Cerebellar damage diminishes long-latency responses to multijoint perturbations

PubMed Central

Trautman, Paxson; Rasquinha, Russell J.; Bhanpuri, Nasir H.; Scott, Stephen H.; Bastian, Amy J.

2013-01-01

Damage to the cerebellum can cause significant problems in the coordination of voluntary arm movements. One prominent idea is that incoordination stems from an inability to predictively account for the complex mechanical interactions between the arm's several joints. Motivated by growing evidence that corrective feedback control shares important capabilities and neural substrates with feedforward control, we asked whether cerebellar damage impacts feedback stabilization of the multijoint arm appropriate for the arm's intersegmental dynamics. Specifically, we tested whether cerebellar dysfunction impacts the ability of posterior deltoid to incorporate elbow motion in its long-latency response (R2 = 45–75 ms and R3 = 75–100 ms after perturbation) to an unexpected torque perturbation. Healthy and cerebellar-damaged subjects were exposed to a selected pattern of shoulder-elbow displacements to probe the response pattern from this shoulder extensor muscle. The healthy elderly subjects expressed a long-latency response linked to both shoulder and elbow motion, including an increase/decrease in shoulder extensor activity with elbow flexion/extension. Critically, cerebellar-damaged subjects displayed the normal pattern of activity in the R3 period indicating an intact ability to rapidly integrate multijoint motion appropriate to the arm's intersegmental dynamics. However, cerebellar-damaged subjects had a lower magnitude of activity that was specific to the long-latency period (both R2 and R3) and a slightly delayed onset of multijoint sensitivity. Taken together, our results suggest that the basic motor pattern of the long-latency response is housed outside the cerebellum and is scaled by processes within the cerebellum. PMID:23390311

Stretch reflex excitability of the anti-gravity ankle extensor muscle in elderly humans.

PubMed

Kawashima, N; Nakazawa, K; Yamamoto, S-I; Nozaki, D; Akai, M; Yano, H

2004-01-01

To examine whether the stretch reflex excitability of the soleus muscle changes with age, stretch reflexes at rest (REST) and during weak voluntary contractions (ACT) were elicited in 18 older and 14 younger subjects. The amplitude of the stretch reflex responses and gain, defined as the gradient of the regression line for the relation between stretch reflex responses against the angular velocity of the applied perturbation, were evaluated in each short-latency (M1) and two long-latency components (M2 and M3). It was found that in the older group, both the amplitude and gain of the M1 component did not change from the REST to the ACT conditions, whereas in the younger group both variables significantly increased from the REST to ACT conditions. The latency of the M1 component was significantly shorter under the REST condition (older vs. younger: 51.8 +/- 7.37 vs. 55.1 +/- 8.69 ms), while no group differences were found in those variables under the ACT condition, suggesting that the muscle-tendon complexes of SOL muscles of the older subjects were less elastic and had less slack, probably due to age-related histochemical alterations. Further, the Hoffman reflex (H-reflex), elicited during the REST condition in 10 older and 11 younger subjects showed no significant differences, suggesting that the soleus motoneuron response to the Ia input was comparable between the two subject groups. The histochemical alterations occurring with the ageing process might augment the short-latency stretch reflex in the SOL muscle without enhancement of motoneuronal excitability, and this effect might be masked when the muscle is voluntarily activated.

Acute Effects of Foam Rolling, Static Stretching, and Dynamic Stretching During Warm-ups on Muscular Flexibility and Strength in Young Adults.

PubMed

Su, Hsuan; Chang, Nai-Jen; Wu, Wen-Lan; Guo, Lan-Yuen; Chu, I-Hua

2017-11-01

Foam rolling has been proposed to improve muscle function, performance, and joint range of motion (ROM). However, whether a foam rolling protocol can be adopted as a warm-up to improve flexibility and muscle strength is unclear. To examine and compare the acute effects of foam rolling, static stretching, and dynamic stretching used as part of a warm-up on flexibility and muscle strength of knee flexion and extension. Crossover study. University research laboratory. 15 male and 15 female college students (age 21.43 ± 1.48 y, weight 65.13 ± 12.29 kg, height 166.90 ± 6.99 cm). Isokinetic peak torque was measured during knee extension and flexion at an angular velocity of 60°/second. Flexibility of the quadriceps was assessed by the modified Thomas test, while flexibility of the hamstrings was assessed using the sit-and-reach test. The 3 interventions were performed by all participants in random order on 3 days separated by 48-72 hours. The flexibility test scores improved significantly more after foam rolling as compared with static and dynamic stretching. With regard to muscle strength, only knee extension peak torque (pre vs. postintervention) improved significantly after the dynamic stretching and foam rolling, but not after static stretching. Knee flexion peak torque remained unchanged. Foam rolling is more effective than static and dynamic stretching in acutely increasing flexibility of the quadriceps and hamstrings without hampering muscle strength, and may be recommended as part of a warm-up in healthy young adults.

Long-latency neurodegenerative disease in the western Pacific.

PubMed

Spencer, P S; Kisby, G E; Ludolph, A C

1991-08-01

The western Pacific parkinsonism-dementia and amyotrophic lateral sclerosis complex is a prototypical neurodegenerative disorder found among inhabitants of Guam, New Guinea (Irian Jaya, Indonesia) and Japan (Kii Peninsula, Honshu). Nonviral environmental factors peculiar to the affected populations seem to play a prominent etiologic role. Although cause-effect relationships cannot be established by epidemiologic studies alone, we have shown in all three affected population groups that individuals develop the amyotrophic lateral sclerosis variant of this disorder after heavy exposure to the raw or incompletely detoxified seed of neurotoxic cycad plants. Since long periods may elapse between cycad exposure and the appearance of neurological disease in humans, cycads may harbor a "slow toxin" that causes the postmitotic neuron to undergo slow irreversible degeneration. Two cycad neurotoxins are recognized, one of which (cycasin) is known to have long-latency effects (tumorigenesis) on mitotic neurons and replicating cells in other tissues. This paper explores the possible relationship between tumorigenesis and long-latency neurotoxicity, and discusses possible biologic markers of cycad exposure and subclinical neurodegenerative disease.

Long-latency auditory evoked potentials with verbal and nonverbal stimuli.

PubMed

Oppitz, Sheila Jacques; Didoné, Dayane Domeneghini; Silva, Débora Durigon da; Gois, Marjana; Folgearini, Jordana; Ferreira, Geise Corrêa; Garcia, Michele Vargas

2015-01-01

Long-latency auditory evoked potentials represent the cortical activity related to attention, memory, and auditory discrimination skills. Acoustic signal processing occurs differently between verbal and nonverbal stimuli, influencing the latency and amplitude patterns. To describe the latencies of the cortical potentials P1, N1, P2, N2, and P3, as well as P3 amplitude, with different speech stimuli and tone bursts, and to classify them in the presence and absence of these data. A total of 30 subjects with normal hearing were assessed, aged 18-32 years old, matched by gender. Nonverbal stimuli were used (tone burst; 1000Hz - frequent and 4000Hz - rare); and verbal (/ba/ - frequent; /ga/, /da/, and /di/ - rare). Considering the component N2 for tone burst, the lowest latency found was 217.45ms for the BA/DI stimulus; the highest latency found was 256.5ms. For the P3 component, the shortest latency with tone burst stimuli was 298.7 with BA/GA stimuli, the highest, was 340ms. For the P3 amplitude, there was no statistically significant difference among the different stimuli. For latencies of components P1, N1, P2, N2, P3, there were no statistical differences among them, regardless of the stimuli used. There was a difference in the latency of potentials N2 and P3 among the stimuli employed but no difference was observed for the P3 amplitude. Copyright © 2015 Associação Brasileira de Otorrinolaringologia e Cirurgia Cérvico-Facial. Published by Elsevier Editora Ltda. All rights reserved.

Cooperativity among Short Amyloid Stretches in Long Amyloidogenic Sequences

PubMed Central

He, Zhisong; Shi, Xiaohe; Feng, Kaiyan; Ma, Buyong; Cai, Yu-Dong

2012-01-01

Amyloid fibrillar aggregates of polypeptides are associated with many neurodegenerative diseases. Short peptide segments in protein sequences may trigger aggregation. Identifying these stretches and examining their behavior in longer protein segments is critical for understanding these diseases and obtaining potential therapies. In this study, we combined machine learning and structure-based energy evaluation to examine and predict amyloidogenic segments. Our feature selection method discovered that windows consisting of long amino acid segments of ∼30 residues, instead of the commonly used short hexapeptides, provided the highest accuracy. Weighted contributions of an amino acid at each position in a 27 residue window revealed three cooperative regions of short stretch, resemble the β-strand-turn-β-strand motif in A-βpeptide amyloid and β-solenoid structure of HET-s(218–289) prion (C). Using an in-house energy evaluation algorithm, the interaction energy between two short stretches in long segment is computed and incorporated as an additional feature. The algorithm successfully predicted and classified amyloid segments with an overall accuracy of 75%. Our study revealed that genome-wide amyloid segments are not only dependent on short high propensity stretches, but also on nearby residues. PMID:22761773

Quadriceps strength and weight acceptance strategies continue to improve two years after anterior cruciate ligament reconstruction

PubMed Central

Roewer, Ben D.; Di Stasi, Stephanie L.; Snyder-Mackler, Lynn

2011-01-01

The anterior cruciate ligament (ACL) is the most commonly-injured knee ligament during sporting activities. After injury, most individuals experience episodes of the knee giving way during daily activities (non-copers). Non-copers demonstrate asymmetrical quadriceps strength and movement patterns which could have long-term deleterious effects on the integrity of the knee joint. The purpose of this study was to determine if non-copers resolve their strength and movement asymmetries within two years after surgery. 26 non-copers were recruited to undergo pre-operative quadriceps strength testing and 3-dimensional gait analysis. Subjects underwent surgery to reconstruct the ligament followed by physical therapy focused on restoring normal range of motion, quadriceps strength, and function. Subjects returned for quadriceps strength testing and gait analysis six months and two years after surgery. Acutely after injury, quadriceps strength was asymmetric between limbs, but resolved six months after surgery. Asymmetric knee angles, knee moments, and knee and hip power profiles were also observed acutely after injury and persisted six months after surgery despite subjects achieving symmetrical quadriceps strength. Two years after surgery, quadriceps strength in the involved limb continued to improve and most kinematic and kinetic asymmetries resolved. These findings suggest that adequate quadriceps strength does not immediately resolve gait asymmetries in non-copers. They also suggest that non-copers have the capacity to improve their quadriceps strength and gait symmetry long after ACL reconstruction. PMID:21592482

Predictors of treatment response to strengthening and stretching exercises for patellofemoral pain: An examination of patellar alignment.

PubMed

Peng, Hsien-Te; Song, Chen-Yi

2015-12-01

Closed kinetic chain and quadriceps strengthening, combined with flexibility exercises of the lower limb musculature, is a common treatment for patellofemoral pain syndrome (PFPS). The effectiveness has been well documented; however, very little is known about which factors predict treatment success. A total of 43 female subjects with PFPS participated in an eight-week progressive leg press (LP) strengthening and stretching exercise program. A decrease of 1.5 cm on a 10 cm visual analog scale (VAS) score was used as an indicator for treatment success. The baseline patellar tilt angle difference (PTA-d) due to quadriceps contraction prior to treatment was evaluated as a predictor of treatment success. The logistic regression and receiver operating characteristics (ROC) curve analysis were performed to investigate the predictive value of PTA-d. PTA-d could significantly predict the treatment success of LP strengthening and stretching exercises. The odds ratio (OR) for having an unsuccessful outcome was 1.19 (95% confidence interval (CI), 1.03-1.39, P<0.021) per degree increment of PTA-d. The most optimal cut-off value for the clinical discrimination of treatment success after LP strengthening and stretching exercise was -1.5° of PTA-d (sensitivity=0.74, specificity=0.71). The area under the ROC curve was 0.73 (standard error=0.08). Female patients with PFPS whose quadriceps contraction reduced the lateral patellar tilt prior to LP strengthening and stretching exercise treatment are more likely to experience pain relief. It seems clinically important to check dynamic patellar tilt characteristics before treatment to aid in clinical decision making. Copyright © 2014 Elsevier B.V. All rights reserved.

Long latency postural responses are functionally modified by cognitive set.

PubMed

Beckley, D J; Bloem, B R; Remler, M P; Roos, R A; Van Dijk, J G

1991-10-01

We examined how cognitive set influences the long latency components of normal postural responses in the legs. We disturbed the postural stability of standing human subjects with sudden toe-up ankle rotations. To influence the subjects' cognitive set, we varied the rotation amplitude either predictably (serial 4 degrees versus serial 10 degrees) or unpredictably (random mixture of 4 degrees and 10 degrees). The subjects' responses to these ankle rotations were assessed from the EMG activity of the tibialis anterior, the medial gastrocnemius, and the vastus lateralis muscles of the left leg. The results indicate that, when the rotation amplitude is predictable, only the amplitude of the long latency (LL) response in tibialis anterior and vastus lateralis varied directly with perturbation size. Furthermore, when the rotation amplitude is unpredictable, the central nervous system selects a default amplitude for the LL response in the tibialis anterior. When normal subjects are exposed to 2 perturbation amplitudes which include the potential risk of falling, the default LL response in tibialis anterior appropriately anticipates the larger amplitude perturbation rather than the smaller or an intermediate one.

Role of stretch reflex in voluntary movements. [of human foot

NASA Technical Reports Server (NTRS)

Gottlieb, G. L.; Agarwal, G. C.

1975-01-01

The stretch reflex is often described as a spinal servomechanism, a device for assisting in the regulation of muscle length. Observation of the EMG response to mechanical interruption of voluntary movements fails to demonstrate a significant role for spinal reflexes at 40 msec latency. Two functional responses with latencies of 120 msec and 200 msec, implying supraspinal mediation, are observed.

Acute Effects of Three Different Stretching Protocols on the Wingate Test Performance

PubMed Central

Franco, Bruno L.; Signorelli, Gabriel R.; Trajano, Gabriel S.; Costa, Pablo B.; de Oliveira, Carlos G.

2012-01-01

The purpose of this study was to examine the acute effects of different stretching exercises on the performance of the traditional Wingate test (WT). Fifteen male participants performed five WT; one for familiarization (FT), and the remaining four after no stretching (NS), static stretching (SS), dynamic stretching (DS), and proprioceptive neuromuscular facilitation (PNF). Stretches were targeted for the hamstrings, quadriceps, and calf muscles. Peak power (PP), mean power (MP), and the time to reach PP (TP) were calculated. The MP was significantly lower when comparing the DS (7.7 ± 0.9 W/kg) to the PNF (7.3 ± 0.9 W/kg) condition (p < 0.05). For PP, significant differences were observed between more comparisons, with PNF stretching providing the lowest result. A consistent increase of TP was observed after all stretching exercises when compared to NS. The results suggest the type of stretching, or no stretching, should be considered by those who seek higher performance and practice sports that use maximal anaerobic power. Key points The mean power was significantly lower when comparing dynamic stretching.to proprioceptive neuromuscular facilitation. For peak power, significant differences were observed between more comparisons, with proprioceptive neuromuscular facilitation stretching providing the lowest result. A consistent increase of time to reach the peak was observed after all stretching exercises when compared to non-stretching. The type of stretching, or no stretching, should be considered by those who seek higher performance and practice sports that use maximal anaerobic power. PMID:24149116

The Relationship between Parameters of Long-Latency Evoked Potentials in a Multisensory Design.

PubMed

Hernández, Oscar H; García-Martínez, Rolando; Monteón, Victor

2016-10-01

In previous papers, we have shown that parameters of the omitted stimulus potential (OSP), which occurs at the end of a train of sensory stimuli, strongly depend on the modality. A train of stimuli also produces long-latency evoked potentials (LLEP) at the beginning of the train. This study is an extension of the OSP research, and it tested the relationship between parameters (ie, rate of rise, amplitude, and peak latency) of the P2 waves when trains of auditory, visual, or somatosensory stimuli were applied. The dynamics of the first 3 potentials in the train, related to habituation, were also studied. Twenty healthy young college volunteers participated in the study. As in the OSP, the P2 was faster and higher for auditory than for visual or somatosensory stimuli. The first P2 was swifter and higher than the second and the third potentials. The strength of habituation depends on the sensory modality and the parameter used. All these findings support the view that many long-latency brain potentials could share neural mechanisms related to wave generation. © EEG and Clinical Neuroscience Society (ECNS) 2015.

Reduced Short- and Long-Latency Afferent Inhibition Following Acute Muscle Pain: A Potential Role in the Recovery of Motor Output.

PubMed

Burns, Emma; Chipchase, Lucinda Sian; Schabrun, Siobhan May

2016-02-13

. Corticomotor output is reduced in response to acute muscle pain, yet the mechanisms that underpin this effect remain unclear. Here the authors investigate the effect of acute muscle pain on short-latency afferent inhibition, long-latency afferent inhibition, and long-interval intra-cortical inhibition to determine whether these mechanisms could plausibly contribute to reduced motor output in pain. . Observational same subject pre-post test design. . Neurophysiology research laboratory. . Healthy, right-handed human volunteers (n = 22, 9 male; mean age ± standard deviation, 22.6 ± 7.8 years). . Transcranial magnetic stimulation was used to assess corticomotor output, short-latency afferent inhibition, long-latency afferent inhibition, and long-interval intra-cortical inhibition before, during, immediately after, and 15 minutes after hypertonic saline infusion into right first dorsal interosseous muscle. Pain intensity and quality were recorded using an 11-point numerical rating scale and the McGill Pain Questionnaire. . Compared with baseline, corticomotor output was reduced at all time points (p = 0.001). Short-latency afferent inhibition was reduced immediately after (p = 0.039), and long-latency afferent inhibition 15 minutes after (p = 0.035), the resolution of pain. Long-interval intra-cortical inhibition was unchanged at any time point (p = 0.36). . These findings suggest short- and long-latency afferent inhibition, mechanisms thought to reflect the integration of sensory information with motor output at the cortex, are reduced following acute muscle pain. Although the functional relevance is unclear, the authors hypothesize a reduction in these mechanisms may contribute to the restoration of normal motor output after an episode of acute muscle pain. © 2016 American Academy of Pain Medicine. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Quadriceps Contusion

MedlinePlus

... An intramuscular contusion , which is when a muscle tears within the sheath (lining) that surrounds it. An ... the muscle and the sheath surrounding it both tear. Quadriceps contusions are common in sports that involve ...

Act quickly, decide later: long-latency visual processing underlies perceptual decisions but not reflexive behavior.

PubMed

Jolij, Jacob; Scholte, H Steven; van Gaal, Simon; Hodgson, Timothy L; Lamme, Victor A F

2011-12-01

Humans largely guide their behavior by their visual representation of the world. Recent studies have shown that visual information can trigger behavior within 150 msec, suggesting that visually guided responses to external events, in fact, precede conscious awareness of those events. However, is such a view correct? By using a texture discrimination task, we show that the brain relies on long-latency visual processing in order to guide perceptual decisions. Decreasing stimulus saliency leads to selective changes in long-latency visually evoked potential components reflecting scene segmentation. These latency changes are accompanied by almost equal changes in simple RTs and points of subjective simultaneity. Furthermore, we find a strong correlation between individual RTs and the latencies of scene segmentation related components in the visually evoked potentials, showing that the processes underlying these late brain potentials are critical in triggering a response. However, using the same texture stimuli in an antisaccade task, we found that reflexive, but erroneous, prosaccades, but not antisaccades, can be triggered by earlier visual processes. In other words: The brain can act quickly, but decides late. Differences between our study and earlier findings suggesting that action precedes conscious awareness can be explained by assuming that task demands determine whether a fast and unconscious, or a slower and conscious, representation is used to initiate a visually guided response.

Flexibility training in preadolescent female athletes: Acute and long-term effects of intermittent and continuous static stretching.

PubMed

Donti, Οlyvia; Papia, Konstantina; Toubekis, Argyris; Donti, Anastasia; Sands, William A; Bogdanis, Gregory C

2018-07-01

This study compared the acute and long-term effects of intermittent and continuous static stretching training on straight leg raise range of motion (ROM). Seventy-seven preadolescent female gymnasts were divided into a stretching (n = 57), and a control group (n = 20). The stretching group performed static stretching of the hip extensors of both legs, three times per week for 15 weeks. One leg performed intermittent (3 × 30 s with 30 s rest) while the other leg performed continuous stretching (90 s). ROM pre- and post-stretching was measured at baseline, on weeks 3, 6, 9, 12, 15 and after 2 weeks of detraining. ROM was increased during both intermittent and continuous stretching training, but remained unchanged in the control group. Intermittent stretching conferred a larger improvement in ROM compared to both continuous stretching and control from week 3, until the end of training, and following detraining (p = 0.045 to 0.001 and d = 0.80 to 1.41). During detraining, ROM after the intermittent protocol decreased (p = 0.001), while it was maintained after the continuous protocol (p = 0.36). Acute increases in ROM following the intermittent stretching were also larger than in the continuous (p = 0.038). Intermittent stretching was more effective than continuous, for both long-term and acute ROM enhancement in preadolescent female athletes.

Slow toxins, biologic markers, and long-latency neurodegenerative disease in the western Pacific region.

PubMed

Spencer, P S; Kisby, G E; Ludolph, A C

1991-05-01

The western Pacific parkinsonism-dementia and amyotrophic lateral sclerosis complex is a prototypical neurodegenerative disorder found among inhabitants of Guam, New Guinea (Irian Jaya, Indonesia) and Japan (Kii Peninsula, Honshu). Nonviral environmental factors peculiar to the affected populations seem to play a prominent etiologic role. Although cause-effect relationships cannot be established by epidemiologic studies alone, we have shown in all three affected population groups that individuals develop the amyotrophic lateral sclerosis variant of this disorder after heavy exposure to the raw or incompletely detoxified seed of neurotoxic cycad plants. Since long periods may elapse between cycad exposure and the appearance of neurological disease in humans, cycads may harbor a "slow toxin" that causes the postmitotic neuron to undergo slow irreversible degeneration. Two cycad neurotoxins are recognized, one of which (cycasin) is known to have long-latency effects (tumorigenesis) on mitotic neurons and replicating cells in other tissues. This paper explores the possible relationship between tumorigenesis and long-latency neurotoxicity, and discusses possible biologic markers of cycad exposure and subclinical neurodegenerative disease.

A new isometric quadriceps-strengthening exercise using EMG-biofeedback.

PubMed

Kesemenli, Cumhur C; Sarman, Hakan; Baran, Tuncay; Memisoglu, Kaya; Binbir, Ismail; Savas, Yilmaz; Isik, Cengiz; Boyraz, Ismail; Koc, Bunyamin

2014-01-01

A new isometric contraction quadriceps-strengthening exercise was developed to restore the quadriceps strength lost after knee surgery more rapidly. This study evaluated the results of this new method. Patients were taught to perform the isometric quadriceps-strengthening exercise in the unaffected knee in the supine position, and then they performed it in the affected knee. First, patients were taught the classical isometric quadriceps-strengthening exercise, and then they were taught our new alternative method: "pull the patella superiorly tightly and hold the leg in the same position for 10 seconds". Afterward, the quadriceps contraction was evaluated using a non-invasive Myomed 932 EMG-biofeedback device (Enraf-Nonius, The Netherlands) with gel-containing 48 mm electrodes (Türklab, The Turkey) placed on both knees. The isometric quadriceps-strengthening exercise performed using our new method had stronger contraction than the classical method (P < 0.01). The new method involving pulling the patella superiorly appears to be a better choice, which can be applied easily, leading to better patient compliance and greater quadriceps force after arthroscopic and other knee surgeries.

Correlation analysis of the long latency auditory evoked potential N2 and cognitive P3 with the level of lead poisoning in children

PubMed Central

Alvarenga, Kátia de Freitas; Alvarez Bernardez-Braga, Gabriela Rosito; Zucki, Fernanda; Duarte, Josilene Luciene; Lopes, Andrea Cintra; Feniman, Mariza Ribeiro

2013-01-01

Summary Introduction: The effects of lead on children's health have been widely studied. Aim: To analyze the correlation between the long latency auditory evoked potential N2 and cognitive P3 with the level of lead poisoning in Brazilian children. Methods: This retrospective study evaluated 20 children ranging in age from 7 to 14 years at the time of audiological and electrophysiological evaluations. We performed periodic surveys of the lead concentration in the blood and basic audiological evaluations. Furthermore, we studied the auditory evoked potential long latency N2 and cognitive P3 by analyzing the absolute latency of the N2 and P3 potentials and the P3 amplitude recorded at Cz. At the time of audiological and electrophysiological evaluations, the average concentration of lead in the blood was less than 10 ug/dL. Results: In conventional audiologic evaluations, all children had hearing thresholds below 20 dBHL for the frequencies tested and normal tympanometry findings; the auditory evoked potential long latency N2 and cognitive P3 were present in 95% of children. No significant correlations were found between the blood lead concentration and latency (p = 0.821) or amplitude (p = 0.411) of the P3 potential. However, the latency of the N2 potential increased with the concentration of lead in the blood, with a significant correlation (p = 0.030). Conclusion: Among Brazilian children with low lead exposure, a significant correlation was found between blood lead levels and the average latency of the auditory evoked potential long latency N2; however, a significant correlation was not observed for the amplitude and latency of the cognitive potential P3. PMID:25991992

Hip Strength in Patients with Quadriceps Strength Deficits after ACL Reconstruction.

PubMed

Bell, David R; Trigsted, Stephanie M; Post, Eric G; Walden, Courtney E

2016-10-01

Quadriceps strength deficits persist for years after anterior cruciate ligament (ACL) reconstruction, and patients with these deficits often shift torque demands away from the knee extensors to the hip during functional tasks. However, it is not clear how quadriceps strength deficits may affect hip strength. Therefore, the purpose of this study was to investigate differences in lower extremity strength in individuals with ACL reconstruction with differing levels of quadriceps strength asymmetry. Isometric strength was recorded bilaterally in 135 participants (73 control and 62 with unilateral ACL reconstruction, time from surgery = 30.9 ± 17.6 months) from the knee extensors and flexors, hip extensors and abductors, and hip internal and external rotator muscle groups. Symmetry indices (limb symmetry index (LSI)) were created based on quadriceps strength, and subjects with ACL reconstruction were subdivided (high quadriceps (LSI ≥ 90%), n = 37; low quadriceps (LSI < 85%), n = 18). Individual group (control vs high quadriceps vs low quadriceps) by limb (reconstructed/nondominant vs healthy/dominant) repeated-measures ANOVA was used to compare strength (%BW) for each of the six joint motions of interest (knee extensors/flexors, hip abductors/extensors/external, and internal rotators) while controlling for time from surgery. An interaction was observed for quadriceps strength (P < 0.001), and the reconstructed limb in the low quadriceps group was weaker than all other limbs. A main effect for group was observed with the low quadriceps group having greater hip extension (P = 0.007) strength in both limbs compared with the other groups. Knee flexion strength was weaker in the reconstructed limb of the high quadriceps group (P = 0.047) compared with all other groups and limbs. Individuals with ACL reconstruction and involved limb quadriceps weakness have greater hip extension strength in both limbs compared with patients with bilateral strength symmetry and controls.

Monitoring auditory cortical plasticity in hearing aid users with long latency auditory evoked potentials: a longitudinal study.

PubMed

Leite, Renata Aparecida; Magliaro, Fernanda Cristina Leite; Raimundo, Jeziela Cristina; Bento, Ricardo Ferreira; Matas, Carla Gentile

2018-02-19

The objective of this study was to compare long-latency auditory evoked potentials before and after hearing aid fittings in children with sensorineural hearing loss compared with age-matched children with normal hearing. Thirty-two subjects of both genders aged 7 to 12 years participated in this study and were divided into two groups as follows: 14 children with normal hearing were assigned to the control group (mean age 9 years and 8 months), and 18 children with mild to moderate symmetrical bilateral sensorineural hearing loss were assigned to the study group (mean age 9 years and 2 months). The children underwent tympanometry, pure tone and speech audiometry and long-latency auditory evoked potential testing with speech and tone burst stimuli. The groups were assessed at three time points. The study group had a lower percentage of positive responses, lower P1-N1 and P2-N2 amplitudes (speech and tone burst), and increased latencies for the P1 and P300 components following the tone burst stimuli. They also showed improvements in long-latency auditory evoked potentials (with regard to both the amplitude and presence of responses) after hearing aid use. Alterations in the central auditory pathways can be identified using P1-N1 and P2-N2 amplitude components, and the presence of these components increases after a short period of auditory stimulation (hearing aid use). These findings emphasize the importance of using these amplitude components to monitor the neuroplasticity of the central auditory nervous system in hearing aid users.

Monitoring auditory cortical plasticity in hearing aid users with long latency auditory evoked potentials: a longitudinal study

PubMed Central

Leite, Renata Aparecida; Magliaro, Fernanda Cristina Leite; Raimundo, Jeziela Cristina; Bento, Ricardo Ferreira; Matas, Carla Gentile

2018-01-01

OBJECTIVE: The objective of this study was to compare long-latency auditory evoked potentials before and after hearing aid fittings in children with sensorineural hearing loss compared with age-matched children with normal hearing. METHODS: Thirty-two subjects of both genders aged 7 to 12 years participated in this study and were divided into two groups as follows: 14 children with normal hearing were assigned to the control group (mean age 9 years and 8 months), and 18 children with mild to moderate symmetrical bilateral sensorineural hearing loss were assigned to the study group (mean age 9 years and 2 months). The children underwent tympanometry, pure tone and speech audiometry and long-latency auditory evoked potential testing with speech and tone burst stimuli. The groups were assessed at three time points. RESULTS: The study group had a lower percentage of positive responses, lower P1-N1 and P2-N2 amplitudes (speech and tone burst), and increased latencies for the P1 and P300 components following the tone burst stimuli. They also showed improvements in long-latency auditory evoked potentials (with regard to both the amplitude and presence of responses) after hearing aid use. CONCLUSIONS: Alterations in the central auditory pathways can be identified using P1-N1 and P2-N2 amplitude components, and the presence of these components increases after a short period of auditory stimulation (hearing aid use). These findings emphasize the importance of using these amplitude components to monitor the neuroplasticity of the central auditory nervous system in hearing aid users. PMID:29466495

Quadriceps Strength Asymmetry Following ACL Reconstruction Alters Knee Joint Biomechanics and Functional Performance at Time of Return to Activity

PubMed Central

Palmieri-Smith, RM; Lepley, LK

2016-01-01

Background Quadriceps strength deficits are observed clinically following anterior cruciate injury and reconstruction and are often not overcome despite rehabilitation. Given that quadriceps strength may be important for achieving symmetrical joint biomechanics and promoting long-term joint health, determining the magnitude of strength deficits that lead to altered mechanics is critical. Purpose To determine if the magnitude of quadriceps strength asymmetry alters knee and hip biomechanical symmetry, as well as functional performance and self-reported function. Study Design Cross-Sectional study. Methods Seventy-three patients were tested at the time they were cleared for return to activity following ACL reconstruction. Quadriceps strength and activation, scores on the International Knee Documentation Committee form, the hop for distance test, and sagittal plane lower extremity biomechanics were recorded while patients completed a single-legged hop. Results Patients with high and moderate quadriceps strength symmetry had larger central activation ratios as well as greater limb symmetry indices on the hop for distance compared to patients with low quadriceps strength symmetry (P<0.05). Similarly, knee flexion angle and external moment symmetry was higher in the patients with high and moderate quadriceps symmetry compared to those with low symmetry (P<0.05). Quadriceps strength was found to be associated with sagittal plane knee angle and moment symmetry (P<0.05). Conclusion Patients with low quadriceps strength displayed greater movement asymmetries at the knee in the sagittal plane. Quadriceps strength was related to movement asymmetries and functional performance. Rehabilitation following ACL reconstruction needs to focus on maximizing quadriceps strength, which likely will lead to more symmetrical knee biomechanics. PMID:25883169

Contribution of hamstring fatigue to quadriceps inhibition following lumbar extension exercise.

PubMed

Hart, Joseph M; Kerrigan, D Casey; Fritz, Julie M; Saliba, Ethan N; Gansneder, Bruce; Ingersoll, Christopher D

2006-01-01

The purpose of this study was to determine the contribution of hamstrings and quadriceps fatigue to quadriceps inhibition following lumbar extension exercise. Regression models were calculated consisting of the outcome variable: quadriceps inhibition and predictor variables: change in EMG median frequency in the quadriceps and hamstrings during lumbar fatiguing exercise. Twenty-five subjects with a history of low back pain were matched by gender, height and mass to 25 healthy controls. Subjects performed two sets of fatiguing isometric lumbar extension exercise until mild (set 1) and moderate (set 2) fatigue of the lumbar paraspinals. Quadriceps and hamstring EMG median frequency were measured while subjects performed fatiguing exercise. A burst of electrical stimuli was superimposed while subjects performed an isometric maximal quadriceps contraction to estimate quadriceps inhibition after each exercise set. Results indicate the change in hamstring median frequency explained variance in quadriceps inhibition following the exercise sets in the history of low back pain group only. Change in quadriceps median frequency explained variance in quadriceps inhibition following the first exercise set in the control group only. In conclusion, persons with a history of low back pain whose quadriceps become inhibited following lumbar paraspinal exercise may be adapting to the fatigue by using their hamstring muscles more than controls. Key PointsA neuromuscular relationship between the lumbar paraspinals and quadriceps while performing lumbar extension exercise may be influenced by hamstring muscle fatigue.QI following lumbar extension exercise in persons with a history of LBP group may involve significant contribution from the hamstring muscle group.More hamstring muscle contribution may be a necessary adaptation in the history of LBP group due to weaker and more fatigable lumbar extensors.

The Relation Between Stretching Typology and Stretching Duration: The Effects on Range of Motion.

PubMed

Thomas, Ewan; Bianco, Antonino; Paoli, Antonio; Palma, Antonio

2018-04-01

Different stretching strategies and protocols are widely used to improve flexibility or maintain health, acting on the muscle tendon-unit, in order to improve the range of motion (ROM) of the joints. This review aims to evaluate the current body of literature in order to understand the relation between stretching typology and ROM, and secondly to evaluate if a relation exists between stretching volume (either as a single training session, weekly training and weekly frequency) and ROM, after long-term stretching. Twenty-three articles were considered eligible and included in the quantitative synthesis. All stretching typologies showed ROM improvements over a long-term period, however the static protocols showed significant gains (p<0.05) when compared to the ballistic or PNF protocols. Time spent stretching per week seems fundamental to elicit range of movement improvements when stretches are applied for at least or more than 5 min, whereas the time spent stretching within a single session does not seem to have significant effects for ROM gains. Weekly frequency is positively associated to ROM. Evaluated data indicates that performing stretching at least 5 days a week for at least 5 min per week using static stretching may be beneficial to promote ROM improvements. © Georg Thieme Verlag KG Stuttgart · New York.

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

PubMed

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

2018-06-01

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

Anticonvulsant Effects of Fractions Isolated from Dinoponera quadriceps (Kempt) Ant Venom (Formicidae: Ponerinae).

PubMed

Nôga, Diana Aline Morais Ferreira; Brandão, Luiz Eduardo Mateus; Cagni, Fernanda Carvalho; Silva, Delano; de Azevedo, Dina Lilia Oliveira; Araújo, Arrilton; Dos Santos, Wagner Ferreira; Miranda, Antonio; da Silva, Regina Helena; Ribeiro, Alessandra Mussi

2016-12-23

Natural products, sources of new pharmacological substances, have large chemical diversity and architectural complexity. In this context, some toxins obtained from invertebrate venoms have anticonvulsant effects. Epilepsy is a neurological disorder that affects about 65 million people worldwide, and approximately 30% of cases are resistant to pharmacological treatment. Previous studies from our group show that the denatured venom of the ant Dinoponera quadriceps (Kempt) protects mice against bicuculline (BIC)-induced seizures and death. The aim of this study was to investigate the anticonvulsant activity of compounds isolated from D. quadriceps venom against seizures induced by BIC in mice. Crude venom was fractionated by high-performance liquid chromatography (HPLC) resulting in six fractions referred to as DqTx1-DqTx6. A liquid chromatography-mass spectrometry (LC/MS) analysis revealed a major 431 Da compound in fractions DqTx1 and DqTx2. Fractions DqTx3 and DqTx4 showed a compound of 2451 Da and DqTx5 revealed a 2436 Da compound. Furthermore, the DqTx6 fraction exhibited a major component with a molecular weight of 13,196 Da. Each fraction (1 mg/mL) was microinjected into the lateral ventricle of mice, and the animals were observed in an open field. We did not observe behavioral alterations when the fractions were given alone. Conversely, when the fractions were microinjected 20 min prior to the administration of BIC (21.6 nM), DqTx1, DqTx4, and DqTx6 fractions increased the latency for onset of tonic-clonic seizures. Moreover, all fractions, except DqTx5, increased latency to death. The more relevant result was obtained with the DqTx6 fraction, which protected 62.5% of the animals against tonic-clonic seizures. Furthermore, this fraction protected 100% of the animals from seizure episodes followed by death. Taken together, these findings indicate that compounds from ant venom might be a potential source of new anticonvulsants molecules.

Source analysis of short and long latency vestibular-evoked potentials (VsEPs) produced by left vs. right ear air-conducted 500 Hz tone pips.

PubMed

Todd, N P M; Paillard, A C; Kluk, K; Whittle, E; Colebatch, J G

2014-06-01

Todd et al. (2014) have recently demonstrated the presence of vestibular dependent changes both in the morphology and in the intensity dependence of auditory evoked potentials (AEPs) when passing through the vestibular threshold as determined by vestibular evoked myogenic potentials (VEMPs). In this paper we extend this work by comparing left vs. right ear stimulation and by conducting a source analysis of the resulting evoked potentials of short and long latency. Ten healthy, right-handed subjects were recruited and evoked potentials were recorded to both left- and right-ear sound stimulation, above and below vestibular threshold. Below VEMP threshold, typical AEPs were recorded, consisting of mid-latency (MLR) waves Na and Pa followed by long latency AEPs (LAEPs) N1 and P2. In the supra-threshold condition, the expected changes in morphology were observed, consisting of: (1) short-latency vestibular evoked potentials (VsEPs) which have no auditory correlate, i.e. the ocular VEMP (OVEMP) and inion response related potentials; (2) a later deflection, labelled N42/P52, followed by the LAEPs N1 and P2. Statistical analysis of the vestibular dependent responses indicated a contralateral effect for inion related short-latency responses and a left-ear/right-hemisphere advantage for the long-latency responses. Source analysis indicated that the short-latency effects may be mediated by a contralateral projection to left cerebellum, while the long-latency effects were mediated by a contralateral projection to right cingulate cortex. In addition we found evidence of a possible vestibular contribution to the auditory T-complex in radial temporal lobe sources. These last results raise the possibility that acoustic activation of the otolith organs could potentially contribute to auditory processing. Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.

Maturation of long latency auditory evoked potentials in hearing children: systematic review.

PubMed

Silva, Liliane Aparecida Fagundes; Magliaro, Fernanda Cristina Leite; Carvalho, Ana Claudia Martinho de; Matas, Carla Gentile

2017-05-15

To analyze how Auditory Long Latency Evoked Potentials (LLAEP) change according to age in children population through a systematic literature review. After formulation of the research question, a bibliographic survey was done in five data bases with the following descriptors: Electrophysiology (Eletrofisiologia), Auditory Evoked Potentials (Potenciais Evocados Auditivos), Child (Criança), Neuronal Plasticity (Plasticidade Neuronal) and Audiology (Audiologia). Level 1 evidence articles, published between 1995 and 2015 in Brazilian Portuguese or English language. Aspects related to emergence, morphology and latency of P1, N1, P2 and N2 components were analyzed. A total of 388 studies were found; however, only 21 studies contemplated the established criteria. P1 component is characterized as the most frequent component in young children, being observed around 100-150 ms, which tends to decrease as chronological age increases. The N2 component was shown to be the second most commonly observed component in children, being observed around 200-250 ms.. The other N1 and P2 components are less frequent and begin to be seen and recorded throughout the maturational process. The maturation of LLAEP occurs gradually, and the emergence of P1, N1, P2 and N2 components as well as their latency values are variable in childhood. P1 and N2 components are the most observed and described in pediatric population. The diversity of protocols makes the comparison between studies difficult.

Electromyographic analysis of a modified maneuver for quadriceps femoris muscle setting with co-contraction of the hamstrings.

PubMed

Nakajima, Masaaki; Kawamura, Kenji; Takeda, Isao

2003-05-01

A "quadriceps femoris muscle setting" is isometric quadriceps femoris exercise which can be widely used in early knee rehabilitation. However this exercise cannot obtain enough co-contraction of the hamstrings. Isolated quadriceps femoris contraction in knee extension imposes severe strain to anterior cruciate ligament. We succeeded in developing a simple training maneuver that is effective in obtaining co-contraction of the hamstrings--a modified maneuver for the quadriceps femoris muscle setting with the contralateral lower limb raised (MQS). In this study, we analyzed the effect of this maneuver by EMG quantification. Twenty-eight healthy young adult men performed sequential trials consisting of normal quadriceps femoris muscle setting (NQS) and MQS. Electromyographic activity was recorded from surface electrodes on the gluteus maximus, vastus medialis, rectus femoris, vastus lateralis, semitendinosus and biceps femoris (long head), and normalized to values derived from maximal isometric trials. The % maximal voluntary isometric contraction (%MVIC) of the vastus medialis, vastus lateralis and rectus femoris did not vary in the each maneuver. However, the %MVIC of the hamstrings varied significantly in the MQS. This study suggests that effective co-contraction of the hamstrings can be obtained in MQS by adjusting the load to the raised lower limb.

Quadriceps oxygenation during isometric exercise in sailing.

PubMed

Vogiatzis, I; Tzineris, D; Athanasopoulos, D; Georgiadou, O; Geladas, N

2008-01-01

The aim of the present study was to investigate why blood lactate after prolonged quadriceps contraction during hiking is only marginally increased. Eight sailors performed five 3-min hiking bouts interspersed with 5-s recovery periods. Whole body oxygen uptake, heart rate and lactate were recorded, along with continuous-wave near-infrared spectroscopy measures of quadriceps oxygenation. The time for 50% re-oxygenation was also assessed as an indication of the degree of localized oxygen delivery stress. Hiking elicited a significant (p = 0.001) increase in mean (+/- SD) heart rate (124 +/- 10 beats . min (-1)) which was accompanied by a disproportionately low oxygen uptake (12 +/- 2 ml.kg(-1).min(-1)). Lactate was significantly (p = 0.001) increased throughout hiking manoeuvres, though post-exercise it remained low (3.2 +/- 0.9 mmol.l(-1)). During the hiking bouts mean quadriceps oxygenation was significantly (p = 0.001) reduced compared to baseline (by 33 +/- 5%), indicating an imbalance between muscle oxygen accessibility and oxygen demand. During rest intervals quadriceps oxygenation was partially restored. After the end of the final bout the time for 50 % re-oxygenation was only 8 +/- 2 s, whereas recovery of quadriceps oxygenation and oxygen uptake was completed within 3 min. We conclude that the observed low lactate could be attributed to the small oxygen and energy deficits during hiking as the muscles' oxygen accessibility is presumably partially restored during the brief rest intervals.

Quadriceps Strength Asymmetry After Anterior Cruciate Ligament Reconstruction Alters Knee Joint Biomechanics and Functional Performance at Time of Return to Activity.

PubMed

Palmieri-Smith, Riann M; Lepley, Lindsey K

2015-07-01

Quadriceps strength deficits are observed clinically after anterior cruciate ligament (ACL) injury and reconstruction and are often not overcome despite rehabilitation. Given that quadriceps strength may be important for achieving symmetrical joint biomechanics and promoting long-term joint health, determining the magnitude of strength deficits that lead to altered mechanics is critical. To determine if the magnitude of quadriceps strength asymmetry alters knee and hip biomechanical symmetry as well as functional performance and self-reported function. Cross-sectional study; Level of evidence, 3. A total of 73 patients were tested at the time they were cleared for return to activity after ACL reconstruction. Quadriceps strength and activation, scores on the International Knee Documentation Committee form, the hop for distance test, and sagittal plane lower extremity biomechanics were recorded while patients completed a single-legged hop. Patients with high and moderate quadriceps strength symmetry had larger central activation ratios as well as greater limb symmetry indices on the hop for distance compared with patients with low quadriceps strength symmetry (P < .05). Similarly, knee flexion angle and external moment symmetry were higher in the patients with high and moderate quadriceps symmetry compared with those with low symmetry (P < .05). Quadriceps strength was found to be associated with sagittal plane knee angle and moment symmetry (P < .05). Patients with low quadriceps strength displayed greater movement asymmetries at the knee in the sagittal plane. Quadriceps strength was related to movement asymmetries and functional performance. Rehabilitation after ACL reconstruction needs to focus on maximizing quadriceps strength, which likely will lead to more symmetrical knee biomechanics. © 2015 The Author(s).

Quadriceps combined with hip abductor strengthening versus quadriceps strengthening in treating knee osteoarthritis: a study protocol for a randomized controlled trial.

PubMed

Xie, Yujie; Zhang, Chi; Jiang, Wei; Huang, Juan; Xu, Lili; Pang, Guoyin; Tang, Haiyan; Chen, Ruyan; Yu, Jihua; Guo, Shengmin; Xu, Fangyuan; Wang, Jianxiong

2018-05-15

Lower limb strengthening, especially the quadriceps training, is of much necessity for patients with knee osteoarthritis (KOA). Previous studies suggest that strengthening of the hip muscles, especially the hip abductor, can potentially relieve the KOA-associated symptoms. Nevertheless, the effects of quadriceps combined with hip abductor strengthening remain unclear. Therefore, the current randomized controlled trial is designed aiming to observe whether quadriceps in combination with hip abductor strengthening can better improve the function and reduce pain in KOA patients than quadriceps training alone. A total of 80 subjects with symptomatic KOA will be recruited from the communities and hospital outpatient, and will be randomly assigned to the experiment group (Quadriceps-plus-hip-abductor-strengthening) or the control group (Quadriceps-strengthening). Specifically, participants in the experiment group will complete 4 exercises to train the quadriceps and hip abductor twice a day for 6 weeks at home, while those in the control group will only perform 2 exercises to strengthen the quadriceps. Besides, all patients will also receive usual care management, including health education and physical agent therapy when necessary. Knee pain will be measured using the Visual Analogue Scale (VAS) at baseline, in every week during the course of treatment, as well as 8 and 12 weeks after randomization. Furthermore, knee function will be measured using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scale, and the quality of life will be measured using the MOS Item Short-form Health Survey (SF-36). In this study, several simple tests will be applied to assess the objective function. All the assessments except for VAS will be carried out at baseline, and in the 6th, 8th and 12th weeks respectively. Our findings will provide more evidence for the effects of hip abductor strengthening on relieving pain and improving function in KOA patients. Hip

Intermittent But Not Continuous Static Stretching Improves Subsequent Vertical Jump Performance In Flexibility-Trained Athletes.

PubMed

Bogdanis, Gregory C; Donti, Olyvia; Tsolakis, Charilaos; Smilios, Ilias; Bishop, David J

2017-02-23

This study examined changes in countermovement jump (CMJ) height after an intermittent or a continuous static stretching protocol of equal total duration. Sixteen male, elite-level gymnasts performed 90 s of intermittent (3 x 30 s with 30 s rest) or continuous stretching (90 s) of the quadriceps muscle. A single-leg stretching and jumping design was used, with the contra-lateral limb serving as a control. The same individuals performed both conditions with alternate legs in a randomized, counterbalanced order. One leg CMJ height was measured for the stretched and the control leg after warm-up, immediately after stretching, and at regular intervals for 10 min after stretching. Range of motion (ROM) of the hip and knee joints was measured before, after, and 10 min post-stretching. Compared to the control leg, intermittent stretching increased CMJ height by 8.1±2.0%, 4 min into recovery (+2.2±2.0 cm, 95%CI: 1.0-3.4 cm, p=0.001), while continuous stretching decreased CMJ height by 17.5±3.3% immediately after (-2.9±1.7 cm, 95%CI: -2.0 to -3.7 cm, p=0.001) and by 12.0±2.7% one min after stretching (-2.2±2.1 cm, 95%CI: -1.2 to -3.2 cm, p=0.001). The increases in hip (2.9 and 3.6, p=0.001. d=2.4) and knee joint ROM (5.1 and 6.1, p=0.001. d=0.85) after the intermittent and continuous stretching protocols were not different. The opposite effects of intermittent vs. continuous stretching on subsequent CMJ performance suggests that stretching mode is an important variable when examining the acute effects of static stretching on performance in flexibility-trained athletes.

In vivo Knock-down of the HSV-1 Latency-Associated Transcript Reduces Reactivation from Latency.

PubMed

Watson, Zachary L; Washington, Shannan D; Phelan, Dane M; Lewin, Alfred S; Tuli, Sonal S; Schultz, Gregory S; Neumann, Donna M; Bloom, David C

2018-06-06

During Herpes Simplex Virus (HSV) latency, most viral genes are silenced with the exception of one region of the genome encoding the latency-associated transcript (LAT). This long non-coding RNA was originally described as having a role in enhancing HSV-1 reactivation. However, subsequent evidence showing that the LAT blocked apoptosis and promoted efficient establishment of latency suggested that its effects on reactivation were secondary to establishment. Here, we utilize an Adeno-associated Virus (AAV) vector to deliver a LAT-targeting hammerhead ribozyme to HSV-1-infected neurons of rabbits after the establishment of HSV-1 latency. The rabbits were then induced to reactivate latent HSV-1. Using this model, we show that decreasing LAT levels in neurons following the establishment of latency reduced the ability of the virus to reactivate. This demonstrates that the HSV-1 LAT RNA has a role in reactivation that is independent of its function in establishment of latency. In addition these results suggest the potential of AAV vectors expressing LAT-targeting ribozymes as a potential therapy for recurrent HSV disease such as herpes stromal keratitis, a leading cause of infectious blindness. Importance Herpes Simplex Virus (HSV) establishes a life long infection and remains dormant (latent) in our nerve cells. Occasionally HSV reactivates to cause disease, with HSV-1 typically causing cold sores whereas HSV-2 is the most common cause of genital herpes. The details of how HSV reactivates are largely unknown. Most of HSV's genes are silent during latency with the exception of RNAs made from the latency-associated transcript (LAT) region. While viruses that make less LAT do not reactivate efficiently, these viruses also do not establish latency as efficiently. Here we deliver a ribozyme that can degrade the LAT to the nerve cells of latently infected rabbits using a gene therapy vector. We show that this treatment blocks reactivation in the majority of the rabbits. This

Latency in Distributed Acquisition and Rendering for Telepresence Systems.

PubMed

Ohl, Stephan; Willert, Malte; Staadt, Oliver

2015-12-01

Telepresence systems use 3D techniques to create a more natural human-centered communication over long distances. This work concentrates on the analysis of latency in telepresence systems where acquisition and rendering are distributed. Keeping latency low is important to immerse users in the virtual environment. To better understand latency problems and to identify the source of such latency, we focus on the decomposition of system latency into sub-latencies. We contribute a model of latency and show how it can be used to estimate latencies in a complex telepresence dataflow network. To compare the estimates with real latencies in our prototype, we modify two common latency measurement methods. This presented methodology enables the developer to optimize the design, find implementation issues and gain deeper knowledge about specific sources of latency.

Different Muscle Action Training Protocols on Quadriceps-Hamstrings Neuromuscular Adaptations.

PubMed

Ruas, Cassio V; Brown, Lee E; Lima, Camila D; Gregory Haff, G; Pinto, Ronei S

2018-05-01

The aim of this study was to compare three specific concentric and eccentric muscle action training protocols on quadriceps-hamstrings neuromuscular adaptations. Forty male volunteers performed 6 weeks of training (two sessions/week) of their dominant and non-dominant legs on an isokinetic dynamometer. They were randomly assigned to one of four groups; concentric quadriceps and concentric hamstrings (CON/CON, n=10), eccentric quadriceps and eccentric hamstrings (ECC/ECC, n=10), concentric quadriceps and eccentric hamstrings (CON/ECC, n=10), or no training (CTRL, n=10). Intensity of training was increased every week by decreasing the angular velocity for concentric and increasing it for eccentric groups in 30°/s increments. Volume of training was increased by adding one set every week. Dominant leg quadriceps and hamstrings muscle thickness, muscle quality, muscle activation, muscle coactivation, and electromechanical delay were tested before and after training. Results revealed that all training groups similarly increased MT of quadriceps and hamstrings compared to control (p<0.05). However, CON/ECC and ECC/ECC training elicited a greater magnitude of change. There were no significant differences between groups for all other neuromuscular variables (p>0.05). These findings suggest that different short-term muscle action isokinetic training protocols elicit similar muscle size increases in hamstrings and quadriceps, but not for other neuromuscular variables. Nevertheless, effect sizes indicate that CON/ECC and ECC/ECC may elicit the greatest magnitude of change in muscle hypertrophy. © Georg Thieme Verlag KG Stuttgart · New York.

Quadriceps muscle strength and voluntary activation after polio.

PubMed

Beelen, Anita; Nollet, Frans; de Visser, Marianne; de Jong, Bareld A; Lankhorst, Gustaaf J; Sargeant, Anthony J

2003-08-01

Quadriceps strength, maximal anatomical cross-sectional area (CSA), maximal voluntary activation (MVA), and maximal relaxation rate (MRR) were studied in 48 subjects with a past history of polio, 26 with and 22 without postpoliomyelitis syndrome (PPS), and in 13 control subjects. It was also investigated whether, apart from CSA, MVA and MRR were determinants of muscle strength. Polio subjects had significantly less strength, CSA, and MRR in the more-affected quadriceps than control subjects. MVA was reduced in 18 polio subjects and normal in all controls. PPS subjects differed from non-PPS subjects only in that the MVA of the more-affected quadriceps was significantly lower. Both CSA and MVA were found to be associated with muscle strength. Quadriceps strength in polio subjects was dependent not only on muscle mass, but also on the ability to activate the muscles. Since impaired activation was more pronounced in PPS subjects, the new muscle weakness and functional decline in PPS may be due not only to a gradual loss of muscle fibers, but also to an increasing inability to activate the muscles.

Loss of motor unit size and quadriceps strength over 10 years in post-polio syndrome.

PubMed

Bickerstaffe, A; van Dijk, J P; Beelen, A; Zwarts, M J; Nollet, F

2014-06-01

To investigate whether strength decline in post-polio syndrome (PPS) results from excessive distal axonal degeneration of enlarged motor units. We assessed changes over 10 years in isometric quadriceps strength, mean motor unit action potential (MUAP) size, root mean squared (RMS) amplitude, and level of interference (LOI) in 47 patients with PPS and 12 healthy controls, using high density surface EMG. At baseline, all patients had symptomatic quadriceps dysfunction, evidenced by transmission defects on single-fibre EMG. MU size and strength declined significantly by 20% and 15%, respectively in patients with PPS. Those with the largest initial MU sizes exhibited the greatest losses of mean MU size (27%) and proportional decreases in quadriceps strength (23%). Initial strength, change in LOI and change in RMS amplitude together explained 35% of the variability in strength changes in patients. MU size of controls did not change, although they lost 29% strength. MU size and strength declined concomitantly in a homogeneous cohort of patients with PPS and quadriceps dysfunction. This long term follow-up study provides evidence that size diminution of enlarged MUs combined with a reduced number of active MUs contributes to the gradual strength decline in PPS. Copyright © 2013 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

The effects of different durations of static stretching within a comprehensive warm-up on voluntary and evoked contractile properties.

PubMed

Reid, Jonathan C; Greene, Rebecca; Young, James D; Hodgson, Daniel D; Blazevich, Anthony J; Behm, David G

2018-05-02

Evidence for performance decrements following prolonged static stretching (SS) has led to a paradigm shift in stretching routines within a warm-up. Rather than SS, dynamic stretching (DS) and dynamic activity (DA) have replaced SS within warm-up routines. The objective of the present study was to compare the effect of differing lower limb SS durations (30 [SS30s], 60 [SS60s] or 120 s [SS120s] of SS per muscle group or no-stretch control) within a comprehensive warm-up protocol consisting of aerobic activity, DS and DA. Sixteen male participants completed the four stretching conditions in a randomized order, after a 5-min low-intensity (cycle) warm-up and before a DS/DA component on separate days. Tests included passive hip and knee ranges of motion (ROM), maximum voluntary knee extensor/flexor force, force produced at 100 ms (F100), vertical jump height and evoked knee extensor contractile properties. For hip flexion (hamstrings) ROM, SS120s provided the largest increase (5.6-11.7%) followed by SS60s (4.3-11.4%), control (4.4-10.6%) and SS30s (3.6-11.1%). For knee flexion (quadriceps) ROM, SS30s provided the largest increase (9.3-18.2%) followed by SS120s (6.5-16.3%), SS60s (7.2-15.2%) and control (6.3-15.2%). There were decreases in quadriceps F100 following SS in SS120s (29.6%) only. There were increases in vertical jump performance in the control (6.2%), SS60s (4.6%) and SS30s (3.3%). While 120 s SS per muscle increased ROM, even within a comprehensive warm-up routine, it also elicited notable performance decrements. However, moderate durations of SS were observed to improve ROM whilst either having negligible or beneficial (but not detrimental) effects on specific aspects of athletic performance.

Quadriceps muscle use in the flywheel and barbell squat.

PubMed

Norrbrand, Lena; Tous-Fajardo, Julio; Vargas, Roberto; Tesch, Per A

2011-01-01

Resistance exercise has been proposed as an aid to counteract quadriceps muscle atrophy in astronauts during extended missions in orbit. While space authorities have advocated the squat exercise should be prescribed, no exercise system suitable for in-flight use has been validated with regard to quadriceps muscle use. We compared muscle involvement in the terrestrial "gold standard" squat using free weights and a nongravity dependent flywheel resistance exercise device designed for use in space. The subjects were 10 strength-trained men who performed 5 sets of 10 repetitions using the barbell squat (BS; 10 repetition maximum) or flywheel squat (FS; each repetition maximal), respectively. Functional magnetic resonance imaging (MRI) and surface electromyography (EMG) techniques assessed quadriceps muscle use. Exercise-induced contrast shift of MR images was measured by means of transverse relaxation time (T2). EMG root mean square (RMS) was measured during concentric (CON) and eccentric (ECC) actions and normalized to EMG RMS determined during maximal voluntary contraction. The quadriceps muscle group showed greater exercise-induced T2 increase following FS compared with BS. Among individual muscles, the rectus femoris displayed greater T2 increase with FS (+24 +/- 14%) than BS (+8 +/- 4%). Normalized quadriceps EMG showed no difference across exercise modes. Collectively, the results of this study suggest that quadriceps muscle use in the squat is comparable, if not greater, with flywheel compared with free weight resistance exercise. Data appear to provide support for use of flywheel squat resistance exercise as a countermeasures adjunct during spaceflight.

Quadriceps Function and Knee Joint Ultrasonography after ACL Reconstruction.

PubMed

Pamukoff, Derek N; Montgomery, Melissa M; Moffit, Tyler J; Vakula, Michael N

2018-02-01

Individuals with anterior cruciate ligament reconstruction (ACLR) are at greater risk for knee osteoarthritis, partially because of chronic quadriceps dysfunction. Articular cartilage is commonly assessed using magnetic resonance imaging and radiography, but these methods are expensive and lack portability. Ultrasound imaging may provide a cost-effective and portable alternative for imaging the femoral cartilage. The purpose of this study was to compare ultrasonography of the femoral cartilage between the injured and uninjured limbs of individuals with unilateral ACLR, and to examine the association between quadriceps function and ultrasonographic measures of femoral cartilage. Bilateral femoral cartilage thickness and quadriceps function were assessed in 44 individuals with unilateral ACLR. Quadriceps function was assessed using peak isometric strength, and early (RTD100) and late (RTD200) rate of torque development. Cartilage thickness at the medial femoral condyle (P < 0.001) and femoral cartilage cross-sectional area (P = 0.007) were smaller in the injured compared with the uninjured limb. After accounting for time since ACLR, quadriceps peak isometric strength was associated with cartilage thickness at the medial femoral condyle (r = 0.35, P = 0.02) and femoral cartilage cross-sectional area (r = 0.28, P = 0.04). RTD100 and RTD200 were not associated with femoral cartilage thickness or cross-sectional area. Individuals with ACLR have thinner cartilage in their injured limb compared with uninjured limb, and cartilage thickness is associated with quadriceps function. These results indicate that ultrasonography may be useful for monitoring cartilage health and osteoarthritis progression after ACLR.

Long Latency Auditory Evoked Potential in Term and Premature Infants

PubMed Central

Didoné, Dayane Domeneghini; Garcia, Michele Vargas; da Silveira, Aron Ferreira

2013-01-01

Introduction The research in long latency auditory evokes potentials (LLAEP) in newborns is recent because of the cortical structure maturation, but studies note that these potentials may be evidenced at this age and could be considered as indicators of cognitive development. Purpose To research the exogenous potentials in term and premature infants during their first month of life. Materials and Methods The sample consisted of 25 newborns, 15 term and 10 premature infants. The infants with gestational age under 37 weeks were considered premature. To evaluate the cortical potentials, the infants remained in natural sleep. The LLAEPs were researched binaurally, through insertion earphones, with frequent /ba/ and rare /ga/ speech stimuli in the intensity of 80 dB HL (decibel hearing level). The frequent stimuli presented a total of 80% of the presentations, and the rare, 20%. The data were statistically analyzed. Results The average gestational age of the term infants was 38.9 weeks (± 1.3) and for the premature group, 33.9 weeks (± 1.6). It was possible to observe only the potentials P1 and N1 in both groups, but there was no statistically significant difference for the latencies of the components P1 and N1 (p > 0.05) between the groups. Conclusion It was possible to observe the exogenous components P1 and N1 of the cortical potentials in both term and preterm newborns of no more than 1 month of age. However, there was no difference between the groups. PMID:25992057

Kinesiotape and quadriceps strengthening with elastic band in women with knee osteoarthritis and overweight or obesity. A randomized clinical trial.

PubMed

León-Ballesteros, Saúl; Espinosa-Morales, Rolando; Clark-Peralta, Patricia; Gómez-Pineda, Ascención Guadalupe; Guadarrama-Becerril, Jaime Horacio

2018-04-07

The beneficial effects of exercise in the treatment of Osteoarthritis (OA) of the knee have been verified in several studies. Kinesiotaping (KT) has been popularized due to its reducing local pressure and increasing circulation, resulting in decreased pain. Determine the clinical effectiveness of strengthening therapy with KT in women with knee OA for pain reduction. Thirty two women with knee OA, aged 50-70 years, with overweight or obesity grade I, who were randomized into two groups: one with exercise and KT, and the other, with exercise and placebo technique. Both groups performed stretching and quadriceps strengthening exercise with the elastic band 3 days weekly for 6 weeks. Measurement of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain subscale was taken as primary outcome. Stiffness and functionality of the same index and the Visual Analog Scale (VAS) for pain intensity were measured. At the end of the study, there were no significant differences between the groups. Both groups had a difference of 2.7 points with respect to the baseline measurement, change percentage of 32.2% and 31.1% for placebo and experimental respectively (p=0.2). KT plus quadriceps strengthening exercise does not offer advantages for improvement of pain compared with quadriceps strengthening exercise alone in knee OA. Copyright © 2018 Sociedad Espaola de Reumatologa y Colegio Mexicano de Reumatologa. Publicado por Elsevier España, S.L.U. All rights reserved.

Suture anchor repair of quadriceps tendon rupture after total knee arthroplasty.

PubMed

Kim, Tae Won B; Kamath, Atul F; Israelite, Craig L

2011-08-01

Disruption of the extensor mechanism after total knee arthroplasty (TKA) is a devastating complication, usually requiring surgical repair. Although suture anchor fixation is well described for repair of the ruptured native knee quadriceps tendon, no study has discussed the use of suture anchors in quadriceps repair after TKA. We present an illustrative case of successful suture anchor fixation of the quadriceps mechanism after TKA. The procedure has been performed in a total of 3 patients. A surgical technique and brief review of the literature follows. Suture anchor fixation of the quadriceps tendon is a viable option in the setting of rupture after TKA. Copyright © 2011 Elsevier Inc. All rights reserved.

Quadriceps Tendon Autograft Medial Patellofemoral Ligament Reconstruction.

PubMed

Fink, Christian; Steensen, Robert; Gföller, Peter; Lawton, Robert

2018-06-01

Critically evaluate the published literature related to quadriceps tendon (QT) medial patellofemoral ligament (MPFL) reconstruction. Hamstring tendon (HT) MPFL reconstruction techniques have been shown to successfully restore patella stability, but complications including patella fracture are reported. Quadriceps tendon (QT) reconstruction techniques with an intact graft pedicle on the patella side have the advantage that patella bone tunnel drilling and fixation are no longer needed, reducing risk of patella fracture. Several QT MPFL reconstruction techniques, including minimally invasive surgical (MIS) approaches, have been published with promising clinical results and fewer complications than with HT techniques. Parallel laboratory studies have shown macroscopic anatomy and biomechanical properties of QT are more similar to native MPFL than hamstring (HS) HT, suggesting QT may more accurately restore native joint kinematics. Quadriceps tendon MPFL reconstruction, via both open and MIS techniques, have promising clinical results and offer valuable alternatives to HS grafts for primary and revision MPFL reconstruction in both children and adults.

Quadriceps tendon injuries in national football league players.

PubMed

Boublik, Martin; Schlegel, Theodore F; Koonce, Ryan C; Genuario, James W; Kinkartz, Jason D

2013-08-01

Distal quadriceps tendon tears are uncommon injuries that typically occur in patients older than 40 years of age, and they have a guarded prognosis. Predisposing factors, prodromal findings, mechanisms of injury, treatment guidelines, and recovery expectations are not well described in high-level athletes. Professional American football players with an isolated tear of the quadriceps tendon treated with timely surgical repair will return to their sport. Case series; Level of evidence, 4. Fourteen unilateral distal quadriceps tendon tears were identified in National Football League (NFL) players from 1994 to 2004. Team physicians retrospectively reviewed training room and clinic records, operative notes, and imaging studies for each of these players. Data on each player were analyzed to identify variables predicting return to play. A successful outcome was defined as returning to play in regular-season NFL games. Eccentric contraction of the quadriceps was the most common mechanism of injury, occurring in 10 players. Only 1 player had antecedent ipsilateral extensor mechanism symptoms. Eleven players had a complete rupture of the quadriceps tendon, and 3 had partial tears. There were no associated knee injuries. All ruptures were treated with surgical repair, 1 of which was delayed after failure of nonoperative treatment. Fifty percent of players returned to play in regular-season NFL games. There was a trend toward earlier draft status for those who returned to play compared with those who did not (draft round, 3.1 ± 2.5 vs. 6.0 ± 2.9, respectively; P = .073). For those who returned to play, the average number of games after injury was 40.9 (range, 12-92). Quadriceps tendon tears are rare in professional American football players, and they usually occur from eccentric load on the extensor mechanism. Prodromal symptoms and predisposing factors are usually absent. Even with timely surgical repair, there is a low rate of return to play in regular-season games. There

Electromyography of the quadriceps in patellofemoral pain with patellar subluxation.

PubMed

Mohr, Karen J; Kvitne, Ronald S; Pink, Marilyn M; Fideler, Bradley; Perry, Jacquelin

2003-10-01

This study compared muscle activity and timing of gait phases during functional activities in 13 subjects with patellofemoral pain associated with lateral subluxation and in 11 subjects with healthy knees. Fine wire electromyography recorded activity in the vastus lateralis and vastus medialis oblique during walking and ascending and descending stairs. Subjects were filmed to divide the activities into phases and determine timing. The vastus medialis oblique and vastus lateralis had similar patterns during all activities. Subjects with patellofemoral pain had significantly increased activity in the vastus medialis oblique and vastus lateralis compared with the healthy subjects during the most demanding phases of the gait cycle, suggesting a generalized quadriceps weakness in the patients with patellofemoral pain. Timing differences were seen in walking and stair ascending with the subjects with patellofemoral pain spending significantly more time in stance compared with the healthy subjects. This may be an attempt to reduce the load on weak quadriceps. These data reflect a generalized quadriceps muscle weakness, rather than the prevailing theory of quadriceps muscle imbalance as an etiology of patellofemoral pain. Therefore, we support the practice of strengthening the entire quadriceps muscle group, rather than attempting to specifically target the vastus medialis oblique.

Disruption of quadriceps tendon after total knee arthroplasty: Case report of four cases.

PubMed

Soong, J W; Silva, A N; Andrew, Tan Hc

2017-01-01

Quadriceps tendon rupture after total knee arthroplasty (TKA) is a rare but dire complication. It is associated with adverse outcomes and morbidities. Studies on such complications are scarce in the literature. In this study, we share our experience in the management of four patients who sustained quadriceps tendon rupture in the early postoperative period. Efforts should be focused on prevention. Meticulous surgical techniques during the medial parapatellar approach to preserve the integrity of quadriceps can reduce the risk of rupture. The importance of prompt diagnosis is emphasized as delayed treatment may lead to poor outcomes. However, making a diagnosis can be challenging, as worsening of the quadriceps strength after TKA is expected because of the surgical approach that violates the quadriceps muscle. In an event of postoperative trauma with resultant extensor weakness, an ultrasound evaluation to exclude a quadriceps tendon rupture should be promptly performed after a fracture is excluded.

Effect of quadriceps and hamstrings muscle cooling on standing balance in healthy young men.

PubMed

Alghadir, A H; Anwer, S; Zafar, H; Al-Eisa, E S

2017-09-01

The present study compared the effect of quadriceps and hamstring muscle cooling on standing balance in healthy young men. Thirty healthy young men (18-30 years) participated in the study. The participants were randomly assigned to three groups (n=10 each): quadriceps cooling (QC), hamstring cooling (HC), or control group (no cooling). Participants in the QC and HC groups received 20 minutes of cooling using a cold pack (gel pack), placed on the anterior thigh (from the apex of the patella to the mid-thigh) and the posterior thigh (from the base of the popliteal fossa to the mid-thigh), respectively. Balance score including unilateral stance was measured at baseline and immediately after the application of the cold pack. No significant difference in the balance score was noted in any group after the application of the cold pack (p⟩0.05). Similarly, no significant differences in post-test balance score were noted among the three groups (p⟩0.05). Cooling of the quadriceps and hamstring muscles has no immediate effect on standing balance in healthy young men. However, longitudinal studies are warranted to investigate the long-term effects of cooling these muscles on standing balance.

Quadriceps intramuscular fat fraction rather than muscle size is associated with knee osteoarthritis

PubMed Central

Kumar, Deepak; Karampinos, Dimitrios C.; MacLeod, Toran D.; Lin, Wilson; Nardo, Lorenzo; Li, Xiaojuan; Link, Thomas M; Majumdar, Sharmila; Souza, Richard B

2014-01-01

Objectives To compare thigh muscle intramuscular fat (intraMF) fractions and area between people with and without knee radiographic osteoarthritis (ROA); and to evaluate the relationships of quadriceps adiposity and area with strength, function and knee MRI lesions. Methods Ninety six subjects (ROA: KL >1; n = 30, control: KL = 0,1; n = 66) underwent 3-Tesla MRI of the thigh muscles using chemical shift-based water/fat MR imaging (fat fractions) and the knee (clinical grading). Subjects were assessed for isometric/isokinetic quadriceps/hamstrings strength, function (KOOS, stair climbing test [SCT], and 6-minute walk test [(6MWT]. Thigh muscle intraMF fractions, muscle area and strength, and function were compared between controls and ROA subjects, adjusting for age. Relationships between measures of muscle fat/area with strength, function, KL and lesion scores were assessed using regression and correlational analyses. Results The ROA group had worse KOOS scores but SCT and 6MWT were not different. The ROA group had greater quadriceps intraMF fraction but not for other muscles. Quadriceps strength was lower in ROA group but the area was not different. Quadriceps intraMF fraction but not area predicted self-reported disability. Aging, worse KL, and cartilage and meniscus lesions were associated with higher quadriceps intraMF fraction. Conclusion Quadriceps intraMF is higher in people with knee OA and is related to symptomatic and structural severity of knee OA, where as the quadriceps area is not. Quadriceps fat fraction from chemical shift-based water/fat MR imaging may have utility as a marker of structural and symptomatic severity of knee OA disease process. PMID:24361743

[Neglected ipsilateral simultaneous ruptures of patellar and quadriceps tendon].

PubMed

Karahasanoğlu, İlker; Yoloğlu, Osman; Kerimoğlu, Servet; Turhan, Ahmet Uğur

2015-01-01

Neglected patellar and quadriceps tendon rupture is a rare injury, but ipsilateral simultaneous patellar and quadriceps tendon rupture was not described in the literature to our knowledge. In this article, we report a 40-year-old healthy male patient with neglected ipsilateral patellar and quadriceps tendon ruptures treated by peroneus longus tendon autograft. Patient had received some conservative and surgical treatments for patellar fracture before applying to our clinic. After our treatment using peroneus longus autograft and interference nails, patient was immobilized for six weeks in cylindrical cast. Flexion exercises and full weight bearing were started after cast removal. Patient had no complaint at postoperative second year. Patient was a neglected case. Surgical repair and early rehabilitation enabled us to achieve a satisfactory outcome.

Quadriceps strength, quadriceps power, and gait speed in older U.S. adults with diabetes mellitus: results from the National Health and Nutrition Examination Survey, 1999-2002.

PubMed

Kalyani, Rita Rastogi; Tra, Yolande; Yeh, Hsin-Chieh; Egan, Josephine M; Ferrucci, Luigi; Brancati, Frederick L

2013-05-01

To examine the independent association between diabetes mellitus (and its duration and severity) and quadriceps strength, quadriceps power, and gait speed in a national population of older adults. Cross-sectional nationally representative survey. United States. Two thousand five hundred seventy-three adults aged 50 and older in the National Health and Nutrition Examination Survey 1999-2002 who had assessment of quadriceps strength. Diabetes mellitus was ascertained according to questionnaire. Measurement of isokinetic knee extensor (quadriceps) strength was performed at 60º/s. Gait speed was assessed using a 20-foot walk test. Multiple linear regression analyses were used to assess the association between diabetes mellitus status and outcomes, adjusting for potential confounders or mediators. Older U.S. adults with diabetes mellitus had significantly slower gait speed (0.96 ± 0.02 m/s) than those without (1.08 ± 0.01 m/s; P < .001). After adjusting for demographic characteristics, weight, and height, diabetes mellitus was also associated with significantly lower quadriceps strength (-4.6 ± 1.9 Nm; P = .02) and power (-4.9 ± 2.0 W; P = .02) and slower gait speed (-0.05 ± 0.02 m/s; P = .002). Associations remained significant after adjusting for physical activity and C-reactive protein. After accounting for comorbidities (cardiovascular disease, peripheral neuropathy, amputation, cancer, arthritis, fracture, chronic obstructive pulmonary disease), diabetes mellitus was independently associated only with gait speed (-0.04 ± 0.02 m/s; P = .02). Diabetes mellitus duration in men and women was negatively associated with age-adjusted quadriceps strength (-5.7 and -3.5 Nm/decade of diabetes mellitus, respectively) and power (-6.1 and -3.8 W/decade of diabetes mellitus, respectively) (all P ≤ .001, no significant interactions according to sex). Glycosylated hemoglobin was not associated with outcomes after accounting for body weight. Older U.S. adults with diabetes

Central and peripheral quadriceps fatigue in congestive heart failure☆

PubMed Central

Hopkinson, Nicholas S.; Dayer, Mark J.; Antoine-Jonville, Sophie; Swallow, Elisabeth B.; Porcher, Raphael; Vazir, Ali; Poole-Wilson, Philip; Polkey, Michael I.

2013-01-01

Aims The clinical syndrome of heart failure includes exercise limitation that is not directly linked to measures of cardiac function. Quadriceps fatigability may be an important component of this and this may arise from peripheral or central factors. Methods and results We studied 10 men with CHF and 10 healthy age-matched controls. Compared with a rest condition, 10 min after incremental maximal cycle exercise, twitch quadriceps force in response to supramaximal magnetic femoral nerve stimulation fell in both groups (CHF 14.1% ± 18.1%, p = 0.037; Control: 20.8 ± 11.0%, p < 0.001; no significant difference between groups). There was no significant change in quadriceps maximum voluntary contraction voluntary force. The difference in the motor evoked potential (MEP) response to transcranial magnetic stimulation of the motor cortex between rest and exercise conditions at 10 min, normalised to the peripheral action potential, also fell significantly in both groups (CHF: 27.3 ± 38.7%, p = 0.037; Control: 41.1 ± 47.7%, p = 0.024). However, the fall in MEP was sustained for a longer period in controls than in patients (p = 0.048). Conclusions The quadriceps is more susceptible to fatigue, with a similar fall in TwQ occurring in CHF patients at lower levels of exercise. This is associated with no change in voluntary activation but a lesser degree of depression of quadriceps motor evoked potential. PMID:22795722

The evaluation of muscle recovery after anatomical single-bundle ACL reconstruction using a quadriceps autograft.

PubMed

Iriuchishima, Takanori; Ryu, Keinosuke; Okano, Tatsumasa; Suruga, Makoto; Aizawa, Shin; Fu, Freddie H

2017-05-01

The purpose of this study was to reveal the degree of muscle recovery and report the clinical results of anatomical single-bundle ACL reconstruction using a quadriceps autograft. Twenty subjects undergoing anatomical single-bundle ACL reconstruction using a quadriceps autograft were included in this study. A 5-mm-wide, 8-cm-long graft, involving the entire layer of the quadriceps tendon, was harvested without bone block. The average graft diameter was 8.1 ± 1.4 mm. An initial tension of 30 N was applied. The femoral tunnel was created from the far-medial portal. Each femoral and tibial tunnel was created close to the antero-medial bundle insertion site. For the evaluation of muscle recovery (quadriceps and hamstring), a handheld dynamometer was used. The evaluation of muscle recovery was performed pre-operatively, and at 3, 6, 9, and 12 months after surgery. Muscle recovery data were calculated as a percentage of leg strength in the non-operated leg. Anterior tibial translation (ATT), pivot shift test, and IKDC score were evaluated. The average quadriceps strength pre-operatively, and at 3, 6, 9, and 12 months after ACL reconstruction was 90.5 ± 19, 67.8 ± 21.4, 84 ± 17.5, and 85.1 ± 12.6 %, respectively. The average hamstring strength pre-operatively, and at 3, 6, 9, and 12 months after ACL reconstruction was 99.5 ± 13.7, 78.7 ± 11.4, 90.5 ± 19, and 96.7 ± 13.8 %, respectively. ATT pre-operatively and at 12 months after surgery was 5.4 ± 1.3 and 1.0 ± 0.8 mm, respectively. No subjects exhibited positive pivot shift after surgery. Within 6 months following surgery, quadriceps hypotrophy was observed in all subjects. However, the hypotrophy had recovered at 12 months following surgery. No subjects complained of donor site pain after surgery. Anatomical single-bundle ACL reconstruction using a quadriceps autograft resulted in equivalent level of muscle recovery and knee stability when compared with previously reported ACL

The Effects of Different Passive Static Stretching Intensities on Recovery from Unaccustomed Eccentric Exercise - A Randomized Controlled Trial.

PubMed

Apostolopoulos, Nikos C; Lahart, Ian M; Plyley, Michael J; Taunton, Jack; Nevill, Alan M; Koutedakis, Yiannis; Wyon, Matthew; Metsios, George S

2018-03-12

Effects of passive static stretching intensity on recovery from unaccustomed eccentric exercise of right knee extensors was investigated in 30 recreationally active males randomly allocated into three groups: high-intensity (70-80% maximum perceived stretch), low-intensity (30-40% maximum perceived stretch), and control. Both stretching groups performed 3 sets of passive static stretching exercises of 60s each for hamstrings, hip flexors, and quadriceps, over 3 consecutive days, post-unaccustomed eccentric exercise. Muscle function (eccentric and isometric peak torque) and blood biomarkers (CK and CRP) were measured before (baseline) and after (24, 48, and 72h) unaccustomed eccentric exercise. Perceived muscle soreness scores were collected immediately (time 0), and after 24, 48, and 72h post-exercise. Statistical time x condition interactions observed only for eccentric peak torque (p=.008). Magnitude-based inference analyses revealed low-intensity stretching had most likely, very likely, or likely beneficial effects on perceived muscle soreness (48-72h and 0-72h) and eccentric peak torque (baseline-24h and baseline-72h), compared with high-intensity stretching. Compared with control, low-intensity stretching had very likely or likely beneficial effects on perceived muscle soreness (0-24h and 0-72h), eccentric peak torque (baseline-48h and baseline-72h), and isometric peak torque (baseline-72h). High-intensity stretching had likely beneficial effects on eccentric peak torque (baseline-48h), but likely harmful effects eccentric peak torque (baseline-24h) and CK (baseline-48h and baseline-72h), compared with control. Therefore, low-intensity stretching is likely to result in small-to-moderate beneficial effects on perceived muscle soreness and recovery of muscle function post-unaccustomed eccentric exercise, but not markers of muscle damage and inflammation, compared with high-intensity or no stretching.

Influence of Herpes Simplex Virus 1 Latency-Associated Transcripts on the Establishment and Maintenance of Latency in the ROSA26R Reporter Mouse Model

PubMed Central

Nicoll, M. P.; Proença, J. T.; Connor, V.

2012-01-01

Herpes simplex virus 1 (HSV-1) can establish life-long latent infection in sensory neurons, from which periodic reactivation can occur. During latency, viral gene expression is largely restricted to the latency-associated transcripts (LATs). While not essential for any phase of latency, to date the LATs have been shown to increase the efficiency of both establishment and reactivation of latency in small-animal models. We sought to investigate the role of LAT expression in the frequency of latency establishment within the ROSA26R reporter mouse model utilizing Cre recombinase-encoding recombinant viruses harboring deletions of the core LAT promoter (LAP) region. HSV-1 LAT expression was observed to influence the number of latently infected neurons in trigeminal but not dorsal root ganglia. Furthermore, the relative frequencies of latency establishment of LAT-positive and LAT-negative viruses are influenced by the inoculum dose following infection of the mouse whisker pads. Finally, analysis of the infected cell population at two latent time points revealed a relative loss of latently infected cells in the absence of LAT expression. We conclude that the HSV-1 LATs facilitate the long-term stability of the latent cell population within the infected host and that interpretation of LAT establishment phenotypes is influenced by infection methodology. PMID:22696655

Effects of Quadriceps Muscle Fatigue on Stiff-Knee Gait in Patients with Hemiparesis

PubMed Central

Boudarham, Julien; Roche, Nicolas; Pradon, Didier; Delouf, Eric; Bensmail, Djamel; Zory, Raphael

2014-01-01

The relationship between neuromuscular fatigue and locomotion has never been investigated in hemiparetic patients despite the fact that, in the clinical context, patients report to be more spastic or stiffer after walking a long distance or after a rehabilitation session. The aim of this study was to evaluate the effects of quadriceps muscle fatigue on the biomechanical gait parameters of patients with a stiff-knee gait (SKG). Thirteen patients and eleven healthy controls performed one gait analysis before a protocol of isokinetic quadriceps fatigue and two after (immediately after and after 10 minutes of rest). Spatiotemporal parameters, sagittal knee and hip kinematics, rectus femoris (RF) and vastus lateralis (VL) kinematics and electromyographic (EMG) activity were analyzed. The results showed that quadriceps muscle weakness, produced by repetitive concentric contractions of the knee extensors, induced an improvement of spatiotemporal parameters for patients and healthy subjects. For the patient group, the increase in gait velocity and step length was associated with i) an increase of sagittal hip and knee flexion during the swing phase, ii) an increase of the maximal normalized length of the RF and VL and of the maximal VL lengthening velocity during the pre-swing and swing phases, and iii) a decrease in EMG activity of the RF muscle during the initial pre-swing phase and during the latter 2/3 of the initial swing phase. These results suggest that quadriceps fatigue did not alter the gait of patients with hemiparesis walking with a SKG and that neuromuscular fatigue may play the same functional role as an anti-spastic treatment such as botulinum toxin-A injection. Strength training of knee extensors, although commonly performed in rehabilitation, does not seem to be a priority to improve gait of these patients. PMID:24718087

Simultaneous Bilateral Quadriceps Tendon Rupture in Patient with Chronic Renal Failure

PubMed Central

Lee, Yunseok; Kim, Byounggook; Chung, Ju-Hwan

2011-01-01

Simultaneous bilateral spontaneous rupture of the quadriceps tendon is a very rare condition and only a few cases have been reported in the literature. The etiology is not clear yet. But it occurs infrequently in patients with chronic metabolic disorders. A 30-year-old female patient with simultaneous bilateral spontaneous quadriceps tendon rupture visited our hospital. She had chronic renal failure and her parathyroid hormone level was elevated due to parathyroid adenoma. We report a surgical repair of both quadriceps tendons of a patient with chronic renal failure as well as management of hyperparathyroidism. PMID:22570843

Gear Shifting of Quadriceps during Isometric Knee Extension Disclosed Using Ultrasonography.

PubMed

Zhang, Shu; Huang, Weijian; Zeng, Yu; Shi, Wenxiu; Diao, Xianfen; Wei, Xiguang; Ling, Shan

2018-01-01

Ultrasonography has been widely employed to estimate the morphological changes of muscle during contraction. To further investigate the motion pattern of quadriceps during isometric knee extensions, we studied the relative motion pattern between femur and quadriceps under ultrasonography. An interesting observation is that although the force of isometric knee extension can be controlled to change almost linearly, femur in the simultaneously captured ultrasound video sequences has several different piecewise moving patterns. This phenomenon is like quadriceps having several forward gear ratios like a car starting from rest towards maximal voluntary contraction (MVC) and then returning to rest. Therefore, to verify this assumption, we captured several ultrasound video sequences of isometric knee extension and collected the torque/force signal simultaneously. Then we extract the shapes of femur from these ultrasound video sequences using video processing techniques and study the motion pattern both qualitatively and quantitatively. The phenomenon can be seen easier via a comparison between the torque signal and relative spatial distance between femur and quadriceps. Furthermore, we use cluster analysis techniques to study the process and the clustering results also provided preliminary support to the conclusion that, during both ramp increasing and decreasing phases, quadriceps contraction may have several forward gear ratios relative to femur.

Acute Effect of Static Stretching on Lower Limb Movement Performance by Using STABL Virtual Reality System.

PubMed

Ameer, Mariam A; Muaidi, Qassim I

2017-07-17

The effect of acute static stretch (ASS) on the lower limb RT has been recently questioned to decrease the risk of falling and injuries in situations requiring a rapid reaction, as in the cases of balance disturbance. The main purpose of this study was to detect the effect of ASS on the lower limb RT by using virtual reality device. Two Group Control Group design. Research laboratory. The control and experimental groups were formed randomly from sixty female university students. Each participant in the experimental group was tested before and after ASS for the quadriceps, hamstrings and planter flexor muscles, and compared with the control group with warming-up exercise only. The stretching program involved warming-up in the form of circular running inside the lab for 5 minutes followed by stretching of each muscle group thrice, to the limit of discomfort of 45 s, with resting period of 15s between stretches. The measurements included the RT of the dominant lower extremity by using the dynamic stability program, STABL Virtual Reality System (Model No. DIZ 2709, Motek Medical and Force Link Merged Co., Amsterdam). There was statistically significant reduction (F = 162, P= .00) in post-test RT between the two groups, and significant decrease in RT after stretching, in the experimental group (7.5%) (P= .00). ASS of the lower limb muscles tends to decrease the lower limb RT and improve movement performance.

Cardiovascular Responses to Skeletal Muscle Stretching: "Stretching" the Truth or a New Exercise Paradigm for Cardiovascular Medicine?

PubMed

Kruse, Nicholas T; Scheuermann, Barry W

2017-12-01

Stretching is commonly prescribed with the intended purpose of increasing range of motion, enhancing muscular coordination, and preventing prolonged immobilization induced by aging or a sedentary lifestyle. Emerging evidence suggests that acute or long-term stretching exercise may modulate a variety of cardiovascular responses. Specifically, at the onset of stretch, the mechanical deformation of the vascular bed coupled with stimulation of group III muscle afferent fibers initiates a cascade of events resulting in both peripheral vasodilation and a heart rate-driven increase in cardiac output, blood pressure, and muscle blood flow. This potential to increase shear stress and blood flow without the use of excessive muscle energy expenditure may hold important implications for future therapeutic vascular medicine and cardiac health. However, the idea that a cardiovascular component may be involved in human skeletal muscle stretching is relatively new. Therefore, the primary intent of this review is to highlight topics related to skeletal muscle stretching and cardiovascular regulation and function. The current evidence suggests that acute stretching causes a significant macro- and microcirculatory event that alters blood flow and the relationship between oxygen availability and oxygen utilization. These acute vascular changes if performed chronically may result in improved endothelial function, improved arterial blood vessel stiffness, and/or reduced blood pressure. Although several mechanisms have been postulated, an increased nitric oxide bioavailability has been highlighted as one promising candidate for the improvement in vessel function with stretching. Collectively, the evidence provided in this review suggests that stretching acutely or long term may serve as a novel and alternative low intensity therapeutic intervention capable of improving several parameters of vascular function.

Knee flexion with quadriceps cocontraction: A new therapeutic exercise for the early stage of ACL rehabilitation.

PubMed

Biscarini, Andrea; Contemori, Samuele; Busti, Daniele; Botti, Fabio M; Pettorossi, Vito E

2016-12-08

Quadriceps strengthening exercises designed for the early phase of anterior cruciate ligament (ACL) rehabilitation should limit the anterior tibial translation developed by quadriceps contraction near full knee extension, in order to avoid excessive strain on the healing tissue. We hypothesize that knee-flexion exercises with simultaneous voluntary contraction of quadriceps (voluntary quadriceps cocontraction) can yield considerable levels of quadriceps activation while preventing the tibia from translating forward relative to the femur. Electromyographic activity in quadriceps and hamstring muscles was measured in 20 healthy males during isometric knee-flexion exercises executed near full knee extension with maximal voluntary effort of quadriceps cocontraction and external resistance (R) ranging from 0% to 60% of the 1-repetition maximum (1RM). Biomechanical modeling was applied to derive the shear (anterior/posterior) tibiofemoral force developed in each exercise condition. Isometric knee-flexion exercises with small external resistance (R=10% 1RM) and maximal voluntary effort of quadriceps cocontraction yielded a net posterior (ACL-unloading) tibial pull (P=0.005) and levels of activation of 32%, 50%, and 45% of maximum voluntary isometric contraction, for the rectus femoris, vastus medialis, and vastus lateralis, respectively. This exercise might potentially rank as one of the most appropriate quadriceps strengthening interventions in the early phase of ACL rehabilitation. Copyright © 2016 Elsevier Ltd. All rights reserved.

Influence of Anterior Cruciate Ligament Tear on Thigh Muscle Strength and Hamstring-to-Quadriceps Ratio: A Meta-Analysis.

PubMed

Kim, Hyun-Jung; Lee, Jin-Hyuck; Ahn, Sung-Eun; Park, Min-Ji; Lee, Dae-Hee

2016-01-01

Theoretical compensation after anterior cruciate ligament (ACL) tear could cause quadriceps weakness and hamstring activation, preventing anterior tibial subluxation and affecting the expected hamstring-to-quadriceps ratio. Although quadriceps weakness often occurs after ACL tears, it remains unclear whether hamstring strength and hamstring-to-quadriceps ratio increase in ACL deficient knees. This meta-analysis compared the isokinetic muscle strength of quadriceps and hamstring muscles, and the hamstring-to-quadriceps ratio, of the injured and injured limbs of patients with ACL tears. This meta-analysis included all studies comparing isokinetic thigh muscle strengths and hamstring-to-quadriceps ratio in the injured and uninjured legs of patients with ACL tear, without or before surgery. Thirteen studies were included in the meta-analysis. Quadriceps and hamstring strengths were 22.3 N∙m (95% CI: 15.2 to 29.3 N∙m; P<0.001) and 7.4 N∙m (95% CI: 4.3 to 10.5 N∙m; P<0.001) lower, respectively, on the injured than on the uninjured side. The mean hamstring-to-quadriceps ratio was 4% greater in ACL deficient than in uninjured limbs (95% CI: 1.7% to 6.3%; P<0.001). Conclusively, Decreases were observed in both the quadriceps and hamstring muscles of patients with ACL tear, with the decrease in quadriceps strength being 3-fold greater. These uneven reductions slightly increase the hamstring-to-quadriceps ratio in ACL deficient knees.

Influence of Anterior Cruciate Ligament Tear on Thigh Muscle Strength and Hamstring-to-Quadriceps Ratio: A Meta-Analysis

PubMed Central

Ahn, Sung-Eun; Park, Min-Ji; Lee, Dae-Hee

2016-01-01

Theoretical compensation after anterior cruciate ligament (ACL) tear could cause quadriceps weakness and hamstring activation, preventing anterior tibial subluxation and affecting the expected hamstring-to-quadriceps ratio. Although quadriceps weakness often occurs after ACL tears, it remains unclear whether hamstring strength and hamstring-to-quadriceps ratio increase in ACL deficient knees. This meta-analysis compared the isokinetic muscle strength of quadriceps and hamstring muscles, and the hamstring-to-quadriceps ratio, of the injured and injured limbs of patients with ACL tears. This meta-analysis included all studies comparing isokinetic thigh muscle strengths and hamstring-to-quadriceps ratio in the injured and uninjured legs of patients with ACL tear, without or before surgery. Thirteen studies were included in the meta-analysis. Quadriceps and hamstring strengths were 22.3 N∙m (95% CI: 15.2 to 29.3 N∙m; P<0.001) and 7.4 N∙m (95% CI: 4.3 to 10.5 N∙m; P<0.001) lower, respectively, on the injured than on the uninjured side. The mean hamstring-to-quadriceps ratio was 4% greater in ACL deficient than in uninjured limbs (95% CI: 1.7% to 6.3%; P<0.001). Conclusively, Decreases were observed in both the quadriceps and hamstring muscles of patients with ACL tear, with the decrease in quadriceps strength being 3-fold greater. These uneven reductions slightly increase the hamstring-to-quadriceps ratio in ACL deficient knees. PMID:26745808

Variability of Measurement of Patellofemoral Indices with Knee Flexion and Quadriceps Contraction: An MRI-Based Anatomical Study

PubMed Central

Laugharne, Edward; Bali, Navi; Purushothamdas, Sanjay; Almallah, Faris; Kundra, Rik

2016-01-01

Purpose The purpose of this study was to investigate the impact of varying knee flexion and quadriceps activity on patellofemoral indices measured on magnetic resonance imaging (MRI). Materials and Methods MRI of the knee was performed in 20 patients for indications other than patellar or patellofemoral pathology. Axial and sagittal sequences were performed in full extension of the knee with the quadriceps relaxed, full extension of the knee with the quadriceps contracted, 30° flexion of the knee with the quadriceps relaxed, and 30° flexion with the quadriceps contracted. Bisect offset, patella tilt angle, Insall-Salvati ratio and Caton-Deschamps index were measured. Results With the knee flexed to 30° and quadriceps relaxed, the mean values of patellar tilt angle, bisect offset, Insall-Salvati ratio and Caton-Deschamps index were all within normal limits. With the knee extended and quadriceps contracted, the mean patellar tilt angle (normal value, <15°) was 14.6° and the bisect offset (normal value, <65%) was 65%, while the Caton-Deschamps index was 1.34 (normal range, 0.6 to 1.3). With the knee extended and quadriceps relaxed, the mean Caton-Deschamps index was 1.31. Conclusions MRI scanning of the knee in extension with the quadriceps contracted leads to elevated patellofemoral indices. MRI taken with the knee in 30° of flexion allows more reliable assessment of the patellofemoral joint and minimises the confounding effect of quadriceps contraction. PMID:27894177

Spatial distribution of motor units recruited during electrical stimulation of the quadriceps muscle versus the femoral nerve.

PubMed

Rodriguez-Falces, Javier; Maffiuletti, Nicola A; Place, Nicolas

2013-11-01

In this study we investigated differences in the spatial recruitment of motor units (MUs) in the quadriceps when electrical stimulation is applied over the quadriceps belly versus the femoral nerve. M-waves and mechanical twitches were evoked using over-the-quadriceps and femoral nerve stimulation of gradually increasing intensity from 22 young, healthy subjects. Spatial recruitment was investigated using recruitment curves of M-waves recorded from the vastus medialis (VM) and vastus lateralis (VL) and of twitches recorded from the quadriceps. At maximal stimulation intensity (Imax), no differences were found between nerve and over-the-quadriceps stimulation. At submaximal intensities, VL M-wave amplitude was higher for over-the-quadriceps stimulation at 40% Imax, and peak twitch force was greater for nerve stimulation at 60% and 80% Imax. For the VM, MU spatial recruitment during nerve and over-the-quadriceps stimulation of increasing intensity occurred in a similar manner, whereas significant differences were observed for the VL. Copyright © 2013 Wiley Periodicals, Inc.

Preferential reduction of quadriceps over respiratory muscle strength and bulk after lung transplantation for cystic fibrosis.

PubMed

Pinet, C; Scillia, P; Cassart, M; Lamotte, M; Knoop, C; Mélot, C; Estenne, M

2004-09-01

In the absence of complications, recipients of lung transplants for cystic fibrosis have normal pulmonary function but the impact of the procedure on the strength and bulk of respiratory and limb muscles has not been studied. Twelve stable patients who had undergone lung transplantation for cystic fibrosis 48 months earlier (range 8-95) and 12 normal subjects matched for age, height, and sex were studied. The following parameters were measured: standard lung function, peak oxygen uptake by cycle ergometry, diaphragm surface area by computed tomographic (CT) scanning, diaphragm and abdominal muscle thickness by ultrasonography, twitch transdiaphragmatic and gastric pressures, quadriceps isokinetic strength, and quadriceps cross section by CT scanning, and lean body mass. Diaphragm mass was computed from diaphragm surface area and thickness. Twitch transdiaphragmatic and gastric pressures, diaphragm mass, and abdominal muscle thickness were similar in the two groups but quadriceps strength and cross section were decreased by nearly 30% in the patients. Patients had preserved quadriceps strength per unit cross section but reduced quadriceps cross section per unit lean body mass. The cumulative dose of corticosteroids was an independent predictor of quadriceps atrophy. Peak oxygen uptake showed positive correlations with quadriceps strength and cross section in the two groups, but peak oxygen uptake per unit quadriceps strength or cross section was reduced in the patient group. The diaphragm and abdominal muscles have preserved strength and bulk in patients transplanted for cystic fibrosis but the quadriceps is weak due to muscle atrophy. This atrophy is caused in part by corticosteroid therapy and correlates with the reduction in exercise capacity.

Acute Effects of Static vs. Ballistic Stretching on Strength and Muscular Fatigue Between Ballet Dancers and Resistance-Trained Women.

PubMed

Lima, Camila D; Brown, Lee E; Wong, Megan A; Leyva, Whitney D; Pinto, Ronei S; Cadore, Eduardo L; Ruas, Cassio V

2016-11-01

Lima, CD, Brown, LE, Wong, MA, Leyva, WD, Pinto, RS, Cadore, EL, and Ruas, CV. Acute effects of static vs. ballistic stretching on strength and muscular fatigue between ballet dancers and resistance-trained women. J Strength Cond Res 30(11): 3220-3227, 2016-Stretching is used to increase joint range of motion, but the acute effects can decrease muscle strength. However, this may depend on the population or mode of stretching. The purpose of this study was to compare the acute effects of static vs. ballistic stretching on strength and muscular fatigue between ballet dancers and resistance-trained women. Fifteen resistance-trained women (age 23.8 ± 1.80 years, mass 67.47 ± 7.77 kg, height 168.30 ± 5.53 cm) and 12 ballet dancers (age 22.8 ± 3.04 years, mass 58.67 ± 5.65 kg, height 168.00 ± 7.69 cm) performed 5 days of testing. The first day was control (no stretching), whereas the other 4 days were static or ballistic stretching in a counterbalanced order. Range of motion, strength, and fatigue tests were also performed. Both groups demonstrated a significant decrease in hamstrings strength after static (102.71 ± 2.67 N·m) and ballistic stretching (99.49 ± 2.61 N·m) compared with control (113.059 ± 3.25 N·m), with no changes in quadriceps strength. For fatigue, only ballet dancers demonstrated a decrease from control (71.79 ± 4.88%) to ballistic (65.65 ± 8.19%), but no difference with static (65.01 ± 12.29%). These findings suggest that stretching decreases hamstrings strength similarly in ballet dancers and resistance-trained women, with no differences between modes of stretching. However, ballistic stretching only decreased muscular fatigue in ballet dancers, but not in resistance-trained women. Therefore, no stretching should be performed before strength performance. However, ballistic stretching may decrease acute muscular fatigue in ballet dancers.

Position of the quadriceps actuator influences knee loads during simulated squat testing.

PubMed

Hast, Michael W; Piazza, Stephen J

2018-05-17

The "Oxford Rig" cadaveric simulator permits researchers and clinicians to study knee mechanics during a simulated squatting motion. The motion of the lower limb in the Oxford Rig is typically controlled by a single actuator that applies tension to the quadriceps tendon. The location of the quadriceps actuator, however, has differed across published descriptions of the Oxford Rig. Actuators have been placed on the femur and pelvis, and on "grounded" locations external to the specimen, but the consequences of this placement for knee kinematics and kinetics are unknown. The purpose of this study was to examine these effects using a validated computational musculoskeletal model. When the actuator was placed on the femur or pelvis, forces realistically increased with knee flexion, with quadriceps and patellofemoral contact forces exceeding 2000 N and 3000 N, respectively, at 100° flexion. When the actuator was grounded, however, forces were substantially reduced and did not monotonically increase with flexion. Articular joint contact forces were not strongly influenced by changing the location of the actuator from the femur to the pelvis, with small RMS differences in quadriceps forces (48.2 N), patellofemoral forces (83.6 N), and tibiofemoral forces (58.9 N) between these conditions. The location of the actuator did not substantially affect knee kinematics. The results of this study suggest that the quadriceps actuator of the Oxford Rig should be attached to either the femur or the pelvis when the goal is to make realistic estimates of quadriceps forces and articular contact forces within the knee joint. Copyright © 2018 Elsevier Ltd. All rights reserved.

Low-Latency Lunar Surface Telerobotics from Earth-Moon Libration Points

NASA Technical Reports Server (NTRS)

Lester, Daniel; Thronson, Harley

2011-01-01

Concepts for a long-duration habitat at Earth-Moon LI or L2 have been advanced for a number of purposes. We propose here that such a facility could also have an important role for low-latency telerobotic control of lunar surface equipment, both for lunar science and development. With distances of about 60,000 km from the lunar surface, such sites offer light-time limited two-way control latencies of order 400 ms, making telerobotic control for those sites close to real time as perceived by a human operator. We point out that even for transcontinental teleoperated surgical procedures, which require operational precision and highly dexterous manipulation, control latencies of this order are considered adequate. Terrestrial telerobots that are used routinely for mining and manufacturing also involve control latencies of order several hundred milliseconds. For this reason, an Earth-Moon LI or L2 control node could build on the technology and experience base of commercially proven terrestrial ventures. A lunar libration-point telerobotic node could demonstrate exploration strategies that would eventually be used on Mars, and many other less hospitable destinations in the solar system. Libration-point telepresence for the Moon contrasts with lunar telerobotic control from the Earth, for which two-way control latencies are at least six times longer. For control latencies that long, telerobotic control efforts are of the "move-and-wait" variety, which is cognitively inferior to near real-time control.

Quadriceps tendon autograft for arthroscopic knee ligament reconstruction: use it now, use it often.

PubMed

Sheean, Andrew J; Musahl, Volker; Slone, Harris S; Xerogeanes, John W; Milinkovic, Danko; Fink, Christian; Hoser, Christian

2018-04-28

Traditional bone-patellar tendon-bone and hamstring tendon ACL grafts are not without limitations. A growing body of anatomic, biomechanical and clinical data has demonstrated the utility of quadriceps tendon autograft in arthroscopic knee ligament reconstruction. The quadriceps tendon autograft provides a robust volume of tissue that can be reliably harvested, mitigating the likelihood of variably sized grafts and obviating the necessity of allograft augmentation. Modern, minimally invasive harvest techniques offer the advantages of low rates of donor site morbidity and residual extensor mechanism strength deficits. New data suggest that quadriceps tendon autograft may possess superior biomechanical characteristics when compared with bone-patella tendon-bone (BPTB) autograft. However, there have been very few direct, prospective comparisons between the clinical outcomes associated with quadriceps tendon autograft and other autograft options (eg, hamstring tendon and bone-patellar tendon-bone). Nevertheless, quadriceps tendon autograft should be one of the primary options in any knee surgeon's armamentarium. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Acute Effects of Static Stretching of Hamstring on Performance and Anterior Cruciate Ligament Injury Risk During Stop-Jump and Cutting Tasks in Female Athletes.

PubMed

Ruan, Mianfang; Zhang, Qiang; Wu, Xie

2017-05-01

Ruan, M, Zhang, Q, and Wu, X. Acute effects of static stretching of hamstring on performance and anterior cruciate ligament injury risk during stop-jump and cutting tasks in female athletes. J Strength Cond Res 31(5): 1241-1250, 2017-There is limited research investigating antagonist stretch. The purpose of this study was to evaluate the influence of static stretching of hamstrings (SSH) on performance and anterior cruciate ligament (ACL) injury risk during stop-jump and 180° cutting tasks. Twelve female college athletes (age 20.8 ± 0.7 years; height 1.61 ± 0.05 m; mass 54.25 ± 4.22 kg) participated in this study. Subjects performed stop-jump and 180° cutting tasks under 2 conditions: after warm-up with 4 × 30 seconds SSH or after warm-up without SSH. Three-dimensional kinematic and kinetic data as well as electromyography of biceps femoris, rectus femoris, vastus medialis, and gastrocnemius medialis were collected during testing. Static stretching of hamstrings significantly enhanced jump height by 5.1% (p = 0.009) but did not change the takeoff speed of cutting. No significant changes in peak knee adduction moment or peak anterior tibia shear force were observed with SSH regardless of the task. The peak lateral tibia shear force during cutting was significantly (p = 0.036) reduced with SSH. The co-contraction of hamstring and quadriceps during the preactivation (stop-jump: p = 0.04; cutting: p = 0.05) and downward phases (stop-jump: p = 0.04; cutting: p = 0.05) was significantly reduced after SSH regardless of the task. The results suggest that SSH enhanced the performance of stop-jump because of decreased co-contraction of hamstring and quadriceps but did not change the performance of cutting. In addition, SSH did not increase ACL injury risk during stop-jump and cutting tasks and even reduced medial-lateral knee loading during cutting.

Acute Effects of Static Stretching of Hamstring on Performance and Anterior Cruciate Ligament Injury Risk During Stop-Jump and Cutting Tasks in Female Athletes

PubMed Central

Ruan, Mianfang; Zhang, Qiang

2017-01-01

Abstract Ruan, M, Zhang, Q, and Wu, X. Acute effects of static stretching of hamstring on performance and anterior cruciate ligament injury risk during stop-jump and cutting tasks in female athletes. J Strength Cond Res 31(5): 1241–1250, 2017—There is limited research investigating antagonist stretch. The purpose of this study was to evaluate the influence of static stretching of hamstrings (SSH) on performance and anterior cruciate ligament (ACL) injury risk during stop-jump and 180° cutting tasks. Twelve female college athletes (age 20.8 ± 0.7 years; height 1.61 ± 0.05 m; mass 54.25 ± 4.22 kg) participated in this study. Subjects performed stop-jump and 180° cutting tasks under 2 conditions: after warm-up with 4 × 30 seconds SSH or after warm-up without SSH. Three-dimensional kinematic and kinetic data as well as electromyography of biceps femoris, rectus femoris, vastus medialis, and gastrocnemius medialis were collected during testing. Static stretching of hamstrings significantly enhanced jump height by 5.1% (p = 0.009) but did not change the takeoff speed of cutting. No significant changes in peak knee adduction moment or peak anterior tibia shear force were observed with SSH regardless of the task. The peak lateral tibia shear force during cutting was significantly (p = 0.036) reduced with SSH. The co-contraction of hamstring and quadriceps during the preactivation (stop-jump: p = 0.04; cutting: p = 0.05) and downward phases (stop-jump: p = 0.04; cutting: p = 0.05) was significantly reduced after SSH regardless of the task. The results suggest that SSH enhanced the performance of stop-jump because of decreased co-contraction of hamstring and quadriceps but did not change the performance of cutting. In addition, SSH did not increase ACL injury risk during stop-jump and cutting tasks and even reduced medial-lateral knee loading during cutting. PMID:28118311

Hamstring Stiffness Returns More Rapidly After Static Stretching Than Range of Motion, Stretch Tolerance, and Isometric Peak Torque.

PubMed

Hatano, Genki; Suzuki, Shigeyuki; Matsuo, Shingo; Kataura, Satoshi; Yokoi, Kazuaki; Fukaya, Taizan; Fujiwara, Mitsuhiro; Asai, Yuji; Iwata, Masahiro

2017-12-18

Hamstring injuries are common, and lack of hamstring flexibility may predispose to injury. Static stretching increases range of motion (ROM) but also results in reduced muscle strength after stretching. The effects of stretching on the hamstring muscles and the duration of these effects remain unclear. To determine the effects of static stretching on the hamstrings and the duration of these effects. Randomized crossover study. University laboratory. Twenty-four healthy volunteers. We measured the torque-angle relationship (ROM, passive torque (PT) at the onset of pain, and passive stiffness) and isometric muscle force using an isokinetic dynamometer. After a 60-minute rest, the ROM of the dynamometer was set at maximum tolerable intensity; this position was maintained for 300 seconds while static passive torque (SPT) was measured continuously. We remeasured the torque-angle relationship and isometric muscle force after rest periods of 10, 20, and 30 minutes. Change in SPT during stretching; changes in ROM, PT at the onset of pain, passive stiffness, and isometric muscle force before stretching compared with 10, 20, and 30 minutes after stretching. SPT decreased significantly during stretching. Passive stiffness decreased significantly 10 and 20 minutes after stretching, but there was no significant pre- vs. post-stretching difference after 30 minutes. PT at the onset of pain and ROM increased significantly after stretching at all rest intervals, while isometric muscle force decreased significantly after all rest intervals. The effect of static stretching on passive stiffness of the hamstrings was not maintained as long as the changes in ROM, stretch tolerance, and isometric muscle force. Therefore, frequent stretching is necessary to improve the viscoelasticity of the muscle-tendon unit. Muscle force was decreased for 30 minutes after stretching; this should be considered prior to activities requiring maximal muscle strength.

Epidemiology of Quadriceps Strains in National Collegiate Athletic Association Athletes, 2009–2010 Through 2014–2015

PubMed Central

Eckard, Timothy G.; Kerr, Zachary Y.; Padua, Darin A.; Djoko, Aristarque; Dompier, Thomas P.

2017-01-01

Context:  Few researchers have examined the rates and patterns of quadriceps strains in student-athletes in the National Collegiate Athletic Association (NCAA). Objective:  To describe the epidemiology of quadriceps strains in 25 NCAA sports during the 2009–2010 through 2014–2015 academic years. Design:  Descriptive epidemiology study. Setting:  Convenience sample of NCAA programs from 25 sports during the 2009–2010 through 2014–2015 academic years. Patients or Other Particpants:  Collegiate student-athletes participating in men's and women's NCAA athletics during the 2009–2010 through 2014–2015 academic years. Main Outcome Measure(s):  Aggregate quadriceps strain injury and exposure data from the NCAA Injury Surveillance Program during the 2009–2010 through 2014–2015 academic years were analyzed. Quadriceps strain injury rates and injury rate ratios (IRRs) were reported with 95% confidence intervals (CIs). Results:  Overall, 517 quadriceps strains were reported, resulting in an injury rate of 1.07/10 000 athlete-exposures (AEs). The sports with the highest overall quadriceps strain rates were women's soccer (5.61/10 000 AEs), men's soccer (2.52/10 000 AEs), women's indoor track (2.24/10 000 AEs), and women's softball (2.15/10 000 AEs). Across sex-comparable sports, women had a higher rate of quadriceps strains than men overall (1.97 versus 0.65/10 000 AEs; IRR = 3.03; 95% CI = 2.45, 3.76). The majority of quadriceps strains were sustained during practice (77.8%). However, the quadriceps strain rate was higher during competition than during practice (1.29 versus 1.02/10 000 AEs; IRR = 1.27; 95% CI = 1.03, 1.56). Most quadriceps strains occurred in the preseason (57.8%), and rates were higher during the preseason compared with the regular season (2.29 versus 0.63/10 000 AEs; IRR = 3.60; 95% CI = 3.02, 4.30). Common injury mechanisms were noncontact (63.2%) and overuse (21.9%). Most quadriceps strains restricted

Performance on a Clinical Quadriceps Activation Battery Is Related to a Laboratory Measure of Activation and Recovery After Total Knee Arthroplasty.

PubMed

Bade, Michael; Struessel, Tamara; Paxton, Roger; Winters, Joshua; Baym, Carol; Stevens-Lapsley, Jennifer

2018-01-01

To determine the relation between performance on a clinical quadriceps activation battery with (1) activation measured by doublet interpolation and (2) recovery of quadriceps strength and functional performance after total knee arthroplasty (TKA). Planned secondary analysis of a randomized controlled trial. University research laboratory. Patients (N=162; mean age, 63±7y; 89 women) undergoing TKA. Patients were classified as high (quadriceps activation battery ≥4/6) or low (quadriceps activation battery ≤3/6) based on performance on the quadriceps activation battery measured 4 days after TKA. Differences between groups in activation and recovery at 1, 2, 3, 6, and 12 months after TKA were compared using a repeated-measures maximum likelihood model. The low quadriceps activation battery group demonstrated poorer quadriceps activation via doublet interpolation (P=.01), greater quadriceps strength loss (P=.01), and greater functional performance decline (all P<.001) at 1 month after TKA compared with the high quadriceps activation battery group. Differences between low and high quadriceps activation battery groups on all measures did not persist at 3 and 12 months (all P>.05). Poor performance on the quadriceps activation battery early after TKA is related to poor quadriceps activation and poor recovery in the early postoperative period. Patients in the low quadriceps activation battery group took 3 months to recover to the same level as the high quadriceps activation battery group. The quadriceps activation battery may be useful in identifying individuals who need specific interventions to target activation deficits or different care pathways in the early postoperative period to speed recovery after TKA. Copyright © 2017 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

Long-latency reflexes of elbow and shoulder muscles suggest reciprocal excitation of flexors, reciprocal excitation of extensors, and reciprocal inhibition between flexors and extensors

PubMed Central

Meriggi, Jenna; Parikh, Nidhi; Saad, Kenneth

2016-01-01

Postural corrections of the upper limb are required in tasks ranging from handling an umbrella in the changing wind to securing a wriggling baby. One complication in this process is the mechanical interaction between the different segments of the arm where torque applied at one joint induces motion at multiple joints. Previous studies have shown the long-latency reflexes of shoulder muscles (50–100 ms after a limb perturbation) account for these mechanical interactions by integrating information about motion of both the shoulder and elbow. It is less clear whether long-latency reflexes of elbow muscles exhibit a similar capability and what is the relation between the responses of shoulder and elbow muscles. The present study utilized joint-based loads tailored to the subjects' arm dynamics to induce well-controlled displacements of their shoulder and elbow. Our results demonstrate that the long-latency reflexes of shoulder and elbow muscles integrate motion from both joints: the shoulder and elbow flexors respond to extension at both joints, whereas the shoulder and elbow extensors respond to flexion at both joints. This general pattern accounts for the inherent flexion-extension coupling of the two joints arising from the arm's intersegmental dynamics and is consistent with spindle-based reciprocal excitation of shoulder and elbow flexors, reciprocal excitation of shoulder and elbow extensors, and across-joint inhibition between the flexors and extensors. PMID:26864766

Posterolateral hip muscle strengthening versus quadriceps strengthening for patellofemoral pain: a comparative control trial.

PubMed

Khayambashi, Khalil; Fallah, Alireza; Movahedi, Ahmadreza; Bagwell, Jennifer; Powers, Christopher

2014-05-01

To compare the efficacy of posterolateral hip muscle strengthening versus quadriceps strengthening in reducing pain and improving health status in persons with patellofemoral pain (PFP). Comparative control trial. Rehabilitation facility. Persons with a diagnosis of PFP (N=36; 18 men, 18 women). Patients were alternately assigned to a posterolateral hip muscle strengthening group (9 men and 9 women) or a quadriceps strengthening group (9 men and 9 women). The posterolateral hip muscle strengthening group performed hip abductor and external rotator strengthening exercises, whereas the quadriceps strengthening group performed quadriceps strengthening exercises (3 times a week for 8wk). Pain (visual analog scale [VAS]) and health status (Western Ontario McMaster Universities Osteoarthritis Index [WOMAC]) were assessed at baseline, postintervention, and 6-month follow-up. Significant improvements in VAS and WOMAC scores were observed in both groups from baseline to postintervention and baseline to 6-month follow-up (P<.001). Improvements in VAS and WOMAC scores in the posterolateral hip exercise group were superior to those in the quadriceps exercise group postintervention and at 6-month follow-up (P<.05). Although both intervention programs resulted in decreased pain and improved function in persons with PFP, outcomes in the posterolateral hip exercise group were superior to the quadriceps exercise group. The superior outcomes obtained in the posterolateral hip exercise group were maintained 6 months postintervention. Copyright © 2014 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

Varicella zoster virus latency

PubMed Central

Eshleman, Emily; Shahzad, Aamir; Cohrs, Randall J

2011-01-01

Primary infection by varicella zoster virus (VZV) typically results in childhood chickenpox, at which time latency is established in the neurons of the cranial nerve, dorsal root and autonomic ganglia along the entire neuraxis. During latency, the histone-associated virus genome assumes a circular episomal configuration from which transcription is epigenetically regulated. The lack of an animal model in which VZV latency and reactivation can be studied, along with the difficulty in obtaining high-titer cell-free virus, has limited much of our understanding of VZV latency to descriptive studies of ganglia removed at autopsy and analogy to HSV-1, the prototype alphaherpesvirus. However, the lack of miRNA, detectable latency-associated transcript and T-cell surveillance during VZV latency highlight basic differences between the two neurotropic herpesviruses. This article focuses on VZV latency: establishment, maintenance and reactivation. Comparisons are made with HSV-1, with specific attention to differences that make these viruses unique human pathogens. PMID:21695042

The associations between quadriceps muscle strength, power, and knee joint mechanics in knee osteoarthritis: A cross-sectional study.

PubMed

Murray, Amanda M; Thomas, Abbey C; Armstrong, Charles W; Pietrosimone, Brian G; Tevald, Michael A

2015-12-01

Abnormal knee joint mechanics have been implicated in the pathogenesis and progression of knee osteoarthritis. Deficits in muscle function (i.e., strength and power) may contribute to abnormal knee joint loading. The associations between quadriceps strength, power and knee joint mechanics remain unclear in knee osteoarthritis. Three-dimensional motion analysis was used to collect peak knee joint angles and moments during the first 50% of stance phase of gait in 33 participants with knee osteoarthritis. Quadriceps strength and power were assessed using a knee extension machine. Strength was quantified as the one repetition maximum. Power was quantified as the peak power produced at 40-90% of the one repetition maximum. Quadriceps strength accounted for 15% of the variance in peak knee flexion angle (P=0.016). Quadriceps power accounted for 20-29% of the variance in peak knee flexion angle (P<0.05). Quadriceps power at 90% of one repetition maximum accounted for 9% of the variance in peak knee adduction moment (P=0.05). These data suggest that quadriceps power explains more variance in knee flexion angle and knee adduction moment during gait in knee osteoarthritis than quadriceps strength. Additionally, quadriceps power at multiple loads is associated with knee joint mechanics and therefore should be assessed at a variety of loads. Taken together, these results indicate that quadriceps power may be a potential target for interventions aimed at changing knee joint mechanics in knee osteoarthritis. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effect of time-dependent cryotherapy on redox balance of quadriceps injuries.

PubMed

Silva, Marco Aurélio dos Santos; Carvalho, Taiara Ramos de; Cruz, Amanda Cristina Marques Barros da; Jesus, Lennon Rafael Guedine de; Silva Neto, Larissa Alexsandra da; Trajano, Eduardo Tavares Lima; Bezerra, Frank Silva

2016-02-01

Muscle trauma represents a high number of injuries in professional sport and recreation and may occur through several mechanisms. This study aims at analyzing time-dependent effects of cryotherapy on the redox balance in lesioned quadriceps muscles in F1 mice. Twenty male F1 mice were divided into five groups: (a) animals were not subjected to muscle lesioning or treatment (CTR); (b) quadriceps muscle was lesioned without treatment (L); (c) quadriceps muscle was lesioned and treated with cryotherapy for 5 min (LC5); (d) quadriceps muscle was lesioned and treated with cryotherapy for 20 min (LC20); and quadriceps muscle was lesioned and treated with cryotherapy for 40 min (LC40). The mice were euthanized; the quadriceps muscles were collected and subjected to analyses for levels of protein, hydroperoxides, nitrite, catalase (CAT) activity, oxidized glutathione (GSSG) and reduced glutathione (GSH). Protein levels were reduced in L (-39%; p < 0.05), LC5 (-54%; p < 0.05), LC20 (-40%; p < 0.05) and LC40 (-50%; p < 0.05) compared to CTR. There was an increase in lipid peroxidation in L (158%; p < 0.05), LC5 (300%; p < 0.01), LC20 (292%; p < 0.01) and LC40 (362%; p < 0.01) compared to CTR. We observed a significant increase in CAT activity in L (164%; p < 0.05) and LC5 (193%; p < 0.01) compared to CTR; a significant reduction in GSH in L (-60%; p < 0.05) and LC20 (-61%; p < 0.05) compared to CTR; and a significant increase in GSSG in LC5 (171%; p < 0.05) compared to CTR. In addition, GSH/GSSG was reduced in L (-89%; p < 0.01), LC5 (-95%; p < 0.01), LC20 (-59%; p < 0.05), and LC40 (-82%; p < 0.01) compared to CTR. This study showed that the cryotherapy does not improve the oxidative stress in lesioned muscles. Copyright © 2016 Elsevier Inc. All rights reserved.

Effects of Bed Rest on Conduction Velocity of the Triceps Surae Stretch Reflex and Postural Control

NASA Technical Reports Server (NTRS)

Reschke, M. F.; Wood, S. J.; Cerisano, J. M.; Kofman, I. S.; Fisher, E. A.; Esteves, J. T.; Taylor, L. C.; DeDios, Y. E.; Harm, D. L.

2011-01-01

Despite rigorous exercise and nutritional management during space missions, astronauts returning from microgravity exhibit neuromuscular deficits and a significant loss in muscle mass in the postural muscles of the lower leg. Similar changes in the postural muscles occur in subjects participating in long-duration bed rest studies. These adaptive muscle changes manifest as a reduction in reflex conduction velocity during head-down bed rest. Because the stretch reflex encompasses both the peripheral (muscle spindle and nerve axon) and central (spinal synapse) components involved in adaptation to calf muscle unloading, it may be used to provide feedback on the general condition of neuromuscular function, and might be used to evaluate the effectiveness of countermeasures aimed at preserving muscle mass and function during periods of unloading. Stretch reflexes were measured on 18 control subjects who spent 60 to 90 days in continuous 6 deg head-down bed rest. Using a motorized system capable of rotating the foot around the ankle joint (dorsiflexion) through an angle of 10 degrees at a peak velocity of about 250 deg/sec, a stretch reflex was recorded from the subject's left triceps surae muscle group. Using surface electromyography, about 300 reflex responses were obtained and ensemble-averaged on 3 separate days before bed rest, 3 to 4 times in bed, and 3 times after bed rest. The averaged responses for each test day were examined for reflex latency and conduction velocity (CV) across gender. Computerized posturography was also conducted on these same subjects before and after bed rest as part of the standard measures. Peak-to-peak sway was measured during Sensory Organization Tests (SOTs) to evaluate changes in the ability to effectively use or suppress visual, vestibular, and proprioceptive information for postural control. Although no gender differences were found, a significant increase in reflex latency and a significant decrease in CV were observed during the bed

Chronic Quadriceps Tendon Rupture After Total Knee Arthroplasty Augmented With Synthetic Mesh.

PubMed

Ormaza, Amaia; Moreta, Jesús; Mosquera, Javier; de Ugarte, Oskar Sáez; Mozos, José Luis Martinez-de Los

2017-01-01

Tear of the quadriceps tendon after revision or primary total knee arthroplasty is a rare complication, but when it occurs, this injury has serious functional consequences. In complete tears, the outcome of direct repair is unpredictable, and several authors recommend that the suture should be reinforced. Several techniques have been described, including the use of autografts, allografts, and synthetic mesh. The goal of this study was to assess the outcomes of a reconstruction technique augmented with synthetic mesh. A retrospective study was performed involving 3 patients who had chronic partial quadriceps tendon tear after total knee revision. In 2 cases, proximal quadriceps release was performed. When conservative management failed, surgical reconstruction with suture reinforced with synthetic mesh was attempted. The knee was immobilized in full extension for 6 weeks after the surgical procedure. A minimum follow-up of 12 months was required to assess results. All reconstructions showed clinical success at a mean follow-up of 19 months. Mean Knee Society Score improved from 55.7 to 87.3, with average postoperative extensor lag of 3.3° (range, 0°-10°). The mean visual analog scale pain score was 2.3 (range, 0-4). No complications were reported. Synthetic mesh has previously been shown to be an effective treatment for patellar tendon repairs after total knee replacement, but there have been few articles on quadriceps rupture. Surgical reconstruction with synthetic mesh is a viable option that provides good functional outcomes in chronic quadriceps tendon rupture after total knee arthroplasty. [Orthopedics. 2017; 40(1):38-42.]. Copyright 2016, SLACK Incorporated.

Serial Changes of Quadriceps and Hamstring Muscle Strength Following Total Knee Arthroplasty: A Meta-Analysis

PubMed Central

Ahn, Hyeong-Sik; Lee, Dae-Hee

2016-01-01

This meta-analysis was performed to analyze serial changes in thigh muscles, including quadriceps and hamstring muscles, from before to one year after total knee arthroplasty (TKA). All studies sequentially comparing isokinetic quadriceps and hamstring muscle strengths between the TKA side and the contralateral uninjured limb were included in this meta-analysis. Five studies with 7 cohorts were included in this meta-analysis. The mean differences in the strengths of quadriceps and hamstring muscles between the TKA and uninjured sides were greatest three months after surgery (26.8 N∙m, 12.8 N∙m, P<0.001), but were similar to preoperative level at six months (18.4 N∙m, 7.4 N∙m P<0.001) and were maintained for up to one year (15.9 N∙m, 4.1 N∙m P<0.001). The pooled mean differences in changes in quadriceps and hamstring strengths relative to preoperative levels were 9.2 N∙m and 4.9 N∙m, respectively, three months postoperatively (P = 0.041), but were no longer significant after six months and one year. During the year after TKA, quadriceps and hamstring muscle strengths were lowest after 3 months, recovering to preoperative level after six months, but not reaching the muscle strength on the contralateral side. Relative to preoperative levels, the difference in muscle strength between the TKA and contralateral knees was only significant at three months. Because decrease of strength of the quadriceps was significantly greater than decrease in hamstring muscle strength at postoperative three months, early rehabilitation after TKA should focus on recovery of quadriceps muscle strength. PMID:26849808

Iterated Stretching of Viscoelastic Jets

NASA Technical Reports Server (NTRS)

Chang, Hsueh-Chia; Demekhin, Evgeny A.; Kalaidin, Evgeny

1999-01-01

We examine, with asymptotic analysis and numerical simulation, the iterated stretching dynamics of FENE and Oldroyd-B jets of initial radius r(sub 0), shear viscosity nu, Weissenberg number We, retardation number S, and capillary number Ca. The usual Rayleigh instability stretches the local uniaxial extensional flow region near a minimum in jet radius into a primary filament of radius [Ca(1 - S)/ We](sup 1/2)r(sub 0) between two beads. The strain-rate within the filament remains constant while its radius (elastic stress) decreases (increases) exponentially in time with a long elastic relaxation time 3We(r(sup 2, sub 0)/nu). Instabilities convected from the bead relieve the tension at the necks during this slow elastic drainage and trigger a filament recoil. Secondary filaments then form at the necks from the resulting stretching. This iterated stretching is predicted to occur successively to generate high-generation filaments of radius r(sub n), (r(sub n)/r(sub 0)) = square root of 2[r(sub n-1)/r(sub 0)](sup 3/2) until finite-extensibility effects set in.

Rosidal K: a short-stretch compression bandage system.

PubMed

Williams, C

Management of venous leg ulcers account for a large proportion of the work of healthcare professionals, especially for those who are community based. Multilayer and long-stretch bandage systems have been used successfully for many years in venous leg ulcer management. Rosidal K, a short-stretch bandage, is now also becoming more widely accepted in this country as an effective and cost-effective bandage system. This product focus looks at bandage systems and examines the research supporting the use of short-stretch bandages and Rosidal K.

Contributions of neural excitability and voluntary activation to quadriceps muscle strength following anterior cruciate ligament reconstruction.

PubMed

Lepley, Adam S; Ericksen, Hayley M; Sohn, David H; Pietrosimone, Brian G

2014-06-01

Persistent quadriceps weakness is common following anterior cruciate ligament reconstruction (ACLr). Alterations in spinal-reflexive excitability, corticospinal excitability and voluntary activation have been hypothesized as underlying mechanisms contributing to quadriceps weakness. The aim of this study was to evaluate the predictive capabilities of spinal-reflexive excitability, corticospinal excitability and voluntary activation on quadriceps strength in healthy and ACLr participants. Quadriceps strength was measured using maximal voluntary isometric contractions (MVIC). Voluntary activation was quantified via the central activation ratio (CAR). Corticospinal and spinal-reflexive excitability were measured using active motor thresholds (AMT) and Hoffmann reflexes normalized to maximal muscle responses (H:M), respectively. ACLr individuals were also split into high and low strength subsets based on MVIC. CAR was the only significant predictor in the healthy group. In the ACLr group, CAR and H:M significantly predicted 47% of the variance in MVIC. ACLr individuals in the high strength subset demonstrated significantly higher CAR and H:M than those in the low strength subset. Increased quadriceps voluntary activation, spinal-reflexive excitability and corticospinal excitability relates to increased quadriceps strength in participants following ACLr. Rehabilitation strategies used to target neural alterations may be beneficial for the restoration of muscle strength following ACLr. Copyright © 2014 Elsevier B.V. All rights reserved.

Innovative neurophysiological methods in itch research: long-latency evoked potentials after electrical and thermal stimulation in patients with atopic dermatitis.

PubMed

Yudina, Marina M; Toropina, Galina G; Lvov, Andrey; Gieler, Uwe

2011-10-01

The aim of this study was to examine the findings of innovative neurophysiological methods of itch research. Short-latency and pain-related somatosensory-evoked potentials after electrical stimulation, as well as long-latency evoked potentials after thermal stimulation were studied in 38 patients with atopic dermatitis (AD) and 26 healthy volunteers. Quantitative Sensory Testing of thermal perception was performed in 22 patients with AD from the main AD group and in 15 healthy volunteers. Brain hyperactivity to electrical stimuli, delayed thermal-evoked potentials and elevated thermal thresholds were revealed in patients with AD compared with healthy controls. The data indicate small nerve fibre dysfunction in patients with AD, which may contribute to the pathogenesis of AD and chronic itch. The study demonstrates objective approaches to assess the function of small nerve fibres in patients with chronic itch.

Joint awareness after total knee arthroplasty is affected by pain and quadriceps strength.

PubMed

Hiyama, Y; Wada, O; Nakakita, S; Mizuno, K

2016-06-01

There is a growing interest in the use of patient-reported outcomes to provide a more patient-centered view on treatment. Forgetting the artificial joint can be regarded as the goal in joint arthroplasty. The goals of the study were to describe changes in joint awareness in the artificial joint after total knee arthroplasty (TKA), and to determine which factors among pain, knee range of motion (ROM), quadriceps strength, and functional ability affect joint awareness after TKA. Patients undergoing TKA demonstrate changes in joint awareness and joint awareness is associated with pain, knee ROM, quadriceps strength, and functional ability. This prospective cohort study comprised 63 individuals undergoing TKA, evaluated at 1, 6, and 12 months postoperatively. Outcomes included joint awareness assessed using the Forgotten Joint Score (FJS), pain score, knee ROM, quadriceps strength, and functional ability. Fifty-eight individuals completed all postoperative assessments. All measures except for knee extension ROM improved from 1 to 6 months. However, there were no differences in any measures from 6 to 12 months. FJS was affected most greatly by pain at 1 month and by quadriceps strength at 6 and 12 months. Patients following TKA demonstrate improvements in joint awareness and function within 6 months after surgery, but reach a plateau from 6 to 12 months. Quadriceps strength could contribute to this plateau of joint awareness. Prospective cohort study, IV. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Healthy-side dominance of middle- and long-latency neuromagnetic fields in idiopathic sudden sensorineural hearing loss.

PubMed

Li, L P H; Shiao, A S; Chen, L F; Niddam, D M; Chang, S Y; Lien, C F; Lee, S K; Hsieh, J C

2006-08-01

Any lesion along the neural axis may induce a subsequent functional reorganization at the level above. The present study used magnetoencephalography to investigate auditory-evoked magnetic fields [a component of the middle-latency auditory evoked fields peaking at approximately 50 ms (P50m) and a component of the long-latency auditory evoked fields peaking at approximately 100 ms (N100m)] on stimulation of both healthy and affected ears in patients with acute unilateral idiopathic sudden sensorineural hearing loss (ISSNHL) of moderate degree in order to elucidate the functional plasticity of the auditory system. Sixteen right-handed, previously untreated adult patients with acute unilateral left (n = 8) or right (n = 8) ISSNHL of moderate degree were studied. Sixteen right-handed healthy volunteers with normal hearing served as control. Auditory neuromagnetic responses, measured by a whole-head 306-channel neuromagnetometer, were detected by monaural tone stimulation applied to affected and healthy ears, respectively, in different sessions. Intragroup and intergroup interhemispheric differences of peak dipole strengths and latencies of P50m and N100m, respectively, to monaural tones were evaluated. Healthy-side amplitude dominance of both P50m and N100m was found in ISSNHL, i.e. contralateral dominance was preserved on affected-ear stimulation but ipsilateral dominance was seen on healthy-ear stimulation. The phenomena could be attributed to the combined contralateral attenuation and ipsilateral enhancement of P50m and N100m activity in response to healthy-ear stimulation. Our findings confirmed that functional modulation can occur within the first few tens of milliseconds of evoked response at the auditory cortex in ISSNHL. The mechanisms of healthy-side dominance might be ascribed to a functional retune of auditory pathways, i.e. conjoined contralateral inhibition and ipsilateral excitation of the auditory pathway in response to healthy-ear stimulation. The

An Intelligent Computerized Stretch Reflex Measurement System For Clinical And Investigative Neurology

NASA Astrophysics Data System (ADS)

Flanagan, P. M.; Chutkow, J. G.; Riggs, M. T.; Cristiano, V. D.

1987-05-01

We describe the design of a reliable, user-friendly preprototype system for quantifying the tendon stretch reflexes in humans and large mammals. A hand-held, instrumented reflex gun, the impactor of which contains a single force sensor, interfaces with a computer. The resulting test system can deliver sequences of reproducible stimuli at graded intensities and adjustable durations to a muscle's tendon ("tendon taps"), measure the impacting force of each tap, and record the subsequent reflex muscle contraction from the same tendon -- all automatically. The parameters of the reflex muscle contraction include latency; mechanical threshold; and peak time, peak magnitude, and settling time. The results of clinical tests presented in this paper illustrate the system's potential usefulness in detecting neurologic dysfunction affecting the tendon stretch reflexes, in documenting the course of neurologic illnesses and their response to therapy, and in clinical and laboratory neurologic research.

Effect on Passive Range of Motion and Functional Correlates After a Long-Term Lower Limb Self-Stretch Program in Patients With Chronic Spastic Paresis.

PubMed

Pradines, Maud; Baude, Marjolaine; Marciniak, Christina; Francisco, Gerard; Gracies, Jean-Michel; Hutin, Emilie; Bayle, Nicolas

2018-03-02

In current health care systems, long-duration stretching, performed daily, cannot be obtained through prescriptions of physical therapy. In addition, the short-term efficacy of the various stretching techniques is disputed, and their long-term effects remain undocumented. To evaluate changes in extensibility in 6 lower limb muscles and in ambulation speed after a ≥1-year self-stretch program, the Guided Self-rehabilitation Contract (GSC), in individuals with chronic spastic paresis. Retrospective study comparing self-stretched and nonself-stretched muscles. Neurorehabilitation clinic. Patients diagnosed with hemiparesis or paraparesis at least 1 year before the initiation of a GSC and who were then involved in the GSC program for at least 1 year. For each patient, specific muscles were identified for intervention among the following: gluteus maximus, hamstrings, vastus, rectus femoris, soleus, and gastrocnemius. Prescriptions and training for a daily, high-load, prolonged, home self-stretching program were primarily based on the baseline coefficient of shortening, defined as C SH = [(X N -X V1 )/X N ] (X V1 = PROM, passive range of motion; X N = normally expected amplitude). Six assessments were performed per year, measuring the Tardieu X V1 or maximal slow stretch range of motion angle (PROM), C SH , 10-m ambulation speed, and its functional ambulation category (Perry's classification: household, limited, or full). Changes from baseline in self-stretched and nonself-stretched muscles were compared, with meaningful X V1 change defined as ΔX V1 >5° for plantar flexors and >10° for proximal muscles. Correlation between the composite X V1 (mean PROM for the 6 muscles) and ambulation speed also was evaluated. Twenty-seven GSC participants were identified (14 women, mean age 44 years, range 29-59): 18 with hemiparesis and 9 with paraparesis. After 1 year, 47% of self-stretched muscles showed meaningful change in PROM (ΔX V1 ) versus 14% in nonself-stretched

Quadriceps force and anterior tibial force occur obviously later than vertical ground reaction force: a simulation study.

PubMed

Ueno, Ryo; Ishida, Tomoya; Yamanaka, Masanori; Taniguchi, Shohei; Ikuta, Ryohei; Samukawa, Mina; Saito, Hiroshi; Tohyama, Harukazu

2017-11-18

Although it is well known that quadriceps force generates anterior tibial force, it has been unclear whether quadriceps force causes great anterior tibial force during the early phase of a landing task. The purpose of the present study was to examine whether the quadriceps force induced great anterior tibial force during the early phase of a landing task. Fourteen young, healthy, female subjects performed a single-leg landing task. Muscle force and anterior tibial force were estimated from motion capture data and synchronized force data from the force plate. One-way repeated measures analysis of variance and the post hoc Bonferroni test were conducted to compare the peak time of the vertical ground reaction force, quadriceps force and anterior tibial force during the single-leg landing. In addition, we examined the contribution of vertical and posterior ground reaction force, knee flexion angle and moment to peak quadriceps force using multiple linear regression. The peak times of the estimated quadriceps force (96.0 ± 23.0 ms) and anterior tibial force (111.9 ± 18.9 ms) were significantly later than that of the vertical ground reaction force (63.5 ± 6.8 ms) during the single-leg landing. The peak quadriceps force was positively correlated with the peak anterior tibial force (R = 0.953, P < 0.001). Multiple linear regression analysis showed that the peak knee flexion moment contributed significantly to the peak quadriceps force (R 2  = 0.778, P < 0.001). The peak times of the quadriceps force and the anterior tibial force were obviously later than that of the vertical ground reaction force for the female athletes during successful single-leg landings. Studies have reported that the peak time of the vertical ground reaction force was close to the time of anterior cruciate ligament (ACL) disruption in ACL injury cases. It is possible that early contraction of the quadriceps during landing might induce ACL disruption as a result of

Efficacy of kinesio taping on isokinetic quadriceps torque in knee osteoarthritis: a double blinded randomized controlled study.

PubMed

Anandkumar, Sudarshan; Sudarshan, Shobhalakshmi; Nagpal, Pratima

2014-08-01

Double blind pre-test post-test control group design. To compare the isokinetic quadriceps torque, standardized stair-climbing task (SSCT) and pain during SSCT between subjects diagnosed with knee osteoarthritis pre and post kinesio tape (KT) application with and without tension. Strength of the quadriceps and torque producing capability is frequently found to be compromised in knee osteoarthritis. The efficacy of KT in improving isokinetic quadriceps torque in knee osteoarthritis is unknown, forming the basis for this study. Forty subjects were randomly allocated to either the experimental (therapeutic KT with tension) or control group (sham KT without tension) with the allocation being concealed. Pre and post test measurements of isokinetic quadriceps torque, SSCT and pain during SSCT were carried out by a blinded assessor. A large effect size with significant improvements in the peak quadriceps torque (concentric and eccentric at angular velocities of 90° per second and 120° per second), SSCT and pain were obtained in the experimental group when compared to the control group. Application of therapeutic KT is effective in improving isokinetic quadriceps torque, SSCT and reducing pain in knee osteoarthritis.

Monitoring data transfer latency in CMS computing operations

DOE PAGES

Bonacorsi, Daniele; Diotalevi, Tommaso; Magini, Nicolo; ...

2015-12-23

During the first LHC run, the CMS experiment collected tens of Petabytes of collision and simulated data, which need to be distributed among dozens of computing centres with low latency in order to make efficient use of the resources. While the desired level of throughput has been successfully achieved, it is still common to observe transfer workflows that cannot reach full completion in a timely manner due to a small fraction of stuck files which require operator intervention.For this reason, in 2012 the CMS transfer management system, PhEDEx, was instrumented with a monitoring system to measure file transfer latencies, andmore » to predict the completion time for the transfer of a data set. The operators can detect abnormal patterns in transfer latencies while the transfer is still in progress, and monitor the long-term performance of the transfer infrastructure to plan the data placement strategy.Based on the data collected for one year with the latency monitoring system, we present a study on the different factors that contribute to transfer completion time. As case studies, we analyze several typical CMS transfer workflows, such as distribution of collision event data from CERN or upload of simulated event data from the Tier-2 centres to the archival Tier-1 centres. For each workflow, we present the typical patterns of transfer latencies that have been identified with the latency monitor.We identify the areas in PhEDEx where a development effort can reduce the latency, and we show how we are able to detect stuck transfers which need operator intervention. Lastly, we propose a set of metrics to alert about stuck subscriptions and prompt for manual intervention, with the aim of improving transfer completion times.« less

Monitoring data transfer latency in CMS computing operations

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

Bonacorsi, Daniele; Diotalevi, Tommaso; Magini, Nicolo

During the first LHC run, the CMS experiment collected tens of Petabytes of collision and simulated data, which need to be distributed among dozens of computing centres with low latency in order to make efficient use of the resources. While the desired level of throughput has been successfully achieved, it is still common to observe transfer workflows that cannot reach full completion in a timely manner due to a small fraction of stuck files which require operator intervention.For this reason, in 2012 the CMS transfer management system, PhEDEx, was instrumented with a monitoring system to measure file transfer latencies, andmore » to predict the completion time for the transfer of a data set. The operators can detect abnormal patterns in transfer latencies while the transfer is still in progress, and monitor the long-term performance of the transfer infrastructure to plan the data placement strategy.Based on the data collected for one year with the latency monitoring system, we present a study on the different factors that contribute to transfer completion time. As case studies, we analyze several typical CMS transfer workflows, such as distribution of collision event data from CERN or upload of simulated event data from the Tier-2 centres to the archival Tier-1 centres. For each workflow, we present the typical patterns of transfer latencies that have been identified with the latency monitor.We identify the areas in PhEDEx where a development effort can reduce the latency, and we show how we are able to detect stuck transfers which need operator intervention. Lastly, we propose a set of metrics to alert about stuck subscriptions and prompt for manual intervention, with the aim of improving transfer completion times.« less

Atrophy of the quadriceps muscle in children with a painful hip.

PubMed

Robben, S G; Lequin, M H; Meradji, M; Diepstraten, A F; Hop, W C

1999-09-01

The objective of this study was to determine the degree of muscle wasting of various components of the quadriceps muscle in children with a painful hip. Between January 1994 and September 1997, 327 consecutive children with a unilateral painful hip and/or limping were evaluated prospectively with ultrasonography. Quadriceps thickness was measured on both sides. Moreover, muscle thickness was measured in 59 control subjects. The patients were divided into eight groups; transient synovitis (n = 134), Perthes' disease (n = 35), slipped capital femoral epiphysis (n = 5), osteomyelitis (n = 4), aspecific synovitis (n = 5), rheumatoid arthritis (n = 3) and miscellaneous (n = 16). In 125 patients, no sonographic and radiological abnormalities were found and during follow-up the symptoms disappeared ('no pathology' group). Ipsilateral muscle wasting was present in all patient groups, whereas the control subjects showed no significant difference in muscle thickness between legs. The degree of muscle wasting was compared between transient synovitis, the 'no pathology' group, Perthes' disease and control subjects. For both quadriceps and vastus intermedius muscles, there was a significant difference between these groups, except between control subjects and the 'no pathology' group. For the rectus femoris muscle, there was a significant difference between these groups, except between transient synovitis and 'no pathology'. Muscle wasting showed a positive correlation with duration of symptoms and pre-existing muscle mass. In conclusion, different diseases show different degrees of muscle wasting, and there are different patterns of muscle wasting of various components of the quadriceps femoris muscle.

On the Prony series representation of stretched exponential relaxation

NASA Astrophysics Data System (ADS)

Mauro, John C.; Mauro, Yihong Z.

2018-09-01

Stretched exponential relaxation is a ubiquitous feature of homogeneous glasses. The stretched exponential decay function can be derived from the diffusion-trap model, which predicts certain critical values of the fractional stretching exponent, β. In practical implementations of glass relaxation models, it is computationally convenient to represent the stretched exponential function as a Prony series of simple exponentials. Here, we perform a comprehensive mathematical analysis of the Prony series approximation of the stretched exponential relaxation, including optimized coefficients for certain critical values of β. The fitting quality of the Prony series is analyzed as a function of the number of terms in the series. With a sufficient number of terms, the Prony series can accurately capture the time evolution of the stretched exponential function, including its "fat tail" at long times. However, it is unable to capture the divergence of the first-derivative of the stretched exponential function in the limit of zero time. We also present a frequency-domain analysis of the Prony series representation of the stretched exponential function and discuss its physical implications for the modeling of glass relaxation behavior.

Motoneuron excitability of the quadriceps decreases during a fatiguing submaximal isometric contraction.

PubMed

Finn, Harrison T; Rouffet, David M; Kennedy, David S; Green, Simon; Taylor, Janet L

2018-04-01

During fatiguing voluntary contractions, the excitability of motoneurons innervating arm muscles decreases. However, the behavior of motoneurons innervating quadriceps muscles is unclear. Findings may be inconsistent because descending cortical input influences motoneuron excitability and confounds measures during exercise. To overcome this limitation, we examined effects of fatigue on quadriceps motoneuron excitability tested during brief pauses in descending cortical drive after transcranial magnetic stimulation (TMS). Participants ( n = 14) performed brief (~5-s) isometric knee extension contractions before and after a 10-min sustained contraction at ~25% maximal electromyogram (EMG) of vastus medialis (VM) on one ( n = 5) or two ( n = 9) days. Electrical stimulation over thoracic spine elicited thoracic motor evoked potentials (TMEP) in quadriceps muscles during ongoing voluntary drive and 100 ms into the silent period following TMS (TMS-TMEP). Femoral nerve stimulation elicited maximal M-waves (M max ). On the 2 days, either large (~50% M max ) or small (~15% M max ) TMS-TMEPs were elicited. During the 10-min contraction, VM EMG was maintained ( P = 0.39), whereas force decreased by 52% (SD 13%) ( P < 0.001). TMEP area remained unchanged ( P = 0.9), whereas large TMS-TMEPs decreased by 49% (SD 28%) ( P = 0.001) and small TMS-TMEPs by 71% (SD 22%) ( P < 0.001). This decline was greater for small TMS-TMEPs ( P = 0.019; n = 9). Therefore, without the influence of descending drive, quadriceps TMS-TMEPs decreased during fatigue. The greater reduction for smaller responses, which tested motoneurons that were most active during the contraction, suggests a mechanism related to repetitive activity contributes to reduced quadriceps motoneuron excitability during fatigue. By contrast, the unchanged TMEP suggests that ongoing drive compensates for altered motoneuron excitability. NEW & NOTEWORTHY We provide evidence that the excitability of quadriceps

Stretch marks

MedlinePlus

Stretch marks can appear when there is rapid stretching of the skin. The marks appear as parallel ... often disappear after the cause of the skin stretching is gone. Avoiding rapid weight gain helps reduce ...

Quadriceps muscle injury in trans-femoral amputees.

PubMed

Alsindi, Z; Datta, D

1998-12-01

Two male trans-femoral amputees using modular trans-femoral prostheses lost control and fell to the ground when their prosthetic knees gave way. The semi-automatic knee lock malfunctioned in the first case while the free knee stabilising mechanics gave way in the second case. This resulted in a high tensile force acting on the contralateral quadriceps muscle causing it to rupture. As there are a significant number of patients with both kinds of prostheses it is important to be aware of this possibility so that necessary actions can be taken to minimise its occurrence. Even with the currently available weight activated stance phase control, the prosthetic knee will give way if the knee is flexed more than 20 degrees on weight bearing. Good power and control of hip extensors on the amputation side is needed to control the prosthetic knee joint, especially in the early stage of the walking cycle, i.e., from heel strike to mid-stance. Quadriceps muscle injury in amputees, as far as the authors are aware, has not been reported previously.

Isokinetic Hamstrings: Quadriceps Ratios in Intercollegiate Athletes.

ERIC Educational Resources Information Center

Rosene, John M.; Fogarty, Tracey D.; Mahaffey, Brian L.

2001-01-01

Compared the differences in the concentric hamstrings to quadriceps (H:Q) ratio among athletes in different sports at three velocities. Measurement of H:Q ratio of both knees among male and female college athletes indicated that the H:Q ratio increased as velocity increased. No differences existed for the H:Q ratio for sport or side of body. (SM)

Effects of electromyographic biofeedback on quadriceps strength: a systematic review.

PubMed

Lepley, Adam S; Gribble, Phillip A; Pietrosimone, Brian G

2012-03-01

Quadriceps strength is a vital component to lower extremity function and is often the focus in resistance training interventions and injury rehabilitation. Electromyographic biofeedback (EMGBF) is frequently used to supplement strength gains; however, the true effect remains unknown. Therefore, the objective of this investigation was to determine the magnitude of the treatment effect for EMGBF on quadriceps strength compared with that of placebo and traditional exercise interventions in both healthy and pathological populations. Web of Science and ProQuest databases were searched, and bibliographies of relevant articles were crossreferenced. Six articles measuring isometric quadriceps strength in response to EMGBF training were included and methodologically assessed using the Physiotherapy Evidence Database (PEDro). Standardized effect sizes with 95% confidence intervals (CIs) were calculated from preintervention and postintervention measures for EMGBF, placebo, and exercise-only interventions. Separate comparisons were made between studies assessing different intervention length (<4 and ≥4 weeks) and patient populations (pathological and healthy). Articles included received an average PEDro score of 6.5 ± 0.84. Homogeneous EMGBF effect sizes were found in all 6 studies (d = 0.01-5.56), with 4 studies reporting CI that crossed 0. A heterogeneous collection of effect sizes was found for exercise alone (d = -0.12 to 1.18) and placebo (d = -0.2 to 1.38), with 4 and 1 studies having a CI that crossed 0, respectively. The greatest EMGBF effects were found in pathological populations (d = 0.01-5.56), with the strongest effect found in the subjects with knee osteoarthritis (d = 5.56, CI = 4.26-6.68). As a group, effects were the strongest for EMGBF compared with that of placebo and exercise-only interventions, yet definitive evidence that EMGBF is beneficial for increasing quadriceps strength could not be concluded because of the 4 studies demonstrating a wide CI.

Quadriceps tendon rupture - treatment results.

PubMed

Popov, Iva; Ristić, Vladimir; Maljanović, Mirsad; Milankov, Vukadin

2013-01-01

Quadriceps tendon rupture is a rare but rather serious injury. If this injury is not promptly recognized and early operated, it may lead to disability. This research was aimed at pointing out the results and complications of the quadriceps tendon rupture surgical treatment. This retrospective multicentric study was conducted in a group of 29 patients (mostly elderly men). Lysholm knee scoring scale was used to evaluate the surgical results. The post-operative results were compared in relation to the type of tendon rupture reconstructions (acute or chronic), various surgical techniques, type of injuries (unilateral or bilateral) as well as the presence or absence of comorbid risk factors in the patients. The average value of a Lysholm score was 87.6. Excellent and satisfactory Lysholm score results dominated in our sample of patients. Better post-operative results were recorded in the group of patients without risk factors, in case of a bilateral injury, and in case of an acute injury. The best result was obtained after performing the reconstruction using anchors, and the worst result came after using Codivilla technique. Early diagnosis and surgical treatment are an absolute imperative in management of this injury. We have not proven that a certain surgical technique has an advantage over the others. A comorbid risk factor is related to a lower Lysholm score. Despite a few cases of complications, we can conclude that the surgical treatment yields satisfactory results.

Young Athletes With Quadriceps Femoris Strength Asymmetry at Return to Sport After Anterior Cruciate Ligament Reconstruction Demonstrate Asymmetric Single-Leg Drop-Landing Mechanics.

PubMed

Ithurburn, Matthew P; Paterno, Mark V; Ford, Kevin R; Hewett, Timothy E; Schmitt, Laura C

2015-11-01

Young athletes who have had anterior cruciate ligament (ACL) reconstruction demonstrate suboptimal rates of return to sport, high rates of second ACL injuries, and persistent movement asymmetries. Therefore, the influence of musculoskeletal impairments on movement mechanics in this population needs to be further evaluated. The primary hypothesis was that among young athletes who have had ACL reconstruction, those with greater quadriceps strength asymmetry would demonstrate altered single-leg drop-landing mechanics at return to sport compared with individuals with more symmetric quadriceps strength and also compared with healthy controls (ie, those with no ACL reconstruction). A second hypothesis was that quadriceps strength symmetry would predict single-leg drop-landing symmetry in individuals who have undergone ACL reconstruction. Controlled laboratory study. The study entailed a total of 103 participants (age, 17.4 years) at the time of return to sport after ACL reconstruction and 47 control participants (age, 17.0 years). The quadriceps index (QI) was calculated for isometric quadriceps strength, which was then used to divide the ACL reconstruction participants into high-quadriceps (QI ≥90%; n = 52) and low-quadriceps (QI <85%; n = 41) subgroups. Biomechanical data were collected by use of 3-dimensional motion analysis during a single-leg drop-landing task. The LSI was calculated for kinematic and kinetic sagittal-plane variables of interest during landing. Group differences were compared by use of 1-way analysis of variance and linear regression analyses (α < .05). Both the low- and high-quadriceps groups demonstrated greater limb asymmetry during landing compared with the control group in knee flexion excursion (mean LSI ± SD: low quadriceps, 85.8% ± 15.5% [P < .001]; high quadriceps, 94.2% ± 15.6% [P = .019]; control, 102.7% ± 14.1%), peak trunk flexion angle (low quadriceps, 129.2% ± 36.6% [P < .001]; high quadriceps, 110.5% ± 22.6% [P = .03

Implementation of Open and Closed Kinetic Chain Quadriceps Strengthening Exercises after Anterior Cruciate Ligament Reconstruction.

ERIC Educational Resources Information Center

Ross, Michael D.; Denegar, Craig R.; Winzenried, Jay A.

2001-01-01

Reviews the effects of open kinetic chain (OKC) and closed kinetic chain (CKC) exercise on anterior cruciate ligament (ACL) strain and patellofemoral joint stress, suggesting a combination of the two for quadriceps strengthening after ACL reconstruction. Both OKC and CKC exercises may be modified and implemented for quadriceps strengthening after…

Comparing the effects of eccentric training with eccentric training and static stretching exercises in the treatment of patellar tendinopathy. A controlled clinical trial.

PubMed

Dimitrios, Stasinopoulos; Pantelis, Manias; Kalliopi, Stasinopoulou

2012-05-01

The aim of the present study was to investigate the effectiveness of eccentric training and eccentric training with static stretching exercises in the management of patellar tendinopathy. Controlled clinical trial. Rheumatology and rehabilitation centre. Forty-three patients who had patellar tendinopathy for at least three months. They were allocated to two groups by alternative allocation. Group A (n = 22) was treated with eccentric training of patellar tendon and static stretching exercises of quadriceps and hamstrings and Group B (n = 21) received eccentric training of patellar tendon. All patients received five treatments per week for four weeks. Pain and function were evaluated using the VISA-P score at baseline, at the end of treatment (week 4), and six months (week 24) after the end of treatment. At the end of treatment, there was a rise in VISA-P score in both groups compared with baseline (P<0.0005, paired t test). There were significant differences in the VISA-P score between the groups at the end of treatment (+14; 10 to 18) and at the six-month follow-up (+19; 13 to 24); eccentric training and static stretching exercises produced the largest effect (P<0.0005, one-way ANOVA). Eccentric training and static stretching exercises is superior to eccentric training alone to reduce pain and improve function in patients with patellar tendinopathy at the end of the treatment and at follow-up.

THE EFFECTS OF VARIED TENSIONS OF KINESIOLOGY TAPING ON QUADRICEPS STRENGTH AND LOWER LIMB FUNCTION

PubMed Central

Franco, Yuri Rafael dos Santos; Nannini, Stella Bispo; Nakaoka, Gustavo Bezerra; dos Reis, Amir Curcio; Bryk, Flavio Fernandes

2017-01-01

Background Kinesiology Taping (KT) may promote changes in muscle strength and motor performance, topics of great interest in the sports-medicine sciences. These characteristics are purported to be associated with the tension generated by the KT on the skin. However, the most suitable tension for the attainment of these strength and performance effects has not yet been confirmed. Hypothesis/Purpose The purpose of the present study was to analyze the effects of different tensions of KT on the isometric contraction of the quadriceps and lower limb function of healthy individuals over a period of seven days. Study Design Blind, randomized, clinical trial. Methods One hundred and thirty healthy individuals were distributed into the following five groups: control (without KT); KT0 (KT without tension); KT50; KT75 and KT100 (approximately 50%, 75% and 100% tension applied to the tape, respectively). Assessments of isometric quadriceps strength were conducted using a hand held dynamometer. Lower limb function was assessed through Single Hop Test for Distance, with five measurement periods: baseline; immediately after KT application; three days after KT; five days after KT; and 72h after KT removal (follow-up). Results There were no statistically significant differences (p > 0.05) at any of the studied periods on participants’ quadriceps strength nor in the function of the lower dominant limb, based on comparisons between the control group and the experimental groups. Conclusion KT applied with different tensions did not produce modulations, in short or long-term, on quadriceps’ strength or lower limb function of healthy individuals. Therefore, this type of KT application, when seeking these objectives, should be reconsidered. Level of Evidence 1b PMID:28217419

Fatigue affects peak joint torque angle in hamstrings but not in quadriceps.

PubMed

Coratella, Giuseppe; Bellin, Giuseppe; Beato, Marco; Schena, Federico

2015-01-01

Primary aim of this study was to investigate peak joint torque angle (i.e. the angle of peak torque) changes recorded during an isokinetic test before and after a fatiguing soccer match simulation. Secondarily we want to investigate functional Hecc:Qconc and conventional Hconc:Qconc ratio changes due to fatigue. Before and after a standardised soccer match simulation, twenty-two healthy male amateur soccer players performed maximal isokinetic strength tests both for hamstrings and for quadriceps muscles at 1.05 rad · s(‒1), 3.14 rad · s(‒1) and 5.24 rad · s(‒1). Peak joint torque angle, peak torque and both functional Hecc:Qconc and conventional Hconc:Qconc ratios were examined. Both dominant and non-dominant limbs were tested. Peak joint torque angle significantly increased only in knee flexors. Both eccentric and concentric contractions resulted in such increment, which occurred in both limbs. No changes were found in quadriceps peak joint torque angle. Participants experienced a significant decrease in torque both in hamstrings and in quadriceps. Functional Hecc:Qconc ratio was lower only in dominant limb at higher velocities, while Hconc:Qconc did not change. This study showed after specific fatiguing task changes in hamstrings only torque/angle relationship. Hamstrings injury risk could depend on altered torque when knee is close to extension, coupled with a greater peak torque decrement compared to quadriceps. These results suggest the use eccentric based training to prevent hamstrings shift towards shorter length.

Selective hypertrophy of the quadriceps musculature after 14 weeks of isokinetic and conventional resistance training.

PubMed

Matta, Thiago Torres; Nascimento, Francisco Xavier; Trajano, Gabriel S; Simão, Roberto; Willardson, Jeffrey Michael; Oliveira, Liliam Fernandes

2017-03-01

One of the fundamental adaptations observed with resistance training (RT) is muscle hypertrophy. Conventional and isokinetic machines provide different forms of mechanical stress, and it is possible that these two training modes could promote differing degrees of hypertrophic adaptations. There is a lack of data comparing the selective hypertrophy of the quadriceps musculature after training with a conventional knee extension machine versus an isokinetic machine. The purpose of this study was to evaluate the selective hypertrophy of the quadriceps musculature and knee extension maximal isometric torque after 14 weeks of conventional versus isokinetic RT. Thirty-five men were assigned to three groups: control group and training groups (conventional and isokinetic) performed three sets of unilateral knee extensions per session with a progressive loading scheme twice a week. Prior to and following the intervention, maximal isometric knee extensor torque was measured using an isokinetic dynamometer, and muscle thickness (MT) of quadriceps femoris muscles was assessed via ultrasound. The results indicated non-uniform changes in MT between the muscles that comprise the quadriceps femoris group. For the conventional group, significantly greater increases in rectus femoris thickness were evident versus all other quadriceps muscles (14%). For the isokinetic group, increases in RF thickness (11%) were significantly greater in comparison with the vastus intermedius only. Although the muscle thickness did not increase for all the quadriceps femoris muscles, the relative rectus femoris adaptation suggested a selective hypertrophy favouring this portion. © 2015 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.

Quadriceps Muscle Function After Rehabilitation With Cryotherapy in Patients With Anterior Cruciate Ligament Reconstruction

PubMed Central

Hart, Joseph M.; Kuenze, Christopher M.; Diduch, David R.; Ingersoll, Christopher D.

2014-01-01

Context: Persistent muscle weakness after anterior cruciate ligament (ACL) reconstruction may be due to underlying activation failure and arthrogenic muscle inhibition (AMI). Knee-joint cryotherapy has been shown to improve quadriceps function transiently in those with AMI, thereby providing an opportunity to improve quadriceps muscle activation and strength in patients with a reconstructed ACL. Objective: To compare quadriceps muscle function in patients with a reconstructed ACL who completed a 2-week intervention including daily cryotherapy (ice bag), daily exercises, or both. Design: Cross-sectional study. Setting: Laboratory. Patients or Other Participants: A total of 30 patients with reconstructed ACLs who were at least 6 months post-index surgery and had measurable quadriceps AMI. Intervention(s): The patients attended 4 supervised visits over a 2-week period. They were randomly assigned to receive 20 minutes of knee-joint cryotherapy, 1 hour of therapeutic rehabilitation exercises, or cryotherapy followed by exercises. Main Outcome Measure(s): We measured quadriceps Hoffmann reflex, normalized maximal voluntary isometric contraction torque, central activation ratio using the superimposed-burst technique, and patient-reported outcomes before and after the intervention period. Results: After the 2-week intervention period, patients who performed rehabilitation exercises immediately after cryotherapy had higher normalized maximal voluntary isometric contraction torques (P = .002, Cohen d effect size = 1.4) compared with those who received cryotherapy alone (P = .16, d = 0.58) or performed exercise alone (P = .16, d = 0.30). Conclusions: After ACL reconstruction, patients with AMI who performed rehabilitation exercises immediately after cryotherapy experienced greater strength gains than those who performed cryotherapy or exercises alone. PMID:25299442

Polypropylene mesh augmentation for complete quadriceps rupture after total knee arthroplasty.

PubMed

Nodzo, Scott R; Rachala, Sridhar R

2016-01-01

Polypropylene mesh has previously been shown to be an effective treatment for failed patellar tendon repairs after total knee arthroplasty (TKA), but there have been few reports of this synthetic mesh used in complete quadriceps rupture after TKA. We retrospectively reviewed seven consecutive cases in six patients with complete quadriceps tears after TKA who had their quadriceps tendon repaired with suture and polypropylene mesh augmentation. All but two patients had previously failed primary suture repair. Patient outcomes were evaluated using the Knee Society Score. Standardized anterior-posterior (AP), lateral and merchant radiographs were evaluated preoperatively and at final follow-up. Seven knees in six patients were evaluated with a mean follow-up of 34±10 (range 24 to 49months) months. There were only four clinical successes defined as an extensor lag less than 30°. Of the functioning knees at final follow-up (n=5) the overall extensor lag in this group did significantly improve from 50±13° to 20±15° (range 5 to 40°) (p=.01). Mean postoperative flexion at final follow-up was 115±8°. Mean Knee Society Score for function improved from 20±30 to 45±54 (p=.03) as did the mean Knee Society Score for pain (44±18 vs. 74±78, p=.02). Polypropylene mesh offered limited postoperative functional results when used as an augment to the multiply operated knee that sustains a complete quadriceps rupture after TKA, but did allow for significant improvement in postoperative pain outcomes. IV. Copyright © 2015 Elsevier B.V. All rights reserved.

Stretching & Flexibility: An Interactive Encyclopedia of Stretching. [CD-ROM].

ERIC Educational Resources Information Center

2002

This CD-ROM offers 140 different stretches in full-motion video sequences. It focuses on the proper techniques for overall physical fitness, injury prevention and rehabilitation, and 23 different sports (e.g., golf, running, soccer, skiing, climbing, football, and baseball). Topics include stretching for sports; stretching awareness and education…

Orientation-specific responses to sustained uniaxial stretching in focal adhesion growth and turnover

PubMed Central

Chen, Yun; Pasapera, Ana M.; Koretsky, Alan P.; Waterman, Clare M.

2013-01-01

Cells are mechanosensitive to extracellular matrix (ECM) deformation, which can be caused by muscle contraction or changes in hydrostatic pressure. Focal adhesions (FAs) mediate the linkage between the cell and the ECM and initiate mechanically stimulated signaling events. We developed a stretching apparatus in which cells grown on fibronectin-coated elastic substrates can be stretched and imaged live to study how FAs dynamically respond to ECM deformation. Human bone osteosarcoma epithelial cell line U2OS was transfected with GFP-paxillin as an FA marker and subjected to sustained uniaxial stretching. Two responses at different timescales were observed: rapid FA growth within seconds after stretching, and delayed FA disassembly and loss of cell polarity that occurred over tens of minutes. Rapid FA growth occurred in all cells; however, delayed responses to stretch occurred in an orientation-specific manner, specifically in cells with their long axes perpendicular to the stretching direction, but not in cells with their long axes parallel to stretch. Pharmacological treatments demonstrated that FA kinase (FAK) promotes but Src inhibits rapid FA growth, whereas FAK, Src, and calpain 2 all contribute to delayed FA disassembly and loss of polarity in cells perpendicular to stretching. Immunostaining for phospho-FAK after stretching revealed that FAK activation was maximal at 5 s after stretching, specifically in FAs oriented perpendicular to stretch. We hypothesize that orientation-specific activation of strain/stress-sensitive proteins in FAs upstream to FAK and Src promote orientation-specific responses in FA growth and disassembly that mediate polarity rearrangement in response to sustained stretch. PMID:23754369

Atrophy of the Quadriceps Is Not Isolated to the Vastus Medialis Oblique in Individuals With Patellofemoral Pain.

PubMed

Giles, Lachlan S; Webster, Kate E; McClelland, Jodie A; Cook, Jill

2015-08-01

Cross-sectional. Objectives To determine if quadriceps atrophy was present in people with patellofemoral pain (PFP), and whether the vastus medialis oblique (VMO) was selectively involved. Despite the lack of research investigating individual quadriceps muscle size in individuals with PFP, it has been suggested that selective atrophy of the VMO relative to the vastus lateralis could be associated with PFP. The quadriceps muscle sizes of 35 participants with PFP (22 with unilateral and 13 with bilateral symptoms) and 35 asymptomatic control participants matched for age and sex were measured using real-time ultrasound. The thicknesses of the VMO, vastus lateralis, vastus medialis, rectus femoris, and vastus intermedius were measured. Paired-samples t tests were used to compare muscle thickness between limbs in those with unilateral PFP, and independent t tests were used to compare muscle thickness between groups with and without PFP. Results In those with unilateral PFP, the thickness of all portions of the quadriceps muscle was statistically smaller in the symptomatic compared to the asymptomatic limb: VMO (P = .038), vastus medialis (P<.001), vastus lateralis (P = .005), vastus intermedius (P = .013), and rectus femoris (P = .045). No difference was found in thickness of any of the portions of the quadriceps on the affected side of people with PFP compared to asymptomatic controls: VMO (P = .148), vastus medialis (P = .474), vastus lateralis (P = .122), vastus intermedius (P = .466), and rectus femoris (P = .508). Atrophy of all portions of the quadriceps muscles is present in the affected limb of people with unilateral PFP. There was no atrophy of the quadriceps in individuals with PFP compared to those without pathology. Selective atrophy of the VMO relative to the vastus lateralis was not identified in people with PFP.

Influence of patterned electrical neuromuscular stimulation on quadriceps activation in individuals with knee joint injury.

PubMed

Glaviano, Neal R; Langston, William T; Hart, Joseph M; Saliba, Susan

2014-12-01

Neuromuscular Electrical Stimulation is a common intervention to address muscle weakness, however presents with many limitations such as fatigue, muscle damage, and patient discomfort that may influence its effectiveness. One novel form of electrical stimulation purported to improve neuromuscular re-education is Patterned Electrical Neuromuscular Stimulation (PENS), which is proposed to mimic muscle-firing patterns of healthy individuals. PENS provides patterned stimulating to the agonist muscle, antagonist muscle and then agonist muscle again in an effort to replicate firing patterns. The purpose of this study was to determine the effect of a single PENS treatment on knee extension torque and quadriceps activation in individuals with quadriceps inhibition. 18 subjects (10 males and 8 females: 24.2±3.4 years, 175.3±11.8cm, 81.8±12.4kg) with a history of knee injury/pain participated in this double-blinded randomized controlled laboratory trial. Participants demonstrated quadriceps inhibition with a central activation ratio of ≤90%. Maximal voluntary isometric contraction of the quadriceps and central activation ratio were measured before and after treatment. The treatment intervention was a 15-minute patterned electrical stimulation applied to the quadriceps and hamstring muscles with a strong motor contraction or a sham group, who received an identical set up as the PENS group, but received a 1mA subsensory stimulation. A 2×2 (group × time) ANCOVA was used to determine differences in maximal voluntary isometric contraction and central activation ratio between groups. The maximal voluntary isometric contraction was selected as a covariate due to baseline differences. There were no differences in change scores between pre- and post-intervention for maximal voluntary isometric contraction: (PENS: 0.09±0.32Nm/kg and Sham 0.15±0.18Nm/kg, p=0.713), or central activation ratio:(PENS: -1.22±6.06 and Sham: 1.48±3.7, p=0.270). A single Patterned Electrical

Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction With a Free Quadriceps Tendon Autograft.

PubMed

Caterev, Sergiu; Nistor, Dan Viorel; Todor, Adrian

2016-10-01

Anatomic double-bundle anterior cruciate ligament (ACL) reconstruction aims to restore the 2 functional bundles of the ACL in an attempt to better reproduce the native biomechanics of the injured knee and promote long-term knee health. However, this concept is not fully accepted and is not performed on a standard basis. In addition, the superiority of this technique over the conventional single-bundle technique has been questioned, especially the long-term clinical results. One of the down sides of the double-bundle reconstruction is the complexity of the procedure, with increased risks, operative time, and costs compared with the single-bundle procedure. Also, the revision procedure, if necessary, is more challenging. We propose a technique that has some advantages over the traditional double-bundle procedure, using a single femoral tunnel, 2 tibial tunnels, and a free quadriceps tendon autograft.

Exercise-induced quadriceps muscle fatigue in men and women: effects of arterial oxygen content and respiratory muscle work.

PubMed

Dominelli, Paolo B; Molgat-Seon, Yannick; Griesdale, Donald E G; Peters, Carli M; Blouin, Jean-Sébastien; Sekhon, Mypinder; Dominelli, Giulio S; Henderson, William R; Foster, Glen E; Romer, Lee M; Koehle, Michael S; Sheel, A William

2017-08-01

High work of breathing and exercise-induced arterial hypoxaemia (EIAH) can decrease O 2 delivery and exacerbate exercise-induced quadriceps fatigue in healthy men. Women have a higher work of breathing during exercise, dedicate a greater fraction of whole-body V̇O2 towards their respiratory muscles and develop EIAH. Despite a greater reduction in men's work of breathing, the attenuation of quadriceps fatigue was similar between the sexes. The degree of EIAH was similar between sexes, and regardless of sex, those who developed the greatest hypoxaemia during exercise demonstrated the most attenuation of quadriceps fatigue. Based on our previous finding that women have a greater relative oxygen cost of breathing, women appear to be especially susceptible to work of breathing-related changes in quadriceps muscle fatigue. Reducing the work of breathing or eliminating exercise-induced arterial hypoxaemia (EIAH) during exercise decreases the severity of quadriceps fatigue in men. Women have a greater work of breathing during exercise, dedicate a greater fraction of whole-body V̇O2 towards their respiratory muscles, and demonstrate EIAH, suggesting women may be especially susceptible to quadriceps fatigue. Healthy subjects (8 male, 8 female) completed three constant load exercise tests over 4 days. During the first (control) test, subjects exercised at ∼85% of maximum while arterial blood gases and work of breathing were assessed. Subsequent constant load exercise tests were iso-time and iso-work rate, but with EIAH prevented by inspiring hyperoxic gas or work of breathing reduced via a proportional assist ventilator (PAV). Quadriceps fatigue was assessed by measuring force in response to femoral nerve stimulation. For both sexes, quadriceps force was equally reduced after the control trial (-27 ± 2% baseline) and was attenuated with hyperoxia and PAV (-18 ± 1 and -17 ± 2% baseline, P < 0.01, respectively), with no sex difference. EIAH was similar between

Quadriceps force during knee extension in different replacement scenarios with a modular partial prosthesis.

PubMed

Calliess, Tilman; Schado, Ssuheib; Richter, Berna I; Becher, Christoph; Ezechieli, Marco; Ostermeier, Sven

2014-02-01

Previous biomechanical studies have shown that bi-cruciate retaining knee replacement does not significantly alter normal knee kinematics, however, there are no data on the influence of a combined medial and patellofemoral bi-compartimental arthroplasty. The purpose of this in vitro study was to evaluate the effect of different replacement scenarios with a modular partial knee replacement system on the amount of quadriceps force required to extend the knee during an isokinetic extension cycle. Ten human knee specimens were tested in a kinematic knee simulator under (1) physiologic condition and after subsequent implantation of (2) a medial unicondylar and (3) a trochlear replacement. An isokinetic extension cycle of the knee with a constant extension moment of 31 Nm was simulated. The resulting quadriceps extension force was measured from 120° to full knee extension. The quadriceps force curve described a typically sinusoidal characteristic before and after each replacement scenario. The isolated medial replacement resulted in a slightly, but significantly higher maximum quadriceps force (1510 N vs. 1585 N, P = 0.006) as well as the subsequent trochlear replacement showed an additional increase (1801 N, P = 0.008). However, for both replacements no significant difference to the untreated condition could be detected in mid-flexion (10-50°). When considering a bi-compartimental replacement an increase of required maximum quadriceps force needed to extend the knee has to keep in mind. However, the close to physiological movement in mid-flexion suggests that patients with a bi-crutiate retaining arthroplasty might have an advantage in knee stability compared to total knee arthroplasty. Copyright © 2013 Elsevier Ltd. All rights reserved.

Quadriceps Weakness, Patella Alta and Structural Features of Patellofemoral Osteoarthritis: The Multicenter Osteoarthritis Study

PubMed Central

Stefanik, Joshua J.; Guermazi, Ali; Zhu, Yanyan; Zumwalt, Ann C.; Gross, K. Douglas; Clancy, Margaret; Lynch, John A.; Segal, Neil A.; Lewis, Cora E.; Roemer, Frank W.; Powers, Christopher M.; Felson, David T.

2011-01-01

Objective To determine the relationship between quadriceps weakness and cartilage damage and bone marrow lesions (BMLs) in the patellofemoral joint (PFJ), and if this relationship is modified by patella alta. Methods The Multicenter Osteoarthritis (MOST) Study is a cohort study of persons aged 50–79 years with or at risk for knee OA. Concentric knee extensor strength was measured using an isokinetic dynamometer. Patella alta was measured using the Insall-Salvati ratio (ISR) on the lateral radiograph, and cartilage damage and bone marrow lesions (BMLs) were graded on MRI in the PFJ. We determined the association between quadriceps weakness with cartilage damage and BMLs in the PFJ among those knees with (ISR≥1.2) and without patella alta (ISR<1.2) using multiple binomial regression. Results 807 knees were studied (mean age 62 years, BMI 30, ISR 1.10), 64% from female subjects. Compared with knees in the highest strength tertile, those in the lowest had 10.2% {95% Confidence Interval (CI) 3–18}, 9.1% (95% CI 2–16), and 7.1% (95% CI 1–13) higher prevalence of lateral PFJ cartilage damage, medial PFJ cartilage damage, and lateral PFJ BMLs, respectively. The association between quadriceps weakness with cartilage damage and BMLs was not different between knees with and with out patella alta in the lateral PFJ. Conclusion Quadriceps weakness was associated with PFJ cartilage damage and BMLs. While both patella alta and quadriceps weakness are associated with PFJ damage, the combination of the two was not associated with more damage than either of these factors alone. PMID:21702087

Relative Distribution of Quadriceps Head Anatomical Cross-Sectional Areas and Volumes – Sensitivity to Pain and to Training Intervention

PubMed Central

Sattler, M; Dannhauer, T; Ring-Dimitriou, S; Sänger, AM; Wirth, W; Hudelmaier, M; Eckstein, F

2014-01-01

SUMMARY Introduction Quadriceps heads are important in biomechanical stabilization and in the pathogenesis osteoarthritis of the knee. This is the first study to explore the relative distribution of quadriceps head anatomical cross-sectional areas (ACSA) and volumes, and their response to pain and to training intervention. Methods The relative proportions of quadriceps heads were determined in 48 Osteoarthritis Initiative participants with unilateral pain (65% women; age 45–78y). Quadriceps head volumes were also measured in 35 untrained women (45–55y) before and after 12 week training intervention. Cross-sectional areas of the vastus medialis (VM), inter-medius (VIM), and lateralis (VL), and of the rectus femoris (RF) were determined from axial T1-weighted MR images. Results The proportion of the VM on the total quadriceps ACSA increased from proximal to distal. The difference in quadriceps ACSA of painful (vs. pain-free) limbs was −5.4% for the VM (p<0.001), −6.8% for the VL (p<0.01), −2.8% for the VIM (p=0.06), and +3.4% for the RF (p=0.67) but the VM/VL ratio was not significantly altered. The muscle volume increase during training intervention was +4.2% (p<0.05) for VM, +1.3% for VL, +2.0% for VIM (p<0.05) and +1.6% for RF. Conclusion The proportion of quadriceps head relative to total muscle ACSA and volume depends on the anatomical level studied. The results suggest that there may be a differential response of the quadriceps heads to pain-induced atrophy and to training-related hypertrophy. Studies in larger samples are needed to ascertain whether the observed differences in response to pain and training are statistically and clinically significant. PMID:25153247

Long Noncoding RNA uc002yug.2 Activates HIV-1 Latency through Regulation of mRNA Levels of Various RUNX1 Isoforms and Increased Tat Expression.

PubMed

Huan, Chen; Li, Zhaolong; Ning, Shanshan; Wang, Hong; Yu, Xiao-Fang; Zhang, Wenyan

2018-05-01

The HIV-1 reservoir is a major obstacle to complete eradication of the virus. Although many proteins and RNAs have been characterized as regulators in HIV-1/AIDS pathogenesis and latency, only a few long noncoding RNAs (lncRNAs) have been shown to be closely associated with HIV-1 replication and latency. In this study, we demonstrated that lncRNA uc002yug.2 plays a key role in HIV-1 replication and latency. uc002yug.2 potentially enhances HIV-1 replication, long terminal repeat (LTR) activity, and the activation of latent HIV-1 in both cell lines and CD4 + T cells from patients. Further investigation revealed that uc002yug.2 activates latent HIV-1 through downregulating RUNX1b and -1c and upregulating Tat protein expression. The accumulated evidence supports our model that the Tat protein has the key role in the uc002yug.2-mediated regulatory effect on HIV-1 reactivation. Moreover, uc002yug.2 showed an ability to activate HIV-1 similar to that of suberoylanilide hydroxamic acid or phorbol 12-myristate 13-acetate using latently infected cell models. These findings improve our understanding of lncRNA regulation of HIV-1 replication and latency, providing new insights into potential targeted therapeutic interventions. IMPORTANCE The latent viral reservoir is the primary obstacle to curing HIV-1 disease. To date, only a few lncRNAs, which play major roles in various biological processes, including viral infection, have been identified as regulators in HIV-1 latency. In this study, we demonstrated that lncRNA uc002yug.2 is important for both HIV-1 replication and activation of latent viruses. Moreover, uc002yug.2 was shown to activate latent HIV-1 through regulating alternative splicing of RUNX1 and increasing the expression of Tat protein. These findings highlight the potential merit of targeting lncRNA uc002yug.2 as an activating agent for latent HIV-1. Copyright © 2018 American Society for Microbiology.

Telemetry System Data Latency

DTIC Science & Technology

2017-07-13

ec o n d s Data Rate TELEMETRY SYSTEM DATA LATENCY 15 of 31 Document: JT3-AFC-SRPT-17172-0005 Revision...250 So ft w ar e D ec o m L at en cy N T im es G re at er T h an D xD ec o m L at en cy Data Rate TELEMETRY SYSTEM DATA LATENCY 16 of...20.0 30.0 40.0 50.0 60.0 70.0 M ill is ec o n d s Data Rate TELEMETRY SYSTEM DATA LATENCY 17 of 31 Document:

Osgood-Schlatter Disease (For Parents)

MedlinePlus

... tightness of the muscles surrounding the knee (the hamstring and quadriceps muscles) Symptoms that aren't typical ... bruises. A good stretching program, focusing on the hamstring and quadriceps muscles, before and after activity is ...

Effects of long-term self-massage at the musculotendinous junction on hamstring extensibility, stiffness, stretch tolerance, and structural indices: A randomized controlled trial.

PubMed

Akazawa, Naoki; Okawa, Naomi; Kishi, Masaki; Nakatani, Kiyoshi; Nishikawa, Katsuya; Tokumura, Daichi; Matsui, Yuji; Moriyama, Hideki

2016-09-01

The purpose of this study was to examine the effect of long-term self-massage at the musculotendinous junction on hamstring extensibility, stiffness, stretch tolerance, and structural indices. Single-blind, randomized, controlled trial. Laboratory. Thirty-seven healthy men. The right or left leg of each participant was randomly assigned to the massage group, and the other leg was assigned to the control group. The participants conducted self-massage at the musculotendinous junction for 3 min daily, five times per week, for 12 weeks. Hamstring extensibility, stiffness, stretch tolerance, and structural indices were measured by a blinded examiner prior to the massage intervention and after 6 and 12 weeks of intervention. The maximum hip flexion angle (HFA) and the maximum passive pressure after 6 and 12 weeks of intervention in the massage group were significantly higher than prior to intervention. The visual analog scale (for pain perception) at maximum HFA, the stiffness of the hamstring, and the structural indices did not differ in either group over the 12 week period. Our results suggest that long-term self-massage at the musculotendinous junction increases hamstring extensibility by improving stretch tolerance. However, this intervention does not change hamstring stiffness. University Hospital Medical Information Network registration number UMIN000011233. Copyright © 2016 Elsevier Ltd. All rights reserved.

Proprioceptive reaction times and long-latency reflexes in humans.

PubMed

Manning, C D; Tolhurst, S A; Bawa, P

2012-08-01

The stretch of upper limb muscles results in two electromyographic (EMG) peaks, M1 and M2. The amplitude of M2 peak can generally be modified by giving prior instruction to the subject on how to react to the applied perturbation. The unresolved question is whether the amplitude modulation results from change in the gain of the reflex pathway contributing to M2, or by superposition of reaction time (RT) activity. The following study attempted to resolve this question by examining the overlap between proprioceptive RT and M2 activities. Subject's right wrist flexors were stretched, and he/she was instructed either (1) not to intervene (passive task) or (2) to react as fast as possible by simultaneously flexing both wrists (active or compensate task). Under passive and active conditions, M1 and M2 were observed from EMG of right wrist flexors, and during the active condition, RT activities were additionally observed from both sides. The onset and offset of M2 (M1(onset), M2(offset)) were measured from the passive averages, while the RT was measured from the averaged EMG response of the left wrist flexors. For between-subject correlations, the data were divided into two sets: (1) subjects with RT shorter than M2(offset) (fast group) and (2) subjects with RT more than 10 ms longer than their M2(offset) (slow group). Modulation during M2 period was large for the fast group, and it was almost zero for the slow group. These results indicate that the superimposition of RT activity mainly contributes to the instruction-dependent modulation of M2 peak.

Functional difference in short- and long-latency interhemispheric inhibitions from active to resting hemisphere during a unilateral muscle contraction.

PubMed

Uehara, Kazumasa; Morishita, Takuya; Kubota, Shinji; Hirano, Masato; Funase, Kozo

2014-01-01

The aim of the present study was to investigate whether there is a functional difference in short-latency (SIHI) and long-latency (LIHI) interhemispheric inhibition from the active to the resting primary motor cortex (M1) with paired-pulse transcranial magnetic stimulation during a unilateral muscle contraction. In nine healthy right-handed participants, IHI was tested from the dominant to the nondominant M1 and vice versa under resting conditions or during performance of a sustained unilateral muscle contraction with the right or left first dorsal interosseous muscle at 10% and 30% maximum voluntary contraction. To obtain measurements of SIHI and LIHI, a conditioning stimulus (CS) was applied over the M1 contralateral to the muscle contraction, followed by a test stimulus over the M1 ipsilateral to the muscle contraction at short (10 ms) and long (40 ms) interstimulus intervals. We used four CS intensities to investigate SIHI and LIHI from the active to the resting M1 systematically. The amount of IHI during the unilateral muscle contractions showed a significant difference between SIHI and LIHI, but the amount of IHI during the resting condition did not. In particular, SIHI during the muscle contractions, but not LIHI, significantly increased with increase in CS intensity compared with the resting condition. Laterality of IHI was not detected in any of the experimental conditions. The present study provides novel evidence that a functional difference between SIHI and LIHI from the active to the resting M1 exists during unilateral muscle contractions.

Consistent latencies of vestibular evoked myogenic potentials.

PubMed

Wang, Shou-Jen; Yeh, Te-Huei; Chang, Chun-Hsiang; Young, Yi-Ho

2008-12-01

This study investigated the association between neck length and vestibular evoked myogenic potential (VEMP) latencies in healthy children, adolescents, and adults to elucidate when VEMP latencies reach consistent levels. Findings of VEMP tests in 14 healthy children, seven healthy adolescents, and 14 healthy adults were analyzed for correlations with neck length, which was measured as the distance of a line dropping vertically from the mastoid tip to the horizontal plane passing through the clavicle. All healthy children, adolescents, and adults exhibited present VEMP responses. Children, adolescents, and adults significantly differed in p13 latency, n23 latency, and p13-n23 interval. According to receiver operating characteristic curve analysis, the optimal cutoff values of p13 and n23 latencies between children and adults were 12.6 and 19.8 msec, respectively. Because the odds ratio of p13 latency was less than that of n23 latency, n23 latency was used to discriminate VEMP latencies between children and adults. Accordingly, a cutoff value of 15.3 cm for neck length was proposed as a criterion for predicting VEMP latency within the adult range. Consequently, a positive correlation between neck length and VEMP latency was observed when neck length was <15.3 cm, while above which level one need not account for neck length in evaluating VEMP latency. The intra-subject variability of norms can be enhanced if the normative data for VEMP characteristic parameters take structural variance into account. This study suggests that the adult range of VEMP latencies can be anticipated if neck length is >15.3 cm.

Effects of physical therapist-guided quadriceps-strengthening exercises for the treatment of patellofemoral pain syndrome: a systematic review.

PubMed

Kooiker, Laura; Van De Port, Ingrid G L; Weir, Adam; Moen, Maarten H

2014-06-01

Systematic literature review. To summarize the evidence for physical therapist-guided quadriceps-strengthening exercises as a treatment for patellofemoral pain syndrome. Although quadriceps strengthening is often included in the plan of care for patellofemoral pain syndrome, a systematic review published in 2003 found only limited evidence that exercise was more effective than no exercise for this common condition. The PubMed, Embase/MEDLINE, and Cochrane Central Register of Controlled Trials databases, from inception to January 9, 2014, were searched for randomized controlled trials comparing the use of quadriceps-strengthening exercises to interventions consisting of advice/information or a placebo. Outcomes of interest were pain measures and function, as measured with self-report questionnaires. The methodological quality of the randomized controlled trials was assessed with the Physiotherapy Evidence Database scale. Results were summarized using a best-evidence synthesis and graphically illustrated using forest plots without meta-analysis. Seven studies were included in the literature review. These studies reported strong evidence that isolated quadriceps strengthening is more effective in reducing pain and improving function than advice and information alone. In addition, compared to advice and information or placebo, there was strong evidence that quadriceps-strengthening exercises combined with other interventions may be more effective in reducing pain immediately postintervention and after 12 months, but not in improving function. The literature provides strong evidence for the use of quadriceps-strengthening exercises, with or without other interventions, for the treatment of patellofemoral pain syndrome.

Orientation and length of mammalian skeletal myocytes in response to a unidirectional stretch

NASA Technical Reports Server (NTRS)

Collinsworth, A. M.; Torgan, C. E.; Nagda, S. N.; Rajalingam, R. J.; Kraus, W. E.; Truskey, G. A.

2000-01-01

Effects of mechanical forces exerted on mammalian skeletal muscle cells during development were studied using an in vitro model to unidirectionally stretch cultured C2C12 cells grown on silastic membrane. Previous models to date have not studied these responses of the mammalian system specifically. The silastic membrane upon which these cells were grown exhibited linear strain behavior over the range of 3.6-14.6% strain, with a Poisson's ratio of approximately 0.5. To mimic murine in utero long bone growth, cell substrates were stretched at an average strain rate of 2.36%/day for 4 days or 1.77%/day for 6 days with an overall membrane strain of 9.5% and 10.6%, respectively. Both control and stretched fibers stained positively for the contractile protein, alpha-actinin, demonstrating muscle fiber development. An effect of stretch on orientation and length of myofibers was observed. At both strain rates, stretched fibers aligned at a smaller angle relative to the direction of stretch and were significantly longer compared to randomly oriented control fibers. There was no effect of duration of stretch on orientation or length, suggesting the cellular responses are independent of strain rate for the range tested. These results demonstrate that, under conditions simulating mammalian long bone growth, cultured myocytes respond to mechanical forces by lengthening and orienting along the direction of stretch.

Biomechanical Evaluation of Suture Anchor Versus Transosseous Tunnel Quadriceps Tendon Repair Techniques.

PubMed

Sherman, Seth L; Copeland, Marilyn E; Milles, Jeffrey L; Flood, David A; Pfeiffer, Ferris M

2016-06-01

To evaluate the biomechanical fixation strength of suture anchor and transosseous tunnel repair of the quadriceps tendon in a standardized cadaveric repair model. Twelve "patella-only" specimens were used. Dual-energy X-ray absorptiometry measurement was performed to ensure equal bone quality amongst groups. Specimens were randomly assigned to either a suture anchor repair of quadriceps tendon group (n = 6) or a transosseous tunnel repair group (n = 6). Suture type and repair configuration were equivalent. After the respective procedures were performed, each patella was mounted into a gripping jig. Tensile load was applied at a rate of 0.1 mm/s up to 100 N after which cyclic loading was applied at a rate of 1 Hz between magnitudes of 50 to 150 N, 50 to 200 N, 50 to 250 N, and tensile load at a rate of 0.1 mm/s until failure. Outcome measures included load to failure, displacement at 1st 100 N load, and displacement after each 10th cycle of loading. The measured cyclic displacement to the first 100 N, 50 to 150 N, 50 to 200 N, and 50 to 250 N was significantly less for suture anchors than transosseous tunnels. There was no statistically significant difference in ultimate load to failure between the 2 groups (P = .40). Failure mode for all suture anchors except one was through the soft tissue. Failure mode for all transosseous specimens but one was pulling the repair through the transosseous tunnel. Suture anchor quadriceps tendon repairs had significantly decreased gapping during cyclic loading, but no statistically significant difference in ultimate load to failure when compared with transosseous tunnel repairs. Although suture anchor quadriceps tendon repair appears to be a biomechanically superior construct, a clinical study is needed to confirm this technique as a viable alternative to gold standard transosseous techniques. Although in vivo studies are needed, these results support the suture anchor technique as a viable alternative to

VIEW OF INTERIOR SPACE WITH SQUARE SHAPE STRETCH PRESS CONTAINMENT ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

VIEW OF INTERIOR SPACE WITH SQUARE SHAPE STRETCH PRESS CONTAINMENT PITS CENTER, FACING NORTH. - Douglas Aircraft Company Long Beach Plant, Aircraft Parts Shipping & Receiving Building, 3855 Lakewood Boulevard, Long Beach, Los Angeles County, CA

VIEW OF INTERIOR SPACE WITH RECTANGULAR SHAPE STRETCH PRESS CONTAINMENT ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

VIEW OF INTERIOR SPACE WITH RECTANGULAR SHAPE STRETCH PRESS CONTAINMENT PIT IN BACKGROUND, FACING NORTH. - Douglas Aircraft Company Long Beach Plant, Aircraft Parts Shipping & Receiving Building, 3855 Lakewood Boulevard, Long Beach, Los Angeles County, CA

Interactions between Herpesvirus Entry Mediator (TNFRSF14) and Latency-Associated Transcript during Herpes Simplex Virus 1 Latency

PubMed Central

Allen, Sariah J.; Rhode-Kurnow, Antje; Mott, Kevin R.; Jiang, Xianzhi; Carpenter, Dale; Rodriguez-Barbosa, J. Ignacio; Jones, Clinton; Wechsler, Steven L.; Ware, Carl F.

2014-01-01

Herpesvirus entry mediator (HVEM) is one of several cell surface proteins herpes simplex virus (HSV) uses for attachment/entry. HVEM regulates cellular immune responses and can also increase cell survival. Interestingly, latency-associated transcript (LAT), the only viral gene consistently expressed during neuronal latency, enhances latency and reactivation by promoting cell survival and by helping the virus evade the host immune response. However, the mechanisms of these LAT activities are not well understood. We show here for the first time that one mechanism by which LAT enhances latency and reactivation appears to be by upregulating HVEM expression. HSV-1 latency/reactivation was significantly reduced in Hvem−/− mice, indicating that HVEM plays a significant role in HSV-1 latency/reactivation. Furthermore, LAT upregulated HVEM expression during latency in vivo and also when expressed in vitro in the absence of other viral factors. This study suggests a mechanism whereby LAT upregulates HVEM expression potentially through binding of two LAT small noncoding RNAs to the HVEM promoter and that the increased HVEM then leads to downregulation of immune responses in the latent microenvironment and increased survival of latently infected cells. Thus, one of the mechanisms by which LAT enhances latency/reactivation appears to be through increasing expression of HVEM. PMID:24307582

ACL deficient potential copers and non-copers reveal different isokinetic quadriceps strength profiles in the early stage after injury

PubMed Central

Eitzen, I; Eitzen, TJ; Holm, I; Snyder-Mackler, L; Risberg, MA

2011-01-01

Background Isokinetic muscle strength tests using the peak torque value is the most frequently included quadriceps muscle strength measurement for anterior cruciate ligament (ACL) injured subjects. Aims The purpose of this study was to investigate quadriceps muscle performance during the whole isokinetic curve in ACL deficient subjects classified as potential copers or non-copers, and investigate whether these curve profiles were associated with single-leg hop performance. We hypothesized that quadriceps muscle torque at other knee flexion angles than peak torque would give more information about quadriceps muscle strength deficits. Furthermore, we hypothesized that there would be significant torque differences between potential copers and non-copers, and a significant relationship between angle specific torque values and single-leg hop performance. Study Design Cross-sectional study; Level of evidence, 2 Methods Seventy-six individuals with a complete unilateral ACL rupture within the last 3 months were included. The subjects were classified into potential copers and non-copers according to the criteria from Fitzgerald et al12. Isokinetic quadriceps muscle tests were performed at 60°/sec (Biodex 6000). Mean torque values were calculated for peak torque as well as for specific knee flexion angles. The one-leg hop and the 6 meter timed hop tests were included and symmetry indices were used. Results The peak torque value did not identify the largest quadriceps muscle strength deficit. Rather, these were established at knee flexion angles of less than 40°. There were significant differences in angle specific torque values between potential copers and non-copers (p<0.05). Moderate to strong associations were disclosed between angle specific torque values and single-leg hop performance, but only for non-copers (r≥0.32– 0.58). Conclusions Angle specific quadriceps muscle torque values of less than 40° of knee flexion provide more information on the quadriceps

Validation of Bedside Ultrasound of Muscle Layer Thickness of the Quadriceps in the Critically Ill Patient (VALIDUM Study).

PubMed

Paris, Michael T; Mourtzakis, Marina; Day, Andrew; Leung, Roger; Watharkar, Snehal; Kozar, Rosemary; Earthman, Carrie; Kuchnia, Adam; Dhaliwal, Rupinder; Moisey, Lesley; Compher, Charlene; Martin, Niels; Nicolo, Michelle; White, Tom; Roosevelt, Hannah; Peterson, Sarah; Heyland, Daren K

2017-02-01

In critically ill patients, muscle atrophy is associated with long-term disability and mortality. Bedside ultrasound may quantify muscle mass, but it has not been validated in the intensive care unit (ICU). Here, we compared ultrasound-based quadriceps muscle layer thickness (QMLT) with precise quantifications of computed tomography (CT)-based muscle cross-sectional area (CSA). Patients ≥18 years old with abdominal CT scans performed for clinical reasons were recruited from 9 ICUs for an ultrasound assessment of the quadriceps. CT scans of the third lumbar vertebra, performed <24 hours before or <72 hours after ICU admission, were analyzed for CSA. Low muscularity was defined as 170 cm 2 for men and 110 cm 2 for women. The ultrasound probe was maximally compressed against the skin and QMLT was measured on 2 sites of each quadriceps <72 hours of the CT scan. Mean CT-derived muscle CSA was 109 ± 25 cm 2 for women and 168 ± 37 cm 2 for men, where 58% of patients exhibited low muscularity; only 2.7% patients were underweight according to body mass index. QMLT was positively correlated with CT CSA ( r = 0.45, P < .001). Based on logistic regression to predict low muscularity, QMLT independently generated a concordance index ( c) of 0.67 ( P < .002), which increased to 0.77 ( P < .001) when age, sex, body mass index, Charlson Comorbidity Index, and admission type (surgical vs medical) were added. Our results suggest that QMLT alone with our current protocol may not accurately identify patients with low muscle mass.

Effect of isometric quadriceps exercise on muscle strength, pain, and function in patients with knee osteoarthritis: a randomized controlled study.

PubMed

Anwer, Shahnawaz; Alghadir, Ahmad

2014-05-01

[Purpose] The aim of present study was to investigate the effects of isometric quadriceps exercise on muscle strength, pain, and function in knee osteoarthritis. [Subjects and Methods] Outpatients (N=42, 21 per group; age range 40-65 years; 13 men and 29 women) with osteoarthritis of the knee participated in the study. The experimental group performed isometric exercises including isometric quadriceps, straight leg raising, and isometric hip adduction exercise 5 days a week for 5 weeks, whereas the control group did not performed any exercise program. The outcome measures or dependent variables selected for this study were pain intensity, isometric quadriceps strength, and knee function. These variables were measured using the Numerical Rating Scale (NRS), strength gauge device, and reduced WOMAC index, respectively. All the measurements were taken at baseline (week 0) and at the end of the trial at week 5. [Results] In between-group comparisons, the maximum isometric quadriceps strength, reduction in pain intensity, and improvement in function in the isometric exercise group at the end of the 5th week were significantly greater than those of the control group (p<0.05). [Conclusion] The 5-week isometric quadriceps exercise program showed beneficial effects on quadriceps muscle strength, pain, and functional disability in patients with osteoarthritis of the knee.

Stretch Marks

MedlinePlus

... stretch marks. This isn't true with regular tanning or tanning beds , though: Stretch marks are less likely to ... up looking more obvious. Plus, the sun and tanning beds do more harm than good when it ...

Stretch Garment Dermatitis

PubMed Central

Mihan, Richard; Ayres, Samuel

1968-01-01

A disease of the skin, not hitherto described, is caused by pressure or tension on the skin from the wearing of tight-fitting stretch garments such as “stretch bras,” “stretch girdles” and “stretch socks.” The condition is not due to chemical sensitization of fabrics, dyes or other additives but is of mechanical origin. The eruption may assume various clinical forms and may be characterized by a nondescript erythematous and eczematous appearance or may consist of an exaggeration, in the areas covered by the stretch garment, of already existing dermatosis such as lichen planus, psoriasis, acne vulgaris, discoid lupus erythematosus or atopic dermatitis. ImagesFigure 1.Figure 2.Figure 3.Figure 4.Figure 5. PMID:5639939

Evaluation of Electromyographic Biofeedback for the Quadriceps Femoris: A Systematic Review

PubMed Central

Wasielewski, Noah J.; Parker, Tonya M.; Kotsko, Kevin M.

2011-01-01

Objective: To critically review evidence for the effectiveness of electromyographic biofeedback (EMGB) of the quadriceps femoris muscle in treating various knee conditions. Data Sources: Databases used to locate randomized controlled trials included PubMed (1980–2010), Cumulative Index of Nursing and Allied Health Literature (CINAHL, 1995–2007), Web of Science (1986–2010), SPORTDiscus (1990–2007), and Physiotherapy Evidence Database (PEDro). Key words were knee and biofeedback. Study Selection: The criteria for selection were clinical randomized controlled trials in which EMGB of the quadriceps femoris was used for various knee conditions of musculoskeletal origin. Trials were excluded because of research designs other than randomized controlled trials, articles published in a non-English language, inclusion of healthy research participants, inability to identify EMGB as the source of clinical improvement, and lack of pain, functional outcome, or quadriceps torque as outcome measures. Data Extraction: Twenty specific data points were abstracted from each clinical trial under the broad categories of attributes of the patient and injury, treatment variables for the EMGB group, treatment variables for the control group, and attributes of the research design. Data Synthesis: Eight trials yielded a total of 319 participants with patellofemoral pain syndrome (n = 86), anterior cruciate ligament reconstruction (n = 52), arthroscopic surgery (n = 91), or osteoarthritis (n = 90). The average methodologic score of the included studies was 4.6/10 based on PEDro criteria. Pooled analyses demonstrated heterogeneity of the included studies, rendering the interpretation of the pooled data inappropriate. The EMGB appeared to benefit short-term postsurgical pain or quadriceps strength in 3 of 4 postsurgical investigations but was ineffective for chronic knee conditions such as patellofemoral pain and osteoarthritis in all 4 studies. Because the findings are based on limited

[Amino acid composition of the rat quadriceps femoris muscle after a flight on the Kosmos-936 biosatellite].

PubMed

Vlasova, T F; Miroshnikova, E B; Poliakov, V V; Murugova, T P

1982-01-01

The amino acid composition of the quadriceps muscle of rats flown onboard the biosatellite Cosmos-936 and exposed to the ground-based synchronous control experiment was studied. The weightless rats showed changes in the amino acid concentration in the quadriceps muscle. The centrifuged flight and synchronous rats displayed an accumulation of free amino acids in the above muscle.

The relationship between quadriceps muscle force, knee flexion, and anterior cruciate ligament strain in an in vitro simulated jump landing.

PubMed

Withrow, Thomas J; Huston, Laura J; Wojtys, Edward M; Ashton-Miller, James A

2006-02-01

An instrumented cadaveric knee construct was used to quantify the association between impact force, quadriceps force, knee flexion angle, and anterior cruciate ligament relative strain in simulated unipedal jump landings. Anterior cruciate ligament strain will correlate with impact force, quadriceps force, and knee flexion angle. Descriptive laboratory study. Eleven cadaveric knees (age, 70.8 [19.3] years; 5 male; 6 female) were mounted in a custom fixture with the tibia and femur secured to a triaxial load cell. Quadriceps, hamstring, and gastrocnemius muscle forces were simulated using pretensioned steel cables (stiffness, 7 kN/cm), and the quadriceps tendon force was measured using a load cell. Mean strain on the anteromedial bundle of the anterior cruciate ligament was measured using a DVRT. With the knee in 25 degrees of flexion, the construct was vertically loaded by an impact force initially directed 4 cm posterior to the knee joint center. Tibiofemoral kinematics was measured using a 3D optoelectronic tracking system. The increase in anterior cruciate ligament relative strain was proportional to the increase in quadriceps force (r(2) = 0.74; P < .00001) and knee flexion angle (r(2) = 0.88; P < .00001) but was not correlated with the impact force (r(2) = 0.009; P = .08). The increase in knee flexion and quadriceps force during this simulated 1-footed landing strongly influenced the relative strain on the anteromedial bundle of the anterior cruciate ligament. These results suggest that even in the presence of knee flexor muscle forces, the increase in quadriceps force required to prevent the knee from flexing during landing can place the anterior cruciate ligament at risk for large strains.

Effects of Short-Term Isokinetic Training on Standing Long-Jump Performance in Untrained Men.

ERIC Educational Resources Information Center

Morriss, Calvin J.; Tolfrey, Keith; Coppack, Russell J.

2001-01-01

Evaluated the effects of a brief isokinetic training program on quadriceps and hamstring peak torque (PT) and standing long-jump performance. Tests on 12 untrained men indicated that the brief training program was at least as effective in improving quadriceps isokinetic (but not hamstring) PT. PT gains subsequent to isokinetic resistance training…

Get up and Stretch

ERIC Educational Resources Information Center

Crupi, Jeffrey

2004-01-01

Daily stretching has many benefits for one's body. It can relieve stress and tension, it increases flexibility and it can help prevent injuries. There are many stretching exercises that a teacher can do with his or her students to help promote daily stretching routines. In this article, the author presents several stretching exercises and some…

[Simultaneous Traumatic Rupture of Patellar Ligament and Contralateral Rupture of Quadriceps Femoris Muscle].

PubMed

Hladký, V; Havlas, V

2017-01-01

Our paper presents a unique case of a 64-year-old patient after a fall, treated with oral antidiabetic drugs for type II diabetes mellitus. Following a series of examinations, a bilateral injury was diagnosed - patellar ligament tear on the right side and rupture of quadriceps femoris muscle on the left side. It is a rare injury, complicated by simultaneous involvement of both knee joints. The used therapy consisted of a bilateral surgery followed by gradual verticalisation, first with the support of a walking frame and later with the use of forearm crutches. During the final examination, the patient demonstrated full flexion at both knees, while an extension deficit of approx. 5 degrees was still present on the left side. The right knee X-ray showed a proper position of the patella after the removal of temporary tension band wire. Although the clinical results of operative treatment of both the patellar ligament rupture and rupture of quadriceps femoris muscle are in most cases good, early operative treatment, proper technique and post-operative rehabilitation are a prerequisite for success. Key words: knee injuries, patellar ligament, quadriceps muscle, rupture.

The Time Course of Knee Swelling Post Total Knee Arthroplasty and Its Associations with Quadriceps Strength and Gait Speed.

PubMed

Pua, Yong-Hao

2015-07-01

This study examines the time course of knee swelling post total knee arthroplasty (TKA) and its associations with quadriceps strength and gait speed. Eighty-five patients with unilateral TKA participated. Preoperatively and on post-operative days (PODs) 1, 4, 14, and 90, knee swelling was measured using bioimpedance spectrometry. Preoperatively and on PODs 14 and 90, quadriceps strength was measured using isokinetic dynamometry while fast gait speed was measured using the timed 10-meter walk. On POD1, knee swelling increased ~35% from preoperative levels after which, knee swelling reduced but remained at ~11% above preoperative levels on POD90. In longitudinal, multivariable analyses, knee swelling was associated with quadriceps weakness (P<0.01) and slower gait speed (P=0.03). Interventions to reduce post-TKA knee swelling may be indicated to improve quadriceps strength and gait speed. Copyright © 2015 Elsevier Inc. All rights reserved.

The effects of passive stretching plus vibration on strength and activation of the plantar flexors.

PubMed

Miller, Jonathan D; Herda, Trent J; Trevino, Michael A; Mosier, Eric M

2016-09-01

This study examined the effects of passive stretching only (PS+CON) and passive stretching with the addition of continuous vibration (VIB) during post-passive stretching tests (PS+VIB) on peak torque (PT), percent voluntary inactivation (%VI), single stimulus twitch torque (TTSINGLE), and doublet stimuli twitch torque (TTDOUBLET) of the plantar flexors at a short (20° plantar flexion (PF)) and long muscle length (15° dorsiflexion (DF)). Fourteen healthy men (age = 22 ± 3 years) performed isometric maximal voluntary contractions at PF and DF, and passive range of motion (PROM) assessments before and after 8 × 30-s passive stretches without (PS+CON) or with VIB (PS+VIB) administered continuously throughout post-passive stretching tests. The passive properties of the muscle tendon unit were assessed pre- and post-passive stretching via PROM, passive torque (PASSTQ), and musculotendinous stiffness (MTS) measurements. PT, TTSINGLE, and TTDOUBLET decreased, whereas, %VI increased following passive stretching at PF and DF (P < 0.05) with no significant differences between PS+CON and PS+VIB. PASSTQ and MTS decreased while PROM increased post-passive stretching during both trials (P < 0.05). The stretching-induced force/torque deficit and increases in %VI were evident following passive stretching at short and long muscle lengths. Although not statistically significant, effect size calculations suggested large and moderate differences in the absolute changes in PT (Cohen's d = 1.14) and %VI (Cohen's d = 0.54) from pre- to post-passive stretching between treatments, with PS+VIB having greater decreases of PT and higher %VI than PS+CON. The decrement in PT following passive stretching may be primarily neural in origin.

Repair of insertional achilles tendinosis with a bone-quadriceps tendon graft.

PubMed

Philippot, Rémi; Wegrzyn, Julien; Grosclaude, Sophie; Besse, Jean Luc

2010-09-01

While conservative treatment may be successful in most cases, partial rupture at the calcaneal insertion point is a significant concern with insertional Achilles tendinopathy. We report on the outcomes of a surgical technique for Achilles tendon augmentation using a bone-tendon graft harvested from the knee extensor system. Our retrospective case series includes 25 surgical procedures performed in 24 patients, 19 males and five females, with a mean age of 47 (range, 30 to 59) years, 18 of whom were athletes. The mean followup period was 52 (range, 12 to 156) months. All patients underwent MRI examination prior to surgery which showed partial Achilles tendon rupture. The Achilles tendon was debrided through a posterolateral approach. The bone-quadriceps tendon graft was harvested, then the bone plug of the graft was inserted into a blind tunnel drilled into the calcaneus and fixed with an interference screw. The fibers of the quadriceps tendon were sutured to the residual part of the Achilles tendon with the foot at an angle of 90 degrees. Patients were able to resume their sporting activity after an average of 6.7 months. At last followup examination, physical activity was scored 5.2 on the 10-point Tegner Scale; the mean AOFAS score was 98.4. MRI examination showed good graft integration 1 year postoperatively. The bone-quadriceps tendon grafting technique was a good alternative for the insertional Achilles lesions with partial detachment which we felt required augmentation.

Effect of a lateral step-up exercise protocol on quadriceps and lower extremity performance.

PubMed

Worrell, T W; Borchert, B; Erner, K; Fritz, J; Leerar, P

1993-12-01

Closed kinetic chain exercises have been promoted as more functional and more appropriate than open kinetic chain exercises. Limited research exists demonstrating the effect of closed kinetic chain exercise on quadriceps and lower extremity performance. The purpose of this study was to determine the effect of a lateral step-up exercise protocol on isokinetic quadriceps peak torque and the following lower extremity activities: 1) leg press, 2) maximal step-up repetitions with body weight plus 25%, 3) hop for distance, and 4) 6-m timed hop. Twenty subjects participated in a 4-week training period, and 18 subjects served as controls. For the experimental group, a repeated measure ANOVA comparing pretest and posttest values revealed significant improvements in the leg press (p < or = .05), step-ups (p < or = .05), hop for distance (p < or = .05), and hop for time (p < or = .05) and no significant increase in isokinetic quadriceps peak torque (p > or = .05). Over the course of the training period, weight used for the step-up exercise increased (p < or = .05), repetitions decreased (p < or = .05), and step-up work did not change (p > or = .05). For the control group, no significant change (p > or = .05) occurred in any variable. The inability of the isokinetic dynamometer to detect increases in quadriceps performance is important because the isokinetic values are frequently used as criteria for return to functional activities. We conclude that closed kinetic chain testing and exercise provide additional means to assess and rehabilitate the lower extremity.

Dynamic stretching and golf swing performance.

PubMed

Moran, K A; McGrath, T; Marshall, B M; Wallace, E S

2009-02-01

The aim of the present study was to examine the effect of dynamic stretching, static stretching and no stretching, as part of a general warm-up, on golf swing performance with a five-iron. Measures of performance were taken 0 min, 5 min, 15 min and 30 min after stretching. Dynamic stretching produced significantly greater club head speeds than both static stretching (Delta=1.9m.s (-1); p=0.000) and no stretching (Delta=1.7 m.s (-1); p=0.000), and greater ball speeds than both static stretching (Delta=3.5m.s (-1); p=0.003) and no stretching (Delta=3.3m.s (-1); p=0.001). Dynamic stretching produced significantly straighter swing-paths than both static stretching (Delta=-0.61 degrees , p=0.000) and no stretching (Delta=-0.72 degrees , p=0.01). Dynamic stretching also produced more central impact points than the static stretch (Delta=0.7 cm, p=0.001). For the club face angle, there was no effect of either stretch or time. For all of the variables measured, there was no significant difference between the static stretch and no stretch conditions. All of the results were unaffected by the time of measurement after stretching. The results indicate that dynamic stretching should be used as part of a general warm-up in golf.

Short-latency primate vestibuloocular responses during translation

NASA Technical Reports Server (NTRS)

Angelaki, D. E.; McHenry, M. Q.

1999-01-01

Short-lasting, transient head displacements and near target fixation were used to measure the latency and early response gain of vestibularly evoked eye movements during lateral and fore-aft translations in rhesus monkeys. The latency of the horizontal eye movements elicited during lateral motion was 11.9 +/- 5.4 ms. Viewing distance-dependent behavior was seen as early as the beginning of the response profile. For fore-aft motion, latencies were different for forward and backward displacements. Latency averaged 7.1 +/- 9.3 ms during forward motion (same for both eyes) and 12.5 +/- 6.3 ms for the adducting eye (e.g., left eye during right fixation) during backward motion. Latencies during backward motion were significantly longer for the abducting eye (18.9 +/- 9.8 ms). Initial acceleration gains of the two eyes were generally larger than unity but asymmetric. Specifically, gains were consistently larger for abducting than adducting eye movements. The large initial acceleration gains tended to compensate for the response latencies such that the early eye movement response approached, albeit consistently incompletely, that required for maintaining visual acuity during the movement. These short-latency vestibuloocular responses could complement the visually generated optic flow responses that have been shown to exhibit much longer latencies.

Stretching Safely and Effectively

MedlinePlus

... shown that stretching immediately before an event weakens hamstring strength. Instead of static stretching, try performing a " ... If you play soccer, for instance, stretch your hamstrings as you're more vulnerable to hamstring strains. ...

Vortex stretching in self-gravitating protoplanetary discs

NASA Astrophysics Data System (ADS)

Regály, Zs.; Vorobyov, E.

2017-10-01

Horseshoe-shaped brightness asymmetries of several transitional discs are thought to be caused by large-scale vortices. Anticyclonic vortices efficiently collect dust particles, therefore they can play a major role in planet formation. Former studies suggest that the disc self-gravity weakens vortices formed at the edge of the gap opened by a massive planet in discs whose masses are in the range of 0.01 ≤ Mdisc/M* ≤ 0.1. Here, we present an investigation on the long-term evolution of the large-scale vortices formed at the viscosity transition of the discs' dead zone outer edge by means of two-dimensional hydrodynamic simulations taking disc self-gravity into account. We perform a numerical study of low-mass, 0.001 ≤ Mdisc/M* ≤ 0.01, discs, for which cases disc self-gravity was previously neglected. The large-scale vortices are found to be stretched due to disc self-gravity even for low-mass discs with Mdisc/M* ≳ 0.005, where initially the Toomre Q-parameter was ≲ 50 at the vortex distance. As a result of stretching, the vortex aspect ratio increases and a weaker azimuthal density contrast develops. The strength of the vortex stretching is proportional to the disc mass. The vortex stretching can be explained by a combined action of a non-vanishing gravitational torque caused by the vortex and the Keplerian shear of the disc. Self-gravitating vortices are subject to significantly faster decay than non-self-gravitating ones. We found that vortices developed at sharp viscosity transitions of self-gravitating discs can be described by a Goodman - Narayan - Goldreich (GNG) model as long as the disc viscosity is low, I.e. αdz ≤ 10-5.

Quadriceps strengthening with and without blood flow restriction in the treatment of patellofemoral pain: a double-blind randomised trial.

PubMed

Giles, Lachlan; Webster, Kate E; McClelland, Jodie; Cook, Jill L

2017-12-01

Quadriceps strengthening exercises are part of the treatment of patellofemoral pain (PFP), but the heavy resistance exercises may aggravate knee pain. Blood flow restriction (BFR) training may provide a low-load quadriceps strengthening method to treat PFP. Seventy-nine participants were randomly allocated to a standardised quadriceps strengthening (standard) or low-load BFR. Both groups performed 8 weeks of leg press and leg extension, the standard group at 70% of 1 repetition maximum (1RM) and the BFR group at 30% of 1RM. Interventions were compared using repeated-measures analysis of variance for Kujala Patellofemoral Score, Visual Analogue Scale for 'worst pain' and 'pain with daily activity', isometric knee extensor torque (Newton metre) and quadriceps muscle thickness (cm). Subgroup analyses were performed on those participants with painful resisted knee extension at 60°. Sixty-nine participants (87%) completed the study (standard, n=34; BFR, n=35). The BFR group had a 93% greater reduction in pain with activities of daily living (p=0.02) than the standard group. Participants with painful resisted knee extension (n=39) had greater increases in knee extensor torque with BFR than standard (p<0.01). No between-group differences were found for change in Kujala Patellofemoral Score (p=0.31), worst pain (p=0.24), knee extensor torque (p=0.07) or quadriceps thickness (p=0.2). No difference was found between interventions at 6 months. Compared with standard quadriceps strengthening, low load with BFR produced greater reduction in pain with daily living at 8 weeks in people with PFP. Improvements were similar between groups in worst pain and Kujala score. The subgroup with painful resisted knee extension had larger improvements in quadriceps strength from BFR. 12614001164684. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Advanced LIGO low-latency searches

NASA Astrophysics Data System (ADS)

Kanner, Jonah; LIGO Scientific Collaboration, Virgo Collaboration

2016-06-01

Advanced LIGO recently made the first detection of gravitational waves from merging binary black holes. The signal was first identified by a low-latency analysis, which identifies gravitational-wave transients within a few minutes of data collection. More generally, Advanced LIGO transients are sought with a suite of automated tools, which collectively identify events, evaluate statistical significance, estimate source position, and attempt to characterize source properties. This low-latency effort is enabling a broad multi-messenger approach to the science of compact object mergers and other transients. This talk will give an overview of the low-latency methodology and recent results.

Quadriceps muscle function after exercise in men and women with a history of anterior cruciate ligament reconstruction.

PubMed

Kuenze, Christopher M; Hertel, Jay; Hart, Joseph M

2014-01-01

Sex differences in lower extremity neuromuscular function have been reported after anterior cruciate ligament reconstruction (ACLR). Research evidence supports different levels of fatigability in men and women and between patients with ACLR and healthy controls. The influence of sex on the response to continuous exercise in patients with ACLR is not clear. To compare quadriceps neuromuscular function after exercise between men and women with ACLR. Descriptive laboratory study. Laboratory. Twenty-six active volunteers (13 men [50%]: age = 24.1 ± 4.4 years, height = 179.1 ± 9.8 cm, mass = 80.1 ± 9.4 kg, months since surgery = 43.5 ± 37.0; 13 women [50%]: age = 24.2 ± 5.6 years, height = 163.0 ± 5.9 cm, mass = 62.3 ± 8.3 kg, months since surgery = 45.8 ± 42.7) with a history of unilateral primary ACLR at least 6 months earlier. Thirty minutes of continuous exercise comprising 5 separate 6-minute cycles, including 5 minutes of uphill walking and 1 minute of body-weight squatting and step-ups. Normalized knee-extension maximal voluntary isometric contraction torque, quadriceps superimposed-burst torque, and quadriceps central activation ratio before and after exercise. We performed separate 2 (sex: men, women) × 2 (time: preexercise, postexercise) repeated-measures analyses of variance for the 3 variables. Separate, independent-samples t tests were calculated to compare preexercise with postexercise change in all dependent variables between sexes. A significant group-by-time interaction was present for knee-extension torque (P = .04). The percentage reduction in knee-extension maximal voluntary isometric contraction torque (men = 1.94%, women = -10.32%; P = .02) and quadriceps central activation ratio (men = -1.45%, women = -8.69%; P = .03) experienced by men was less than that observed in women. In the presence of quadriceps dysfunction, female participants experienced greater-magnitude reductions in quadriceps function after 30 minutes of exercise than male

A mathematical model of forces in the knee under isometric quadriceps contractions.

PubMed

Huss, R A; Holstein, H; O'Connor, J J

2000-02-01

To predict the knee's response to isometric quadriceps contractions against a fixed tibial restraint.Design. Mathematical modelling of the human knee joint. Isometric quadriceps contraction is commonly used for leg muscle strengthening following ligament injury or reconstruction. It is desirable to know the ligament forces induced but direct measurement is difficult. The model, previously applied to the Lachmann or 'drawer' tests, combines an extensible fibre-array representation of the cruciate ligaments with a compressible 'thin-layer' representation of the cartilage. The model allows the knee configuration and force system to be calculated, given flexion angle, restraint position and loading. Inclusion of cartilage deformation increases relative tibio-femoral translation and decreases the ligament forces generated. For each restraint position, a range of flexion angles is found in which no ligament force is required, as opposed to a single flexion angle in the case of incompressible cartilage layers. Knee geometry and ligament elasticity are found to be the most important factors governing the joint's response to isometric quadriceps contractions, but cartilage deformation is found to be more important than in the Lachmann test. Estimation of knee ligament forces is important when devising exercise regimes following ligament injury or reconstruction. The finding of a 'neutral zone' of zero ligament force may have implications for rehabilitation of the ligament-injured knee.

Perceived ejaculatory latency and pleasure in different outlets.

PubMed

Corty, Eric W

2008-11-01

Ejaculatory latencies have been studied in coitus and with masturbation, but not with oral or manual stimulation by a partner. The present study extended research on ejaculatory latency to these outlets, and investigated the effect of perceived pleasure on self-reported ejaculatory latency. A convenience sample of male college students, not selected for sexual dysfunction, completed questionnaires assessing the outcome measures. Self-report measures of latency to ejaculation in, and perceived pleasure associated with, four different outlets (vaginal intercourse, oral intercourse, manual stimulation by a partner, and masturbation). Ejaculatory latencies in partnered activities were predictive of each other. Masturbatory latencies were predictive of coital latencies but not oral or manual stimulation latencies; all the partnered activities were predictive of each other. There was no difference in time to ejaculation among any of the partnered outlets, although ejaculation occurred more quickly with masturbation than with coitus or manual stimulation. In terms of pleasure associated with the outlets, vaginal and oral intercourse were perceived as equally pleasurable, and both were rated as more pleasurable than manual stimulation or masturbation, which did not differ from each other. These results suggest that rapidity of ejaculation is consistent across outlets for the partnered sexual activities, and that there is little unique-in terms of ejaculatory latency--about vaginal intercourse compared with oral or manual stimulation by a partner. Masturbation, however, does differ from the partnered activities. Although the average correlation, for individuals, between latency and pleasure for the different outlets is near zero, there are subgroups of men who have (i) a negative relation, (ii) a positive relation, or (iii) no relation. Results show that men, for whom greater pleasure is associated with shorter latency, are more likely to be dissatisfied with their

Validity and reliability of isometric, isokinetic and isoinertial modalities for the assessment of quadriceps muscle strength in patients with total knee arthroplasty.

PubMed

Lienhard, K; Lauermann, S P; Schneider, D; Item-Glatthorn, J F; Casartelli, N C; Maffiuletti, N A

2013-12-01

Reliability of isometric, isokinetic and isoinertial modalities for quadriceps strength evaluation, and the relation between quadriceps strength and physical function was investigated in 29 total knee arthroplasty (TKA) patients, with an average age of 63 years. Isometric maximal voluntary contraction torque, isokinetic peak torque, and isoinertial one-repetition maximum load of the involved and uninvolved quadriceps were evaluated as well as objective (walking parameters) and subjective physical function (WOMAC). Reliability was good and comparable for the isometric, isokinetic, and isoinertial strength outcomes on both sides (intraclass correlation coefficient range: 0.947-0.966; standard error of measurement range: 5.1-9.3%). Involved quadriceps strength was significantly correlated to walking speed (r range: 0.641-0.710), step length (r range: 0.685-0.820) and WOMAC function (r range: 0.575-0.663), independent from the modality (P < 0.05). Uninvolved quadriceps strength was also significantly correlated to walking speed (r range: 0.413-0.539), step length (r range: 0.514-0.608) and WOMAC function (r range: 0.374-0.554) (P < 0.05), except for WOMAC function/isokinetic peak torque (P > 0.05). In conclusion, isometric, isokinetic, and isoinertial modalities ensure valid and reliable assessment of quadriceps muscle strength in TKA patients. Copyright © 2013 Elsevier Ltd. All rights reserved.

Pain level after ACL reconstruction: A comparative study between free quadriceps tendon and hamstring tendons autografts.

PubMed

Buescu, Cristian Tudor; Onutu, Adela Hilda; Lucaciu, Dan Osvald; Todor, Adrian

2017-03-01

The objective of this study was to compare the pain levels and analgesic consumption after single bundle ACL reconstruction with free quadriceps tendon autograft versus hamstring tendon autograft. A total of 48 patients scheduled for anatomic single-bundle ACL reconstruction were randomized into two groups: the free quadriceps tendon autograft group (24 patients) and the hamstring tendons autograft group (24 patients). A basic multimodal analgesic postoperative program was used for all patients and rescue analgesia was provided with tramadol, at pain scores over 30 on the Visual Analog Scale. The time to the first rescue analgesic, the number of doses of tramadol and pain scores were recorded. The results within the same group were compared with the Wilcoxon signed test. Supplementary analgesic drug administration proved significantly higher in the group of subjects with hamstring grafts, with a median (interquartile range) of 1 (1.3) dose, compared to the group of subjects treated with a quadriceps graft, median = 0.5 (0.1.25) (p = 0.009). A significantly higher number of subjects with a quadriceps graft did not require any supplementary analgesic drug (50%) as compared with subjects with hamstring graft (13%; Z-statistics = 3.01, p = 0.002). The percentage of subjects who required a supplementary analgesic drug was 38% higher in the HT group compared with the FQT group. The use of the free quadriceps tendon autograft for ACL reconstruction leads to less pain and analgesic consumption in the immediate postoperative period compared with the use of hamstrings autograft. Level I Therapeutic study. Copyright © 2017 Turkish Association of Orthopaedics and Traumatology. Production and hosting by Elsevier B.V. All rights reserved.

Handling qualities effects of display latency

NASA Technical Reports Server (NTRS)

King, David W.

1993-01-01

Display latency is the time delay between aircraft response and the corresponding response of the cockpit displays. Currently, there is no explicit specification for allowable display lags to ensure acceptable aircraft handling qualities in instrument flight conditions. This paper examines the handling qualities effects of display latency between 70 and 400 milliseconds for precision instrument flight tasks of the V-22 Tiltrotor aircraft. Display delay effects on the pilot control loop are analytically predicted through a second order pilot crossover model of the V-22 lateral axis, and handling qualities trends are evaluated through a series of fixed-base piloted simulation tests. The results show that the effects of display latency for flight path tracking tasks are driven by the stability characteristics of the attitude control loop. The data indicate that the loss of control damping due to latency can be simply predicted from knowledge of the aircraft's stability margins, control system lags, and required control bandwidths. Based on the relationship between attitude control damping and handling qualities ratings, latency design guidelines are presented. In addition, this paper presents a design philosophy, supported by simulation data, for using flight director display augmentation to suppress the effects of display latency for delays up to 300 milliseconds.

Associations Among Quadriceps Strength and Rate of Torque Development 6 Weeks Post Anterior Cruciate Ligament Reconstruction and Future Hop and Vertical Jump Performance: A Prospective Cohort Study.

PubMed

Pua, Yong-Hao; Mentiplay, Benjamin F; Clark, Ross A; Ho, Jia-Ying

2017-11-01

Study Design Prospective cohort. Background Quadriceps strength is associated with hop distance and jump height in persons who have undergone anterior cruciate ligament (ACL) reconstruction. However, it is unknown whether the ability to rapidly generate quadriceps torque in the early phase of recovery is associated with future hopping and jumping performance in this population. Objective To evaluate the prospective associations among quadriceps strength and rate of torque development (RTD) and single-leg hop for distance, vertical jump height, vertical ground reaction force (vGRF), and vertical force loading rate during a landing task in persons who have undergone ACL reconstruction. Methods Seventy patients with unilateral ACL reconstruction participated. At 6 weeks post ACL reconstruction, isometric quadriceps strength and RTD were measured using a dynamometer. At 6 months following ACL reconstruction, patients performed the single-leg hop for distance test. Patients also performed the single-leg vertical jump test on a force plate that measured maximum jump height, vGRF, and average loading rate during landing. Results Both quadriceps strength and RTD at 6 weeks post ACL reconstruction were associated with all hopping and jumping measures at 6 months post ACL reconstruction (P≤.04). Single-leg hop distance was associated more closely with quadriceps strength than with quadriceps RTD (P = .05), and vertical jump height and vGRF measures were associated more closely with quadriceps RTD than with quadriceps strength (P = .05 and P<.01, respectively). Both quadriceps measures were associated with loading rate. Conclusion Quadriceps strength and RTD are complementary but distinct predictors of future hopping and jumping performance in persons who have undergone ACL reconstruction. These findings may contribute to improved rehabilitation of patients who are at risk for poor jumping/hopping performance and abnormal knee loading. J Orthop Sports Phys Ther 2017

HIV-1 Latency: An Update of Molecular Mechanisms and Therapeutic Strategies

PubMed Central

Battistini, Angela; Sgarbanti, Marco

2014-01-01

The major obstacle towards HIV-1 eradication is the life-long persistence of the virus in reservoirs of latently infected cells. In these cells the proviral DNA is integrated in the host’s genome but it does not actively replicate, becoming invisible to the host immune system and unaffected by existing antiviral drugs. Rebound of viremia and recovery of systemic infection that follows interruption of therapy, necessitates life-long treatments with problems of compliance, toxicity, and untenable costs, especially in developing countries where the infection hits worst. Extensive research efforts have led to the proposal and preliminary testing of several anti-latency compounds, however, overall, eradication strategies have had, so far, limited clinical success while posing several risks for patients. This review will briefly summarize the more recent advances in the elucidation of mechanisms that regulates the establishment/maintenance of latency and therapeutic strategies currently under evaluation in order to eradicate HIV persistence. PMID:24736215

Stretch-Oriented Polyimide Films

NASA Technical Reports Server (NTRS)

Hinkley, Jeffrey A.; Klinedinst, D.; Feuz, L.

2000-01-01

Two thermoplastic polyimides - one amorphous, the other crystallizable -- were subjected to isothermal stretching just above their glass transition temperatures. Room-temperature strengths in the stretch direction were greatly improved and, moduli increased up to 3.6-fold. Optimum stretching conditions were determined.

Does long-term passive stretching alter muscle-tendon unit mechanics in children with spastic cerebral palsy?

PubMed

Theis, Nicola; Korff, Thomas; Mohagheghi, Amir A

2015-12-01

Cerebral palsy causes motor impairments during development and many children may experience excessive neural and mechanical muscle stiffness. The clinical assumption is that excessive stiffness is thought to be one of the main reasons for functional impairments in cerebral palsy. As such, passive stretching is widely used to reduce stiffness, with a view to improving function. However, current research evidence on passive stretching in cerebral palsy is not adequate to support or refute the effectiveness of stretching as a management strategy to reduce stiffness and/or improve function. The purpose was to identify the effect of six weeks passive ankle stretching on muscle-tendon unit parameters in children with spastic cerebral palsy. Thirteen children (8-14 y) with quadriplegic/diplegic cerebral palsy were randomly assigned to either an experimental group (n=7) or a control group (n=6). The experimental group underwent an additional six weeks of passive ankle dorsiflexion stretching for 15 min (per leg), four days per week, whilst the control group continued with their normal routine, which was similar for the two groups. Measures of muscle and tendon stiffness, strain and resting length were acquired pre- and post-intervention. The experimental group demonstrated a 3° increase in maximum ankle dorsiflexion. This was accompanied by a 13% reduction in triceps surae muscle stiffness, with no change in tendon stiffness. Additionally, there was an increase in fascicle strain with no changes in resting length, suggesting muscle stiffness reductions were a result of alterations in intra/extra-muscular connective tissue. The results demonstrate that stretching can reduce muscle stiffness by altering fascicle strain but not resting fascicle length. Copyright © 2015 Elsevier Ltd. All rights reserved.

Manual therapy directed at the knee or lumbopelvic region does not influence quadriceps spinal reflex excitability.

PubMed

Grindstaff, Terry L; Pietrosimone, Brian G; Sauer, Lindsay D; Kerrigan, D Casey; Patrie, James T; Hertel, Jay; Ingersoll, Christopher D

2014-08-01

Manual therapies, directed to the knee and lumbopelvic region, have demonstrated the ability to improve neuromuscular quadriceps function in individuals with knee pathology. It remains unknown if manual therapies may alter impaired spinal reflex excitability, thus identifying a potential mechanism in which manual therapy may improve neuromuscular function following knee injury. To determine the effect of local and distant mobilisation/manipulation interventions on quadriceps spinal reflex excitability. Seventy-five individuals with a history of knee joint injury and current quadriceps inhibition volunteered for this study. Participants were randomised to one of five intervention groups: lumbopelvic manipulation (grade V), lumbopelvic manipulation positioning (no thrust), grade IV patellar mobilisation, grade I patellar mobilisation, and control (no treatment). Changes in spinal reflex excitability were quantified by assessing the Hoffmann reflex (H-reflex), presynaptic, and postsynaptic excitability. A hierarchical linear-mixed model for repeated measures was performed to compare changes in outcome variables between groups over time (pre, post 0, 30, 60, 90 min). There were no significant differences in H-reflex, presynaptic, or postsynaptic excitability between groups across time. Manual therapies directed to the knee or lumbopelvic region did not acutely change quadriceps spinal reflex excitability. Although manual therapies may improve impairments and functional outcomes the underlying mechanism does not appear to be related to changes in spinal reflex excitability. Copyright © 2014 Elsevier Ltd. All rights reserved.

High-resolution FISH on super-stretched flow-sorted plant chromosomes.

PubMed

Valárik, M; Bartos, J; Kovárová, P; Kubaláková, M; de Jong, J H; Dolezel, J

2004-03-01

A novel high-resolution fluorescence in situ hybridisation (FISH) strategy, using super-stretched flow-sorted plant chromosomes as targets, is described. The technique that allows longitudinal extension of chromosomes of more than 100 times their original metaphase size is especially attractive for plant species with large chromosomes, whose pachytene chromosomes are generally too long and heterochromatin patterns too complex for FISH analysis. The protocol involves flow cytometric sorting of metaphase chromosomes, mild proteinase-K digestion of air-dried chromosomes on microscopic slides, followed by stretching with ethanol:acetic acid (3 : 1). Stretching ratios were assessed in a number of FISH experiments with super-stretched chromosomes from barley, wheat, rye and chickpea, hybridised with 45S and 5S ribosomal DNAs and the [GAA]n microsatellite, the [TTTAGGG]n telomeric repeat and a bacterial artificial chromosome (BAC) clone as probes. FISH signals on stretched chromosomes were brighter than those on the untreated control, resulting from better accessibility of the stretched chromatin and maximum observed sensitivity of 1 kbp. Spatial resolution of neighbouring loci was improved down to 70 kbp as compared to 5-10 Mbp after FISH on mitotic chromosomes, revealing details of adjacent DNA sequences hitherto not obtained with any other method. Stretched chromosomes are advantageous over extended DNA fibres from interphase nuclei as targets for FISH studies because they still retain chromosomal integrity. Although the method is confined to species for which chromosome flow sorting has been developed, it provides a unique system for controlling stretching degree of mitotic chromosomes and high-resolution bar-code FISH.

Nandrolone decanoate and physical activity affect quadriceps in peripubertal rats.

PubMed

Sretenovic, Jasmina; Ajdzanovic, Vladimir; Zivkovic, Vladimir; Srejovic, Ivan; Corbic, Milena; Milosevic, Verica; Jakovljevic, Vladimir; Milosavljevic, Zoran

2018-07-01

Anabolic androgenic steroids (AASs) are synthetic analogs of testosterone often used by athletes to increase the skeletal muscle mass. Our goal was to examine the effects of physical activity and physical activity combined with supraphysiological doses of nandrolone on functional morphology of the quadriceps muscle. The study included 32 peripubertal Wistar rats, divided into 4 groups: control (T-N-), nandrolone (T-N+), physical activity (T+N-) and physical activity plus nandrolone (T+N+) groups. The T+N- and T+N+ group swam for 4 weeks, 1 h/day, 5 days/week. The T-N+ and T+N+ groups received nandolone decanoate (20 mg/kg b.w.) once per week, subcutaneously. Subsequently, the rats were sacrificed and muscle specimens were prepared for the processing. Tissue sections were histochemically and immunohistochemically stained, while the image analysis was used for quantification. Longitudinal diameter of quadriceps muscle cells was increased for 21% in T-N+, for 57% in T+N- and for 64% in T+N+ group while cross section muscle cell area was increased in T-N+ for 19%, in T+N- for 47% and in T+N+ group for 59%, compared to the control. Collagen fibers covered area was increased in T-N+ group for 36%, in T+N- for 109% and in T+N+ group for 159%, compared to the control. Erythrocyte depots were decreased in T-N+ group and increased in T+N- and T+N+ group, in comparison with T-N-. VEGF depots were increased in all treated groups. Chronic administration of supraphysiological doses of AASs alone or in combination with physical activity induces hypertrophy and significant changes in the quadriceps muscle tissue structure. Copyright © 2018 Elsevier GmbH. All rights reserved.

Communication latencies of wireless devices suitable for time-critical messaging to anesthesia providers.

PubMed

Epstein, Richard H; Dexter, Franklin; Rothman, Brian

2013-04-01

anesthesia communication systems need to measure latencies of proposed communication pathways and devices used to deliver urgent messages to mobile users. Similar evaluation is relevant for text pagers used on an ad hoc basis for delivery of time-critical notifications. Testing over a period of hours to days is adequate only for disqualification of a candidate paging system, because acceptable results are not necessarily indicative of long-term performance. Rather, weeks of testing are required, with appropriate batching of pages for analysis.

Signal, noise, and variation in neural and sensory-motor latency

PubMed Central

Lee, Joonyeol; Joshua, Mati; Medina, Javier F.; Lisberger, Stephen G.

2016-01-01

Analysis of the neural code for sensory-motor latency in smooth pursuit eye movements reveals general principles of neural variation and the specific origin of motor latency. The trial-by-trial variation in neural latency in MT comprises: a shared component expressed as neuron-neuron latency correlations; and an independent component that is local to each neuron. The independent component arises heavily from fluctuations in the underlying probability of spiking with an unexpectedly small contribution from the stochastic nature of spiking itself. The shared component causes the latency of single neuron responses in MT to be weakly predictive of the behavioral latency of pursuit. Neural latency deeper in the motor system is more strongly predictive of behavioral latency. A model reproduces both the variance of behavioral latency and the neuron-behavior latency correlations in MT if it includes realistic neural latency variation, neuron-neuron latency correlations in MT, and noisy gain control downstream from MT. PMID:26971946

Recovery of gait after quadriceps muscle fatigue.

PubMed

Barbieri, Fabio Augusto; Beretta, Stephannie Spiandor; Pereira, Vinicius A I; Simieli, Lucas; Orcioli-Silva, Diego; dos Santos, Paulo Cezar Rocha; van Dieën, Jaap H; Gobbi, Lilian Teresa Bucken

2016-01-01

The aim of this study was to investigate the effect of recovery time after quadriceps muscle fatigue on gait in young adults. Forty young adults (20-40 years old) performed three 8-m gait trials at preferred velocity before and after muscle fatigue, and after 5, 10 and 20min of passive rest. In addition, at each time point, two maximal isometric voluntary contractions were preformed. Muscle fatigue was induced by repeated sit-to-stand transfers until task failure. Spatio-temporal, kinetic and muscle activity parameters, measured in the central stride of each trial, were analyzed. Data were compared between before and after the muscle fatigue protocol and after the recovery periods by one-way repeated measures ANOVA. The voluntary force was decreased after the fatigue protocol (p<0.001) and after 5, 10 and 20min of recovery compared to before the fatigue protocol. Step width (p<0.001) and RMS of biceps femoris (p<0.05) were increased immediately after the fatigue protocol and remained increased after the recovery periods. In addition, stride duration was decreased immediately after the fatigue protocol compared to before and to after 10 and 20min of rest (p<0.001). The anterior-posterior propulsive impulse was also decreased after the fatigue protocol (p<0.001) and remained low after 5, 10 and 20min of rest. We conclude that 20min is not enough to see full recovery of gait after exhaustive quadriceps muscle fatigue. Copyright © 2015 Elsevier B.V. All rights reserved.

Latency causes and reduction in optical metro networks

NASA Astrophysics Data System (ADS)

Bobrovs, Vjaceslavs; Spolitis, Sandis; Ivanovs, Girts

2013-12-01

The dramatic growth of transmitted information in fiber optical networks is leading to a concern about the network latency for high-speed reliable services like financial transactions, telemedicine, virtual and augmented reality, surveillance, and other applications. In order to ensure effective latency engineering, the delay variability needs to be accurately monitored and measured, in order to control it. This paper in brief describes causes of latency in fiber optical metro networks. Several available latency reduction techniques and solutions are also discussed, namely concerning usage of different chromatic dispersion compensation methods, low-latency amplifiers, optical fibers as well as other network elements.

Rewards modulate saccade latency but not exogenous spatial attention.

PubMed

Dunne, Stephen; Ellison, Amanda; Smith, Daniel T

2015-01-01

The eye movement system is sensitive to reward. However, whilst the eye movement system is extremely flexible, the extent to which changes to oculomotor behavior induced by reward paradigms persist beyond the training period or transfer to other oculomotor tasks is unclear. To address these issues we examined the effects of presenting feedback that represented small monetary rewards to spatial locations on the latency of saccadic eye movements, the time-course of learning and extinction of the effects of rewarding saccades on exogenous spatial attention and oculomotor inhibition of return. Reward feedback produced a relative facilitation of saccadic latency in a stimulus driven saccade task which persisted for three blocks of extinction trials. However, this hemifield-specific effect failed to transfer to peripheral cueing tasks. We conclude that rewarding specific spatial locations is unlikely to induce long-term, systemic changes to the human oculomotor or attention systems.

Peroneus longus stretch reflex amplitude increases after ankle brace application

PubMed Central

Cordova, M; Ingersoll, C

2003-01-01

Background: The use of external ankle support is widespread throughout sports medicine. However, the application of ankle bracing to a healthy ankle over a long period has been scrutinised because of possible neuromuscular adaptations resulting in diminished dynamic support offered by the peroneus longus. Objective: To investigate the immediate and chronic effects of ankle brace application on the amplitude of peroneus longus stretch reflex. Methods: Twenty physically active college students (mean (SD) age 23.6 (1.7) years, height 168.7 (8.4) cm, and mass 69.9 (12.0) kg) who had been free from lower extremity pathology for the 12 months preceding the study served as subjects. None had been involved in a strength training or conditioning programme in the six months preceding the study. A 3 x 3 x 2 (test condition x treatment condition x time) design with repeated measures on the first and third factor was used. The peroneus longus stretch reflex (% of maximum amplitude) during sudden foot inversion was evaluated under three ankle brace conditions (control, lace up, and semi-rigid) before and after eight weeks of ankle brace use. Results: A 3 x 3 x 2 repeated measures analysis of variance showed that peroneus longus stretch reflex amplitude increased immediately after application of a lace up brace (67.1 (4.4)) compared with the semi-rigid (57.9 (4.3)) and control (59.0 (5.2)) conditions (p<0.05). Peroneus longus stretch reflex also increased after eight weeks of use of the semi-rigid brace compared with the lace up and control conditions (p<0.05). Conclusions: Initial application of a lace up style ankle brace and chronic use of a semi-rigid brace facilitates the amplitude of the peroneus longus stretch reflex. It appears that initial and long term ankle brace use does not diminish the magnitude of this stretch reflex in the healthy ankle. PMID:12782553

Influence of the stretch wrapping process on the mechanical behavior of a stretch film

NASA Astrophysics Data System (ADS)

Klein, Daniel; Stommel, Markus; Zimmer, Johannes

2018-05-01

Lightweight construction is an ongoing task in packaging development. Consequently, the stability of packages during transport is gaining importance. This study contributes to the optimization of lightweight packaging concepts regarding their stability. A very widespread packaging concept is the distribution of goods on a pallet whereas a Polyethylene (PE) stretch film stabilizes the lightweight structure during the shipment. Usually, a stretch wrapping machine applies this stretch film to the pallet. The objective of this study is to support packaging development with a method that predicts the result of the wrapping process, based on the mechanical characterization of the stretch film. This result is not only defined by the amount of stretch film, its spatial distribution on the pallet and its internal stresses that result in a containment force. More accurate, this contribution also considers the influence of the deformation history of the stretch film during the wrapping process. By focusing on similarities of stretch wrappers rather than on differences, the influence of generalized process parameters on stretch film mechanics and thereby on pallet stability can be determined experimentally. For a practical use, the predictive method is accumulated in an analytic model of the wrapping process that can be verified experimentally. This paves the way for experimental and numerical approaches regarding the optimization of pallet stability.

Dual binding mode in cohesin-dockerin complexes as assessed through stretching studies

NASA Astrophysics Data System (ADS)

Wojciechowski, Michał; Cieplak, Marek

2016-10-01

A recent experimental study by Jobst et al. of stretching of a wild-type (WT) cohesin-dockerin complex has identified two kinds of the force-displacement patterns, with a single or double-peaked final rupture, which are termed "short" and "long" here. This duality has been interpreted as arising from the existence of two kinds of binding. Here, we analyze the separation of two cohesin-dockerin complexes of C. thermocellum theoretically. We use a coarse-grained structure-based model and the values of the pulling speeds are nearly experimental. In their native states, the two systems differ in the mutual binding orientations of the molecules in the complex. We demonstrate that the WT complex (PDB:1OHZ) unravels along two possible pathways that are qualitatively consistent with the presence of the short and long patterns observed experimentally. On the other hand, the mutated complex (PDB:2CCL) leads only to short trajectories. The short and long stretching pathways also appear in the cohesin-dockerin-Xmodule complex (PDB:4IU3, WT) of R. flavefaciens. Thus the duality in the stretching patterns need not be necessarily due to the duality in binding.

Stretch-induced contraction in pulmonary arteries.

PubMed

Kulik, T J; Evans, J N; Gamble, W J

1988-12-01

Stretch stimulates contraction of systemic blood vessels, but the response has not been described in pulmonary vessels. To determine whether pulmonary arteries contract when stretched, isolated cylindrical segments of pulmonary arteries were suspended between two parallel wires, stretched, and the active force was generated in response to stretch measured. Eighty-nine percent of segments from small (in situ diameter less than 1,000 microns) feline pulmonary arteries contracted when stretched, and in 65% of these the magnitude of stretch was related to the magnitude of contraction. Large (in situ diameter greater than or equal to 1,000 microns) feline pulmonary arteries did not contract with stretch. Multiple, rapidly repeated stretches resulted in a diminution of active force development. Stretch-induced contraction required external Ca2+ and was abolished by diltiazem (10 microns), but it was not affected by phenoxybenzamine, phentolamine, diethylcarbamazine, or mechanical removal of endothelium. Indomethacin blunted but did not abolish stretch-induced contraction, an effect that may have been nonspecific. This study suggests that stretch can act, probably directly, on smooth muscle in small feline pulmonary arteries to elicit contraction and that it may be a determinant of pulmonary vascular tone. In addition, feline pulmonary arteries are suitable for the in vitro study of stretch-induced contraction.

Somatosensory spatial attention modulates amplitudes, latencies, and latency jitter of laser-evoked brain potentials.

PubMed

Franz, Marcel; Nickel, Moritz M; Ritter, Alexander; Miltner, Wolfgang H R; Weiss, Thomas

2015-04-01

Several studies provided evidence that the amplitudes of laser-evoked potentials (LEPs) are modulated by attention. However, previous reports were based on across-trial averaging of LEP responses at the expense of losing information about intertrial variability related to attentional modulation. The aim of this study was to investigate the effects of somatosensory spatial attention on single-trial parameters (i.e., amplitudes, latencies, and latency jitter) of LEP components (N2 and P2). Twelve subjects participated in a sustained spatial attention paradigm while noxious laser stimuli (left hand) and noxious electrical stimuli (right hand) were sequentially delivered to the dorsum of the respective hand with nonnoxious air puffs randomly interspersed within the sequence of noxious stimuli. Participants were instructed to mentally count all stimuli (i.e., noxious and nonnoxious) applied to the attended location. Laser stimuli, presented to the attended hand (ALS), elicited larger single-trial amplitudes of the N2 component compared with unattended laser stimuli (ULS). In contrast, single-trial amplitudes of the P2 component were not significantly affected by spatial attention. Single-trial latencies of the N2 and P2 were significantly smaller for ALS vs. ULS. Additionally, the across-trial latency jitter of the N2 component was reduced for ALS. Conversely, the latency jitter of the P2 component was smaller for ULS compared with ALS. With the use of single-trial analysis, the study provided new insights into brain dynamics of LEPs related to spatial attention. Our results indicate that single-trial parameters of LEP components are differentially modulated by spatial attention. Copyright © 2015 the American Physiological Society.

Proviral Latency, Persistent Human Immunodeficiency Virus Infection, and the Development of Latency Reversing Agents

PubMed Central

Archin, Nancie M.

2017-01-01

Abstract Quiescent proviral genomes that persist during human immunodeficiency virus type 1 (HIV-1) infection despite effective antiretroviral therapy (ART) can fuel rebound viremia after ART interruption and is a central obstacle to the cure of HIV infection. The induction of quiescent provirus is the goal of a new class of potential therapeutics, latency reversing agents (LRAs). The discovery, development, and testing of HIV LRAs is a key part of current efforts to develop latency reversal and viral clearance strategies to eradicate established HIV infection. The development of LRAs is burdened by many uncertainties that make drug discovery difficult. The biology of HIV latency is complex and incompletely understood. Potential targets for LRAs are host factors, and the potential toxicities of host-directed therapies in individuals that are otherwise clinically stable may be unacceptable. Assays to measure latency reversal and assess the effectiveness of potential therapeutics are complex and incompletely validated. Despite these obstacles, novel LRAs are under development and beginning to enter combination testing with viral clearance strategies. It is hoped that the steady advances in the development of LRAs now being paired with emerging immunotherapeutics to clear persistently infected cells will soon allow measurable clinical advances toward an HIV cure. PMID:28520964

Short Durations of Static Stretching when Combined with Dynamic Stretching do not Impair Repeated Sprints and Agility

PubMed Central

Wong, Del P.; Chaouachi, Anis; Lau, Patrick W.C.; Behm, David G.

2011-01-01

This study aimed to compare the effect of different static stretching durations followed by dynamic stretching on repeated sprint ability (RSA) and change of direction (COD). Twenty-five participants performed the RSA and COD tests in a randomized order. After a 5 min aerobic warm up, participants performed one of the three static stretching protocols of 30 s, 60 s or 90 s total duration (3 stretches x 10 s, 20 s or 30 s). Three dynamic stretching exercises of 30 s duration were then performed (90 s total). Sit-and-reach flexibility tests were conducted before the aerobic warm up, after the combined static and dynamic stretching, and post- RSA/COD test. The duration of static stretching had a positive effect on flexibility with 36.3% and 85.6% greater sit-and-reach scores with the 60 s and 90 s static stretching conditions respectively than with the 30 s condition (p ≤ 0.001). However there were no significant differences in RSA and COD performance between the 3 stretching conditions. The lack of change in RSA and COD might be attributed to a counterbalancing of static and dynamic stretching effects. Furthermore, the short duration (≤ 90 s) static stretching may not have provided sufficient stimulus to elicit performance impairments. Key points The duration of combined static and dynamic stretching had a positive effect on flexibility with 36.3% and 85.6% greater sit and reach scores with the 60 s and 90 s static stretching conditions respectively than with the 30 s condition (p ≤ 0.001). No significant differences in RSA and COD between the 3 stretching conditions. The lack of change in RSA and COD might be attributed to a counterbalancing of static and dynamic stretching effects. The short duration (≤ 90 s) static stretching may not have provided sufficient stimulus to elicit performance impairments. PMID:24149890

Short Durations of Static Stretching when Combined with Dynamic Stretching do not Impair Repeated Sprints and Agility.

PubMed

Wong, Del P; Chaouachi, Anis; Lau, Patrick W C; Behm, David G

2011-01-01

This study aimed to compare the effect of different static stretching durations followed by dynamic stretching on repeated sprint ability (RSA) and change of direction (COD). Twenty-five participants performed the RSA and COD tests in a randomized order. After a 5 min aerobic warm up, participants performed one of the three static stretching protocols of 30 s, 60 s or 90 s total duration (3 stretches x 10 s, 20 s or 30 s). Three dynamic stretching exercises of 30 s duration were then performed (90 s total). Sit-and-reach flexibility tests were conducted before the aerobic warm up, after the combined static and dynamic stretching, and post- RSA/COD test. The duration of static stretching had a positive effect on flexibility with 36.3% and 85.6% greater sit-and-reach scores with the 60 s and 90 s static stretching conditions respectively than with the 30 s condition (p ≤ 0.001). However there were no significant differences in RSA and COD performance between the 3 stretching conditions. The lack of change in RSA and COD might be attributed to a counterbalancing of static and dynamic stretching effects. Furthermore, the short duration (≤ 90 s) static stretching may not have provided sufficient stimulus to elicit performance impairments. Key pointsThe duration of combined static and dynamic stretching had a positive effect on flexibility with 36.3% and 85.6% greater sit and reach scores with the 60 s and 90 s static stretching conditions respectively than with the 30 s condition (p ≤ 0.001).No significant differences in RSA and COD between the 3 stretching conditions.The lack of change in RSA and COD might be attributed to a counterbalancing of static and dynamic stretching effects.The short duration (≤ 90 s) static stretching may not have provided sufficient stimulus to elicit performance impairments.

Accommodation and vergence latencies in human infants

PubMed Central

Tondel, Grazyna M.; Candy, T. Rowan

2008-01-01

Purpose Achieving simultaneous single and clear visual experience during postnatal development depends on the temporal relationship between accommodation and vergence, in addition to their accuracies. This study was designed to examine one component of the dynamic relationship, the latencies of the responses. Methods Infants and adults were tested in three conditions i) Binocular viewing of a target moving in depth at 5cm/s (closed loop) ii) monocular viewing of the same target (vergence open loop) iii) binocular viewing of a low spatial frequency Difference of Gaussian target during a prism induced step change in retinal disparity (accommodation open loop). Results There was a significant correlation between accommodation and vergence latencies in binocular conditions for infants from 7 to 23 weeks of age. Some of the infants, as young as 7 or 8 weeks, generated adult-like latencies of less than 0.5 s. Latencies in the vergence open loop and accommodation open loop conditions tended to be shorter for the stimulated system than the open loop system in both cases, and all latencies were typically less than 2 seconds across the infant age range. Conclusions Many infants between 7 and 23 weeks of age were able to generate accommodation and vergence responses with latencies of less than a second in full binocular closed loop conditions. The correlation between the latencies in the two systems suggests that they are limited by related factors from the earliest ages tested. PMID:18199466

Accommodation and vergence latencies in human infants.

PubMed

Tondel, Grazyna M; Candy, T Rowan

2008-02-01

Achieving simultaneous single and clear visual experience during postnatal development depends on the temporal relationship between accommodation and vergence, in addition to their accuracies. This study was designed to examine one component of the dynamic relationship, the latencies of the responses. Infants and adults were tested in three conditions (i) binocular viewing of a target moving in depth at 5 cm/s (closed loop) (ii) monocular viewing of the same target (vergence open loop) (iii) binocular viewing of a low spatial frequency Difference of Gaussian target during a prism induced step change in retinal disparity (accommodation open loop). There was a significant correlation between accommodation and vergence latencies in binocular conditions for infants from 7 to 23 weeks of age. Some of the infants, as young as 7 or 8 weeks, generated adult-like latencies of less than 0.5 s. Latencies in the vergence open loop and accommodation open loop conditions tended to be shorter for the stimulated system than the open loop system in both cases, and all latencies were typically less than 2 s across the infant age range. Many infants between 7 and 23 weeks of age were able to generate accommodation and vergence responses with latencies of less than a second in full binocular closed loop conditions. The correlation between the latencies in the two systems suggests that they are limited by related factors from the earliest ages tested.

Neglected rupture of the quadriceps tendon in a patient with chronic renal failure (case report and review of the literature).

PubMed

Hassani, Zouhir Ameziane; Boufettal, Moncef; Mahfoud, Moustapha; Elyaacoubi, Moradh

2014-01-01

Spontaneous ruptures of the quadriceps tendon are infrequent injuries, it is seen primarily in patients with predisposing diseases such as gout, rheumatoid arthritis and chronic renal failure. A 32-year-old man had a history of end stage renal disease and received regular hemodialysis treatment for more than 5 years. He was admitted in our service for total functional impotence of the right lower limb with knee pain after a common fall two months ago. The radiogram showed a ''patella baja" with suprapatellar calcifications. The ultrasound and MRI showed an aspect of rupture of the quadriceps tendon in its proximal end with retraction of 3 cm. Quadriceps tendon repair was performed with a lengthening plasty, and the result was satisfactory after a serial rehabilitation program. The diagnosis of quadriceps tendon ruptures needs more attention in patients with predisposing diseases. They should not be unknown because the treatment of neglected lesions is more difficult. We insist on the early surgical repair associated with early rehabilitation that can guarantee recovery of good active extension.

Atypical long-latency auditory event-related potentials in a subset of children with specific language impairment

PubMed Central

Bishop, Dorothy VM; Hardiman, Mervyn; Uwer, Ruth; von Suchodoletz, Waldemar

2007-01-01

It has been proposed that specific language impairment (SLI) is the consequence of low-level abnormalities in auditory perception. However, studies of long-latency auditory ERPs in children with SLI have generated inconsistent findings. A possible reason for this inconsistency is the heterogeneity of SLI. The intraclass correlation (ICC) has been proposed as a useful statistic for evaluating heterogeneity because it allows one to compare an individual's auditory ERP with the grand average waveform from a typically developing reference group. We used this method to reanalyse auditory ERPs from a sample previously described by Uwer, Albrecht and von Suchodoletz (2002). In a subset of children with receptive SLI, there was less correspondence (i.e. lower ICC) with the normative waveform (based on the control grand average) than for typically developing children. This poorer correspondence was seen in responses to both tone and speech stimuli for the period 100–228 ms post stimulus onset. The effect was lateralized and seen at right- but not left-sided electrodes. PMID:17683344

Free Bone Plug Quadriceps Tendon Harvest and Suspensory Button Attachment for Anterior Cruciate Ligament Reconstruction.

PubMed

Todor, Adrian; Caterev, Sergiu; Nistor, Dan Viorel; Khallouki, Youssef

2016-06-01

The most commonly used autografts for anterior cruciate ligament reconstruction are the bone-patellar tendon-bone and hamstring tendons. Each has its advantages and limitations. The bone-patellar tendon-bone autograft can lead to more donor-site morbidity, and the hamstring autograft can be unpredictable in size. The quadriceps tendon, with or without a bone block, has been described as an alternative graft source and has been used especially in revision cases, but in recent years, it has attracted attention even for primary cases. We report a technique for harvesting a free bone quadriceps tendon graft and attaching an extracortical button for femoral fixation for anterior cruciate ligament reconstruction.

Stretching, twisting and supercoiling in short, single DNA molecules

NASA Astrophysics Data System (ADS)

Lam, Pui-Man; Zhen, Yi

2018-02-01

We had combined the Neukirch-Marko model that describes the extension, torque and supercoiling in single, stretched and twisted DNA of infinite contour length, with a form of the free energy suggested by Sinha and Samuels to describe short DNA, with contour length only a few times the persistence length. We find that the free energy of the stretched but untwisted DNA, is significantly modified from its infinitely length value and this in turn modifies significantly the torque and supercoiling. We show that this is consistent with short DNA being more flexible than infinitely long DNA. We hope our results will stimulate experimental investigation of torque and supercoiling in short DNA.

Effect of thumb anaesthesia on weight perception, muscle activity and the stretch reflex in man.

PubMed Central

Marsden, C D; Rothwell, J C; Traub, M M

1979-01-01

1. We have confirmed the results of Gandevia & McCloskey (1977) on the effect of thumb anaesthesia on perception of weights lifted by the thumb. Weights lifted by flexion feel heavier and weights lifted by extension feel lighter. 2. The change in size of the long-latency stretch reflex in flexor pollicis longus or extensor pollicis longus after thumb anaesthesia cannot explain the effect on weight perception by removal or augmentation of the background servo assistance to muscular contraction. 3. During smooth thumb flexion, thumb anaesthesia increases e.m.g. activity in flexor pollicis longus and extensor pollicis longus for any given opposing torque. 4. During smooth thumb extension the opposite occurs: e.m.g. activity in both extensor and flexor pollicis longus decreases. 5. Clamping the thumb at the proximal phalanx to limit movement solely to the interphalangeal joint reduces or abolishes the effect of anaesthesia on both weight perception and e.m.g. activity during both flexion or extension tasks. 6. Gandevia & McCloskey's findings on the distorting effects of thumb anaesthesia on weight perception cannot be used to support the hypothesis of an efferent monitoring system of the sense of effort. Our results emphasize the close functional relationship between cutaneous and joint afferent information and motor control. PMID:512948

Factors influencing the latency of simple reaction time

PubMed Central

Woods, David L.; Wyma, John M.; Yund, E. William; Herron, Timothy J.; Reed, Bruce

2015-01-01

Simple reaction time (SRT), the minimal time needed to respond to a stimulus, is a basic measure of processing speed. SRTs were first measured by Francis Galton in the 19th century, who reported visual SRT latencies below 190 ms in young subjects. However, recent large-scale studies have reported substantially increased SRT latencies that differ markedly in different laboratories, in part due to timing delays introduced by the computer hardware and software used for SRT measurement. We developed a calibrated and temporally precise SRT test to analyze the factors that influence SRT latencies in a paradigm where visual stimuli were presented to the left or right hemifield at varying stimulus onset asynchronies (SOAs). Experiment 1 examined a community sample of 1469 subjects ranging in age from 18 to 65. Mean SRT latencies were short (231, 213 ms when corrected for hardware delays) and increased significantly with age (0.55 ms/year), but were unaffected by sex or education. As in previous studies, SRTs were prolonged at shorter SOAs and were slightly faster for stimuli presented in the visual field contralateral to the responding hand. Stimulus detection time (SDT) was estimated by subtracting movement initiation time, measured in a speeded finger tapping test, from SRTs. SDT latencies averaged 131 ms and were unaffected by age. Experiment 2 tested 189 subjects ranging in age from 18 to 82 years in a different laboratory using a larger range of SOAs. Both SRTs and SDTs were slightly prolonged (by 7 ms). SRT latencies increased with age while SDT latencies remained stable. Precise computer-based measurements of SRT latencies show that processing speed is as fast in contemporary populations as in the Victorian era, and that age-related increases in SRT latencies are due primarily to slowed motor output. PMID:25859198

Quadriceps rate of torque development and disability in individuals with anterior cruciate ligament reconstruction.

PubMed

Davis, Hope C; Troy Blackburn, J; Ryan, Eric D; Luc-Harkey, Brittney A; Harkey, Matthew S; Padua, Darin A; Pietrosimone, Brian

2017-07-01

The purpose of this study was to determine associations between self-reported function (International Knee Documentation Committee Index), isometric quadriceps strength and rate of torque development in individuals with a unilateral anterior cruciate ligament reconstruction. Forty-one individuals [31% male, BMI mean 25 (SD 4) kg/m 2 , months post anterior cruciate ligament reconstruction mean 49 (SD 40)] completed the self-reported function and isometric quadriceps function testing. Rate of torque development was assessed at 0-100ms (early), 100-200ms (late) ms, and peak following the onset of contraction. Associations were examined between rate of torque development, strength, and self-reported function. Linear regression was used to determine the unique amount of variance explained by the combination of rate of torque development and strength. Higher rate of torque development 100-200ms is weakly associated with higher self-reported function in individuals with a unilateral anterior cruciate ligament reconstruction (r=0.274, p=0.091); however, rate of torque development 100-200ms does not predict a significant amount of variance in self-reported function after accounting for strength (ΔR 2 =0.003, P=0.721). Quadriceps strength has a greater influence on self-reported function compared to rate of torque development in individuals with an anterior cruciate ligament reconstruction with time from surgery. Copyright © 2017 Elsevier Ltd. All rights reserved.

Isometric quadriceps strength determines sailing performance and neuromuscular fatigue during an upwind sailing emulation.

PubMed

Bourgois, Jan G; Callewaert, Margot; Celie, Bert; De Clercq, Dirk; Boone, Jan

2016-01-01

This study investigates the physiological responses to upwind sailing on a laser emulation ergometer and analyses the components of the physical profile that determine the physiological responses related to sailing level. Ten male high-level laser sailors performed an upwind sailing test, incremental cycling test and quadriceps strength test. During the upwind sailing test, heart rate (HR), oxygen uptake, ventilation, respiratory exchange ratio, rating of perceived exertion (RPE) and lactate concentration were measured, combined with near-infrared spectroscopy (NIRS) and electromyography (EMG) registration of the M. Vastus lateralis. Repeated measures ANOVA showed for the cardio-respiratory, metabolic and muscles responses (mean power frequency [MPF], root mean square [RMS], deoxy[Hb+Mb]) during the upwind sailing test an initial significant increase followed by a stabilisation, despite a constant increase in RPE. Stepwise regression analysis showed that better sailing level was for 46.5% predicted by lower MPF decrease. Lower MPF decrease was for 57.8% predicted by a higher maximal isometric quadriceps strength. In conclusion, this study indicates that higher sailing level was mainly determined by a lower rate of neuromuscular fatigue during the upwind sailing test (as indicated by MPF decrease). Additionally, the level of neuromuscular fatigue was mainly determined by higher maximal isometric quadriceps strength stressing the importance of resistance training in the planning of training.

The molecular basis of herpes simplex virus latency

PubMed Central

Nicoll, Michael P; Proença, João T; Efstathiou, Stacey

2012-01-01

Herpes simplex virus type 1 is a neurotropic herpesvirus that establishes latency within sensory neurones. Following primary infection, the virus replicates productively within mucosal epithelial cells and enters sensory neurones via nerve termini. The virus is then transported to neuronal cell bodies where latency can be established. Periodically, the virus can reactivate to resume its normal lytic cycle gene expression programme and result in the generation of new virus progeny that are transported axonally back to the periphery. The ability to establish lifelong latency within the host and to periodically reactivate to facilitate dissemination is central to the survival strategy of this virus. Although incompletely understood, this review will focus on the mechanisms involved in the regulation of latency that centre on the functions of the virus-encoded latency-associated transcripts (LATs), epigenetic regulation of the latent virus genome and the molecular events that precipitate reactivation. This review considers current knowledge and hypotheses relating to the mechanisms involved in the establishment, maintenance and reactivation herpes simplex virus latency. PMID:22150699

Wrinkling instability of an inhomogeneously stretched viscous sheet

NASA Astrophysics Data System (ADS)

Srinivasan, Siddarth; Wei, Zhiyan; Mahadevan, L.

2017-07-01

Motivated by the redrawing of hot glass into thin sheets, we investigate the shape and stability of a thin viscous sheet that is inhomogeneously stretched in an imposed nonuniform temperature field. We first determine the associated base flow by solving the long-time-scale stretching flow of a flat sheet as a function of two dimensionless parameters: the normalized stretching velocity α and a dimensionless width of the heating zone β . This allows us to determine the conditions for the onset of an out-of-plane wrinkling instability stated in terms of an eigenvalue problem for a linear partial differential equation governing the displacement of the midsurface of the sheet. We show that the sheet can become unstable in two regions that are upstream and downstream of the heating zone where the minimum in-plane stress is negative. This yields the shape and growth rates of the most unstable buckling mode in both regions for various values of the stretching velocity and heating zone width. A transition from stationary to oscillatory unstable modes is found in the upstream region with increasing β , while the downstream region is always stationary. We show that the wrinkling instability can be entirely suppressed when the surface tension is large enough relative to the magnitude of the in-plane stress. Finally, we present an operating diagram that indicates regions of the parameter space that result in a required outlet sheet thickness upon stretching while simultaneously minimizing or suppressing the out-of-plane buckling, a result that is relevant for the glass redraw method used to create ultrathin glass sheets.

The effectiveness of manual stretching in the treatment of plantar heel pain: a systematic review

PubMed Central

2011-01-01

long-term follow up are needed to assess the efficacy of stretching. PMID:21703003

Laser Pulse-Stretching Using Multiple Optical Ring-Cavities

NASA Technical Reports Server (NTRS)

Kojima, Jun; Nguyen, Quang-Viet; Lee, Chi-Ming (Technical Monitor)

2002-01-01

We describe a simple and passive nanosecond-long (ns-long) laser 'pulse-stretcher' using multiple optical ring-cavities. We present a model of the pulse-stretching process for an arbitrary number of optical ring-cavities. Using the model, we optimize the design of a pulse-stretcher for use in a spontaneous Raman scattering excitation system that avoids laser-induced plasma spark problems. From the optimized design, we then experimentally demonstrate and verify the model with a 3-cavity pulse-stretcher system that converts a 1000 mJ, 8.4 ns-long input laser pulse into an approximately 75 ns-long (FWHM) output laser pulse with a peak power reduction of 0.10X, and an 83% efficiency.

Acute Effects of Dynamic Stretching on Muscle Flexibility and Performance: An Analysis of the Current Literature.

PubMed

Opplert, Jules; Babault, Nicolas

2018-02-01

Stretching has long been used in many physical activities to increase range of motion (ROM) around a joint. Stretching also has other acute effects on the neuromuscular system. For instance, significant reductions in maximal voluntary strength, muscle power or evoked contractile properties have been recorded immediately after a single bout of static stretching, raising interest in other stretching modalities. Thus, the effects of dynamic stretching on subsequent muscular performance have been questioned. This review aimed to investigate performance and physiological alterations following dynamic stretching. There is a substantial amount of evidence pointing out the positive effects on ROM and subsequent performance (force, power, sprint and jump). The larger ROM would be mainly attributable to reduced stiffness of the muscle-tendon unit, while the improved muscular performance to temperature and potentiation-related mechanisms caused by the voluntary contraction associated with dynamic stretching. Therefore, if the goal of a warm-up is to increase joint ROM and to enhance muscle force and/or power, dynamic stretching seems to be a suitable alternative to static stretching. Nevertheless, numerous studies reporting no alteration or even performance impairment have highlighted possible mitigating factors (such as stretch duration, amplitude or velocity). Accordingly, ballistic stretching, a form of dynamic stretching with greater velocities, would be less beneficial than controlled dynamic stretching. Notwithstanding, the literature shows that inconsistent description of stretch procedures has been an important deterrent to reaching a clear consensus. In this review, we highlight the need for future studies reporting homogeneous, clearly described stretching protocols, and propose a clarified stretching terminology and methodology.

Relationship between quadriceps strength and patellofemoral joint chondral lesions after anterior cruciate ligament reconstruction.

PubMed

Wang, Hai-Jun; Ao, Ying-Fang; Jiang, Dong; Gong, Xi; Wang, Yong-Jian; Wang, Jian; Yu, Jia-Kuo

2015-09-01

The incidence of the patellofemoral joint chondral lesions after anterior cruciate ligament reconstruction (ACLR) is disturbingly high. Few studies have assessed the factors affecting patellofemoral joint chondral lesions postoperatively. The recovery of quadriceps strength after ACLR could be associated with patellofemoral joint cartilage damage. Cohort study; Level of evidence, 3. A total of 88 patients who underwent arthroscopic anatomic double-bundle ACLR with hamstring autografts received second-look arthroscopy at the time of metal staple removal at an average of 24.1 months (range, 12-51 months) postoperatively. All patients underwent standardized isokinetic strength testing for bilateral quadriceps and hamstrings 1 to 2 days before second-look arthroscopy. The patients were divided into 2 groups: Patients in group 1 had a ≥20% deficit on the peak torque measures for quadriceps compared with that of the contralateral knee, whereas those in group 2 had a <20% deficit on peak torque. Cartilage status at the patellofemoral joint and tibiofemoral joint were evaluated by second-look arthroscopy and the Outerbridge classification. Other assessments included the International Knee Documentation Committee (IKDC) score, Tegner and Lysholm scores, side-to-side difference on KT-2000 arthrometer, and range of motion. There were 42 patients included in group 1 and 46 patients in group 2. The mean postoperative quadriceps peak torque of the involved knee compared with the contralateral knee was 70% (range, 57%-80%) in group 1 and 95% (range, 81%-116%) in group 2. For all patients, a significant worsening was seen in the patellar and trochlear cartilage (P = .030 and <.001, respectively) but not at the medial or lateral tibiofemoral joint after ACLR. A significant worsening in the status of both patellar and trochlear cartilage was seen after ACLR in group 1 (P = .013 and =.011, respectively) and of trochlear cartilage in group 2 (P = .006). Significantly fewer severe

Long-latency reductions in gamma power predict hemodynamic changes that underlie the negative BOLD signal.

PubMed

Boorman, Luke; Harris, Samuel; Bruyns-Haylett, Michael; Kennerley, Aneurin; Zheng, Ying; Martin, Chris; Jones, Myles; Redgrave, Peter; Berwick, Jason

2015-03-18

Studies that use prolonged periods of sensory stimulation report associations between regional reductions in neural activity and negative blood oxygenation level-dependent (BOLD) signaling. However, the neural generators of the negative BOLD response remain to be characterized. Here, we use single-impulse electrical stimulation of the whisker pad in the anesthetized rat to identify components of the neural response that are related to "negative" hemodynamic changes in the brain. Laminar multiunit activity and local field potential recordings of neural activity were performed concurrently with two-dimensional optical imaging spectroscopy measuring hemodynamic changes. Repeated measurements over multiple stimulation trials revealed significant variations in neural responses across session and animal datasets. Within this variation, we found robust long-latency decreases (300 and 2000 ms after stimulus presentation) in gamma-band power (30-80 Hz) in the middle-superficial cortical layers in regions surrounding the activated whisker barrel cortex. This reduction in gamma frequency activity was associated with corresponding decreases in the hemodynamic responses that drive the negative BOLD signal. These findings suggest a close relationship between BOLD responses and neural events that operate over time scales that outlast the initiating sensory stimulus, and provide important insights into the neurophysiological basis of negative neuroimaging signals. Copyright © 2015 Boorman et al.

Long-Latency Reductions in Gamma Power Predict Hemodynamic Changes That Underlie the Negative BOLD Signal

PubMed Central

Harris, Samuel; Bruyns-Haylett, Michael; Kennerley, Aneurin; Zheng, Ying; Martin, Chris; Jones, Myles; Redgrave, Peter; Berwick, Jason

2015-01-01

Studies that use prolonged periods of sensory stimulation report associations between regional reductions in neural activity and negative blood oxygenation level-dependent (BOLD) signaling. However, the neural generators of the negative BOLD response remain to be characterized. Here, we use single-impulse electrical stimulation of the whisker pad in the anesthetized rat to identify components of the neural response that are related to “negative” hemodynamic changes in the brain. Laminar multiunit activity and local field potential recordings of neural activity were performed concurrently with two-dimensional optical imaging spectroscopy measuring hemodynamic changes. Repeated measurements over multiple stimulation trials revealed significant variations in neural responses across session and animal datasets. Within this variation, we found robust long-latency decreases (300 and 2000 ms after stimulus presentation) in gamma-band power (30–80 Hz) in the middle-superficial cortical layers in regions surrounding the activated whisker barrel cortex. This reduction in gamma frequency activity was associated with corresponding decreases in the hemodynamic responses that drive the negative BOLD signal. These findings suggest a close relationship between BOLD responses and neural events that operate over time scales that outlast the initiating sensory stimulus, and provide important insights into the neurophysiological basis of negative neuroimaging signals. PMID:25788681

Reduced evolutionary rates in HIV-1 reveal extensive latency periods among replicating lineages.

PubMed

Immonen, Taina T; Leitner, Thomas

2014-10-16

HIV-1 can persist for the duration of a patient's life due in part to its ability to hide from the immune system, and from antiretroviral drugs, in long-lived latent reservoirs. Latent forms of HIV-1 may also be disproportionally involved in transmission. Thus, it is important to detect and quantify latency in the HIV-1 life cycle. We developed a novel molecular clock-based phylogenetic tool to investigate the prevalence of HIV-1 lineages that have experienced latency. The method removes alternative sources that may affect evolutionary rates, such as hypermutation, recombination, and selection, to reveal the contribution of generation-time effects caused by latency. Our method was able to recover latent lineages with high specificity and sensitivity, and low false discovery rates, even on relatively short branches on simulated phylogenies. Applying the tool to HIV-1 sequences from 26 patients, we show that the majority of phylogenetic lineages have been affected by generation-time effects in every patient type, whether untreated, elite controller, or under effective or failing treatment. Furthermore, we discovered extensive effects of latency in sequence data (gag, pol, and env) from reservoirs as well as in the replicating plasma population. To better understand our phylogenetic findings, we developed a dynamic model of virus-host interactions to investigate the proportion of lineages in the actively replicating population that have ever been latent. Assuming neutral evolution, our dynamic modeling showed that under most parameter conditions, it is possible for a few activated latent viruses to propagate so that in time, most HIV-1 lineages will have been latent at some time in their past. These results suggest that cycling in and out of latency plays a major role in the evolution of HIV-1. Thus, no aspect of HIV-1 evolution can be fully understood without considering latency - including treatment, drug resistance, immune evasion, transmission, and pathogenesis.

Enhanced long-latency somatosensory potentials in major depressive disorder.

PubMed

Dietl, T; Dirlich, G; Vogl, L; Nickel, T; Sonntag, A; Strian, F; Lechner, C

2001-01-01

Bodily misperceptions are a frequent symptom in major depressive disorder. A reduced ability to deflect attention from somatosensory stimuli may contribute to the generation of unpleasant bodily sensations and co-occur with altered habituation of the brain electric reactions to somatosensory stimuli. The aim of the present study was to explore whether attention-related components of somatosensory evoked potentials (SSEP) and the habituation of these components are altered in major depression. Fifteen patients with major depressive disorder were compared to an age- and gender-matched group of 15 healthy controls. A series of identical, intrusive but not painful electric stimuli were applied to the left index finger for 48 min. Averaged SSEP were computed from multichannel EEG recordings for consecutive recording blocks of the experiment, each block containing 162 stimuli. Based on these data the habituation process of late components of the SSEP was analysed in two latency intervals (50-150, 170-370 ms). Patients showed significantly enhanced reactions throughout the entire experiment. The persistence of enhanced SSEP components throughout the habituation process may be caused by a deficit in reducing the activity of attention-related brain processes concerned with intrusive, yet behaviourally irrelevant, continued stimulation in the state of major depression.

High-Pressure Balloon-Assisted Stretching of the Coracohumeral Ligament to Determine the Optimal Stretching Positions: A Cadaveric Study.

PubMed

Baek, Sora; Lee, Kyu Jin; Kim, Keewon; Han, Seung-Ho; Lee, U-Young; Lee, Kun-Jai; Chung, Sun Gun

2016-10-01

The coracohumeral ligament (CHL) is a thick capsular structure and markedly thickened when affected by adhesive capsulitis. Therapeutic stretching is the most commonly applied treatment for adhesive capsulitis, but optimal stretching postures for maximal therapeutic effects on the CHL have not been fully investigated. To investigate the most effective stretching direction for the CHL by measuring the stretching intensity in 5 different directions and to determine whether the stretching intervention resulted in loosening of the ligament by comparing the changes of CHL tightness before and after stretching. Biomechanical cadaver study. Academic institution cadaver laboratory. Nine fresh frozen cadaveric shoulders. A high-pressure balloon catheter inserted under the CHL and intraballoon pressure was measured, to evaluate CHL tightness without ligament damage as well as to augment and monitor stretching intensity. To find the optimal stretching direction, the glenohumeral joint was stretched from the neutral position into 5 directions sequentially under pressure-monitoring: flexion, extension [EX], external rotation [ER], EX+ER, and EX+ER+adduction [AD] directions. CHL tightness was determined by a surrogate parameter, the additional pressure created by the overlying CHL. The pressure increase (ΔP str ) by a specific directional stretch was considered as the stretching intensity. ΔP str by the 5 directions were mean (standard deviation) values of 0.03 ± 0.07 atm, 0.87 ± 1.31 atm, 1.13 ± 1.36 atm, 1.49 ± 1.32 atm, and 2.10 ± 1.70 atm, respectively, revealing the highest ΔP str by the EX+ER+AD stretch (P < .05). The balloon pressure by the overlying CHL was decreased from 0.45 ± 0.35 atm to 0.18 ± 0.14 atm (P = .012) before and after the stretching manipulation. EX+ER+AD of the glenohumeral joint resulted in the greatest increase in balloon pressure, implying that it could be the most effective stretching direction. A series of stretching manipulations

Prophylactic stretching does not reduce cramp susceptibility.

PubMed

Miller, Kevin C; Harsen, James D; Long, Blaine C

2018-03-01

Some clinicians advocate stretching to prevent muscle cramps. It is unknown whether static or proprioceptive neuromuscular facilitation (PNF) stretching increases cramp threshold frequency (TF c ), a quantitative measure of cramp susceptibility. Fifteen individuals completed this randomized, counterbalanced, cross-over study. We measured passive hallux range of motion (ROM) and then performed 3 minutes of either static stretching, PNF stretching (hold-relax-with agonist contraction), or no stretching. ROM was reassessed and TF c was measured. PNF stretching increased hallux extension (pre-PNF 81 ± 11°, post-PNF 90 ± 10°; P < 0.05) but not hallux flexion (pre-PNF 40 ± 7°, post-PNF 40 ± 7°; P > 0.05). Static stretching increased hallux extension (pre-static 80 ± 11°, post-static 88 ± 9°; P < 0.05) but not hallux flexion (pre-static 38 ± 9°, post-static 39 ± 8°; P > 0.05). No ROM changes occurred with no stretching (P > 0.05). TF c was unaffected by stretching (no stretching 18 ± 7 Hz, PNF 16 ± 4 Hz, static 16 ± 5 Hz; P = 0.37). Static and PNF stretching increased hallux extension, but neither increased TF c . Acute stretching may not prevent muscle cramping. Muscle Nerve 57: 473-477, 2018. © 2017 Wiley Periodicals, Inc.

Sixty-five years of the long march in protein secondary structure prediction: the final stretch?

PubMed Central

Yang, Yuedong; Gao, Jianzhao; Wang, Jihua; Heffernan, Rhys; Hanson, Jack; Paliwal, Kuldip; Zhou, Yaoqi

2018-01-01

Abstract Protein secondary structure prediction began in 1951 when Pauling and Corey predicted helical and sheet conformations for protein polypeptide backbone even before the first protein structure was determined. Sixty-five years later, powerful new methods breathe new life into this field. The highest three-state accuracy without relying on structure templates is now at 82–84%, a number unthinkable just a few years ago. These improvements came from increasingly larger databases of protein sequences and structures for training, the use of template secondary structure information and more powerful deep learning techniques. As we are approaching to the theoretical limit of three-state prediction (88–90%), alternative to secondary structure prediction (prediction of backbone torsion angles and Cα-atom-based angles and torsion angles) not only has more room for further improvement but also allows direct prediction of three-dimensional fragment structures with constantly improved accuracy. About 20% of all 40-residue fragments in a database of 1199 non-redundant proteins have <6 Å root-mean-squared distance from the native conformations by SPIDER2. More powerful deep learning methods with improved capability of capturing long-range interactions begin to emerge as the next generation of techniques for secondary structure prediction. The time has come to finish off the final stretch of the long march towards protein secondary structure prediction. PMID:28040746

Characterization of herpes simplex virus type 2 latency-associated transcription in human sacral ganglia and in cell culture.

PubMed

Croen, K D; Ostrove, J M; Dragovic, L; Straus, S E

1991-01-01

The ability of herpes simplex virus type 2 (HSV-2) to establish latency in and reactivate from sacral dorsal root sensory ganglia is the basis for recurrent genital herpes. The expression of HSV-2 genes in latently infected human sacral ganglia was investigated by in situ hybridization. Hybridizations with a probe from the long repeat region of HSV-2 revealed strong nuclear signals overlying neurons in sacral ganglia from five of nine individuals. The RNA detected overlaps with the transcript for infected cell protein O but in the opposite, or "anti-sense," orientation. These observations mimic those made previously with HSV-1 in human trigeminal ganglia and confirm the recent findings during latency in HSV-2-infected mice and guinea pigs. Northern hybridization of RNA from infected Vero cells showed that an HSV-2 latency-associated transcript was similar in size to the larger (1.85 kb) latency transcript of HSV-1. Thus, HSV-1 and HSV-2 latency in human sensory ganglia are similar, if not identical, in terms of their cellular localization and pattern of transcription.

Ultrasound-Guided Removal of an Infected Loose Body from the Quadriceps Muscle.

PubMed

Razdan, Rishi N; Dube, Tiffany; Specht, Neil

2008-01-01

We present the case of a 35 year-old male with pain and swelling in his right thigh. By CT and sonography, an abscess was localized to the deep, anteromedial, mid-thigh within the quadriceps muscle, along with a 1.3 cm loose body. The infected loose body was removed under ultrasound guidance without complications.

Prospective multicentre study of the clinical and functional outcomes following quadriceps tendon repair with suture anchors.

PubMed

Mille, F; Adam, A; Aubry, S; Leclerc, G; Ghislandi, X; Sergent, P; Garbuio, P

2016-01-01

Quadriceps tendon avulsions are typically treated by reattaching the tendon through bone tunnels, with or without tendon or hardware augmentation. The operated knee joint can be moved right away; however, tendon grafting or tension banding will be required to protect the repair, and the hardware must be removed later on. The goal of this study was to evaluate the clinical and functional outcomes when suture anchors are used to reattached torn quadriceps tendon, and also to assess tendon healing using MRI. Thirteen consecutive patients with avulsed quadriceps tendons were operated and then followed prospectively. The surgical technique consisted of tendon reattachment using at least three anchors, in addition to intratendinous weaving of the sutures. Weight bearing was allowed while using a splint. Rehabilitation was initiated immediately after surgery according to a set protocol. Eleven patients were followed for a mean of 14.7 months. Two retears occurred in patients who did not wear the splint. Eighty-two per cent of patients were satisfied or very satisfied with the outcome. The mean knee flexion was 124.5°. All patients were able to return to their pre-injury activity levels. The mean time for clinical and functional recovery was 3 months. MRI performed 6 months after the surgical repair revealed good tendon healing. This was the first prospective study performed on quadriceps avulsion patients undergoing suture anchor repair. Prior clinical case reports have shown that this method leads to predictable clinical and functional results. Our results were comparable to those in published cases. The procedure is simpler when only suture anchors are used. Tendon healing was observed on MRI in all cases. This simple, reproducible technique is free of the drawbacks associated with the typical repair augmentation.

The effect of age on hamstring passive properties after a 10-week stretch training

PubMed Central

Haab, Thomas; Wydra, Georg

2017-01-01

[Purpose] Degenerative changes take place in the musculoskeletal system of elderly people, resulting in a reduced range of motion. For this reason, stretch training is recommended for elderly individuals. To date, there have been no studies of the adaptations of the passive properties of muscles following long-term stretch training. The aim of this study is to investigate the hamstring elasticity of elderly people following a 10-week stretch training and compare the results to a younger cohort. [Subjects and Methods] The experimental groups consisted of 15 younger (24.0 ± 4.0 years) and 14 older (65.1 ± 7.9 years) individuals. Both experimental groups undertook a standardised 10-week static passive hamstring stretch training. Passive properties of the hamstring were measured with an instrumented Straight Leg Raise Test. [Results] After a 10-week stretch training, there were increases in range of motion, passive resistive force and passive elastic energy in both age groups. Passive elastic stiffness decreased. Changes of hamstring passive properties did not differ significantly between age groups after a 10-week stretch training. [Conclusion] Increasing age has a negative effect on muscle passive properties, but older individuals benefit from regular stretch training, just as younger individuals do. PMID:28626322

Ego Functioning During Latency

PubMed Central

Adams, Milton S.

1979-01-01

The latency period is an extremely important transition between the preschool years and adolescence. Normal ego functioning is described, especially cognition, socialization, motor development, and defensive functions. PMID:529320

Ultrasonographic assessment of the quadriceps muscle and femoral cartilage in transtibial amputees using different prostheses.

PubMed

Şahin Onat, Şule; Malas, Fevziye Ünsal; Öztürk, Gökhan Tuna; Akkaya, Nuray; Kara, Murat; Özçakar, Levent

2016-08-01

In patients with lower limb amputations, gait alteration, increased loading on the intact extremity, and use of prosthesis may lead to joint degeneration. To explore the effects of prosthesis type on quadriceps muscle and distal femoral cartilage thicknesses in transtibial amputees. A cross-sectional study. A total of 38 below-knee amputees were enrolled in the study, of which 13 patients were using vacuum system type prosthesis and 25 patients were using silicon liner pin system prosthesis. Patients' femoral cartilage and quadriceps muscle thickness measurements were performed using musculoskeletal ultrasound. When compared with the intact sides, cartilage and rectus femoris, vastus intermedius, and vastus medialis muscle thickness values were significantly decreased on the amputee sides (all p < 0.05). Clinical characteristics and ultrasound measurements were similar between the two groups except the lateral and medial femoral condyle thicknesses, thinner in the silicon liner pin system users (both p < 0.05). The distal femoral cartilage and quadriceps muscle thicknesses were found to be decreased on the amputated sides, and the negative impact on the cartilage seemed to be worse in the silicon liner pin system users. This study might provide another argument as regards the preference of vacuum system type prosthesis to prevent possible knee osteoarthritis due to cartilage thinning in adult transtibial amputees. © The International Society for Prosthetics and Orthotics 2015.

Barriers to performing stretching exercises among Korean-Chinese female migrant workers in Korea.

PubMed

Lee, Hyeonkyeong; Wilbur, JoEllen; Chae, Duckhee; Lee, Kyongeun; Lee, Meenhye

2015-01-01

The purpose of this study was to investigate the barriers to performing stretching exercise experienced by Korean-Chinese female migrant workers during a community-based 12-week stretching exercise intervention trial. Qualitative secondary data analysis was conducted using telephone counseling interview transcripts from 27 middle-aged, Korean-Chinese migrant women workers. A semistructured interview question asking barriers to performing stretching exercise was given to women who did not adhere to recommended stretching exercise. During the 12-week home-based stretching exercise intervention trial, six telephone calls were made to participants biweekly to elicit barriers to performing stretching exercise. Directed content analysis approach was utilized using three barrier categories: intrapersonal, interpersonal, and work-related environmental factors based on the ecological model. Participants experienced an average of 2.5 barriers during the study period. Intrapersonal barriers included lack of time and lack of motivation, and interpersonal barriers included no family to provide support and also a feeling resistance from coworkers. Work-related environmental barriers included frequent job changes, long working hours, lack of rest time, and unpredictable job demands. The findings highlight that migrant workers in Korea face unique work-related difficulties which present barriers to exercise. © 2014 Wiley Periodicals, Inc.

Methodology for Calculating Latency of GPS Probe Data

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

Wang, Zhongxiang; Hamedi, Masoud; Young, Stanley

Crowdsourced GPS probe data, such as travel time on changeable-message signs and incident detection, have been gaining popularity in recent years as a source for real-time traffic information to driver operations and transportation systems management and operations. Efforts have been made to evaluate the quality of such data from different perspectives. Although such crowdsourced data are already in widespread use in many states, particularly the high traffic areas on the Eastern seaboard, concerns about latency - the time between traffic being perturbed as a result of an incident and reflection of the disturbance in the outsourced data feed - havemore » escalated in importance. Latency is critical for the accuracy of real-time operations, emergency response, and traveler information systems. This paper offers a methodology for measuring probe data latency regarding a selected reference source. Although Bluetooth reidentification data are used as the reference source, the methodology can be applied to any other ground truth data source of choice. The core of the methodology is an algorithm for maximum pattern matching that works with three fitness objectives. To test the methodology, sample field reference data were collected on multiple freeway segments for a 2-week period by using portable Bluetooth sensors as ground truth. Equivalent GPS probe data were obtained from a private vendor, and their latency was evaluated. Latency at different times of the day, impact of road segmentation scheme on latency, and sensitivity of the latency to both speed-slowdown and recovery-from-slowdown episodes are also discussed.« less

Effects of hamstring stretching on passive muscle stiffness vary between hip flexion and knee extension maneuvers.

PubMed

Miyamoto, N; Hirata, K; Kanehisa, H

2017-01-01

The purpose of this study was to examine whether the effects of hamstring stretching on the passive stiffness of each of the long head of the biceps femoris (BFl), semitendinosus (ST), and semimembranosus (SM) vary between passive knee extension and hip flexion stretching maneuvers. In 12 male subjects, before and after five sets of 90 s static stretching, passive lengthening measurements where knee or hip joint was passively rotated to the maximal range of motion (ROM) were performed. During the passive lengthening, shear modulus of each muscle was measured by ultrasound shear wave elastography. Both stretching maneuvers significantly increased maximal ROM and decreased passive torque at a given joint angle. Passive knee extension stretching maneuver significantly reduced shear modulus at a given knee joint angle in all of BFl, ST, and SM. In contrast, the stretching effect by passive hip flexion maneuver was significant only in ST and SM. The present findings indicate that the effects of hamstring stretching on individual passive muscles' stiffness vary between passive knee extension and hip flexion stretching maneuvers. In terms of reducing the muscle stiffness of BFl, stretching of the hamstring should be performed by passive knee extension rather than hip flexion. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Quadriceps tendon rupture: a biomechanical comparison of transosseous equivalent double-row suture anchor versus transosseous tunnel repair.

PubMed

Hart, Nathan D; Wallace, Matthew K; Scovell, J Field; Krupp, Ryan J; Cook, Chad; Wyland, Douglas J

2012-09-01

Quadriceps rupture off the patella is traditionally repaired by a transosseous tunnel technique, although a single-row suture anchor repair has recently been described. This study biomechanically tested a new transosseous equivalent (TE) double-row suture anchor technique compared with the transosseous repair for quadriceps repair. After simulated quadriceps-patella avulsion in 10 matched cadaveric knees, repairs were completed by either a three tunnel transosseous (TT = 5) or a TE suture anchor (TE = 5) technique. Double-row repairs were done using two 5.5 Bio-Corkscrew FT (fully threaded) (Arthrex, Inc., Naples, FL, USA) and two 3.5 Bio-PushLock anchors (Arthrex, Inc., Naples, FL, USA) with all 10 repairs done with #2 FiberWire suture (Arthrex, Inc., Naples, FL). Cyclic testing from 50 to 250 N for 250 cycles and pull to failure load (1 mm/s) were undertaken. Gap formation and ultimate tensile load (N) were recorded and stiffness data (N/mm) were calculated. Statistical analysis was performed using a Mann-Whitney U test and survival characteristics examined with Kaplan-Meier test. No significant difference was found between the TE and TT groups in stiffness (TE = 134 +/- 15 N/mm, TT = 132 +/- 26 N/mm, p = 0.28). The TE group had significantly less ultimate tensile load (N) compared with the TT group (TE = 447 +/- 86 N, TT = 591 +/- 84 N, p = 0.04), with all failures occurring at the suture eyelets. Although both quadriceps repairs were sufficiently strong, the transosseous repairs were stronger than the TE suture anchor repairs. The repair stiffness and gap formation were similar between the groups.

Trochanteric bursitis

MedlinePlus

... inflamed bursa. A new bursa sac will grow back. Prevention Overuse is the most common cause of hip bursitis. To help prevent hip pain: Always warm up and stretch before exercising and cool down afterward. Stretch your quadriceps and hamstrings. Don't increase the distance, intensity, and amount ...

Normative Quadriceps and Hamstring Muscle Strength Values for Female, Healthy, Elite Handball and Football Players.

PubMed

Risberg, May A; Steffen, Kathrin; Nilstad, Agnethe; Myklebust, Grethe; Kristianslund, Eirik; Moltubakk, Marie M; Krosshaug, Tron

2018-05-23

Risberg, MA, Steffen, K, Nilstad, A, Myklebust, G, Kristianslund, E, Moltubakk, MM, and Krosshaug, T. Normative quadriceps and hamstring muscle strength values for female, healthy, elite handball and football players. J Strength Cond Res XX(X): 000-000, 2018-This study presents normative values for isokinetic knee extension and flexion muscle strength tests in 350 elite, female, handball (n = 150) and football (n = 200) players. Isokinetic concentric muscle strength tests at 60°·sec were recorded bilaterally using a dynamometer. Peak torque (in Newton meter [N·m]), body mass normalized peak torque (N·m·kg), and hamstring to quadriceps ratio (H:Q ratio) for dominant and nondominant legs were recorded. The female elite players were 20.9 ± 4.0 years, started playing at the elite level at the age of 18.2 ± 2.7 years, with a mean of 9.7 ± 2.2 hours of weekly in-season training. Handball players demonstrated greater quadriceps muscle strength compared with football players (11.0%) (p < 0.001), also when normalized to body mass (4.1%) (p = 0.012), but not for weight-adjusted hamstring muscle strength. The H:Q ratio was higher on the dominant compared with the nondominant leg for handball players only (p = 0.012).The H:Q ratio was significantly lower for handball players (0.58) compared with football players (0.60) (p < 0.02). These normative values for isokinetic knee extension and flexion torques of healthy, elite, female handball and football players can be used to set rehabilitation goals for muscle strength after injury and enable comparison with uninjured legs. Significantly greater quadriceps muscle strength was found for handball players compared with football players, also when normalized to body mass.This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be

Exposure to microgravity for 30 days onboard Bion M1 caused muscle atrophy and impaired regeneration in murine femoral Quadriceps

NASA Astrophysics Data System (ADS)

Radugina, E. A.; Almeida, E. A. C.; Blaber, E.; Poplinskaya, V. A.; Markitantova, Y. V.; Grigoryan, E. N.

2018-02-01

Mechanical unloading in microgravity during spaceflight is known to cause muscular atrophy, changes in muscle fiber composition, gene expression, and reduction in regenerative muscle growth. Although some limited data exists for long-term effects of microgravity in human muscle, these processes have mostly been studied in rodents for short periods of time. Here we report on how long-term (30-day long) mechanical unloading in microgravity affects murine muscles of the femoral Quadriceps group. To conduct these studies we used muscle tissue from 6 microgravity mice, in comparison to habitat (7), and vivarium (14) ground control mice from the NASA Biospecimen Sharing Program conducted in collaboration with the Institute for Biomedical Problems of the Russian Academy of Sciences, during the Russian Bion M1 biosatellite mission in 2013. Muscle histomorphology from microgravity specimens showed signs of extensive atrophy and regenerative hypoplasia relative to ground controls. Specifically, we observed a two-fold decrease in the number of myonuclei, compared to vivarium and ground controls, and central location of myonuclei, low density of myofibers in the tissue, and of myofibrils within a fiber, as well as fragmentation and swelling of myofibers. Despite obvious atrophy, muscle regeneration nevertheless appeared to have continued after 30 days in microgravity as evidenced by thin and short newly formed myofibers. Many of them, however, showed evidence of apoptotic cells and myofibril degradation, suggesting that long-term unloading in microgravity may affect late stages of myofiber differentiation. Ground asynchronous and vivarium control animals demonstrated normal, well-developed tissue structure with sufficient blood and nerve supply and evidence of regenerative formation of new myofibers free of apoptotic nuclei. Regenerative activity of satellite cells in muscles was observed both in microgravity and ground control groups, using Pax7 and Myogenin

Stretching: Does It Help?

ERIC Educational Resources Information Center

Vardiman, Phillip; Carrand, David; Gallagher, Philip M.

2010-01-01

Stretching prior to activity is universally accepted as an important way to improve performance and help prevent injury. Likewise, limited flexibility has been shown to decrease functional ability and predispose a person to injuries. Although this is commonly accepted, appropriate stretching for children and adolescents involved with sports and…

Status of stretched-membrane heliostats

NASA Astrophysics Data System (ADS)

Alpert, D. J.; Houser, R. M.; Heckes, A. A.

1990-01-01

Since the early 1980s, Sandia National Laboratories has been developing stretched-membrane heliostats for solar central receiver power plants. They differ from conventional glass-mirror heliostats in that the optical surface is a stretched membrane -- a thin metal foil stretched over both sides of a large diameter ring. The reflective surface is provided by either a silvered-acrylic film or thin glass mirrors attached to the front membrane. Heliostats with single 14 m diameter (150 sq meter) stretched-membrane reflectors have been designed. Because of their simplicity and light weight, stretched-membrane heliostats are expected to cost up to one-third less than conventional glass-mirror designs. Two generations of 50 sq meter prototype stretched-membrane mirror modules have been built and evaluated at Sandia's Central Receiver Test Facility in Albuquerque, NM. They demonstrated that the optical performance of membrane heliostats rivals that of glass-mirror heliostats. The durability of the silvered-acrylic reflective film has improved so that a lifetime of at least 5 years is likely; methods of replacing the film in the field are being investigated. Sandia recently initiated the final phase of development: the design of fully integrated, market-ready heliostats. Field tests of these heliostats are planned to begin in FY90.

STRETCHING IMPACTS INFLAMMATION RESOLUTION IN CONNECTIVE TISSUE

PubMed Central

Berrueta, Lisbeth; Muskaj, Igla; Olenich, Sara; Butler, Taylor; Badger, Gary J.; Colas, Romain A.; Spite, Matthew; Serhan, Charles N.; Langevin, Helene M.

2016-01-01

Acute inflammation is accompanied from its outset by the release of specialized pro-resolving mediators (SPMs), including resolvins, that orchestrate the resolution of local inflammation. We showed earlier that, in rats with subcutaneous inflammation of the back induced by carrageenan, stretching for 10 minutes twice daily reduced inflammation and improved pain, two weeks after carrageenan injection. In this study, we hypothesized that stretching of connective tissue activates local pro-resolving mechanisms within the tissue in the acute phase of inflammation. In rats injected with carrageenan and randomized to stretch vs. no stretch for 48 hours, stretching reduced inflammatory lesion thickness and neutrophil count, and increased resolvin (RvD1) concentrations within lesions. Furthermore, subcutaneous resolvin injection mimicked the effect of stretching. In ex vivo experiments, stretching of connective tissue reduced the migration of neutrophils and increased tissue RvD1 concentration. These results demonstrate a direct mechanical impact of stretching on inflammation-regulation mechanisms within connective tissue. PMID:26588184

Latency as a region contrast: Measuring ERP latency differences with Dynamic Time Warping.

PubMed

Zoumpoulaki, A; Alsufyani, A; Filetti, M; Brammer, M; Bowman, H

2015-12-01

Methods for measuring onset latency contrasts are evaluated against a new method utilizing the dynamic time warping (DTW) algorithm. This new method allows latency to be measured across a region instead of single point. We use computer simulations to compare the methods' power and Type I error rates under different scenarios. We perform per-participant analysis for different signal-to-noise ratios and two sizes of window (broad vs. narrow). In addition, the methods are tested in combination with single-participant and jackknife average waveforms for different effect sizes, at the group level. DTW performs better than the other methods, being less sensitive to noise as well as to placement and width of the window selected. © 2015 Society for Psychophysiological Research.

Comparison of hamstring and quadriceps femoris electromyographic activity between men and women during a single-limb squat on both a stable and labile surface.

PubMed

Youdas, James W; Hollman, John H; Hitchcock, James R; Hoyme, Gregory J; Johnsen, Jeremiah J

2007-02-01

The purpose of this study was to determine if women are quadriceps dominant and men are hamstring dominant during the performance of a partial single-leg squat (SLS) on both a stable and labile ground surface against body weight resistance. Thirty healthy participants (15 men and 15 women) performed an SLS on both a stable surface and a 6.4-cm-thick vinyl pad. Surface electromyographic (EMG) recordings were obtained from the quadriceps femoris and hamstring muscles during the extension phase of the SLS. Statistical analysis revealed that women produced 14% more EMG activity (p = 0.04) in their quadriceps than the men during the SLS on a stable surface, whereas the men generated 18% more EMG activity (p = 0.04) in their hamstrings than the women during the SLS on a labile surface. Additionally, we found a statistically significant sex effect (p = 0.048) for the hamstring/quadriceps (H/Q) EMG ratio, which was 2.25 and 0.62, respectively, for men and women on the stable surface and 2.52 and 0.71, respectively, on the labile surface. We concluded that women are quadriceps dominant and men are hamstring dominant during the performance of SLS against body weight resistance on either a stable or labile surface condition. During an SLS, men showed an H/Q ratio approximately 3.5 times larger than their female counterparts, suggesting that men activate their hamstrings more effectively than women during an SLS. According to our data, the SLS may not be an ideal exercise for activating the hamstring muscles in women without additional neuromuscular training techniques, because women are quadriceps dominant during the SLS.

Predictive Displays for High Latency Teleoperation

DTIC Science & Technology

2016-08-04

PREDICTIVE DISPLAYS FOR HIGH LATENCY TELEOPERATION” Analysis of existing approach 3 C om m s. C hannel Vehicle OCU D Throttle, Steer, Brake D Video ...presents opportunity mitigate outgoing latency. • Video is not governed by physics, however, video is dependent on the state of the vehicle, which...Commands, estimates UDP: H.264 Video UDP: Vehicle state • C++ implementation • 2 threads • OpenCV for image manipulation • FFMPEG for video decoding

Association of Quadriceps Strength and Psychosocial Factors With Single-Leg Hop Performance in Patients With Meniscectomy.

PubMed

Hsu, Chao-Jung; George, Steven Z; Chmielewski, Terese L

2016-12-01

Clinicians use the single-leg hop test to assess readiness for return to sports after knee injury. Few studies have reported the results of single-leg hop testing after meniscectomy. Additionally, the contributions of impairments in quadriceps strength and psychosocial factors to single-leg hop performance are unknown. To compare single-leg hop performance (distance and landing mechanics) between limbs and to examine the association of single-leg hop performance with quadriceps strength and psychosocial factors in patients with meniscectomy. Descriptive laboratory study. A total of 22 subjects who underwent meniscectomy for traumatic meniscal tears received either standard rehabilitation alone or with additional quadriceps strengthening. Testing was conducted immediately postrehabilitation and at 1 year postsurgery. A single-leg hop test was performed bilaterally, and hop distance was used to create a hop symmetry index. Landing mechanics (peak knee flexion angle, knee extension moment, and peak vertical ground-reaction force) were analyzed with a motion-capture system and a force plate. An isokinetic dynamometer (60 deg/s) assessed knee extensor peak torque and rate of torque development (RTD 0-200ms and RTD 0-peak torque ). Questionnaires assessed fear of reinjury (Tampa Scale for Kinesiophobia [TSK-11]) and self-efficacy (Knee Activity Self-Efficacy [KASE]). Rehabilitation groups did not significantly differ in single-leg hop performance; therefore, groups were combined for further analyses. The mean hop symmetry index was 88.6% and 98.9% at postrehabilitation and 1 year postsurgery, respectively. Compared with the nonsurgical limb, the surgical limb showed decreased peak knee flexion angle at postrehabilitation and decreased knee extension moment at 1 year postsurgery. The hop symmetry index was positively associated with peak torque, RTD 0-200ms , and the KASE score at postrehabilitation. Moreover, at postrehabilitation, the peak knee flexion angle was

Association of Quadriceps Strength and Psychosocial Factors With Single-Leg Hop Performance in Patients With Meniscectomy

PubMed Central

Hsu, Chao-Jung; George, Steven Z.; Chmielewski, Terese L.

2016-01-01

Background: Clinicians use the single-leg hop test to assess readiness for return to sports after knee injury. Few studies have reported the results of single-leg hop testing after meniscectomy. Additionally, the contributions of impairments in quadriceps strength and psychosocial factors to single-leg hop performance are unknown. Purpose: To compare single-leg hop performance (distance and landing mechanics) between limbs and to examine the association of single-leg hop performance with quadriceps strength and psychosocial factors in patients with meniscectomy. Study Design: Descriptive laboratory study. Methods: A total of 22 subjects who underwent meniscectomy for traumatic meniscal tears received either standard rehabilitation alone or with additional quadriceps strengthening. Testing was conducted immediately postrehabilitation and at 1 year postsurgery. A single-leg hop test was performed bilaterally, and hop distance was used to create a hop symmetry index. Landing mechanics (peak knee flexion angle, knee extension moment, and peak vertical ground-reaction force) were analyzed with a motion-capture system and a force plate. An isokinetic dynamometer (60 deg/s) assessed knee extensor peak torque and rate of torque development (RTD0-200ms and RTD0–peak torque). Questionnaires assessed fear of reinjury (Tampa Scale for Kinesiophobia [TSK-11]) and self-efficacy (Knee Activity Self-Efficacy [KASE]). Results: Rehabilitation groups did not significantly differ in single-leg hop performance; therefore, groups were combined for further analyses. The mean hop symmetry index was 88.6% and 98.9% at postrehabilitation and 1 year postsurgery, respectively. Compared with the nonsurgical limb, the surgical limb showed decreased peak knee flexion angle at postrehabilitation and decreased knee extension moment at 1 year postsurgery. The hop symmetry index was positively associated with peak torque, RTD0-200ms, and the KASE score at postrehabilitation. Moreover, at

Knee joint laxity does not moderate the relationship between quadriceps strength and physical function in knee osteoarthritis patients: A cross-sectional study.

PubMed

Altubasi, Ibrahim M

2018-06-07

Knee osteoarthritis is a common and a disabling musculoskeletal disorder. Patients with knee osteoarthritis have activity limitations which are linked to the strength of the quadriceps muscle. Previous research reported that the relationship between quadriceps muscle strength and physical function is moderated by the level of knee joint frontal plane laxity. The purpose of the current study is to reexamine the moderation effect of the knee joint laxity as measured by stress radiographs on the relationship between quadriceps muscle strength and physical function. One-hundred and sixty osteoarthritis patients participated in this cross-sectional study. Isometric quadriceps muscle strength was measured using an isokinetic dynamometer. Self-rated and performance-based physical function were measured using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) physical function subscale and Get Up and Go test, respectively. Stress radiographs which were taken while applying varus and valgus loads to knee using the TELOS device. Knee joint laxity was determined by measuring the distance between joint surfaces on the medial and lateral sides. Hierarchical multiple regression models were constructed to study the moderation effect of laxity on the strength function relationship. Two regression models were constructed for self-rated and performance-based function. After controlling for demographics, strength contributed significantly in the models. The addition of laxity and laxity-strength interaction did not add significant contributions in the regression models. Frontal plane knee joint laxity measured by stress radiographs does not moderate the relationship between quadriceps muscle strength and physical function in patients with osteoarthritis. Copyright © 2018 Elsevier B.V. All rights reserved.

Growth on demand: Reviewing the mechanobiology of stretched skin

PubMed Central

Zöllner, Alexander M.; Holland, Maria A.; Honda, Kord S.; Gosain, Arun K.; Kuhl, Ellen

2013-01-01

Skin is a highly dynamic, autoregulated, living system that responds to mechanical stretch through a net gain in skin surface area. Tissue expansion uses the concept of controlled overstretch to grow extra skin for defect repair in situ. While the short-term mechanics of stretched skin have been studied intensely by testing explanted tissue samples ex vivo, we know very little about the long-term biomechanics and mechanobiology of living skin in vivo. redHere we explore the long-term effects of mechanical stretch on the characteristics of living skin using a mathematical model for skin growth. We review the molecular mechanisms by which skin responds to mechanical loading and model their effects collectively in a single scalar-valued internal variable, the surface area growth. redThis allows us to adopt a continuum model for growing skin based on the multiplicative decomposition of the deformation gradient into a reversible elastic and an irreversible growth part.redTo demonstrate the inherent modularity of this approach, we implement growth as a user-defined constitutive subroutine into the general purpose implicit finite element program Abaqus/Standard. To illustrate the features of the model, we simulate the controlled area growth of skin in response to tissue expansion with multiple filling points in time. Our results demonstrate that the field theories of continuum mechanics can reliably predict the manipulation of thin biological membranes through mechanical overstretch. Our model could serve as a valuable tool to rationalize clinical process parameters such as expander geometry, expander size, filling volume, filling pressure, and inflation timing to minimize tissue necrosis and maximize patient comfort in plastic and reconstructive surgery. While initially developed for growing skin, our model can easily be generalized to arbitrary biological structures to explore the physiology and pathology of stretch-induced growth of other living systems such as hearts

Immediate Effects of Proprioceptive Neuromuscular Facilitation Stretching Programs Compared With Passive Stretching Programs for Hamstring Flexibility: A Critically Appraised Topic.

PubMed

Hill, Kristian J; Robinson, Kendall P; Cuchna, Jennifer W; Hoch, Matthew C

2017-11-01

Clinical Scenario: Increasing hamstring flexibility through clinical stretching interventions may be an effective means to prevent hamstring injuries. However the most effective method to increase hamstring flexibility has yet to be determined. For a healthy individual, are proprioceptive neuromuscular facilitation (PNF) stretching programs more effective in immediately improving hamstring flexibility when compared with static stretching programs? Summary of Key Findings: A thorough literature search returned 195 possible studies; 5 studies met the inclusion criteria and were included. Current evidence supports the use of PNF stretching or static stretching programs for increasing hamstring flexibility. However, neither program demonstrated superior effectiveness when examining immediate increases in hamstring flexibility. Clinical Bottom Line: There were consistent findings from multiple low-quality studies that indicate there is no difference in the immediate improvements in hamstring flexibility when comparing PNF stretching programs to static stretching programs in physically active adults. Strength of Recommendation: Grade B evidence exists that PNF and static stretching programs equally increase hamstring flexibility immediately following the stretching program.

Low Latency Messages on Distributed Memory Multiprocessors

DOE PAGES

Rosing, Matt; Saltz, Joel

1995-01-01

This article describes many of the issues in developing an efficient interface for communication on distributed memory machines. Although the hardware component of message latency is less than 1 ws on many distributed memory machines, the software latency associated with sending and receiving typed messages is on the order of 50 μs. The reason for this imbalance is that the software interface does not match the hardware. By changing the interface to match the hardware more closely, applications with fine grained communication can be put on these machines. This article describes several tests performed and many of the issues involvedmore » in supporting low latency messages on distributed memory machines.« less

Stretch Band Exercise Program

ERIC Educational Resources Information Center

Skirka, Nicholas; Hume, Donald

2007-01-01

This article discusses how to use stretch bands for improving total body fitness and quality of life. A stretch band exercise program offers a versatile and inexpensive option to motivate participants to exercise. The authors suggest practical exercises that can be used in physical education to improve or maintain muscular strength and endurance,…

Passive stretch reduces calpain activity through nitric oxide pathway in unloaded soleus muscles.

PubMed

Xu, Peng-Tao; Li, Quan; Sheng, Juan-Juan; Chang, Hui; Song, Zhen; Yu, Zhi-Bin

2012-08-01

Unloading in spaceflight or long-term bed rest induces to pronounced atrophy of anti-gravity skeletal muscles. Passive stretch partially resists unloading-induced atrophy of skeletal muscle, but the mechanism remains elusive. The aims of this study were to investigate the hypotheses that stretch tension might increase protein level of neuronal nitric oxide synthase (nNOS) in unloaded skeletal muscle, and then nNOS-derived NO alleviated atrophy of skeletal muscle by inhibiting calpain activity. The tail-suspended rats were used to unload rat hindlimbs for 2 weeks, at the same time, left soleus muscle was stretched by applying a plaster cast to fix the ankle at 35° dorsiflexion. Stretch partially resisted atrophy and inhibited the decreased protein level and activity of nNOS in unloaded soleus muscles. Unloading increased frequency of calcium sparks and elevated intracellular resting and caffeine-induced Ca(2+) concentration ([Ca(2+)]i) in unloaded soleus muscle fibers. Stretch reduced frequency of calcium sparks and restored intracellular resting and caffeine-induced Ca(2+) concentration to control levels in unloaded soleus muscle fibers. The increased protein level and activity of calpain as well as the higher degradation of desmin induced by unloading were inhibited by stretch in soleus muscles. In conclusion, these results suggest that stretch can preserve the stability of sarcoplasmic reticulum Ca(2+) release channels which prevents the elevated [Ca(2+)]i by means of keeping nNOS activity, and then the enhanced protein level and activity of calpain return to control levels in unloaded soleus muscles. Therefore, stretch can resist in part atrophy of unloaded soleus muscles.

Latency and User Performance in Virtual Environments and Augmented Reality

NASA Technical Reports Server (NTRS)

Ellis, Stephen R.

2009-01-01

System rendering latency has been recognized by senior researchers, such as Professor Fredrick Brooks of UNC (Turing Award 1999), as a major factor limiting the realism and utility of head-referenced displays systems. Latency has been shown to reduce the user's sense of immersion within a virtual environment, disturb user interaction with virtual objects, and to contribute to motion sickness during some simulation tasks. Latency, however, is not just an issue for external display systems since finite nerve conduction rates and variation in transduction times in the human body's sensors also pose problems for latency management within the nervous system. Some of the phenomena arising from the brain's handling of sensory asynchrony due to latency will be discussed as a prelude to consideration of the effects of latency in interactive displays. The causes and consequences of the erroneous movement that appears in displays due to latency will be illustrated with examples of the user performance impact provided by several experiments. These experiments will review the generality of user sensitivity to latency when users judge either object or environment stability. Hardware and signal processing countermeasures will also be discussed. In particular the tuning of a simple extrapolative predictive filter not using a dynamic movement model will be presented. Results show that it is possible to adjust this filter so that the appearance of some latencies may be hidden without the introduction of perceptual artifacts such as overshoot. Several examples of the effects of user performance will be illustrated by three-dimensional tracking and tracing tasks executed in virtual environments. These experiments demonstrate classic phenomena known from work on manual control and show the need for very responsive systems if they are indented to support precise manipulation. The practical benefits of removing interfering latencies from interactive systems will be emphasized with some

Mechanisms of quadriceps muscle weakness in knee joint osteoarthritis: the effects of prolonged vibration on torque and muscle activation in osteoarthritic and healthy control subjects.

PubMed

Rice, David A; McNair, Peter J; Lewis, Gwyn N

2011-01-01

A consequence of knee joint osteoarthritis (OA) is an inability to fully activate the quadriceps muscles, a problem termed arthrogenic muscle inhibition (AMI). AMI leads to marked quadriceps weakness that impairs physical function and may hasten disease progression. The purpose of the present study was to determine whether γ-loop dysfunction contributes to AMI in people with knee joint OA. Fifteen subjects with knee joint OA and 15 controls with no history of knee joint pathology participated in this study. Quadriceps and hamstrings peak isometric torque (Nm) and electromyography (EMG) amplitude were collected before and after 20 minutes of 50 Hz vibration applied to the infrapatellar tendon. Between-group differences in pre-vibration torque were analysed using a one-way analysis of covariance, with age, gender and body mass (kg) as the covariates. If the γ-loop is intact, vibration should decrease torque and EMG levels in the target muscle; if dysfunctional, then torque and EMG levels should not change following vibration. One-sample t tests were thus undertaken to analyse whether percentage changes in torque and EMG differed from zero after vibration in each group. In addition, analyses of covariance were utilised to analyse between-group differences in the percentage changes in torque and EMG following vibration. Pre-vibration quadriceps torque was significantly lower in the OA group compared with the control group (P = 0.005). Following tendon vibration, quadriceps torque (P < 0.001) and EMG amplitude (P ≤0.001) decreased significantly in the control group but did not change in the OA group (all P > 0.299). Hamstrings torque and EMG amplitude were unchanged in both groups (all P > 0.204). The vibration-induced changes in quadriceps torque and EMG were significantly different between the OA and control groups (all P < 0.011). No between-group differences were observed for the change in hamstrings torque or EMG (all P > 0.554). γ-loop dysfunction may

Amount of torque and duration of stretching affects correction of knee contracture in a rat model of spinal cord injury.

PubMed

Moriyama, Hideki; Tobimatsu, Yoshiko; Ozawa, Junya; Kito, Nobuhiro; Tanaka, Ryo

2013-11-01

Joint contractures are a common complication of many neurologic conditions, and stretching often is advocated to prevent and treat these contractures. However, the magnitude and duration of the stretching done in practice usually are guided by subjective clinical impressions. Using an established T8 spinal cord injury rat model of knee contracture, we sought to determine what combination of static or intermittent stretching, varied by magnitude (high or low) and duration (long or short), leads to the best (1) improvement in the limitation in ROM; (2) restoration of the muscular and articular factors leading to contractures; and (3) prevention and treatment of contracture-associated histologic alterations of joint capsule and articular cartilage. Using a rat animal model, the spinal cord was transected completely at the level of T8. The rats were randomly assigned to seven treatment groups (n = 4 per group), which were composed of static or intermittent stretching in combination with different amounts of applied torque magnitude and duration. We assessed the effect of stretching by measuring the ROM and evaluating the histologic alteration of the capsule and cartilage. Contractures improved in all treated groups except for the low-torque and short-duration static stretching conditions. High-torque stretching was effective against shortening of the synovial membrane and adhesions in the posterosuperior regions. Collagen Type II and VEGF in the cartilage were increased by stretching. High-torque and long-duration static stretching led to greater restoration of ROM than the other torque and duration treatment groups. Stretching was more effective in improving articular components of contractures compared with the muscular components. Stretching in this rat model prevented shortening and adhesion of the joint capsule, and affected biochemical composition, but did not change morphologic features of the cartilage. This animal study tends to support the ideas that static

Surgical Treatment for Failure of Repair of Patellar and Quadriceps Tendon Rupture With Ipsilateral Hamstring Tendon Graft.

PubMed

Maffulli, Nicola; Papalia, Rocco; Torre, Guglielmo; Denaro, Vincenzo

2017-03-01

Tears of the patellar and quadriceps tendon are common in the active population, especially in athletes. At present, several techniques for surgical repair and reconstruction are available. When reruptures occur, a reconstruction is mandatory. In the present paper, we describe a surgical technique for patellar and quadriceps tendon reconstruction using ipsilateral hamstring autograft. After routine hamstring tendon harvesting, the tendon ends are prepared using a whip stitch. A transverse tunnel is drilled in the midportion of the patella, the hamstring graft is passed through the patella, and firmly secured to the patellar tunnel openings with sutures. The details of the technique are fully described. Autologous ipsilateral hamstring tendon grafts provide a secure sound means to manage these challenging injuries.

The long non-coding HOTAIR is modulated by cyclic stretch and WNT/β-CATENIN in human aortic valve cells and is a novel repressor of calcification genes.

PubMed

Carrion, Katrina; Dyo, Jeffrey; Patel, Vishal; Sasik, Roman; Mohamed, Salah A; Hardiman, Gary; Nigam, Vishal

2014-01-01

Aortic valve calcification is a significant and serious clinical problem for which there are no effective medical treatments. Individuals born with bicuspid aortic valves, 1-2% of the population, are at the highest risk of developing aortic valve calcification. Aortic valve calcification involves increased expression of calcification and inflammatory genes. Bicuspid aortic valve leaflets experience increased biomechanical strain as compared to normal tricuspid aortic valves. The molecular pathogenesis involved in the calcification of BAVs are not well understood, especially the molecular response to mechanical stretch. HOTAIR is a long non-coding RNA (lncRNA) that has been implicated with cancer but has not been studied in cardiac disease. We have found that HOTAIR levels are decreased in BAVs and in human aortic interstitial cells (AVICs) exposed to cyclic stretch. Reducing HOTAIR levels via siRNA in AVICs results in increased expression of calcification genes. Our data suggest that β-catenin is a stretch responsive signaling pathway that represses HOTAIR. This is the first report demonstrating that HOTAIR is mechanoresponsive and repressed by WNT β-catenin signaling. These findings provide novel evidence that HOTAIR is involved in aortic valve calcification.

Relationship between quadriceps strength and rate of loading during gait in women.

PubMed

Mikesky, A E; Meyer, A; Thompson, K L

2000-03-01

One function of skeletal muscle is to serve as the body's shock absorbers and thus dampen rates of loading during activity. The aim of this cross-sectional study was to determine the significance of muscle strength on rates of loading during gait. Thirty-seven women (mean age: 34.5 +/- 8.2 years) were solicited by advertisement and placed into one of two groups-strength-trained or sedentary-on the basis of training history. They walked (10 trials) over a 10-m walkway at a controlled speed of 1.22-1.35 m/s while the rate of loading was sampled with a 1,000-Hz force platform. Quadriceps and hamstring strength was measured at 90 degrees/s with an isokinetic dynamometer. Statistical analyses (p < 0.05) included descriptive statistics and unpaired t tests for comparison between groups. The women in the sedentary group weighed more and had significantly less concentric and eccentric strength of the quadriceps and hamstrings relative to body weight than did those in the strength-trained group. In addition, they demonstrated significantly higher rates of loading (2.21 +/- 0.15 compared with 1.75 +/- 0.08%wt/ms) than those in the strength-trained group.

Effect of exercise-induced arterial hypoxemia on quadriceps muscle fatigue in healthy humans.

PubMed

Romer, Lee M; Haverkamp, Hans C; Lovering, Andrew T; Pegelow, David F; Dempsey, Jerome A

2006-02-01

The effect of exercise-induced arterial hypoxemia (EIAH) on quadriceps muscle fatigue was assessed in 11 male endurance-trained subjects [peak O2 uptake (VO2 peak) = 56.4 +/- 2.8 ml x kg(-1) x min(-1); mean +/- SE]. Subjects exercised on a cycle ergometer at >or=90% VO2 peak) to exhaustion (13.2 +/- 0.8 min), during which time arterial O2 saturation (Sa(O2)) fell from 97.7 +/- 0.1% at rest to 91.9 +/- 0.9% (range 84-94%) at end exercise, primarily because of changes in blood pH (7.183 +/- 0.017) and body temperature (38.9 +/- 0.2 degrees C). On a separate occasion, subjects repeated the exercise, for the same duration and at the same power output as before, but breathed gas mixtures [inspired O2 fraction (Fi(O2)) = 0.25-0.31] that prevented EIAH (Sa(O2) = 97-99%). Quadriceps muscle fatigue was assessed via supramaximal paired magnetic stimuli of the femoral nerve (1-100 Hz). Immediately after exercise at Fi(O2) 0.21, the mean force response across 1-100 Hz decreased 33 +/- 5% compared with only 15 +/- 5% when EIAH was prevented (P < 0.05). In a subgroup of four less fit subjects, who showed minimal EIAH at Fi(O2) 0.21 (Sa(O2) = 95.3 +/- 0.7%), the decrease in evoked force was exacerbated by 35% (P < 0.05) in response to further desaturation induced via Fi(O2) 0.17 (Sa(O2) = 87.8 +/- 0.5%) for the same duration and intensity of exercise. We conclude that the arterial O2 desaturation that occurs in fit subjects during high-intensity exercise in normoxia (-6 +/- 1% DeltaSa(O2) from rest) contributes significantly toward quadriceps muscle fatigue via a peripheral mechanism.

Static postural sway, proprioception, and maximal voluntary quadriceps contraction in patients with knee osteoarthritis and normal control subjects

PubMed Central

Hassan, B; Mockett, S; Doherty, M

2001-01-01

OBJECTIVES—To investigate whether subjects with knee osteoarthritis (OA) have reduced static postural control, knee proprioceptive acuity, and maximal voluntary contraction (MVC) of the quadriceps compared with normal controls, and to determine possible independent predictors of static postural sway.
METHODS—77 subjects with symptomatic and radiographic knee OA (58 women, 19 men; mean age 63.4 years, range 36-82) and 63 controls with asymptomatic and clinically normal knees (45 women, 18 men; mean age 63 years, range 46-85) underwent assessment of static postural sway. 108 subjects (59 patients, 49 controls) also underwent assessment of knee proprioceptive activity and MVC (including calculation of quadriceps activation). In patients with knee OA knee pain, stiffness, and functional disability were assessed using the WOMAC Index. The height (m) and weight (kg) of all subjects was assessed.
RESULTS—Compared with controls, patients with knee OA were heavier (mean difference 15.3 kg, p<0.001), had increased postural lateral sway (controls: median 2.3, interquartile (IQ) range 1.8-2.9; patients: median 4.7, IQ range 1.9-4.7, p<0.001), reduced proprioceptive acuity (controls: mean 7.9, 95% CI 6.9 to 8.9; patients: mean 12.0, 95% CI 10.5 to 13.6, p<0.001), weaker quadriceps strength (controls: mean 22.5, 95% CI 19.9 to 24.6; patients: mean 14.7, 95% CI 12.5 to 16.9, p<0.001), and less percentage activation of quadriceps (controls: mean 87.4, 95% CI 80.7 to 94.2; patients: mean 66.0, 95% CI 58.8 to 73.2, p<0.001). The significant predictors of postural sway were knee pain and the ratio of MVC/body weight.
CONCLUSIONS—Compared with age and sex matched controls, subjects with symptomatic knee OA have quadriceps weakness, reduced knee proprioception, and increased postural sway. Pain and muscle strength may particularly influence postural sway. The interaction between physiological, structural, and functional abnormalities in knee OA

The quadriceps muscle of knee joint modelling Using Hybrid Particle Swarm Optimization-Neural Network (PSO-NN)

NASA Astrophysics Data System (ADS)

Kamaruddin, Saadi Bin Ahmad; Marponga Tolos, Siti; Hee, Pah Chin; Ghani, Nor Azura Md; Ramli, Norazan Mohamed; Nasir, Noorhamizah Binti Mohamed; Ksm Kader, Babul Salam Bin; Saiful Huq, Mohammad

2017-03-01

Neural framework has for quite a while been known for its ability to handle a complex nonlinear system without a logical model and can learn refined nonlinear associations gives. Theoretically, the most surely understood computation to set up the framework is the backpropagation (BP) count which relies on upon the minimization of the mean square error (MSE). However, this algorithm is not totally efficient in the presence of outliers which usually exist in dynamic data. This paper exhibits the modelling of quadriceps muscle model by utilizing counterfeit smart procedures named consolidated backpropagation neural network nonlinear autoregressive (BPNN-NAR) and backpropagation neural network nonlinear autoregressive moving average (BPNN-NARMA) models in view of utilitarian electrical incitement (FES). We adapted particle swarm optimization (PSO) approach to enhance the performance of backpropagation algorithm. In this research, a progression of tests utilizing FES was led. The information that is gotten is utilized to build up the quadriceps muscle model. 934 preparing information, 200 testing and 200 approval information set are utilized as a part of the improvement of muscle model. It was found that both BPNN-NAR and BPNN-NARMA performed well in modelling this type of data. As a conclusion, the neural network time series models performed reasonably efficient for non-linear modelling such as active properties of the quadriceps muscle with one input, namely output namely muscle force.

Endovascular rescue method for undesirably stretched coil.

PubMed

Cho, Jae Hoon

2014-10-01

Undesirable detachment or stretching of coils within the parent artery during aneurysm embolization can be related with thrombus formation, which can be caused occlusion of parent artery or embolic event(s). To escape from this situation, several rescue methods have been reported. A case with undesirably stretched coil in which another rescue method was used, is presented. When the stretched coil is still located in the coil delivery microcatheter, the stretched coil can be removed safely using a snare and a handmade monorail microcatheter. After a snare is lodged in the handmade monorail microcatheter, the snare is introduced over the coil delivery micorcatheter and located in the distal part of the stretched coil. After then, the handmade monorail microcatheter captures the stretched coil and the snare as one unit. This technique using a handmade monorail microcatheter and a snare can be a good rescue modality for the undesirably stretched coil, still remained within the coil delivery microcatheter.

Endovascular Rescue Method for Undesirably Stretched Coil

PubMed Central

2014-01-01

Undesirable detachment or stretching of coils within the parent artery during aneurysm embolization can be related with thrombus formation, which can be caused occlusion of parent artery or embolic event(s). To escape from this situation, several rescue methods have been reported. A case with undesirably stretched coil in which another rescue method was used, is presented. When the stretched coil is still located in the coil delivery microcatheter, the stretched coil can be removed safely using a snare and a handmade monorail microcatheter. After a snare is lodged in the handmade monorail microcatheter, the snare is introduced over the coil delivery micorcatheter and located in the distal part of the stretched coil. After then, the handmade monorail microcatheter captures the stretched coil and the snare as one unit. This technique using a handmade monorail microcatheter and a snare can be a good rescue modality for the undesirably stretched coil, still remained within the coil delivery microcatheter. PMID:25371791

A randomized controlled trial for the effect of passive stretching on measures of hamstring extensibility, passive stiffness, strength, and stretch tolerance.

PubMed

Marshall, Paul W M; Cashman, Anthony; Cheema, Birinder S

2011-11-01

To measure hamstring extensibility, stiffness, stretch tolerance, and strength following a 4-week passive stretching program. Randomized controlled trial. Twenty-two healthy participants were randomly assigned to either a 4-week stretching program consisting of 4 hamstring and hip stretches performed 5 times per week, or a non-stretching control group. Hamstring extensibility and stiffness were measured before and after training using the instrumented straight leg raise test (iSLR). Stretch tolerance was measured as the pain intensity (visual analog scale; VAS) elicited during the maximal stretch. Hamstring strength was measured using isokinetic dynamometry at 30 and 120° s(-1). Hamstring extensibility increased by 20.9% in the intervention group following 4 weeks of training (p<0.001; d=0.86). Passive stiffness was reduced by 31% in the intervention group (p<0.05; d=-0.89). Stretch tolerance VAS scores were not different between groups at either time point, and no changes were observed following training. There were no changes in hamstring concentric strength measured at 30 and 120° s(-1). Passive stretching increases hamstring extensibility and decreases passive stiffness, with no change in stretch tolerance defined by pain intensity during the stretch. Compared to previous research, the volume of stretching was higher in this study. The volume of prescribed stretching is important for eliciting the strong clinical effect observed in this study. Copyright © 2011 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

The effects of joint aspiration and intra-articular corticosteroid injection on flexion reflex excitability, quadriceps strength and pain in individuals with knee synovitis: a prospective observational study.

PubMed

Rice, David Andrew; McNair, Peter John; Lewis, Gwyn Nancy; Dalbeth, Nicola

2015-07-28

Substantial weakness of the quadriceps muscles is typically observed in patients with arthritis. This is partly due to ongoing neural inhibition that prevents the quadriceps from being fully activated. Evidence from animal studies suggests enhanced flexion reflex excitability may contribute to this weakness. This prospective observational study examined the effects of joint aspiration and intra-articular corticosteroid injection on flexion reflex excitability, quadriceps muscle strength and knee pain in individuals with knee synovitis. Sixteen patients with chronic arthritis and clinically active synovitis of the knee participated in this study. Knee pain flexion reflex threshold, and quadriceps peak torque were measured at baseline, immediately after knee joint aspiration alone and 5 ± 2 and 15 ± 2 days after knee joint aspiration and the injection of 40 mg of methylprednisolone acetate. Compared to baseline, knee pain was significantly reduced 5 (p = 0.001) and 15 days (p = 0.009) post intervention. Flexion reflex threshold increased immediately after joint aspiration (p = 0.009) and 5 (p = 0.01) and 15 days (p = 0.002) post intervention. Quadriceps peak torque increased immediately after joint aspiration (p = 0.004) and 5 (p = 0.001) and 15 days (p <0.001) post intervention. The findings from this study suggest that altered sensory output from an inflamed joint may increase flexion reflex excitability in humans, as has previously been shown in animals. Joint aspiration and corticosteroid injection may be a clinically useful intervention to reverse quadriceps muscle weakness in individuals with knee synovitis.

MicroRNA-155 Reinforces HIV Latency*

PubMed Central

Ruelas, Debbie S.; Chan, Jonathan K.; Oh, Eugene; Heidersbach, Amy J.; Hebbeler, Andrew M.; Chavez, Leonard; Verdin, Eric; Rape, Michael; Greene, Warner C.

2015-01-01

The presence of a small number of infected but transcriptionally dormant cells currently thwarts a cure for the more than 35 million individuals infected with HIV. Reactivation of these latently infected cells may result in three fates: 1) cell death due to a viral cytopathic effect, 2) cell death due to immune clearance, or 3) a retreat into latency. Uncovering the dynamics of HIV gene expression and silencing in the latent reservoir will be crucial for developing an HIV-1 cure. Here we identify and characterize an intracellular circuit involving TRIM32, an HIV activator, and miR-155, a microRNA that may promote a return to latency in these transiently activated reservoir cells. Notably, we demonstrate that TRIM32, an E3 ubiquitin ligase, promotes reactivation from latency by directly modifying IκBα, leading to a novel mechanism of NF-κB induction not involving IκB kinase activation. PMID:25873391

Effects of combined application of progressive resistance training and Russian electrical stimulation on quadriceps femoris muscle strength in elderly women with knee osteoarthritis.

PubMed

Park, Seong Hoon; Hwangbo, Gak

2015-03-01

[Purpose] The aim of this study was to investigate the effects of combined application of progressive resistance training and Russian electrical stimulation on quadriceps femoris muscle strength in elderly women with osteoarthritis of the knee. [Subjects] Thirty women over 65 years of age diagnosed with knee osteoarthritis participated in the present study. The subjects were randomly assigned to a control group (n=10), a progressive resistance training group (n=10), or a Russian electrical stimulation group (n=10). [Methods] Each group was treated 3 times weekly for 8 weeks, and each session lasted 45 minutes. Muscle strength was assessed by measuring the peak torque of the quadriceps femoris muscle. Outcome measurements were performed at baseline and at the fourth and eighth weeks of the treatment period. [Results] All groups showed significant intragroup differences in the quadriceps femoris muscle peak torque after the treatment intervention. There were significant intergroup differences between the Russian electrical stimulation group and the other groups. [Conclusion] The results of this study suggest that combined application of progressive resistance training and Russian electrical stimulation can be effective in strengthening the quadriceps femoris muscle in elderly women with knee osteoarthritis.

Transient photoresponse in amorphous In-Ga-Zn-O thin films under stretched exponential analysis

NASA Astrophysics Data System (ADS)

Luo, Jiajun; Adler, Alexander U.; Mason, Thomas O.; Bruce Buchholz, D.; Chang, R. P. H.; Grayson, M.

2013-04-01

We investigated transient photoresponse and Hall effect in amorphous In-Ga-Zn-O thin films and observed a stretched exponential response which allows characterization of the activation energy spectrum with only three fit parameters. Measurements of as-grown films and 350 K annealed films were conducted at room temperature by recording conductivity, carrier density, and mobility over day-long time scales, both under illumination and in the dark. Hall measurements verify approximately constant mobility, even as the photoinduced carrier density changes by orders of magnitude. The transient photoconductivity data fit well to a stretched exponential during both illumination and dark relaxation, but with slower response in the dark. The inverse Laplace transforms of these stretched exponentials yield the density of activation energies responsible for transient photoconductivity. An empirical equation is introduced, which determines the linewidth of the activation energy band from the stretched exponential parameter β. Dry annealing at 350 K is observed to slow the transient photoresponse.

Ultra-high-speed optical coherence tomography with a stretched pulse supercontinuum source.

PubMed

Moon, Sucbei; Kim, Dug Young

2006-11-27

We introduce a new high-speed Fourier-domain optical coherence tomography (FD-OCT) scheme based on a stretched pulse supercontinuum source. A wide-band short pulse of a supercontinuum source of which output spectrum spanned a wavelength range from 1,200 nm to 1,550 nm was stretched to a long pulse of 70-ns duration by using a dispersive fiber due to the group-velocity dispersion, and it was used directly as frequency-swept light for FD-OCT. The OCT spectral interferogram was acquired in the time domain and converted into the spectral domain by the pre-calibrated time-to-wavelength relation. Using this stretched-pulse OCT (SP-OCT) scheme, we have demonstrated an ultrahigh-speed axial-line scanning rate of 5 MHz. The axial resolution of 8 microm was achieved without re-calibration of the sweep characteristic owing to the passive nature of the frequency-sweeping mechanism.

Pursuit Latency for Chromatic Targets

NASA Technical Reports Server (NTRS)

Mulligan, Jeffrey B.; Ellis, Stephen R. (Technical Monitor)

1998-01-01

The temporal dynamics of eye movement response to a change in direction of stimulus motion has been used to compare the processing speeds of different types of stimuli (Mulligan, ARVO '97). In this study, the pursuit response to colored targets was measured to test the hypothesis that the slow response of the chromatic system (as measured using traditional temporal sensitivity measures such as contrast sensitivity) results in increased eye movement latencies. Subjects viewed a small (0.4 deg) Gaussian spot which moved downward at a speed of 6.6 deg/sec. At a variable time during the trajectory, the dot's direction of motion changed by 30 degrees, either to the right or left. Subjects were instructed to pursue the spot. Eye movements were measured using a video ophthalmoscope with an angular resolution of approximately 1 arc min and a temporal sampling rate of 60 Hz. Stimuli were modulated in chrominance for a variety of hue directions, combined with a range of small luminance increments and decrements, to insure that some of the stimuli fell in the subjects' equiluminance planes. The smooth portions of the resulting eye movement traces were fit by convolving the stimulus velocity with an exponential having variable onset latency, time constant and amplitude. Smooth eye movements with few saccades were observed for all stimuli. Pursuit responses to stimuli having a significant luminance component are well-fit by exponentials having latencies and time constants on the order of 100 msec. Increases in pursuit response latency on the order of 100-200 msec are observed in response to certain stimuli, which occur in pairs of complementary hues, corresponding to the intersection of the stimulus section with the subjects' equiluminant plane. Smooth eye movements can be made in response to purely chromatic stimuli, but are slower than responses to stimuli with a luminance component.

Stretch Reflex as a Simple Measure to Evaluate the Efficacy of Potential Flight Countermeasures Using the Bed Rest Environment

NASA Technical Reports Server (NTRS)

Cerisano, J. M.; Reschke, M. F.; Kofman, I. S.; Fisher, E. A.; Harm, D. L.

2010-01-01

INTRODUCTION: Spaceflight is acknowledged to have significant effects on the major postural muscles. However, it has been difficult to separate the effects of ascending somatosensory changes caused by the unloading of these muscles during flight from changes in sensorimotor function caused by a descending vestibulo-cerebellar response to microgravity. It is hypothesized that bed rest is an adequate model to investigate postural muscle unloading given that spaceflight and bed rest may produce similar results in both nerve axon and muscle tissue. METHODS: To investigate this hypothesis, stretch reflexes were measured on 18 subjects who spent 60 to 90 days in continuous 6 head-down bed rest. Using a motorized system capable of rotating the foot around the ankle joint (dorsiflexion) through an angle of 10 deg at a peak velocity of approximately 250 deg/sec, a stretch reflex was recorded from the subject's left triceps surae muscle group. Using surface electromyography, about 300 reflex responses were obtained and ensemble-averaged on 3 separate days before bed rest, 3 to 4 times in bed, and 3 times after bed rest. The averaged responses for each test day were examined for reflex latency and conduction velocity (CV) across gender and compared with spaceflight data. RESULTS: Although no gender differences were found, bed rest induced changes in reflex latency and CV similar to the ones observed during spaceflight. Also, a relationship between CV and loss of muscle strength in the lower leg was observed for most bed rest subjects. CONCLUSION: Even though bed rest (limb unloading) alone may not mimic all of the synaptic and muscle tissue loss that is observed as a result of spaceflight, it can serve as a working analog of flight for the evaluation of potential countermeasures that may be beneficial in mitigating unwanted changes in the major postural muscles that are observed post flight.

Muscle oxygenation and fascicle length during passive muscle stretching in ballet-trained subjects.

PubMed

Otsuki, A; Fujita, E; Ikegawa, S; Kuno-Mizumura, M

2011-07-01

Muscle stretching transiently decreases muscle-blood flow corresponding to a muscle extension. It may disturb a balance between muscular oxygen demand and oxygen supply to muscles and reduce muscle oxygenation. However, muscle-stretching training may improve blood circulatory condition, resulting in the maintained muscle oxygenation during muscle stretching. The aim of this study was to investigate changes in muscle-blood volume (tHb) and tissue oxygenation index (TOI) during muscle stretching determined by using near-infrared spectroscopy (NIRS) in ballet-trained (BT) and untrained (C) subjects. 11 BT women who regularly perform muscle stretching and 11 C women participated in this study. Fascicle lengths, tHb and TOI in the tibialis anterior muscle were measured during passive plantar flexion from ankle joint angles of 120° (baseline) to 140°, 160°, the maximal comfortable position without pain (CP), and the maximal position (MP). At 160°, the % fascicle-length change from baseline was significantly lower in the BT than the C group, however, for the changes in tHb and TOI the significant interaction effect between the 2 groups was not detected. On the other hand, although the increases in the fascicle length from baseline to CP and MP were greater in BT than C, the tHb and TOI reductions were comparable between groups. We concluded that it appears that BT can extend their muscles without excessive reduction in muscle-blood volume and muscle oxygenation at relatively same but absolutely greater muscle-stretching levels than C. The attenuation in these indices during high-level muscle stretching may be associated with the repetitive muscle stretching of long-term ballet training. © Georg Thieme Verlag KG Stuttgart · New York.

Avoiding and tolerating latency in large-scale next-generation shared-memory multiprocessors

NASA Technical Reports Server (NTRS)

Probst, David K.

1993-01-01

A scalable solution to the memory-latency problem is necessary to prevent the large latencies of synchronization and memory operations inherent in large-scale shared-memory multiprocessors from reducing high performance. We distinguish latency avoidance and latency tolerance. Latency is avoided when data is brought to nearby locales for future reference. Latency is tolerated when references are overlapped with other computation. Latency-avoiding locales include: processor registers, data caches used temporally, and nearby memory modules. Tolerating communication latency requires parallelism, allowing the overlap of communication and computation. Latency-tolerating techniques include: vector pipelining, data caches used spatially, prefetching in various forms, and multithreading in various forms. Relaxing the consistency model permits increased use of avoidance and tolerance techniques. Each model is a mapping from the program text to sets of partial orders on program operations; it is a convention about which temporal precedences among program operations are necessary. Information about temporal locality and parallelism constrains the use of avoidance and tolerance techniques. Suitable architectural primitives and compiler technology are required to exploit the increased freedom to reorder and overlap operations in relaxed models.

Anisotropic instability of a stretching film

NASA Astrophysics Data System (ADS)

Xu, Bingrui; Li, Minhao; Deng, Daosheng

2017-11-01

Instability of a thin liquid film, such as dewetting arising from Van der Waals force, has been well studied, and is typically characterized by formation of many droplets. Interestingly, a thin liquid film subjected to an applied stretching during a process of thermal drawing is evolved into an array of filaments, i.e., continuity is preserved along the direction of stretching while breakup occurs exclusively in the plane of cross section. Here, to understand this anisotropic instability, we build a physical model by considering both Van der Waals force and the effect of stretching. By using the linear instability analysis method and then performing a numerical calculation, we find that the growth rate of perturbations at the cross section is larger than that along the direction of stretching, resulting in the anisotropic instability of the stretching film. These results may provide theoretical guidance to achieve more diverse structures for nanotechnology.

Impact of pain reported during isometric quadriceps muscle strength testing in people with knee pain: data from the osteoarthritis initiative.

PubMed

Riddle, Daniel L; Stratford, Paul W

2011-10-01

Muscle force testing is one of the more common categories of diagnostic tests used in clinical practice. Clinicians have little evidence to guide interpretations of muscle force tests when pain is elicited during testing. The purpose of this study was to examine the construct validity of isometric quadriceps muscle strength tests by determining whether the relationship between maximal isometric quadriceps muscle strength and functional status was influenced by pain during isometric testing. A cross-sectional design was used. Data from the Osteoarthritis Initiative were used to identify 1,344 people with unilateral knee pain and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain subscale scores of 1 or higher on the involved side. Measurements of maximal isometric quadriceps strength and ratings of pain during isometric testing were collected. Outcome variables were WOMAC physical function subscale, 20-m walk test, 400-m walk test, and a repeated chair stand test. Multiple regression models were used to determine whether pain during testing modified or confounded the relationship between strength and functional status. Pearson r correlations among the isometric quadriceps strength measures and the 4 outcome measures ranged from -.36 (95% confidence interval=-.41, -.31) for repeated chair stands to .36 (95% confidence interval=.31, .41) for the 20-m walk test. In the final analyses, neither effect modification nor confounding was found for the repeated chair stand test, the 20-m walk test, the 400-m walk test, or the WOMAC physical function subscale. Moderate or severe pain during testing was weakly associated with reduced strength, but mild pain was not. The disease spectrum was skewed toward mild or moderate symptoms, and the pain measurement scale used during muscle force testing was not ideal. Given that the spectrum of the sample was skewed toward mild or moderate symptoms and disease, the data suggest that isometric quadriceps muscle

Impact of Pain Reported During Isometric Quadriceps Muscle Strength Testing in People With Knee Pain: Data From the Osteoarthritis Initiative

PubMed Central

Stratford, Paul W.

2011-01-01

Background Muscle force testing is one of the more common categories of diagnostic tests used in clinical practice. Clinicians have little evidence to guide interpretations of muscle force tests when pain is elicited during testing. Objective The purpose of this study was to examine the construct validity of isometric quadriceps muscle strength tests by determining whether the relationship between maximal isometric quadriceps muscle strength and functional status was influenced by pain during isometric testing. Design A cross-sectional design was used. Methods Data from the Osteoarthritis Initiative were used to identify 1,344 people with unilateral knee pain and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain subscale scores of 1 or higher on the involved side. Measurements of maximal isometric quadriceps strength and ratings of pain during isometric testing were collected. Outcome variables were WOMAC physical function subscale, 20-m walk test, 400-m walk test, and a repeated chair stand test. Multiple regression models were used to determine whether pain during testing modified or confounded the relationship between strength and functional status. Results Pearson r correlations among the isometric quadriceps strength measures and the 4 outcome measures ranged from −.36 (95% confidence interval=−.41, −.31) for repeated chair stands to .36 (95% confidence interval=.31, .41) for the 20-m walk test. In the final analyses, neither effect modification nor confounding was found for the repeated chair stand test, the 20-m walk test, the 400-m walk test, or the WOMAC physical function subscale. Moderate or severe pain during testing was weakly associated with reduced strength, but mild pain was not. Limitations The disease spectrum was skewed toward mild or moderate symptoms, and the pain measurement scale used during muscle force testing was not ideal. Conclusions Given that the spectrum of the sample was skewed toward mild or moderate

Manipulation of sensory input can improve stretching outcomes.

PubMed

Capobianco, Robyn A; Almuklass, Awad M; Enoka, Roger M

2018-02-01

The primary purpose of our study was to assess the influence of modulating sensory input with either transcutaneous electrical nerve stimulation (TENS) or self-massage with therapy balls on the maximal range of motion (ROM) about the ankle joint when stretching the calf muscles. We also investigated the influence of these two conditions on the force capacity and force control of plantar flexor muscles. Twenty healthy adults (25 ± 3 yr) performed three sessions of ankle plantar flexor stretching (three stretches of 30 s each): stretching alone (SS), stretching with concurrent TENS (TENS), and stretching after self-massage using therapy balls (SM). TENS was applied for 60 s prior to and during each stretch, and SM was performed for 60 s prior to each of the three stretches. Maximal voluntary contraction (MVC) torque and force steadiness at 20% MVC were recorded before and at 15 min after the final stretch. Ankle dorsiflexion ROM was assessed before, after, and at 5, 10, and 15 min after the last stretch. The increase in ROM was greater after SM (24%) than after SS (13%) and TENS (9%; p < .001). Maximal discomfort level (0-10 VAS) during stretching was similar for all conditions. MVC torque increased after SM only (p < .001, Cohen's D = 1.5): SM, 16%; SS, -1%; TENS, -3%. Force steadiness did not change. The sensory fibres that contribute to stretch tolerance were engaged by self-massage but not by TENS, resulting in greater increases in flexibility and MVC torque after self-massage.

Hydraulic fracture during epithelial stretching

NASA Astrophysics Data System (ADS)

Casares, Laura; Vincent, Romaric; Zalvidea, Dobryna; Campillo, Noelia; Navajas, Daniel; Arroyo, Marino; Trepat, Xavier

2015-03-01

The origin of fracture in epithelial cell sheets subject to stretch is commonly attributed to excess tension in the cells’ cytoskeleton, in the plasma membrane, or in cell-cell contacts. Here, we demonstrate that for a variety of synthetic and physiological hydrogel substrates the formation of epithelial cracks is caused by tissue stretching independently of epithelial tension. We show that the origin of the cracks is hydraulic; they result from a transient pressure build-up in the substrate during stretch and compression manoeuvres. After pressure equilibration, cracks heal readily through actomyosin-dependent mechanisms. The observed phenomenology is captured by the theory of poroelasticity, which predicts the size and healing dynamics of epithelial cracks as a function of the stiffness, geometry and composition of the hydrogel substrate. Our findings demonstrate that epithelial integrity is determined in a tension-independent manner by the coupling between tissue stretching and matrix hydraulics.

Hydraulic fracture during epithelial stretching

PubMed Central

Casares, Laura; Vincent, Romaric; Zalvidea, Dobryna; Campillo, Noelia; Navajas, Daniel; Arroyo, Marino; Trepat, Xavier

2015-01-01

The origin of fracture in epithelial cell sheets subject to stretch is commonly attributed to excess tension in the cells’ cytoskeleton, in the plasma membrane, or in cell-cell contacts. Here we demonstrate that for a variety of synthetic and physiological hydrogel substrates the formation of epithelial cracks is caused by tissue stretching independently of epithelial tension. We show that the origin of the cracks is hydraulic; they result from a transient pressure build-up in the substrate during stretch and compression maneuvers. After pressure equilibration cracks heal readily through actomyosin-dependent mechanisms. The observed phenomenology is captured by the theory of poroelasticity, which predicts the size and healing dynamics of epithelial cracks as a function of the stiffness, geometry and composition of the hydrogel substrate. Our findings demonstrate that epithelial integrity is determined in a tension-independent manner by the coupling between tissue stretching and matrix hydraulics. PMID:25664452

Comparison of Sleep Latency and Number of SOREMPs in the Home and Hospital With a Modified Multiple Sleep Latency Test: A Randomized Crossover Study.

PubMed

Beiske, Kornelia K; Sand, Trond; Rugland, Eyvind; Stavem, Knut

2017-05-01

Comparison of mean sleep latencies and number of sleep-onset rapid eye movement periods (SOREMPs) between modified multiple sleep latency test (MSLT) performed in the unattended home and in-hospital laboratory setting. A randomized crossover single-blinded design. Thirty-four subjects referred to MSLT for suspected hypersomnia or narcolepsy were included. Participants were randomized to perform modified MSLT in the unattended home or in the hospital first. Scores in the two settings were compared using Wilcoxon signed-rank test or exact McNemar test. Agreement between home and hospital categorized mean sleep latency and number of SOREMPs was assessed using simple kappa (κ) and proportion agreement. Agreement between home and hospital mean sleep latency was assessed using a Bland-Altman plot and an intraclass correlation coefficient. There was no difference between home and hospital assessment of mean sleep latency (P = 0.86). Two or more SOREMPs were found more frequently on modified MSLTs performed at home compared with those at the hospital (7 and 2, respectively; P = 0.025). Agreement was moderate for categorized sleep latency (κ = 0.53) and fair for categorized SOREMPs (κ = 0.39) in the 2 settings. Analysis of mean sleep latency using intraclass correlation coefficient showed a very good agreement between the two settings. Group mean sleep latency for home modified MSLTs seems to be reliable compared with that for the attended sleep-laboratory setting. Higher rate of SOREMP in the unattended home suggests that napping in a familiar environment facilitates the transition into REM sleep. Further studies are needed to assess the normal limit, sensitivity, and specificity for SOREMP at home before the clinical utility of home-based napping can be determined.

DNA Molecules Adsorbed on Rippled Supported Cationic Lipid Membranes -- A new way to stretch DNAs

NASA Astrophysics Data System (ADS)

Golubovic, Leonardo

2005-03-01

We discuss a novel approach to control to shapes of DNA molecules. We elucidate the recent experimental work of M. Hochrein, L. Golubovic and J. Raedler, on the conformational behavior of DNA molecules adsorbed on lipid membranes that are supported on grooved micro-structured surfaces. We explain the striking ability of the edges formed on these supported membranes to adsorb and completely orient (stretch) very long DNA molecules. Here we explain the experimentally observed DNA stretching effect in terms of the surface curvature dependent electrostatic potential seen by the adsorbed DNA molecules. On the curved, rippled membrane, we show that the DNA molecules undergo localization transitions causing them to stretch by binding to the ripple edges of the supported membrane. In the future, this stretching will allow to directly image, by the common fluorescence microscopy, fundamental biological processes of the interactions between DNA and single protein molecules.

Immediate effects of kinesiotaping on quadriceps muscle strength: a single-blind, placebo-controlled crossover trial.

PubMed

Vercelli, Stefano; Sartorio, Francesco; Foti, Calogero; Colletto, Lorenzo; Virton, Domenico; Ronconi, Gianpaolo; Ferriero, Giorgio

2012-07-01

To investigate the immediate effects on maximal muscle strength of kinesiotaping (KT) applied to the dominant quadriceps of healthy subjects. Single-blind, placebo-controlled crossover trial. "Salvatore Maugeri" Foundation. With ethical approval and informed consent, a convenience sample of 36 healthy volunteers were recruited. Two subjects did not complete the sessions and were excluded from the analysis. Subjects were tested across 3 different sessions, randomly receiving 2 experimental KT conditions applied with the aim of enhancing and inhibiting muscle strength and a sham KT application. Quadriceps muscle strength was measured by means of an isokinetic maximal test performed at 60 and 180 degrees per second. Two secondary outcome measures were performed: the single-leg triple hop for distance to measure limb performance and the Global Rating of Change Scale (GRCS) to calculate agreement between KT application and subjective perception of strength. Compared with baseline, none of the 3 taping conditions showed a significant change in muscle strength and performance (all P > 0.05). Effect size was very low under all conditions (≤0.08). Very few subjects showed an individual change greater than the minimal detectable change. Global Rating of Change Scale scores demonstrated low to moderate agreement with the type of KT applied, but some placebo effects were reported independently of condition. Our findings indicated no significant effect in the maximal quadriceps strength immediately after the application of inhibition, facilitation, or sham KT. These results do not support the use of KT applied in this way to change maximal muscle strength in healthy people.

Microengineered Conductive Elastomeric Electrodes for Long-Term Electrophysiological Measurements with Consistent Impedance under Stretch

PubMed Central

Hu, Dinglong; Cheng, Tin Kei; Xie, Kai; Lam, Raymond H. W.

2015-01-01

In this research, we develop a micro-engineered conductive elastomeric electrode for measurements of human bio-potentials with the absence of conductive pastes. Mixing the biocompatible polydimethylsiloxane (PDMS) silicone with other biocompatible conductive nano-particles further provides the material with an electrical conductivity. We apply micro-replica mold casting for the micro-structures, which are arrays of micro-pillars embedded between two bulk conductive-PDMS layers. These micro-structures can reduce the micro-structural deformations along the direction of signal transmission; therefore the corresponding electrical impedance under the physical stretch by the movement of the human body can be maintained. Additionally, we conduct experiments to compare the electrical properties between the bulk conductive-PDMS material and the microengineered electrodes under stretch. We also demonstrate the working performance of these micro-engineered electrodes in the acquisition of the 12-lead electrocardiographs (ECG) of a healthy subject. Together, the presented gel-less microengineered electrodes can provide a more convenient and stable bio-potential measurement platform, making tele-medical care more achievable with reduced technical barriers for instrument installation performed by patients/users themselves. PMID:26512662

[Quadriceps tendon insufficiency and rupture : Treatment options in total knee arthroplasty].

PubMed

Thiele, K; von Roth, P; Pfitzner, T; Preininger, B; Perka, C

2016-05-01

Quadriceps tendon injuries and insufficiencies in total knee arthroplasty are rare, but are followed by a devastating complication that left untreated leads to a complete loss of function of the knee. This review article summarizes the functional anatomy, risk factors, and the prevalence and diagnosis of quadriceps tendon injuries, in addition to the possible management options for partial and complete ruptures. The treatment options are adapted according to the extent of the loss of function (partial, complete) and the duration of the injury (acute vs chronic). Furthermore, the choice of treatment should take into account the quality and availability of primary tissue, the patient's general health, along with their likely functional requirements. Conservative treatment is often justified in partial ruptures with good results. Complete ruptures require surgical intervention and multiple operative techniques are described. Treatment options for acute ruptures include direct primary repair with autogenous or synthetic tissue augmentation. In the case of chronic insufficiency and a lack of soft-tissue surroundings, reconstruction with the aid of a muscle flap or allograft tissue can be considered. All surgical intervention techniques used so far have been fraught with complications and rarely lead to satisfactory results. A new surgical approach to the reconstruction and augmentation of the extensor mechanism consists of the use of a synthetic mesh. The technique is described here in detail.

Sensory and motor peripheral nerve function and lower-extremity quadriceps strength: the health, aging and body composition study.

PubMed

Strotmeyer, Elsa S; de Rekeneire, Nathalie; Schwartz, Ann V; Resnick, Helaine E; Goodpaster, Bret H; Faulkner, Kimberly A; Shorr, Ronald I; Vinik, Aaron I; Harris, Tamara B; Newman, Anne B

2009-11-01

To determine whether sensory and motor nerve function is associated cross-sectionally with quadriceps or ankle dorsiflexion strength in an older community-based population. Cross-sectional analyses within a longitudinal cohort study. Two U.S. clinical sites. Two thousand fifty-nine Health, Aging and Body Composition Study (Health ABC) participants (49.5% male, 36.7% black, aged 73-82) in 2000/01. Quadriceps and ankle strength were measured using an isokinetic dynamometer. Sensory and motor peripheral nerve function in the legs and feet was assessed using 10-g and 1.4-g monofilaments, vibration threshold, and peroneal motor nerve conduction amplitude and velocity. Monofilament insensitivity, poorest vibration threshold quartile (>60 mu), and poorest motor nerve conduction amplitude quartile (<1.7 mV) were associated with 11%, 7%, and 8% lower quadriceps strength (all P<.01), respectively, than in the best peripheral nerve function categories in adjusted linear regression models. Monofilament insensitivity and lowest amplitude quartile were both associated with 17% lower ankle strength (P<.01). Multivariate analyses were adjusted for demographic characteristics, diabetes mellitus, body composition, lifestyle factors, and chronic health conditions and included all peripheral nerve measures in the same model. Monofilament insensitivity (beta=-7.19), vibration threshold (beta=-0.097), and motor nerve conduction amplitude (beta=2.01) each contributed independently to lower quadriceps strength (all P<.01). Monofilament insensitivity (beta=-5.29) and amplitude (beta=1.17) each contributed independently to lower ankle strength (all P<.01). Neither diabetes mellitus status nor lean mass explained the associations between peripheral nerve function and strength. Reduced sensory and motor peripheral nerve function is related to poorer lower extremity strength in older adults, suggesting a mechanism for the relationship with lower extremity disability.

In vivo expression of human cytomegalovirus (HCMV) microRNAs during latency.

PubMed

Meshesha, Mesfin K; Bentwich, Zvi; Solomon, Semaria A; Avni, Yonat Shemer

2016-01-01

Viral encoded microRNAs play key roles in regulating gene expression and the life cycle of human herpes viruses. Latency is one of the hallmarks of the human cytomegalovirus (HCMV or HHV5) life cycle, and its control may have immense practical applications. The present study aims to identify HCMV encoded microRNAs during the latency phase of the virus. We used a highly sensitive real time PCR (RTPCR) assay that involves a pre-amplification step before RTPCR. It can detect HCMV encoded microRNAs (miRNAs) during latency in purified monocytes and PBMCs from HCMV IgG positive donors and in latently infected monocytic THP-1 cell lines. During the latency phase, only eight HCMV encoded microRNAs were detected in PBMCs, monocytes and in the THP-1 cells. Five originated from the UL region of the virus genome and three from the US region. Reactivation of the virus from latency, in monocytes obtained from the same donor, using dexamethasone restored the expression of all known HCMV encoded miRNAs including those that were absent during latency. We observed a shift in the abundance of the two arms of mir-US29 between the productive and latency stages of the viral life cycle, suggesting that the star "passenger" form of this microRNA is preferentially expressed during latency. As a whole, our study demonstrates that HCMV expresses during the latency phase, both in vivo and in vitro, only a subset of its microRNAs, which may indicate that they play an important role in maintenance and reactivation of latency. Copyright © 2015 Elsevier B.V. All rights reserved.

Primary display latency criteria based on flying qualities and performance data

NASA Technical Reports Server (NTRS)

Funk, John D., Jr.; Beck, Corin P.; Johns, John B.

1993-01-01

With a pilots' increasing use of visual cue augmentation, much requiring extensive pre-processing, there is a need to establish criteria for new avionics/display design. The timeliness and synchronization of the augmented cues is vital to ensure the performance quality required for precision mission task elements (MTEs) where augmented cues are the primary source of information to the pilot. Processing delays incurred while transforming sensor-supplied flight information into visual cues are unavoidable. Relationships between maximum control system delays and associated flying qualities levels are documented in MIL-F-83300 and MIL-F-8785. While cues representing aircraft status may be just as vital to the pilot as prompt control response for operations in instrument meteorological conditions, presently, there are no specification requirements on avionics system latency. To produce data relating avionics system latency to degradations in flying qualities, the Navy conducted two simulation investigations. During the investigations, flying qualities and performance data were recorded as simulated avionics system latency was varied. Correlated results of the investigation indicates that there is a detrimental impact of latency on flying qualities. Analysis of these results and consideration of key factors influencing their application indicate that: (1) Task performance degrades and pilot workload increases as latency is increased. Inconsistency in task performance increases as latency increases. (2) Latency reduces the probability of achieving Level 1 handling qualities with avionics system latency as low as 70 ms. (3) The data suggest that the achievement of desired performance will be ensured only at display latency values below 120 ms. (4) These data also suggest that avoidance of inadequate performance will be ensured only at display latency values below 150 ms.

Developmental axon stretch stimulates neuron growth while maintaining normal electrical activity, intracellular calcium flux, and somatic morphology

PubMed Central

Loverde, Joseph R.; Pfister, Bryan J.

2015-01-01

Elongation of nerve fibers intuitively occurs throughout mammalian development, and is synchronized with expansion of the growing body. While most tissue systems enlarge through mitosis and differentiation, elongation of nerve fibers is remarkably unique. The emerging paradigm suggests that axons undergo stretch as contiguous tissues enlarge between the proximal and distal segments of spanning nerve fibers. While stretch is distinct from growth, tension is a known stimulus which regulates the growth of axons. Here, we hypothesized that the axon stretch-growth process may be a natural form of injury, whereby regenerative processes fortify elongating axons in order to prevent disconnection. Harnessing the live imaging capability of our axon stretch-growth bioreactors, we assessed neurons both during and following stretch for biomarkers associated with injury. Utilizing whole-cell patch clamp recording, we found no evidence of changes in spontaneous action potential activity or degradation of elicited action potentials during real-time axon stretch at strains of up to 18% applied over 5 min. Unlike traumatic axonal injury, functional calcium imaging of the soma revealed no shifts in free intracellular calcium during axon stretch. Finally, the cross-sectional areas of nuclei and cytoplasms were normal, with no evidence of chromatolysis following week-long stretch-growth limited to the lower of 25% strain or 3 mm total daily stretch. The neuronal growth cascade coupled to stretch was concluded to be independent of the changes in membrane potential, action potential generation, or calcium flux associated with traumatic injury. While axon stretch-growth is likely to share overlap with regenerative processes, we conclude that developmental stretch is a distinct stimulus from traumatic axon injury. PMID:26379492

High throughput web inspection system using time-stretch real-time imaging

NASA Astrophysics Data System (ADS)

Kim, Chanju

Photonic time-stretch is a novel technology that enables capturing of fast, rare and non-repetitive events. Therefore, it operates in real-time with ability to record over long period of time while having fine temporal resolution. The powerful property of photonic time-stretch has already been employed in various fields of application such as analog-to-digital conversion, spectroscopy, laser scanner and microscopy. Further expanding the scope, we fully exploit the time-stretch technology to demonstrate a high throughput web inspection system. Web inspection, namely surface inspection is a nondestructive evaluation method which is crucial for semiconductor wafer and thin film production. We successfully report a dark-field web inspection system with line scan speed of 90.9 MHz which is up to 1000 times faster than conventional inspection instruments. The manufacturing of high quality semiconductor wafer and thin film may directly benefit from this technology as it can easily locate defects with area of less than 10 microm x 10 microm where it allows maximum web flow speed of 1.8 km/s. The thesis provides an overview of our web inspection technique, followed by description of the photonic time-stretch technique which is the keystone in our system. A detailed explanation of each component is covered to provide quantitative understanding of the system. Finally, imaging results from a hard-disk sample and flexible films are presented along with performance analysis of the system. This project was the first application of time-stretch to industrial inspection, and was conducted under financial support and with close involvement by Hitachi, Ltd.

RESPONSE LATENCIES OF NORMAL AND FOCAL-HEAD IRRADIATED MONKEYS

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

McDowell, A.A.; Brown, W.L.

1963-12-01

This study was designed to determine whether focal-head irradiated rhesus monkeys differ from normal monkeys in a manner analogous to that previously found in whole-body irradiated monkeys with respect to response latencies under both familiar and novel stimulus conditions. Five control and four focal-head irradiated rhesus monkeys with nearly identical training histories were used; the latter were survivors of a focal-head irradiation study conducted four years earlier. They had received 3000 r x radiation to the inferior parietal lobule and posterior aspect of the temporal lobe of the brain, and 30 days later the same dosage to the same areamore » of the brain. The testing was conducted in a modified version of the Wisconsin General Test Apparatus, with 24 trials per day for two days, on response latency to a single food-rewarded wooden block placed randomly over either of the two extreme food-well positions. Then, 24 trials were conducted per day for two days on response latency to either the same food-rewarded wooden block or to a novel nonrewarded wooden block presented simultaneously. On the single-block condition, median response latencies of the two groups were comparable and the groups improved in a similar manner with practice. Optimal performance latencies were also comparable for the two groups. When the novel nonrewarded stimulus block was introduced, both groups manifested comparable disruption of median response latencies, but disruption of optimal response latencies was shown only by the focalhead irradiated group. The findings show that monkeys with previous focal-head irradiation of the posterior association areas, unlike relatively high-dose whole-body irradiated monkeys, manifest median response latencies comparable to those of controls. These data indicate the lasting effects of focal-head irradiation with x rays, and suggest that the sites of permanent damage for monkeys given sublethal whole-body radiation exposure differ from the sites

Mechanisms of quadriceps muscle weakness in knee joint osteoarthritis: the effects of prolonged vibration on torque and muscle activation in osteoarthritic and healthy control subjects

PubMed Central

2011-01-01

Introduction A consequence of knee joint osteoarthritis (OA) is an inability to fully activate the quadriceps muscles, a problem termed arthrogenic muscle inhibition (AMI). AMI leads to marked quadriceps weakness that impairs physical function and may hasten disease progression. The purpose of the present study was to determine whether γ-loop dysfunction contributes to AMI in people with knee joint OA. Methods Fifteen subjects with knee joint OA and 15 controls with no history of knee joint pathology participated in this study. Quadriceps and hamstrings peak isometric torque (Nm) and electromyography (EMG) amplitude were collected before and after 20 minutes of 50 Hz vibration applied to the infrapatellar tendon. Between-group differences in pre-vibration torque were analysed using a one-way analysis of covariance, with age, gender and body mass (kg) as the covariates. If the γ-loop is intact, vibration should decrease torque and EMG levels in the target muscle; if dysfunctional, then torque and EMG levels should not change following vibration. One-sample t tests were thus undertaken to analyse whether percentage changes in torque and EMG differed from zero after vibration in each group. In addition, analyses of covariance were utilised to analyse between-group differences in the percentage changes in torque and EMG following vibration. Results Pre-vibration quadriceps torque was significantly lower in the OA group compared with the control group (P = 0.005). Following tendon vibration, quadriceps torque (P < 0.001) and EMG amplitude (P ≤0.001) decreased significantly in the control group but did not change in the OA group (all P > 0.299). Hamstrings torque and EMG amplitude were unchanged in both groups (all P > 0.204). The vibration-induced changes in quadriceps torque and EMG were significantly different between the OA and control groups (all P < 0.011). No between-group differences were observed for the change in hamstrings torque or EMG (all P > 0

Latency in Visionic Systems: Test Methods and Requirements

NASA Technical Reports Server (NTRS)

Bailey, Randall E.; Arthur, J. J., III; Williams, Steven P.; Kramer, Lynda J.

2005-01-01

A visionics device creates a pictorial representation of the external scene for the pilot. The ultimate objective of these systems may be to electronically generate a form of Visual Meteorological Conditions (VMC) to eliminate weather or time-of-day as an operational constraint and provide enhancement over actual visual conditions where eye-limiting resolution may be a limiting factor. Empirical evidence has shown that the total system delays or latencies including the imaging sensors and display systems, can critically degrade their utility, usability, and acceptability. Definitions and measurement techniques are offered herein as common test and evaluation methods for latency testing in visionics device applications. Based upon available data, very different latency requirements are indicated based upon the piloting task, the role in which the visionics device is used in this task, and the characteristics of the visionics cockpit display device including its resolution, field-of-regard, and field-of-view. The least stringent latency requirements will involve Head-Up Display (HUD) applications, where the visionics imagery provides situational information as a supplement to symbology guidance and command information. Conversely, the visionics system latency requirement for a large field-of-view Head-Worn Display application, providing a Virtual-VMC capability from which the pilot will derive visual guidance, will be the most stringent, having a value as low as 20 msec.

Data latency and the user community

NASA Astrophysics Data System (ADS)

Escobar, V. M.; Brown, M. E.; Carroll, M.

2013-12-01

The community using NASA Earth science observations in applications has grown significantly, with increasing sophistication to serve national interests. The National Research Council's Earth Science Decadal Survey report stated that the planning for applied and operational considerations in the missions should accompany the acquisition of new knowledge about Earth (NRC, 2007). This directive has made product applications at NASA an integral part of converting the data collected into actionable knowledge that can be used to inform policy. However, successfully bridging scientific research with operational decision making in different application areas requires looking into user data requirements and operational needs. This study was conducted to determine how users are incorporating NASA data into applications and operational processes. The approach included a review of published materials, direct interviews with mission representatives, and an online professional review, which was distributed to over 6000 individuals. We provide a complete description of the findings with definitions and explanations of what goes into measuring latency as well as how users and applications utilize NASA data products. We identified 3 classes of users: operational (need data in 3 hours or less), near real time (need data within a day of acquisition), and scientific users (need highest quality data, time independent). We also determined that most users with applications are interested in specific types of products that may come from multiple missions. These users will take the observations when they are available, however the observations may have additional applications value if they are available either by a certain time of day or within a period of time after acquisition. NASA has supported the need for access to low latency data on an ad-hoc basis and more substantively in stand-alone systems such as the MODIS Rapid Response system and more recently with LANCE. The increased level

Effect of whole body vibration training on quadriceps strength, bone mineral density, and functional capacity in children with hemophilia: a randomized clinical trial.

PubMed

El-Shamy, S

2017-06-01

The objective was to evaluate the effects of whole body vibration training on quadriceps strength, bone mineral density, and functional capacity in children with hemophilia. Thirty children with hemophilia with age ranging from 9 to 13 years were selected and randomly assigned to either the study group that received whole body vibration training (30-40 Hz, 2-4 mm of peak-to-peak vertical plate displacement for 15 minutes/day, 3 days/week/ 12 weeks) plus the conventional physical therapy program or the control group that performed a conventional physical therapy program only. Outcomes included quadriceps strength, bone mineral density, and the functional capacity. Children in the study group showed a significant improvement in all outcomes compared with the control group. The quadriceps peak torque after treatment was 70.26 and 56.46 Nm for the study and control group, respectively (p⟨0.001). The lumbar spine bone mineral density after treatment was 0.85 and 0.72 g/cm 2 for the study and control group, respectively (p⟨0.001). The functional capacity after treatment was 325 and 290 m for the study and control group, respectively (p=0.006). Whole body vibration training is an effective modality in increasing quadriceps strength, bone mineral density, and functional capacity in children with hemophilia.

DART: A Microcomputer Program for Response Latency Analysis.

ERIC Educational Resources Information Center

Greene, John O.; Greene, Barry F.

1987-01-01

Discusses how chronometric measures such as the DART (Display And Response Timing) computer program, have become virtually indispensable in testing cognitive theories of human social behavior. Describes how the DART (1) provides a way to collect response latency data; and (2) allows measurement of response latencies to a set of user-specified,…

Zebra Alphaherpesviruses (EHV-1 and EHV-9): Genetic Diversity, Latency and Co-Infections.

PubMed

Abdelgawad, Azza; Damiani, Armando; Ho, Simon Y W; Strauss, Günter; Szentiks, Claudia A; East, Marion L; Osterrieder, Nikolaus; Greenwood, Alex D

2016-09-20

Alphaherpesviruses are highly prevalent in equine populations and co-infections with more than one of these viruses' strains frequently diagnosed. Lytic replication and latency with subsequent reactivation, along with new episodes of disease, can be influenced by genetic diversity generated by spontaneous mutation and recombination. Latency enhances virus survival by providing an epidemiological strategy for long-term maintenance of divergent strains in animal populations. The alphaherpesviruses equine herpesvirus 1 (EHV-1) and 9 (EHV-9) have recently been shown to cross species barriers, including a recombinant EHV-1 observed in fatal infections of a polar bear and Asian rhinoceros. Little is known about the latency and genetic diversity of EHV-1 and EHV-9, especially among zoo and wild equids. Here, we report evidence of limited genetic diversity in EHV-9 in zebras, whereas there is substantial genetic variability in EHV-1. We demonstrate that zebras can be lytically and latently infected with both viruses concurrently. Such a co-occurrence of infection in zebras suggests that even relatively slow-evolving viruses such as equine herpesviruses have the potential to diversify rapidly by recombination. This has potential consequences for the diagnosis of these viruses and their management in wild and captive equid populations.

Quadriceps Strength in Patients With Isolated Cartilage Defects of the Knee: Results of Isokinetic Strength Measurements and Their Correlation With Clinical and Functional Results

PubMed Central

Hirschmüller, Anja; Andres, Tasja; Schoch, Wolfgang; Baur, Heiner; Konstantinidis, Lukas; Südkamp, Norbert P.; Niemeyer, Philipp

2017-01-01

Background: Recent studies have found a significant deficit of maximum quadriceps strength after autologous chondrocyte implantation (ACI) of the knee. However, it is unclear whether muscular strength deficits in patients with cartilage damage exist prior to operative treatment. Purpose: To isokinetically test maximum quadriceps muscle strength and quantify the impact of possible strength deficits on functional and clinical test results. Study Design: Cross-sectional study; Level of evidence, 3. Methods: To identify clinically relevant muscular strength deficits, 24 patients (5 females, 19 males; mean age, 34.5 years; body mass index, 25.9 kg/m2) with isolated cartilage defects (mean onset, 5.05 years; SD, 7.8 years) in the knee joint underwent isokinetic strength measurements. Maximal quadriceps strength was recorded in 3 different testing modes: pure concentric contraction (flexors and extensors alternating work; con1), concentric-eccentric (only the extensors work concentrically and eccentrically; con2), and eccentric contraction in the alternating mode (ecc). Results were compared for functional performance (single-leg hop test), pain scales (visual analog scale [VAS], numeric rating scale [NRS]), self-reported questionnaires (International Knee Documentation Committee [IKDC], Knee Injury and Osteoarthritis Outcome Scale [KOOS]), and defect size (cm2). Results: Compared with the uninjured leg, significantly lower quadriceps strength was detected in the injured leg in all isokinetic working modes (con1 difference, 27.76 N·m [SD 17.47; P = .003]; con2 difference, 21.45 N·m [SD, 18.45; P =.025]; ecc difference, 29.48 N·m [SD, 21.51; P = .001]), with the largest deficits found for eccentric muscle performance. Moderate negative correlations were observed for the subjective pain scales NRS and VAS. The results of the IKDC and KOOS questionnaires showed low, nonsignificant correlations with findings in the isokinetic measurement. Moreover, defect sizes (mean, 3

Is hip strengthening the best treatment option for females with patellofemoral pain? A randomized controlled trial of three different types of exercises.

PubMed

Saad, Marcelo Camargo; Vasconcelos, Rodrigo Antunes de; Mancinelli, Letícia Villani de Oliveira; Munno, Matheus Soares de Barros; Liporaci, Rogério Ferreira; Grossi, Débora Bevilaqua

2018-04-04

To evaluate the effect of three types of exercise intervention in patients with patellofemoral pain and to verify the contributions of each intervention to pain control, function, and lower extremity kinematics. A randomized controlled, single-blinded trial was conducted. Forty women with patellofemoral pain were randomly allocated into four groups: hip exercises, quadriceps exercises, stretching exercises and a control group (no intervention). Pain (using a visual analog scale), function (using the Anterior Knee Pain Scale), hip and quadriceps strength (using a handheld isometric dynamometer) and measuring lower limb kinematics during step up and down activities were evaluated at baseline and 8 weeks post intervention. All treatment groups showed significant improvements on pain and Anterior Knee Pain Scale after intervention with no statistically significant differences between groups except when compared to the control group. Only hip and quadriceps groups demonstrated improvements in muscle strength and knee valgus angle during the step activities. Hip strengthening exercises were not more effective for pain relief and function compared to quadriceps or stretching exercises in females with patellofemoral pain. Only hip and quadriceps groups were able to decrease the incidence of dynamic valgus during step-down activity. This study was approved by Brazilian Clinical Trials Registry registration number: RBR-6tc7mj (http://www.ensaiosclinicos.gov.br/rg/RBR-6tc7mj/). Copyright © 2018 Associação Brasileira de Pesquisa e Pós-Graduação em Fisioterapia. Publicado por Elsevier Editora Ltda. All rights reserved.

Reliability of quadriceps surface electromyography measurements is improved by two vs. single site recordings.

PubMed

Balshaw, T G; Fry, A; Maden-Wilkinson, T M; Kong, P W; Folland, J P

2017-06-01

The reliability of surface electromyography (sEMG) is typically modest even with rigorous methods, and therefore further improvements in sEMG reliability are desirable. This study compared the between-session reliability (both within participant absolute reliability and between-participant relative reliability) of sEMG amplitude from single vs. average of two distinct recording sites, for individual muscle (IM) and whole quadriceps (WQ) measures during voluntary and evoked contractions. Healthy males (n = 20) performed unilateral isometric knee extension contractions: voluntary maximum and submaximum (60%), as well as evoked twitch contractions on two separate days. sEMG was recorded from two distinct sites on each superficial quadriceps muscle. Averaging two recording sites vs. using single site measures improved reliability for IM and WQ measurements during voluntary (16-26% reduction in within-participant coefficient of variation, CV W ) and evoked contractions (40-56% reduction in CV W ). For sEMG measurements from large muscles, averaging the recording of two distinct sites is recommended as it improves within-participant reliability. This improved sensitivity has application to clinical and research measurement of sEMG amplitude.

Automatic latency equalization in VHDL-implemented complex pipelined systems

NASA Astrophysics Data System (ADS)

Zabołotny, Wojciech M.

2016-09-01

In the pipelined data processing systems it is very important to ensure that parallel paths delay data by the same number of clock cycles. If that condition is not met, the processing blocks receive data not properly aligned in time and produce incorrect results. Manual equalization of latencies is a tedious and error-prone work. This paper presents an automatic method of latency equalization in systems described in VHDL. The proposed method uses simulation to measure latencies and verify introduced correction. The solution is portable between different simulation and synthesis tools. The method does not increase the complexity of the synthesized design comparing to the solution based on manual latency adjustment. The example implementation of the proposed methodology together with a simple design demonstrating its use is available as an open source project under BSD license.

High-frequency tone burst-evoked ABR latency-intensity functions.

PubMed

Fausti, S A; Olson, D J; Frey, R H; Henry, J A; Schaffer, H I

1993-01-01

High-frequency tone burst stimuli (8, 10, 12, and 14 kHz) have been developed and demonstrated to provide reliable and valid auditory brainstem responses (ABRs) in normal-hearing subjects. In this study, latency-intensity functions (LIFs) were determined using these stimuli in 14 normal-hearing individuals. Significant shifts in response latency occurred as a function of stimulus intensity for all tone burst frequencies. For each 10 dB shift in intensity, latency shifts for waves I and V were statistically significant except for one isolated instance. LIF slopes were comparable between frequencies, ranging from 0.020 to 0.030 msec/dB. These normal LIFs for high-frequency tone burst-evoked ABRs suggest the degree of response latency change that might be expected from, for example, progressive hearing loss due to ototoxic insult, although these phenomena may not be directly related.

Role of microRNAs in herpesvirus latency and persistence.

PubMed

Grey, Finn

2015-04-01

The identification of virally encoded microRNAs (miRNAs) has had a major impact on the field of herpes virology. Given their ability to target cellular and viral transcripts, and the lack of immune response to small RNAs, miRNAs represent an ideal mechanism of gene regulation during viral latency and persistence. In this review, we discuss the role of miRNAs in virus latency and persistence, specifically focusing on herpesviruses. We cover the current knowledge on miRNAs in establishing and maintaining virus latency and promoting survival of infected cells through targeting of both viral and cellular transcripts, highlighting key publications in the field. We also discuss potential areas of future research and how novel technologies may aid in determining how miRNAs shape virus latency in the context of herpesvirus infections. © 2015 The Author.

Test Operations Procedure (TOP) 02-2-546 Teleoperated Unmanned Ground Vehicle (UGV) Latency Measurements

DTIC Science & Technology

2017-01-11

discrete system components or measurements of latency in autonomous systems. 15. SUBJECT TERMS Unmanned Ground Vehicles, Basic Video Latency, End-to... discrete system components or measurements of latency in autonomous systems. 1.1 Basic Video Latency. Teleoperation latency, or lag, describes

Design of Warped Stretch Transform

PubMed Central

Mahjoubfar, Ata; Chen, Claire Lifan; Jalali, Bahram

2015-01-01

Time stretch dispersive Fourier transform enables real-time spectroscopy at the repetition rate of million scans per second. High-speed real-time instruments ranging from analog-to-digital converters to cameras and single-shot rare-phenomena capture equipment with record performance have been empowered by it. Its warped stretch variant, realized with nonlinear group delay dispersion, offers variable-rate spectral domain sampling, as well as the ability to engineer the time-bandwidth product of the signal’s envelope to match that of the data acquisition systems. To be able to reconstruct the signal with low loss, the spectrotemporal distribution of the signal spectrum needs to be sparse. Here, for the first time, we show how to design the kernel of the transform and specifically, the nonlinear group delay profile dictated by the signal sparsity. Such a kernel leads to smart stretching with nonuniform spectral resolution, having direct utility in improvement of data acquisition rate, real-time data compression, and enhancement of ultrafast data capture accuracy. We also discuss the application of warped stretch transform in spectrotemporal analysis of continuous-time signals. PMID:26602458

Acute effect of different time periods of passive static stretching on the hamstring flexibility.

PubMed

Cini, Anelize; de Vasconcelos, Gabriela Souza; Lima, Claudia Silveira

2017-01-01

Several factors are associated with the presence of chronic low back pain; one of them is the flexibility of the hamstring muscles that influences the posture of the pelvic spine. Investigate the influence of two different time periods of passive static stretching on the flexibility of the hamstring. Forty-six physiotherapy students were divided into two groups performing stretching exercises: 30 s and 60 s duration. The collections consisted of: (1) pre-test: evaluation of the flexibility of the hip and knee, using a manual goniometer by means of the following tests: Straight Leg Raise Test (SLR), Passive Hip Flexion Test (PHFT) and Modified Knee Extension Test (MKET), (2) intervention: stretching with different runtimes, (3) post-test: reappraisal of flexibility, conducted immediately after the intervention. Significant difference was observed intra groups, group that did stretching exercises lasting 30 seconds (G30) (SLR p = 0.000. PHFT p = 0.003 and MKET p = 0.000) and group that did stretching exercises lasting 60 seconds (G60) (SLR p = 0.000. PHFT p = 0.001 and MKET p = 0.002). Comparing the groups, no significant difference was found (SLR p = 0.307; PHFT p = 0.904; MKET p = 0.132). Thus it can be inferred that 30 seconds are sufficient for increased flexibility of young women. Therefore the time-treatment sessions can be optimized. Only the acute effect of stretching was observed; further investigation of the long-term effect is required.

The Influence of Non-Nociceptive Factors on Hot Plate Latency in Rats

PubMed Central

Gunn, Amanda; Bobeck, Erin N.; Weber, Ceri; Morgan, Michael M.

2010-01-01

The hot plate is a widely used test to assess nociception. The effect of non-nociceptive factors (weight, sex, activity, habituation, and repeated testing) on hot plate latency was examined. Comparison of body weight and hot plate latency revealed a small but significant inverse correlation (light rats had longer latencies). Habituating rats to the test room for 1 hr prior to testing did not decrease hot plate latency except for female rats tested on Days 2 - 4. Hot plate latency decreased with repeated daily testing, but this was not caused by a decrease in locomotor activity or learning to respond. Activity on the hot plate was consistent across all four trials, and prior exposure to a room temperature plate caused a similar decrease in latency as rats tested repeatedly on the hot plate. Despite this decrease in baseline hot plate latency, there was no difference in morphine antinociceptive potency. The present study shows that weight, habituation to the test room, and repeated testing can alter baseline hot plate latency, but these effects are small and have relatively little impact on morphine antinociception. PMID:20797920

Human embryonic stem cell lines model experimental human cytomegalovirus latency.

PubMed

Penkert, Rhiannon R; Kalejta, Robert F

2013-05-28

Herpesviruses are highly successful pathogens that persist for the lifetime of their hosts primarily because of their ability to establish and maintain latent infections from which the virus is capable of productively reactivating. Human cytomegalovirus (HCMV), a betaherpesvirus, establishes latency in CD34(+) hematopoietic progenitor cells during natural infections in the body. Experimental infection of CD34(+) cells ex vivo has demonstrated that expression of the viral gene products that drive productive infection is silenced by an intrinsic immune defense mediated by Daxx and histone deacetylases through heterochromatinization of the viral genome during the establishment of latency. Additional mechanistic details about the establishment, let alone maintenance and reactivation, of HCMV latency remain scarce. This is partly due to the technical challenges of CD34(+) cell culture, most notably, the difficulty in preventing spontaneous differentiation that drives reactivation and renders them permissive for productive infection. Here we demonstrate that HCMV can establish, maintain, and reactivate in vitro from experimental latency in cultures of human embryonic stem cells (ESCs), for which spurious differentiation can be prevented or controlled. Furthermore, we show that known molecular aspects of HCMV latency are faithfully recapitulated in these cells. In total, we present ESCs as a novel, tractable model for studies of HCMV latency.

Levator Ani Muscle Stretch Induced by Simulated Vaginal Birth

PubMed Central

Lien, Kuo-Cheng; Mooney, Brian; DeLancey, John O. L.; Ashton-Miller, James A.

2005-01-01

OBJECTIVE: To develop a three-dimensional computer model to predict levator ani muscle stretch during vaginal birth. METHODS: Serial magnetic resonance images from a healthy nulliparous 34-year-old woman, published anatomic data, and engineering graphics software were used to construct a structural model of the levator ani muscles along with related passive tissues. The model was used to quantify pelvic floor muscle stretch induced during the second stage of labor as a model fetal head progressively engaged and then stretched the iliococcygeus, pubococcygeus, and puborectalis muscles. RESULTS: The largest tissue strain reached a stretch ratio (tissue length under stretch/original tissue length) of 3.26 in medial pubococcygeus muscle, the shortest, most medial and ventral levator ani muscle. Regions of the ileococcygeus, pubococcygeus, and puborectalis muscles reached maximal stretch ratios of 2.73, 2.50, and 2.28, respectively. Tissue stretch ratios were proportional to fetal head size: For example, increasing fetal head diameter by 9% increased medial pubococcygeus stretch by the same amount. CONCLUSION: The medial pubococcygeus muscles undergo the largest stretch of any levator ani muscles during vaginal birth. They are therefore at the greatest risk for stretch-related injury. PMID:14704241

Minimizing Input-to-Output Latency in Virtual Environment

NASA Technical Reports Server (NTRS)

Adelstein, Bernard D.; Ellis, Stephen R.; Hill, Michael I.

2009-01-01

A method and apparatus were developed to minimize latency (time delay ) in virtual environment (VE) and other discrete- time computer-base d systems that require real-time display in response to sensor input s. Latency in such systems is due to the sum of the finite time requi red for information processing and communication within and between sensors, software, and displays.

Low-latency situational awareness for UxV platforms

NASA Astrophysics Data System (ADS)

Berends, David C.

2012-06-01

Providing high quality, low latency video from unmanned vehicles through bandwidth-limited communications channels remains a formidable challenge for modern vision system designers. SRI has developed a number of enabling technologies to address this, including the use of SWaP-optimized Systems-on-a-Chip which provide Multispectral Fusion and Contrast Enhancement as well as H.264 video compression. Further, the use of salience-based image prefiltering prior to image compression greatly reduces output video bandwidth by selectively blurring non-important scene regions. Combined with our customization of the VLC open source video viewer for low latency video decoding, SRI developed a prototype high performance, high quality vision system for UxV application in support of very demanding system latency requirements and user CONOPS.

Stretching Micropatterned Cells on a PDMS Membrane

PubMed Central

Carpi, Nicolas; Piel, Matthieu

2014-01-01

Mechanical forces exerted on cells and/or tissues play a major role in numerous processes. We have developed a device to stretch cells plated on a PolyDiMethylSiloxane (PDMS) membrane, compatible with imaging. This technique is reproducible and versatile. The PDMS membrane can be micropatterned in order to confine cells or tissues to a specific geometry. The first step is to print micropatterns onto the PDMS membrane with a deep UV technique. The PDMS membrane is then mounted on a mechanical stretcher. A chamber is bound on top of the membrane with biocompatible grease to allow gliding during the stretch. The cells are seeded and allowed to spread for several hours on the micropatterns. The sample can be stretched and unstretched multiple times with the use of a micrometric screw. It takes less than a minute to apply the stretch to its full extent (around 30%). The technique presented here does not include a motorized device, which is necessary for applying repeated stretch cycles quickly and/or computer controlled stretching, but this can be implemented. Stretching of cells or tissue can be of interest for questions related to cell forces, cell response to mechanical stress or tissue morphogenesis. This video presentation will show how to avoid typical problems that might arise when doing this type of seemingly simple experiment. PMID:24514571

Effect of whole body vibration training on quadriceps strength, bone mineral density, and functional capacity in children with hemophilia: a randomized clinical trial

PubMed Central

El-Shamy, S.

2017-01-01

Objectives: The objective was to evaluate the effects of whole body vibration training on quadriceps strength, bone mineral density, and functional capacity in children with hemophilia. Methods: Thirty children with hemophilia with age ranging from 9 to 13 years were selected and randomly assigned to either the study group that received whole body vibration training (30-40 Hz, 2-4 mm of peak-to-peak vertical plate displacement for 15 minutes/day, 3 days/week/ 12 weeks) plus the conventional physical therapy program or the control group that performed a conventional physical therapy program only. Outcomes included quadriceps strength, bone mineral density, and the functional capacity. Results: Children in the study group showed a significant improvement in all outcomes compared with the control group. The quadriceps peak torque after treatment was 70.26 and 56.46 Nm for the study and control group, respectively (p<0.001). The lumbar spine bone mineral density after treatment was 0.85 and 0.72 g/cm2 for the study and control group, respectively (p<0.001). The functional capacity after treatment was 325 and 290 m for the study and control group, respectively (p=0.006). Conclusions: Whole body vibration training is an effective modality in increasing quadriceps strength, bone mineral density, and functional capacity in children with hemophilia. PMID:28574408

Effect of whole body vibration training on quadriceps muscle strength in individuals with knee osteoarthritis: a systematic review and meta-analysis.

PubMed

Anwer, Shahnawaz; Alghadir, Ahmad; Zafar, Hamayun; Al-Eisa, Einas

2016-06-01

Several studies have reported the effects of whole body vibration (WBV) training on muscle strength. This systematic review investigates the current evidence regarding the effects of WBV training on quadriceps muscle strength in individuals with knee osteoarthritis (OA). We searched PubMed, CINAHL, Embase, Scopus, PEDro, and Science citation index for research articles published prior to March 2015 using the keywords whole body vibration, vibration training, strength and vibratory exercise in combination with the Medical Subject Heading 'Osteoarthritis knee'. This meta-analysis was limited to randomized controlled trials published in the English language. The quality of the selected studies was assessed by two independent evaluators using the PEDro scale and criteria given by the International Society of Musculoskeletal and Neuronal Interactions (ISMNI) for reporting WBV intervention studies. The risk of bias was assessed using the Cochrane collaboration's tool for domain-based evaluation. Isokinetic quadriceps muscle strength was calculated for each intervention. Eighteen studies were identified in the search. Of these, four studies met the inclusion criteria. Three of these four studies reached high methodological quality on the PEDro scale. Out of the four studies, only one study found significantly greater quadriceps muscle strength gains following WBV compared to the control group. In three of the four studies that compared a control group performing the same exercise as the WBV groups, no additional effect of WBV on quadriceps muscle strength in individuals with knee OA was indicated. Copyright © 2015 Chartered Society of Physiotherapy. Published by Elsevier Ltd. All rights reserved.

Muscle afferent potential (`A-wave') in the surface electromyogram of a phasic stretch reflex in normal humans

PubMed Central

Clarke, Alex. M.; Michie, Patricia T.; Glue, Leonard C. T.

1972-01-01

The experiments reported in this paper tested the hypothesis that the afferent potential elicited by a tendon tap in an isometrically recorded phasic stretch reflex can be detected in the surface EMG of normal humans when appropriate techniques are used. These techniques involved (1) training the subjects to relax mentally and physically so that the EMG was silent before and immediately after the diphasic MAP which reflects a highly synchronous discharge of afferent impulses from low threshold muscle stretch receptors after a tendon tap, and (2) using a data retrieval computer to summate stimulus-locked potentials in the EMG over a series of 16 samples using taps of uniform peak force and duration on the Achilles tendon to elicit the tendon jerk in the calf muscles. A discrete, diphasic potential (`A-wave') was recorded from EMG electrodes placed on the surface of the skin over the medial gastrocnemius muscle. The `A-wave' afferent potential had the opposite polarity to the corresponding efferent MAP. Under control conditions of relaxation the `A-wave' had a latency after the onset of the tap of 2 msec, the peak to peak amplitude was of the order of 5 μV and the duration was in the range of 6 to 10 msec. Further experiments were conducted to show that the `A-wave' (1) was not an artefact of the instrumentation used, (2) had a threshold at low intensities of stimulation, and (3) could be reliably augmented by using a Jendrassik manoeuvre compared with the potential observed during control (relaxation) conditions. The results support the conclusion that the `A-wave' emanates from the pool of muscle spindles which discharges impulses along group Ia nerve fibres in response to the phasic stretch stimulus because the primary ending of the spindles is known to initiate the stretch reflex and the spindles can be sensitized by fusimotor impulses so that their threshold is lowered as a result of a Jendrassik manoeuvre. The finding has important implications for the

A Simulation Base Investigation of High Latency Space Systems Operations

NASA Technical Reports Server (NTRS)

Li, Zu Qun; Crues, Edwin Z.; Bielski, Paul; Moore, Michael

2017-01-01

NASA's human space program has developed considerable experience with near Earth space operations. Although NASA has experience with deep space robotic missions, NASA has little substantive experience with human deep space operations. Even in the Apollo program, the missions lasted only a few weeks and the communication latencies were on the order of seconds. Human missions beyond the relatively close confines of the Earth-Moon system will involve missions with durations measured in months and communications latencies measured in minutes. To minimize crew risk and to maximize mission success, NASA needs to develop a better understanding of the implications of these types of mission durations and communication latencies on vehicle design, mission design and flight controller interaction with the crew. To begin to address these needs, NASA performed a study using a physics-based subsystem simulation to investigate the interactions between spacecraft crew and a ground-based mission control center for vehicle subsystem operations across long communication delays. The simulation, built with a subsystem modeling tool developed at NASA's Johnson Space Center, models the life support system of a Mars transit vehicle. The simulation contains models of the cabin atmosphere and pressure control system, electrical power system, drinking and waste water systems, internal and external thermal control systems, and crew metabolic functions. The simulation has three interfaces: 1) a real-time crew interface that can be use to monitor and control the vehicle subsystems; 2) a mission control center interface with data transport delays up to 15 minutes each way; 3) a real-time simulation test conductor interface that can be use to insert subsystem malfunctions and observe the interactions between the crew, ground, and simulated vehicle. The study was conducted at the 21st NASA Extreme Environment Mission Operations (NEEMO) mission between July 18th and Aug 3rd of year 2016. The NEEMO

Impact of wave propagation delay on latency in optical communication systems

NASA Astrophysics Data System (ADS)

Kawanishi, Tetsuya; Kanno, Atsushi; Yoshida, Yuki; Kitayama, Ken-ichi

2012-12-01

Latency is an important figure to describe performance of transmission systems for particular applications, such as data transfer for earthquake early warning, transaction for financial businesses, interactive services such as online games, etc. Latency consists of delay due to signal processing at nodes and transmitters, and of signal propagation delay due to propagation of electromagnetic waves. The lower limit of the latency in transmission systems using conventional single mode fibers (SMFs) depends on wave propagation speed in the SMFs which is slower than c. Photonic crystal fibers, holly fibers and large core fibers can have low effective refractive indices, and can transfer light faster than in SMFs. In free-space optical systems, signals propagate with the speed c, so that the latency could be smaller than in optical fibers. For example, LEO satellites would transmit data faster than optical submarine cables, when the transmission distance is longer than a few thousand kilometers. This paper will discuss combination of various transmission media to reduce negative impact of the latency, as well as applications of low-latency systems.

Effects of structured nontarget stimuli on saccadic latency.

PubMed

White, Brian J; Gegenfurtner, Karl R; Kerzel, Dirk

2005-06-01

It has been suggested that the remote distractor effect is the result of nontarget stimulation of a central region representing a collicular fixation zone near the time of target onset. The distributed network of the cells responsible for this effect is believed to extend over a large area, responding to distractors < or =10 deg in the periphery. Several studies also implicate the superior colliculus as the substrate behind an inhibited saccadic response arising from a display change. We investigated this further by using a patch of pink noise of various sizes as a nontarget stimulus. We show that the onset of a small patch (2.3 x 2.3 deg) of centrally displayed pink noise can produce a significant increase in saccadic latency to a simultaneously presented peripheral Gabor target. In contrast, a large patch (36 x 36 deg) of pink noise did not increase latency despite the fact that it also stimulated the region representing the fixation zone. Furthermore, only the large patch of noise facilitated latency when presented before target onset. We also examined the effect of patch sizes between these two extremes and found a steady decrease in latency as patch size increased. This confirms that nontarget stimulation of the region representing the fixation zone near the time of target onset is not in itself sufficient to produce the increase in latency typically found with remote distractors. The results are consistent with the idea that only a spatially confined object leads to a discharge of collicular fixation neurons.

The influence of non-nociceptive factors on hot-plate latency in rats.

PubMed

Gunn, Amanda; Bobeck, Erin N; Weber, Ceri; Morgan, Michael M

2011-02-01

The hot plate is a widely used test to assess nociception. The effect of non-nociceptive factors (weight, sex, activity, habituation, and repeated testing) on hot-plate latency was examined. Comparison of body weight and hot-plate latency revealed a small but significant inverse correlation (light rats had longer latencies). Habituating rats to the test room for 1 hour prior to testing did not decrease hot-plate latency except for female rats tested on days 2 to 4. Hot-plate latency decreased with repeated daily testing, but this was not caused by a decrease in locomotor activity or learning to respond. Activity on the hot plate was consistent across all 4 trials, and prior exposure to a room-temperature plate caused a similar decrease in latency as rats tested repeatedly on the hot plate. Despite this decrease in baseline hot-plate latency, there was no difference in morphine antinociceptive potency. The present study shows that weight, habituation to the test room, and repeated testing can alter baseline hot-plate latency, but these effects are small and have relatively little impact on morphine antinociception. This manuscript shows that non-nociceptive factors such as body weight, habituation, and repeated testing can alter hot-plate latency, but these factors do not alter morphine potency. In sum, the hot-plate test is an easy to use and reliable method to assess supraspinally organized nociceptive responses. Copyright © 2011 American Pain Society. Published by Elsevier Inc. All rights reserved.

Frequency and peak stretch magnitude affect alveolar epithelial permeability.

PubMed

Cohen, T S; Cavanaugh, K J; Margulies, S S

2008-10-01

The present study measured stretch-induced changes in transepithelial permeability to uncharged tracers (1.5-5.5 A) using cultured monolayers of alveolar epithelial type-I like cells. Cultured alveolar epithelial cells were subjected to uniform cyclic (0, 0.25 and 1.0 Hz) biaxial stretch from 0% to 12, 25 or 37% change in surface area (DeltaSA) for 1 h. Significant changes in permeability of cell monolayers were observed when stretched from 0% to 37% DeltaSA at all frequencies, and from 0% to 25% DeltaSA only at high frequency (1 Hz), but not at all when stretched from 0% to 12% DeltaSA compared with unstretched controls. At stretch oscillation amplitudes of 25 and 37% DeltaSA, imposed at 1 Hz, tracer permeability increased compared with that at 0.25 Hz. Cells subjected to a single stretch cycle at 37% DeltaSA (0.25 Hz), to simulate a deep sigh, were not distinguishable from unstretched controls. Reducing stretch oscillation amplitude while maintaining a peak stretch of 37% DeltaSA (0.25 Hz) via the application of a simulated post-end-expiratory pressure did not protect barrier properties. In conclusion, peak stretch magnitude and stretch frequency were the primary determining factors for epithelial barrier dysfunction, as opposed to oscillation amplitude.

To Stretch and Search for Better Ways

NASA Astrophysics Data System (ADS)

Moore, John W.

2000-06-01

There's a lot to do to get each issue of this Journal ready for publication, and there's a lot that can go awry during that process. We the editorial staff do our utmost to make certain that each issue is the best it can possibly be, but, of necessity, a lot of our effort is focused on solving problems, correcting errors, and avoiding pitfalls. It is not surprising that we sometimes lose sight of the bigger picture--all of the things that came out as well as or better than we hoped they would. Therefore it gives us great pleasure when a reader applauds (and thereby rewards) our efforts. One such communication inspired this editorial.

I have appreciated the extra effort put forward by the staff to make the Journal really come alive. The high quality of the Journal serves as an incentive to chemical educators to stretch and search for better ways to inspire our students.

Low Stretch PMMA Burning in Microgravity: Status of the Ground-Based Program and New ISS Glovebox Experiment SALSA

NASA Technical Reports Server (NTRS)

Olson, S. L.; T'ien, J. S.; Armstrong, J. B.

2001-01-01

The objective of this ground-based program is to study low stretch diffusion flames burning PMMA as the solid fuel to determine the relationship between buoyant low stretch burning in normal gravity and forced flow low stretch burning in microgravity. The low stretch is generated in normal gravity by using the buoyant convection induced by burning the bottom of a large radius of curvature sample. Low stretch is also generated using the Combustion Tunnel drop tower rig (2.2 and 5.2 second facilities), which provides a forced convective low velocity flow past smaller radius of curvature samples. Lastly, an ISS glovebox investigation is being developed to study low stretch burning of PMMA spheres to obtain long duration testing needed to accurately assess the flammability and burning characteristics of the material in microgravity. A comparison of microgravity experiment results with normal gravity test results allows us to establish a direct link between a material's burning characteristics in normal gravity (easily measured) with its burning characteristics in extraterrestrial environments, including microgravity forced convective environments. Theoretical predictions and recent experimental results indicate that it should be possible to understand a material's burning characteristics in the low stretch environment of spacecraft (non-buoyant air movement induced by fans and crew disturbances) by understanding its burning characteristics in an equivalent Earth-based low stretch environment (induced by normal gravity buoyancy). Similarly, Earth-based stretch environments can be made equivalent to those in Lunar- and Martian-surface stretch environments (which would induce partial-gravity buoyancy).

CURRENT CONCEPTS IN MUSCLE STRETCHING FOR EXERCISE AND REHABILITATION

PubMed Central

2012-01-01

Stretching is a common activity used by athletes, older adults, rehabilitation patients, and anyone participating in a fitness program. While the benefits of stretching are known, controversy remains about the best type of stretching for a particular goal or outcome. The purpose of this clinical commentary is to discuss the current concepts of muscle stretching interventions and summarize the evidence related to stretching as used in both exercise and rehabilitation. PMID:22319684

Effective therapy of transected quadriceps muscle in rat: Gastric pentadecapeptide BPC 157.

PubMed

Staresinic, Mario; Petrovic, Igor; Novinscak, Tomislav; Jukic, Ivana; Pevec, Damira; Suknaic, Slaven; Kokic, Neven; Batelja, Lovorka; Brcic, Luka; Boban-Blagaic, Alenka; Zoric, Zdenka; Ivanovic, Domagoj; Ajduk, Marko; Sebecic, Bozidar; Patrlj, Leonardo; Sosa, Tomislav; Buljat, Gojko; Anic, Tomislav; Seiwerth, Sven; Sikiric, Predrag

2006-05-01

We report complete transection of major muscle and the systemic peptide treatment that induces healing of quadriceps muscle promptly and then maintains the healing with functional restoration. Initially, stable gastric pentadecapeptide BPC 157 (GEPPPGKPADDAGLV, M.W. 1419, PL-10, PLD-116, PL 14736 Pliva, Croatia; in trials for inflammatory bowel disease; wound treatment; no toxicity reported; effective alone without carrier) also superiorly accelerates the healing of transected Achilles tendon. Regularly, quadriceps muscle completely transected transversely 1.0 cm proximal to patella presents a definitive defect that cannot be compensated in rat. BPC 157 (10 microg, 10 ng, 10 pg/kg) is given intraperitoneally, once daily; the first application 30 min posttransection, the final 24 h before sacrifice. It consistently improves muscle healing throughout the whole 72-day period. Improved are: (i) biomechanic (load of failure increased); (ii) function (walking recovery and extensor postural thrust/motor function index returned toward normal healthy values); (iii) microscopy/immunochemistry [i.e., mostly muscle fibers connect muscle segments; absent gap; significant desmin positivity for ongoing regeneration of muscle; larger myofibril diameters on both sides, distal and proximal (normal healthy rat-values reached)]; (iv) macroscopic presentation (stumps connected; subsequently, atrophy markedly attenuated; finally, presentation close to normal noninjured muscle, no postsurgery leg contracture). Thus, posttransection healing-consistently improved-may suggest this peptide therapeutic application in muscle disorders. Copyright 2006 Orthopaedic Research Society.

Phototherapy during treadmill training improves quadriceps performance in postmenopausal women.

PubMed

Paolillo, F R; Corazza, A V; Paolillo, A R; Borghi-Silva, A; Arena, R; Kurachi, C; Bagnato, V S

2014-06-01

To evaluate the effects of infrared-light-emitting diode (LED) during treadmill training on functional performance. Thirty postmenopausal women aged 50-60 years were randomly assigned to one of three groups and successfully completed the full study. The three groups were: (1) the LED group, which performed treadmill training associated with phototherapy (n = 10); (2) the exercise group, which carried out treadmill training only (n = 10); and (3) the sedentary group, which neither performed physical training nor underwent phototherapy (n = 10). Training was performed over a period of 6 months, twice a week for 45 min per session at 85-90% of maximal heart rate, which was obtained during progressive exercise testing. The irradiation parameters were 100 mW, 39 mW/cm(2) and 108 J/cm(2) for 45 min. Quadriceps performance was measured during isokinetic exercise testing at 60°/s and 300°/s. Peak torque did not differ amongst the groups. However, the results showed significantly higher values of power and total work for the LED group (∆ = 21 ± 6 W and ∆ = 634 ± 156 J, p < 0.05) when compared to both the exercise group (∆ = 13 ± 10 W and = 410 ± 270 J) and the sedentary group (∆ = 10 ± 9 W and ∆ = 357 ± 327 J). Fatigue was also significantly lower in the LED group (∆ = -7 ± 4%, p < 0.05) compared to both the exercise group (∆ = 3 ± 8%) and the sedentary group (∆ = -2 ± 6%). Infrared-LED during treadmill training may improve quadriceps power and reduce peripheral fatigue in postmenopausal women.

Cumulative latency advance underlies fast visual processing in desynchronized brain state

PubMed Central

Wang, Xu-dong; Chen, Cheng; Zhang, Dinghong; Yao, Haishan

2014-01-01

Fast sensory processing is vital for the animal to efficiently respond to the changing environment. This is usually achieved when the animal is vigilant, as reflected by cortical desynchronization. However, the neural substrate for such fast processing remains unclear. Here, we report that neurons in rat primary visual cortex (V1) exhibited shorter response latency in the desynchronized state than in the synchronized state. In vivo whole-cell recording from the same V1 neurons undergoing the two states showed that both the resting and visually evoked conductances were higher in the desynchronized state. Such conductance increases of single V1 neurons shorten the response latency by elevating the membrane potential closer to the firing threshold and reducing the membrane time constant, but the effects only account for a small fraction of the observed latency advance. Simultaneous recordings in lateral geniculate nucleus (LGN) and V1 revealed that LGN neurons also exhibited latency advance, with a degree smaller than that of V1 neurons. Furthermore, latency advance in V1 increased across successive cortical layers. Thus, latency advance accumulates along various stages of the visual pathway, likely due to a global increase of membrane conductance in the desynchronized state. This cumulative effect may lead to a dramatic shortening of response latency for neurons in higher visual cortex and play a critical role in fast processing for vigilant animals. PMID:24347634

Cumulative latency advance underlies fast visual processing in desynchronized brain state.

PubMed

Wang, Xu-dong; Chen, Cheng; Zhang, Dinghong; Yao, Haishan

2014-01-07

Fast sensory processing is vital for the animal to efficiently respond to the changing environment. This is usually achieved when the animal is vigilant, as reflected by cortical desynchronization. However, the neural substrate for such fast processing remains unclear. Here, we report that neurons in rat primary visual cortex (V1) exhibited shorter response latency in the desynchronized state than in the synchronized state. In vivo whole-cell recording from the same V1 neurons undergoing the two states showed that both the resting and visually evoked conductances were higher in the desynchronized state. Such conductance increases of single V1 neurons shorten the response latency by elevating the membrane potential closer to the firing threshold and reducing the membrane time constant, but the effects only account for a small fraction of the observed latency advance. Simultaneous recordings in lateral geniculate nucleus (LGN) and V1 revealed that LGN neurons also exhibited latency advance, with a degree smaller than that of V1 neurons. Furthermore, latency advance in V1 increased across successive cortical layers. Thus, latency advance accumulates along various stages of the visual pathway, likely due to a global increase of membrane conductance in the desynchronized state. This cumulative effect may lead to a dramatic shortening of response latency for neurons in higher visual cortex and play a critical role in fast processing for vigilant animals.

Randomized Controlled Trial Comparing Orthosis Augmented by Either Stretching or Stretching and Strengthening for Stage II Tibialis Posterior Tendon Dysfunction.

PubMed

Houck, Jeff; Neville, Christopher; Tome, Josh; Flemister, Adolph

2015-09-01

The value of strengthening and stretching exercises combined with orthosis treatment in a home-based program has not been evaluated. The purpose of this study was to compare the effects of augmenting orthosis treatment with either stretching or a combination of stretching and strengthening in participants with stage II tibialis posterior tendon dysfunction (TPTD). Participants included 39 patients with stage II TPTD who were recruited from a medical center and then randomly assigned to a strengthening or stretching treatment group. Excluding 3 dropouts, there were 19 participants in the strengthening group and 17 in the stretching group. The stretching treatment consisted of a prefabricated orthosis used in conjunction with stretching exercises. The strengthening treatment consisted of a prefabricated orthosis used in conjunction with the stretching and strengthening exercises. The main outcome measures were self-report (ie, Foot Function Index and Short Musculoskeletal Function Assessment) and isometric deep posterior compartment strength. Two-way analysis of variance was used to test for differences between groups at 6 and 12 weeks after starting the exercise programs. Both groups significantly improved in pain and function over the 12-week trial period. The self-report measures showed minimal differences between the treatment groups. There were no differences in isometric deep posterior compartment strength. A moderate-intensity, home-based exercise program was minimally effective in augmenting orthosis wear alone in participants with stage II TPTD. Level I, prospective randomized study. © The Author(s) 2015.

Stretching-induced wrinkling in plastic-rubber composites.

PubMed

Yang, Junyu; Damle, Sameer; Maiti, Spandan; Velankar, Sachin S

2017-01-25

We examine the mechanics of three-layer composite films composed of an elastomeric layer sandwiched between two thin surface layers of plastic. Upon stretching and releasing such composite films, they develop a highly wrinkled surface texture. The mechanism for this texturing is that during stretching, the plastic layers yield and stretch irreversibly whereas the elastomer stretches reversibly. Thus upon releasing, the plastic layers buckle due to compressive stress imposed by the elastomer. Experiments are conducted using SEPS elastomer and 50 micron thick LLDPE plastic films. Stretching and releasing the composites to 2-5 times their original length induces buckles with wavelength on the order of 200 microns, and the wavelength decreases as the stretching increases. FEM simulations reveal that plastic deformation is involved at all stages during this process: (1) during stretching, the plastic layer yields in tension; (2) during recovery, the plastic layer first yields in-plane in compression and then buckles; (3) post-buckling, plastic hinges are formed at high-curvature regions. Homogeneous wrinkles are predicted only within a finite window of material properties: if the yield stress is too low, the plastic layers yield in-plane, without wrinkling, whereas if the yield stress is too high, non-homogeneous wrinkles are predicted. This approach to realizing highly wrinkled textures offers several advantages, most importantly the fact that high aspect ratio wrinkles (amplitude to wavelength ratios exceeding 0.4) can be realized.

Effects of static stretching of knee musculature on patellar alignment and knee functional disability in male patients diagnosed with knee extension syndrome: A single-group, pretest-posttest trial.

PubMed

Pourahmadi, Mohammad Reza; Ebrahimi Takamjani, Ismail; Hesampour, Kazem; Shah-Hosseini, Gholam Reza; Jamshidi, Ali Ashraf; Shamsi, Mohammad Bagher

2016-04-01

Knee extension (Kext) syndrome is based on movement system impairments and is described as knee pain associated with quadriceps stiffness. To investigate the effects of 3 times per week for 4 weeks static stretching of knee musculature on patellar alignment and knee functional disability in male Kext syndrome patients. A single-group, pretest-posttest clinical trial. Hazrat-e-Rasoul Akram Hospital. Forty-six male Kext syndrome patients aged 18-35 years. Knee functional disability was assessed by the Kujala questionnaire. Patellar tilt was assessed using the skyline view X-ray. In addition, patella alta was assessed by X-ray using the Insall-Salvati ratio. After intervention, changes in knee flexion-extension range of motion (ROM) and hip adduction were assessed by goniometer and inclinometer. Changes in patellar tilt and patella alta were evaluated. Correlations between muscles length, patellar tilt and knee functional disability were also evaluated. The mean of patellar tilt in male Kext syndrome patients was 15.19°. Only the correlation between rectus femoris shortness and patellar tilt (P = 0.002) and the correlation between rectus femoris shortness and knee functional disability (P = 0.037) were significant. Patella alta was not severe in male Kext syndrome patients (1.28 ± 0.10). Knee flexion-extension ROM and femoral adduction increased significantly after a 12-session stretching programme (P < 0.0001). The results demonstrated that rectus femoris shortness had higher correlation with patellar tilt and knee functional disability than iliotibial band and hamstring shortness. Stretching was effective in reducing patellar tilt, patella alta, knee functional disability, increasing knee ROM and hip adduction in these patients. Copyright © 2015 Elsevier Ltd. All rights reserved.

Comparison of lower body specific resistance training on the hamstring to quadriceps strength ratios in men and women.

PubMed

Dorgo, Sandor; Edupuganti, Pradeep; Smith, Darla R; Ortiz, Melchor

2012-06-01

In this study, we compared hamstring (H) and quadriceps (Q) strength changes in men and women, as well as changes in conventional and functional H:Q ratios following an identical 12-week resistance training program. An isokinetic dynamometer was used to assess 14 male and 14 female participants before and after the intervention, and conventional and functional H:Q ratios were calculated. Hamstring strength improved similarly in men and women, but improvement in quadriceps strength was significantly greater in men, while women showed only modest improvements. For the conventional and functional H:Q ratios, women showed significantly greater improvements than men. Both men and women were able to exceed the commonly recommended 0.6 conventional and 1.0 functional H:Q ratios after the 12-week lower-body resistance training program.

On the origin of stretched exponential (Kohlrausch) relaxation kinetics in the room temperature luminescence decay of colloidal quantum dots.

PubMed

Bodunov, E N; Antonov, Yu A; Simões Gamboa, A L

2017-03-21

The non-exponential room temperature luminescence decay of colloidal quantum dots is often well described by a stretched exponential function. However, the physical meaning of the parameters of the function is not clear in the majority of cases reported in the literature. In this work, the room temperature stretched exponential luminescence decay of colloidal quantum dots is investigated theoretically in an attempt to identify the underlying physical mechanisms associated with the parameters of the function. Three classes of non-radiative transition processes between the excited and ground states of colloidal quantum dots are discussed: long-range resonance energy transfer, multiphonon relaxation, and contact quenching without diffusion. It is shown that multiphonon relaxation cannot explain a stretched exponential functional form of the luminescence decay while such dynamics of relaxation can be understood in terms of long-range resonance energy transfer to acceptors (molecules, quantum dots, or anharmonic molecular vibrations) in the environment of the quantum dots acting as energy-donors or by contact quenching by acceptors (surface traps or molecules) distributed statistically on the surface of the quantum dots. These non-radiative transition processes are assigned to different ranges of the stretching parameter β.

Construction and Evaluation of an Ultra Low Latency Frameless Renderer for VR.

PubMed

Friston, Sebastian; Steed, Anthony; Tilbury, Simon; Gaydadjiev, Georgi

2016-04-01

Latency - the delay between a user's action and the response to this action - is known to be detrimental to virtual reality. Latency is typically considered to be a discrete value characterising a delay, constant in time and space - but this characterisation is incomplete. Latency changes across the display during scan-out, and how it does so is dependent on the rendering approach used. In this study, we present an ultra-low latency real-time ray-casting renderer for virtual reality, implemented on an FPGA. Our renderer has a latency of ~1 ms from 'tracker to pixel'. Its frameless nature means that the region of the display with the lowest latency immediately follows the scan-beam. This is in contrast to frame-based systems such as those using typical GPUs, for which the latency increases as scan-out proceeds. Using a series of high and low speed videos of our system in use, we confirm its latency of ~1 ms. We examine how the renderer performs when driving a traditional sequential scan-out display on a readily available HMO, the Oculus Rift OK2. We contrast this with an equivalent apparatus built using a GPU. Using captured human head motion and a set of image quality measures, we assess the ability of these systems to faithfully recreate the stimuli of an ideal virtual reality system - one with a zero latency tracker, renderer and display running at 1 kHz. Finally, we examine the results of these quality measures, and how each rendering approach is affected by velocity of movement and display persistence. We find that our system, with a lower average latency, can more faithfully draw what the ideal virtual reality system would. Further, we find that with low display persistence, the sensitivity to velocity of both systems is lowered, but that it is much lower for ours.

EXERCISES THAT FACILITATE OPTIMAL HAMSTRING AND QUADRICEPS CO-ACTIVATION TO HELP DECREASE ACL INJURY RISK IN HEALTHY FEMALES: A SYSTEMATIC REVIEW OF THE LITERATURE.

PubMed Central

Dedinsky, Rachel; Baker, Lindsey; Imbus, Samuel; Bowman, Melissa

2017-01-01

Background Anterior cruciate ligament (ACL) injury is common among females due to many anatomic, hormonal, and neuromuscular risk factors. One modifiable risk factor that places females at increased risk of ACL injury is a poor hamstrings: quadriceps (H:Q) co-activation ratio, which should be 0.6 or greater in order to decrease the stress placed on the ACL. Exercises that produce more quadriceps dominant muscle activation can add to the tension placed upon the ACL, potentially increasing the risk of ACL injury. Hypothesis/Purpose The purpose of this systematic review was to compare quadriceps and hamstring muscle activation during common closed kinetic chain therapeutic exercises in healthy female knees to determine what exercises are able to produce adequate H:Q co-activation ratios. Study Design Systematic Review Methods Multiple online databases were systematically searched and screened for inclusion. Eight articles were identified for inclusion. Data on mean electromyography (EMG) activation of both quadriceps and hamstring muscles, % maximal voluntary isometric contraction (MVIC), and H:Q co-activation ratios were extracted from the studies. Quality assessment was performed on all included studies. Results Exercises analyzed in the studies included variations of the double leg squat, variations of the single leg squat, lateral step-up, Fitter, Stairmaster® (Core Health and Fitness, Vancouver, WA), and slide board. All exercises, except the squat machine with posterior support at the level of the scapula and feet placed 50 cm in front of the hips, produced higher quadriceps muscle activation compared to hamstring muscle activation. Conclusion Overall, two leg squats demonstrate poor H:Q co-activation ratios. Single leg exercises, when performed between 30 and 90 degrees of knee flexion, produce adequate H:Q ratios, thereby potentially reducing the risk of tensile stress on the ACL and ACL injury. Level of Evidence 2a- Systematic Review of Cohort Studies PMID

Hyperglycemia Augments the Adipogenic Transdifferentiation Potential of Tenocytes and Is Alleviated by Cyclic Mechanical Stretch.

PubMed

Wu, Yu-Fu; Huang, Yu-Ting; Wang, Hsing-Kuo; Yao, Chung-Chen Jane; Sun, Jui-Sheng; Chao, Yuan-Hung

2017-12-28

Diabetes mellitus is associated with damage to tendons, which may result from cellular dysfunction in response to a hyperglycemic environment. Tenocytes express diminished levels of tendon-associated genes under hyperglycemic conditions. In contrast, mechanical stretch enhances tenogenic differentiation. However, whether hyperglycemia increases the non-tenogenic differentiation potential of tenocytes and whether this can be mitigated by mechanical stretch remains elusive. We explored the in vitro effects of high glucose and mechanical stretch on rat primary tenocytes. Specifically, non-tenogenic gene expression, adipogenic potential, cell migration rate, filamentous actin expression, and the activation of signaling pathways were analyzed in tenocytes treated with high glucose, followed by the presence or absence of mechanical stretch. We analyzed tenocyte phenotype in vivo by immunohistochemistry using an STZ (streptozotocin)-induced long-term diabetic mouse model. High glucose-treated tenocytes expressed higher levels of the adipogenic transcription factors PPAR γ and C/EBPs. PPARγ was also highly expressed in diabetic tendons. In addition, increased adipogenic differentiation and decreased cell migration induced by high glucose implicated a fibroblast-to-adipocyte phenotypic change. By applying mechanical stretch to tenocytes in high-glucose conditions, adipogenic differentiation was repressed, while cell motility was enhanced, and fibroblastic morphology and gene expression profiles were strengthened. In part, these effects resulted from a stretch-induced activation of ERK (extracellular signal-regulated kinases) and a concomitant inactivation of Akt. Our results show that mechanical stretch alleviates the augmented adipogenic transdifferentiation potential of high glucose-treated tenocytes and helps maintain their fibroblastic characteristics. The alterations induced by high glucose highlight possible pathological mechanisms for diabetic tendinopathy

A Discrete Electromechanical Model for Human Cardiac Tissue: Effects of Stretch-Activated Currents and Stretch Conditions on Restitution Properties and Spiral Wave Dynamics

PubMed Central

Weise, Louis D.; Panfilov, Alexander V.

2013-01-01

We introduce an electromechanical model for human cardiac tissue which couples a biophysical model of cardiac excitation (Tusscher, Noble, Noble, Panfilov, 2006) and tension development (adjusted Niederer, Hunter, Smith, 2006 model) with a discrete elastic mass-lattice model. The equations for the excitation processes are solved with a finite difference approach, and the equations of the mass-lattice model are solved using Verlet integration. This allows the coupled problem to be solved with high numerical resolution. Passive mechanical properties of the mass-lattice model are described by a generalized Hooke's law for finite deformations (Seth material). Active mechanical contraction is initiated by changes of the intracellular calcium concentration, which is a variable of the electrical model. Mechanical deformation feeds back on the electrophysiology via stretch-activated ion channels whose conductivity is controlled by the local stretch of the medium. We apply the model to study how stretch-activated currents affect the action potential shape, restitution properties, and dynamics of spiral waves, under constant stretch, and dynamic stretch caused by active mechanical contraction. We find that stretch conditions substantially affect these properties via stretch-activated currents. In constantly stretched medium, we observe a substantial decrease in conduction velocity, and an increase of action potential duration; whereas, with dynamic stretch, action potential duration is increased only slightly, and the conduction velocity restitution curve becomes biphasic. Moreover, in constantly stretched medium, we find an increase of the core size and period of a spiral wave, but no change in rotation dynamics; in contrast, in the dynamically stretching medium, we observe spiral drift. Our results may be important to understand how altered stretch conditions affect the heart's functioning. PMID:23527160

A discrete electromechanical model for human cardiac tissue: effects of stretch-activated currents and stretch conditions on restitution properties and spiral wave dynamics.

PubMed

Weise, Louis D; Panfilov, Alexander V

2013-01-01

We introduce an electromechanical model for human cardiac tissue which couples a biophysical model of cardiac excitation (Tusscher, Noble, Noble, Panfilov, 2006) and tension development (adjusted Niederer, Hunter, Smith, 2006 model) with a discrete elastic mass-lattice model. The equations for the excitation processes are solved with a finite difference approach, and the equations of the mass-lattice model are solved using Verlet integration. This allows the coupled problem to be solved with high numerical resolution. Passive mechanical properties of the mass-lattice model are described by a generalized Hooke's law for finite deformations (Seth material). Active mechanical contraction is initiated by changes of the intracellular calcium concentration, which is a variable of the electrical model. Mechanical deformation feeds back on the electrophysiology via stretch-activated ion channels whose conductivity is controlled by the local stretch of the medium. We apply the model to study how stretch-activated currents affect the action potential shape, restitution properties, and dynamics of spiral waves, under constant stretch, and dynamic stretch caused by active mechanical contraction. We find that stretch conditions substantially affect these properties via stretch-activated currents. In constantly stretched medium, we observe a substantial decrease in conduction velocity, and an increase of action potential duration; whereas, with dynamic stretch, action potential duration is increased only slightly, and the conduction velocity restitution curve becomes biphasic. Moreover, in constantly stretched medium, we find an increase of the core size and period of a spiral wave, but no change in rotation dynamics; in contrast, in the dynamically stretching medium, we observe spiral drift. Our results may be important to understand how altered stretch conditions affect the heart's functioning.

Reinforcement for Stretch Formed Sheet Metal

NASA Technical Reports Server (NTRS)

Lea, J. B.; Baxter, C. R.

1983-01-01

Tearing of aluminum sheet metal durinng stretch forming prevented by flame spraying layer of aluminum on edges held in stretch-forming machine. Technique improves grip of machine on metal and reinforced sheet better able to with stand concentration of force in vicinity of grips.

Defining the Transcriptional Landscape during Cytomegalovirus Latency with Single-Cell RNA Sequencing

PubMed Central

2018-01-01

ABSTRACT Primary infection with human cytomegalovirus (HCMV) results in a lifelong infection due to its ability to establish latent infection, with one characterized viral reservoir being hematopoietic cells. Although reactivation from latency causes serious disease in immunocompromised individuals, our molecular understanding of latency is limited. Here, we delineate viral gene expression during natural HCMV persistent infection by analyzing the massive transcriptome RNA sequencing (RNA-seq) atlas generated by the Genotype-Tissue Expression (GTEx) project. This systematic analysis reveals that HCMV persistence in vivo is prevalent in diverse tissues. Notably, we find only viral transcripts that resemble gene expression during various stages of lytic infection with no evidence of any highly restricted latency-associated viral gene expression program. To further define the transcriptional landscape during HCMV latent infection, we also used single-cell RNA-seq and a tractable experimental latency model. In contrast to some current views on latency, we also find no evidence for any highly restricted latency-associated viral gene expression program. Instead, we reveal that latency-associated gene expression largely mirrors a late lytic viral program, albeit at much lower levels of expression. Overall, our work has the potential to revolutionize our understanding of HCMV persistence and suggests that latency is governed mainly by quantitative changes, with a limited number of qualitative changes, in viral gene expression. PMID:29535194

Collagen and Stretch Modulate Autocrine Secretion of Insulin-like Growth Factor-1 and Insulin-like Growth Factor Binding Proteins from Differentiated Skeletal Muscle Cells

NASA Technical Reports Server (NTRS)

Perrone, Carmen E.; Fenwick-Smith, Daniela; Vandenburgh, Herman H.

1995-01-01

Stretch-induced skeletal muscle growth may involve increased autocrine secretion of insulin-like growth factor-1 (IGF-1) since IGF-1 is a potent growth factor for skeletal muscle hypertrophy, and stretch elevates IGF-1 mRNA levels in vivo. In tissue cultures of differentiated avian pectoralis skeletal muscle cells, nanomolar concentrations of exogenous IGF-1 stimulated growth in mechanically stretched but not static cultures. These cultures released up to 100 pg of endogenously produced IGF-1/micro-g of protein/day, as well as three major IGF binding proteins of 31, 36, and 43 kilodaltons (kDa). IGF-1 was secreted from both myofibers and fibroblasts coexisting in the muscle cultures. Repetitive stretch/relaxation of the differentiated skeletal muscle cells stimulated the acute release of IGF-1 during the first 4 h after initiating mechanical activity, but caused no increase in the long-term secretion over 24-72 h of IGF-1, or its binding proteins. Varying the intensity and frequency of stretch had no effect on the long-term efflux of IGF-1. In contrast to stretch, embedding the differentiated muscle cells in a three-dimensional collagen (Type I) matrix resulted in a 2-5-fold increase in long-term IGF-1 efflux over 24-72 h. Collagen also caused a 2-5-fold increase in the release of the IGF binding proteins. Thus, both the extracellular matrix protein type I collagen and stretch stimulate the autocrine secretion of IGF-1, but with different time kinetics. This endogenously produced growth factor may be important for the growth response of skeletal myofibers to both types of external stimuli.

Glomerular latency coding in artificial olfaction.

PubMed

Yamani, Jaber Al; Boussaid, Farid; Bermak, Amine; Martinez, Dominique

2011-01-01

Sensory perception results from the way sensory information is subsequently transformed in the brain. Olfaction is a typical example in which odor representations undergo considerable changes as they pass from olfactory receptor neurons (ORNs) to second-order neurons. First, many ORNs expressing the same receptor protein yet presenting heterogeneous dose-response properties converge onto individually identifiable glomeruli. Second, onset latency of glomerular activation is believed to play a role in encoding odor quality and quantity in the context of fast information processing. Taking inspiration from the olfactory pathway, we designed a simple yet robust glomerular latency coding scheme for processing gas sensor data. The proposed bio-inspired approach was evaluated using an in-house SnO(2) sensor array. Glomerular convergence was achieved by noting the possible analogy between receptor protein expressed in ORNs and metal catalyst used across the fabricated gas sensor array. Ion implantation was another technique used to account both for sensor heterogeneity and enhanced sensitivity. The response of the gas sensor array was mapped into glomerular latency patterns, whose rank order is concentration-invariant. Gas recognition was achieved by simply looking for a "match" within a library of spatio-temporal spike fingerprints. Because of its simplicity, this approach enables the integration of sensing and processing onto a single-chip.

Hip pain

MedlinePlus

... from a chair, walking, climbing stairs, and driving Hamstring strain Iliotibial band syndrome Hip flexor strain Hip ... and cool down afterward. Stretch your quadriceps and hamstrings. Avoid running straight down hills. Walk down instead. ...

DYNAMIC OSCILLATORY STRETCHING EFFICACY ON HAMSTRING EXTENSIBILITY AND STRETCH TOLERANCE: A RANDOMIZED CONTROLLED TRIAL

PubMed Central

Tee, Jason Cameron; Stewart, Aimee

2017-01-01

Background While static stretch (SS), proprioceptive neuromuscular facilitation (PNF) and oscillatory physiological mobilization techniques are documented to have positive effects on a range of motion (ROM), there are no reports on the effect of dynamic oscillatory stretching (DOS), a technique that combines these three techniques, on hamstring extensibility. Purpose To determine whether DOS improves hamstring extensibility and stretch tolerance to a greater degree than SS in asymptomatic young participants. Study Design Randomized Controlled Trial. Methods Sixty participants (47 females, 13 males, mean age 22 ± 1 years, height 166 ± 6 centimeters, body mass 67.6 ± 9.7 kg) completed a passive straight leg (SLR) to establish hamstring extensibility and stretch tolerance as perceived by participants, using a visual analogue scale (VAS). Participants were randomly assigned to one of two treatment groups (SS or DOS) or a placebo control (20 per group). Tests were repeated immediately following and one hour after each intervention. Data were assessed using a two-way repeated measure analysis of variance (ANOVA) and Tukey's post hoc test. Results Immediately post-intervention, there was a significant improvement in the hamstring extensibility as measured by the SLR in both the SS and DOS groups, with the DOS group exhibiting a significantly greater increase than the SS group (Control 73 ± 12°, SS 86 ± 8°, DOS 94 ± 11°, p < 0.001). One hour post-intervention, hamstring extensibility in the DOS group remained elevated, while the SS group no longer differed from the control group (Control 73 ± 12°, SS 80 ± 8°, DOS 89 ± 12°, p = 0.001). Furthermore, the stretch tolerance remained significantly elevated for the SS group, but there was no difference between the control and DOS groups, (Control 4.6 ± 1.3, SS 5.9 ± 0.8, DOS 4.3 ± 1.0 AU, p < 0.001). Conclusion DOS was more effective than SS at achieving

Fault latency in the memory - An experimental study on VAX 11/780

NASA Technical Reports Server (NTRS)

Chillarege, Ram; Iyer, Ravishankar K.

1986-01-01

Fault latency is the time between the physical occurrence of a fault and its corruption of data, causing an error. The measure of this time is difficult to obtain because the time of occurrence of a fault and the exact moment of generation of an error are not known. This paper describes an experiment to accurately study the fault latency in the memory subsystem. The experiment employs real memory data from a VAX 11/780 at the University of Illinois. Fault latency distributions are generated for s-a-0 and s-a-1 permanent fault models. Results show that the mean fault latency of a s-a-0 fault is nearly 5 times that of the s-a-1 fault. Large variations in fault latency are found for different regions in memory. An analysis of a variance model to quantify the relative influence of various workload measures on the evaluated latency is also given.

Treatment of high-latency microcapsules containing an aluminium complex with an epoxy-functionalised trialkoxysilane.

PubMed

Kamiya, Kazunobu; Suzuki, Noboru

2016-12-01

Some aluminium complexes are excellent catalysts of cationic polymerisation and are used for low-temperature and fast-curing adhesive, used in electronic part mounting. Microencapsulation is a suitable technique for getting high latency of the catalysts and long shelf life of the adhesives. For the higher latency in a cycloaliphatic epoxy compound, the microcapsule surface which retained small amount of aluminium complex was coated with epoxy polymer and the effect was examined. From the X-ray photoelectron spectroscopic results, the surface was recognised to be sufficiently coated and the differential scanning calorimetric analyses showed that the coating did not significantly affect the low-temperature and fast-curing properties of adhesive. After storing the mixture of cycloaliphatic epoxy compound, coated microcapsules, triphenylsilanol and silane coupling agent for 48 h at room temperature, the increase in viscosity was only 0.01 Pa s, resulting in the excellent shelf life.

Effects of cervical self-stretching on slow vital capacity.

PubMed

Han, Dongwook; Yoon, Nayoon; Jeong, Yeongran; Ha, Misook; Nam, Kunwoo

2015-07-01

[Purpose] This study investigated the effects of self-stretching of cervical muscles, because the accessory inspiratory muscle is considered to improve pulmonary function. [Subjects] The subjects were 30 healthy university students 19-21 years old who did not have any lung disease, respiratory dysfunction, cervical injury, or any problems upon cervical stretching. [Methods] Spirometry was used as a pulmonary function test to measure the slow vital capacity before and after stretching. The slow vital capacity of the experimental group was measured before and after cervical self-stretching. Meanwhile, the slow vital capacity of the control group, which did not perform stretching, was also measured before and after the intervention. [Results] The expiratory vital capacity, inspiratory reserve volume, and expiratory reserve volume of the experimental group increased significantly after the cervical self-stretching. [Conclusion] Self-stretching of the cervical muscle (i.e., the inspiratory accessory muscle) improves slow vital capacity.

Hamstrings to quadriceps peak torque ratios diverge between sexes with increasing isokinetic angular velocity.

PubMed

Hewett, Timothy E; Myer, Gregory D; Zazulak, Bohdanna T

2008-09-01

Our purpose was to determine if females demonstrate decreased hamstrings to quadriceps peak torque (H/Q) ratios compared to males and if H/Q ratios increase with increased isokinetic velocity in both sexes. Maturation disproportionately increases hamstrings peak torque at high velocity in males, but not females. Therefore, we hypothesised that mature females would demonstrate decreased H/Q ratios compared to males and the difference in H/Q ratio between sexes would increase as isokinetic velocity increased. Studies that analysed the H/Q ratio with gravity corrected isokinetic strength testing reported between 1967 and 2004 were included in our review and analysis. Keywords were hamstrings/quadriceps, isokinetics, peak torque and gravity corrected. Medline and Smart databases were searched combined with cross-checked bibliographic reference lists of the publications to determine studies to be included. Twenty-two studies were included with a total of 1568 subjects (1145 male, 423 female). Males demonstrated a significant correlation between H/Q ratio and isokinetic velocity (R=0.634, p<0.0001), and a significant difference in the isokinetic H/Q ratio at the lowest angular velocity (47.8+/-2.2% at 30 degrees /s) compared to the highest velocity (81.4+/-1.1% at 360 degrees /s, p<0.001). In contrast, females did not demonstrate a significant relationship between H/Q ratio and isokinetic velocity (R=0.065, p=0.77) or a change in relative hamstrings strength as the speed increased (49.5+/-8.8% at 30 degrees /s; 51.0+/-5.7% at 360 degrees /s, p=0.84). Gender differences in isokinetic H/Q ratios were not observed at slower angular velocities. However, at high knee flexion/extension angular velocities, approaching those that occur during sports activities, significant gender differences were observed in the H/Q ratio. Females, unlike males, do not increase hamstrings to quadriceps torque ratios at velocities that approach those of functional activities.

Focal vibration of quadriceps muscle enhances leg power and decreases knee joint laxity in female volleyball players.

PubMed

Brunetti, O; Botti, F M; Roscini, M; Brunetti, A; Panichi, R; Filippi, G M; Biscarini, A; Pettorossi, V E

2012-12-01

This double-blind randomized controlled study aims at determining the effect of repeated muscle vibration (rMV) on explosive and reactive leg power and on knee laxity of female volleyball players. Eighteen voluntary volleyball athletes, belonging to the same senior regional level team (age=22.7 ± 3 years, height=180.3 ± 5 cm, mass= 64 ± 4 kg) were assigned to three groups (N.=6) for vibration on contracted quadriceps (VC), vibration on relaxed muscle (VR), and sham vibration (NV), respectively. Intervention consisted in 3 rMV sessions performed in 3 consecutive days. In each session, 100 Hz, 300-500 μm amplitude vibratory stimuli were bilaterally delivered to the quadriceps in three consecutive 10-minutes applications. Explosive and reactive leg power and knee joint laxity were evaluated 1 day before, and 1, 30, and 240 days after intervention. In VC group, explosive and reactive leg power increased respectively by ~16% and ~9% at 1 day, by ~19% and ~11% at 30 days and by ~26% and ~13% at 240 days, concomitantly knee laxity decreased by ~6%, ~15% and ~18% at the same times. These changes were significantly larger than in the other groups, in which leg power increment and knee joint laxity reduction remained close to ~3%, ~5% and ~10% at 1, 30 and 240 days, respectively. Combined bilateral voluntary contraction and rMV of the quadriceps muscles is a short-lasting, non-invasive technique that can significantly and persistently improve muscle performance and knee laxity in volleyball women players.

Tonic vibration reflex in spasticity, Parkinson's disease, and normal subjects

PubMed Central

Burke, David; Andrews, Colin J.; Lance, James W.

1972-01-01

The tonic vibration reflex (TVR) has been studied in the quadriceps and triceps surae muscles of 34 spastic, 15 Parkinsonism, and 10 normal subjects. The TVR of spasticity develops rapidly, reaching a plateau level within 2-4 sec of the onset of vibration. The tonic contraction was often preceded by a phasic spike which appeared to be a vibration-induced equivalent of the tendon jerk. The initial phasic spike was usually followed by a silent period, and induced clonus in some patients. No correlation was found between the shape of the TVR and the site of the lesion in the central nervous system. The TVR of normal subjects and patients with Parkinsonism developed slowly, starting some seconds after the onset of vibration, and reaching a plateau level in 20-60 sec. A phasic spike was recorded occasionally in these subjects, but the subsequent tonic contraction followed the usual time course. Muscle stretch increased the quadriceps TVR of all subjects, including those with spasticity in whom the quadriceps stretch reflex decreased with increasing stretch. It is suggested that this difference between the tonic vibration reflex and the tonic stretch reflex arises from the selective activation of spindle primary endings by vibration, while both the primary and the secondary endings are responsive to muscle stretch. The TVR could be potentiated by reinforcement in some subjects. Potentiation outlasted the reinforcing manoeuvre, and was most apparent at short muscle lengths. As muscle stretch increased, thus producing a larger TVR, the degree of potentiation decreased. It is therefore suggested that the effects of reinforcement result at least partially from the activation of the fusimotor system. Since reinforcement potentiated the TVR of patients with spinal spasticity in whom a prominent clasp-knife phenomenon could be demonstrated, it is suggested that the effects of reinforcement are mediated by a descending pathway that traverses the anterior quadrant of the spinal

Cyclic stretching of soft substrates induces spreading and growth

PubMed Central

Cui, Yidan; Hameed, Feroz M.; Yang, Bo; Lee, Kyunghee; Pan, Catherine Qiurong; Park, Sungsu; Sheetz, Michael

2015-01-01

In the body, soft tissues often undergo cycles of stretching and relaxation that may affect cell behaviour without changing matrix rigidity. To determine whether transient forces can substitute for a rigid matrix, we stretched soft pillar arrays. Surprisingly, 1–5% cyclic stretching over a frequency range of 0.01–10 Hz caused spreading and stress fibre formation (optimum 0.1 Hz) that persisted after 4 h of stretching. Similarly, stretching increased cell growth rates on soft pillars comparative to rigid substrates. Of possible factors linked to fibroblast growth, MRTF-A (myocardin-related transcription factor-A) moved to the nucleus in 2 h of cyclic stretching and reversed on cessation; but YAP (Yes-associated protein) moved much later. Knockdown of either MRTF-A or YAP blocked stretch-dependent growth. Thus, we suggest that the repeated pulling from a soft matrix can substitute for a stiff matrix in stimulating spreading, stress fibre formation and growth. PMID:25704457

Triceps stretch (image)

MedlinePlus

... shoulder. Hold for 10 to 20 seconds, then switch sides. Alternate method: raise your arm over your ... elbow. Hold for 10 to 20 seconds, then switch sides. You should feel either of these stretches ...

Stretch induced endothelin-1 secretion by adult rat astrocytes involves calcium influx via stretch-activated ion channels (SACs)

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

Ostrow, Lyle W., E-mail: lostrow1@jhmi.edu; Suchyna, Thomas M.; Sachs, Frederick

2011-06-24

Highlights: {yields} Endothelin-1 expression by adult rat astrocytes correlates with cell proliferation. {yields} Stretch-induced ET-1 is inhibited by GsMtx-4, a specific inhibitor of Ca{sup 2+} permeant SACs. {yields} The less specific SAC inhibitor streptomycin also inhibits ET-1 secretion. {yields} Stretch-induced ET-1 production depends on a calcium influx. {yields} SAC pharmacology may provide a new class of therapeutic agents for CNS pathology. -- Abstract: The expression of endothelins (ETs) and ET-receptors is often upregulated in brain pathology. ET-1, a potent vasoconstrictor, also inhibits the expression of astrocyte glutamate transporters and is mitogenic for astrocytes, glioma cells, neurons, and brain capillary endothelia.more » We have previously shown that mechanical stress stimulates ET-1 production by adult rat astrocytes. We now show in adult astrocytes that ET-1 production is driven by calcium influx through stretch-activated ion channels (SACs) and the ET-1 production correlates with cell proliferation. Mechanical stimulation using biaxial stretch (<20%) of a rubber substrate increased ET-1 secretion, and 4 {mu}M GsMTx-4 (a specific inhibitor of SACs) inhibited secretion by 30%. GsMTx-4 did not alter basal ET-1 levels in the absence of stretch. Decreasing the calcium influx by lowering extracellular calcium also inhibited stretch-induced ET-1 secretion without effecting ET-1 secretion in unstretched controls. Furthermore, inhibiting SACs with the less specific inhibitor streptomycin also inhibited stretch-induced ET-1 secretion. The data can be explained with a simple model in which ET-1 secretion depends on an internal Ca{sup 2+} threshold. This coupling of mechanical stress to the astrocyte endothelin system through SACs has treatment implications, since all pathology deforms the surrounding parenchyma.« less

The Human Immunodeficiency Virus 1 ASP RNA promotes viral latency by recruiting the Polycomb Repressor Complex 2 and promoting nucleosome assembly

PubMed Central

Zapata, Juan C.; Campilongo, Federica; Barclay, Robert A.; DeMarino, Catherine; Iglesias-Ussel, Maria D.; Kashanchi, Fatah; Romerio, Fabio

2017-01-01

Various epigenetic marks at the HIV-1 5′LTR suppress proviral expression and promote latency. Cellular antisense transcripts known as long noncoding RNAs (lncRNAs) recruit the polycomb repressor complex 2 (PRC2) to gene promoters, which catalyzes trimethylation of lysine 27 on histone H3 (H3K27me3), thus promoting nucleosome assembly and suppressing gene expression. We found that an HIV-1 antisense transcript expressed from the 3′LTR and encoding the antisense protein ASP promotes proviral latency. Expression of ASP RNA reduced HIV-1 replication in Jurkat cells. Moreover, ASP RNA expression promoted the establishment and maintenance of HIV-1 latency in Jurkat E4 cells. We show that this transcript interacts with and recruits PRC2 to the HIV-1 5′LTR, increasing accumulation of the suppressive epigenetic mark H3K27me3, while reducing RNA Polymerase II and thus proviral transcription. Altogether, our results suggest that the HIV-1 ASP transcript promotes epigenetic silencing of the HIV-1 5′LTR and proviral latency through the PRC2 pathway. PMID:28340355

Low-Latency Science Exploration of Planetary Bodies: How ISS Might Be Used as Part of a Low-Latency Analog Campaign for Human Exploration

NASA Technical Reports Server (NTRS)

Thronson, Harley; Valinia, Azita; Bleacher, Jacob; Eigenbrode, Jennifer; Garvin, Jim; Petro, Noah

2014-01-01

We suggest that the International Space Station be used to examine the application and validation of low-latency telepresence for surface exploration from space as an alternative, precursor, or potentially as an adjunct to astronaut "boots on the ground." To this end, controlled experiments that build upon and complement ground-based analog field studies will be critical for assessing the effects of different latencies (0 to 500 milliseconds), task complexity, and alternate forms of feedback to the operator. These experiments serve as an example of a pathfinder for NASA's roadmap of missions to Mars with low-latency telerobotic exploration as a precursor to astronaut's landing on the surface to conduct geological tasks.

Optimizing latency in Xilinx FPGA implementations of the GBT

NASA Astrophysics Data System (ADS)

Muschter, S.; Baron, S.; Bohm, C.; Cachemiche, J.-P.; Soos, C.

2010-12-01

The GigaBit Transceiver (GBT) [1] system has been developed to replace the Timing, Trigger and Control (TTC) system [2], currently used by LHC, as well as to provide data transmission between on-detector and off-detector components in future sLHC detectors. A VHDL version of the GBT-SERDES, designed for FPGAs, was released in March 2010 as a GBT-FPGA Starter Kit for future GBT users and for off-detector GBT implementation [3]. This code was optimized for resource utilization [4], as the GBT protocol is very demanding. It was not, however, optimized for latency — which will be a critical parameter when used in the trigger path. The GBT-FPGA Starter Kit firmware was first analyzed in terms of latency by looking at the separate components of the VHDL version. Once the parts which contribute most to the latency were identified and modified, two possible optimizations were chosen, resulting in a latency reduced by a factor of three. The modifications were also analyzed in terms of logic utilization. The latency optimization results were compared with measurement results from a Virtex 6 ML605 development board [5] equipped with a XC6VLX240T with speedgrade-1 and the package FF1156. Bit error rate tests were also performed to ensure an error free operation. The two final optimizations were analyzed for utilization and compared with the original code, distributed in the Starter Kit.

[Upper-limb work-related musculoskeletal disorders (UL-WMSDs) and latency of effect].

PubMed

Nicoletti, S; Battevi, N

2008-01-01

Trends in work-related upper limb musculoskeletal disorders appear to be in constant increase in industrialized countries. In Europe claims and compensation for these disorders have significantly increased. The aim of this study was to investigate the temporal relationship between the beginning of occupational exposure to repetitive movements and exertions of upper limbs, assessed through the OCRA index, and the manifestation of the disorders. Clinical and questionnaire information about 557 cases of UL-WMSDs in the upholstered furniture industry were analyzed in order to investigate the mean latency period of the disorders and to verify to what extent different levels of exposure influence the latency time. The latency of UL-WMSDs is influenced by the level of exposure to risk, measured by means of the OCRA index. Shorter latency times were found for wrist/hand tendonitis, with a mean latency time of 5.4 years and with a greater sensitivity to the level of exposure assessed with the OCRA index value. This might support a sort of predictive value with reference to other UL-WMSDs with longer latency. Probably a latency period of 12 years may be suggested as the cut-off limit to assess a causal relationship between tendon or canalicular WMISDs and occupational exposure to repetitive movements and exertions of upper limbs.

Importance of Stretching

MedlinePlus

... Kids and Teens Pregnancy and Childbirth Women Men Seniors Your Health Resources Healthcare Management End-of-Life ... pain. Always listen to your body. Stretching for seniors It’s all about maintaining that flexibility when it ...

Effects of different duration isometric contractions on tendon elasticity in human quadriceps muscles

PubMed Central

Kubo, Keitaro; Kanehisa, Hiroaki; Fukunaga, Tetsuo

2001-01-01

The present study aimed to investigate the influence of isometric training protocols with long- and short-duration contractions on the elasticity of human tendon structures in vivo. The elasticity was assessed through in vivo determination of the elongation (L) of the tendons and aponeuroses using ultrasonography, while the subjects performed ramp isometric exercise up to maximum voluntary contraction (MVC).Eight young males completed 12 weeks (4 days per week) of a unilateral isometric training programme on knee extensors, which consisted of two different combinations of contraction and relaxation times at 70 % MVC: one leg was trained using a short-duration protocol (3 sets of 50 repetitions of contraction for 1 s and relaxation for 2 s), and the other leg was trained using a long-duration protocol (4 sets of a combination of contraction for 20 s and relaxation for 1 min). The training volume per session, expressed as the integrated torque, was the same for the two protocols.Both protocols resulted in a significant increase in MVC: 31.8 ± 17.2 % for the short-duration protocol and 33.9 ± 14.4 % for the long-duration protocol. Moreover, the training produced significant increases in the muscle volume of the constituents of the quadriceps femoris, with similar relative gains for the two protocols: 7.4 ± 3.9 % for the short-duration protocol and 7.6 ± 4.3 % for the long-duration protocol.The short-duration protocol produced no significant change in L values at any of the force production levels. For the long-duration protocol, however, the L values above 550 N were significantly shorter after training. Analysis revealed that the group × test time interaction effect on tendon stiffness was significant. Stiffness increased significantly for the long-duration protocol, but not for the short-duration protocol.The present study demonstrates a greater increase in stiffness of human tendon structures following isometric training using longer duration contractions

Fault and Error Latency Under Real Workload: an Experimental Study. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Chillarege, Ram

1986-01-01

A practical methodology for the study of fault and error latency is demonstrated under a real workload. This is the first study that measures and quantifies the latency under real workload and fills a major gap in the current understanding of workload-failure relationships. The methodology is based on low level data gathered on a VAX 11/780 during the normal workload conditions of the installation. Fault occurrence is simulated on the data, and the error generation and discovery process is reconstructed to determine latency. The analysis proceeds to combine the low level activity data with high level machine performance data to yield a better understanding of the phenomena. A strong relationship exists between latency and workload and that relationship is quantified. The sampling and reconstruction techniques used are also validated. Error latency in the memory where the operating system resides was studied using data on the physical memory access. Fault latency in the paged section of memory was determined using data from physical memory scans. Error latency in the microcontrol store was studied using data on the microcode access and usage.

The effect of the stretching of PLA extruded films on their crystallinity and gas barrier properties

NASA Astrophysics Data System (ADS)

Guinault, A.; Menary, G. H.; Courgneau, C.; Griffith, D.; Ducruet, V.; Miri, V.; Sollogoub, C.

2011-05-01

Driven by environmental concerns, new polymers based on renewable resources are arriving on the market to replace conventional polymers, obtained from petroleum, for different applications like food packaging. One of the most prominent polymers among these materials is poly(lactic acid) (PLA), a biodegradable, thermoplastic, aliphatic polyester derived from renewable resources, such as corn starch (in the USA) or sugarcanes (in the rest of the world). However this polymer presents different disadvantages and especially low gas barrier properties [1]. Thermal crystallization can be used to increase its gas barrier properties but long times are necessary [2] and are not compatible with an industrial process. Another way to increase the gas barrier properties consists in stretching the film in order to increase its crystallinity and so its diffusion coefficient. We have prepared stretched PLA films with different stretch ratio and we have studied the effect of the stretching parameters on the gas barrier properties of PLA films. Finally we compared this process with the isothermal crystallization process by taking into account the crystallinity degree and the crystalline morphology.

Acute effect of constant torque and angle stretching on range of motion, muscle passive properties, and stretch discomfort perception.

PubMed

Cabido, Christian E T; Bergamini, Juliana C; Andrade, André G P; Lima, Fernando V; Menzel, Hans J; Chagas, Mauro H

2014-04-01

The aim of the present study was to compare the acute effects of constant torque (CT) and constant angle (CA) stretching exercises on the maximum range of motion (ROMmax), passive stiffness (PS), and ROM corresponding to the first sensation of tightness in the posterior thigh (FSTROM). Twenty-three sedentary men (age, 19-33 years) went through 1 familiarization session and afterward proceeded randomly to both CA and CT treatment stretching conditions, on separate days. An isokinetic dynamometer was used to analyze hamstring muscles during passive knee extension. The subjects performed 4 stretches of 30 seconds each with a 15-second interval between them. In the CA stretching, the subject reached a certain ROM (95% of ROMmax), and the angle was kept constant. However, in the CT stretching exercise, the volunteer reached a certain resistance torque (corresponding to 95% of ROMmax) and it was kept constant. The results showed an increase in ROMmax for both CA and CT (p < 0.001), but the increase was greater for CT than for CA (CA vs. CT in poststretching, p = 0.002). Although the PS decreased for both CA and CT (p < 0.001), the decrease was greater for CT than for CA (CA vs. CT in poststretching, p = 0.002). The FSTROM increased for both CA and CT, but the increase for CT was greater than that for CA (CA vs. CT in poststretching, p = 0.003). The greater increase in ROMmax for the CT stretch may be explained by greater changes in the biomechanical properties of the muscle-tendon unit and stretch tolerance, as indicated by the results of PS and FSTROM.

Optofluidic time-stretch microscopy: recent advances

NASA Astrophysics Data System (ADS)

Lei, Cheng; Nitta, Nao; Ozeki, Yasuyuki; Goda, Keisuke

2018-06-01

Flow cytometry is an indispensable method for valuable applications in numerous fields such as immunology, pathology, pharmacology, molecular biology, and marine biology. Optofluidic time-stretch microscopy is superior to conventional flow cytometry methods for its capability to acquire high-quality images of single cells at a high-throughput exceeding 10,000 cells per second. This makes it possible to extract copious information from cellular images for accurate cell detection and analysis with the assistance of machine learning. Optofluidic time-stretch microscopy has proven its effectivity in various applications, including microalga-based biofuel production, evaluation of thrombotic disorders, as well as drug screening and discovery. In this review, we discuss the principles and recent advances of optofluidic time-stretch microscopy.

Optofluidic time-stretch microscopy: recent advances

NASA Astrophysics Data System (ADS)

Lei, Cheng; Nitta, Nao; Ozeki, Yasuyuki; Goda, Keisuke

2018-04-01

Flow cytometry is an indispensable method for valuable applications in numerous fields such as immunology, pathology, pharmacology, molecular biology, and marine biology. Optofluidic time-stretch microscopy is superior to conventional flow cytometry methods for its capability to acquire high-quality images of single cells at a high-throughput exceeding 10,000 cells per second. This makes it possible to extract copious information from cellular images for accurate cell detection and analysis with the assistance of machine learning. Optofluidic time-stretch microscopy has proven its effectivity in various applications, including microalga-based biofuel production, evaluation of thrombotic disorders, as well as drug screening and discovery. In this review, we discuss the principles and recent advances of optofluidic time-stretch microscopy.

A randomized controlled comparison of stretching procedures for posterior shoulder tightness.

PubMed

McClure, Philip; Balaicuis, Jenna; Heiland, David; Broersma, Mary Ellen; Thorndike, Cheryl K; Wood, April

2007-03-01

Randomized controlled trial, To compare changes in shoulder internal rotation range of motion (ROM), for 2 stretching exercises, the "cross-body stretch" and the "sleeper stretch," in individuals with posterior shoulder tightness. Recently, some authors have expressed the belief that the sleeper stretch is better than the cross-body stretch to address glenohumeral posterior tightness because the scapula is stabilized. Fifty-four asymptomatic subjects (20 males, 34 females) participated in the study. The control group (n=24) consisted of subjects with a between-shoulder difference in internal rotation ROM of less than 10 degrees, whereas those subjects with more than a 10 degrees difference were randomly assigned to 1 of 2 intervention groups, the sleeper stretch group (n=15) or the cross-body stretch group (n=15). Shoulder internal rotation ROM, with the arm abducted to 90 degrees and scapula motion prevented, was measured before and after a 4-week intervention period. Subjects in the control group were asked not to engage in any new stretching activities, while subjects in the 2 stretching groups were asked to perform stretching exercises on the more limited side only, once daily for 5 repetitions, holding each stretch for 30 seconds. The improvements in internal rotation ROM for the subjects in the cross-body stretch group (mean +/- SD, 20.0 degrees +/- 12.9 degrees) were significantly greater than for the subjects in the control group (5.9 degrees +/- 9.4 degrees, P = .009). The gains in the sleeper stretch group (12.4 degrees +/- 10.4 degrees) were not significant compared to those of the control group (P = .586) and those of the cross-body stretch group (P = .148). The cross-body stretch in individuals with limited shoulder internal rotation ROM appears to be more effective than no stretching in controls without internal rotation asymmetry to improve shoulder internal rotation ROM. While the improvement in internal rotation from the cross-body stretch was

Training Effects of Alternated and Pulsed Currents on the Quadriceps Muscles of Athletes.

PubMed

Oliveira, Pedro; Modesto, Karenina Arrais Guida; Bottaro, Martim; Babault, Nicolas; Durigan, João Luiz Quagliotti

2018-05-22

The aim of the study was to evaluate the effects of 6 weeks training with different neuromuscular electrical stimulation (NMES) currents (medium alternated and low-frequency pulsed current) on muscle architecture and neuromuscular performance of competitive athletes. A double-blind controlled and randomized experimental study was carried out with 33 athletes (22.2±2.6 yrs, 74.7±9.8 kg, 176.8±6.0 cm), divided into 3 groups: mid-frequency current (MF, n=12), pulsed current (PC, n=11) and the control group (CG, n=10). Quadriceps maximal voluntary peak torque (PT) and corresponding vastus lateralis electromyographic activity, evoked torque (PT-NMES), vastus lateralis muscle thickness, fascicle length, pennation angle, and level of discomfort were assessed before and after the interventions. NMES training was performed 3 times per week and consisted of 18 sessions, 15 min/session, 6 s duration in each contraction interspersed with 18 s rest. After the training period, muscle thickness increased in the MF and PC groups (p<0.05). PT-NMES increased only in the PC group (p<0.05). All currents produced similar levels of discomfort (p>0.05). Quadriceps NMES training applied through alternated or pulsed currents produced similar effects in architecture and neuromuscular performance in competitive athletes. © Georg Thieme Verlag KG Stuttgart · New York.

Patellar tendon vibration reduces the increased facilitation from quadriceps to soleus in post-stroke hemiparetic individuals.

PubMed

Maupas, Eric; Dyer, Joseph-Omer; Melo, Sibele de Andrade; Forget, Robert

2017-09-01

Stimulation of the femoral nerve in healthy people can facilitate soleus H-reflex and electromyography (EMG) activity. In stroke patients, such facilitation of transmission in spinal pathways linking the quadriceps and soleus muscles is enhanced and related to co-activation of knee and ankle extensors while sitting and walking. Soleus H-reflex facilitation can be depressed by vibration of the quadriceps in healthy people, but the effects of such vibration have never been studied on the abnormal soleus facilitation observed in people after stroke. To determine whether vibration of the quadriceps can modify the enhanced heteronymous facilitation of the soleus muscle observed in people with spastic stroke after femoral nerve stimulation and compare post-vibration effects on soleus facilitation in control and stroke individuals. Modulation of voluntary soleus EMG activity induced by femoral nerve stimulation (2×motor threshold) was assessed before, during and after vibration of the patellar tendon in 10 healthy controls and 17 stroke participants. Voluntary soleus EMG activity was facilitated by femoral nerve stimulation in 4/10 (40%) controls and 11/17 (65%) stroke participants. The level of facilitation was greater in the stroke than control group. Vibration significantly reduced early heteronymous facilitation in both groups (50% of pre-vibration values). However, the delay in recovery of soleus facilitation after vibration was shorter for the stroke than control group. The control condition with the vibrator turned off had no effect on the modulation. Patellar tendon vibration can reduce the facilitation between knee and ankle extensors, which suggests effective presynaptic inhibition but decreased post-activation depression in the lower limb of people after chronic hemiparetic stroke. Further studies are warranted to determine whether such vibration could be used to reduce the abnormal extension synergy of knee and ankle extensors in people after hemiparetic

Changes in transverse relaxation time of quadriceps femoris muscles after active recovery exercises with different intensities.

PubMed

Mukaimoto, Takahiro; Semba, Syun; Inoue, Yosuke; Ohno, Makoto

2014-01-01

The purpose of this study was to examine the changes in the metabolic state of quadriceps femoris muscles using transverse relaxation time (T2), measured by muscle functional magnetic resonance (MR) imaging, after inactive or active recovery exercises with different intensities following high-intensity knee-extension exercise. Eight healthy men performed recovery sessions with four different conditions for 20 min after high-intensity knee-extension exercise on separate days. During the recovery session, the participants conducted a light cycle exercise for 20 min using a cycle (50%, 70% and 100% of the lactate threshold (LT), respectively: active recovery), and inactive recovery. The MR images of quadriceps femoris muscles were taken before the trial and after the recovery session every 30 min for 120 min. The percentage changes in T2 for the rectus femoris and vastus medialis muscles after the recovery session in 50% LT and 70% LT were significantly lower than those in either inactive recovery or 100% LT. There were no significant differences in those for vastus lateralis and vastus intermedius muscles among the four trials. The percentage changes in T2 of rectus femoris and vastus medialis muscles after the recovery session in 50% LT and 70% LT decreased to the values before the trial faster than those in either inactive recovery or 100% LT. Those of vastus lateralis and vastus intermedius muscles after the recovery session in 50% LT and 70% LT decreased to the values before the trial faster than those in 100% LT. Although the changes in T2 after active recovery exercises were not uniform in exercised muscles, the results of this study suggest that active recovery exercise with the intensities below LT are more effective to recover the metabolic state of quadriceps femoris muscles after intense exercise than with either intensity at LT or inactive recovery.

Research on low-latency MAC protocols for wireless sensor networks

NASA Astrophysics Data System (ADS)

He, Chenguang; Sha, Xuejun; Lee, Chankil

2007-11-01

Energy-efficient should not be the only design goal in MAC protocols for wireless sensor networks, which involve the use of battery-operated computing and sensing devices. Low-latency operation becomes the same important as energy-efficient in the case that the traffic load is very heavy or the real-time constrain is used in applications like tracking or locating. This paper introduces some causes of traditional time delays which are inherent in a multi-hops network using existing WSN MAC protocols, illuminates the importance of low-latency MAC design for wireless sensor networks, and presents three MACs as examples of low-latency protocols designed specially for sleep delay, wait delay and wakeup delay in wireless sensor networks, respectively. The paper also discusses design trade-offs with emphasis on low-latency and points out their advantages and disadvantages, together with some design considerations and suggestions for MAC protocols for future applications and researches.

The relevance of stretch intensity and position—a systematic review

PubMed Central

Apostolopoulos, Nikos; Metsios, George S.; Flouris, Andreas D.; Koutedakis, Yiannis; Wyon, Matthew A.

2015-01-01

Stretching exercises to increase the range of motion (ROM) of joints have been used by sports coaches and medical professionals for improving performance and rehabilitation. The ability of connective and muscular tissues to change their architecture in response to stretching is important for their proper function, repair, and performance. Given the dearth of relevant data in the literature, this review examined two key elements of stretching: stretch intensity and stretch position; and their significance to ROM, delayed onset muscle soreness (DOMS), and inflammation in different populations. A search of three databases, Pub-Med, Google Scholar, and Cochrane Reviews, identified 152 articles, which were subsequently categorized into four groups: athletes (24), clinical (29), elderly (12), and general population (87). The use of different populations facilitated a wider examination of the stretching components and their effects. All 152 articles incorporated information regarding duration, frequency and stretch position, whereas only 79 referred to the intensity of stretching and 22 of these 79 studies were deemed high quality. It appears that the intensity of stretching is relatively under-researched, and the importance of body position and its influence on stretch intensity, is largely unknown. In conclusion, this review has highlighted areas for future research, including stretch intensity and position and their effect on musculo-tendinous tissue, in relation to the sensation of pain, delayed onset muscle soreness, inflammation, as well as muscle health and performance. PMID:26347668

Effects of Neuromuscular Fatigue on Quadriceps Strength and Activation and Knee Biomechanics in Individuals Post-Anterior Cruciate Ligament Reconstruction and Healthy Adults.

PubMed

Thomas, Abbey C; Lepley, Lindsey K; Wojtys, Edward M; McLean, Scott G; Palmieri-Smith, Riann M

2015-12-01

Laboratory-based experiment using a pretest/posttest design. To determine the effects of neuromuscular fatigue on quadriceps strength and activation and sagittal and frontal plane knee biomechanics during dynamic landing following anterior cruciate ligament reconstruction (ACLR). Impaired quadriceps central activation occurs post-ACLR, likely altering lower extremity biomechanics. Neuromuscular fatigue similarly reduces volitional muscle activation and impairs neuromuscular control. Upon return to full activity post-ACLR, individuals likely concurrently experience quadriceps central activation deficits and neuromuscular fatigue, though the effects of fatigue on muscle strength and activation and biomechanics post-ACLR are unknown. Seventeen individuals 7 to 10 months post-ACLR and 16 controls participated. Quadriceps strength and central activation ratio were recorded prefatigue and postfatigue, which was induced via sets of double-leg squats. Knee biomechanics were recorded during a dynamic landing activity prefatigue and postfatigue. Both groups demonstrated smaller knee flexion (initial contact, P = .017; peak, P = .004) and abduction (initial contact, P = .005; peak, P = .009) angles postfatigue. The ACLR group had smaller peak knee flexion angles (P<.001) prefatigue and postfatigue than controls. Knee flexion moment was smaller in those post-ACLR than controls prefatigue (P<.001), but not postfatigue (P = .103). Controls had smaller knee flexion moments postfatigue (P = .001). Knee abduction moment was smaller in both groups postfatigue (P = .003). All participants demonstrated significantly lower strength (P<.001) and activation (P = .003) postfatigue. Impaired strength, central activation, and biomechanics were present postfatigue in both groups, suggesting that neuromuscular fatigue may increase noncontact ACL injury risk. However, these changes were not exaggerated in those post-ACLR, likely because they already demonstrated a stiff-legged landing strategy

Stretched Inertial Jets

NASA Astrophysics Data System (ADS)

Ghabache, Elisabeth; Antkowiak, Arnaud; Seon, Thomas; Villermaux, Emmanuel

2015-11-01

Liquid jets often arise as short-lived bursting liquid flows. Cavitation or impact-driven jets, bursting champagne bubbles, shaped-charge jets, ballistospores or drop-on-demand inkjet printing are a few examples where liquid jets are suddenly released. The trademark of all these discharge jets is the property of being stretched, due to the quenching injection. the present theoretical and experimental investigation, the structure of the jet flow field will be unraveled experimentally for a few emblematic occurrences of discharge jets. Though the injection markedly depends on each flow configuration, the jet velocity field will be shown to be systematically and rapidly attracted to the universal stretching flow z/t. The emergence of this inertial attractor actually only relies on simple kinematic ingredients, and as such is fairly generic. The universality of the jet velocity structure will be discussed.

Altered Energetics of Exercise Explain Risk of Rhabdomyolysis in Very Long-Chain Acyl-CoA Dehydrogenase Deficiency

PubMed Central

Diekman, E. F.; Visser, G.; Schmitz, J. P. J.; Nievelstein, R. A. J.; de Sain-van der Velden, M.; Wardrop, M.; Van der Pol, W. L.; Houten, S. M.; van Riel, N. A. W.; Takken, T.; Jeneson, J. A. L.

2016-01-01

Rhabdomyolysis is common in very long-chain acyl-CoA dehydrogenase deficiency (VLCADD) and other metabolic myopathies, but its pathogenic basis is poorly understood. Here, we show that prolonged bicycling exercise against a standardized moderate workload in VLCADD patients is associated with threefold bigger changes in phosphocreatine (PCr) and inorganic phosphate (Pi) concentrations in quadriceps muscle and twofold lower changes in plasma acetyl-carnitine levels than in healthy subjects. This result is consistent with the hypothesis that muscle ATP homeostasis during exercise is compromised in VLCADD. However, the measured rates of PCr and Pi recovery post-exercise showed that the mitochondrial capacity for ATP synthesis in VLCADD muscle was normal. Mathematical modeling of oxidative ATP metabolism in muscle composed of three different fiber types indicated that the observed altered energy balance during submaximal exercise in VLCADD patients may be explained by a slow-to-fast shift in quadriceps fiber-type composition corresponding to 30% of the slow-twitch fiber-type pool in healthy quadriceps muscle. This study demonstrates for the first time that quadriceps energy balance during exercise in VLCADD patients is altered but not because of failing mitochondrial function. Our findings provide new clues to understanding the risk of rhabdomyolysis following exercise in human VLCADD. PMID:26881790

Elastography Study of Hamstring Behaviors during Passive Stretching

PubMed Central

Le Sant, Guillaume; Ates, Filiz; Brasseur, Jean-Louis; Nordez, Antoine

2015-01-01

Introduction The mechanical properties of hamstring muscles are usually inferred from global passive torque/angle relationships, in combination with adjoining tissues crossing the joint investigated. Shear modulus measurement provides an estimate of changes in muscle-tendon stiffness and passive tension. This study aimed to assess the passive individual behavior of each hamstring muscle in different stretching positions using shear wave elastography. Methods/Results The muscle shear modulus of each hamstring muscle was measured during a standardized slow passive knee extension (PKE, 80% of maximal range of motion) on eighteen healthy male volunteers. Firstly, we assessed the reliability of the measurements. Results were good for semitendinosus (ST, CV: 8.9%-13.4%), semimembranosus (SM, CV: 10.3%-11.2%) and biceps femoris long-head (BF-lh, CV: 8.6%-13.3%), but not for biceps femoris short-head (BF-sh, CV: 20.3%-44.9%). Secondly, we investigated each reliable muscle in three stretch positions: 70°, 90° and 110° of hip flexion. The results showed different values of shear modulus for the same amount of perceived stretch, with the highest measurements in the high-flexed hip situation. Moreover, individual muscles displayed different values, with values increasing or BF-lh, SM and ST, respectively. The inter-subject variability was 35.3% for ST, 27.4% for SM and 30.2% for BF-lh. Conclusion This study showed that the hip needs to be high-flexed to efficiently tension the hamstrings, and reports a higher muscle-tendon stress tolerance at 110° of hip angle. In addition muscles have different passive behaviors, and future works will clarify if it can be linked with rate of injury. PMID:26418862

Massage therapy decreases pain and perceived fatigue after long-distance Ironman triathlon: a randomised trial.

PubMed

Nunes, Guilherme S; Bender, Paula Urio; de Menezes, Fábio Sprada; Yamashitafuji, Igor; Vargas, Valentine Zimermann; Wageck, Bruna

2016-04-01

Can massage therapy reduce pain and perceived fatigue in the quadriceps of athletes after a long-distance triathlon race (Ironman)? Randomised, controlled trial with concealed allocation, intention-to-treat analysis and blinded outcome assessors. Seventy-four triathlon athletes who completed an entire Ironman triathlon race and whose main complaint was pain in the anterior portion of the thigh. The experimental group received massage to the quadriceps, which was aimed at recovery after competition, and the control group rested in sitting. The outcomes were pain and perceived fatigue, which were reported using a visual analogue scale, and pressure pain threshold at three points over the quadriceps muscle, which was assessed using digital pressure algometry. The experimental group had significantly lower scores than the control group on the visual analogue scale for pain (MD -7 mm, 95% CI -13 to -1) and for perceived fatigue (MD -15 mm, 95% CI -21 to -9). There were no significant between-group differences for the pressure pain threshold at any of the assessment points. Massage therapy was more effective than no intervention on the post-race recovery from pain and perceived fatigue in long-distance triathlon athletes. Brazilian Registry of Clinical Trials, RBR-4n2sxr. Copyright © 2016 Australian Physiotherapy Association. Published by Elsevier B.V. All rights reserved.

Design of a new membrane stretching device

NASA Astrophysics Data System (ADS)

Shao, Yiran

Cell stretching device has been applied into the lab use for many years to help researchers study about the behavior of cells during the stretching process. Because the cell responses to the different mechanical stimuli, especially in the case of disease, the cell stretching device is a necessary tool to study the cell behavior in a controlled environment. However existing devices have limitations, such as too big to fit the culture chamber, unable to be observed during the stretching process and too expensive to fabricate. In this thesis, a new cell stretcher is designed to resolve these limitations. Many typical cell stretching devices only work under simple conditions. For instance they can only apply the strain on the cell in uniaxial or equibiaxial directions. On the other hand the environment of cells' survival is varying. Many new cell stretchers have been developed, which have the same property that cells can be stretched via the radical deformation of the elastomeric membrane. The aim of this new design is to create a cell stretching device that fits in general lab conditions. This device is designed to fit on a microscope to observe, as well as in the incubator. In addition, two small step motors are used to control the strain, adjust the frequency, and maintain the stability precisely. Problems such as the culture media leakage and the membrane breakage are solved by the usage of multiple materials for both the cell stretcher and the membrane. Based on the experimental results, this device can satisfy the requirements of target users with a reduced manufacturing cost. In the future, an auto-focus tracking function will be developed to allow real time observation of the cells' behavior.

Low-power low-latency MAC protocol for aeronautical applications

NASA Astrophysics Data System (ADS)

Sabater, Jordi; Kluge, Martin; Bovelli, Sergio; Schalk, Josef

2007-05-01

This paper describes asynchronous MAC (Medium Access Control) strategies based on the IEEE 802.15.4 physical layer for wireless aeronautical applications where low power and low latency are important requirements as well as security and data integrity. Sensor data is acquired and collected on request, by means of a mobile device, and later stored in a centralized database. In order to have the smallest power consumption the wireless sensor has to remain in deep sleep mode as long as possible and wake up and listen periodically for RF activity. If its unique ID is mentioned in the destination address field, the complete frame is received, processed and replied if necessary. If the detected packet is addressed to another sensor the reception will stop immediately and the wireless sensor will go into deep sleep mode again. Listening instead of sending actively does not 'pollute' the already crowded 2.45GHz spectrum, reduces collisions and increases security. The mobile data concentrator can not be synchronized with all the sensors installed in a distributed environment, therefore smart asynchronous data transmission strategies are needed to reduce latencies and increase throughput. For the considered application, sensors are independent of each other, simply share the medium and together with the data concentrator are organized in a star network topology. The centre of the star is the concentrator which is rarely in range. It coordinates and activates the wireless sensor nodes to collect the measured data.

mTOR-INDEPENDENT INDUCTION OF AUTOPHAGY IN TRABECULAR MESHWORK CELLS SUBJECTED TO BIAXIAL STRETCH

PubMed Central

Porter, Kristine M.; Jeyabalan, Nallathambi; Liton, Paloma B.

2014-01-01

The trabecular meshwork (TM) is part of a complex tissue that controls the exit of aqueous humor from the anterior chamber of the eye, and therefore helps maintaining intraocular pressure (IOP). Because of variations in IOP with changing pressure gradients and fluid movement, the TM and its contained cells undergo morphological deformations, resulting in distention and stretching. It is therefore essential for TM cells to continuously detect and respond to these mechanical forces and adapt their physiology to maintain proper cellular function and protect against mechanical injury. Here we demonstrate the activation of autophagy, a pro-survival pathway responsible for the degradation of long-lived proteins and organelles, in TM cells when subjected to biaxial static stretch (20 % elongation), as well as in high-pressure perfused eyes (30 mm Hg). Morphological and biochemical markers for autophagy found in the stretched cells include elevated LC3-II levels, increased autophagic flux, and the presence of autophagic figures in electron micrographs. Furthermore, our results indicate that the stretch-induced autophagy in TM cells occurs in an MTOR- and BAG3-independent manner. We hypothesize that activation of autophagy is part of the physiological response that allows TM cells to cope and adapt to mechanical forces. PMID:24583119

Temperature effect on the recovery process in stretched Bombyx mori silk fibers

NASA Astrophysics Data System (ADS)

Aksakal, Baki

2016-01-01

The recovery process in stretched Bombyx mori silk fibers at different strain levels from 3% to 17% was investigated at room conditions during long period of time from 5 min to 20 days and more. How the temperature affects the recovery process in the silk fibers stretched at room conditions was examined at temperatures from 25 to 125 °C. The results of the recovery process at 25 °C revealed that although the recovery process from strain values higher than 3% strain continued slowly which caused quite high remaining deformation, a complete recovery from 3% strain was observed after 3 days. However, better recovery process was observed with increasing temperature which led to lower remaining deformations. For instance, a complete recovery from 6% strain was observed after 144 h and 3 h for the recovery process at 100 °C and 125 °C, respectively which indicates an important result that the deformations induced by stretching the silk fibers up to 6% strain are reversible and increasing temperature affects the velocity of this process significantly. The recovery process expressed in the strain (ε) and logarithm time coordinates showed a linear dependence for which a linear equation was proposed. Thus, this linear equation enables to estimate the required time for a complete recovery from different strain levels and remaining deformation at any stage of the recovery at different temperatures. The ATR-FTIR spectra of the stretched silk fibers during the recovery process revealed some changes in the absorbance ratios and shifts in the positions of the bands assigned to Cα-C, N-H stretching vibrations, and the Amide III mode. It was suggested that new formation of the hydrogen bonds between polypeptide chains especially in amorphous regions and the changes in the intra-sheet hydrogen bonds in β-sheet crystalline regions greatly contribute to the recovery process.

Reconstruction of a quadriceps tendon tear using Polyvinylidene fluoride sutures and patellar screw fixation: A biomechanical study.

PubMed

Sellei, R M; Bauer, E; Hofman, M; Kobbe, P; Lichte, P; Garrison, R L; Pape, H C; Horst, K

2015-12-01

Acute quadriceps tendon tears are infrequent injuries requiring surgical treatment. Improved stability after surgical repair may allow for earlier weight-bearing and range of motion. Therefore, a new implant was tested and compared with the "gold standard", using transosseous sutures. Quadriceps tendon tears were constructed using a cadaveric model of 12 fresh matched-pair specimens (aged 61-97; mean age: 82 years). The biomechanical testing compared non-absorbable suture anchors (Polyvinylidene fluoride) versus transosseous absorbable sutures (Polydioxanon). Following anatomic reconstruction, the repaired specimens were loaded until they failed (testing machine: Hounsfield H10KM, Redhill, United Kingdom; maximum force: 1000 N; load speed: 25 mm/min; maximum test length: 150 mm; pre-load: 5 N). Values for load until tear displacement, maximum load until complete failure of the construct (pullout or breakage of the sutures or anchors) and stiffness of the reconstruction were recorded. The stiffness found in the Polyvinylidene fluoride reconstruction (mean 9.83 N/mm) (standard deviation (SD) 7.75) showed a significant increase compared to the Polydioxanon reconstruction (mean 6.66 N/mm (SD 3.32); P=0.045). Transosseous fixation showed comparable results to the suture anchor system. There was no significant difference found in the maximum load to tear displacement (PVDF: 290.88 N (SD 106.01) vs. PDS: 266.75 N (SD 82.61); P=0.358). Using the Polyvinylidene fluoride thread showed comparable results to the established method in reconstruction of ruptured quadriceps tendon. Stiffness of the Polyvinylidene fluoride thread reconstruction was even greater than Polydioxanon thread. Improved stiffness may facilitate healing and is suggested as clinical relevance in reconstruction. Copyright © 2015 Elsevier B.V. All rights reserved.

Multiple sleep latency measures in narcolepsy and behaviourally induced insufficient sleep syndrome.

PubMed

Marti, Isabelle; Valko, Philipp O; Khatami, Ramin; Bassetti, Claudio L; Baumann, Christian R

2009-12-01

Short mean latencies to the first epoch of non-rapid eye movement sleep stage 1 (NREM1) and the presence of >or= 2 sleep onset REM (SOREM) periods on multiple sleep latency test (MSLT) occur in both narcolepsy-cataplexy (NC) and behaviourally induced insufficient sleep syndrome (BIISS). It is not known whether specific MSLT findings help differentiate the two disorders. We analyzed MSLT data including sleep latencies to and between different sleep stages of 60 age-, gender- and body mass index (BMI)-matched subjects (hypocretin-deficient NC, actigraphy-confirmed BIISS, healthy controls: each 20). Mean latency (in minutes) to NREM1 sleep was significantly shorter in NC (1.8+/-1.5) than in BIISS (4.7+/-2.1, p<0.001) and controls (11.4+/-3.3, p<0.001). Mean latency to NREM2 sleep was similar in NC (8.6+/-4.7) and BIISS (8.1+/-2.7, p=0.64); latency to either NREM2 or rapid eye movement (REM) sleep (i.e., the sum of the sleep latency to NREM1 and the duration of the first NREM1 sleep sequence), however, was shorter in NC (4.4+/-2.9) than in BIISS (7.9+/-3.5, p<0.001). Referring to all naps with SOREM periods, the sequence NREM1-REM-NREM2 was more common (71%) in NC than in BIISS (15%, p<0.001), reflecting the shorter latency from NREM1 to NREM2 in BIISS (3.7+/-2.5) than in NC (6.1+/-5.9, p<0.001). Our findings show that both sleepiness (as measured by NREM1 sleep latency) and REM sleep propensity are higher in NC than in BIISS. Furthermore, our finding of frequent REM sleep prior to NREM2 sleep in NC is in line with the recent assumption of an insufficient NREM sleep intensity in NC. Together with detailed clinical interviews, sleep logs, actigraphy, and nocturnal polysomnography, mean sleep latencies to NREM1

Immediate effects of different types of stretching exercises on badminton jump smash.

PubMed

Jang, Hwi S; Kim, Daeho; Park, Jihong

2018-01-01

Since different types of stretching exercises may alter athletic performance, we compared the effects of three types of stretching exercises on badminton jump smash. Sixteen male collegiate badminton players performed one of three different stretching exercises in a counterbalanced order on different days. Static stretching had seven typical stretches, while dynamic stretching involved nine dynamic movements, and resistance dynamic stretching was performed with weighted vests and dumbbells. Before and after each stretching exercise, subjects performed 20 trials of jump smashes. Dependent measurements were the jump heights during jump smashes, velocities of jump-smashed shuttlecocks, and drop point of jump-smashed shuttlecocks. To test the effects of each stretching exercise, we performed mixed model ANOVAs and calculated between-time effect sizes (ES). Each stretching exercise improved the jump heights during jump smashes (type main effect: F(2,75)=1.19, P=0.31; static stretching: 22.1%, P<0.01, ES=0.98; dynamic stretching: 30.1%, P<0.01, ES=1.49; resistance dynamic stretching: 17.7%, P=0.03, ES=0.98) and velocities of jump-smashed shuttlecocks (type main effect: F(2,75)=2.18, P=0.12; static stretching: 5.7%, P=0.61, ES=0.39; dynamic stretching: 3.4%, P=0.94, ES=0.28; resistance dynamic stretching: 6%, P=0.50, ES=0.66). However, there were no differences among the stretching exercises for any measurement. The drop point of jump-smashed shuttlecocks did not change (interaction: F(2,75)=0.88, P=0.42). All stretching exercises improved badminton jump smash performance, but we could not determine the best protocol. Since badminton requires high-speed movement and explosive force, we suggest performing dynamic stretching or resistance dynamic stretching.

On the influence of latency estimation on dynamic group communication using overlays

NASA Astrophysics Data System (ADS)

Vik, Knut-Helge; Griwodz, Carsten; Halvorsen, Pål

2009-01-01

Distributed interactive applications tend to have stringent latency requirements and some may have high bandwidth demands. Many of them have also very dynamic user groups for which all-to-all communication is needed. In online multiplayer games, for example, such groups are determined through region-of-interest management in the application. We have investigated a variety of group management approaches for overlay networks in earlier work and shown that several useful tree heuristics exist. However, these heuristics require full knowledge of all overlay link latencies. Since this is not scalable, we investigate the effects that latency estimation techqniues have ton the quality of overlay tree constructions. We do this by evaluating one example of our group management approaches in Planetlab and examing how latency estimation techqniues influence their quality. Specifically, we investigate how two well-known latency estimation techniques, Vivaldi and Netvigator, affect the quality of tree building.

Mechanical stretching for tissue engineering: two-dimensional and three-dimensional constructs.

PubMed

Riehl, Brandon D; Park, Jae-Hong; Kwon, Il Keun; Lim, Jung Yul

2012-08-01

Mechanical cell stretching may be an attractive strategy for the tissue engineering of mechanically functional tissues. It has been demonstrated that cell growth and differentiation can be guided by cell stretch with minimal help from soluble factors and engineered tissues that are mechanically stretched in bioreactors may have superior organization, functionality, and strength compared with unstretched counterparts. This review explores recent studies on cell stretching in both two-dimensional (2D) and three-dimensional (3D) setups focusing on the applications of stretch stimulation as a tool for controlling cell orientation, growth, gene expression, lineage commitment, and differentiation and for achieving successful tissue engineering of mechanically functional tissues, including cardiac, muscle, vasculature, ligament, tendon, bone, and so on. Custom stretching devices and lab-specific mechanical bioreactors are described with a discussion on capabilities and limitations. While stretch mechanotransduction pathways have been examined using 2D stretch, studying such pathways in physiologically relevant 3D environments may be required to understand how cells direct tissue development under stretch. Cell stretch study using 3D milieus may also help to develop tissue-specific stretch regimens optimized with biochemical feedback, which once developed will provide optimal tissue engineering protocols.

Mechanical Stretching for Tissue Engineering: Two-Dimensional and Three-Dimensional Constructs

PubMed Central

Riehl, Brandon D.; Park, Jae-Hong; Kwon, Il Keun

2012-01-01

Mechanical cell stretching may be an attractive strategy for the tissue engineering of mechanically functional tissues. It has been demonstrated that cell growth and differentiation can be guided by cell stretch with minimal help from soluble factors and engineered tissues that are mechanically stretched in bioreactors may have superior organization, functionality, and strength compared with unstretched counterparts. This review explores recent studies on cell stretching in both two-dimensional (2D) and three-dimensional (3D) setups focusing on the applications of stretch stimulation as a tool for controlling cell orientation, growth, gene expression, lineage commitment, and differentiation and for achieving successful tissue engineering of mechanically functional tissues, including cardiac, muscle, vasculature, ligament, tendon, bone, and so on. Custom stretching devices and lab-specific mechanical bioreactors are described with a discussion on capabilities and limitations. While stretch mechanotransduction pathways have been examined using 2D stretch, studying such pathways in physiologically relevant 3D environments may be required to understand how cells direct tissue development under stretch. Cell stretch study using 3D milieus may also help to develop tissue-specific stretch regimens optimized with biochemical feedback, which once developed will provide optimal tissue engineering protocols. PMID:22335794

Dynamics of the OH stretching mode in crystalline Ba(ClO4)2.3H2O

NASA Astrophysics Data System (ADS)

Hutzler, Daniel; Brunner, Christian; Petkov, Petko St.; Heine, Thomas; Fischer, Sighart F.; Riedle, Eberhard; Kienberger, Reinhard; Iglev, Hristo

2018-02-01

The vibrational dynamics of the OH stretching mode in Ba(ClO4)2 trihydrate are investigated by means of femtosecond infrared spectroscopy. The sample offers plane cyclic water trimers in the solid phase that feature virtually no hydrogen bond interaction between the water molecules. Selective excitation of the symmetric and asymmetric stretching leads to fast population redistribution, while simultaneous excitation yields quantum beats, which are monitored via a combination tone that dominates the overtone spectrum. The combination of steady-state and time-resolved spectroscopy with quantum chemical simulations and general theoretical considerations gives indication of various aspects of symmetry breakage. The system shows a joint population lifetime of 8 ps and a long-lived coherence between symmetric and asymmetric stretching, which decays with a time constant of 0.6 ps.

Statistics of Advective Stretching in Three-dimensional Incompressible Flows

NASA Astrophysics Data System (ADS)

Subramanian, Natarajan; Kellogg, Louise H.; Turcotte, Donald L.

2009-09-01

We present a method to quantify kinematic stretching in incompressible, unsteady, isoviscous, three-dimensional flows. We extend the method of Kellogg and Turcotte (J. Geophys. Res. 95:421-432, 1990) to compute the axial stretching/thinning experienced by infinitesimal ellipsoidal strain markers in arbitrary three-dimensional incompressible flows and discuss the differences between our method and the computation of Finite Time Lyapunov Exponent (FTLE). We use the cellular flow model developed in Solomon and Mezic (Nature 425:376-380, 2003) to study the statistics of stretching in a three-dimensional unsteady cellular flow. We find that the probability density function of the logarithm of normalised cumulative stretching (log S) for a globally chaotic flow, with spatially heterogeneous stretching behavior, is not Gaussian and that the coefficient of variation of the Gaussian distribution does not decrease with time as t^{-1/2} . However, it is observed that stretching becomes exponential log S˜ t and the probability density function of log S becomes Gaussian when the time dependence of the flow and its three-dimensionality are increased to make the stretching behaviour of the flow more spatially uniform. We term these behaviors weak and strong chaotic mixing respectively. We find that for strongly chaotic mixing, the coefficient of variation of the Gaussian distribution decreases with time as t^{-1/2} . This behavior is consistent with a random multiplicative stretching process.

Importance of Patella, Quadriceps Forces, and Depthwise Cartilage Structure on Knee Joint Motion and Cartilage Response During Gait.

PubMed

Halonen, K S; Mononen, M E; Jurvelin, J S; Töyräs, J; Klodowski, A; Kulmala, J-P; Korhonen, R K

2016-07-01

In finite-element (FE) models of the knee joint, patella is often omitted. We investigated the importance of patella and quadriceps forces on the knee joint motion by creating an FE model of the subject's knee. In addition, depthwise strains and stresses in patellar cartilage with different tissue properties were determined. An FE model was created from subject's magnetic resonance images. Knee rotations, moments, and translational forces during gait were recorded in a motion laboratory and used as an input for the model. Three material models were implemented into the patellar cartilage: (1) homogeneous model, (2) inhomogeneous (arcadelike fibrils), and (3) random fibrils at the superficial zone, mimicking early stages of osteoarthritis (OA). Implementation of patella and quadriceps forces into the model substantially reduced the internal-external femoral rotations (versus without patella). The simulated rotations in the model with the patella matched the measured rotations at its best. In the inhomogeneous model, maximum principal stresses increased substantially in the middle zone of the cartilage. The early OA model showed increased compressive strains in the superficial and middle zones of the cartilage and decreased stresses and fibril strains especially in the middle zone. The results suggest that patella and quadriceps forces should be included in moment- and force-driven FE knee joint models. The results indicate that the middle zone has a major role in resisting shear forces in the patellar cartilage. Also, early degenerative changes in the collagen network substantially affect the cartilage depthwise response in the patella during walking.

Latency correction of event-related potentials between different experimental protocols

NASA Astrophysics Data System (ADS)

Iturrate, I.; Chavarriaga, R.; Montesano, L.; Minguez, J.; Millán, JdR

2014-06-01

Objective. A fundamental issue in EEG event-related potentials (ERPs) studies is the amount of data required to have an accurate ERP model. This also impacts the time required to train a classifier for a brain-computer interface (BCI). This issue is mainly due to the poor signal-to-noise ratio and the large fluctuations of the EEG caused by several sources of variability. One of these sources is directly related to the experimental protocol or application designed, and may affect the amplitude or latency of ERPs. This usually prevents BCI classifiers from generalizing among different experimental protocols. In this paper, we analyze the effect of the amplitude and the latency variations among different experimental protocols based on the same type of ERP. Approach. We present a method to analyze and compensate for the latency variations in BCI applications. The algorithm has been tested on two widely used ERPs (P300 and observation error potentials), in three experimental protocols in each case. We report the ERP analysis and single-trial classification. Main results. The results obtained show that the designed experimental protocols significantly affect the latency of the recorded potentials but not the amplitudes. Significance. These results show how the use of latency-corrected data can be used to generalize the BCIs, reducing the calibration time when facing a new experimental protocol.

A primary cell model of HIV-1 latency that uses activation through the T cell receptor and return to quiescence to establish latent infection

PubMed Central

Kim, Michelle; Hosmane, Nina N.; Bullen, C. Korin; Capoferri, Adam; Yang, Hung-Chih; Siliciano, Janet D.; Siliciano, Robert F.

2015-01-01

A mechanistic understanding of HIV-1 latency depends upon a model system that recapitulates the in vivo condition of latently infected, resting CD4+ T lymphocytes. Latency appears to be established after activated CD4+ T cells, the principal targets of HIV-1 infection, become productively infected and survive long enough to return to a resting memory state in which viral expression is inhibited by changes in the cellular environment. This protocol describes an ex vivo primary cell system that is generated under conditions that reflect the in vivo establishment of latency. Creation of these latency model cells takes 12 weeks and, once established, the cells can be maintained and used for several months. The resulting cell population contains both uninfected and latently infected cells. This primary cell model can be used to perform drug screens, study CTL responses to HIV-1, compare viral alleles, or to expand the ex vivo lifespan of cells from HIV-1 infected individuals for extended study. PMID:25375990

The effect of monitor raster latency on VEPs, ERPs and Brain-Computer Interface performance.

PubMed

Nagel, Sebastian; Dreher, Werner; Rosenstiel, Wolfgang; Spüler, Martin

2018-02-01

Visual neuroscience experiments and Brain-Computer Interface (BCI) control often require strict timings in a millisecond scale. As most experiments are performed using a personal computer (PC), the latencies that are introduced by the setup should be taken into account and be corrected. As a standard computer monitor uses a rastering to update each line of the image sequentially, this causes a monitor raster latency which depends on the position, on the monitor and the refresh rate. We technically measured the raster latencies of different monitors and present the effects on visual evoked potentials (VEPs) and event-related potentials (ERPs). Additionally we present a method for correcting the monitor raster latency and analyzed the performance difference of a code-modulated VEP BCI speller by correcting the latency. There are currently no other methods validating the effects of monitor raster latency on VEPs and ERPs. The timings of VEPs and ERPs are directly affected by the raster latency. Furthermore, correcting the raster latency resulted in a significant reduction of the target prediction error from 7.98% to 4.61% and also in a more reliable classification of targets by significantly increasing the distance between the most probable and the second most probable target by 18.23%. The monitor raster latency affects the timings of VEPs and ERPs, and correcting resulted in a significant error reduction of 42.23%. It is recommend to correct the raster latency for an increased BCI performance and methodical correctness. Copyright © 2017 Elsevier B.V. All rights reserved.

Modelling Transposition Latencies: Constraints for Theories of Serial Order Memory

ERIC Educational Resources Information Center

Farrell, Simon; Lewandowsky, Stephan

2004-01-01

Several competing theories of short-term memory can explain serial recall performance at a quantitative level. However, most theories to date have not been applied to the accompanying pattern of response latencies, thus ignoring a rich and highly diagnostic aspect of performance. This article explores and tests the error latency predictions of…

Transcriptome Analysis in Venom Gland of the Predatory Giant Ant Dinoponera quadriceps: Insights into the Polypeptide Toxin Arsenal of Hymenopterans

PubMed Central

Chong, Cheong-Meng; Leung, Siu Wai; Prieto-da-Silva, Álvaro R. B.; Havt, Alexandre; Quinet, Yves P.; Martins, Alice M. C.; Lee, Simon M. Y.; Rádis-Baptista, Gandhi

2014-01-01

Background Dinoponera quadriceps is a predatory giant ant that inhabits the Neotropical region and subdues its prey (insects) with stings that deliver a toxic cocktail of molecules. Human accidents occasionally occur and cause local pain and systemic symptoms. A comprehensive study of the D. quadriceps venom gland transcriptome is required to advance our knowledge about the toxin repertoire of the giant ant venom and to understand the physiopathological basis of Hymenoptera envenomation. Results We conducted a transcriptome analysis of a cDNA library from the D. quadriceps venom gland with Sanger sequencing in combination with whole-transcriptome shotgun deep sequencing. From the cDNA library, a total of 420 independent clones were analyzed. Although the proportion of dinoponeratoxin isoform precursors was high, the first giant ant venom inhibitor cysteine-knot (ICK) toxin was found. The deep next generation sequencing yielded a total of 2,514,767 raw reads that were assembled into 18,546 contigs. A BLAST search of the assembled contigs against non-redundant and Swiss-Prot databases showed that 6,463 contigs corresponded to BLASTx hits and indicated an interesting diversity of transcripts related to venom gene expression. The majority of these venom-related sequences code for a major polypeptide core, which comprises venom allergens, lethal-like proteins and esterases, and a minor peptide framework composed of inter-specific structurally conserved cysteine-rich toxins. Both the cDNA library and deep sequencing yielded large proportions of contigs that showed no similarities with known sequences. Conclusions To our knowledge, this is the first report of the venom gland transcriptome of the New World giant ant D. quadriceps. The glandular venom system was dissected, and the toxin arsenal was revealed; this process brought to light novel sequences that included an ICK-folded toxins, allergen proteins, esterases (phospholipases and carboxylesterases), and lethal

Reversal of Latency as Part of a Cure for HIV-1.

PubMed

Rasmussen, Thomas Aagaard; Tolstrup, Martin; Søgaard, Ole Schmeltz

2016-02-01

Here, the use of pharmacological agents to reverse HIV-1 latency will be explored as a therapeutic strategy towards a cure. However, while clinical trials of latency-reversing agents LRAs) have demonstrated their ability to increase production of latent HIV-1, such interventions have not had an effect on the size of the latent HIV-1 reservoir. Plausible explanations for this include insufficient host immune responses against virus-expressing cells, the presence of escape mutations in archived virus, or an insufficient scale of latency reversal. Importantly, these early studies of LRAs were primarily designed to investigate their ability to perturb the state of HIV-1 latency; using the absence of an impact on the size of the HIV-1 reservoir to discard their potential inclusion in curative strategies would be erroneous and premature. Copyright © 2015 Elsevier Ltd. All rights reserved.

Bruxism: Is There an Indication for Muscle-Stretching Exercises?

PubMed

Gouw, Simone; de Wijer, Anton; Creugers, Nico Hj; Kalaykova, Stanimira I

Bruxism is a common phenomenon involving repetitive activation of the masticatory muscles. Muscle-stretching exercises are a recommended part of several international guidelines for musculoskeletal disorders and may be effective in management of the jaw muscle activity that gives rise to bruxism. However, most studies of muscle-stretching exercises have mainly focused on their influence on performance (eg, range of motion, coordination, and muscle strength) of the limb or trunk muscles of healthy individuals or individuals with sports-related injuries. Very few have investigated stretching of the human masticatory muscles and none muscle-stretching exercises in the management of (sleep) bruxism. This article reviews the literature on muscle-stretching exercises and their potential role in the management of sleep bruxism or its consequences in the musculoskeletal system.

A cephalometric study of velar stretch in adolescent subjects.

PubMed

Simpson, R K; Colton, J

1980-01-01

Cephalometric x-rays were used to evaluate velar stretch in 20 normal adolescents during the production of /s/. Radiopaque markers were used so that the behaviors of both the anterior and posterior portions and the total velum cound be evaluated. Velar stretch was found in each of the subjects with the average stretch (15.19%) greater than the amount reported for 10-year-old subjects but less than the average stretch for adults. The correlation between amount of velar stretch and need ratio was not significant. The different stages of involution of adenoid tissue, which is characteristic of this age group, resulted in varying configurations of the naso-pharynx were postulated as one possible explanation for this unexpected finding. Normative data and clinical implications are presented.

Superelastic supercapacitors with high performances during stretching.

PubMed

Zhang, Zhitao; Deng, Jue; Li, Xueyi; Yang, Zhibin; He, Sisi; Chen, Xuli; Guan, Guozhen; Ren, Jing; Peng, Huisheng

2015-01-14

A fiber-shaped supercapacitor that can be stretched over 400% is developed by using two aligned carbon nanotube/polyaniline composite sheets as electrodes. A high specific capacitance of approximately 79.4 F g(-1) is well maintained after stretching at a strain of 300% for 5000 cycles or 100.8 F g(-1) after bending for 5000 cycles at a current density of 1 A g(-1). In particular, the high specific capacitance is maintained by 95.8% at a stretching speed as high as 30 mm s(-1). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Human Immunodeficiency Virus 1 ASP RNA promotes viral latency by recruiting the Polycomb Repressor Complex 2 and promoting nucleosome assembly.

PubMed

Zapata, Juan C; Campilongo, Federica; Barclay, Robert A; DeMarino, Catherine; Iglesias-Ussel, Maria D; Kashanchi, Fatah; Romerio, Fabio

2017-06-01

Various epigenetic marks at the HIV-1 5'LTR suppress proviral expression and promote latency. Cellular antisense transcripts known as long noncoding RNAs (lncRNAs) recruit the polycomb repressor complex 2 (PRC2) to gene promoters, which catalyzes trimethylation of lysine 27 on histone H3 (H3K27me3), thus promoting nucleosome assembly and suppressing gene expression. We found that an HIV-1 antisense transcript expressed from the 3'LTR and encoding the antisense protein ASP promotes proviral latency. Expression of ASP RNA reduced HIV-1 replication in Jurkat cells. Moreover, ASP RNA expression promoted the establishment and maintenance of HIV-1 latency in Jurkat E4 cells. We show that this transcript interacts with and recruits PRC2 to the HIV-1 5'LTR, increasing accumulation of the suppressive epigenetic mark H3K27me3, while reducing RNA Polymerase II and thus proviral transcription. Altogether, our results suggest that the HIV-1 ASP transcript promotes epigenetic silencing of the HIV-1 5'LTR and proviral latency through the PRC2 pathway. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

Arbitration in crossbar interconnect for low latency

DOEpatents

Ohmacht, Martin; Sugavanam, Krishnan

2013-02-05

A system and method and computer program product for reducing the latency of signals communicated through a crossbar switch, the method including using at slave arbitration logic devices associated with Slave devices for which access is requested from one or more Master devices, two or more priority vector signals cycled among their use every clock cycle for selecting one of the requesting Master devices and updates the respective priority vector signal used every clock cycle. Similarly, each Master for which access is requested from one or more Slave devices, can have two or more priority vectors and can cycle among their use every clock cycle to further reduce latency and increase throughput performance via the crossbar.

Workers' Extra-Nest Behavioral Changes During Colony Fission in Dinoponera quadriceps (Santschi).

PubMed

Medeiros, J; Araújo, A

2014-04-01

Ant colonies can reproduce by two strategies: independent foundation, wherein the queen starts a new colony alone, and dependent foundation, in which workers assist the queen. In the queenless species Dinoponera quadriceps (Santschi), the colony reproduces obligatorily by fission, a type of dependent foundation, but this process is not well understood. This study describes a colony fission event of D. quadriceps in the field and analyzes the influence of the fission process on workers' extra-nest behavior. Based on observations of workers outside the nest, five distinct stages were identified: monodomic stage, polydomic stage, split stage, conflict stage, and post-conflict stage. The colony was initially monodomic and then occupied a second nest before it split into two independent colonies, indicating a gradual and opportunistic dependent foundation. After the fission event, the daughter colony had aggressive conflicts with the parental colony, resulting in the latter's disappearance. Colony fission affected workers' extra-nest behavior by increasing the frequency of rubbing the gaster against the substrate (which probably has a chemical marking function) and by decreasing the frequency of foraging during the split stage. After the fission event, the number of foragers was halved and foragers remained nearer to the nest during extra-nest activity. The spatial closeness of the parental and daughter colonies led to competition that caused the extinction or migration of the parental colony. Intraspecific competition was indicated by foraging directionality at the colony level, whereby areas of neighbor colonies were avoided; this directionality was stronger while both colonies coexisted.

Effect of Tibial Posterior Slope on Knee Kinematics, Quadriceps Force, and Patellofemoral Contact Force After Posterior-Stabilized Total Knee Arthroplasty.

PubMed

Okamoto, Shigetoshi; Mizu-uchi, Hideki; Okazaki, Ken; Hamai, Satoshi; Nakahara, Hiroyuki; Iwamoto, Yukihide

2015-08-01

We used a musculoskeletal model validated with in vivo data to evaluate the effect of tibial posterior slope on knee kinematics, quadriceps force, and patellofemoral contact force after posterior-stabilized total knee arthroplasty. The maximum quadriceps force and patellofemoral contact force decreased with increasing posterior slope. Anterior sliding of the tibial component and anterior impingement of the anterior aspect of the tibial post were observed with tibial posterior slopes of at least 5° and 10°, respectively. Increased tibial posterior slope contributes to improved exercise efficiency during knee extension, however excessive tibial posterior slope should be avoided to prevent knee instability. Based on our computer simulation we recommend tibial posterior slopes of less than 5° in posterior-stabilized total knee arthroplasty. Copyright © 2015 Elsevier Inc. All rights reserved.

Latency reversal and viral clearance to cure HIV-1

PubMed Central

Margolis, David M.; Garcia, J. Victor; Hazuda, Daria J.; Haynes, Barton F.

2016-01-01

Research toward a cure for human immunodeficiency virus type 1 (HIV-1) infection has joined prevention and treatment efforts in the global public health agenda. A major approach to HIV eradication envisions antiretroviral suppression, paired with targeted therapies to enforce the expression of viral antigen from quiescent HIV-1 genomes, and immunotherapies to clear latent infection. These strategies are targeted to lead to viral eradication—a cure for AIDS. Paired testing of latency reversal and clearance strategies has begun, but additional obstacles to HIV eradication may emerge. Nevertheless, there is reason for optimism that advances in long-acting antiretroviral therapy and HIV prevention strategies will contribute to efforts in HIV cure research and that the implementation of these efforts will synergize to markedly blunt the effect of the HIV pandemic on society. PMID:27463679

Comparison of neuromuscular and quadriceps strengthening exercise in the treatment of varus malaligned knees with medial knee osteoarthritis: a randomised controlled trial protocol.

PubMed

Bennell, Kim L; Egerton, Thorlene; Wrigley, Tim V; Hodges, Paul W; Hunt, Michael; Roos, Ewa M; Kyriakides, Mary; Metcalf, Ben; Forbes, Andrew; Ageberg, Eva; Hinman, Rana S

2011-12-05

Osteoarthritis of the knee involving predominantly the medial tibiofemoral compartment is common in older people, giving rise to pain and loss of function. Many people experience progressive worsening of the disease over time, particularly those with varus malalignment and increased medial knee joint load. Therefore, interventions that can reduce excessive medial knee loading may be beneficial in reducing the risk of structural progression. Traditional quadriceps strengthening can improve pain and function in people with knee osteoarthritis but does not appear to reduce medial knee load. A neuromuscular exercise program, emphasising optimal alignment of the trunk and lower limb joints relative to one another, as well as quality of movement performance, while dynamically and functionally strengthening the lower limb muscles, may be able to reduce medial knee load. Such a program may also be superior to traditional quadriceps strengthening with respect to improved pain and physical function because of the functional and dynamic nature. This randomised controlled trial will investigate the effect of a neuromuscular exercise program on medial knee joint loading, pain and function in individuals with medial knee joint osteoarthritis. We hypothesise that the neuromuscular program will reduce medial knee load as well as pain and functional limitations to a greater extent than a traditional quadriceps strengthening program. 100 people with medial knee pain, radiographic medial compartment osteoarthritis and varus malalignment will be recruited and randomly allocated to one of two 12-week exercise programs: quadriceps strengthening or neuromuscular exercise. Each program will involve 14 supervised exercise sessions with a physiotherapist plus four unsupervised sessions per week at home. The primary outcomes are medial knee load during walking (the peak external knee adduction moment from 3D gait analysis), pain, and self-reported physical function measured at baseline and

Comparison of neuromuscular and quadriceps strengthening exercise in the treatment of varus malaligned knees with medial knee osteoarthritis: a randomised controlled trial protocol

PubMed Central

2011-01-01

Background Osteoarthritis of the knee involving predominantly the medial tibiofemoral compartment is common in older people, giving rise to pain and loss of function. Many people experience progressive worsening of the disease over time, particularly those with varus malalignment and increased medial knee joint load. Therefore, interventions that can reduce excessive medial knee loading may be beneficial in reducing the risk of structural progression. Traditional quadriceps strengthening can improve pain and function in people with knee osteoarthritis but does not appear to reduce medial knee load. A neuromuscular exercise program, emphasising optimal alignment of the trunk and lower limb joints relative to one another, as well as quality of movement performance, while dynamically and functionally strengthening the lower limb muscles, may be able to reduce medial knee load. Such a program may also be superior to traditional quadriceps strengthening with respect to improved pain and physical function because of the functional and dynamic nature. This randomised controlled trial will investigate the effect of a neuromuscular exercise program on medial knee joint loading, pain and function in individuals with medial knee joint osteoarthritis. We hypothesise that the neuromuscular program will reduce medial knee load as well as pain and functional limitations to a greater extent than a traditional quadriceps strengthening program. Methods/Design 100 people with medial knee pain, radiographic medial compartment osteoarthritis and varus malalignment will be recruited and randomly allocated to one of two 12-week exercise programs: quadriceps strengthening or neuromuscular exercise. Each program will involve 14 supervised exercise sessions with a physiotherapist plus four unsupervised sessions per week at home. The primary outcomes are medial knee load during walking (the peak external knee adduction moment from 3D gait analysis), pain, and self-reported physical function

Self-efficacy, pain, and quadriceps capacity at baseline predict changes in mobility performance over 2 years in women with knee osteoarthritis.

PubMed

Brisson, Nicholas M; Gatti, Anthony A; Stratford, Paul W; Maly, Monica R

2018-02-01

This study examined the extent to which baseline measures of quadriceps strength, quadriceps power, knee pain and self-efficacy for functional tasks, and their interactions, predicted 2-year changes in mobility performance (walking, stair ascent, stair descent) in women with knee osteoarthritis. We hypothesized that lesser strength, power and self-efficacy, and higher pain at baseline would each be independently associated with reduced mobility over 2 years, and each of pain and self-efficacy would interact with strength and power in predicting 2-year change in stair-climbing performance. This was a longitudinal, observational study of women with clinical knee osteoarthritis. At baseline and follow-up, mobility was assessed with the Six-Minute Walk Test, and stair ascent and descent tasks. Quadriceps strength and power, knee pain, and self-efficacy for functional tasks were also collected at baseline. Multiple linear regression examined the extent to which 2-year changes in mobility performances were predicted by baseline strength, power, pain, and self-efficacy, after adjusting for covariates. Data were analyzed for 37 women with knee osteoarthritis over 2 years. Lower baseline self-efficacy predicted decreased walking (β = 1.783; p = 0.030) and stair ascent (β = -0.054; p < 0.001) performances over 2 years. Higher baseline pain intensity/frequency predicted decreased walking performance (β = 1.526; p = 0.002). Lower quadriceps strength (β = 0.051; p = 0.015) and power (β = 0.022; p = 0.022) interacted with lesser self-efficacy to predict worsening stair ascent performance. Strategies to sustain or improve mobility in women with knee osteoarthritis must focus on controlling pain and boosting self-efficacy. In those with worse self-efficacy, developing knee muscle capacity is an important target.

Reliability of the Q Force; a mobile instrument for measuring isometric quadriceps muscle strength.

PubMed

Douma, K W; Regterschot, G R H; Krijnen, W P; Slager, G E C; van der Schans, C P; Zijlstra, W

2016-01-01

The ability to generate muscle strength is a pre-requisite for all human movement. Decreased quadriceps muscle strength is frequently observed in older adults and is associated with a decreased performance and activity limitations. To quantify the quadriceps muscle strength and to monitor changes over time, instruments and procedures with a sufficient reliability are needed. The Q Force is an innovative mobile muscle strength measurement instrument suitable to measure in various degrees of extension. Measurements between 110 and 130° extension present the highest values and the most significant increase after training. The objective of this study is to determine the test-retest reliability of muscle strength measurements by the Q Force in older adults in 110° extension. Forty-one healthy older adults, 13 males and 28 females were included in the study. Mean (SD) age was 81.9 (4.89) years. Isometric muscle strength of the Quadriceps muscle was assessed with the Q Force at 110° of knee extension. Participants were measured at two sessions with a three to eight day interval between sessions. To determine relative reliability, the intraclass correlation coefficient (ICC) was calculated. To determine absolute reliability, Bland and Altman Limits of Agreement (LOA) were calculated and t-tests were performed. Relative reliability of the Q Force is good to excellent as all ICC coefficients are higher than 0.75. Generally a large 95 % LOA, reflecting only moderate absolute reliability, is found as exemplified for the peak torque left leg of -18.6 N to 33.8 N and the right leg of -9.2 N to 26.4 N was between 15.7 and 23.6 Newton representing 25.2 % to 39.9 % of the size of the mean. Small systematic differences in mean were found between measurement session 1 and 2. The present study shows that the Q Force has excellent relative test-retest reliability, but limited absolute test-retest reliability. Since the Q Force is relatively cheap and mobile it is suitable for

Cessation of cyclic stretch induces atrophy of C2C12 myotubes.

PubMed

Soltow, Quinlyn A; Zeanah, Elizabeth H; Lira, Vitor A; Criswell, David S

2013-05-03

Cyclic stretch of differentiated myotubes mimics the loading pattern of mature skeletal muscle. We tested a cell culture model of disuse atrophy by the cessation of repetitive bouts of cyclic stretch in differentiated C2C12 myotubes. Myotubes were subjected to cyclic strain (12%, 0.7 Hz, 1 h/d) on collagen-I-coated Bioflex plates using a computer-controlled vacuum stretch apparatus (Flexcell Int.) for 2 (2dSTR) or 5 (5dSTR) consecutive days. Control cultures were maintained in the Bioflex plates without cyclic stretch for 2d or 5d. Additionally, some cultures were stretched for 2 d followed by cessation of stretch for 3d (2dSTR3dCES). Cyclic stretching (5dSTR) increased myotube diameter and overall myotube area by ~2-fold (P<0.05) compared to non-stretched controls, while cessation of stretch (2dSTR3dCES) resulted in ~80% smaller myotubes than 5dSTR cells, and 40-50% smaller than non-stretched controls (P<0.05). Further, the calpain-dependent cleavage products of αII-spectrin (150 kDa) and talin increased (3.5-fold and 2.2-fold, respectively; P<0.05) in 2dSTR3dCES myotubes, compared to non-stretched controls. The 1h cyclic stretching protocol acutely increased the phosphorylation of Akt (+4.5-fold; P<0.05) and its downstream targets, FOXO3a (+4.2-fold; P<0.05) and GSK-3β (+1.8-fold; P<0.05), which returned to baseline by 48 h after cessation of stretch. Additionally, nitric oxide production increased during stretch and co-treatment with the NOS inhibitor, l-NAME, inhibited the effects of stretch and cessation of stretch. We conclude that cessation of cyclic stretching causes myotube atrophy by activating calpains and decreasing activation of Akt. Stretch-induced myotube growth, as well as activation of atrophy signaling with cessation of stretch, are dependent on NOS activity. Copyright © 2013 Elsevier Inc. All rights reserved.

EMG and peak force responses to PNF stretching and the relationship between stretching-induced force deficits and bilateral deficits

PubMed Central

Cengiz, Asim

2015-01-01

[Purpose] The aim of the present study was to investigate the possibility of an interaction between stretching induced deficit (SFD) and bilateral deficits (BLD) during maximal voluntary isometric hand flexion under PNF stretch and no-stretch conditions through measurement of EMG and force production. [Subjects and Methods] Ten physically active male Caucasian students (age, 24.1±2.38 years; body mass, 79.48±11.40 kg; height, 174.15±0.8 cm) volunteered to participate in this study. EMG and force measurements of the subjects were recorded during either unilateral or bilateral 3-second maximal voluntary isometric hand flexion (MVC) against a force transducer. The paired sample t-test was used to examine the significance of differences among several conditions. Pearson product-moment correlation was used to evaluate the associations between different parameters. [Results] Stretching-induced deficits correlated with bilateral deficits in both force (r=0.85) and iEMG (r=0.89). PNF stretching caused significant decrements in the bilateral and unilateral conditions for both the right and left sides. [Conclusion] Since both force and iEMG decreases were observed in most measurements; it suggests there is a neural mechanism behinnd both the BLD and the SFD. PMID:25931696

STRETCH-DEPENDENT SENSITIZATION OF POST-JUNCTIONAL NEURAL EFFECTORS IN COLONIC MUSCLES

PubMed Central

Won, Kyung-Jong; Sanders, Kenton M.; Ward, Sean M.

2012-01-01

Background The colon undergoes distension-induced changes in motor activity as luminal contents or feces increases wall pressure. Input from enteric motor neurons regulates motility. Here we examined stretch-dependent responses in circular muscle strips of murine colon. Methods Length-ramps (6–31μm s−1) were applied in the axis of the circular muscle layer in a controlled manner until 5 mN isometric force was reached. Key Results Length-ramps produced transient membrane potential hyperpolarizations and attenuation of action potential (AP) complexes. Responses were reproducible when ramps were applied every 30s. Stretch-dependent hyperpolarization was blocked by TTX, suggesting AP-dependent release of inhibitory neurotransmitter(s). Atropine did not potentiate stretch-induced hyperpolarizations, but increased compliance of the circular layer. L-NNA inhibited stretch-dependent hyperpolarization and decreased muscle compliance, suggesting release of NO mediates stretch-dependent inhibition. Control membrane potential was restored by the NO donor SNP. Stretch-dependent hyperpolarizations were blocked by L-methionine, an inhibitor of stretch-dependent K+ (SDK) channels in colonic muscles. Loss of ICC, elicited by Kit neutralizing antibody, also inhibited responses to stretch. In presence of L-NNA and apamin, stretch responses became excitatory and were characterized by membrane depolarization and increased AP firing. A neurokinin-1 receptor antagonist inhibited this stretch-dependent increase in excitability. Conclusions & Inferences Our data show that stretch-dependent responses in colonic muscles require tonic firing of enteric inhibitory neurons, but reflex activation of neurons does not appear to be necessary. NO causes activation of SDK channels, and stretch of muscles further activates these channels, explaining the inhibitory response to stretch in colonic muscle strips. PMID:23279087

Development of anticipatory postural adjustments during locomotion in children.

PubMed

Hirschfeld, H; Forssberg, H

1992-08-01

1. Anticipatory postural adjustments were studied in children (6-14 yr of age) walking on a treadmill while pulling a handle. Electromyographs (EMGs) and movements were recorded from the left arm and leg. 2. Postural activity in the leg muscles preceded voluntary arm muscle activity in all age groups, including the youngest children (6 yr of age). The latency to both leg and arm muscle activity, from a triggering audio signal, decreased with age. 3. In older children the latency to both voluntary and postural activity was influenced by the phase of the step cycle. The shortest latency to the first activated postural muscle occurred during single support phase in combination with a long latency to arm muscle activity. 4. In the youngest children, there was no phase-dependent modulation of the latency to the activation of the postural muscles. The voluntary activity was delayed during the beginning of the support phase resulting in a long delay between leg and arm muscle activity. 5. The postural muscle activation pattern was modified in a phase-dependent manner in all children. Lateral gastrocnemius (LG) and hamstring muscles (HAM) were activated during the early support phase, whereas tibialis anterior (TA) and quadriceps (Q) muscles were activated during the late support phase and during the swing phase. However, in the 6-yr-old children, LG was also activated in the swing phase. LG was activated before the HAM activity in the youngest children but after HAM in 14-yr-old children and adults. 6. The occurrence of LG activity in postural responses before heel strike suggests an immature (nonplantigrade) gating of postural activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Modeling HSV-1 Latency in Human Embryonic Stem Cell-Derived Neurons

PubMed Central

Pourchet, Aldo; Modrek, Aram S.; Placantonakis, Dimitris G.; Mohr, Ian; Wilson, Angus C.

2017-01-01

Herpes simplex virus 1 (HSV-1) uses latency in peripheral ganglia to persist in its human host, however, recurrent reactivation from this reservoir can cause debilitating and potentially life-threatening disease. Most studies of latency use live-animal infection models, but these are complex, multilayered systems and can be difficult to manipulate. Infection of cultured primary neurons provides a powerful alternative, yielding important insights into host signaling pathways controlling latency. However, small animal models do not recapitulate all aspects of HSV-1 infection in humans and are limited in terms of the available molecular tools. To address this, we have developed a latency model based on human neurons differentiated in culture from an NIH-approved embryonic stem cell line. The resulting neurons are highly permissive for replication of wild-type HSV-1, but establish a non-productive infection state resembling latency when infected at low viral doses in the presence of the antivirals acyclovir and interferon-α. In this state, viral replication and expression of a late viral gene marker are not detected but there is an accumulation of the viral latency-associated transcript (LAT) RNA. After a six-day establishment period, antivirals can be removed and the infected cultures maintained for several weeks. Subsequent treatment with sodium butyrate induces reactivation and production of new infectious virus. Human neurons derived from stem cells provide the appropriate species context to study this exclusively human virus with the potential for more extensive manipulation of the progenitors and access to a wide range of preexisting molecular tools. PMID:28594343

Simulation Based Studies of Low Latency Teleoperations for NASA Exploration Missions

NASA Technical Reports Server (NTRS)

Gernhardt, Michael L.; Crues, Edwin Z.; Bielski, Paul; Dexter, Dan; Litaker, Harry L.; Chappell, Steven P.; Beaton, Kara H.; Bekdash, Omar S.

2017-01-01

Human exploration of Mars will involve both crewed and robotic systems. Many mission concepts involve the deployment and assembly of mission support assets prior to crew arrival on the surface. Some of these deployment and assembly activities will be performed autonomously while others will be performed using teleoperations. However, significant communications latencies between the Earth and Mars make teleoperations challenging. Alternatively, low latency teleoperations are possible from locations in Mars orbit like Mars' moons Phobos and Deimos. To explore these latency opportunities, NASA is conducting a series of studies to investigate the effects of latency on telerobotic deployment and assembly activities. These studies are being conducted in laboratory environments at NASA's Johnson Space Center (JSC), the Human Exploration Research Analog (HERA) at JSC and the NASA Extreme Environment Mission Operations (NEEMO) underwater habitat off the coast of Florida. The studies involve two human-in-the-loop interactive simulations developed by the NASA Exploration Systems Simulations (NExSyS) team at JSC. The first simulation investigates manipulation related activities while the second simulation investigates mobility related activities. The first simulation provides a simple real-time operator interface with displays and controls for a simulated 6 degree of freedom end effector. The initial version of the simulation uses a simple control mode to decouple the robotic kinematic constraints and a communications delay to model latency effects. This provides the basis for early testing with more detailed manipulation simulations planned for the future. Subjects are tested using five operating latencies that represent teleoperation conditions from local surface operations to orbital operations at Phobos, Deimos and ultimately high Martian orbit. Subject performance is measured and correlated with three distance-to-target zones of interest. Each zone represents a target

Analog Testing of Operations Concepts for Mitigation of Communication Latency During Human Space Exploration

NASA Technical Reports Server (NTRS)

Chappell, Steven P.; Abercromby, Andrew F.; Miller, Matthew J.; Halcon, Christopher; Gernhardt, Michael L.

2016-01-01

allow for presampling surveys enable efficient traverse execution and meaningful Mission Control Center (MCC) interaction across long communication latencies and can be done with minimal crew idle time. Imagery and information from the EVA crew that is transmitted real-time to the intravehicular (IV) crewmember(s) can be used to verify that exploration traverse plans are being executed correctly. That same data can be effectively used by MCC (across comm latency) to provide further instructions to the crew from a SBT on sampling priorities, additional tasks, and changes to the plan. Text / data capabilities are preferred over voice capabilities between MCC and IV when executing exploration traverse plans over communication latency. Autonomous crew planning tools can be effective at modifying existing plans if the objectives and constraints are clearly defined.

Enhancement of multispectral thermal infrared images - Decorrelation contrast stretching

NASA Technical Reports Server (NTRS)

Gillespie, Alan R.

1992-01-01

Decorrelation contrast stretching is an effective method for displaying information from multispectral thermal infrared (TIR) images. The technique involves transformation of the data to principle components ('decorrelation'), independent contrast 'stretching' of data from the new 'decorrelated' image bands, and retransformation of the stretched data back to the approximate original axes, based on the inverse of the principle component rotation. The enhancement is robust in that colors of the same scene components are similar in enhanced images of similar scenes, or the same scene imaged at different times. Decorrelation contrast stretching is reviewed in the context of other enhancements applied to TIR images.

The dinoponeratoxin peptides from the giant ant Dinoponera quadriceps display in vitro antitrypanosomal activity.

PubMed

Lima, Dânya Bandeira; Mello, Clarissa Perdigão; Bandeira, Izabel Cristina Justino; Pessoa Bezerra de Menezes, Ramon Róseo Paula; Sampaio, Tiago Lima; Falcão, Cláudio Borges; Morlighem, Jean-Étienne R L; Rádis-Baptista, Gandhi; Martins, Alice Maria Costa

2018-01-26

The crude venom of the giant ant Dinoponera quadriceps is a cocktail of polypeptides and organic compounds that shows antiparasitic effects against Trypanosoma cruzi, the causative agent of Chagas disease. In order to investigate the venom-derived components responsible for such antitrypanosomal activity, four dinoponeratoxins (DnTxs) were identified, namely M-PONTX-Dq3a, -Dq3b, -Dq3c and -Dq4e, that are diverse in size, net charge, hydrophobicity and propensity to interact with eukaryote cell membranes. These peptides were tested against epimastigote, trypomastigote and amastigote forms of benznidazole (Bz)-resistant Y strain of T. cruzi and in mammalian host cells. The M-PONTX-Dq3a and -Dq4e inhibited all developmental forms of T. cruzi, including amastigotes, the responsible form for the maintenance of infection on chronic phase of the disease. The M-PONTX-Dq3a showed the highest selectivity index (SI) (80) and caused morphological alterations in T. cruzi, as observed by scanning electron microscopy (SEM), and induced cell death through necrosis, as seen by multiparametric flow cytometry analysis with specific biochemical markers. Altogether, the D. quadriceps venom appears as a source for the prospection of trypanocidal peptides and the M-PONTX-Dq3a arises as a candidate among the dinoponeratoxin-related peptides in the development of compounds against Chagas disease.

Isokinetic Hamstrings:Quadriceps Ratios in Intercollegiate Athletes

PubMed Central

Fogarty, Tracey D.; Mahaffey, Brian L.

2001-01-01

Objective: To compare the differences in the concentric hamstrings:quadriceps (H:Q) ratio among athletes in different sports at 3 velocities. Design and Setting: We measured the H:Q ratio of both knees using the Biodex Pro Isokinetic Device. Subjects: Eighty-one male and female collegiate athletes. Measurements: We performed analyses for sport, velocity, and side of body for each sex. To compare the means of the concentric H:Q ratios for mean peak torque and mean total work, a 2 × 3 × 4 mixed-factorial analysis of variance was computed for women and a 2 × 2 × 3 mixed-factorial analysis of variance was computed for men. Results: We observed no significant interactions for men and women for the concentric H:Q ratio for mean peak torque. There was a significant mean difference among velocity conditions and a significant difference for men with respect to velocity. No significant differences were found for side of body or sport. Conclusions: The H:Q ratio increased as velocity increased. No differences existed for the H:Q ratio for sport or side of body. PMID:12937479

Three Fresh Exposures, Stretched Color

NASA Technical Reports Server (NTRS)

2004-01-01

This panoramic camera image from NASA's Mars Exploration Rover Opportunity has been processed using a technique known as a decorrelation stretch to exaggerate the colors. The area in the image includes three holes created inside 'Endurance Crater' by Opportunity's rock abrasion tool between sols 143 and 148 (June 18 and June 23, 2004). Because color variations are so subtle in the pictured area, stretched images are useful for discriminating color differences that can alert scientists to compositional and textural variations. For example, without the exaggeration, no color difference would be discernable among the tailings left behind after the grinding of these holes, but in this stretched image, the tailings around 'London' (top) appear more red than those of the other holes ('Virginia,' middle, and 'Cobble Hill,' bottom). Scientists believe that is because the rock abrasion tool sliced through two 'blueberries,' or spherules (visible on the upper left and upper right sides of the circle). When the blades break up these spherules, composed of mostly gray hematite, the result is a bright red powder. In this image, you can see the rock layers that made the team want to grind holes in each identified layer. The top layer is yellowish red, the middle is yellowish green and the lower layer is green. Another advantage to viewing this stretched image is the clear detail of the distribution of the rock abrasion tool tailings (heading down-slope) and the differences in rock texture. This image was created using the 753-, 535- and 432-nanometer filters.

On One-Dimensional Stretching Functions for Finite-Difference Calculations

NASA Technical Reports Server (NTRS)

Vinokur, M.

1980-01-01

The class of one dimensional stretching function used in finite difference calculations is studied. For solutions containing a highly localized region of rapid variation, simple criteria for a stretching function are derived using a truncation error analysis. These criteria are used to investigate two types of stretching functions. One is an interior stretching function, for which the location and slope of an interior clustering region are specified. The simplest such function satisfying the criteria is found to be one based on the inverse hyperbolic sine. The other type of function is a two sided stretching function, for which the arbitrary slopes at the two ends of the one dimensional interval are specified. The simplest such general function is found to be one based on the inverse tangent. The general two sided function has many applications in the construction of finite difference grids.

Lamellar Thickness and Stretching Temperature Dependency of Cavitation in Semicrystalline Polymers

PubMed Central

Wang, Yaotao; Jiang, Zhiyong; Fu, Lianlian; Lu, Ying; Men, Yongfeng

2014-01-01

Polybutene-1 (PB-1), a typical semicrystalline polymer, in its stable form I shows a peculiar temperature dependent strain-whitening behavior when being stretched at temperatures in between room temperature and melting temperature of the crystallites where the extent of strain-whitening weakens with the increasing of stretching temperature reaching a minima value followed by an increase at higher stretching temperatures. Correspondingly, a stronger strain-hardening phenomenon was observed at higher temperatures. The strain-whitening phenomenon in semicrystalline polymers has its origin of cavitation process during stretching. In this work, the effect of crystalline lamellar thickness and stretching temperature on the cavitation process in PB-1 has been investigated by means of combined synchrotron ultrasmall-angle and wide-angle X-ray scattering techniques. Three modes of cavitation during the stretching process can be identified, namely “no cavitation” for the quenched sample with the thinnest lamellae where only shear yielding occurred, “cavitation with reorientation” for the samples stretched at lower temperatures and samples with thicker lamellae, and “cavitation without reorientation” for samples with thinner lamellae stretched at higher temperatures. The mode “cavitation with reorientation” occurs before yield point where the plate-like cavities start to be generated within the lamellar stacks with normal perpendicular to the stretching direction due to the blocky substructure of the crystalline lamellae and reorient gradually to the stretching direction after strain-hardening. The mode of “cavitation without reorientation” appears after yield point where ellipsoidal shaped cavities are generated in those lamellae stacks with normal parallel to the stretching direction followed by an improvement of their orientation at larger strains. X-ray diffraction results reveal a much improved crystalline orientation for samples with thinner lamellae

Saccade Latency Indexes Exogenous and Endogenous Object-Based Attention

PubMed Central

Şentürk, Gözde; Greenberg, Adam S.; Liu, Taosheng

2016-01-01

Classic studies of object-based attention have utilized keypress responses as the main dependent measure. However, people typically make saccades to fixate important objects. Recent work has shown that attention may act differently when deployed covertly versus in advance of a saccade. We further investigated the link between saccades and attention by examining whether object-based effects can be observed for saccades. We adapted the classical double-rectangle cueing paradigm of Egly et al., (1994), and measured both the first saccade latency and keypress reaction time (RT) to a target that appeared at the end of one of the two rectangles. Our results showed that saccade latency exhibited higher sensitivity than RT in detecting effects of attention. We also assessed the generality of the attention effects by testing three types of cues: hybrid (predictive and peripheral), exogenous (non-predictive and peripheral), and endogenous (predictive and central). We found that both RT and saccade latency exhibited effects of both space-based and object-based attentional selection. However, saccade latency showed a more robust attentional modulation than RTs. For the exogenous cue, we observed a spatial inhibition-of-return along with an object-based effect, implying that object-based attention is independent of space-based attention. Overall, our results reveal an oculomotor correlate of object-based attention, suggesting that, in addition to spatial priority, object-level priority also affects saccade planning. PMID:27225468

Two-stage unified stretched-exponential model for time-dependence of threshold voltage shift under positive-bias-stresses in amorphous indium-gallium-zinc oxide thin-film transistors

NASA Astrophysics Data System (ADS)

Jeong, Chan-Yong; Kim, Hee-Joong; Hong, Sae-Young; Song, Sang-Hun; Kwon, Hyuck-In

2017-08-01

In this study, we show that the two-stage unified stretched-exponential model can more exactly describe the time-dependence of threshold voltage shift (ΔV TH) under long-term positive-bias-stresses compared to the traditional stretched-exponential model in amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs). ΔV TH is mainly dominated by electron trapping at short stress times, and the contribution of trap state generation becomes significant with an increase in the stress time. The two-stage unified stretched-exponential model can provide useful information not only for evaluating the long-term electrical stability and lifetime of the a-IGZO TFT but also for understanding the stress-induced degradation mechanism in a-IGZO TFTs.

Stretch That Budget!

ERIC Educational Resources Information Center

Walker, John R.

1976-01-01

Discusses ways in which industrial education teachers can stretch their budgets, which include reducing waste to a minimum, keeping an accurate and up-to-date inventory, trading surplus or excess materials with neighboring schools, and planning programs more carefully. Money-saving tips concerned with metals, plastics, woods, and printing are also…

Latency of TCP applications over the ATM-WAN using the GFR service category

NASA Astrophysics Data System (ADS)

Chen, Kuo-Hsien; Siliquini, John F.; Budrikis, Zigmantas

1998-10-01

The GFR service category has been proposed for data services in ATM networks. Since users are ultimately interested in data service that provide high efficiency and low latency, it is important to study the latency performance for data traffic of the GFR service category in an ATM network. Today much of the data traffic utilizes the TCP/IP protocol suite and in this paper we study through simulation the latency of TCP applications running over a wide-area ATM network utilizing the GFR service category using a realistic TCP traffic model. From this study, we find that during congestion periods the reserved bandwidth in GFR can improve the latency performance for TCP applications. However, due to TCP 'Slow Start' data segment generation dynamics, we show that a large proportion of TCP segments are discarded under network congestion even when the reserved bandwidth is equal to the average generated rate of user data. Therefore, a user experiences worse than expected latency performance when the network is congested. In this study we also examine the effects of segment size on the latency performance of TCP applications using the GFR service category.

Low latency messages on distributed memory multiprocessors

NASA Technical Reports Server (NTRS)

Rosing, Matthew; Saltz, Joel

1993-01-01

Many of the issues in developing an efficient interface for communication on distributed memory machines are described and a portable interface is proposed. Although the hardware component of message latency is less than one microsecond on many distributed memory machines, the software latency associated with sending and receiving typed messages is on the order of 50 microseconds. The reason for this imbalance is that the software interface does not match the hardware. By changing the interface to match the hardware more closely, applications with fine grained communication can be put on these machines. Based on several tests that were run on the iPSC/860, an interface that will better match current distributed memory machines is proposed. The model used in the proposed interface consists of a computation processor and a communication processor on each node. Communication between these processors and other nodes in the system is done through a buffered network. Information that is transmitted is either data or procedures to be executed on the remote processor. The dual processor system is better suited for efficiently handling asynchronous communications compared to a single processor system. The ability to send data or procedure is very flexible for minimizing message latency, based on the type of communication being performed. The test performed and the proposed interface are described.

An anterior cruciate ligament injury does not affect the neuromuscular function of the non-injured leg except for dynamic balance and voluntary quadriceps activation.

PubMed

Zult, Tjerk; Gokeler, Alli; van Raay, Jos J A M; Brouwer, Reinoud W; Zijdewind, Inge; Hortobágyi, Tibor

2017-01-01

The function of the anterior cruciate ligament (ACL) patients' non-injured leg is relevant in light of the high incidence of secondary ACL injuries on the contralateral side. However, the non-injured leg's function has only been examined for a selected number of neuromuscular outcomes and often without appropriate control groups. We measured a broad array of neuromuscular functions between legs of ACL patients and compared outcomes to age, sex, and physical activity matched controls. Thirty-two ACL-deficient patients (208 ± 145 days post-injury) and active and less-active controls (N = 20 each) participated in the study. We measured single- and multi-joint neuromuscular function in both legs in each group and expressed the overall neuromuscular function in each leg by calculating a mean z-score across all neuromuscular measures. A group by leg MANOVA and ANOVA were performed to examine group and leg differences for the selected outcomes. After an ACL injury, duration (-4.3 h/week) and level (Tegner activity score of -3.9) of sports activity decreased and was comparable to less-active controls. ACL patients showed bilateral impairments in the star excursion balance test compared to both control groups (P ≤ 0.004) and for central activation ratio compared to active controls (P ≤ 0.002). There were between-leg differences within each group for maximal quadriceps and hamstring strength, voluntary quadriceps activation, star excursion balance test performance, and single-leg hop distance (all P < 0.05), but there were no significant differences in quadriceps force accuracy and variability, knee joint proprioception, and static balance. Overall neuromuscular function (mean z-score) did not differ between groups, but ACL patients' non-injured leg displayed better neuromuscular function than the injured leg (P < 0.05). Except for poorer dynamic balance and reduced quadriceps activation, ACL patients had no bilateral neuromuscular deficits despite

Latency Requirements for Head-Worn Display S/EVS Applications

NASA Technical Reports Server (NTRS)

Bailey, Randall E.; Trey Arthur, J. J., III; Williams, Steven P.

2004-01-01

NASA s Aviation Safety Program, Synthetic Vision Systems Project is conducting research in advanced flight deck concepts, such as Synthetic/Enhanced Vision Systems (S/EVS), for commercial and business aircraft. An emerging thrust in this activity is the development of spatially-integrated, large field-of-regard information display systems. Head-worn or helmet-mounted display systems are being proposed as one method in which to meet this objective. System delays or latencies inherent to spatially-integrated, head-worn displays critically influence the display utility, usability, and acceptability. Research results from three different, yet similar technical areas flight control, flight simulation, and virtual reality are collectively assembled in this paper to create a global perspective of delay or latency effects in head-worn or helmet-mounted display systems. Consistent definitions and measurement techniques are proposed herein for universal application and latency requirements for Head-Worn Display S/EVS applications are drafted. Future research areas are defined.

Latency requirements for head-worn display S/EVS applications

NASA Astrophysics Data System (ADS)

Bailey, Randall E.; Arthur, Jarvis J., III; Williams, Steven P.

2004-08-01

NASA's Aviation Safety Program, Synthetic Vision Systems Project is conducting research in advanced flight deck concepts, such as Synthetic/Enhanced Vision Systems (S/EVS), for commercial and business aircraft. An emerging thrust in this activity is the development of spatially-integrated, large field-of-regard information display systems. Head-worn or helmet-mounted display systems are being proposed as one method in which to meet this objective. System delays or latencies inherent to spatially-integrated, head-worn displays critically influence the display utility, usability, and acceptability. Research results from three different, yet similar technical areas - flight control, flight simulation, and virtual reality - are collectively assembled in this paper to create a global perspective of delay or latency effects in head-worn or helmet-mounted display systems. Consistent definitions and measurement techniques are proposed herein for universal application and latency requirements for Head-Worn Display S/EVS applications are drafted. Future research areas are defined.

The 12-week progressive quadriceps resistance training improves muscle strength, exercise capacity and quality of life in patients with stable chronic heart failure.

PubMed

Jankowska, Ewa A; Wegrzynowska, Kinga; Superlak, Malgorzata; Nowakowska, Katarzyna; Lazorczyk, Malgorzata; Biel, Bartosz; Kustrzycka-Kratochwil, Dorota; Piotrowska, Katarzyna; Banasiak, Waldemar; Wozniewski, Marek; Ponikowski, Piotr

2008-10-30

Abnormalities in the skeletal musculature underlie exercise intolerance in chronic heart failure (CHF). We investigated, whether in CHF selective resistance training without accompanying aerobic regime favourably affects muscle strength, muscle mass and improves exercise capacity. Ten patients with stable ischaemic CHF in NYHA class III (9 men, age: 70+/-6 years [mean+/-SD], left ventricular ejection fraction: 30+/-5%, peak oxygen consumption [peak VO(2)]: 12.4+/-3.0 mL/min/kg) underwent the rehabilitation programme which consisted of a 12-week training phase (progressive resistance exercises restricted to the quadriceps muscles) followed by a 12-week detraining phase. All subjects completed a training phase of the programme with no adverse events. Resistance training markedly increased quadriceps strength (right leg: 260+/-34 vs. 352+/-28 N, left leg: 264+/-38 vs. 342+/-30 N, both p<0.01 - all comparisons: baseline vs. after training), but did not affect lean tissue mass of lower extremities (both p>0.2). It was accompanied by an improvement in clinical status (all NYHA III vs. all NYHA II, p<0.01), quality of life (Minnesota questionnaire: 44+/-15 vs. 33+/-18 points, p<0.05), exercise capacity assessed using a distance during 6-minute walk test (6MWT: 362+/-83 vs. 455+/-71 m, p<0.01), but not peak VO(2) (p>0.2). Plasma NT-proBNP remained unchanged during the training. At the end of detraining phase, only a partial improvement in quadriceps strength (p<0.05), a 6MWT distance (p<0.05) and NYHA class (p=0.07 vs. baseline) persisted. Applied resistance quadriceps training is safe in patients with CHF. It increases muscle strength, improves clinical status, exercise capacity, and quality of life.

Energy latency tradeoffs for medium access and sleep scheduling in wireless sensor networks

NASA Astrophysics Data System (ADS)

Gang, Lu

Wireless sensor networks are expected to be used in a wide range of applications from environment monitoring to event detection. The key challenge is to provide energy efficient communication; however, latency remains an important concern for many applications that require fast response. The central thesis of this work is that energy efficient medium access and sleep scheduling mechanisms can be designed without necessarily sacrificing application-specific latency performance. We validate this thesis through results from four case studies that cover various aspects of medium access and sleep scheduling design in wireless sensor networks. Our first effort, DMAC, is to design an adaptive low latency and energy efficient MAC for data gathering to reduce the sleep latency. We propose staggered schedule, duty cycle adaptation, data prediction and the use of more-to-send packets to enable seamless packet forwarding under varying traffic load and channel contentions. Simulation and experimental results show significant energy savings and latency reduction while ensuring high data reliability. The second research effort, DESS, investigates the problem of designing sleep schedules in arbitrary network communication topologies to minimize the worst case end-to-end latency (referred to as delay diameter). We develop a novel graph-theoretical formulation, derive and analyze optimal solutions for the tree and ring topologies and heuristics for arbitrary topologies. The third study addresses the problem of minimum latency joint scheduling and routing (MLSR). By constructing a novel delay graph, the optimal joint scheduling and routing can be solved by M node-disjoint paths algorithm under multiple channel model. We further extended the algorithm to handle dynamic traffic changes and topology changes. A heuristic solution is proposed for MLSR under single channel interference. In the fourth study, EEJSPC, we first formulate a fundamental optimization problem that provides tunable

Latency reversal and viral clearance to cure HIV-1.

PubMed

Margolis, David M; Garcia, J Victor; Hazuda, Daria J; Haynes, Barton F

2016-07-22

Research toward a cure for human immunodeficiency virus type 1 (HIV-1) infection has joined prevention and treatment efforts in the global public health agenda. A major approach to HIV eradication envisions antiretroviral suppression, paired with targeted therapies to enforce the expression of viral antigen from quiescent HIV-1 genomes, and immunotherapies to clear latent infection. These strategies are targeted to lead to viral eradication--a cure for AIDS. Paired testing of latency reversal and clearance strategies has begun, but additional obstacles to HIV eradication may emerge. Nevertheless, there is reason for optimism that advances in long-acting antiretroviral therapy and HIV prevention strategies will contribute to efforts in HIV cure research and that the implementation of these efforts will synergize to markedly blunt the effect of the HIV pandemic on society. Copyright © 2016, American Association for the Advancement of Science.

Latency of pupillary reflex to light stimulation and its relationship to aging.

DOT National Transportation Integrated Search

1965-09-01

A method is described for measuring pupillary contraction latency period regardless of initial absolute pupil diameter. Pupillary contraction latency period increases with age: the data presented show that the normal pupil, as usually found in health...

Using Arduino microcontroller boards to measure response latencies.

PubMed

Schubert, Thomas W; D'Ausilio, Alessandro; Canto, Rosario

2013-12-01

Latencies of buttonpresses are a staple of cognitive science paradigms. Often keyboards are employed to collect buttonpresses, but their imprecision and variability decreases test power and increases the risk of false positives. Response boxes and data acquisition cards are precise, but expensive and inflexible, alternatives. We propose using open-source Arduino microcontroller boards as an inexpensive and flexible alternative. These boards connect to standard experimental software using a USB connection and a virtual serial port, or by emulating a keyboard. In our solution, an Arduino measures response latencies after being signaled the start of a trial, and communicates the latency and response back to the PC over a USB connection. We demonstrated the reliability, robustness, and precision of this communication in six studies. Test measures confirmed that the error added to the measurement had an SD of less than 1 ms. Alternatively, emulation of a keyboard results in similarly precise measurement. The Arduino performs as well as a serial response box, and better than a keyboard. In addition, our setup allows for the flexible integration of other sensors, and even actuators, to extend the cognitive science toolbox.

Saccade latency reveals episodic representation of object color.

PubMed

Gordon, Robert D

2014-08-01

While previous studies suggest that identity, but not color, plays a role in episodic object representation, such studies have typically used tasks in which only identity is relevant, raising the possibility that the results reflect task demands, rather than the general principles that underlie object representation. In the present study, participants viewed a preview display containing one (Experiments 1 and 2) or two (Experiment 3) letters, then viewed a target display containing a single letter, in either the same or a different location. Participants executed an immediate saccade to fixate the target; saccade latency served as the dependent variable. In all experiments, saccade latencies were longer to fixate a target appearing in its previewed location, consistent with a bias to attend to new objects rather than to objects for which episodic representations are being maintained in visual working memory. The results of Experiment 3 further demonstrate, however, that changing target color eliminates these latency differences. The results suggest that color and identity are part of episodic representation even when not task relevant and that examining biases in saccade execution may be a useful approach to studying episodic representation.

Human Immunodeficiency Virus (HIV) Latency: The Major Hurdle in HIV Eradication

PubMed Central

Tyagi, Mudit; Bukrinsky, Michael

2012-01-01

Failure of highly active antiretroviral therapy to eradicate the human immunodeficiency virus (HIV), even in patients who suppress the virus to undetectable levels for many years, underscores the problems associated with fighting this infection. The existence of persistent infection in certain cellular and anatomical reservoirs appears to be the major hurdle in HIV eradication. The development of therapeutic interventions that eliminate or limit the latent viral pools or prevent the reemergence of the viruses from producing cells will therefore be required to enhance the effectiveness of current antiretroviral strategies. To achieve this goal, there is a pressing need to understand HIV latency at the molecular level to design novel and improved therapies to either eradicate HIV or find a functional cure in which patients could maintain a manageable viral pool without AIDS in the absence of antiretroviral therapy. The integrated proviral genome remains transcriptionally silent for a long period in certain subsets of T cells. This ability to infect cells latently helps HIV to establish a persistent infection despite strong humoral and cellular immune responses against the viral proteins. The main purpose of this report is to provide a general overview of the HIV latency. We will describe the hurdles being faced in eradicating latent HIV proviruses. We will also briefly discuss the ongoing strategies aimed toward curing HIV infection. PMID:22692576

Rounded stretched exponential for time relaxation functions.

PubMed

Powles, J G; Heyes, D M; Rickayzen, G; Evans, W A B

2009-12-07

A rounded stretched exponential function is introduced, C(t)=exp{(tau(0)/tau(E))(beta)[1-(1+(t/tau(0))(2))(beta/2)]}, where t is time, and tau(0) and tau(E) are two relaxation times. This expression can be used to represent the relaxation function of many real dynamical processes, as at long times, t>tau(0), the function converges to a stretched exponential with normalizing relaxation time, tau(E), yet its expansion is even or symmetric in time, which is a statistical mechanical requirement. This expression fits well the shear stress relaxation function for model soft soft-sphere fluids near coexistence, with tau(E)

Gum chewing improves swallow frequency and latency in Parkinson patients: a preliminary study.

PubMed

South, Angela R; Somers, Stephanie M; Jog, Mandar S

2010-04-13

Reduced swallowing frequency affects secretion management in Parkinson disease (PD). Gum chewing increases saliva flow and swallow frequency. This study uses chewing gum to modify swallow frequency and latency between swallows in patients with PD. 1) Assess the frequency and latency of swallow at baseline (BL), during gum chewing (GC), and post gum chewing (PGC) for participants with PD (stage 2-4) nonsymptomatic for prandial dysphagia; and 2) assess carryover after gum is expectorated. Twenty participants were studied across 3 tasks, each of 5 minutes in duration: BL, GC, and PGC. Respiratory and laryngeal signals were continuously recorded using PowerLab (version 5.5.5; ADI Instruments, Castle Hill, Australia). Frequency and latency of swallow events were calculated. Differences (analysis of variance) are reported for frequency (p < 0.000001) and latency (p < 0.000001). Swallow frequency (mean +/- SD) increased during GC (14.95 +/- 3.02) compared with BL (3.1 +/- 2.85) and PGC (7.0 +/- 2.57). Latency in seconds (mean +/- SD) decreased during GC (24.1 +/- 4.174) and increased with BL (131.8 +/- 59.52) and PGC (mean = 60.74 +/- 25.25). Intertask comparisons (t test) found differences in swallow frequency and latency between tasks: BL vs GC (p < 0.0001, p < 0.0001), BL vs PGC (p < 0.0011, p < 0.0009), and GC vs PGC (p < 0.0001, p < 0.0002), respectively. Post hoc analysis showed carryover to 5.317 minutes. Modifying sensorimotor input by chewing gum alters frequency and latency of swallowing and may be an effective strategy for secretion management in Parkinson disease. This study provides Class III evidence that chewing gum increases swallow frequency and decreases latency of swallowing in an experiment in patients with stage 2 to 4 Parkinson disease who are nonsymptomatic for significant prandial dysphagia.

A Japanese Stretching Intervention Can Modify Lumbar Lordosis Curvature.

PubMed

Kadono, Norio; Tsuchiya, Kazushi; Uematsu, Azusa; Kamoshita, Hiroshi; Kiryu, Kazunori; Hortobágyi, Tibor; Suzuki, Shuji

2017-08-01

Eighteen healthy male adults were assigned to either an intervention or control group. Isogai dynamic therapy (IDT) is one of Japanese stretching interventions and has been practiced for over 70 years. However, its scientific quantitative evidence remains unestablished. The objective of this study was to determine whether IDT could modify lumbar curvature in healthy young adults compared with stretching exercises used currently in clinical practice. None of previous studies have provided data that conventional stretching interventions could modify spinal curvatures. However, this study provides the first evidence that a specific form of a Japanese stretching intervention can acutely modify the spinal curvatures. We compared the effects of IDT, a Japanese stretching intervention (n=9 males), with a conventional stretching routine (n=9 males) used widely in clinics to modify pelvic tilt and lumbar lordosis (LL) angle. We measured thoracic kyphosis (TK) and LL angles 3 times during erect standing using the Spinal Mouse before and after each intervention. IDT consisted of: (1) hip joint correction, (2) pelvic tilt correction, (3) lumbar alignment correction, and (4) squat exercise stretch. The control group performed hamstring stretches while (1) standing and (2) sitting. IDT increased LL angle to 25.1 degrees (±5.9) from 21.2 degrees (±6.9) (P=0.047) without changing TK angle (pretest: 36.8 degrees [±6.9]; posttest: 36.1 degrees [±6.5]) (P=0.572). The control group showed no changes in TK (P=0.819) and LL angles (P=0.744). IDT can thus be effective for increasing LL angle, hence anterior pelvic tilt. Such modifications could ameliorate low back pain and improve mobility in old adults with an unfavorable pelvic position.

Muscle Activation Profiles and Co-Activation of Quadriceps and Hamstring Muscles around Knee Joint in Indian Primary Osteoarthritis Knee Patients.

PubMed

Sharma, Sanjeev Kumar; Yadav, Shiv Lal; Singh, U; Wadhwa, Sanjay

2017-05-01

Osteoarthritis (OA) of knee is a common joint disease. It is associated with reduced knee joint stability due to impaired quadriceps strength, pain, and an altered joint structure. There is altered muscle activation in knee OA patients, which interferes with normal load distribution around the knee and facilitates disease progression. Our primary aim was to determine activation patterns of the muscles i.e., quadriceps and hamstrings in knee OA patients during walking. We also studied co-activation of muscles around knee joint in primary OA knee patients including directed medial and lateral co-contractions. This observational study was done at Department of Physical Medicine and Rehabilitation, All India Institute of Medical Sciences, New Delhi, India. Fourty-four patients with medial compartment primary knee OA were included in study after satisfying inclusion and exclusion criteria. All the patients were assessed for mean, peak and integrated Root Mean Square (RMS), EMG values, muscle activation patterns and co-activation of muscles around knee joint by surface Electromyography (EMG) analysis of Vastus Medialis Obliques (VMO), Vastus Lateralis (VL), Semitendinosus (SMT) and Biceps Femoris (BF) muscles during gait cycle. The EMG waveform for each muscle was amplitude normalized and time normalized to 100% of gait cycle and plotted on graph. Quantitative variables were assessed for normal distribution and accordingly mean±SD or median (range), as appropriate, was computed. For primary OA knee, mean age 61±5 years, mean weight 63.7±10.1 kg, mean height 153.9±7.2 cm, and mean Body Mass Index (BMI) 26.8±3.0 kg/m 2 was found. The muscle activity of hamstrings (SMT muscle and BF) was increased during midstance, late stance and early swing phase of gait cycle as compared to quadriceps (VMO and VL) muscle activity respectively, suggesting co-contraction of opposing muscles around knee joint. Patients with knee OA walk with increased hamstring muscle activity (during

Muscle Activation Profiles and Co-Activation of Quadriceps and Hamstring Muscles around Knee Joint in Indian Primary Osteoarthritis Knee Patients

PubMed Central

Yadav, Shiv Lal; Singh, U; Wadhwa, Sanjay

2017-01-01

Introduction Osteoarthritis (OA) of knee is a common joint disease. It is associated with reduced knee joint stability due to impaired quadriceps strength, pain, and an altered joint structure. There is altered muscle activation in knee OA patients, which interferes with normal load distribution around the knee and facilitates disease progression. Aim Our primary aim was to determine activation patterns of the muscles i.e., quadriceps and hamstrings in knee OA patients during walking. We also studied co-activation of muscles around knee joint in primary OA knee patients including directed medial and lateral co-contractions. Materials and Methods This observational study was done at Department of Physical Medicine and Rehabilitation, All India Institute of Medical Sciences, New Delhi, India. Fourty-four patients with medial compartment primary knee OA were included in study after satisfying inclusion and exclusion criteria. All the patients were assessed for mean, peak and integrated Root Mean Square (RMS), EMG values, muscle activation patterns and co-activation of muscles around knee joint by surface Electromyography (EMG) analysis of Vastus Medialis Obliques (VMO), Vastus Lateralis (VL), Semitendinosus (SMT) and Biceps Femoris (BF) muscles during gait cycle. The EMG waveform for each muscle was amplitude normalized and time normalized to 100% of gait cycle and plotted on graph. Quantitative variables were assessed for normal distribution and accordingly mean±SD or median (range), as appropriate, was computed. Results For primary OA knee, mean age 61±5 years, mean weight 63.7±10.1 kg, mean height 153.9±7.2 cm, and mean Body Mass Index (BMI) 26.8±3.0 kg/m2 was found. The muscle activity of hamstrings (SMT muscle and BF) was increased during midstance, late stance and early swing phase of gait cycle as compared to quadriceps (VMO and VL) muscle activity respectively, suggesting co-contraction of opposing muscles around knee joint. Conclusion Patients with knee

Saccade latency indexes exogenous and endogenous object-based attention.

PubMed

Şentürk, Gözde; Greenberg, Adam S; Liu, Taosheng

2016-10-01

Classic studies of object-based attention have utilized keypress responses as the main dependent measure. However, people typically make saccades to fixate important objects. Recent work has shown that attention may act differently when it is deployed covertly versus in advance of a saccade. We further investigated the link between saccades and attention by examining whether object-based effects can be observed for saccades. We adapted the classical double-rectangle cueing paradigm of Egly, Driver, and Rafal (1994), and measured both the first saccade latency and the keypress reaction time (RT) to a target that appeared at the end of one of the two rectangles. Our results showed that saccade latencies exhibited higher sensitivity than did RTs for detecting effects of attention. We also assessed the generality of the attention effects by testing three types of cues: hybrid (predictive and peripheral), exogenous (nonpredictive and peripheral), and endogenous (predictive and central). We found that both RTs and saccade latencies exhibited effects of both space-based and object-based attentional selection. However, saccade latencies showed a more robust attentional modulation than RTs. For the exogenous cues, we observed a spatial inhibition of return along with an object-based effect, implying that object-based attention is independent of space-based attention. Overall, our results revealed an oculomotor correlate of object-based attention, suggesting that, in addition to spatial priority, object-level priority also affects saccade planning.

Stretched size of atrial septal defect predicted by intracardiac echocardiography.

PubMed

Lin, Ming-Chih; Fu, Yun-Ching; Jan, Sheng-Ling; Ho, Chi-Lin; Hwang, Betau

2010-01-01

The stretched size of an atrial septal defect (ASD) is important for device selection during transcatheter closure. However, balloon sizing carries potential risks such as hypotension, bradycardia, or laceration of the atrial septum. The aim of the present study was to investigate the accuracy of the predicted stretched size of ASD by intracardiac echocardiography (ICE). From December 2004 to November 2007, 136 consecutive patients with single secundum type ASD undergoing transcatheter closure of their defect using the Amplatzer septal occluder under ICE guidance were enrolled for analysis. There were 43 males and 93 females. The age ranged from 2.2 to 79.1 years with a median age of 13.4 years. The body weight ranged from 12.1 to 93.2 kg with a median body weight of 45.8 kg. The stretched size of ASD measured by a sizing plate was considered as the standard. ASD sizes measured by ICE in bicaval and short-axis views predicted the stretched size by formulae derived from linear regressions. The predicted stretched sizes obtained using 2 formulae, 1.34 x radicalbicaval xshort axis (formula 1) and 1.22 x larger diameter (formula 2), exhibited good agreement with the standard stretched size with Kappa values of 0.91 and 0.90, respectively. The accuracy rate of predicted stretched sizes within 2 mm, 3 mm, and 4 mm range of the standard size were 32.8%, 45.4%, and 57.7% (formula 1) and 33.1%, 50%, and 63.2% (formula 2). The stretched size of ASD predicted by ICE exhibited good agreement with the standard stretched size. This prediction provides helpful information, especially if balloon sizing cannot be adequately performed.

Effects of a 12 week self-managed stretching program among Korean-Chinese female migrant workers in Korea: a randomized trial.

PubMed