed

    Thompson, P D; Day, B L; Rothwell, J C; Dressler, D; Maertens de Noordhout, A; Marsden, C D

    1991-10-01

    The effect of voluntary contraction on the discharge of single motor units following electrical and magnetic stimulation of the motor cortex was examined using the post-stimulus time histogram (PSTH) technique. The latencies of responses in single motor units of the first dorsal interosseous muscle to cortical stimulation were 2-4 msec shorter when the muscle was contracting than when at rest in 9 of 10 units studied. These latency differences are comparable with those recorded by surface electromyography for compound muscle action potentials following cortical stimulation in relaxed and active muscles. The new findings are that the intensity of cortical stimulation required to discharge a resting motor unit to produce a single PSTH peak produced multiple PSTH peaks when the same unit was contracting. The timing of the PSTH peak of relaxed motor unit discharge corresponded to one of the later PSTH peaks (usually the second) when the motor unit was voluntarily activated. These findings are in keeping with our previous suggestions that the longer latency of responses in relaxed muscles is due to the time taken for temporal summation of multiple descending corticospinal volleys at the cortico-motoneurone synapse. Facilitation produced by voluntary contraction occurs at least in part at the level of the spinal cord by lowering motoneurone threshold to enable discharge on the initial descending volley. The higher threshold of relaxed muscles is related to the higher intensities of stimulation needed to recruit multiple descending volleys and discharge resting motoneurones.

  13. Muscle damage after low-intensity eccentric contractions with blood flow restriction.

    PubMed

    Thiebaud, R S; Loenneke, J P; Fahs, C A; Kim, D; Ye, X; Abe, T; Nosaka, K; Bemben, M G

    2014-06-01

    Discrepancies exist whether blood flow restriction (BFR) exacerbates exercise-induced muscle damage (EIMD). This study compared low-intensity eccentric contractions of the elbow flexors with and without BFR for changes in indirect markers of muscle damage. Nine untrained young men (18-26 y) performed low-intensity (30% 1RM) eccentric contractions (2-s) of the elbow flexors with one arm assigned to BFR and the other arm without BFR. EIMD markers of maximum voluntary isometric contraction (MVC) torque, range of motion (ROM), upper arm circumference, muscle thickness and muscle soreness were measured before, immediately after, 1, 2, 3, and 4 days after exercise. Electromyography (EMG) amplitude of the biceps brachii and brachioradialis were recorded during exercise. EMG amplitude was not significantly different between arms and did not significantly change from set 1 to set 4 for the biceps brachii but increased for the brachioradialis (p ≤ 0.05, 12.0% to 14.5%) when the conditions were combined. No significant differences in the changes in any variables were found between arms. MVC torque decreased 7% immediately post-exercise (p ≤ 0.05), but no significant changes in ROM, circumference, muscle thickness and muscle soreness were found. These results show that BFR does not affect EIMD by low-intensity eccentric contractions.

  14. Identification and Validation of Novel Contraction-Regulated Myokines Released from Primary Human Skeletal Muscle Cells

    PubMed Central

    Raschke, Silja; Eckardt, Kristin; Bjørklund Holven, Kirsten; Jensen, Jørgen; Eckel, Jürgen

    2013-01-01

    Proteins secreted by skeletal muscle, so called myokines, have been shown to affect muscle physiology and additionally exert systemic effects on other tissues and organs. Although recent profiling studies have identified numerous myokines, the amount of overlap from these studies indicates that the secretome of skeletal muscle is still incompletely characterized. One limitation of the models used is the lack of contraction, a central characteristic of muscle cells. Here we aimed to characterize the secretome of primary human myotubes by cytokine antibody arrays and to identify myokines regulated by contraction, which was induced by electrical pulse stimulation (EPS). In this study, we validated the regulation and release of two selected myokines, namely pigment epithelium derived factor (PEDF) and dipeptidyl peptidase 4 (DPP4), which were recently described as adipokines. This study reveals that both factors, DPP4 and PEDF, are secreted by primary human myotubes. PEDF is a contraction-regulated myokine, although PEDF serum levels from healthy young men decrease after 60 min cycling at VO2max of 70%. Most interestingly, we identified 52 novel myokines which have not been described before to be secreted by skeletal muscle cells. For 48 myokines we show that their release is regulated by contractile activity. This profiling study of the human skeletal muscle secretome expands the number of myokines, identifies novel contraction-regulated myokines and underlines the overlap between proteins which are adipokines as well as myokines. PMID:23637948

  15. 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.

  16. 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

  17. 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.

  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. 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.

  20. Evidence for a common mechanism for spontaneous rhythmic contraction and myogenic contraction induced by quick stretch in detrusor smooth muscle

    PubMed Central

    Komari, S Omid; Headley, Patrick C; Klausner, Adam P; Ratz, Paul H; Speich, John E

    2013-01-01

    Detrusor smooth muscle exhibits myogenic contraction in response to a quick stretch (QS) as well as spontaneous rhythmic contraction (SRC); however, whether the same population of actomyosin crossbridges with a common regulatory mechanism is responsible for these two types of contraction has not been determined. Detrusor strips from New Zealand white rabbit bladders were allowed to develop SRC at a reference muscle length (Lref), or rhythmic contraction (RC) was induced with tetraethylammonium (TEA). Multiple 10-msec stretches of 15% Lref were then imposed at Lref randomly during the rhythm cycle, and the nadir-to-peak (NTP) tension amplitude of the resulting myogenic contraction was measured. The amplitude and period of the rhythm cycle were measured prior to each QS. NTP was larger when a QS was imposed during a portion the cycle when tension was smaller (n = 3 each SRC and TEA-induced RC). These data suggest that when the rhythmic mechanism was mostly inactive and tension was near a minimum, a larger portion of a shared population of crossbridges was available to produce a myogenic response to a QS. Rho kinase, cyclooxygenase-1, and cyclooxygenase-2 inhibitors (H-1152, SC-560, and NS-398) affected SRC amplitude and NTP amplitude following a QS to the same degree (n = 3 each drug), providing additional evidence to support the hypothesis that a common mechanism is responsible for SRC and myogenic contraction due to QS. If a common mechanism exists, then QS is a potential mechanical probe to study SRC regulation and its alteration in overactive bladder. PMID:24400167

  1. 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.

  2. Hsp25 and Hsp72 content in rat skeletal muscle following controlled shortening and lengthening contractions.

    PubMed

    Holwerda, Andrew M; Locke, Marius

    2014-12-01

    The cytoprotective proteins, Hsp25 and Hsp72, are increased in skeletal muscle after nondamaging, shortening contractions, but the temporal pattern of expression and stimulatory mechanisms remain unclear. Thus, we sought to define the in vivo temporal patterns of expression for Hsp25 and Hsp72 after 2 opposing contractions types. To do this, male Sprague-Dawley rats had 1 tibialis anterior (TA) muscle electrically stimulated (5 sets of 20 repetitions) while being either forcibly lengthened (LC) or shortened (SC). At 2, 8, 24, 48, 72, or 168 h after the contractions both the stimulated and the nonstimulated (contra-lateral control) TA muscles were removed and processed to examine muscle damage (hemotoxylin and eosin staining) and Hsp content (Western blot analyses). Cross-sections from TA muscles subjected to LCs showed muscle fibre damage at 8 h and thereafter. In contrast, no muscle fibre damage was observed at any time point following SCs. When normalized to contra-lateral controls, Hsp25 and Hsp72 content were significantly (P < 0.01) increased at 24 h (3.1- and 3.8-fold, respectively) and thereafter. There were no significant increases in Hsp25 or Hsp72 content at any time point following SC. These data suggest that LCs, but not SCs, result in Hsp accumulation and that the fibre/cellular damage sustained from LCs may be the stimulus for elevating Hsp content.

  3. 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.

  4. Active finite element analysis of skeletal muscle-tendon complex during isometric, shortening and lengthening contraction.

    PubMed

    Tsui, C P; Tang, C Y; Leung, C P; Cheng, K W; Ng, Y F; Chow, D H K; Li, C K

    2004-01-01

    An active finite element model was developed to predict the mechanical behaviors of skeletal muscle-tendon complex during isometric, shortening and lengthening contraction. The active finite element was created through incorporation of a user-defined material property into ABAQUS finite element code. The active finite element is controlled by a motor element that is activated by a mathematical function. The nonlinear passive behavior of the muscle was defined by the viscoelastic elements and can be easily altered to other properties by using other elements in the material library without the need of re-defining the constitutive relation of the muscle. The isometric force-length relationship, force-strain relations of the muscle-tendon complex during both shortening and lengthening contraction and muscle relaxation response were predicted using the proposed finite element model. The predicted results were found to be in good agreement with available experimental data. In addition, the stress distribution in the muscle-tendon complex during isometric, shortening and lengthening contractions was simulated. The location of the maximum stress may provide useful information for studying muscle damage and fatigue in the future.

  5. 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

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

    PubMed

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

    2008-08-01

    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.

  7. Effects of dietary carbohydrate on delayed onset muscle soreness and reactive oxygen species after contraction induced muscle damage

    PubMed Central

    Close, G; Ashton, T; Cable, T; Doran, D; Noyes, C; McArdle, F; MacLaren, D

    2005-01-01

    Background: Delayed onset muscle soreness (DOMS) occurs after unaccustomed exercise and has been suggested to be attributable to reactive oxygen species (ROS). Previous studies have shown increased ROS after lengthening contractions, attributable to invading phagocytes. Plasma glucose is a vital fuel for phagocytes, therefore carbohydrate (CHO) status before exercise may influence ROS production and DOMS Objective: To examine the effect of pre-exercise CHO status on DOMS, ROS production, and muscle function after contraction induced muscle damage. Method: Twelve subjects performed two downhill runs, one after a high CHO diet and one after a low CHO diet. Blood samples were drawn for analysis of malondialdehyde, total glutathione, creatine kinase, non-esterified fatty acids, lactate, glucose, and leucocytes. DOMS and muscle function were assessed daily. Results: The high CHO diet resulted in higher respiratory exchange ratio and lactate concentrations than the low CHO diet before exercise. The low CHO diet resulted in higher non-esterified fatty acid concentrations before exercise. DOMS developed after exercise and remained for up to 96 hours, after both diets. A biphasic response in creatine kinase occurred after both diets at 24 and 96 hours after exercise. Malondialdehyde had increased 72 hours after exercise after both diets, and muscle function was attenuated up to this time. Conclusions: Downhill running resulted in increased ROS production and ratings of DOMS and secondary increases in muscle damage. CHO status before exercise had no effect. PMID:16306505

  8. Temperature-dependent transitions in isometric contractions of rat muscle.

    PubMed Central

    Ranatunga, K W; Wylie, S R

    1983-01-01

    The effect of temperature on tetanic tension development was examined in extensor digitorum longus (fast-twitch) and soleus (slow-twitch) muscles of the rat, in vitro and with direct stimulation. The temperature range was from 35 to 10 degrees C. 2. The maximum tetanic tension decreased slightly on cooling from 35 to 25 degrees C. Cooling below 20 degrees C resulted in a marked depression of tetanic tension. The results were similar in the two muscles. 3. Analysis (in the form of Arrhenius plots) of the rate of tetanic tension development and relaxation clearly showed the occurrence of two phases in their temperature dependence, due to an increased temperature sensitivity below about 25 degrees C. Arrhenius activation energy estimates for temperatures lower than 21 degrees C were around twice as high as those for temperatures higher than 24 degrees C in both muscles. PMID:6887040

  9. Two maximal isometric contractions attenuate the magnitude of eccentric exercise-induced muscle damage.

    PubMed

    Chen, Hsin-Lian; Nosaka, Kazunori; Pearce, Alan J; Chen, Trevor C

    2012-08-01

    This study investigated whether maximal voluntary isometric contractions (MVC-ISO) would attenuate the magnitude of eccentric exercise-induced muscle damage. Young untrained men were placed into one of the two experimental groups or one control group (n = 13 per group). Subjects in the experimental groups performed either two or 10 MVC-ISO of the elbow flexors at a long muscle length (20° flexion) 2 days prior to 30 maximal isokinetic eccentric contractions of the elbow flexors. Subjects in the control group performed the eccentric contractions without MVC-ISO. No significant changes in maximal voluntary concentric contraction peak torque, peak torque angle, range of motion, upper arm circumference, plasma creatine kinase (CK) activity and myoglobin concentration, muscle soreness, and ultrasound echo intensity were evident after MVC-ISO. Changes in the variables following eccentric contractions were smaller (P < 0.05) for the 2 MVC-ISO group (e.g., peak torque loss at 5 days after exercise, 23% ± 3%; peak CK activity, 1964 ± 452 IU·L(-1); peak muscle soreness, 46 ± 4 mm) or the 10 MVC-ISO group (13% ± 3%, 877 ± 198 IU·L(-1), 30 ± 4 mm) compared with the control (34% ± 4%, 6192 ± 1747 IU·L(-1), 66 ± 5 mm). The 10 MVC-ISO group showed smaller (P < 0.05) changes in all variables following eccentric contractions compared with the 2 MVC-ISO group. Therefore, two MVC-ISO conferred potent protective effects against muscle damage, whereas greater protective effect was induced by 10 MVC-ISO, which can be used as a strategy to minimize muscle damage.

  10. 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.

  11. 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.

  12. Multiple causes of fatigue during shortening contractions in rat slow twitch skeletal muscle.

    PubMed

    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. Causes of excitation-induced muscle cell damage in isometric contractions: mechanical stress or calcium overload?

    PubMed

    Fredsted, Anne; Gissel, Hanne; Madsen, Klavs; Clausen, Torben

    2007-06-01

    Prolonged or unaccustomed exercise leads to muscle cell membrane damage, detectable as release of the intracellular enzyme lactic acid dehydrogenase (LDH). This is correlated to excitation-induced influx of Ca2+, but it cannot be excluded that mechanical stress contributes to the damage. We here explore this question using N-benzyl-p-toluene sulfonamide (BTS), which specifically blocks muscle contraction. Extensor digitorum longus muscles were prepared from 4-wk-old rats and mounted on holders for isometric contractions. Muscles were stimulated intermittently at 40 Hz for 15-60 min or exposed to the Ca2+ ionophore A23187. Electrical stimulation increased 45Ca influx 3-5 fold. This was followed by a progressive release of LDH, which was correlated to the influx of Ca2+. BTS (50 microM) caused a 90% inhibition of contractile force but had no effect on the excitation-induced 45Ca influx. After stimulation, ATP and creatine phosphate levels were higher in BTS-treated muscles, most likely due to the cessation of ATP-utilization for cross-bridge cycling, indicating a better energy status of these muscles. No release of LDH was observed in BTS-treated muscles. However, when exposed to anoxia, electrical stimulation caused a marked increase in LDH release that was not suppressed by BTS but associated with a decrease in the content of ATP. Dynamic passive stretching caused no increase in muscle Ca2+ content and only a minor release of LDH, whereas treatment with A23187 markedly increased LDH release both in control and BTS-treated muscles. In conclusion, after isometric contractions, muscle cell membrane damage depends on Ca2+ influx and energy status and not on mechanical stress.

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

    PubMed Central

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

    2016-01-01

    Objective This study investigates the impact of isometric contraction of anterior cervical muscles on cervical lordosis. Methods 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. Results 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). Conclusion 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. PMID:27761195

  15. Effects of physiological and toxic metals on the contraction of glycerinated rabbit psoas muscle

    SciTech Connect

    Both, A.B.; Wofford, H.W.

    1995-07-01

    The effects of three physiological metals (Fe, Zn, and Cu) and three toxic metals (Pb, Cd, and Hg) on the contraction of glycerinated psoas muscle of rabbit were examined. Four different dilutions of each metal solution were added to glycerinated psoas muscle fibers of rabbit. A solution containing 0.25 % ATP plus 0.05 M KCl plus 0.001 M M{sub g}Cl{sub 2} was applied. The lengths of the muscle fibers before and after the addition of the ATP and salt solution were measured. All six metals inhibited muscle contraction in a dose-dependent manner, regardless of whether they were considered physiological or toxic. A possible explanation for the results involving a metal-ATP complex is given.

  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

    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.

  17. 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.

  18. A 2 week routine stretching programme did not prevent contraction-induced injury in mouse muscle.

    PubMed

    Black, Jonathon D J; Freeman, Marcus; Stevens, E Don

    2002-10-01

    Most athletes stretch as part of their training regimen and it is commonly believed that this practice prevents muscle injury. We tested this belief using an animal model, in situ mouse extensor digitorum longus (EDL) muscle. One lower hindlimb was slowly stretched for 1 min on alternate days for 12 days; the other leg served as a control. The mouse was lightly anaesthetized during the stretching protocol (isofluorane). Both legs were tested in situ by measuring maximum isometric force and maximum work before and after an eccentric contraction that was designed to cause a contraction-induced injury. The difference between a contraction before and after (i.e. the deficit) was used as a measure of damage caused by the eccentric contraction. There was a threshold for force deficit at a peak to peak eccentric excursion amplitude of 19.5 % (i.e. L(o) +/- 9.75 %, where L(o) is muscle length at peak isometric force). There was a significant increase in force deficit, work deficit, and curve shift with an increase in eccentric excursion amplitude above the threshold. There was no statistical difference in the force deficit, work deficit, or curve shift between the stretched leg and the control leg (P > 0.05). A routine stretching programme, at least at the intensities employed in this experiment, did not prevent contraction-induced injury in the in situ mouse EDL muscle.

  19. Inhibition of tracheal smooth muscle contraction and myosin phosphorylation by ryanodine

    SciTech Connect

    Gerthoffer, W.T.; Murphey, K.A.; Khoyi, M.A.

    1988-08-01

    Previous studies have shown that muscarinic activation of airway smooth muscle in low Ca++ solutions increases myosin phosphorylation without increasing tension. Blocking Ca++ influx reduced phosphorylation, but not to basal levels. It was proposed that release of intracellular Ca++ contributed to dissociation of phosphorylation and contraction. To test this hypothesis the effects of ryanodine were studied under similar conditions. Ryanodine (10(-7) to 10(-5) M) antagonized caffeine-induced contraction of canine tracheal smooth muscle. Ryanodine also reduced carbachol-induced contractions and carbachol-induced myosin phosphorylation. The effect of ryanodine on potassium and serotonin-induced contractions was also investigated to test for a nonspecific inhibitory effect. In contrast to the effect on carbachol responses, ryanodine (10(-5) M) potentiated the contractile response to low concentrations of serotonin and potassium, but had no effect on the maximum response to either stimulant. Carbachol (10(-6) M) and ryanodine (10(-5) M) both significantly decreased /sup 45/Ca++ content of tracheal muscle. The effect of ryanodine and carbachol together on /sup 45/Ca++ content was not greater than either drug alone suggesting that ryanodine reduces the caffeine and carbachol responses by depleting releaseable Ca++ stores. Ryanodine significantly reduced Ca++-induced contraction and myosin phosphorylation in carbachol-stimulated muscle, suggesting that some of the Ca++ responsible for elevated phosphorylation is released from the sarcoplasmic reticulum.

  20. 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.

  1. Role of Ca2+, membrane excitability, and Ca2+ stores in failing muscle contraction with aging.

    PubMed

    Payne, Anthony Michael; Jimenez-Moreno, Ramón; Wang, Zhong-Ming; Messi, María Laura; Delbono, Osvaldo

    2009-04-01

    Excitation-contraction (EC) coupling in a population of skeletal muscle fibers of aged mice becomes dependent on the presence of external Ca(2+) ions (Payne, A.M., Zheng, Z., Gonzalez, E., Wang, Z.M., Messi, M.L., Delbono, O., 2004b. External Ca(2+)-dependent excitation - contraction coupling in a population of aging mouse skeletal muscle fibers. J. Physiol. 560, 137-155.). However, the mechanism(s) underlying this process remain unknown. In this work, we examined the role of (1) extracellular Ca(2+); (2) voltage-induced influx of external Ca(2+) ions; (3) sarcoplasmic reticulum (SR) Ca(2+) depletion during repeated contractions; (4) store-operated Ca(2+) entry (SOCE); (5) SR ultrastructure; (6) SR subdomain localization of the ryanodine receptor; and (7) sarcolemmal excitability in muscle force decline with aging. These experiments show that external Ca(2+), but not Ca(2+) influx, is needed to maintain force upon repetitive fiber electrical stimulation. Decline in fiber force is associated with depressed SR Ca(2+) release. SR Ca(2+) depletion, SOCE, and the putative segregated Ca(2+) release store do not play a significant role in external Ca(2+)-dependent contraction. More importantly, a significant number of action potentials fail in senescent mouse muscle fibers subjected to a stimulation frequency. These results indicate that failure to generate action potentials accounts for decreased intracellular Ca(2+) mobilization and tetanic force in aging muscle exposed to a Ca(2+)-free medium.

  2. Modeling force-velocity relation in skeletal muscle isotonic contraction using an artificial neural network.

    PubMed

    Dariani, Sharareh; Keshavarz, Mansoor; Parviz, Mohsen; Raoufy, Mohammad Reza; Gharibzadeh, Shahriar

    2007-01-01

    The aim of this study is to design an artificial neural network (ANN) to model force-velocity relation in skeletal muscle isotonic contraction. We obtained the data set, including physiological and morphometric parameters, by myography and morphometric measurements on frog gastrocnemius muscle. Then, we designed a multilayer perceptron ANN, the inputs of which are muscle volume, muscle optimum length, tendon length, preload, and afterload. The output of the ANN is contraction velocity. The experimental data were divided randomly into two parts. The first part was used to train the ANN. In order to validate the model, the second part of experimental data, which was not used in training, was employed to the ANN and then, its output was compared with Hill model and the experimental data. The behavior of ANN in high forces was more similar to experimental data, but in low forces the Hill model had better results. Furthermore, extrapolation of ANN performance showed that our model is more or less able to simulate eccentric contraction. Our results indicate that ANNs represent a powerful tool to capture some essential features of muscle isotonic contraction.

  3. 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.

  4. 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.

  5. The Effects of Horse Riding Simulation Training on Stroke Patients’ Balance Ability and Abdominal Muscle Thickness Changes

    PubMed Central

    Baek, Il-Hun; Kim, Byeong Jo

    2014-01-01

    [Purpose] The purpose of this study was to assess the effects of horse riding simulation training on changes in balance ability and abdominal muscle thicknesses of stroke patients. [Subjects] Thirty stroke patients with hemiplegia were recruited, and they were randomly assigned to a control or experimental group. [Methods] The experimental group performed horse riding simulation training, whereas the control group performed trunk exercises for 8 weeks. Balance ability was measured using a BioRescue system. The thicknesses of subjects’ external oblique, internal oblique, and transversus abdominis muscles were measured by ultrasonic imaging. [Results] In the experimental group, balance ability was significantly improved after training. Similarly, the thickness of the abdominal muscles on the affected side changed after training in the experimental group, whereas the control group showed no statistically significant changes. [Conclusion] We suggest that horse riding simulation training is more effective than trunk exercises at reducing the center of pressure path length and travel speed and improving the asymmetry of the abdominal muscles of stroke patients. PMID:25202200

  6. Contribution of abdominal muscle strength to various activities of daily living of stroke patients with mild paralysis.

    PubMed

    Fujita, Takaaki; Sato, Atsushi; Togashi, Yui; Kasahara, Ryuichi; Ohashi, Takuro; Yamamoto, Yuichi

    2015-03-01

    [Purpose] The trunk muscles frequently become weak after stroke, thus impacting overall activities of daily living. However, activities of daily living items closely related with trunk strength remain unclear. This study aimed to clarify the influence of trunk muscle weakness on activities of daily living items. [Subjects] The subjects were 24 stroke patients who fulfilled the following inclusion criteria: first stroke and the absence of severe paralysis, marked cognitive function deterioration, unilateral spatial neglect or apathy. [Methods] According to abdominal strength, the 24 patients were divided into a nonweakness group and a weakness group. For the assessment, we used the stroke impairment assessment set, the Berg balance scale, a simple test for evaluating hand function, grip strength, and functional independence measure scale scores and the results were compared between the groups. [Results] The Berg balance scale score and scores for dressing, toilet use, transfer to bed, and walk items of the functional independence measure were significantly lower in the weakness group than in the nonweakness group. [Conclusion] Our results suggest that weakness of the abdominal muscles adversely impacts the balance of patients with mild stroke as well as their ability to dress, use a toilet, transfer, and walk. Trunk training, including abdominal muscle exercises, can effectively improve the performance of these activities of daily living items.

  7. Induction of Muscle Hypertrophy in Rats through Low Intensity Eccentric Contraction.

    PubMed

    Tsumiyama, Wakako; Oki, Sadaaki; Takamiya, Naomi; Umei, Namiko; Shimizu, Michele Eisemann; Ono, Takeya; Otsuka, Akira

    2014-10-01

    [Purpose] The purpose of this study was to examine whether a low intensity exercise using an eccentric contraction would result in skeletal muscle hypertrophy in rats. [Subjects and Methods] Eighteen female Wistar rats were used in this study. The rats were randomly divided into three groups. The control group performed no exercise. The level group ran on a treadmill on a 0° incline. The downhill group ran on a treadmill on a -16° incline. The two exercise groups ran on a treadmill at 16 m/min for 90 minutes, once every three days for a total of twenty sessions. [Results] The muscle wet weights, the relative weight ratios, and the muscle fiber cross-section minor axes of the downhill group were significantly larger than those of the control and level groups. There were no differences in the muscle wet weights, the relative weight ratios, and the muscle fiber cross-section minor axes between the control group and the level group. [Conclusion] The stimulation from the low intensity eccentric contraction may have produced enough mechanical stress to induce muscle hypertrophy without the over-stressing that might have produced muscle fiber damage. These results indicate that this technique may be an effective method of inducing hypertrophy in skeletal muscle.

  8. Heat production and metabolism during the contraction of mammalian skeletal muscle.

    PubMed

    Kretzschmar, K M

    1975-01-01

    Methods are described whereby initial processes of muscular contraction may be investigated in a mammalian preparation, the soleus muscle of the rat. Conditions are chosen so that recovery is avoided. An isometric tetanus is investigated and an energy balance sheet is drawn up. It is found that there is more heat evolved than can be accounted for in terms of measured chemical reaction. This discrepancy is discussed with reference to the similar results that have been obtained using frog muscle.

  9. Effects of nitrate supplementation via beetroot juice on contracting rat skeletal muscle microvascular oxygen pressure dynamics.

    PubMed

    Ferguson, Scott K; Hirai, Daniel M; Copp, Steven W; Holdsworth, Clark T; Allen, Jason D; Jones, Andrew M; Musch, Timothy I; Poole, David C

    2013-07-01

    NO3(-) supplementation via beetroot juice (BR) augments exercising skeletal muscle blood flow subsequent to its reduction to NO2(-) then NO. We tested the hypothesis that enhanced vascular control following BR would elevate the skeletal muscle O2 delivery/O2 utilization ratio (microvascular PO2, PmvO2) and raise the PmvO2 during the rest-contractions transition. Rats were administered BR (~0.8 mmol/kg/day, n=10) or water (control, n=10) for 5 days. PmvO2 was measured during 180 s of electrically induced (1 Hz) twitch spinotrapezius muscle contractions. There were no changes in resting or contracting steady-state PmvO2. However, BR slowed the PmvO2 fall following contractions onset such that time to reach 63% of the initial PmvO2 fall increased (MRT1; control: 16.8±1.9, BR: 24.4±2.7 s, p<0.05) and there was a slower relative rate of PmvO2 fall (Δ1PmvO2/τ1; control: 1.9±0.3, BR: 1.2±0.2 mmHg/s, p<0.05). Despite no significant changes in contracting steady state PmvO2, BR supplementation elevated the O2 driving pressure during the crucial rest-contractions transients thereby providing a potential mechanism by which BR supplementation may improve metabolic control.

  10. Reduced activation in isometric muscle action after lengthening contractions is not accompanied by reduced performance fatigability

    PubMed Central

    Seiberl, W.; Hahn, D.; Paternoster, F. K.

    2016-01-01

    After active lengthening contractions, a given amount of force can be maintained with less muscle activation compared to pure isometric contractions at the same muscle length and intensity. This increase in neuromuscular efficiency is associated with mechanisms of stretch-induced residual force enhancement. We hypothesized that stretch-related increase in neuromuscular efficiency reduces fatigability of a muscle during submaximal contractions. 13 subjects performed 60 s isometric knee extensions at 60% of maximum voluntary contraction (MVC) with and without prior stretch (60°/s, 20°). Each 60 s trial was preceded and followed by neuromuscular tests consisting of MVCs, voluntary activation (VA) and resting twitches (RT), and there was 4 h rest between sets. We found a significant (p = 0.036) 10% reduction of quadriceps net-EMG after lengthening compared to pure isometric trials. However, increase in neuromuscular efficiency did not influence the development of fatigue. Albeit we found severe reduction of MVC (30%), RT (30%) and VA (5%) after fatiguing trials, there were no differences between conditions with and without lengthening. As the number of subjects showing no activation reduction increased with increasing contraction time, intensity may have been too strenuous in both types of contractions, such that a distinction between different states of fatigue was not possible anymore. PMID:27966620

  11. Proprioceptive acuity predicts muscle co-contraction of the tibialis anterior and gastrocnemius medialis in older adults' dynamic postural control.

    PubMed

    Craig, C E; Goble, D J; Doumas, M

    2016-05-13

    Older adults use a different muscle strategy to cope with postural instability, in which they 'co-contract' the muscles around the ankle joint. It has been suggested that this is a compensatory response to age-related proprioceptive decline however this view has never been assessed directly. The current study investigated the association between proprioceptive acuity and muscle co-contraction in older adults. We compared muscle activity, by recording surface electromyography (EMG) from the bilateral tibialis anterior (TA) and gastrocnemius medialis (GM) muscles, in young (aged 18-34) and older adults (aged 65-82) during postural assessment on a fixed and sway-referenced surface at age-equivalent levels of sway. We performed correlations between muscle activity and proprioceptive acuity, which was assessed using an active contralateral matching task. Despite successfully inducing similar levels of sway in the two age groups, older adults still showed higher muscle co-contraction. A stepwise regression analysis showed that proprioceptive acuity measured using variable error was the best predictor of muscle co-contraction in older adults. However, despite suggestions from previous research, proprioceptive error and muscle co-contraction were negatively correlated in older adults, suggesting that better proprioceptive acuity predicts more co-contraction. Overall, these results suggest that although muscle co-contraction may be an age-specific strategy used by older adults, it is not to compensate for age-related proprioceptive deficits.

  12. Prolonged contraction-relaxation cycle of fast-twitch muscles in parvalbumin knockout mice.

    PubMed

    Schwaller, B; Dick, J; Dhoot, G; Carroll, S; Vrbova, G; Nicotera, P; Pette, D; Wyss, A; Bluethmann, H; Hunziker, W; Celio, M R

    1999-02-01

    The calcium-binding protein parvalbumin (PV) occurs at high concentrations in fast-contracting vertebrate muscle fibers. Its putative role in facilitating the rapid relaxation of mammalian fast-twitch muscle fibers by acting as a temporary buffer for Ca2+ is still controversial. We generated knockout mice for PV (PV -/-) and compared the Ca2+ transients and the dynamics of contraction of their muscles with those from heterozygous (PV +/-) and wild-type (WT) mice. In the muscles of PV-deficient mice, the decay of intracellular Ca2+ concentration ([Ca2+]i) after 20-ms stimulation was slower compared with WT mice and led to a prolongation of the time required to attain peak twitch tension and to an extension of the half-relaxation time. The integral [Ca2+]i in muscle fibers of PV -/- mice was higher and consequently the force generated during a single twitch was approximately 40% greater than in PV +/- and WT animals. Acceleration of the contraction-relaxation cycle of fast-twitch muscle fibers by PV may confer an advantage in the performance of rapid, phasic movements.

  13. Theoretical analysis of oxygen supply to contracted skeletal muscle.

    PubMed

    Groebe, K; Thews, G

    1986-01-01

    Honig and collaborators reported striking contradictions in current understanding of O2 supply to working skeletal muscle. Therefore we re-examined the problem by means of a new composite computer simulation. As inclusion of erythrocytic O2 desaturation and oxygen transport and consumption inside the muscle cell into a single model would entail immense numerical difficulties, we broke up the whole process into its several components: O2 desaturation of erythrocytes O2 transport and consumption in muscle fiber capillary transit time characterizing the period of contact between red cell and muscle fiber. "Erythrocyte model" as well as "muscle fiber model" both consist of a central core cylinder surrounded by a concentric diffusion layer representing the extracellular resistance to O2 diffusion (Fig. 1). Resistance layers in both models are to be conceived of as one and the same anatomical structure--even though in each model their shape is adapted to the respective geometry. By means of this overlap region a spatial connexion between both is given, whereas temporal coherence governing O2 fluxes and red cell spacing is derived from capillary transit time. Analysis of individual components is outlined as follows: Assuming axial symmetry of the problem a numerical algorithm was employed to solve the parabolic system of partial differential equations describing red cell O2 desaturation. Hb-O2 reaction kinetics, free and facilitated O2 diffusion in axial and radial directions, and red cell movement in capillary were considered. Resulting time courses of desaturation, which are considerably faster than the ones computed by Honig et al., are given in the following table (see also Fig. 3). (Formula: see text) Furthermore, we studied the respective importance of the several processes included in our model: Omission of longitudinal diffusion increased desaturation time by 15% to 23%, whereas effects of reaction kinetics and axial movement were 5% and 2% respectively. For time

  14. Contraction-induced lipolysis is not impaired by inhibition of hormone-sensitive lipase in skeletal muscle.

    PubMed

    Alsted, Thomas J; Ploug, Thorkil; Prats, Clara; Serup, Annette K; Høeg, Louise; Schjerling, Peter; Holm, Cecilia; Zimmermann, Robert; Fledelius, Christian; Galbo, Henrik; Kiens, Bente

    2013-10-15

    In skeletal muscle hormone-sensitive lipase (HSL) has long been accepted to be the principal enzyme responsible for lipolysis of intramyocellular triacylglycerol (IMTG) during contractions. However, this notion is based on in vitro lipase activity data, which may not reflect the in vivo lipolytic activity. We investigated lipolysis of IMTG in soleus muscles electrically stimulated to contract ex vivo during acute pharmacological inhibition of HSL in rat muscles and in muscles from HSL knockout (HSL-KO) mice. Measurements of IMTG are complicated by the presence of adipocytes located between the muscle fibres. To circumvent the problem with this contamination we analysed intramyocellular lipid droplet content histochemically. At maximal inhibition of HSL in rat muscles, contraction-induced breakdown of IMTG was identical to that seen in control muscles (P < 0.001). In response to contractions IMTG staining decreased significantly in both HSL-KO and WT muscles (P < 0.05). In vitro TG hydrolase activity data revealed that adipose triglyceride lipase (ATGL) and HSL collectively account for ∼98% of the TG hydrolase activity in mouse skeletal muscle, other TG lipases accordingly being of negligible importance for lipolysis of IMTG. The present study is the first to demonstrate that contraction-induced lipolysis of IMTG occurs in the absence of HSL activity in rat and mouse skeletal muscle. Furthermore, the results suggest that ATGL is activated and plays a major role in lipolysis of IMTG during muscle contractions.

  15. Contraction-induced lipolysis is not impaired by inhibition of hormone-sensitive lipase in skeletal muscle

    PubMed Central

    Alsted, Thomas J; Ploug, Thorkil; Prats, Clara; Serup, Annette K; Høeg, Louise; Schjerling, Peter; Holm, Cecilia; Zimmermann, Robert; Fledelius, Christian; Galbo, Henrik; Kiens, Bente

    2013-01-01

    In skeletal muscle hormone-sensitive lipase (HSL) has long been accepted to be the principal enzyme responsible for lipolysis of intramyocellular triacylglycerol (IMTG) during contractions. However, this notion is based on in vitro lipase activity data, which may not reflect the in vivo lipolytic activity. We investigated lipolysis of IMTG in soleus muscles electrically stimulated to contract ex vivo during acute pharmacological inhibition of HSL in rat muscles and in muscles from HSL knockout (HSL-KO) mice. Measurements of IMTG are complicated by the presence of adipocytes located between the muscle fibres. To circumvent the problem with this contamination we analysed intramyocellular lipid droplet content histochemically. At maximal inhibition of HSL in rat muscles, contraction-induced breakdown of IMTG was identical to that seen in control muscles (P < 0.001). In response to contractions IMTG staining decreased significantly in both HSL-KO and WT muscles (P < 0.05). In vitro TG hydrolase activity data revealed that adipose triglyceride lipase (ATGL) and HSL collectively account for ∼98% of the TG hydrolase activity in mouse skeletal muscle, other TG lipases accordingly being of negligible importance for lipolysis of IMTG. The present study is the first to demonstrate that contraction-induced lipolysis of IMTG occurs in the absence of HSL activity in rat and mouse skeletal muscle. Furthermore, the results suggest that ATGL is activated and plays a major role in lipolysis of IMTG during muscle contractions. PMID:23878361

  16. Effect of taurine depletion on excitation-contraction coupling and Cl- conductance of rat skeletal muscle.

    PubMed

    De Luca, A; Pierno, S; Camerino, D C

    1996-01-25

    The pharmacological action of taurine on skeletal muscle is to stabilize sarcolemma by increasing macroscopic conductance to Cl- (GCl), whereas a proposed physiological role for the amino acid is to modulate excitation-contraction coupling mechanism via Ca2+ availability. To get insight in the physiological role of taurine in skeletal muscle, the effects of its depletion were evaluated on voltage threshold for mechanical activation and GCl with the two intracellular microelectrode method in 'point' voltage clamp mode and current clamp mode, respectively. The experiments were performed on extensor digitorum longus muscle fibers from rats depleted of taurine by a chronic 4 week treatment with guanidinoethane sulfonate, a known inhibitor of taurine transporter. The treatment significantly modified the mechanical threshold of striated fibers; i.e. at each pulse duration they needed significantly less depolarization to contract and the fitted rheobase voltage was more negative by 10 mV with respect to untreated muscle fibers. In parallel, the treatment with guanidinoethane sulfonate produced a significant 40% lowering of GCl. In vitro application of 60 mM of taurine to such depleted muscles almost completely restored the mechanical threshold and increased GCl even above the value of untreated control. However, in vitro application of 60 mM of either taurine or guanidinoethane sulfonate to untreated control muscles did not cause any change of the mechanical threshold but increased GCl by 40% and 21%, respectively. Furthermore, 100 microM of the S-(-) enantiomer of 2-(p-chlorophenoxy)propionic acid almost fully blocked GCl but did not produce any change in the mechanical threshold of normal muscle fibers. The present results show that the large amount of intracellular taurine plays a role in the excitation-contraction coupling mechanism of striated muscle fibers. This action is independent from any effect involving muscle Cl- channels, but it is likely mediated by the

  17. SARCOPLASMIC RETICULUM AND THE TEMPERATURE-DEPENDENT CONTRACTION OF SMOOTH MUSCLE IN CALCIUM-FREE SOLUTIONS

    PubMed Central

    Somlyo, Andrew P.; Devine, Carrick E.; Somlyo, Avril V.; North, Stanley R.

    1971-01-01

    The contractile response of turtle oviduct smooth muscle to acetylcholine after 30 min of incubation of muscles in Ca-free, 4 mM ethylene (bis) oxyethylenenitrilotetraacetic acid (EGTA) solutions at room temperature was greater than the contractile response after 30 min of incubation in the Ca-free medium at 37°C. Incubation in Ca-free solution at 37°C before stimulation with acetylcholine in Ca-free solutions at room temperature also reduced the contractile response, suggesting that activator calcium was lost from the fibers at a faster rate at higher temperatures. Electron micrographs of turtle oviduct smooth muscle revealed a sarcoplasmic reticulum (SR) occupying approximately 4% of the nucleus- and mitochondria-free cell volume. Incubation of oviduct smooth muscle with ferritin confirmed that the predominantly longitudinally oriented structures described as the SR did not communicate with the extracellular space. The SR formed fenestrations about the surface vesicles, and formed close contacts (couplings) with the surface membrane and surface vesicles in oviduct and vena caval smooth muscle; it is suggested that these are sites of electromechanical coupling. Calculation of the calcium requirements for smooth muscle contraction suggest that the amount of SR observed in the oviduct smooth muscle could supply the activator calcium for the contractions observed in Ca-free solutions. Incubation of oviduct smooth muscle in hypertonic solutions increased the electron opacity of the fibers. A new feature of some of the surface vesicles observed in oviduct, vena caval, and aortic smooth muscle was the presence of approximately 10 nm striations running approximately parallel to the openings of the vesicles to the extracellular space. Thick, thin, and intermediate filaments were observed in turtle oviduct smooth muscle, although the number of thick filaments seen in the present study appeared less than that previously found in mammalian smooth muscles. PMID:4331503

  18. Time-dependent changes in Ca2+ sensitivity during phasic contraction of canine antral smooth muscle.

    PubMed Central

    Ozaki, H; Gerthoffer, W T; Publicover, N G; Fusetani, N; Sanders, K M

    1991-01-01

    1. Relationships between cytosolic Ca2+ concentration ([Ca2+]cyt), myosin light chain (MLC) phosphorylation and muscle tension were examined in circular smooth muscle of canine gastric antrum. 2. Electrical slow waves induced a transient increase in [Ca2+]cyt and muscle tension. [Ca2+]cyt increased before the initiation of contraction and reached a maximum before the peak of the phasic contractions. Following the first Ca2+ transient, a second rise in [Ca2+]cyt was often observed. The second Ca2+ transient was of similar magnitude to the first, but only in some cases was this increase in [Ca2+]cyt associated with a second phase of contraction. Relaxation occurred more rapidly than the restoration of resting levels of [Ca2+]cyt. 3. Acetylcholine (ACh; 3 x 10(-7) M) increased the amplitude of Ca2+ transients, caused MLC phosphorylation and increased the force of contraction. The decay of contraction and MLC dephosphorylation preceded that of [Ca2+]cyt. 4. Increasing external K+ (to 25-40 mM) caused a sustained increase in [Ca2+]cyt, but little change in resting tension. This suggests that the Ca2+ sensitivity decreased as [Ca2+]cyt increased. Increasing K+ to 59.5 mM further increased the level of [Ca2+]cyt, induced MLC phosphorylation and caused a transient contraction. When normal levels of K+ were restored, the rates of MLC dephosphorylation and relaxation exceeded the rate of decay in [Ca2+]cyt. 5. Removal of external Ca2+ in depolarized muscles decreased [Ca2+]cyt below the resting level without affecting resting tension. Readmission of Ca2+ to depolarized muscles caused force to develop at [Ca2+]cyt levels below the original resting level, suggesting that Ca2+ sensitivity was increased when the resting level of [Ca2+]cyt was decreased. 6. The phosphatase inhibitor, calyculin-A (10(-6) M), induced tonic contraction and MLC phosphorylation without an increase in [Ca2+]cyt. During these contractures, electrical activity caused transient increases in [Ca2+]cyt and

  19. 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

  20. Changes in nitric oxide and free radical levels in rat gastrocnemius muscle during contraction and fatigue.

    PubMed

    Ibrahim, Mariam Y; Ashour, Osama M

    2011-12-01

    1. The ratio of nitric oxide (NO) to free radicals is critical during skeletal muscle contraction. Changes in this ratio have been suggested to play a role in muscle fatigue. 2. The aim of the present study was to investigate the changes in NO and free radicals during tetanic and subtetanic contraction and fatigue in the gastrocnemius muscle of adult male Wistar rats. 3. Rats were subjected to either low- or high-frequency stimulation (10 and 100 Hz, respectively) of the right gastrocnemius muscle. Both groups were further subdivided into untreated (0.9% NaCl solution), N(G) -nitro-L-arginine methyl ester (L-NAME)-treated and reduced glutathione (GSH)-treated groups. Rats were administered their treatments intraperitoneally 30 min prior to electrical stimulation. 4. Levels of both NO and lipid peroxides increased significantly during peak force contraction for either type of contractions, with a more significant response during subtetanic contraction. Treatment with L-NAME significantly reduced the maximal force and this effect was more marked in the low frequency-stimulated group. Although peroxides levels were reduced by GSH, it had no significant effect on force production. In L-NAME-treated rats, the onset of 50% fatigue was accelerated with a significant increase in peroxides levels, whereas the opposite effects were observed after GSH treatment. 5. Current results reflect the importance of endogenous NO, as an anti-oxidant, in aiding muscle performance by overcoming oxidative stress during fatigue. They provide a possible explanation as to why patients with myopathies like Duchenne muscular dystrophy, in which dystrophin is lacking suffer from muscle weakness and fatigue easily.

  1. Repeated bouts of fast velocity eccentric contractions induce atrophy of gastrocnemius muscle in rats.

    PubMed

    Ochi, Eisuke; Nosaka, Kazunori; Tsutaki, Arata; Kouzaki, Karina; Nakazato, Koichi

    2015-10-01

    One bout of exercise consisting of fast velocity eccentric contractions has been shown to increase muscle protein degradation in rats. The present study tested the hypothesis that muscle atrophy would be induced after four bouts of fast velocity eccentric contractions, but not after four bouts of slow velocity eccentric contractions. Male Wistar rats were randomly placed into 3 groups; fast (180°/s) velocity (180EC, n = 7), slow (30°/s) velocity eccentric exercise (30EC, n = 7), or sham-treatment group (control, n = 7). The 180EC and 30EC groups received 4 sessions of 4 sets of 5 eccentric contractions of triceps surae muscles by extending the ankle joint during evoked electrical stimulation of the muscles, and the control group had torque measures, every 2 days, and all rats were sacrificed 1 day after the fourth session. Medial and lateral gastrocnemius wet mass were 4-6 % smaller, cross-sectional area of medial gastrocnemius was 6-7% smaller, and isometric tetanic torque of triceps surae muscles was 36 % smaller (p < 0.05) for 180EC than control at 1 day after the fourth session, but no such differences were evident between 30EC and control. The expressions of atrophy-related molecules such as FoxO1, FoxO3 and myostatin were upregulated (78-229 %) only for 180EC, but an increase in phosphorylated p70s6k (227%) was found only for 30EC at 1 day after the fourth session (p < 0.05). The level of Bax, a pro-apoptotic protein, was greater (p < 0.05) for 180EC than control. These results support the hypothesis that muscles are atrophied by repeated bouts of fast but not slow velocity eccentric contractions.

  2. Muscle Contraction and Force: the Importance of an Ancillary Network, Nutrient Supply and Waste Removal

    PubMed Central

    Brüggemann, Dagmar A.; Risbo, Jens; Pierzynowski, Stefan G.; Harrison, Adrian P.

    2008-01-01

    Muscle contraction studies often focus solely on myofibres and the proteins known to be involved in the processes of sarcomere shortening and cross-bridge cycling, but skeletal muscle also comprises a very elaborate ancillary network of capillaries, which not only play a vital role in terms of nutrient delivery and waste product removal, but are also tethered to surrounding fibres by collagen ”wires”. This paper therefore addresses aspects of the ancillary network of skeletal muscle at both a microscopic and functional level in order to better understand its role holistically as a considerable contributor to force transfer within muscular tissue. PMID:19325816

  3. Long-term overactivity in the abdominal oblique muscles after 8 weeks bed-rest- possible implications for musculosketletal health

    NASA Astrophysics Data System (ADS)

    Belavy, D. L.; Richardson, C. A.; Wilson, S.; Darnell, R.; Hides, J.; Toppenberg, R.; Elmann-Larsen, B.; Rittweger, J.; Felsenberg, D.

    2005-08-01

    Changes in the human lumbo-pelvic (LP) muscles with unloading has received little attention in microgravity research, even though this body region has evolved with the development of upright posture in 1-g. This study used a specific movement task to examine the function of four LP muscles during 8-weeks of bed-rest and one-year follow-up. The main finding was the development of overactivity in the abdominal internal oblique muscle in the follow-up period. This finding implies that the L-P muscle changes occurring during bedrest do not recover on return to the 1-g environment. These results may have implications for musculo-skeletal health for those in sedentary lifestyles on Earth.

  4. The impact of altered task mechanics on timing and duration of eccentric bi-articular muscle contractions during cycling.

    PubMed

    Connick, Mark J; Li, François-Xavier

    2013-02-01

    In order to understand muscle adaptations to altered task mechanics during cycling, this study investigated the impact of altered seat height and cadence on timing and duration of gastrocnemius (GAST), biceps femoris (BF) and vastus lateralis (VL) eccentric contractions and muscle activation patterns, and cycling economy. Ten male cyclists completed 9 × 5 min of cycling at 3 seat heights and 3 cadences. Three-dimensional leg kinematics and muscle activation patterns were recorded to estimate timing of eccentric muscle contractions. Onset, offset and duration of eccentric contractions and, onset, offset and duration of muscle activation were calculated, along with cycling economy. Duration of GAST and VL eccentric contractions decreased with increasing seat height due to earlier offset of eccentric muscle contractions. Duration of BF eccentric contractions significantly increased with seat height due to a later eccentric contraction offset. Offset of GAST and BF muscle activation occurred earlier with increasing cadence. Cycling economy was significantly affected by cadence but not seat height. The results suggest that as a consequence of altered seat height, proprioceptive feedback is used to fine-tune the timing of bi-articular eccentric muscle contractions. These results may have implications for seat height self-selection.

  5. Treatment with selectin blocking antibodies after lengthening contractions of mouse muscle blunts neutrophil accumulation but does not reduce damage.

    PubMed

    Sloboda, Darcée D; Brooks, Susan V

    2016-01-01

    P- and E-selectins are expressed on the surface of endothelial cells and may contribute to neutrophil recruitment following injurious lengthening contractions of skeletal muscle. Blunting neutrophil, but not macrophage, accumulation after lengthening contractions may provide a therapeutic benefit as neutrophils exacerbate damage to muscle fibers, while macrophages promote repair. In this study, we tested the hypothesis that P- and E-selectins contribute to neutrophil, but not macrophage, accumulation in muscles after contraction-induced injury, and that reducing neutrophil accumulation by blocking the selectins would be sufficient to reduce damage to muscle fibers. To test our hypothesis, we treated mice with antibodies to block P- and E-selectin function and assessed leukocyte accumulation and damage in muscles 2 days after lengthening contractions. Treatment with P/E-selectin blocking antibodies reduced neutrophil content by about half in muscles subjected to lengthening contractions. In spite of the reduction in neutrophil accumulation, we did not detect a decrease in damage 2 days after lengthening contractions. We conclude that P- and/or E-selectin contribute to the neutrophil accumulation associated with contraction-induced muscle damage and that only a portion of the neutrophils that typically accumulate following injurious lengthening contractions is sufficient to induce muscle fiber damage and force deficits. Thus, therapeutic interventions based on blocking the selectins or other adhesion proteins will have to reduce neutrophil numbers by more than 50% in order to provide a benefit.

  6. Suppression of oxidative stress by resveratrol after isometric contractions in gastrocnemius muscles of aged mice.

    PubMed

    Ryan, Michael J; Jackson, Janna R; Hao, Yanlei; Williamson, Courtney L; Dabkowski, Erinne R; Hollander, John M; Alway, Stephen E

    2010-08-01

    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 H(2)O(2) 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.

  7. Spontaneous oscillatory contraction (SPOC) of sarcomeres in skeletal muscle.

    PubMed

    Ishiwata, S; Okamura, N; Shimizu, H; Anazawa, T; Yasuda, K

    1991-01-01

    Skeletal myofibrils spontaneously oscillate under a condition where ATP, ADP, and Pi coexist and the concentration of free Ca2+ is less than about 1 microM. Although this oscillation phenomenon called SPOC is apparently simple, the molecular mechanism seems to be complex. The SPOC condition and the space-time pattern of SPOC wave suggest that the dynamics of association and dissociation of Pi (ADP) is regulated by the mechanical strain imposed on actin and myosin; the enzymatic activity (ATPase) of actomyosin complex and the mechanical event (contraction) are thus coupled to each other. In this sense, the nature of the mechanochemical enzyme, actomyosin ATPase, is revealed in SPOC.

  8. Smooth muscle cell contraction increases the critical buckling pressure of arteries.

    PubMed

    Hayman, Danika M; Zhang, Jinzhou; Liu, Qin; Xiao, Yangming; Han, Hai-Chao

    2013-02-22

    Recent in vitro experiments demonstrated that arteries under increased internal pressure or decreased axial stretch may buckle into the tortuous pattern that is commonly observed in aging or diseased arteries in vivo. It suggests that buckling is a possible mechanism for the development of artery tortuosity. Vascular tone has significant effects on arterial mechanical properties but its effect on artery buckling is unknown. The objective of this study was to determine the effects of smooth muscle cell contraction on the critical buckling pressure of arteries. Porcine common carotid arteries were perfused in an ex vivo organ culture system overnight under physiological flow and pressure. The perfusion pressure was adjusted to determine the critical buckling pressure of these arteries at in vivo and reduced axial stretch ratios (1.5 and 1.3) at baseline and after smooth muscle contraction and relaxation stimulated by norepinephrine and sodium nitroprusside, respectively. Our results demonstrated that the critical buckling pressure was significantly higher when the smooth muscle was contracted compared with relaxed condition (97.3mmHg vs 72.9mmHg at axial stretch ratio of 1.3 and 93.7mmHg vs 58.6mmHg at 1.5, p<0.05). These results indicate that arterial smooth muscle cell contraction increased artery stability.

  9. Smooth Muscle Cell Contraction Increases the Critical Buckling Pressure of Arteries

    PubMed Central

    Hayman, Danika M.; Zhang, Jinzhou; Liu, Qin; Xiao, Yangming; Han, Hai-Chao

    2012-01-01

    Recent in vitro experiments demonstrated that arteries under increased internal pressure or decreased axial stretch may buckle into the tortuous pattern that is commonly observed in aging or diseased arteries in vivo. It suggests that buckling is a possible mechanism for the development of artery tortuosity. Vascular tone has significant effects on arterial mechanical properties but its effect on artery buckling is unknown. The objective of this study was to determine the effects of smooth muscle cell contraction on the critical buckling pressure of arteries. Porcine common carotid arteries were perfused in an ex vivo organ culture system overnight under physiological flow and pressure. The perfusion pressure was adjusted to determine the critical buckling pressure of these arteries at in vivo and reduced axial stretch ratios (1.5 and 1.3) at baseline and after smooth muscle contraction and relaxation stimulated by norepinephrine and sodium nitroprusside, respectively. Our results demonstrated that the critical buckling pressure was significantly higher when the smooth muscle was contracted compared with relaxed condition (97.3mmHg versus 72.9mmHg at axial stretch ratio of 1.3 and 93.7mmHg vs 58.6mmHg at 1.5, p<0.05). These results indicate that arterial smooth muscle cell contraction increased artery stability. PMID:23261241

  10. CCN1 suppresses pulmonary vascular smooth muscle contraction in response to hypoxia.

    PubMed

    Lee, Seon-Jin; Zhang, Meng; Hu, Kebin; Lin, Ling; Zhang, Duo; Jin, Yang

    2015-12-01

    Pulmonary vasoconstriction and increased vascular resistance are common features in pulmonary hypertension (PH). One of the contributing factors in the development of pulmonary vasoconstriction is increased pulmonary artery smooth muscle cell (PASMC) contraction. Here we report that CCN1, an extracellular matrix molecule, suppressed PASMC contraction in response to hypoxia. CCN1 (Cyr61), discovered in past decade, belongs to the Cyr61-CTGF-Nov (CCN) family. It carries a variety of cellular functions, including angiogenesis and cell adhesion, death, and proliferation. Hypoxia robustly upregulated the expression of CCN1 in the pulmonary vessels and lung parenchyma. Given that CCN1 is a secreted protein and functions in a paracine manner, we examined the potential effects of CCN1 on the adjacent smooth muscle cells. Interestingly, bioactive recombinant CCN1 significantly suppressed hypoxia-induced contraction in human PASMCs in vitro. Consistently, in the in vivo functional studies, administration of bioactive CCN1 protein significantly decreased right ventricular pressure in three different PH animal models. Mechanistically, protein kinase A-pathway inhibitors abolished the effects of CCN1 in suppressing PASMC contraction. Furthermore, CCN1-inhibited smooth muscle contraction was independent of the known vasodilators, such as nitric oxide. Taken together, our studies indicated a novel cellular function of CCN1, potentially regulating the pathogenesis of PH.

  11. Superficial aponeurosis of human gastrocnemius is elongated during contraction: implications for modeling muscle-tendon unit.

    PubMed

    Muramatsu, Tadashi; Muraoka, Tetsuro; Kawakami, Yasuo; Fukunaga, Tetsuo

    2002-02-01

    Two questions were addressed in this study: (1) how much strain of the superficial aponeurosis of the human medial gastrocnemius muscle (MG) was obtained during voluntary isometric contractions in vivo, (2) whether there existed inhomogeneity of the strain along the superficial aponeurosis. Seven male subjects, whose knees were extended and ankles were flexed at right angle, performed isometric plantar flexion while elongation of superficial aponeurosis of MG was determined from the movements of the intersections made by the superficial aponeurosis and fascicles using ultrasonography. The strain of the superficial aponeurosis at the maximum voluntary contraction, estimated from the elongation and length data, was 5.6+/-1.2%. There was no significant difference in strain between the proximal and distal parts of the superficial aponeurosis. Based on the present result and that of our previous study for the same subjects (J. Appl. Physiol 90 (2001) 1671), a model was formulated for a contracting uni-pennate muscle-tendon unit. This model, which could be applied to isometric contractions at other angles and therefore of wide use, showed that similar strain between superficial and deep aponeuroses of MG contributed to homogeneous fascicle length change within MG during contractions. These findings would contribute to clarifying the functions of the superficial aponeurosis and the effects of the superficial aponeurosis elongation on the whole muscle behavior.

  12. Suppression of intestinal smooth muscle contraction by 4-ethylguaiacol, a constituent of wood creosote.

    PubMed

    Toyoda, M; Ogata, N; Shibata, T

    1993-11-01

    Wood creosote, a mixture of phenolic compounds, suppresses in vitro contractions of rat intestine. To identify a compound in wood creosote able to inhibit intestinal motility, we screened its constituent phenolic compounds and found 4-ethylguaiacol (4-EG) as an active compound. It suppressed the spontaneous phasic (IC50 = 513 +/- 48 mumol/l) as well as spasmogenic-agent-induced tonic longitudinal contractions of isolated rat ileum in a reversible and concentration-dependent manner. KCl-depolarization-induced tonic contraction, which was susceptible to a calcium channel blocking agent, was also suppressed by 4-EG with an IC50 of 433 +/- 41 mumol/l. Furthermore, calcium-ionophore-induced contraction, which was affected by an influx of extracellular calcium ion that bypassed calcium channels, was suppressed by 4-EG with an IC50 of 97 +/- 18 mumol/l. These results support the concept that the effect of wood creosote to suppress intestinal motility is attributable, partially or entirely, to its component 4-EG and that this effect of 4-EG on the intestinal muscle is produced at some stage(s) of the muscle contraction process after influx of extracellular calcium into the cytosol of smooth muscle.

  13. Making fast-twitch dystrophic muscles bigger protects them from contraction injury and attenuates the dystrophic pathology.

    PubMed

    Gehrig, Stefan M; Koopman, René; Naim, Timur; Tjoakarfa, Clarissa; Lynch, Gordon S

    2010-01-01

    The lack of functional dystrophin protein in Duchenne muscular dystrophy (DMD) renders muscle fibers highly fragile and susceptible to damage during contractions. Contraction-mediated injury is a major contributor to the progressive degeneration and etiology of muscle wasting in DMD. The prevailing understanding is that large fibers are highly susceptible to contraction damage and are affected preferentially, whereas smaller fibers are relatively spared in DMD. We tested the hypothesis that a pharmacological treatment that caused myofiber hypertrophy would increase the susceptibility of muscles from dystrophin-deficient mdx mice to contraction-induced injury, and thus aggravate the dystrophic pathology. The beta-agonist formoterol (100 microg/kg per day, i.p.) was administered to mdx mice for 28 days. Formoterol increased muscle mass, fiber cross-sectional area, and maximum force producing capacity by 30%, 23%, and 21%, respectively, in fast-twitch tibialis anterior muscles of mdx mice. Myofiber hypertrophy and increased maximum force producing capacity were also observed in the predominantly slow-twitch soleus muscles of mdx mice. Our original hypothesis was rejected since tibialis anterior muscles from formoterol-treated mdx mice had lower cumulative force deficits, indicating that they were less susceptible to contraction-induced injury. Formoterol treatment did not affect injury susceptibility in soleus muscles. These findings indicate that making dystrophic muscles bigger protects them from contraction damage and does not aggravate the dystrophic pathophysiology. These novel results further support the contention that anabolic agents have therapeutic potential for muscle wasting conditions including DMD.

  14. Gated /sup 31/P NMR study of tetanic contraction in rat muscle depleted of phosphocreatine

    SciTech Connect

    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 initial 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.

  15. Force-EMG changes during sustained contractions of a human upper airway muscle.

    PubMed

    Schmitt, Kori; DelloRusso, Christiana; Fregosi, Ralph F

    2009-02-01

    Human upper airway and facial muscles support breathing, swallowing, speech, mastication, and facial expression, but their endurance performance in sustained contractions is poorly understood. The muscular fatigue typically associated with task failure during sustained contractions has both central and intramuscular causes, with the contribution of each believed to be task dependent. Previously we failed to show central fatigue in the nasal dilator muscles of subjects that performed intermittent maximal voluntary contractions (MVCs). Here we test the hypothesis that central mechanisms contribute to the fatigue of submaximal, sustained contractions in nasal dilator muscles. Nasal dilator muscle force and EMG activities were recorded in 11 subjects that performed submaximal contractions (20, 35, and 65% MVC) until force dropped to or=3 s, which we defined as task failure. MVC and twitch forces (the latter obtained by applying supramaximal shocks to the facial nerve) were recorded before the trial and at several time points over the first 10 min of recovery. The time to task failure was inversely related to contraction intensity. MVC force was depressed by roughly 30% at task failure in all three trials, but recovered within 2 min. Twitch force fell by 30-44% depending on contraction intensity and remained depressed after 10 min of recovery, consistent with low-frequency fatigue. Average EMG activity increased with time, but never exceeded 75% of the maximal, pretrial level despite task failure. EMG mean power frequency declined by 20-25% in all trials, suggesting reduced action potential conduction velocity at task failure. In contrast, the maximal evoked potential did not change significantly in any of the tasks, indicating that the EMG deficit at task failure was due largely to mechanisms proximal to the neuromuscular junction. Additional experiments using the interpolated twitch technique suggest that subjects can produce about 92

  16. Messenger molecules of the phospholipase signaling system have dual effects on vascular smooth muscle contraction.

    PubMed

    Vidulescu, Cristina; Mironneau, J.; Mironneau, Chantal; Popescu, L. M.

    2000-01-01

    Background and methods. In order to investigate the role of phospholipases and their immediately derived messengers in agonist-induced contraction of portal vein smooth muscle, we used the addition in the organ bath of exogenous molecules such as: phospholipases C, A(2), and D, diacylglycerol, arachidonic acid, phosphatidic acid, choline. We also used substances modulating activity of downstream molecules like protein kinase C, phosphatidic acid phosphohydrolase, or cyclooxygenase. Results. a) Exogenous phospholipases C or A(2), respectively, induced small agonist-like contractions, while exogenous phospholipase D did not. Moreover, phospholipase D inhibited spontaneous contractions. However, when added during noradrenaline-induced plateau, phospholipase D shortly potentiated it. b) The protein kinase C activator, phorbol dibutyrate potentiated both the exogenous phospholipase C-induced contraction and the noradrenaline-induced plateau, while the protein kinase C inhibitor 1-(-5-isoquinolinesulfonyl)-2-methyl-piperazine relaxed the plateau. c) When added before noradrenaline, indomethacin inhibited both phasic and tonic contractions, but when added during the tonic contraction shortly potentiated it. Arachidonic acid strongly potentiated both spontaneous and noradrenaline-induced contractions, irrespective of the moment of its addition. d) In contrast, phosphatidic acid inhibited spontaneous contractile activity, nevertheless it was occasionally capable of inducing small contractions, and when repetitively added during the agonist-induced tonic contraction, produced short potentiations of the plateau. Pretreatment with propranolol inhibited noradrenaline-induced contractions and further addition of phosphatidic acid augmented this inhibition. Choline augmented the duration and amplitude of noradrenaline-induced tonic contraction and final contractile oscillations. Conclusions. These data suggest that messengers produced by phospholipase C and phospholipase A(2

  17. Contraction-Induced Changes in Hydrogen Bonding of Muscle Hydration Water

    PubMed Central

    2015-01-01

    Protein–water interaction plays a crucial role in protein dynamics and hence function. To study the chemical environment of water and proteins with high spatial resolution, synchrotron radiation-Fourier transform infrared (SR-FTIR) spectromicroscopy was used to probe skeletal muscle myofibrils. Observing the OH stretch band showed that water inside of relaxed myofibrils is extensively hydrogen-bonded with little or no free OH. In higher-resolution measurements obtained with single isolated myofibrils, the water absorption peaks were relatively higher within the center region of the sarcomere compared to those in the I-band region, implying higher hydration capacity of thick filaments compared to the thin filaments. When specimens were activated, changes in the OH stretch band showed significant dehydrogen bonding of muscle water; this was indicated by increased absorption at ∼3480 cm–1 compared to relaxed myofibrils. These contraction-induced changes in water were accompanied by splitting of the amide I (C=O) peak, implying that muscle proteins transition from α-helix to β-sheet-rich structures. Hence, muscle contraction can be characterized by a loss of order in the muscle–protein complex, accompanied by a destructuring of hydration water. The findings shed fresh light on the molecular mechanism of muscle contraction and motor protein dynamics. PMID:24803993

  18. Analysis of the electrical muscle activity during maximal contraction and the influence of ischaemia.

    PubMed

    Dietz, V

    1978-07-01

    (1) The mechanism underlying muscle fatigue has been studied in maintained isometric maximal contraction of the wrist flexor muscles under normal and ischaemic conditions. Automatic EMG analysis has been used to show the level of motor unit firing rates in fatiguing contractions. (2) Under non-ischaemic conditions the decay of force, turns and amplitude is about the same, whereas during ischaemia force and to a lesser extent amplitude pulses, decline steeply towards zero, while turns, representing the number of impulses, remain in the non-ischaemic range. (3) Depending on the duration of the ischaemia applied before contraction, force and amplitude are initially reduced but turns are nearly unchanged compared with the non-ischaemic values. It is suggested, that this is due to nerve blocking of high threshold motor units. (4) The results show that transmission failure at the neuromuscular junction is a minor factor in muscle fatigue and that this structure is not greatly affected by ischaemia. (5) It is believed that in the first phase of muscle fatigue the force decline is connnected with a slowing of discharge rates. This change of firing frequencies with time must be considered optimal in respect to the force produced because higher as well as lower discharge rates would reduce the force development. In the later phase it is possible that contractile element fatigue, connected with a reduction of action potential amplitudes of single muscle fibres, predominates, especially when the blood supply is obstructed.

  19. Finite element modeling reveals complex strain mechanics in the aponeuroses of contracting skeletal muscle.

    PubMed

    Chi, Sheng-Wei; Hodgson, John; Chen, Jiun-Shyan; Reggie Edgerton, V; Shin, David D; Roiz, Ronald A; Sinha, Shantanu

    2010-05-07

    A finite element model was used to investigate the counter-intuitive experimental observation that some regions of the aponeuroses of a loaded and contracting muscle may shorten rather than undergo an expected lengthening. The model confirms the experimental findings and suggests that pennation angle plays a significant role in determining whether regions of the aponeuroses stretch or shorten. A smaller pennation angles (25 degrees ) was accompanied by aponeurosis lengthening whereas a larger pennation angle (47 degrees ) was accompanied by mixed strain effects depending upon location along the length of the aponeurosis. This can be explained by the Poisson effect during muscle contraction and a Mohr's circle analogy. Constant volume constraint requires that fiber cross sectional dimensions increase when a fiber shortens. The opposing influences of these two strains upon the aponeurosis combine in proportion to the pennation angle. Lower pennation angles emphasize the influence of fiber shortening upon the aponeurosis and thus favor aponeurosis compression, whereas higher pennation angles increase the influence of cross sectional changes and therefore favor aponeurosis stretch. The distance separating the aponeuroses was also found to depend upon pennation angle during simulated contractions. Smaller pennation angles favored increased aponeurosis separation larger pennation angles favored decreased separation. These findings caution that measures of the mechanical properties of aponeuroses in intact muscle may be affected by contributions from adjacent muscle fibers and that the influence of muscle fibers on aponeurosis strain will depend upon the fiber pennation angle.

  20. Lower working heights decrease contraction intensity of shoulder muscles in a herringbone 30° milking parlor.

    PubMed

    Cockburn, Marianne; Schick, Matthias; Maffiuletti, Nicola A; Gygax, Lorenz; Savary, Pascal; Umstätter, Christina

    2017-03-29

    Musculoskeletal disorders have been a main concern in milkers for many years. To improve posture, a formula was developed in a previous study to calculate ergonomically optimal working heights for various milking parlor types. However, the working height recommendations based on the formula for the herringbone 30° parlor were broad. To clarify the recommendations for the optimal working height, we investigated the effect of working height on upper limb and shoulder muscle contraction intensities. We evaluated 60 milking cluster attachment procedures in a herringbone 30° milking parlor in 7 men and 9 women. Specifically, we examined the effect of working height on muscle contraction intensity of 4 arm and shoulder muscles bilaterally (flexor carpi ulnaris, biceps brachii, deltoideus anterior, and upper trapezius) by using surface electromyography. The working heights (low, medium, and high), which reflect the ratio of the subject's height to the height of the udder base, were used in the milking health formula to determine and fit individual depth of pits. Data were evaluated for each muscle and arm side in the functions holding and attaching. Statistical analysis was performed using linear mixed effects models, where muscle contraction intensity served as a target variable, whereas working height coefficient, sex, subject height, and repetition were treated as fixed effects, and repetition group nested in working height nested in subject was considered a random effect. Contraction intensities decreased with decreasing working height for the deltoideus anterior and upper trapezius, but not for the flexor carpi ulnaris or the biceps brachii muscles in both holding and attaching arm functions. We found that milking at a lower working height reduced muscle contraction intensities of the shoulder muscles. Women showed higher contraction intensities than men, whereas subject height had no effect. The study demonstrated that a lower working height decreased muscular

  1. The breakdown of adenosine triphosphate in the contraction cycle of the frog sartorius muscle

    PubMed Central

    Mommaerts, W. F. H. M.; Wallner, A.

    1967-01-01

    1. It is confirmed that a fluorodinitrobenzene (FDNB)-treated frog sartorius muscle does not split phosphorylcreatine in the course of its contraction cycle, but does use adenosine triphosphate (ATP). 2. Good stoicheiometric relations between the diminution of ATP and the formation of adenosine diphosphate (ADP), adenosine monophosphate (AMP) and phosphate are obtained, and in a 0·2 sec tetanus at 0° C the net break-down of ATP amounts to 0·27, the total equivalent break-down to 0·34 μmoles/g. 3. There is no difference in this quantity between muscles interrupted at the height of contraction and those that have also relaxed, and, in experiments specifically designed to determine relaxation metabolism separately, no such metabolism is found. Thus, all the ATP-break-down occurs in the contraction phase. PMID:6065882

  2. Nonlinear summation of contractions in cat muscles. I. Early depression

    PubMed Central

    1981-01-01

    Nerves to fast- and slow-twitch cat muscles were stimulated with various numbers of supramaximal pulses under isometric conditions. By subtracting the force produced by j - 1 pulses from that produced by j pulses, the contribution of the j th pulse could be compared with the response to one pulse (twitch response). A less-than-linear summation (depression) was observed during the rising phase of the twitch. This depression became increasingly prominent and longer in duration with repetitive stimulation. A more-than-linear summation (facilitation) was observed during the falling phase of the twitch, which became increasingly delayed and smaller in amplitude with repetitive stimulation. The early depression could be abolished for the first few pulses by Dantrolene [1-(5-p-nitrophenyl) furfurilidene amino hydantoin sodium hydrate], which reduced Ca++ release from the sarcoplasmic reticulum. The depression was less prominent at short muscle lengths or with stimulation of single motor units. A first-order, saturable reaction such as Ca++ binding to troponin or actin binding to myosin can quantitatively account for the early depression. PMID:7328403

  3. A comprehensive mathematical framework for modeling intestinal smooth muscle cell contraction with applications to intestinal edema.

    PubMed

    Young, Jennifer; Ozisik, Sevtap; Riviere, Beatrice; Shamim, Muhammad

    2015-04-01

    The contraction of intestinal smooth muscle cells (ISMCs) involves many coordinated biochemical and mechanical processes. In this work, we present a framework for modeling ISMC contractility that begins with chemical models of calcium dynamics, continues with myosin light chain phosphorylation and force generation, and ends with a cell model of the ISMC undergoing contraction-relaxation. The motivation for developing this comprehensive framework is to study the effects of edema (excess fluid build-up in the muscle tissue) on ISMC contractility. The hypothesis is that more fluid equates to dilution of an external stimulis, eventually leading to reduced contractility. We compare our results to experimental data collected from normal versus edematous intestinal muscle tissue.

  4. Dynamic reconstruction of full-thickness abdominal wall defects using free innervated vastus lateralis muscle flap combined with free anterolateral thigh flap.

    PubMed

    Iida, Takuya; Mihara, Makoto; Narushima, Mitsunaga; Todokoro, Takeshi; Hara, Hisako; Yoshimatu, Hidehiko; Koshima, Isao; Kadono, Takafumi

    2013-03-01

    Reconstruction of full-thickness abdominal wall defects remains a difficult surgical challenge. Although various reconstructive methods, including artificial mesh, pedicled and free flaps, have been reported, most reported reconstruction of only the fascia layer, leaving the resected rectus abdominis muscle unreconstructed. However, recent studies suggested the importance of dynamic reconstruction with functional muscle in preventing abdominal hernia in the long-term. According to the principle of reconstructive surgery, "replace lost tissue with similar tissue," a functionally and aesthetically ideal reconstruction is to reconstruct all components of the abdominal wall structure, including skin, subcutaneous fat, fascia, and muscle. We present 2 cases with full-thickness abdominal wall defects in the upper abdominal region, which we reconstructed with a free innervated vastus lateralis muscle flap combined with a free anterolateral thigh flap. The motor nerve of the vastus lateralis muscle was sutured with the intercostal nerve, and reinnervation was confirmed by electromyography. This method allows reconstruction of all components of the abdominal wall with a single flap, and dynamic reconstruction is achieved which will reduce the risk of postoperative hernia. We believe this method can be a good option for reconstruction of full-thickness abdominal wall defects with long-term stability.

  5. Novel expression of a functional glycine receptor chloride channel that attenuates contraction in airway smooth muscle

    PubMed Central

    Yim, Peter D.; Gallos, George; Xu, Dingbang; Zhang, Yi; Emala, Charles W.

    2011-01-01

    Airway smooth muscle (ASM) contraction is an important component of the pathophysiology of asthma. Taurine, an agonist of glycine receptor chloride (GlyR Cl−) channels, was found to relax contracted ASM, which led us to question whether functional GlyR Cl− channels are expressed in ASM. Messenger RNA for β (GLRB), α1 (GLRA1), α2 (GLRA2), and α4 (GLRA4) subunits were found in human (Homo sapiens) and guinea pig (Cavia porcellus) tracheal smooth muscle. Immunoblotting confirmed the protein expression of GLRA1 and GLRB subunits in ASM. Electrical activity of cultured human ASM cells was assessed using a fluorescent potentiometric dye and electrophysiological recordings. Glycine increased current and significantly increased fluorescence in a dose-dependent manner. The GlyR Cl− channel antagonist strychnine significantly blocked the effects of glycine on potentiometric fluorescence in ASM cells. Guinea pig airway ring relaxation of ACh-induced contractions by isoproterenol was significantly left-shifted in the presence of glycine. This effect of glycine was blocked by pretreatment with the GlyR Cl− channel antagonist strychnine. Glycine treatment during tachykinin- and acetylcholine-induced contractions significantly decreased the maintenance of muscle force compared to control. GlyR Cl− channels are expressed on ASM and regulate smooth muscle force and offer a novel target for therapeutic relaxation of ASM.—Yim, P. D., Gallos, G., Xu, D., Zhang, Y., Emala, C. W. Novel expression of a functional glycine receptor chloride channel that attenuates contraction in airway smooth muscle. PMID:21282206

  6. Muscle Contraction Induces Acute Hydroxymethylation of the Exercise-Responsive Gene Nr4a3

    PubMed Central

    Pattamaprapanont, Pattarawan; Garde, Christian; Fabre, Odile; Barrès, Romain

    2016-01-01

    Exercise training triggers numerous positive adaptations through the regulation of genes controlling muscle structure and function. Epigenetic modifications, including DNA methylation, participate in transcriptional activation by allowing the recruitment of the transcription machinery to gene promoters. Exercise induces dynamic DNA demethylation at gene promoters; however, the contribution of the demethylation precursor hydroxymethylcytosine is unknown. Given the evanescent nature of hydroxymethylcytosine, a muscle contraction model that allows for the collection of samples that are repeatedly stimulated over time is required to determine whether contraction-induced demethylation is preceded by changes in the hydroxymethylcytosine level. Here, we established an acute skeletal muscle contraction model to mimic the effects of acute exercise on gene expression. We used this model to investigate the effect of muscle contraction on DNA demethylation and hydroxymethylation. First, we performed an acute exercise study in healthy humans to identify an exercise-responsive gene that we could study in culture. We identified the nuclear receptor subfamily 4 group A member 3 (Nr4a3) gene with the highest fold-expression increase after acute exercise. We then refined an electrical pulse stimulation (EPS) protocol that could induce expression of the Nr4a3 gene in C2C12 myotubes. Using targeted bisulfite sequencing, we found that in response to EPS, a region of the Nr4a3 promoter is rapidly demethylated at 60 min and re-methylated at 120 min. Of interest, hydroxymethylation of the differentially methylated region of Nr4a3 promoter after EPS was elevated immediately after EPS, with lowest levels reached at 60 min after EPS. In conclusion, we have established a cell culture-based protocol to mimic the acute transcriptional responses to exercise. Furthermore, we provide insight into the mechanism by which the exercise-responsive gene Nr4a3 is demethylated after muscle

  7. Human skeletal muscle metabolic economy in vivo: effects of contraction intensity, age, and mobility impairment.

    PubMed

    Christie, Anita D; Tonson, Anne; Larsen, Ryan G; DeBlois, Jacob P; Kent, Jane A

    2014-11-01

    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.

  8. Modulation of corticospinal excitability during lengthening and shortening contractions in the first dorsal interosseus muscle of humans.

    PubMed

    Sekiguchi, Hirofumi; Kohno, Yutaka; Hirano, Tatsuya; Akai, Masami; Nakajima, Yasoichi; Nakazawa, Kimitaka

    2007-04-01

    Lengthening and shortening contractions are the fundamental patterns of muscle activation underlying various movements. It is still unknown whether or not there is a muscle-specific difference in such a fundamental pattern of muscle activation. The purpose of this study was, therefore, to investigate whether or not the relationship between lengthening and shortening contractions in the modulation of corticospinal excitability in the first dorsal interosseus (FDI) muscle is the same as that of previously tested muscles because the hand muscles are anatomically and functionally different from the other muscles. To this end, we investigated the relationship between the input-output curves of the corticospinal pathway (i.e., the relationship between the stimulus intensities vs. the area of motor-evoked potentials) during lengthening and shortening contractions in 17 healthy subjects. The shape of this relationship was sigmoidal and characterized by a plateau value, maximum slope, and threshold. The plateau value was at the same level between lengthening and shortening contractions. However, the maximum slope (P < 0.01) and threshold (P < 0.01) were significantly higher during lengthening contractions than during shortening contractions. These findings were different from the results of other muscles tested in previous studies (i.e., the soleus muscle and the elbow flexors). That is to say, the plateau value and the maximum slope during lengthening contractions were significantly lower than those during shortening contractions in previous studies. This study provides tentative evidence that the relationship between lengthening and shortening contractions in the modulation of corticospinal excitability differs between muscles, indicating that the underlying neural control is not necessarily the same even though the fundamental patterns of muscle activation are carried out.

  9. Decreased vascular smooth muscle cell density in medial degeneration of human abdominal aortic aneurysms.

    PubMed Central

    López-Candales, A.; Holmes, D. R.; Liao, S.; Scott, M. J.; Wickline, S. A.; Thompson, R. W.

    1997-01-01

    Abdominal aortic aneurysms (AAAs) are characterized by structural deterioration of the aortic wall leading to progressive aortic dilatation and eventual rupture. The histopathological changes in AAAs are particularly evident within the elastic media, which is normally dominated by vascular smooth muscle cells (SMCs). To determine whether a decrease in vascular SMCs contributes to medial degeneration, we measured SMC density in 21 normal and pathological human abdominal aortic tissue specimens using immunohistochemistry for alpha-SMC actin and direct cell counts (medial SMCs per high-power field (HPF)). Medial SMC density was not significantly different between normal aorta (n = 5; 199.5 +/- 14.9 SMCs/HPF) and atherosclerotic occlusive disease (n = 6; 176.4 +/- 13.9 SMCs/HPF), but it was reduced by 74% in AAA (n = 10; 50.9 +/- 6.1 SMCs/HPF; P < 0.01 versus normal aorta). Light and electron microscopy revealed no evidence of overt cellular necrosis, but SMCs in AAAs exhibited ultrastructural changes consistent with apoptosis. Using in situ end-labeling (ISEL) of fragmented DNA to detect apoptotic cells, up to 30% of aortic wall cells were ISEL positive in AAAs. By double-labeling techniques, many of these cells were alpha-actin-positive SMCs distributed throughout the degenerative media. In contrast, ISEL-positive cells were observed only within the intimal plaque in atherosclerotic occlusive disease. The amount of p53 protein detected by immunoblotting was increased nearly fourfold in AAA compared with normal aorta and atherosclerotic occlusive disease (P < 0.01), and immunoreactive p53 was localized to lymphocytes and residual SMCs in the aneurysm wall. Using reverse transcription polymerase chain reaction assays a substantial amount of p53 mRNA expression was observed in AAAs. These results demonstrate that medial SMC density is significantly decreased in human AAA tissues associated with evidence of SMC apoptosis and increased production of p53, a potential

  10. The effect of deuterium oxide (D sub 2 O) on in vitro vascular smooth muscle contraction

    SciTech Connect

    McWilliam, T.M.; Liepins, A.; Rankin, A.J. )

    1990-02-26

    Deuterium oxide (D{sub 2}O), a stable nonradioactive isotope of water, has been demonstrated to reduce L-type calcium channel conductance in isolated myocytes. Since the concentration of intracellular free calcium has been implicated in the mechanism of vascular smooth muscle contraction, the authors investigated whether it inhibits contraction of vascular smooth muscle. Phenylephrine concentration-contraction curves were carried out in the rat aortic ring preparation to determine whether D{sub 2}O inhibits contraction of rat aorta induced through activation of receptor-operated calcium channels. D{sub 2}O depressed these response curves in a concentration dependent manner with 50% inhibition of maximum contraction observed with 60% D{sub 2}O; this effect proved to be reversible and non-toxic. D{sub 2}O also depressed potassium chloride curves, demonstrating an effect on voltage-operated calcium channels. Since vascular endothelium releases endothelium-derived relaxing factor (EDRF) when stimulated by a range of pharmacological agents, it was examined whether the endothelium has a role in these actions of D{sub 2}O on vascular contraction. Mechanical disruption of the endothelium had no effect.

  11. 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.

  12. The Caenorhabditis elegans unc-93 gene encodes a putative transmembrane protein that regulates muscle contraction

    PubMed Central

    1992-01-01

    unc-93 is one of a set of five interacting genes involved in the regulation or coordination of muscle contraction in Caenorhabditis elegans. Rare altered-function alleles of unc-93 result in sluggish movement and a characteristic "rubber band" uncoordinated phenotype. By contrast, null alleles cause no visibly abnormal phenotype, presumably as a consequence of the functional redundancy of unc-93. To understand better the role of unc-93 in regulating muscle contraction, we have cloned and molecularly characterized this gene. We isolated transposon- insertion alleles and used them to identify the region of DNA encoding the unc-93 protein. Two unc-93 proteins differing at their NH2 termini are potentially encoded by transcripts that differ at their 5' ends. The putative unc-93 proteins are 700 and 705 amino acids in length and have two distinct regions: the NH2 terminal portion of 240 or 245 amino acids is extremely hydrophilic, whereas the rest of the protein has multiple potential membrane-spanning domains. The unc-93 transcripts are low in abundance and the unc-93 gene displays weak codon usage bias, suggesting that the unc-93 protein is relatively rare. The unc-93 protein has no sequence similarity to proteins listed in current data- bases. Thus, unc-93 is likely to encode a novel membrane-associated muscle protein. We discuss possible roles for the unc-93 protein either as a component of an ion transport system involved in excitation- contraction coupling in muscle or in coordinating muscle contraction between muscle cells by affecting the functioning of gap junctions. PMID:1313436

  13. Restoration of excitation-contraction coupling and slow calcium current in dysgenic muscle by dihydropyridine receptor complementary DNA

    NASA Astrophysics Data System (ADS)

    Tanabe, Tsutomu; Beam, Kurt G.; Powell, Jeanne A.; Numa, Shosaku

    1988-11-01

    Microinjection of an expression plasmid that carries complementary DNA encoding the receptor for dihydropyridine calcium channel blockers of skeletal muscle restores both excitation-contraction coupling and slow calcium current in cultured skeletal muscle cells from mice with muscular dysgenesis. This suggests that the dihydropyridine receptor in the transverse tubule membrane of skeletal muscle functions both as the voltage sensor for excitation-contraction coupling and as the slow calcium channel.

  14. 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

  15. 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.

  16. Changes in trunk muscle activation and lumbar-pelvic position associated with abdominal hollowing and reach during a simulated manual material handling task.

    PubMed

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

    2007-03-01

    The purpose of this study was to investigate the effect of abdominal hollowing (AH) on trunk muscle activation and lumbar-pelvic motion during a controlled lift and replace task. Surface electromyograms were recorded from five abdominal and two back muscle sites. Sagittal lumbar-pelvic motion was recorded by video. Subjects lifted a 3.8 kg load in normal, maximum and extreme reaches, first while performing their preferred lifting style (PLS) and then maintaining an AH technique. The external oblique muscle site activities were significantly higher (p < 0.05) for the AH technique (ranging from 7-20% of maximal voluntary activation (MVIC)) than at any of the abdominal sites for the PLS (ranging from 2-10% MVIC). Differences were found among abdominal sites for the AH, but not for the PLS. The back muscle site activities (ranging from 9-30% MVIC) were significantly higher (p < 0.05) than for any of the abdominal muscles for all conditions, except for the anterior external oblique for AH. The pelvic and lumbar angles changed significantly (p < 0.05) between normal and maximal reaches and between techniques. The AH technique altered abdominal muscle activation amplitudes, with minimal differences in trunk extensors compared to the PLS. The AH resulted in more posterior pelvic tilt.

  17. Twitch potentiation induced by stimulated and voluntary isometric contractions at various torque levels in human knee extensor muscles.

    PubMed

    Miyamoto, Naokazu; Yanai, Toshimasa; Kawakami, Yasuo

    2011-03-01

    The purpose of this study was to compare the extent of twitch potentiation (TP) after stimulated or voluntary contractions at identical intensities for the human knee extensor muscles. Isometric knee extensions of 10 s were performed at 20%, 40%, and 60% of maximal voluntary contraction (MVC) torque level, through percutaneous electrical stimulation of the quadriceps at 80 Hz or voluntary contraction. Twitch responses were evoked by stimulating the femoral nerve percutaneously with supramaximal intensity. The extent of TP after the stimulated contraction was greater than that after the voluntary contraction at the 20% MVC torque level, whereas a stimulated contraction induced a smaller extent of TP than did a voluntary contraction at contraction intensities higher than 40% MVC. We suggest that this contraction intensity dependence of differences in TP after stimulated and voluntary isometric conditioning contractions is responsible for differences in the recruitment pattern of motor units during the conditioning contractions.

  18. 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..

  19. Extracting low-velocity concentric and eccentric dynamic muscle properties from isometric contraction experiments.

    PubMed

    Rockenfeller, R; Günther, M

    2016-08-01

    Determining dynamic properties of mammalian muscles, such as activation characteristics or the force-velocity relation, challenges the experimentalist. Tracking system, apparatus stiffness, load oscillation, force transducer, other sensors, and additional measuring devices may be incorporated, integrated and evaluated in an experimental set-up. In contrast, isometric contraction experiments (ICEs) are less challenging, but are generally not considered to reveal dynamic muscle properties. Yet, a sensitivity analysis of our muscle model discloses the influence of concentric, eccentric and activation parameters on isometric force development. Accordingly, we used solely experimental ICE data to identify muscle model parameters that generally describe concentric as well as eccentric muscle performance. In addition, we compared two different activation dynamics in regards to their physiological relevance to improve model-fits to ICE data. To this end, we optimized different combinations of such dynamic parameter subsets with respect to their influence on contraction solutions. Depending on muscle length in our optimized model, the contractile element reached shortening peaks during activation in the range 9-39% of its maximum contraction velocity, and about 8-25% during lengthening when deactivated. As a first result, we suggest one formulation of activation dynamics to be superior. Second, the step in slope of the force-velocity relation at isometric force was found to be the least influential among all dynamic parameters. Third, we suggest a specially designed isometric experimental set-up to estimate this transition parameter. Fourth, because of an inconsistency in literature, we developed a simple method to determine switching times of the neural stimulation and thus electro-mechanical delay (EMD) values from measuring muscle force in ICEs only.

  20. Contraction-induced injury to single permeabilized muscle fibers from normal and congenitally-clefted goat palates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A goat model in which cleft palate is induced by the plant alkaloid, anabasine was used to determine muscle fiber integrity of the levator veli palatine (LVP) muscle. It was determined that muscle fiber type, size, and sensitivity to contraction-induced injury was different between cleft palate ind...

  1. 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.

  2. Mechanism of vanadate-induced contraction of airways smooth muscle of the guinea-pig.

    PubMed Central

    Nayler, R. A.; Sparrow, M. P.

    1983-01-01

    The characteristics of vanadate-induced contraction of airways smooth muscle are described in isolated preparations of guinea-pig central and peripheral airways. Vanadate (1-1000 microM) induced sustained contractions of trachea and lung parenchymal strips within 1 min of challenge. It was more potent (P less than 0.001) on the lung strip (EC50 = 63 microM) than on the trachea (EC50 = 123 microM). The lung strip also developed greater maximum isometric tension (P less than 0.001) than the trachea. The efficacy on the lung strip was 2 and the trachea 0.6, relative to the response to acetylcholine (efficacy = 1). Vanadate-induced contractions of the trachea were not inhibited by atropine, mepyramine, phentolamine or indomethacin, nor after mast cell depletion by compound 48/80, showing that contractions were not mediated via specific receptors or by release of endogenous mediators of tone. Inorganic phosphate specifically inhibited vanadate responses in a dose-dependent and reversible manner, suggesting a common site of action. Contractions could be elicited in depolarized muscle and after treatment with ouabain plus propranolol, showing that membrane depolarization and inhibition of the Na, K-ATPase system were not involved in the contractile action of vanadate. Pretreatment of tracheal smooth muscle with verapamil had no influence on contractions elicited by vanadate. After removal of extracellular calcium, vanadate-induced contractions declined slowly with time, indicating that influx of extracellular calcium was not giving rise to contractions elicited by vanadate. Vanadate markedly increased the rate of calcium efflux from trachealis muscle loaded with 45Ca into both Ca2+-free and normal Krebs solutions; this is compatible with vanadate mobilizing an intracellular store of Ca2+. Such a store involving sites with Ca-ATPase activity would be consistent with the action of vanadate in isolated membrane preparations. Membrane-skinned tracheal fibres contracted by

  3. Gravitational effects on human cardiovascular responses to isometric muscle contractions

    NASA Astrophysics Data System (ADS)

    Bonde-Petersen, Flemmig; Suzuki, Yoji; Sadamoto, Tomoko

    Isometric exercise induces profound cardiovascular adaptations increasing mean arterial pressure and heart rate. We investigated effects of simulated +Gz and -Gz respectively on the central and peripheral cardiovascular system. Sustained handgrip exercise was performed at 40% of maximum for 2 minutes in five subjects. This maneuver increased mean arterial pressure by 40-45 mm Hg both during head out water immersion which simulates weightlessness, as well as bedrest during -25, 0, and +25 degrees tilt from the horizontal. Lower body negative pressure (-60 mm Hg for 10 min) attenuated the response to handgrip exercise to 30 mm Hg. It also increased the heart rate minimally by about 20 beats per minute while the water immersion, as well as head up, head down and horizontal bedrest showed increments of about 50 beats per min. It was concluded that the response to isometric contraction is mediated through the high pressure baroreceptors, because similar responses were seen during stresses producing a wide variation in central venous pressure. During lower body negative pressure the increased sympathetic nervous activity itself increased resting heart rate and mean arterial pressure. The responses to static exercise were, therefore, weaker.

  4. Vascular smooth muscle contraction evoked by cell volume modulation: role of the cytoskeleton network.

    PubMed

    Koltsova, Svetlana V; Gusakova, Svetlana V; Anfinogenova, Yana J; Baskakov, Mikhail B; Orlov, Sergei N

    2008-01-01

    Previously, we reported that hyposmotic swelling evoked transient vascular smooth muscle cell (SMC) contraction that was completely abolished by L-type Ca(2+) channel blockers. In contrast, sustained contraction revealed in hyper- and isoosmotically-shrunken SMCs was insensitive to L-type channel blockers and was diminished in Ca(2+)-free medium by only 30-50%. Several research groups reported cell volume-dependent cytoskeleton network rearrangements. This study examines the role of cytoskeleton proteins in cell volume-dependent contraction of endothelium-denuded vascular smooth muscle rings (VSMR) from the rat thoracic aorta. Hyperosmotic shrinkage and hyposmotic swelling were triggered by modulation of medium osmolality; isosmotic shrinkage was induced by VSMR transfer from hypo- to isosmotic medium. The relative content of globular (G) and fibrillar (F) actin was estimated by fluorescence microscopy. Hyperosmotic shrinkage and hyposmotic swelling led to elevation of the F-actin/G-actin ratio by 2.5- and 1.8-fold respectively. Contraction of shrunken and swollen VSMR was insensitive to modulators of microtubules such as vinblastine, colchicine and docetaxel. Microfilament disassembly by cytochalasin B resulted in dramatic attenuation of the maximal amplitude of contraction of hyperosmotically-shrunken and hyposmotically-swollen VSMR, and almost completely abolished the contraction triggered by isosmotic shrinkage. These data suggest that both L-type Ca(2+) channel-mediated contraction of swollen vascular SMC and Ca(2+)(o)-insensitive contractions of shrunken cells are triggered by reorganization of the microfilament network caused by elevation of the F-actin/G-actin ratio.

  5. Ca2+-induced contraction of cat esophageal circular smooth muscle cells.

    PubMed

    Cao, W; Chen, Q; Sohn, U D; Kim, N; Kirber, M T; Harnett, K M; Behar, J; Biancani, P

    2001-04-01

    ACh-induced contraction of esophageal circular muscle (ESO) depends on Ca2+ influx and activation of protein kinase Cepsilon (PKCepsilon). PKCepsilon, however, is known to be Ca2+ independent. To determine where Ca2+ is needed in this PKCepsilon-mediated contractile pathway, we examined successive steps in Ca2+-induced contraction of ESO muscle cells permeabilized by saponin. Ca2+ (0.2-1.0 microM) produced a concentration-dependent contraction that was antagonized by antibodies against PKCepsilon (but not by PKCbetaII or PKCgamma antibodies), by a calmodulin inhibitor, by MLCK inhibitors, or by GDPbetas. Addition of 1 microM Ca2+ to permeable cells caused myosin light chain (MLC) phosphorylation, which was inhibited by the PKC inhibitor chelerythrine, by D609 [phosphatidylcholine-specific phospholipase C inhibitor], and by propranolol (phosphatidic acid phosphohydrolase inhibitor). Ca2+-induced contraction and diacylglycerol (DAG) production were reduced by D609 and by propranolol, alone or in combination. In addition, contraction was reduced by AACOCF(3) (cytosolic phospholipase A(2) inhibitor). These data suggest that Ca2+ may directly activate phospholipases, producing DAG and arachidonic acid (AA), and PKCepsilon, which may indirectly cause phosphorylation of MLC. In addition, direct G protein activation by GTPgammaS augmented Ca2+-induced contraction and caused dose-dependent production of DAG, which was antagonized by D609 and propranolol. We conclude that agonist (ACh)-induced contraction may be mediated by activation of phospholipase through two distinct mechanisms (increased intracellular Ca2+ and G protein activation), producing DAG and AA, and activating PKCepsilon-dependent mechanisms to cause contraction.

  6. Contraction level-related modulation of corticomuscular coherence differs between the tibialis anterior and soleus muscles in humans.

    PubMed

    Ushiyama, Junichi; Masakado, Yoshihisa; Fujiwara, Toshiyuki; Tsuji, Tetsuya; Hase, Kimitaka; Kimura, Akio; Liu, Meigen; Ushiba, Junichi

    2012-04-01

    The sensorimotor cortex activity measured by scalp EEG shows coherence with electromyogram (EMG) activity within the 15- to 35-Hz frequency band (β-band) during weak to moderate intensity of isometric voluntary contraction. This coupling is known to change its frequency band to the 35- to 60-Hz band (γ-band) during strong contraction. This study aimed to examine whether such contraction level-related modulation of corticomuscular coupling differs between muscles with different muscle compositions and functions. In 11 healthy young adults, we quantified the coherence between EEG over the sensorimotor cortex and rectified EMG during tonic isometric voluntary contraction at 10-70% of maximal voluntary contraction of the tibialis anterior (TA) and soleus (SOL) muscles, respectively. In the TA, the EEG-EMG coherence shifted from the β-band to the γ-band with increasing contraction level. Indeed, the magnitude of β-band EEG-EMG coherence was significantly decreased, whereas that of γ-band coherence was significantly increased, when the contraction level was above 60% of maximal voluntary contraction. In contrast to the TA, the SOL showed no such frequency changes of EEG-EMG coherence with alterations in the contraction levels. In other words, the maximal peak of EEG-EMG coherence in the SOL existed within the β-band, irrespective of the contraction levels. These findings suggest that the central nervous system regulates the frequency of corticomuscular coupling to exert the desired levels of muscle force and, notably, that the applicable rhythmicity of the coupling for performing strong contractions differs between muscles, depending on the physiological muscle compositions and functions of the contracting muscle.

  7. The Generalized Hill Model: A Kinematic Approach Towards Active Muscle Contraction

    PubMed Central

    Menzel, Andreas; Kuhl, Ellen

    2014-01-01

    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. PMID:25221354

  8. 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.

  9. 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.

  10. Phospholipase D1 is involved in α1-adrenergic contraction of murine vascular smooth muscle.

    PubMed

    Wegener, Jörg W; Loga, Florian; Stegner, David; Nieswandt, Bernhard; Hofmann, Franz

    2014-03-01

    α1-Adrenergic stimulation increases blood vessel tone in mammals. This process involves a number of intracellular signaling pathways that include signaling via phospholipase C, diacylglycerol (DAG), and protein kinase C. So far, it is not certain whether signaling via phospholipase D (PLD) and PLD-derived DAG is involved in this process. We asked whether PLD participates in the α1-adrenergic-mediated signaling in vascular smooth muscle. α1-Adrenergic-induced contraction was assessed by myography of isolated aortic rings and by pressure recordings using the hindlimb perfusion model in mice. The effects of the PLD inhibitor 1-butanol (IC50 0.15 vol%) and the inactive congener 2-butanol were comparatively studied. Inhibition of PLD by 1-butanol reduced specifically the α1-adrenergic-induced contraction and the α1-adrenergic-induced pressure increase by 10 and 40% of the maximum, respectively. 1-Butanol did not influence the aortic contractions induced by high extracellular potassium, by the thromboxane analog U46619, or by a phorbol ester. The effects of 1-butanol were absent in mice that lack PLD1 (Pld1(-/-) mice) or that selectively lack the CaV1.2 channel in smooth muscle (sm-CaV1.2(-/-) mice) but still present in the heterozygous control mice. α1-Adrenergic contraction of vascular smooth muscle involves activation of PLD1, which controls a portion of the α1-adrenergic-induced CaV1.2 channel activity.

  11. Muscle co-contraction around the knee when walking with unstable shoes.

    PubMed

    Horsak, Brian; Heller, Mario; Baca, Arnold

    2015-02-01

    Walking with unstable shoes has been discussed to decrease joint loading. Typical estimates of joint loading using an inverse dynamic approach only account for net joint moments, not considering the potential role of muscular co-contraction. Therefore, the purpose of this study was to compare muscular co-contraction levels when walking with two different unstable shoe constructions (rocker-bottom and toning shoes) compared to walking with regular shoes. For each shoe condition, 12 healthy subjects walked with both, a regular shoe and with an unstable shoe at self-selected walking speed at a 10-m walkway. Surface EMG data of selected muscles were recorded and time normalized for calculating co-contraction indices (CCI) for opposing muscle groups. Results showed an increase of co-contraction primarily for vastii and gastrocnemius muscles for the first and second half of stance when walking with an unstable shoe construction. Therefore, when using an inverse dynamic approach to analyze joint loading differences between regular shoes and unstable shoes, one should be cautious in interpreting the data, as these methods base their estimates of joint moments upon the net joint torque.

  12. Effects of S1P on skeletal muscle repair/regeneration during eccentric contraction.

    PubMed

    Sassoli, Chiara; Formigli, Lucia; Bini, Francesca; Tani, Alessia; Squecco, Roberta; Battistini, Chiara; Zecchi-Orlandini, Sandra; Francini, Fabio; Meacci, Elisabetta

    2011-11-01

    Skeletal muscle regeneration is severely compromised in the case of extended damage. The current challenge is to find factors capable of limiting muscle degeneration and/or potentiating the inherent regenerative program mediated by a specific type of myoblastic cells, the satellite cells. Recent studies from our groups and others have shown that the bioactive lipid, sphingosine 1-phosphate (S1P), promotes myoblast differentiation and exerts a trophic action on denervated skeletal muscle fibres. In the present study, we examined the effects of S1P on eccentric contraction (EC)-injured extensor digitorum longus muscle fibres and resident satellite cells. After EC, skeletal muscle showed evidence of structural and biochemical damage along with significant electrophysiological changes, i.e. reduced plasma membrane resistance and resting membrane potential and altered Na(+) and Ca(2+) current amplitude and kinetics. Treatment with exogenous S1P attenuated the EC-induced tissue damage, protecting skeletal muscle fibre from apoptosis, preserving satellite cell viability and affecting extracellular matrix remodelling, through the up-regulation of matrix metalloproteinase 9 (MMP-9) expression. S1P also promoted satellite cell renewal and differentiation in the damaged muscle. Notably, EC was associated with the activation of sphingosine kinase 1 (SphK1) and with increased endogenous S1P synthesis, further stressing the relevance of S1P in skeletal muscle protection and repair/regeneration. In line with this, the treatment with a selective SphK1 inhibitor during EC, caused an exacerbation of the muscle damage and attenuated MMP-9 expression. Together, these findings are in favour for a role of S1P in skeletal muscle healing and offer new clues for the identification of novel therapeutic approaches to counteract skeletal muscle damage and disease.

  13. Antibodies probe for folded monomeric myosin in relaxed and contracted smooth muscle.

    PubMed

    Horowitz, A; Trybus, K M; Bowman, D S; Fay, F S

    1994-09-01

    Regulatory light chain phosphorylation is required for assembly of smooth and non-muscle myosins in vitro, but its effect on polymerization within the cell is not understood. Relaxed smooth muscle cells contain dephosphorylated thick filaments, but this does not exclude the presence of a pool of folded myosin monomers which could be recruited to assemble when phosphorylated, thus forming part of smooth muscle's activation pathway. To test this hypothesis, relaxed and contracted avian gizzard cryosections were labeled with a fluorescently conjugated monoclonal antibody specific for the folded monomeric conformation, or with an antibody against the tip of the tail whose epitope is accessible in the monomeric but not the filamentous state. Fluorescence intensity observed in the two physiological states was quantitated by digital imaging microscopy. Only trace amounts of folded monomeric myosin were detected in both the relaxed and contracted states. The amount of monomer also did not increase when alpha-toxin permeabilized gizzard was equilibrated in a solvent that disassembles filaments in vitro. Assembly/disassembly is therefore unlikely to play a major role in regulating the contraction/relaxation cycle in smooth muscle cells.

  14. 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.

  15. A theory on auto-oscillation and contraction in striated muscle.

    PubMed

    Sato, Katsuhiko; Ohtaki, Masako; Shimamoto, Yuta; Ishiwata, Shin'ichi

    2011-05-01

    It is widely accepted that muscle cells take either force-generating or relaxing state in an all-or-none fashion through the so-called excitation-contraction coupling. On the other hand, the membrane-less contractile apparatus takes the third state, i.e., the auto-oscillation (SPOC) state, at the activation level that is intermediate between full activation and relaxation. Here, to explain the dynamics of all three states of muscle, we construct a novel theoretical model based on the balance of forces not only parallel but also perpendicular to the long axis of myofibrils, taking into account the experimental fact that the spacing of myofilament lattice changes with sarcomere length and upon contraction. This theory presents a phase diagram composed of several states of the contractile apparatus and explains the dynamic behavior of SPOC, e.g., periodical changes in sarcomere length with the saw-tooth waveform. The appropriate selection of the constant of the molecular friction due to the cross-bridge formation can explain the difference in the SPOC periods observed under various activating conditions and in different muscle types, i.e., skeletal and cardiac. The theory also predicts the existence of a weak oscillation state at the boundary between SPOC and relaxation regions in the phase diagram. Thus, the present theory comprehensively explains the characteristics of auto-oscillation and contraction in the contractile system of striated muscle.

  16. A Magnetic Resonance-Compatible Loading Device for Dynamically Imaging Shortening and Lengthening Muscle Contraction Mechanics

    PubMed Central

    Silder, Amy; Westphal, Christopher J.; Thelen, Darryl G.

    2013-01-01

    The purpose of this study was to design and test a magnetic resonance (MR)-compatible device to induce either shortening or lengthening muscle contractions for use during dynamic MR imaging. The proposed device guides the knee through cyclic flexion-extension, while either elastic or inertial loads are imposed on the hamstrings. Ten subjects were tested in a motion capture laboratory to evaluate the repeatability of limb motion and imposed loads. Image data were subsequently obtained for all ten subjects using cine phase contrast imaging. Subjects achieved ~30 deg of knee joint motion, with individual subjects remaining within ~1 deg of their average motion across 56 repeated cycles. The maximum hamstring activity and loading occurred when the knee was flexed for the elastic loading condition (shortening contraction), and extended for the inertial loading condition (lengthening contraction). Repeat MR image acquisitions of the same loading condition resulted in similar tissue velocities, while spatial variations in velocity data were clearly different between loading conditions. The proposed device can enable dynamic imaging of the muscle under different types of loads, which has the potential to improve our understanding of basic muscle mechanics, identify potential causes of muscle injury, and provide a basis for quantitatively assessing injury effects at the tissue level. Slight modifications to the device design and/or subject positioning could allow for imaging of the quadriceps or the knee. PMID:24353749

  17. Pharyngeal muscle contraction modifies peri-pharyngeal tissue pressure in rabbits.

    PubMed

    Kairaitis, Kristina; Verma, Manisha; Fish, Victoria; Wheatley, John R; Amis, Terence C

    2009-04-30

    We examined the influence of pharyngeal dilator muscle activity on upper airway extraluminal tissue pressure (ETP) distribution and upper airway patency. We studied seven anaesthetised, supine, spontaneously breathing NZ white rabbits. ETP was measured via pressure transducer tipped catheters in lateral (ETP(lat)) and anterior (ETP(ant)) pharyngeal wall tissues. Airflow (V) and tracheal pressure (P) were monitored and upper airway resistance (RUA) calculated. Genioglossus (GG) or bilateral sternohyoid (SH) muscles were electrically stimulated. Tongue protrusion (TP) during GG stimulation was measured. With GG stimulation, RUA decreased to 57.8+/-10.9% (mean+/-S.E.M.) of baseline and TP increased to 4.8+/-0.5mm (both p<0.05), but ETP(lat) (2.6+/-1.5 cm H(2)O) and ETP(ant) (1.4+/-0.8 cm H(2)O) were unchanged. SH stimulation reduced RUA to 53.6+/-6.8%, and ETP(lat) fell by 1.0+/-0.4 cm H(2)O (both p<0.05). ETP(ant) was unchanged. GG muscle contraction decreased RUA without altering ETP, whereas SH contraction altered RUA and ETP(lat), but not ETP(ant). Contraction of the upper airway dilator muscles results in improvements in upper airway patency associated with changes in peri-pharyngeal tissue pressure.

  18. 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.

  19. Enhancement of Skeletal Muscle in Aged Rats Following High-Intensity Stretch-Shortening Contraction Training.

    PubMed

    Rader, Erik P; Naimo, Marshall A; Layner, Kayla N; Triscuit, Alyssa M; Chetlin, Robert D; Ensey, James; Baker, Brent A

    2016-08-03

    Exercise is the most accessible, efficacious, and multifactorial intervention to improve health and treat chronic disease. High-intensity resistance exercise, in particular, also maximizes skeletal muscle size and strength-outcomes crucial at advanced age. However, such training is capable of inducing muscle maladaptation when misapplied at old age. Therefore, characterization of parameters (e.g., mode and frequency) that foster adaptation is an active research area. To address this issue, we utilized a rodent model that allowed training at maximal intensity in terms of muscle activation and tested the hypothesis that muscles of old rats adapt to stretch-shortening contraction (SSC) training, provided the training frequency is sufficiently low. At termination of training, normalized muscle mass (i.e., muscle mass divided by tibia length) and muscle quality (isometric force divided by normalized muscle mass) were determined. For young rats, normalized muscle mass increased by ∼20% regardless of training frequency. No difference was observed for muscle quality values after 2 days versus 3 days per week training (0.65 ± 0.09 N/mg/mm vs. 0.59 ± 0.05 N/mg/mm, respectively). For old rats following 3 days per week training, normalized muscle mass was unaltered and muscle quality was 30% lower than young levels. Following 2 days per week training at old age, normalized muscle mass increased by 17% and muscle quality was restored to young levels. To investigate this enhanced response, oxidative stress was assessed by lipid peroxidation quantification. For young rats, lipid peroxidation levels were unaltered by training. With aging, baseline levels of lipid peroxidation increased by 1.5-fold. For old rats, only 2 days per week training decreased lipid peroxidation to levels indistinguishable from young values. These results imply that, appropriately scheduled high-intensity SSC training at old age is capable of restoring muscle to a younger phenotype in terms

  20. Structural features of cross-bridges in isometrically contracting skeletal muscle.

    PubMed

    Kraft, Theresia; Mattei, Thomas; Radocaj, Ante; Piep, Birgit; Nocula, Christoph; Furch, Markus; Brenner, Bernhard

    2002-05-01

    Two-dimensional x-ray diffraction was used to investigate structural features of cross-bridges that generate force in isometrically contracting skeletal muscle. Diffraction patterns were recorded from arrays of single, chemically skinned rabbit psoas muscle fibers during isometric force generation, under relaxation, and in rigor. In isometric contraction, a rather prominent intensification of the actin layer lines at 5.9 and 5.1 nm and of the first actin layer line at 37 nm was found compared with those under relaxing conditions. Surprisingly, during isometric contraction, the intensity profile of the 5.9-nm actin layer line was shifted toward the meridian, but the resulting intensity profile was different from that observed in rigor. We particularly addressed the question whether the differences seen between rigor and active contraction might be due to a rigor-like configuration of both myosin heads in the absence of nucleotide (rigor), whereas during active contraction only one head of each myosin molecule is in a rigor-like configuration and the second head is weakly bound. To investigate this question, we created different mixtures of weak binding myosin heads and rigor-like actomyosin complexes by titrating MgATPgammaS at saturating [Ca2+] into arrays of single muscle fibers. The resulting diffraction patterns were different in several respects from patterns recorded under isometric contraction, particularly in the intensity distribution along the 5.9-nm actin layer line. This result indicates that cross-bridges present during isometric force generation are not simply a mixture of weakly bound and single-headed rigor-like complexes but are rather distinctly different from the rigor-like cross-bridge. Experiments with myosin-S1 and truncated S1 (motor domain) support the idea that for a force generating cross-bridge, disorder due to elastic distortion might involve a larger part of the myosin head than for a nucleotide free, rigor cross-bridge.

  1. A multiscale chemo-electro-mechanical skeletal muscle model to analyze muscle contraction and force generation for different muscle fiber arrangements

    PubMed Central

    Heidlauf, Thomas; Röhrle, Oliver

    2014-01-01

    The presented chemo-electro-mechanical skeletal muscle model relies on a continuum-mechanical formulation describing the muscle's deformation and force generation on the macroscopic muscle level. Unlike other three-dimensional models, the description of the activation-induced behavior of the mechanical model is entirely based on chemo-electro-mechanical principles on the microscopic sarcomere level. Yet, the multiscale model reproduces key characteristics of skeletal muscles such as experimental force-length and force-velocity data on the macroscopic whole muscle level. The paper presents the methodological approaches required to obtain such a multiscale model, and demonstrates the feasibility of using such a model to analyze differences in the mechanical behavior of parallel-fibered muscles, in which the muscle fibers either span the entire length of the fascicles or terminate intrafascicularly. The presented results reveal that muscles, in which the fibers span the entire length of the fascicles, show lower peak forces, more dispersed twitches and fusion of twitches at lower stimulation frequencies. In detail, the model predicted twitch rise times of 38.2 and 17.2 ms for a 12 cm long muscle, in which the fibers span the entire length of the fascicles and with twelve fiber compartments in series, respectively. Further, the twelve-compartment model predicted peak twitch forces that were 19% higher than in the single-compartment model. The analysis of sarcomere lengths during fixed-end single twitch contractions at optimal length predicts rather small sarcomere length changes. The observed lengths range from 75 to 111% of the optimal sarcomere length, which corresponds to a region with maximum filament overlap. This result suggests that stability issues resulting from activation-induced stretches of non-activated sarcomeres are unlikely in muscles with passive forces appearing at short muscle length. PMID:25566094

  2. 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

  3. High-frequency irreversible electroporation (H-FIRE) for non-thermal ablation without muscle contraction

    PubMed Central

    2011-01-01

    Background Therapeutic irreversible electroporation (IRE) is an emerging technology for the non-thermal ablation of tumors. The technique involves delivering a series of unipolar electric pulses to permanently destabilize the plasma membrane of cancer cells through an increase in transmembrane potential, which leads to the development of a tissue lesion. Clinically, IRE requires the administration of paralytic agents to prevent muscle contractions during treatment that are associated with the delivery of electric pulses. This study shows that by applying high-frequency, bipolar bursts, muscle contractions can be eliminated during IRE without compromising the non-thermal mechanism of cell death. Methods A combination of analytical, numerical, and experimental techniques were performed to investigate high-frequency irreversible electroporation (H-FIRE). A theoretical model for determining transmembrane potential in response to arbitrary electric fields was used to identify optimal burst frequencies and amplitudes for in vivo treatments. A finite element model for predicting thermal damage based on the electric field distribution was used to design non-thermal protocols for in vivo experiments. H-FIRE was applied to the brain of rats, and muscle contractions were quantified via accelerometers placed at the cervicothoracic junction. MRI and histological evaluation was performed post-operatively to assess ablation. Results No visual or tactile evidence of muscle contraction was seen during H-FIRE at 250 kHz or 500 kHz, while all IRE protocols resulted in detectable muscle contractions at the cervicothoracic junction. H-FIRE produced ablative lesions in brain tissue that were characteristic in cellular morphology of non-thermal IRE treatments. Specifically, there was complete uniformity of tissue death within targeted areas, and a sharp transition zone was present between lesioned and normal brain. Conclusions H-FIRE is a feasible technique for non-thermal tissue

  4. Effects of tetracaine on displacement currents and contraction of frog skeletal muscle.

    PubMed Central

    Almers, W; Best, P M

    1976-01-01

    The kinetics of mechanical activation of intact fibres were examined with a voltage-clamp technique. Tetracaine (2 mM) increases fifteen- to seventyfold the time required to produce a just visible contraction by cell membrane depolarization. 2. Displacement currents thought to be related to contractile activation remain in 2 mM tetracaine. Their characteristics are virtually identical to those found in the absence of the drug. Displacement currents also remain in fibres immobilized by treatment with 10 mM formaldehyde. 3. Despite its effect on contraction of intact fibres, tetracaine does not diminish contraction tension when Ca is applied directly to the contractile proteins of 'skinned' muscle fibres. The sensitivity of the myofilaments to Ca2+ also remains undiminished. 4. When acting on intact fibres the drug must therefore inhibit Ca2+-release from the sarcoplasmic reticulum. It is estimated that 2 mM tetracaine diminishes more than tenfold the capacity for Ca2+-release in response to cell membrane depolarization.5. If muscle displacement currents represent events linking depolarization to Ca2+-release, then tetracaine must be able to block the release without affecting the potential-sensing portion of the release regulating mechanism. 6. Further experiments on skinned fibres show that tetracaine blocks or greatly diminishes caffeine contractions, but that Cl-induced contractions of normal amplitude are still possible. PMID:1087641

  5. The Mode of Transverse Spread of Contraction Initiated by Local Activation in Single Crayfish Muscle Fibers

    PubMed Central

    Sugi, Haruo; Ochi, Rikuo

    1967-01-01

    Isolated single crayfish muscle fibers were locally activated by applying negative current pulses to a pipette whose tip was in contact with the fiber surface. The contraction initiated by a moderate depolarization spread inwards in a graded manner according to the magnitude and duration of depolarization. Increase of the depolarized area increased the distance of the inward spread for a given amount of depolarization. If a large area of the surface membrane was depolarized with a large pipette for a sufficiently long time, the contraction spread not only inwards, but further transversely passing through the center of the fiber. Successive brief depolarizations given at an appropriate interval could produce contraction more effectively for a given amount of total current than did a prolonged depolarization. On the other hand, the contraction initiated by a strong negative current was observed to spread around the whole perimeter but not through the center of the fiber. Each type of local contraction always spread along the striation pattern and not longitudinally. Possible mechanisms of these responses are discussed in connection with the transverse tubular system of the muscle fibers. PMID:19873574

  6. Effectiveness of daily eccentric contractions induced via kilohertz frequency transcutaneous electrical stimulation on muscle atrophy.

    PubMed

    Tanaka, Minoru; Nakanishi, Ryosuke; Murakami, Shinichiro; Fujita, Naoto; Kondo, Hiroyo; Ishihara, Akihiko; Roy, Roland R; Fujino, Hidemi

    2016-01-01

    The effects of daily repeated bouts of concentric, isometric, or eccentric contractions induced by high frequency (kilohertz) transcutaneous electrical stimulation in ameliorating atrophy of the soleus muscle in hindlimb unloaded rats were determined. Five groups of male rats were studied: control, hindlimb unloaded for 2 weeks (HU), or HU plus two daily bouts of concentric, isometric, or eccentric high-frequency electrical stimulation-induced contractions of the calf musculature. Soleus mass and fiber size were smaller, the levels of phosphorylated Akt1 and FoxO3a lower, and atrogin-1 and ubiquitinated proteins higher in the HU, and the HU plus concentric or isometric contraction groups than in the control group. In contrast, daily bouts of eccentric contractions maintained these values at near control levels and all measures were significantly different from all other HU groups. These results indicate that daily bouts of eccentric contractions induced by high-frequency stimulation inhibited the ubiquitin-proteasome catabolic pathway and enhanced the Akt1/FoxO3a anabolic pathway that resulted in a prevention of the atrophic response of the soleus muscle to chronic unloading.

  7. Which type of repetitive muscle contractions induces a greater acute impairment of position sense?

    PubMed

    Fortier, Sylvie; Basset, Fabien A; Billaut, François; Behm, David; Teasdale, Normand

    2010-04-01

    The objective of this study was to determine which type of repetitive muscle contractions induces a greater acute impairment of elbow position sense. Eleven male subjects participating in the study underwent (i) an exercise task (ET) consisting of 9 sets of 10 voluntary isometric, concentric, or eccentric contractions randomly performed on three separate sessions, and (ii) a pre- and post-exercise maximal voluntary isometric contraction (iMVC). Prior to and between sets of ET, a proprioception task (PT) consisting of matching the right arm to the left reference arm was performed at three different target angular positions (70 degrees , 110 degrees and 150 degrees). Each ET was immediately followed by 3 PT and 1 min rest. The statistical analysis revealed that post-exercise iMVCs were significantly decreased compared to pre-exercise iMVC in all conditions with a greater drop following the eccentric task. Despite this greater drop, position sense was significantly affected by the concentric exercise task. In addition, the spectral EMG signals significantly shifted towards lower frequencies from the initial values, regardless of exercise task. The results showed that concentric muscle contractions impaired position sense to a greater extent compared to isometric and eccentric contractions.

  8. Effect of the Mandibular Orthopedic Repositioning Appliance on Trunk and Upper Limb Muscle Activation during Maximum Isometric Contraction.

    PubMed

    Lee, Sang-Yeol; Hong, Min-Ho; Park, Min-Chull; Choi, Sung-Min

    2013-11-01

    [Purpose] The purpose of this study was to measure the muscle activities of the trunk muscles and upper limb muscles during maximum isometric contraction when temporomandibular joint alignment was achieved with a mandibular orthopedic repositioning appliance in order provide basic data on the effects of mandibular orthopedic repositioning appliance on the entire body. [Subjects] The present study was conducted with healthy Korean adults in their 20s (males=10, females=10). [Methods] An 8 channel surface electromyography system was used to measure the muscle activities of the upper limb muscles and neck muscles of the subjects during maximum isometric contraction with and without use of a mandibular orthopedic repositioning appliance. [Results] The maximum isometric contractions of the trunk and upper limb muscles when mandibular orthopedic repositioning appliance were used were compared with those when no mandibular orthopedic repositioning appliance was used. The results showed that the sternocleidomastoid muscle, cervical and lumbar erector spinae, upper trapezius, biceps, triceps, rectus abdominis and internal oblique and external oblique muscles all showed significant increases in maximum isometric contractions with a mandibular orthopedic repositioning appliance. [Conclusion] The use of a mandibular orthopedic repositioning appliance is considered to be a method for normal adults to improve the stability of the entire body with the improvement of the stability of the TMJ. The proximal improvement in stability improves of the proximal thereby improving not only muscle strength with increased muscle activation but also stability during exercises.

  9. 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.

  10. Ultrasound-Derived Abdominal Muscle Thickness Better Detects Metabolic Syndrome Risk in Obese Patients than Skeletal Muscle Index Measured by Dual-Energy X-Ray Absorptiometry

    PubMed Central

    Ido, Ayumi; Nakayama, Yuki; Ishii, Kojiro; Iemitsu, Motoyuki; Sato, Koji; Fujimoto, Masahiro; Kurihara, Toshiyuki; Hamaoka, Takafumi; Satoh-Asahara, Noriko; Sanada, Kiyoshi

    2015-01-01

    Sarcopenia has never been diagnosed based on site-specific muscle loss, and little is known about the relationship between site-specific muscle loss and metabolic syndrome (MetS) risk factors. To this end, this cross-sectional study aimed to investigate the relationship between site-specific muscle size and MetS risk factors. Subjects were 38 obese men and women aged 40–82 years. Total body fat and lean body mass were assessed by whole-body dual-energy X-ray absorptiometry (DXA) scan. Muscle thickness (MTH) was measured using B-mode ultrasound scanning in six body regions. Subjects were classified into general obesity (GO) and sarcopenic obesity (SO) groups using the threshold values of one standard deviation below the sex-specific means of either MTH or skeletal muscle index (SMI) measured by DXA. MetS risk score was acquired by standardizing and summing the following continuously distributed variables: visceral fat area, mean blood pressure, HbA1c, and serum triglyceride / high density lipoprotein cholesterol, to obtain the Z-score. Multiple regression analysis revealed that the MetS risk score was independently associated with abdominal MTH in all subjects, but not with MTH in other muscle regions, including the thigh. Although HbA1c and the number of MetS risk factors in the SO group were significantly higher than those in the GO group, there were no significant differences between GO and SO groups as defined by SMI. Ultrasound-derived abdominal MTH would allow a better assessment of sarcopenia in obese patients and can be used as an alternative to the conventionally-used SMI measured by DXA. PMID:26700167

  11. Can inorganic phosphate explain sag during unfused tetanic contractions of skeletal muscle?

    PubMed

    Smith, Ian C; Bellissimo, Catherine; Herzog, Walter; Tupling, A Russell

    2016-11-01

    We test the hypothesis that cytosolic inorganic phosphate (Pi) can account for the contraction-induced reductions in twitch duration which impair summation and cause force to decline (sag) during unfused tetanic contractions of fast-twitch muscle. A five-state model of crossbridge cycling was used to simulate twitch and unfused tetanic contractions. As Pi concentration ([Pi]) was increased from 0 to 30 mmol·L(-1), twitch duration decreased, with progressive reductions in sensitivity to Pi as [Pi] was increased. When unfused tetani were simulated with rising [Pi], sag was most pronounced when initial [Pi] was low, and when the magnitude of [Pi] increase was large. Fast-twitch extensor digitorum longus (EDL) muscles (sag-prone, typically low basal [Pi]) and slow-twitch soleus muscles (sag-resistant, typically high basal [Pi]) were isolated from 14 female C57BL/6 mice. Muscles were sequentially incubated in solutions containing either glucose or pyruvate to create typical and low Pi environments, respectively. Twitch duration was greater (P < 0.05) in pyruvate than glucose in both muscles. Stimuli applied at intervals approximately three times the time to peak twitch tension resulted in sag of 35.0 ± 3.7% in glucose and 50.5 ± 1.4% in pyruvate in the EDL (pyruvate > glucose; P < 0.05), and 3.9 ± 0.3% in glucose and 37.8 ± 2.7% in pyruvate in the soleus (pyruvate > glucose; P < 0.05). The influence of Pi on crossbridge cycling provides a tenable mechanism for sag. Moreover, the low basal [Pi] in fast-twitch relative to slow-twitch muscle has promise as an explanation for the fiber-type dependency of sag.

  12. A novel three-filament model of force generation in eccentric contraction of skeletal muscles.

    PubMed

    Schappacher-Tilp, Gudrun; Leonard, Timothy; Desch, Gertrud; Herzog, Walter

    2015-01-01

    We propose and examine a three filament model of skeletal muscle force generation, thereby extending classical cross-bridge models by involving titin-actin interaction upon active force production. In regions with optimal actin-myosin overlap, the model does not alter energy and force predictions of cross-bridge models for isometric contractions. However, in contrast to cross-bridge models, the three filament model accurately predicts history-dependent force generation in half sarcomeres for eccentric and concentric contractions, and predicts the activation-dependent forces for stretches beyond actin-myosin filament overlap.

  13. Effects of adenosine triphosphate concentration on motor force regulation during skeletal muscle contraction

    NASA Astrophysics Data System (ADS)

    Wei, J.; Dong, C.; Chen, B.

    2017-03-01

    We employ a mechanical model of sarcomere to quantitatively investigate how adenosine triphosphate (ATP) concentration affects motor force regulation during skeletal muscle contraction. Our simulation indicates that there can be negative cross-bridges resisting contraction within the sarcomere and higher ATP concentration would decrease the resistance force from negative cross-bridges by promoting their timely detachment. It is revealed that the motor force is well regulated only when ATP concentration is above a certain level. These predictions may provide insights into the role of ATP in regulating coordination among multiple motors.

  14. Elastic bending and active tilting of myosin heads during muscle contraction.

    PubMed

    Dobbie, I; Linari, M; Piazzesi, G; Reconditi, M; Koubassova, N; Ferenczi, M A; Lombardi, V; Irving, M

    1998-11-26

    Muscle contraction is driven by a change in shape of the myosin head region that links the actin and myosin filaments. Tilting of the light-chain domain of the head with respect to its actin-bound catalytic domain is thought to be coupled to the ATPase cycle. Here, using X-ray diffraction and mechanical data from isolated muscle fibres, we characterize an elastic bending of the heads that is independent of the presence of ATP. Together, the tilting and bending motions can explain force generation in isometric muscle, when filament sliding is prevented. The elastic strain in the head is 2.0-2.7 nm under these conditions, contributing 40-50% of the compliance of the muscle sarcomere. We present an atomic model for changes in head conformation that accurately reproduces the changes in the X-ray diffraction pattern seen when rapid length changes are applied to muscle fibres both in active contraction and in the absence of ATP. The model predictions are relatively independent of which parts of the head are assumed to bend or tilt, but depend critically on the measured values of filament sliding and elastic strain.

  15. Effects of contraction intensity on muscle fascicle and stretch reflex behavior in the human triceps surae.

    PubMed

    Cronin, Neil J; Peltonen, Jussi; Ishikawa, Masaki; Komi, Paavo V; Avela, Janne; Sinkjaer, Thomas; Voigt, Michael

    2008-07-01

    The aims of this study were to examine changes in the distribution of a stretch to the muscle fascicles with changes in contraction intensity in the human triceps surae and to relate fascicle stretch responses to short-latency stretch reflex behavior. Thirteen healthy subjects were seated in an ankle ergometer, and dorsiflexion stretches (8 degrees ; 250 degrees /s) were applied to the triceps surae at different moment levels (0-100% of maximal voluntary contraction). Surface EMG was recorded in the medial gastrocnemius, soleus, and tibialis anterior muscles, and ultrasound was used to measure medial gastrocnemius and soleus fascicle lengths. At low forces, reflex amplitudes increased despite a lack of change or even a decrease in fascicle stretch velocities. At high forces, lower fascicle stretch velocities coincided with smaller stretch reflexes. The results revealed a decline in fascicle stretch velocity of over 50% between passive conditions and maximal force levels in the major muscles of the triceps surae. This is likely to be an important factor related to the decline in stretch reflex amplitudes at high forces. Because short-latency stretch reflexes contribute to force production and stiffness regulation of human muscle fibers, a reduction in afferent feedback from muscle spindles could decrease the efficacy of human movements involving the triceps surae, particularly where high force production is required.

  16. Voluntary activation level and muscle fiber recruitment of human quadriceps during lengthening contractions.

    PubMed

    Beltman, J G M; Sargeant, A J; van Mechelen, W; de Haan, A

    2004-08-01

    Voluntary activation levels during lengthening, isometric, and shortening contractions (angular velocity 60 degrees/s) were investigated by using electrical stimulation of the femoral nerve (triplet, 300 Hz) superimposed on maximal efforts. Recruitment of fiber populations was investigated by using the phosphocreatine-to-creatine ratio (PCr/Cr) of single characterized muscle fibers obtained from needle biopsies at rest and immediately after a series of 10 lengthening, isometric, and shortening contractions (1 s on/1 s off). Maximal voluntary torque was significantly higher during lengthening (270 +/- 55 N.m) compared with shortening contractions (199 +/- 47 N.m, P < 0.05) but was not different from isometric contractions (252 +/- 47 N.m). Isometric torque was higher than torque during shortening (P < 0.05). Voluntary activation level during maximal attempted lengthening contractions (79 +/- 8%) was significantly lower compared with isometric (93 +/- 5%) and shortening contractions (92 +/- 3%, P < 0.05). Mean PCr/Cr values of all fibers from all subjects at rest were 2.5 +/- 0.6, 2.0 +/- 0.7, and 2.0 +/- 0.7, respectively, for type I, IIa, and IIax fibers. After 10 contractions, the mean PCr/Cr values for grouped fiber populations (regardless of fiber type) were all significantly different from rest (1.3 +/- 0.2, 0.7 +/- 0.3, and 0.8 +/- 0.6 for lengthening, isometric, and shortening contractions, respectively; P < 0.05). The cumulative distributions of individual fiber populations after either contraction mode were significantly different from rest (P < 0.05). Curves after lengthening contractions were less shifted compared with curves from isometric and shortening contractions (P < 0.05), with a smaller shift for the type IIax compared with type I fibers in the lengthening contractions. The results indicate a reduced voluntary drive during lengthening contractions. PCr/Cr values of single fibers indicated a hierarchical order of recruitment of all fiber

  17. Middle ear muscle contractions and their relation to pulse and echo evoked potentials in the bat

    NASA Technical Reports Server (NTRS)

    Henson, O. W., Jr.; Henson, M. M.

    1972-01-01

    An analysis is made of pulse and echo orientation cries of the Mustache Bat. That bat's cries are characterized by a long, 60 to 30 msec, pure tone component and brief beginning and terminal FM sweeps. In addition to obvious echo overlap and middle ear muscle contractions, the following are examined: (1) characteristics of pulse- and echo-evoked potential under various conditions, (2) evidence of changes in hearing sensitivity during and after pulse emission, and (3) the role of the middle ear muscles in bringing about these changes.

  18. Blood flow restriction prevents muscle damage but not protein synthesis signaling following eccentric contractions

    PubMed Central

    Sudo, Mizuki; Ando, Soichi; Poole, David C; Kano, Yutaka

    2015-01-01

    There is a growing body of evidence to suggest that resistance training exercise combined with blood flow restriction (BFR) increases muscle size and strength in humans. Eccentric contraction (ECC) frequently induces severe muscle damage. However, it is not known whether and to what extent muscle damage occurs following ECC + BFR due to the difficulty of conducting definitive invasive studies. The purpose of this study was to examine muscle fiber damage following ECC + BFR at the cellular level. High-intensity ECC was purposefully selected to maximize the opportunity for muscle damage and hypertrophic signaling in our novel in vivo animal model. Male Wistar rats were assigned randomly to the following groups: ECC and ECC + BFR at varying levels of occlusion pressure (140, 160, and 200 Torr). In all conditions, electrical stimulation was applied to the dorsiflexor muscles simultaneously with electromotor-induced plantar flexion. We observed severe histochemical muscle fiber damage (area of damaged fibers/total fiber area analyzed) following ECC (26.4 ± 4.0%). Surprisingly, however, muscle damage was negligible following ECC + BFR140 (2.6 ± 1.2%), ECC+BFR160 (3.0 ± 0.5%), and ECC + BFR200 (0.2 ± 0.1%). Ribosomal S6 kinase 1 (S6K1) phosphorylation, a downstream target of rapamycin (mTOR)-phosphorylation kinase, increased following ECC + BFR200 as well as ECC. In contrast, S6K1 phosphorylation was not altered by BFR alone. The present findings suggest that ECC combined with BFR, even at high exercise intensities, may enhance muscle protein synthesis without appreciable muscle fiber damage. PMID:26149281

  19. Use-dependence of ryanodine effects on postrest contraction in ferret cardiac muscle.

    PubMed

    Malecot, C O; Katzung, B G

    1987-04-01

    During an investigation of the effect of ryanodine on contractions in cardiac muscle, it was found that long rest periods removed all or most of the drug's effect. Therefore, we studied the kinetics of block development and recovery from block produced by low concentrations of ryanodine (1-100 pM) on the postrest contractions of ferret papillary muscle. At 100 pM, ryanodine depressed steady-state contraction amplitude slightly (4.2 +/- 1.1% mean +/- SEM, n = 10) but strongly inhibited (40-80%) the first contraction (postrest contraction) elicited on restimulation of the preparation after rest periods of 1 second to 5 minutes. Under control conditions, the nearly maximal potentiation of the twitch occurring after a standard test rest period (30 seconds of rest) was not affected by a preceding conditioning rest of up to 20 minutes. In the presence of 100 pM ryanodine, a conditioning rest increased the amplitude of the twitch elicited after a test rest, and the test rest contraction recovered toward control (drug-free) amplitude monoexponentially (time constant, 582 +/- 105 seconds). Block of postrest contraction could be reinduced by stimulation and occurred faster when higher rates were used (time constants, 758 seconds at 1 Hz and 107 +/- 26 seconds at 3 Hz). Since rest potentiation of twitch tension is believed to be mostly dependent on extra calcium released from the sarcoplasmic reticulum, the results suggest that the ryanodine-induced blockade of calcium release from the sarcoplasmic reticulum is use-dependent and recovers during diastole.(ABSTRACT TRUNCATED AT 250 WORDS)

  20. Refined distribution of myelinated trigeminal proprioceptive nerve fibres in Mueller's muscle as the mechanoreceptors to induce involuntary reflexive contraction of the levator and frontalis muscles.

    PubMed

    Yuzuriha, Shunsuke; Matsuo, Kiyoshi; Hirasawa, Chihiro; Moriizumi, Tetsuji

    2009-11-01

    Stretching of mechanoreceptors in Mueller's muscle induces reflexive contraction of not only the levator muscle but also the frontalis muscle as two different eyelid-opening muscles. Previously, we reported that fine neural myelinated structures, acting as mechanoreceptors, were found in the proximal Mueller's muscle. Since there is a risk of misunderstanding that the middle and distal Mueller's muscle does not contain mechanoreceptors and can be invalidated or resected, the accurate distribution of myelinated trigeminal proprioceptive nerve fibres as mechanoreceptors in Mueller's muscle was refined horizontally in this study. We explored 10 whole Mueller's muscles between the levator muscle and the tarsus of the upper eyelids obtained from five Japanese cadavers. The specimens were serially sliced along the horizontal plane and stained with HE, S-100 protein to determine the presence of Schwann cells, and smooth muscle actin antibody to determine the presence of Mueller's smooth muscle fibres. Although all myelinated nerve fibres in the intermuscular connective tissues among the sympathetically innervated Mueller's multi-unit smooth muscle fibres may not correspond to the proprioceptive nerve fibres, the nerve bundles consisting of multiple myelinated nerve fibres were well distributed in the proximal Mueller's muscle, and single myelinated nerve fibres were well distributed in the middle and distal Mueller's muscle. We believe that the mechanoreceptors in Mueller's muscle consist of myelinated proprioceptive nerve fibres with nerve endings possibly attached to collagen fibres in the intermuscular connective tissues present among Mueller's smooth muscle fibres. As the myelinated nerve fibres innervate the middle and distal Mueller's muscle to a greater extent than those in the proximal Mueller's muscle, the former may be more important as mechanoreceptors than the latter and should not be invalidated or excised during surgery for treatment of blepharoptosis to

  1. Membrane Cholesterol in Skeletal Muscle: A Novel Player in Excitation-Contraction Coupling and Insulin Resistance.

    PubMed

    Barrientos, G; Sánchez-Aguilera, P; Jaimovich, E; Hidalgo, C; Llanos, P

    2017-01-01

    Membrane cholesterol is critical for signaling processes in a variety of tissues. We will address here current evidence supporting an emerging role of cholesterol on excitation-contraction coupling and glucose transport in skeletal muscle. We have centered our review on the transverse tubule system, a complex network of narrow plasma membrane invaginations that propagate membrane depolarization into the fiber interior and allow nutrient delivery into the fibers. We will discuss current evidence showing that transverse tubule membranes have remarkably high cholesterol levels and we will address how modifications of cholesterol content influence excitation-contraction coupling. In addition, we will discuss how membrane cholesterol levels affect glucose transport by modulating the insertion into the membrane of the main insulin-sensitive glucose transporter GLUT4. Finally, we will address how the increased membrane cholesterol levels displayed by obese animals, which also present insulin resistance, affect these two particular skeletal muscle functions.

  2. A circuit mechanism for the propagation of waves of muscle contraction in Drosophila.

    PubMed

    Fushiki, Akira; Zwart, Maarten F; Kohsaka, Hiroshi; Fetter, Richard D; Cardona, Albert; Nose, Akinao

    2016-02-15

    Animals move by adaptively coordinating the sequential activation of muscles. The circuit mechanisms underlying coordinated locomotion are poorly understood. Here, we report on a novel circuit for the propagation of waves of muscle contraction, using the peristaltic locomotion of Drosophila larvae as a model system. We found an intersegmental chain of synaptically connected neurons, alternating excitatory and inhibitory, necessary for wave propagation and active in phase with the wave. The excitatory neurons (A27h) are premotor and necessary only for forward locomotion, and are modulated by stretch receptors and descending inputs. The inhibitory neurons (GDL) are necessary for both forward and backward locomotion, suggestive of different yet coupled central pattern generators, and its inhibition is necessary for wave propagation. The circuit structure and functional imaging indicated that the commands to contract one segment promote the relaxation of the next segment, revealing a mechanism for wave propagation in peristaltic locomotion.

  3. Experimental basis of the hypotheses on the mechanism of skeletal muscle contraction

    PubMed Central

    Grazi, Enrico

    2011-01-01

    Summary With time clever hypotheses may be accepted as “facts” without being supported by solid experimental evidence. In our opinion this happened with muscle contraction where pure suggestions still occupy the scene and delay the progress of the research. Among these suggestions are: 1. the believe that viscosity is irrelevant in the economy of muscle contraction, 2. the concept of the drag stroke, 3. some interpretations of the significance of the Huxley-Simmons manoeuvre, 4. the definition of the load as a force/cross-section without taking into consideration the possible, divergent effects of the infinite mass x acceleration couples. Technical questions are also raised since it is apparent that measuring equipments interfere with the measure itself. PMID:23738252

  4. Effects of vibratory stimulations on maximal voluntary isometric contraction from delayed onset muscle soreness.

    PubMed

    Koh, Hyung-Woo; Cho, Sung-Hyoun; Kim, Cheol-Yong; Cho, Byung-Jun; Kim, Jin-Woo; Bo, Kak Hwang

    2013-09-01

    [Purpose] The aim of this study was to investigate the effect of vibratory stimulation on maximal voluntary isometric contraction (MVIC) from delayed onset muscle soreness (DOMS). [Subjects] Sixty healthy adults participated in this study. The exclusion criteria were orthopedic or neurologic disease. [Methods] The researchers induced DOMS in the musculus extensor carpi radialis longus of each participant. Subjects in the control group received no treatment. The ultrasound group received ultrasound treatment (intensity, 1.0 W/cm(2;) frequency 1 MHz; time, 10 minutes). The vibration group received vibration stimulation (frequency, 20 MHz; time, 10 minutes). Maximal voluntary isometric contraction (MVIC) was recorded at baseline, immediately after exercise, and 24, 48, and 72 hours after exercise. [Results] MVIC measurements showed statistically significant differences in the vibration group compared with the control group. [Conclusion] Vibratory stimulation had a positive effect on recovery of muscle function from DOMS.

  5. Effects of Vibratory Stimulations on Maximal Voluntary Isometric Contraction from Delayed Onset Muscle Soreness

    PubMed Central

    Koh, Hyung-Woo; Cho, Sung-Hyoun; Kim, Cheol-Yong; Cho, Byung-Jun; Kim, Jin-Woo; Bo, Kak Hwang

    2013-01-01

    [Purpose] The aim of this study was to investigate the effect of vibratory stimulation on maximal voluntary isometric contraction (MVIC) from delayed onset muscle soreness (DOMS). [Subjects] Sixty healthy adults participated in this study. The exclusion criteria were orthopedic or neurologic disease. [Methods] The researchers induced DOMS in the musculus extensor carpi radialis longus of each participant. Subjects in the control group received no treatment. The ultrasound group received ultrasound treatment (intensity, 1.0 W/cm2; frequency 1 MHz; time, 10 minutes). The vibration group received vibration stimulation (frequency, 20 MHz; time, 10 minutes). Maximal voluntary isometric contraction (MVIC) was recorded at baseline, immediately after exercise, and 24, 48, and 72 hours after exercise. [Results] MVIC measurements showed statistically significant differences in the vibration group compared with the control group. [Conclusion] Vibratory stimulation had a positive effect on recovery of muscle function from DOMS. PMID:24259922

  6. Membrane Cholesterol in Skeletal Muscle: A Novel Player in Excitation-Contraction Coupling and Insulin Resistance

    PubMed Central

    Barrientos, G.; Sánchez-Aguilera, P.; Jaimovich, E.; Hidalgo, C.

    2017-01-01

    Membrane cholesterol is critical for signaling processes in a variety of tissues. We will address here current evidence supporting an emerging role of cholesterol on excitation-contraction coupling and glucose transport in skeletal muscle. We have centered our review on the transverse tubule system, a complex network of narrow plasma membrane invaginations that propagate membrane depolarization into the fiber interior and allow nutrient delivery into the fibers. We will discuss current evidence showing that transverse tubule membranes have remarkably high cholesterol levels and we will address how modifications of cholesterol content influence excitation-contraction coupling. In addition, we will discuss how membrane cholesterol levels affect glucose transport by modulating the insertion into the membrane of the main insulin-sensitive glucose transporter GLUT4. Finally, we will address how the increased membrane cholesterol levels displayed by obese animals, which also present insulin resistance, affect these two particular skeletal muscle functions. PMID:28367451

  7. On Using Model Populations to Determine Mechanical Properties of Skeletal Muscle. Application to Concentric Contraction Simulation.

    PubMed

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

    2015-10-01

    In the field of computational biomechanics, the experimental evaluation of the material properties is crucial for the development of computational models that closely reproduce real organ systems. When simulations of muscle tissue are concerned, stress/strain relations for both passive and active behavior are required. These experimental relations usually exhibit certain variability. In this study, a set of material parameters involved in a 3D skeletal muscle model are determined by using a system biology approach in which the parameters are randomly varied leading to a population of models. Using a set of experimental results from an animal model, a subset of the entire population of models was selected. This reduced population predicted the mechanical response within the window of experimental observations. Hence, a range of model parameters, instead of a single set of them, was determined. Rat Tibialis Anterior muscle was selected for this study. Muscles ([Formula: see text]) were activated through the sciatic nerve and during contraction the tissue pulled a weight fixed to the distal tendon (concentric contraction). Three different weights 1, 2 and 3 N were used and the time course of muscle stretch was analyzed obtaining values of (mean [Formula: see text] standard deviation): [Formula: see text], [Formula: see text] and [Formula: see text] respectively. A paired two-sided sign rank test showed significant differences between the muscle response for the three weights ([Formula: see text]). This study shows that the Monte Carlo method could be used for determine muscle characteristic parameters considering the variability of the experimental population.

  8. The effects of modified wall squat exercises on average adults' deep abdominal muscle thickness and lumbar stability.

    PubMed

    Cho, Misuk

    2013-06-01

    [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.

  9. A muscle contracting substance from a plant's closing Fly-Trap.

    PubMed

    Lea, H W

    1976-01-01

    A muscle contracting substance (MCS) occurs in crushed, incubated traps of the insectivorous plant, the Venus Fly-Trap (Dionaea muscipula Ellis). This MCS is provisionally identified as lysophosphatidic acid. More MCS is produced from traps which have been touched than from untouched traps, which may be due to activation of phospholipase D. This enzyme hydrolyses phospholipids of membranes, and could alter the physiological properties of membranes.

  10. PKC delta-isoform translocation and enhancement of tonic contractions of gastrointestinal smooth muscle.

    PubMed

    Poole, Daniel P; Furness, John B

    2007-03-01

    PKC is involved in mediating the tonic component of gastrointestinal smooth muscle contraction in response to stimulation by agonists for G protein-coupled receptors. Here, we present pharmacological and immunohistochemical evidence indicating that a member of the novel PKC isoforms, PKC-delta, is involved in maintaining muscarinic receptor-coupled tonic contractions of the guinea pig ileum. The tonic component of carbachol-evoked contractions was enhanced by an activator of conventional and novel PKCs, phorbol 12,13-dibutyrate (PDBu; 200 nM or 1 microM), and by an activator of novel PKCs, ingenol 3,20-dibenzoate (IDB; 100 or 500 nM). Enhancement was unaffected by concentrations of bisindolylmaleimide I (BIM-I; 22 nM) that block conventional PKCs or by a PKC-epsilon-specific inhibitor peptide but was attenuated by higher doses of BIM-I (2.2 microM). Relevant proteins were localized at a cellular and subcellular level using confocal analysis. Immunohistochemical staining of the ileum showed that PKC-delta was exclusively expressed in smooth muscles distributed throughout the layers of the gut wall. PKC-epsilon immunoreactivity was prominent in enteric neurons but was largely absent from smooth muscle of the muscularis externa. Treatment with PDBu, IDB, or carbachol resulted in a time- and concentration-dependent translocation of PKC-delta from the cytoplasm to filamentous structures within smooth muscle cells. These were parallel to, but distinct from, actin filaments. The translocation of PKC-delta in response to carbachol was significantly reduced by scopolamine or calphostin C. The present study indicates that the tonic carbachol-induced contraction of the guinea pig ileum is mediated through a novel PKC, probably PKC-delta.

  11. Post-contractile BOLD contrast in skeletal muscle at 7 T reveals inter-individual heterogeneity in the physiological responses to muscle contraction.

    PubMed

    Towse, Theodore F; Elder, Christopher P; Bush, Emily C; Klockenkemper, Samuel W; Bullock, Jared T; Dortch, Richard D; Damon, Bruce M

    2016-12-01

    Muscle blood oxygenation-level dependent (BOLD) contrast is greater in magnitude and potentially more influenced by extravascular BOLD mechanisms at 7 T than it is at lower field strengths. Muscle BOLD imaging of muscle contractions at 7 T could, therefore, provide greater or different contrast than at 3 T. The purpose of this study was to evaluate the feasibility of using BOLD imaging at 7 T to assess the physiological responses to in vivo muscle contractions. Thirteen subjects (four females) performed a series of isometric contractions of the calf muscles while being scanned in a Philips Achieva 7 T human imager. Following 2 s maximal isometric plantarflexion contractions, BOLD signal transients ranging from 0.3 to 7.0% of the pre-contraction signal intensity were observed in the soleus muscle. We observed considerable inter-subject variability in both the magnitude and time course of the muscle BOLD signal. A subset of subjects (n = 7) repeated the contraction protocol at two different repetition times (TR : 1000 and 2500 ms) to determine the potential of T1 -related inflow effects on the magnitude of the post-contractile BOLD response. Consistent with previous reports, there was no difference in the magnitude of the responses for the two TR values (3.8 ± 0.9 versus 4.0 ± 0.6% for TR  = 1000 and 2500 ms, respectively; mean ± standard error). These results demonstrate that studies of the muscle BOLD responses to contractions are feasible at 7 T. Compared with studies at lower field strengths, post-contractile 7 T muscle BOLD contrast may afford greater insight into microvascular function and dysfunction.

  12. Associations between low back pain, urinary incontinence, and abdominal muscle recruitment as assessed via ultrasonography in the elderly

    PubMed Central

    Figueiredo, Vânia F.; Amorim, Juleimar S. C.; Pereira, Aline M.; Ferreira, Paulo H.; Pereira, Leani S. M.

    2015-01-01

    Background: 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. Objective: 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. Method: 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. Results: 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. Conclusion: 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. PMID:25714438

  13. Prostanoid receptors mediating contraction in rat, macaque and human bladder smooth muscle in vitro.

    PubMed

    Root, James A; Davey, Dorren A; Af Forselles, Kerry J

    2015-12-15

    Selective prostaglandin EP1 antagonists have been suggested for the treatment of bladder dysfunction. This study assessed the contractile prostanoid receptor subtypes in human and non-human bladder in vitro. Classical tissue bath studies were conducted using bladder strips exposed to prostanoid agonists and antagonists. Prostaglandin E2 (PGE2) contracted rat, macaque and human bladder smooth muscle strips (pEC50 7.91±0.06 (n=7), 6.40±0.13 (n=7), and 6.07±0.11 (n=5), respectively). The EP1 receptor antagonist, PF2907617 (300nM), caused a rightward shift of the PGE2 concentration-response curve in the rat bladder only (pKB 8.40±0.15, n=3). PGE2 responses in rat and macaque bladders, but not human, were antagonised by the EP3 antagonist CJ24979 (1µM). Sulprostone, a mixed EP1/EP3/FP receptor agonist, induced potent contractions of rat bladder muscle (pEC50 7.94±0.31, n=6). The FP receptor agonist, prostaglandin F2α (PGF2α), induced bladder contraction in all species tested, but with a lower potency in rat. The selective FP receptor agonist latanoprost caused potent contractions of macaque and human bladder strips only. SQ29548, a selective TP antagonist, and GW848687X, a mixed EP1/TP antagonist caused rightward shifts of the concentration-response curves to the selective TP agonist, U46619 (pKB estimates 8.53±0.07 and 7.56±0.06, n=3, respectively). Responses to U46619 were absent in rat preparations. These data suggest significant species differences exist in bladder contractile prostanoid receptor subtypes. We conclude that the EP1 subtype does not represent the best approach to the clinical treatment of bladder disorders targeting inhibition of smooth muscle contraction.

  14. Unaccustomed eccentric contractions impair plasma K+ regulation in the absence of changes in muscle Na+,K+-ATPase content.

    PubMed

    Goodman, Craig A; Bennie, Jason A; Leikis, Murray J; McKenna, Michael J

    2014-01-01

    The Na+,K+-ATPase (NKA) plays a fundamental role in the regulation of skeletal muscle membrane Na+ and K+ gradients, excitability and fatigue during repeated intense contractions. Many studies have investigated the effects of acute concentric exercise on K+ regulation and skeletal muscle NKA, but almost nothing is known about the effects of repeated eccentric contractions. We therefore investigated the effects of unaccustomed maximal eccentric knee extensor contractions on K+ regulation during exercise, peak knee extensor muscle torque, and vastus lateralis muscle NKA content and 3-O-MFPase activity. Torque measurements, muscle biopsies, and venous blood samples were taken before, during and up to 7 days following the contractions in six healthy adults. Eccentric contractions reduced peak isometric muscle torque immediately post-exercise by 26±11% and serum creatine kinase concentration peaked 24 h post-exercise at 339±90 IU/L. During eccentric contractions, plasma [K+] rose during Set 1 and remained elevated at ∼4.9 mM during sets 4-10; this was despite a decline in work output by Set 4, which fell by 18.9% at set 10. The rise in plasma [K+] x work(-1) ratio was elevated over Set 2 from Set 4- Set 10. Eccentric contractions had no effect on muscle NKA content or maximal in-vitro 3-O-MFPase activity immediately post- or up to 7 d post-exercise. The sustained elevation in plasma [K+] despite a decrease in work performed by the knee extensor muscles suggests an impairment in K+ regulation during maximal eccentric contractions, possibly due to increased plasma membrane permeability or to excitation-contraction uncoupling.

  15. Acute effect of muscle stretching on the steadiness of sustained submaximal contractions of the plantar flexor muscles.

    PubMed

    Kato, Emika; Vieillevoye, Stéphanie; Balestra, Costantino; Guissard, Nathalie; Duchateau, Jacques

    2011-02-01

    This paper examines the acute effect of a bout of static stretches on torque fluctuation during an isometric torque-matching task that required subjects to sustain isometric contractions as steady as possible with the plantar flexor muscles at four intensities (5, 10, 15, and 20% of maximum) for 20 s. The stretching bout comprised five 60-s passive stretches, separated by 10-s rest. During the torque-matching tasks and muscle stretching, the torque (active and passive) and surface electromyogram (EMG) of the medial gastrocnemius (MG), soleus (Sol), and tibialis anterior (TA) were continuously recorded. Concurrently, changes in muscle architecture (fascicle length and pennation angle) of the MG were monitored by ultrasonography. The results showed that during stretching, passive torque decreased and fascicle length increased gradually. Changes in these two parameters were significantly associated (r(2) = 0.46; P < 0.001). When data from the torque-matching tasks were collapsed across the four torque levels, stretches induced greater torque fluctuation (P < 0.001) and enhanced EMG activity (P < 0.05) in MG and TA muscles with no change in coactivation. Furthermore, stretching maneuvers produced a greater decrease (∼15%; P < 0.001) in fascicle length during the torque-matching tasks and change in torque fluctuation (CV) was positively associated with changes in fascicle length (r(2) = 0.56; P < 0.001), MG and TA EMG activities, and coactivation (r(2) = 0.35, 0.34, and 0.35, respectively; P < 0.001). In conclusion, these observations indicate that repeated stretches can decrease torque steadiness by increasing muscle compliance and EMG activity of muscles around the joint. The relative influence of such adaptations, however, may depend on the torque level during the torque-matching task.

  16. Mechanism of soman-induced contractions in canine tracheal smooth muscle. (Reannouncement with new availability information)

    SciTech Connect

    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 appearance 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.

  17. Esophageal mucosal mast cell infiltration and changes in segmental smooth muscle contraction in noncardiac chest pain.

    PubMed

    Park, S W; Lee, H; Lee, H J; Chung, H; Park, J C; Shin, S K; Lee, S K; Lee, Y C

    2015-01-01

    Mast cells release potent mediators that alter enteric nerve and smooth muscle functions and may contribute to the pathogenesis of functional gastrointestinal disorders. The goal of this study was to determine if mucosal mast cell infiltration was associated with smooth muscle segmental changes in esophageal contraction. All patients with noncardiac chest pain (NCCP) were divided into two groups consisting of patients with non-erosive reflux disease or functional chest pain (FCP) according to the results of ambulatory 24 hours esophageal pH monitoring and high-resolution manometry. Pressure-volume (PV) was calculated by multiplying the length of the esophageal segment, duration of the contraction, and mean pressure over the entire space-time box (P mean). Quantification of mast cells was performed in five consecutive nonoverlapping immunostained sections. Spearman correlation analysis showed that the distal segment PV correlated with the mast cell count in all of the patients combined and in patients with FCP with correlation coefficients of 0.509 and 0.436, respectively (P = 0.004 and P = 0.042). Similar findings were observed for the segmental ratio of distal to proximal smooth muscle PV in all patients and in patients with FCP (correlation coefficients 0.566; P = 0.001 and correlation coefficients 0.525; P = 0.012, respectively). Mucosal mast cell infiltration was associated with distal esophageal contraction as a key pathophysiologic factor of NCCP.

  18. High-speed video imaging and digital analysis of microscopic features in contracting striated muscle cells

    NASA Astrophysics Data System (ADS)

    Roos, Kenneth P.; Taylor, Stuart R.

    1993-02-01

    The rapid motion of microscopic features such as the cross striations of single contracting muscle cells are difficult to capture with conventional optical microscopes, video systems, and image processing approaches. An integrated digital video imaging microscope system specifically designed to capture images from single contracting muscle cells at speeds of up to 240 Hz and to analyze images to extract features critical for the understanding of muscle contraction is described. This system consists of a brightfield microscope with immersion optics coupled to a high-speed charge-coupled device (CCD) video camera, super-VHS (S- VHS) and optical media disk video recording (OMDR) systems, and a semiautomated digital image analysis system. Components are modified to optimize spatial and temporal resolution to permit the evaluation of submicrometer features in real physiological time. This approach permits the critical evaluation of the magnitude, time course, and uniformity of contractile function throughout the volume of a single living cell with higher temporal and spatial resolutions than previously possible.

  19. Brain Functional Connectivity Is Different during Voluntary Concentric and Eccentric Muscle Contraction

    PubMed Central

    Yao, Wan X.; Jiang, Zhiguo; Li, Jinqi; Jiang, Changhao; Franlin, Crystal G.; Lancaster, Jack L.; Huang, Yufei; Yue, Guang H.

    2016-01-01

    Previous studies report greater activation in the cortical motor network in controlling eccentric contraction (EC) than concentric contraction (CC) of human skeletal muscles despite lower activation level of the muscle associated with EC. It is unknown, however, whether the strength of functional coupling between the primary motor cortex (M1) and other involved areas in the brain differs as voluntary movements are controlled by a network of regions in the primary, secondary and association cortices. Examining fMRI-based functional connectivity (FC) offers an opportunity to measure strength of such coupling. To address the question, we examined functional MRI (fMRI) data acquired during EC and CC (20 contractions each with similar movement distance and speed) of the right first dorsal interosseous (FDI) muscle in 11 young (20–32 years) and healthy individuals and estimated FC between the M1 and a number of cortical regions in the motor control network. The major findings from the mechanical and fMRI-based FC analysis were that (1) no significant differences were seen in movement distance, speed and stability between the EC and CC; (2) significantly stronger mean FC was found for CC than EC. Our finding provides novel insights for a better understanding of the control mechanisms underlying voluntary movements produced by EC and CC. The finding is potentially helpful for guiding the development of targeted sport training and/or therapeutic programs for performance enhancement and injury prevention. PMID:27895590

  20. Brain Functional Connectivity Is Different during Voluntary Concentric and Eccentric Muscle Contraction.

    PubMed

    Yao, Wan X; Jiang, Zhiguo; Li, Jinqi; Jiang, Changhao; Franlin, Crystal G; Lancaster, Jack L; Huang, Yufei; Yue, Guang H

    2016-01-01

    Previous studies report greater activation in the cortical motor network in controlling eccentric contraction (EC) than concentric contraction (CC) of human skeletal muscles despite lower activation level of the muscle associated with EC. It is unknown, however, whether the strength of functional coupling between the primary motor cortex (M1) and other involved areas in the brain differs as voluntary movements are controlled by a network of regions in the primary, secondary and association cortices. Examining fMRI-based functional connectivity (FC) offers an opportunity to measure strength of such coupling. To address the question, we examined functional MRI (fMRI) data acquired during EC and CC (20 contractions each with similar movement distance and speed) of the right first dorsal interosseous (FDI) muscle in 11 young (20-32 years) and healthy individuals and estimated FC between the M1 and a number of cortical regions in the motor control network. The major findings from the mechanical and fMRI-based FC analysis were that (1) no significant differences were seen in movement distance, speed and stability between the EC and CC; (2) significantly stronger mean FC was found for CC than EC. Our finding provides novel insights for a better understanding of the control mechanisms underlying voluntary movements produced by EC and CC. The finding is potentially helpful for guiding the development of targeted sport training and/or therapeutic programs for performance enhancement and injury prevention.

  1. Selective activation of lower leg muscles during maximum voluntary isometric contractions.

    PubMed

    Hagen, Marco; Schwiertz, Gerrit; Landorf, Karl B; Menz, Hylton B; Murley, George S

    2016-12-01

    The pronators and supinators play a key role in the medio-lateral stability of the ankle joint complex (i.e. talo-crural and subtalar joints). We hypothesized that each shank muscle has a specific activation pattern determined by its anatomical course around the axes of the subtalar and talo-crural joints. A secondary objective was to examine the effect of foot posture on these activation patterns. Forty-nine young adults (25 normal-arched feet, 24 flat-arched feet) performed maximum voluntary isometric contractions against manual resistance in four movement directions: plantarflexion (PF), dorsiflexion (DF), pronation (PRO) and supination (SUP). Electromyographic activity was recorded from tibialis posterior (TP) and peroneus longus (PL) with intramuscular electrodes, and gastrocnemius medialis (GM) and tibialis anterior (TA) with surface electrodes. When compared to their agonist function, all muscles were co-activated at significantly lower levels in their synergistic function (GM: 23% during SUP, TA: 72% during SUP; TP: 42% during PF, PL: 52% during PF) (p<0.001). A significant interaction between foot posture and contraction type was evident for TA. During isometric contractions, the electromyographic activity of the shank muscles is geared to their biomechanical advantage according to their position relative to the subtalar and talo-crural joint axes.

  2. Effect of muscle contraction levels on the force-length relationship of the human Achilles tendon during lengthening of the triceps surae muscle-tendon unit.

    PubMed

    Sugisaki, Norihide; Kawakami, Yasuo; Kanehisa, Hiroaki; Fukunaga, Tetsuo

    2011-07-28

    Findings from animal experiments are sometimes contradictory to the idea that the tendon structure is a simple elastic spring in series with muscle fibers, and suggest influence of muscle contraction on the tendon mechanical properties. The purpose of the present study was to investigate the influence of muscle contraction levels on the force-length relationship of the human Achilles tendon during lengthening of the triceps surae muscle-tendon unit. For seven subjects, ankle dorsiflexion was performed without (passive condition) and with contraction of plantar flexor muscles (eccentric conditions, at 3 contraction levels) on an isokinetic dynamometer. Deformation of the Achilles tendon during each trial was measured using ultrasonography. The Achilles tendon force corresponding to the tendon elongation of 10mm in the passive condition was significantly smaller than those in the eccentric conditions (p<0.05 or p<0.01). Within the eccentric conditions, the Achilles tendon force corresponding to the tendon elongation of 10mm was significantly greater in the maximal contraction level than those in submaximal eccentric conditions (p<0.05 or p<0.01). In addition, the tendon stiffness was greater in higher contraction levels (p<0.05 or p<0.01). Present results suggest that the human tendon structure is not a simple elastic spring in series with muscle fibers.

  3. Influence of structure on the tissue dynamics of the human soleus muscle observed in MRI studies during isometric contractions.

    PubMed

    Hodgson, John A; Finni, Taija; Lai, Alex M; Edgerton, V Reggie; Sinha, Shantanu

    2006-05-01

    This article investigates how the internal structure of muscle and its relationship with tendon and even skeletal structures influence the translation of muscle fiber contractions into movement of a limb. Reconstructions of the anatomy of the human soleus muscle from the Visible Human Dataset (available from the National Library of Medicine), magnetic resonance images (MRI), and cadaver studies revealed a complex 3D connective tissue structure populated with pennate muscle fibers. The posterior aponeurosis and the median septum of the soleus form the insertion of the muscle and are continuous with the Achilles tendon. The distal extremities of the pennate muscle fibers attach to these structures. The anterior aponeurosis is located intramuscularly, between the posterior aponeurosis and the median septum. It forms the origin of the muscle and contacts the proximal extremities of the soleus muscle fibers. MRI measurements of in vivo tissue velocities during isometric contractions (20% and 40% maximum voluntary contractions) revealed a similarly complex 3D distribution of tissue movements. The distribution of velocities was similar to the distribution of major connective tissue structures within the muscle. During an isometric contraction, muscle fiber contractions move the median septum and posterior aponeurosis proximally, relative to the anterior aponeurosis. The pennate arrangement of muscle fibers probably amplifies muscle fiber length changes but not sufficiently to account for the twofold difference in muscle fiber length changes relative to excursion of the calcaneus. The discrepancy may be accounted for by an additional gain mechanism operating directly on the Achilles tendon by constraining the posterior movement of the tendon, which would otherwise occur due to the increasingly posterior location of the calcaneus in plantarflexeion.

  4. ATP-sensitive potassium channels mediate contraction-induced attenuation of sympathetic vasoconstriction in rat skeletal muscle.

    PubMed

    Thomas, G D; Hansen, J; Victor, R G

    1997-06-01

    Sympathetic vasoconstriction is sensitive to inhibition by metabolic events in contracting rat and human skeletal muscle, but the underlying cellular mechanisms are unknown. In rats, this inhibition involves mainly alpha2-adrenergic vasoconstriction, which relies heavily on Ca2+ influx through voltage-dependent Ca2+ channels. We therefore hypothesized that contraction-induced inhibition of sympathetic vasoconstriction is mediated by ATP-sensitive potassium (KATP) channels, a hyperpolarizing vasodilator mechanism that could be activated by some metabolic product(s) of skeletal muscle contraction. We tested this hypothesis in anesthetized rats by measuring femoral artery blood flow responses to lumbar sympathetic nerve stimulation or intraarterial hindlimb infusion of the specific alpha2-adrenergic agonist UK 14,304 during KATP channel activation with diazoxide in resting hindlimb and during KATP channel block with glibenclamide in contracting hindlimb. The major new findings are twofold. First, like muscle contraction, pharmacologic activation of KATP channels with diazoxide in resting hindlimb dose dependently attenuated the vasoconstrictor responses to either sympathetic nerve stimulation or intraarterial UK 14,304. Second, the large contraction-induced attenuation in sympathetic vasoconstriction elicited by nerve stimulation or UK 14,304 was partially reversed when the physiologic activation of KATP channels produced by muscle contraction was prevented with glibenclamide. We conclude that contraction-induced activation of KATP channels is a major mechanism underlying metabolic inhibition of sympathetic vasoconstriction in exercising skeletal muscle.

  5. Voluntary breathing increases corticospinal excitability of lower limb muscle during isometric contraction.

    PubMed

    Shirakawa, Kazuki; Yunoki, Takahiro; Afroundeh, Roghayyeh; Lian, Chang-Shun; Matsuura, Ryouta; Ohtsuka, Yoshinori; Yano, Tokuo

    2015-10-01

    The aim of the present study was to determine the effects of voluntary breathing on corticospinal excitability of a leg muscle during isometric contraction. Seven subjects performed 5-s isometric knee extension at the intensity of 10% of maximal voluntary contraction (10% MVC). During the 10% MVC, the subjects were instructed to breath normally (NORM) or to inhale (IN) or exhale (OUT) once as fast as possible. Motor-evoked potentials (MEPs) induced by transcranialmagnetic stimulation in the right vastus lateralis (VL) during the 10% MVC were recorded and compared during the three breathing tasks. MEPs in IN and OUT were significantly higher than that in NORM. Effort sense of breathing was significantly higher in IN and OUT than in NORM. There was a significant positive correlation between MEP and effort sense of breathing. These results suggest that activation of the breathing-associated cortical areas with voluntary breathing is involved in the increase in corticospinal excitability of the VL during isometric contraction.

  6. ( sup 3 H)QNB binding and contraction of rabbit colonic smooth muscle cells

    SciTech Connect

    Ringer, M.J.; Hyman, P.E.; Kao, H.W.; Hsu, C.T.; Tomomasa, T.; Snape, W.J. Jr. )

    1987-11-01

    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 receptors 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.

  7. Blood flow and muscle oxygenation during low, moderate, and maximal sustained isometric contractions.

    PubMed

    McNeil, Chris J; Allen, Matti D; Olympico, Eric; Shoemaker, J Kevin; Rice, Charles L

    2015-09-01

    A reduction of blood flow to active muscle will precipitate fatigue, and sustained isometric contractions produce intramuscular and compartmental pressures that can limit flow. The present study explored how blood flow and muscle oxygenation respond to isometric contractions at low, moderate, and maximal intensities. Over two visits, 10 males (26 ± 2 yr; means ± SD) performed 1-min dorsiflexion contractions at 30, 60, and 100% of maximal voluntary contraction (MVC) torque. Doppler ultrasound of the anterior tibial artery was used to record arterial diameter and mean blood velocity and to calculate absolute blood flow. The tissue oxygenation index (TOI) of tibialis anterior was acquired with near-infrared spectroscopy (NIRS). There was a progressive increase in blood flow at 30% MVC (peak of 289 ± 139% resting value), no change from rest until an increase in the final 10 s of exercise at 60% MVC (peak of 197 ± 102% rest), and an initial decrease (59 ± 30% resting value) followed by a progressive increase at 100% MVC (peak of 355 ± 133% rest). Blood flow was greater at 30 and 100% than 60% MVC during the last 30 s of exercise. TOI was ∼63% at rest and, within 30 s of exercise, reached steady-state values of ∼42%, ∼22%, and ∼22% for 30, 60, and 100% MVC, respectively. Even maximal contraction of the dorsiflexors is unable to cause more than a transient decrease of flow in the anterior tibial artery. Unlike dynamic or intermittent isometric exercise, our results indicate blood flow is not linearly graded with intensity or directly coupled with oxygenation during sustained isometric contractions.

  8. Whey protein hydrolysate augments tendon and muscle hypertrophy independent of resistance exercise contraction mode.

    PubMed

    Farup, J; Rahbek, S K; Vendelbo, M H; Matzon, A; Hindhede, J; Bejder, A; Ringgard, S; Vissing, K

    2014-10-01

    In a comparative study, we investigated the effects of maximal eccentric or concentric resistance training combined with whey protein or placebo on muscle and tendon hypertrophy. 22 subjects were allocated into either a high-leucine whey protein hydrolysate + carbohydrate group (WHD) or a carbohydrate group (PLA). Subjects completed 12 weeks maximal knee extensor training with one leg using eccentric contractions and the other using concentric contractions. Before and after training cross-sectional area (CSA) of m. quadriceps and patellar tendon CSA was quantified with magnetic resonance imaging and a isometric strength test was used to assess maximal voluntary contraction (MVC) and rate of force development (RFD). Quadriceps CSA increased by 7.3 ± 1.0% (P < 0.001) in WHD and 3.4 ± 0.8% (P < 0.01) in PLA, with a greater increase in WHD compared to PLA (P < 0.01). Proximal patellar tendon CSA increased by 14.9 ± 3.1% (P < 0.001) and 8.1 ± 3.2% (P = 0.054) for WHD and PLA, respectively, with a greater increase in WHD compared to PLA (P < 0.05), with no effect of contraction mode. MVC and RFD increased by 15.6 ± 3.5% (P < 0.001) and 12-63% (P < 0.05), respectively, with no group or contraction mode effects. In conclusion, high-leucine whey protein hydrolysate augments muscle and tendon hypertrophy following 12 weeks of resistance training - irrespective of contraction mode.

  9. 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.

  10. Lower muscle co-contraction in flutter kicking for competitive swimmers.

    PubMed

    Matsuda, Yuji; Hirano, Masami; Yamada, Yosuke; Ikuta, Yasushi; Nomura, Teruo; Tanaka, Hiroaki; Oda, Shingo

    2016-02-01

    The purpose of this study was to examine the difference in muscle activation pattern and co-contraction of the rectus and biceps femoris in flutter-kick swimming between competitive and recreational swimmers, to better understand the mechanism of repetitive kicking movements during swimming. Ten competitive and 10 recreational swimmers swam using flutter kicks at three different velocities (100%, 90%, and 80% of their maximal velocity) in a swimming flume. Surface electromyographic signals (EMG) were obtained from the rectus (RF) and biceps femoris (BF), and lower limb kinematic data were obtained at the same time. The beginning and ending of one kick cycle was defined as when the right lateral malleolus reached its highest position in the vertical axis. The offset timing of muscle activation of RF in the recreational swimmers was significantly later at all velocities than in the competitive swimmers (47-48% and 26-33% of kick time of one cycle for recreational and competitive swimmers, respectively), although the kinematic data and other activation timing of RF and BF did not differ between groups. A higher integrated EMG of RF during hip extension and knee extension induced a higher level of muscle co-contraction between RF and BF in the recreational swimmers. These results suggest that long-term competitive swimming training can induce an effective muscle activation pattern in the upper legs.

  11. Relationship between innervation zone width and mean muscle fiber conduction velocity during a sustained isometric contraction

    PubMed Central

    Ye, X.; Beck, T.W.; Wages, N.P.

    2015-01-01

    Objectives: To examine the relationship between the biceps brachii muscle innervation zone (IZ) width and the mean muscle fiber conduction velocity (MFCV) during a sustained isometric contraction. Methods: Fifteen healthy men performed a sustained isometric elbow flexion exercise at their 60% maximal voluntary contraction (MVC) until they could not maintain the target force. Mean MFCV was estimated through multichannel surface electromyographic recordings from a linear electrode array. Before exercise, IZ width was quantified. Separate non-parametric one-way analyses of variance (ANOVAs) were used to examine whether there was a difference in each mean MFCV variable among groups with different IZ width. In addition, separate bivariate correlations were also performed to examine the relationships between the IZ width and the mean MFCV variables during the fatiguing exercise. Results: There was a significant difference in the percent decline of mean MFCV (%ΔMFCV) among groups with different IZ width (χ2 (3)=11.571, p=0.009). In addition, there was also a significant positive relationship between the IZ width and the %ΔMFCV (Kendall’s tau= 0.807; p<0.001). Conclusions: We believe that such relationship is likely influenced by both muscle fiber size and the muscle fiber type composition. PMID:25730657

  12. Influence on muscle oxygenation to EMG parameters at different skeletal muscle contraction

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Song, Gaoqing

    2010-02-01

    The purpose of this study is to investigate the influence of muscle oxygenation on EMG parameters during isometric and incremental exercises and to observe the relationship between EMG parameters and muscle oxygenation. Twelve rowers took part in the tests. Near infrared spectrometer was utilized for measurements of muscle oxygenation on lateral quadriceps. sEMG measurement is performed for EMG parameters during isometric and incremental exercises. Results indicated that Oxy-Hb decrease significantly correlated with IEMG, E/T ratio and frequency of impulse signal during 1/3 MVC and 2/3 MVC isometric exercise, and it is also correlated with IEMG, E/T ratio and frequency of impulse signal. Increase of IEMG occurred at the time after Oxy-Hb decrease during incremental exercise and highly correlated with BLa. It is concluded that no matter how heavy the intensity is, Oxy-Hb dissociation may play an important role in affecting EMG parameters of muscle fatigue during isometric exercise. 2) EMG parameters may be influenced by Oxy-Hb dissociation and blood lactate concentration during dynamic exercise.

  13. Influence on muscle oxygenation to EMG parameters at different skeletal muscle contraction

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Song, Gaoqing

    2009-10-01

    The purpose of this study is to investigate the influence of muscle oxygenation on EMG parameters during isometric and incremental exercises and to observe the relationship between EMG parameters and muscle oxygenation. Twelve rowers took part in the tests. Near infrared spectrometer was utilized for measurements of muscle oxygenation on lateral quadriceps. sEMG measurement is performed for EMG parameters during isometric and incremental exercises. Results indicated that Oxy-Hb decrease significantly correlated with IEMG, E/T ratio and frequency of impulse signal during 1/3 MVC and 2/3 MVC isometric exercise, and it is also correlated with IEMG, E/T ratio and frequency of impulse signal. Increase of IEMG occurred at the time after Oxy-Hb decrease during incremental exercise and highly correlated with BLa. It is concluded that no matter how heavy the intensity is, Oxy-Hb dissociation may play an important role in affecting EMG parameters of muscle fatigue during isometric exercise. 2) EMG parameters may be influenced by Oxy-Hb dissociation and blood lactate concentration during dynamic exercise.

  14. 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.

  15. Three-dimensional geometrical changes of the human tibialis anterior muscle and its central aponeurosis measured with three-dimensional ultrasound during isometric contractions

    PubMed Central

    Cresswell, Andrew G.; Lichtwark, Glen A.

    2016-01-01

    Background. Muscles not only shorten during contraction to perform mechanical work, but they also bulge radially because of the isovolumetric constraint on muscle fibres. Muscle bulging may have important implications for muscle performance, however quantifying three-dimensional (3D) muscle shape changes in human muscle is problematic because of difficulties with sustaining contractions for the duration of an in vivo scan. Although two-dimensional ultrasound imaging is useful for measuring local muscle deformations, assumptions must be made about global muscle shape changes, which could lead to errors in fully understanding the mechanical behaviour of muscle and its surrounding connective tissues, such as aponeurosis. Therefore, the aims of this investigation were (a) to determine the intra-session reliability of a novel 3D ultrasound (3DUS) imaging method for measuring in vivo human muscle and aponeurosis deformations and (b) to examine how contraction intensity influences in vivo human muscle and aponeurosis strains during isometric contractions. Methods. Participants (n = 12) were seated in a reclined position with their left knee extended and ankle at 90° and performed isometric dorsiflexion contractions up to 50% of maximal voluntary contraction. 3DUS scans of the tibialis anterior (TA) muscle belly were performed during the contractions and at rest to assess muscle volume, muscle length, muscle cross-sectional area, muscle thickness and width, fascicle length and pennation angle, and central aponeurosis width and length. The 3DUS scan involved synchronous B-mode ultrasound imaging and 3D motion capture of the position and orientation of the ultrasound transducer, while successive cross-sectional slices were captured by sweeping the transducer along the muscle. Results. 3DUS was shown to be highly reliable across measures of muscle volume, muscle length, fascicle length and central aponeurosis length (ICC ≥ 0.98, CV < 1%). The TA remained isovolumetric

  16. Regulation of muscle contraction by Ca2+ and ADP: focusing on the auto-oscillation (SPOC).

    PubMed

    Ishiwata, Shin'ichi; Shimamoto, Yuta; Suzuki, Madoka; Sasaki, Daisuke

    2007-01-01

    A molecular motor in striated muscle, myosin II, is a non-processive motor that is unable to perform physiological functions as a single molecule and acts as an assembly of molecules. It is widely accepted that a myosin II motor is an independent force generator; the force generated at a steady state is usually considered to be a simple sum of those generated by each motor. This is the case at full activation (pCa < 5 in the presence of MgATP); however, we found that the myosin II motors show cooperative functions, i.e., non-linear auto-oscillation, named SPOC (SPontaneous Oscillatory Contraction), when the activation level is intermediate between those of contraction and relaxation (that is, at the intermediate level of pCa, 5-6, for cardiac muscle, or at the coexistence of MgATP, MgADP and inorganic phosphate (Pi) at higher pCa (> 7) for both skeletal and cardiac muscles). Here, we summarize the characteristics of SPOC phenomena, especially focusing on the physiological significance of SPOC in cardiac muscle. We propose a new concept that the auto-oscillatory property, which is inherent to the contractile system of cardiac muscle, underlies the molecular mechanism of heartbeat. Additionally, we briefly describe the dynamic properties of the thin filaments, i.e., the Ca(2+)-dependent flexibility change of the thin filaments, which may be the basis for the SPOC phenomena. We also describe a newly developed experimental system named "bio-nanomuscle," in which tension is asserted on a single reconstituted thin filament by interacting with crossbridges in the A-band composed of the thick filament lattice. This newly devised hybrid system is expected to fill the gap between the single-molecule level and the muscle system.

  17. Appropriately placed surface EMG electrodes reflect deep muscle activity (psoas, quadratus lumborum, abdominal wall) in the lumbar spine.

    PubMed

    McGill, S; Juker, D; Kropf, P

    1996-11-01

    This study tested the possibility of obtaining the activity of deeper muscles in the torso-specifically psoas, quadratus lumborum, external oblique, internal oblique and transverse abdominis, using surface myoelectric electrodes. It was hypothesized that: (1) surface electrodes adequately represent the amplitude of deep muscles (specifically psoas, quadratus lumborum, external oblique, internal oblique, transverse abdominis); (2) a single surface electrode location would best represent the activation profiles of each deep muscle over a broad variety of tasks. We assumed that prediction of activation within 10% of maximum voluntary contraction (RMS difference between the surface and intramuscular channels), over the time history of the signal, was reasonable and acceptable to assist clinical interpretation of muscle activation amplitude, and ultimately for modeled estimates of muscle force. Surface electrodes were applied and intramuscular electrodes were inserted on the left side of the body in five men and three women who then performed a wide variety of flexor tasks (bent knee and straight leg situps and leg raises, curl ups), extensor tasks (including lifting barbells up to 70 kg), lateral bending tasks (standing lateral bend and horizontal lying side support), twisting tasks (standing and sitting), and internal/external hip rotation. Using the criteria of RMS difference and the coefficient of determination (R2) to compare surface with intramuscular myoelectric signals, the results indicated that selected surface electrodes adequately represent the amplitude of deep muscles-always within 15% RMS difference, or less with the exception of psoas where differences up to 20% were observed but only in certain maximum voluntary contraction efforts. It appears reasonable for spine modelers, and particularly clinicians, to assume well selected surface electrode locations provide a representation of these deeper muscles-as long as they recognize the magnitude of error for

  18. Wave Reflection and Central Aortic Pressure Are Increased in Response to Static and Dynamic Muscle Contraction at Comparable Workloads

    DTIC Science & Technology

    2008-02-01

    wave reflec- tion is an important determinant of the central blood pressure response during forearm muscle contractions. tension-time index; exercise ...pressor reflex; blood pressure THE PRESSOR RESPONSE to exercise had been thought to be greater as a result of static muscle contraction compared with...equivalent peripheral blood pressure response to forearm and lower body exercise may result in very different central aortic pressures due to differential

  19. Effect of time of contraction and rest on the masseter and anterior temporal muscles activity in subjects with temporomandibular disorder.

    PubMed

    Ries, Lilian Gerdi Kittel; Graciosa, Maylli Daiani; Soares, Licerry Palma; Sperandio, Fabiana Flores; Santos, Gilmar Moraes; Degan, Viviane Veroni; Gadotti, Inaê Caroline

    2016-04-01

    Purpose The main objective of this study was to investigate the effect of time of contraction and rest on the masseter and temporal muscles activity. Methods 49 female subjects between 18 and 30 years of age were divided into TMD (n: 26) and control groups (n: 23). Surface electromyograph was used to evaluate the anterior temporal and masseter muscles during contraction and rest protocols. The root means square, median frequency and slope coefficient of the linear regression line parameters were analyzed. Results A significant effect of time in the contraction and rest muscle protocols was found. TMD patients showed a significant decrease in median frequency in the right masseter muscle and the slope coefficient in the right temporal muscle during the contraction protocol to control subjects. Conclusion Despite the TMD patients presented with higher fatigue susceptibility compared to the control group, both groups must meet the maximum time of 5 s of maximum voluntary contraction and at least 30 s rest between successive contractions of masticatory muscles during clinical or research assessment protocols.

  20. The experimental type 2 diabetes therapy glycogen phosphorylase inhibition can impair aerobic muscle function during prolonged contraction.

    PubMed

    Baker, David J; Greenhaff, Paul L; MacInnes, Alan; Timmons, James A

    2006-06-01

    Glycogen phosphorylase inhibition represents a promising strategy to suppress inappropriate hepatic glucose output, while muscle glycogen is a major source of fuel during contraction. Glycogen phosphorylase inhibitors (GPi) currently being investigated for the treatment of type 2 diabetes do not demonstrate hepatic versus muscle glycogen phosphorylase isoform selectivity and may therefore impair patient aerobic exercise capabilities. Skeletal muscle energy metabolism and function are not impaired by GPi during high-intensity contraction in rat skeletal muscle; however, it is unknown whether glycogen phosphorylase inhibitors would impair function during prolonged lower-intensity contraction. Utilizing a novel red cell-perfused rodent gastrocnemius-plantaris-soleus system, muscle was pretreated for 60 min with either 3 micromol/l free drug GPi (n=8) or vehicle control (n=7). During 60 min of aerobic contraction, GPi treatment resulted in approximately 35% greater fatigue. Muscle glycogen phosphorylase a form (P<0.01) and maximal activity (P<0.01) were reduced in the GPi group, and postcontraction glycogen (121.8 +/- 16.1 vs. 168.3 +/- 8.5 mmol/kg dry muscle, P<0.05) was greater. Furthermore, lower muscle lactate efflux and glucose uptake (P<0.01), yet higher muscle Vo(2), support the conclusion that carbohydrate utilization was impaired during contraction. Our data provide new confirmation that muscle glycogen plays an essential role during submaximal contraction. Given the critical role of exercise prescription in the treatment of type 2 diabetes, it will be important to monitor endurance capacity during the clinical evaluation of nonselective GPi. Alternatively, greater effort should be devoted toward the discovery of hepatic-selective GPi, hepatic-specific drug delivery strategies, and/or alternative strategies for controlling excess hepatic glucose production in type 2 diabetes.

  1. Mechanical Anisotropy of Rat Aortic Smooth Muscle Cells Decreases with Their Contraction

    NASA Astrophysics Data System (ADS)

    Nagayama, Kazuaki; Matsumoto, Takeo

    Tensile properties of smooth muscle cells freshly isolated from rat thoracic aortas (FSMCs) in their major and minor axes were measured using a laboratory-made micro tensile tester. The relationship between the tension applied to a cell and its elongation was obtained in untreated cells and those treated with 10-5M serotonin to induce contraction. An initial stiffness of untreated FSMCs, normalized by their initial cross-sectional area perpendicular to the stretch direction, was significantly higher in the major axis (14.8±4.3kPa, mean±SEM, n=5) than the minor axis (2.8±1.0kPa, n=5). The stiffness increased significantly in response to the contraction, but the increase was much higher in the minor axis (59.0±9.4kPa, n=4) than in the major (88.1±13.3kPa, n=4). The difference between the two directions was insignificant in the contracted state. Observations of the morphology of actin filaments with a confocal laser scanning microscope in untreated FSMCs revealed that they were long fibers running almost parallel to the major axis, while those in contracted cells showed an aggregated structure without a preferential direction. These results may indicate that anisotropy in untreated FSMCs is caused by the anisotropic alignment of their actin filaments, and that such anisotropy disappears in response to actin filament reorganization caused by the contraction.

  2. Mechanical control of the rising phase of contraction of frog skeletal and cardiac muscle

    PubMed Central

    1977-01-01

    The effect of shortening on contractile activity was studied in experiments in which shortening during the rising phase of an isotonic contraction was suddenly stopped. At the same muscle length and the same time after stimulation the rise in tension was much faster, if preceded by shortening, than during an isometric contraction, demonstrating an increase in contractile activity. In this experiment the rate of tension rise determined in various phases of contraction was proportional to the rate of isotonic shortening at the same time after stimulation. Therefore, the time course of the isotonic rising phase could be derived from the tension rise after shortening. The rate of isotonic shortening was found to be unrelated to the tension generated at various lengths and to correspond closely to the activation process induced by shortening. The length response explains differences between isotonic and isometric contractions with regard to energy release (Fenn effect) and time relations. These results extend previous work which showed that shortening during later phases of a twitch prolongs, while lengthening abbreviates contraction. Thus the length responses, which have been called shortening activation and lengthening deactivation, control activity throughout an isotonic twitch. PMID:591919

  3. Memories of early work on muscle contraction and regulation in the 1950's and 1960's

    SciTech Connect

    Huxley, Hugh E.

    2008-04-25

    Professor Ebashi's epic work on the biochemistry of the regulation of muscle contraction began in the early 1950's, during the same period that work on the molecular basis of force production in muscle was also beginning. The latter work started in two MRC Research Units in the UK, and was continued jointly by the two workers from those Units who had, independently, gone to MIT to learn the new techniques of electron microscopy and to apply them to muscle. In a somewhat similar fashion, Professor Ebashi also spent one or two years in the USA, continuing his work on the role of calcium in muscle regulation in Lippman's laboratory, before returning to Japan to achieve the great breakthroughs in this work during the 1960's. Hanson and Huxley, after putting forward the overlapping actin and myosin filament arrays model for the striated muscle sarcomere, and subsequently the sliding filament model of muscle contraction (simultaneously with A.F Huxley and R. Niedergerke), returned to the UK to pursue detailed structural studies in separate Research Units, in a mixture of consultation, collaboration, and competition, during the later 1950's and throughout the 1960's. However, the path to enlightenment described here in some detail was somewhat more tortuous than the standard literature perhaps reveals. Nevertheless, by the time of the Cold Spring Harbor Symposium on Muscle Contraction in 1972, the two lines of enquiry on regulation itself, and on the tilting cross-bridge model of force production, had arrived at a good deal of common ground, and indeed the identification of troponin and its periodic distribution along the actin filaments had helped resolve a long-standing puzzle in the interpretation of the low angle X-ray diagram. Since then, an enormous amount of remarkable new work has been necessary to establish troponin regulation and the tilting cross-bridge mechanism in molecular detail, but the work in the 1950's and 1960's has provided a firm and accurate basis

  4. Muscle plasticity related to changes in tubulin and αB-crystallin levels induced by eccentric contraction in rat skeletal muscles.

    PubMed

    Jee, H; Ochi, E; Sakurai, T; Lim, J-Y; Nakazato, K; Hatta, H

    2016-09-01

    We used the model of eccentric contraction of the hindlimb muscle by Ochi et al. to examine the role of eccentric contraction in muscle plasticity. This model aims to focus on stimulated skeletal muscle responses by measuring tissue weights and tracing the quantities of αB-crystallin and tubulin. The medial gastrocnemius muscle (GCM) responded to electrically induced eccentric contraction (EIEC) with significant increases in tissue weight (p < 0.01) and the ratio of tissue weight to body weight (p < 0.05); however, there was a decrease in soleus muscle weight after EIEC. EIEC in the GCM caused contractile-induced sustenance of the traced proteins, but the soleus muscle exhibited a remarkable decrease in α-tubulin and a 19% decrease in αB-crystallin. EIEC caused fast-to-slow myosin heavy chain (MHC) isoform type-oriented shift within both the GCM and soleus muscle. These results have shown that different MHC isoform type-expressing slow and fast muscles commonly undergo fast-to-slow type MHC isoform transformation. This suggests that different levels of EIEC affected each of the slow and fast muscles to induce different quantitative changes in the expression of αB-crystallin and α-tubulin.

  5. Dynamics of Muscle Microcirculatory and Blood-myocyte O2 Flux During Contractions

    PubMed Central

    Poole, David C.; Copp, Steven W.; Hirai, Daniel M.; Musch, Timothy I.

    2011-01-01

    The O2 requirements of contracting skeletal muscle may increase 100-fold above rest. In 1919 August Krogh’s brilliant insights recognized the capillary as the principal site for this increased blood-myocyte O2 flux. Based on the premise that most capillaries did not sustain RBC flux at rest Krogh proposed that capillary recruitment (i.e., initiation of red blood cell (RBC) flux in previously non-flowing capillaries) increased the capillary surface area available for O2 flux and reduced mean capillary-to-mitochondrial diffusion distances. More modern experimental approaches reveal that most muscle capillaries may support RBC flux at rest. Thus, rather than contraction-induced capillary recruitment per se, increased RBC flux and hematocrit within already-flowing capillaries likely elevate perfusive and diffusive O2 conductances and hence blood-myocyte O2 flux. Additional surface area for O2 exchange is recruited but, crucially, this may occur along the length of already-flowing capillaries (i.e. longitudinal recruitment). Today, the capillary is still considered the principal site for O2 and substrate delivery to contracting skeletal muscle. Indeed, the presence of very low intramyocyte O2 partial pressures (PO2’s) and the absence of PO2 gradients, whilst refuting the relevance of diffusion distances, place an even greater importance on capillary hemodynamics. This emergent picture calls for a paradigm-shift in our understanding of the function of capillaries by de-emphasizing de novo ‘capillary recruitment.’ Diseases such as heart failure impair blood-myocyte O2 flux, in part, by decreasing the proportion of RBC-flowing capillaries. Knowledge of capillary function in healthy muscle is requisite for identification of pathology and efficient design of therapeutic treatments. PMID:21199399

  6. Effects of shakuyakukanzoto and its absorbed components on twitch contractions induced by physiological Ca2+ release in rat skeletal muscle.

    PubMed

    Kaifuchi, Noriko; Omiya, Yuji; Kushida, Hirotaka; Fukutake, Miwako; Nishimura, Hiroaki; Kase, Yoshio

    2015-07-01

    Shakuyakukanzoto (SKT) is a kampo medicine composed of equal proportions of Glycyrrhizae radix (G. radix) and Paeoniae radix (P. radix). A double-blind study reported that SKT significantly ameliorated painful muscle cramp in cirrhosis patients without the typical severe side effects of muscle weakness and central nervous system (CNS) depression. Previous basic studies reported that SKT and its active components induced relaxation by a direct action on skeletal muscle and that SKT did not depress CNS functions; however, why SKT has a lower incidence of muscle weakness remains unknown. In the present study, we investigated which components are absorbed into the blood of rats after a single oral administration of SKT to identify the active components of SKT. We also investigated the effects of SKT and its components on the twitch contraction induced by physiological Ca(2+) release. Our study demonstrated that SKT and five G. radix isolates, which are responsible for the antispasmodic effect of SKT, did not inhibit the twitch contraction in contrast to dantrolene sodium, a direct-acting peripheral muscle relaxant, indicating that the mechanisms of muscle contraction of SKT and dantrolene in skeletal muscle differ. These findings suggest that SKT does not reduce the contractile force in skeletal muscle under physiological conditions, i.e., SKT may have a low risk of causing muscle weakness in clinical use. Considering that most muscle relaxants and anticonvulsants cause various harmful side effects such as weakness and CNS depression, SKT appears to have a benign safety profile.

  7. Energy metabolism of the gastrocnemius and soleus muscles during isometric voluntary and electrically induced contractions in man

    PubMed Central

    Ratkevičius, Aivaras; Mizuno, Masao; Povilonis, Edward; Quistorff, Bjørn

    1998-01-01

    Phosphocreatine (PCr) and intracellular pH detected by 31P NMR in the gastrocnemius and soleus muscles were evaluated in order to compare the anaerobic ATP costs of voluntary and electrically induced exercise. Continuous isometric contraction at 40 % of maximum force and repeated isometric contractions at approximately 75 % of maximum force (contraction plus relaxation period of 0.5 s plus 2 s) were studied.Anaerobic ATP turnover in soleus and gastrocnemius muscles was slower during continuous voluntary contraction than during continuous electrically induced contraction (0.36 ± 0.04 versus 0.63 ± 0.05 mmol (kg wet wt)−1 s−1, P < 0.05, in soleus; 0.19 ± 0.03 versus 1.04 ± 0.04 mmol (kg wet wt)−1 s−1, P < 0.001, in gastrocnemius).There was no significant difference in anaerobic ATP turnover between voluntary and electrically induced exercise when repeated brief contractions were performed (0.22 ± 0.05 and 0.30 ± 0.04 mmol (kg wet wt)−1 s−1, respectively, for the soleus muscle and 0.57 ± 0.03 and 0.66 ± 0.07 mmol (kg wet wt)−1 s−1, respectively, for the gastrocnemius muscle).During continuous voluntary contraction, in contrast to continuous stimulated contraction, anaerobic ATP turnover was slower (P < 0.05) in the gastrocnemius than in the soleus muscle, which also showed a higher electromyogram amplitude (41.1 ± 1.1 % of maximum) than the medial gastrocnemius muscle (21.4 ± 3.6 % of maximum, P < 0.001).Anaerobic ATP turnover was faster (P < 0.05) in the gastrocnemius than in the soleus muscle during brief voluntary and brief electrically induced contractions.The results show that the anaerobic ATP costs were higher for electrically induced exercise than for voluntary exercise when continuous submaximal contraction was performed but not when brief high-intensity contractions were performed. The gastrocnemius muscle contributes to total force production relatively less than the soleus muscle during continuous voluntary plantar flexion at 40

  8. Effect of stretching on agonist-antagonist muscle activity and muscle force output during single and multiple joint isometric contractions.

    PubMed

    McBride, J M; Deane, R; Nimphius, S

    2007-02-01

    Eight moderately active male subjects where tested for peak force in an isometric knee extension test and peak force and rate of force development in an isometric squat test. Both tests where performed at a 100 degrees knee angle and average integrated electromyography (IEMG) was measured from the vastus medialis (VM), vastus lateralis (VL) and biceps femoris (BF) muscles. Subjects performed the two conditions, stretching (S) or control (C) in a randomized order. Subjects where tested for baseline strength measures in both the isometric knee extension and isometric squat and then either stretched or sat quietly for 10 min. Following S or C subjects where then tested at six time points. Following S peak force in the isometric knee extension was significantly (P < or = 0.05) less than C at 1, 2, 8 and 16 min post. No significant difference in peak force was found between S and C in the isometric squat. However, following S the rate of force development in the isometric squat was significantly less than C at immediately post. No significant differences where observed in IEMG of the VM or VL between S and C in either the isometric knee extension or isometric squat. However, IEMG significantly decreased in the BF at 1 min post after S in comparison with C in both the isometric knee extension and isometric squat. Stretching appears to decrease muscle force output in a single joint isometric contraction and rate of force development in a multiple joint isometric contraction. Possible changes in agonist-antagonist muscle activity patterns need to be further examined.

  9. Discharge properties of motor units during steady isometric contractions performed with the dorsiflexor muscles.

    PubMed

    Jesunathadas, Mark; Klass, Malgorzata; Duchateau, Jacques; Enoka, Roger M

    2012-06-01

    The purpose of this study was to record the discharge characteristics of tibialis anterior motor units over a range of target forces and to import these data, along with previously reported observations, into a computational model to compare experimental and simulated measures of torque variability during isometric contractions with the dorsiflexor muscles. The discharge characteristics of 44 motor units were quantified during brief isometric contractions at torques that ranged from recruitment threshold to an average of 22 ± 14.4% maximal voluntary contraction (MVC) torque above recruitment threshold. The minimal [range: 5.8-19.8 pulses per second (pps)] and peak (range: 8.6-37.5 pps) discharge rates of motor units were positively related to the recruitment threshold torque (R(2) ≥ 0.266; P < 0.001). The coefficient of variation for interspike interval at recruitment was positively associated with recruitment threshold torque (R(2) = 0.443; P < 0.001) and either decreased exponentially or remained constant as target torque increased above recruitment threshold torque. The variability in the simulated torque did not differ from the experimental values once the recruitment range was set to ∼85% MVC torque, and the association between motor twitch contraction times and peak twitch torque was defined as a weak linear association (R(2) = 0.096; P < 0.001). These results indicate that the steadiness of isometric contractions performed with the dorsiflexor muscle depended more on the distributions of mechanical properties than discharge properties across the population of motor units in the tibialis anterior.

  10. Phosphocreatine kinetics at the onset of contractions in skeletal muscle of MM creatine kinase knockout mice

    NASA Technical Reports Server (NTRS)

    Roman, Brian B.; Meyer, Ronald A.; Wiseman, Robert W.

    2002-01-01

    Phosphocreatine (PCr) depletion during isometric twitch stimulation at 5 Hz was measured by (31)P-NMR spectroscopy in gastrocnemius muscles of pentobarbital-anesthetized MM creatine kinase knockout (MMKO) vs. wild-type C57B (WT) mice. PCr depletion after 2 s of stimulation, estimated from the difference between spectra gated to times 200 ms and 140 s after 2-s bursts of contractions, was 2.2 +/- 0.6% of initial PCr in MMKO muscle vs. 9.7 +/- 1.6% in WT muscles (mean +/- SE, n = 7, P < 0.001). Initial PCr/ATP ratio and intracellular pH were not significantly different between groups, and there was no detectable change in intracellular pH or ATP in either group after 2 s. The initial difference in net PCr depletion was maintained during the first minute of continuous 5-Hz stimulation. However, there was no significant difference in the quasi-steady-state PCr level approached after 80 s (MMKO 36.1 +/- 3.5 vs. WT 35.5 +/- 4.4% of initial PCr; n = 5-6). A kinetic model of ATPase, creatine kinase, and adenylate kinase fluxes during stimulation was consistent with the observed PCr depletion in MMKO muscle after 2 s only if ADP-stimulated oxidative phosphorylation was included in the model. Taken together, the results suggest that cytoplasmic ADP more rapidly increases and oxidative phosphorylation is more rapidly activated at the onset of contractions in MMKO compared with WT muscles.

  11. Specific modulation of spinal and cortical excitabilities during lengthening and shortening submaximal and maximal contractions in plantar flexor muscles.

    PubMed

    Duclay, Julien; Pasquet, Benjamin; Martin, Alain; Duchateau, Jacques

    2014-12-15

    This study investigated the influence of the torque produced by plantar flexor muscles on cortical and spinal excitability during lengthening and shortening voluntary contractions. To that purpose, modulations of motor-evoked potential (MEP) and Hoffmann (H) reflex were compared in the soleus (SOL) and medial gastrocnemius (MG) during anisometric submaximal and maximal voluntary contraction (MVC) of the plantar flexor muscles. For the submaximal shortening and lengthening contractions, the target torque was set at 50% of their respective MVC force. The results indicate that the amplitudes of both MEP and H-reflex responses, normalized to the maximal M wave, were significantly (P < 0.05) lower during lengthening compared with shortening submaximal contraction. For these two parameters, the reduction reached, respectively, 22.1 and 31.9% for the SOL and 34.5 and 29.3% for the MG. During MVC, normalized MEP and H reflex of the SOL were both reduced significantly by 19.9% (P < 0.05) and 29.9% (P < 0.001) during lengthening and shortening contraction, respectively, whereas no significant change (P > 0.05) was observed for MG. In addition, the silent period in the ongoing electromyogram (EMG) activity following the MEP was significantly (P < 0.01) briefer during lengthening than shortening contractions but did not differ (P > 0.05) between contraction intensities and muscles. Together, these results indicate that cortical and spinal mechanisms involved in the modulation of muscle activation during shortening and lengthening contractions differ between synergistic muscles according to the torque produced. Data further document previous studies reporting that the specific modulation of muscle activation during lengthening contraction is not torque dependent.

  12. 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.

  13. 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

  14. Changes in joint stability with muscle contraction measured from transmission of mechanical vibration.

    PubMed

    Feltham, M G; van Dieën, J H; Coppieters, M W; Hodges, P W

    2006-01-01

    A non-invasive in vivo technique was developed to evaluate changes in wrist joint stability properties induced by increased co-activation of the forearm muscles in a gripping task. Mechanical vibration at 45, 50 and 55 Hz was applied to the radial head in ten healthy volunteers. Vibrations of the styloid process of the radius and the distal end of the metacarpal bone of the index finger were measured with triaxial accelerometers. Joint stability properties were quantified by the transfer function gain between accelerations on either side of the wrist-joint. Gain was calculated with the muscles at rest and at five force levels ranging from 5% to 25% of maximum grip force (%MF). During contraction the gain was significantly greater than in control trial (0%MF) for all contractions levels at 45 and 50 Hz and a trend for 15%MF and higher at 55 Hz. Group means of contraction force and gain were significantly correlated at 45 (R(2)=0.98) and 50 Hz (R(2)=0.72), but not at 55 Hz (R(2)=0.10). In conclusion, vibration transmission gain may provide a method to evaluate changes in joint stability properties.

  15. Thin-film dielectric elastomer sensors to measure the contraction force of smooth muscle cells

    NASA Astrophysics Data System (ADS)

    Araromi, O.; Poulin, A.; Rosset, S.; Favre, M.; Giazzon, M.; Martin-Olmos, C.; Liley, M.; Shea, H.

    2015-04-01

    The development of thin-film dielectric elastomer strain sensors for the characterization of smooth muscle cell (SMC) contraction is presented here. Smooth muscle disorders are an integral part of diseases such as asthma and emphysema. Analytical tools enabling the characterization of SMC function i.e. contractile force and strain, in a low-cost and highly parallelized manner are necessary for toxicology screening and for the development of new and more effective drugs. The main challenge with the design of such tools is the accurate measurement of the extremely low contractile cell forces expected as a result of SMC monolayer contraction (as low as ~ 100 μN). Our approach utilizes ultrathin (~5 μm) and soft elastomer membranes patterned with elastomer-carbon composite electrodes, onto which the SMCs are cultured. The cell contraction induces an in-plane strain in the elastomer membrane, predicted to be in the order 1 %, which can be measured via the change in the membrane capacitance. The cell force can subsequently be deduced knowing the mechanical properties of the elastomer membrane. We discuss the materials and fabrication methods selected for our system and present preliminary results indicating their biocompatibility. We fabricate functional capacitive senor prototypes with good signal stability over the several hours (~ 0.5% variation). We succeed in measuring in-plane strains of 1 % with our fabricated devices with good repeatability and signal to noise ratio.

  16. Calcium-activated force of human muscle fibers following a standardized eccentric contraction.

    PubMed

    Choi, Seung Jun; Widrick, Jeffrey J

    2010-12-01

    Peak Ca(2+)-activated specific force (force/fiber cross-sectional area) of human chemically skinned vastus lateralis muscle fiber segments was determined before and after a fixed-end contraction or an eccentric contraction of standardized magnitude (+0.25 optimal fiber length) and velocity (0.50 unloaded shortening velocity). Fiber myosin heavy chain (MHC) isoform content was assayed by SDS-PAGE. Posteccentric force deficit, a marker of damage, was similar for type I and IIa fibers but threefold greater for type IIa/IIx hybrid fibers. A fixed-end contraction had no significant effect on force. Multiple linear regression revealed that posteccentric force was explained by a model consisting of a fiber type-independent and a fiber type-specific component (r(2) = 0.91). Preeccentric specific force was directly associated with a greater posteccentric force deficit. When preeccentric force was held constant, type I and IIa fibers showed identical susceptibility to damage, while type IIa/IIx fibers showed a significantly greater force loss. This heightened sensitivity to damage was directly related to the amount of type IIx MHC in the hybrid fiber. Our model reveals a fiber-type sensitivity of the myofilament lattice or cytoskeleton to mechanical strain that can be described as follows: type IIa/IIx > type IIa = type I. If these properties extend to fibers in vivo, then alterations in the number of type IIa/IIx fibers may modify a muscle's susceptibility to eccentric damage.

  17. Triclosan impairs excitation–contraction coupling and Ca2+ dynamics in striated muscle

    PubMed Central

    Cherednichenko, Gennady; Zhang, Rui; Bannister, Roger A.; Timofeyev, Valeriy; Li, Ning; Fritsch, Erika B.; Feng, Wei; Barrientos, Genaro C.; Schebb, Nils H.; Hammock, Bruce D.; Beam, Kurt G.; Chiamvimonvat, Nipavan; Pessah, Isaac N.

    2012-01-01

    Triclosan (TCS), a high-production-volume chemical used as a bactericide in personal care products, is a priority pollutant of growing concern to human and environmental health. TCS is capable of altering the activity of type 1 ryanodine receptor (RyR1), but its potential to influence physiological excitation–contraction coupling (ECC) and muscle function has not been investigated. Here, we report that TCS impairs ECC of both cardiac and skeletal muscle in vitro and in vivo. TCS acutely depresses hemodynamics and grip strength in mice at doses ≥12.5 mg/kg i.p., and a concentration ≥0.52 μM in water compromises swimming performance in larval fathead minnow. In isolated ventricular cardiomyocytes, skeletal myotubes, and adult flexor digitorum brevis fibers TCS depresses electrically evoked ECC within ∼10–20 min. In myotubes, nanomolar to low micromolar TCS initially potentiates electrically evoked Ca2+ transients followed by complete failure of ECC, independent of Ca2+ store depletion or block of RyR1 channels. TCS also completely blocks excitation-coupled Ca2+ entry. Voltage clamp experiments showed that TCS partially inhibits L-type Ca2+ currents of cardiac and skeletal muscle, and [3H]PN200 binding to skeletal membranes is noncompetitively inhibited by TCS in the same concentration range that enhances [3H]ryanodine binding. TCS potently impairs orthograde and retrograde signaling between L-type Ca2+ and RyR channels in skeletal muscle, and L-type Ca2+ entry in cardiac muscle, revealing a mechanism by which TCS weakens cardiac and skeletal muscle contractility in a manner that may negatively impact muscle health, especially in susceptible populations. PMID:22891308

  18. Behaviour of human motor units in different muscles during linearly varying contractions