Search results for "Skeletal"
showing 10 items of 3025 documents
Mechanical behavior of the quadriceps femoris muscle tendon unit during low-load contractions
2008
We examined the relationships between morphology and muscle-tendon dynamics of the quadriceps femoris muscle of 11 men using velocity-encoded phase-contrast magnetic resonance imaging (MRI). Thigh muscle electromyography and joint range of motion were first measured outside the MRI scanner during knee extension-flexion tasks that were performed at a rate of 40 times/min with elastic bands providing peak resistance of 5.2 kp (SD 0.4) to the extension. The same movement was repeated inside the MRI scanner bore where tissue velocities and muscle morphology were recorded. The average displacement in the proximal and distal halves of the rectus femoris and vastus intermedius aponeuroses was dif…
Is Activation of the Back Muscles Impaired by Creep or Muscle Fatigue?
2010
STUDY DESIGN: Intervention study on healthy human subjects. OBJECTIVE: To determine whether reflex activation of the back muscles is influenced by muscle fatigue or soft tissue creep in the spine. SUMMARY OF BACKGROUND DATA: Reflex contraction of the back muscles normally acts to limit spinal flexion, and hence protect the underlying spine from injury. However, repeated flexion allows bending moments on the spine to increase. Impaired reflexes as a result of fatigue or soft tissue creep may be contributing factors. METHODS: A total of 15 healthy volunteers (8 females/7 males aged 23-55 years) underwent 2 interventions, on separate days: (a) sitting flexed for 1 hour to induce creep and (b) …
Muscular synergies during motor corrections: investigation of the latencies of muscle activities.
2010
To reduce the complexity of muscular control, a small number of muscular activations are combined to produce an infinity of movements. This concept of muscle synergies has been widely investigated, mainly by means of principal component analyses (PCA) in the case of unperturbed movements. However, reaching movements can be altered at any time if the target location is changed during their execution. In this case, PCA does not precisely measure the latencies of muscles activities. We develop here a simple method to investigate how a random target jump toward a single location induced motor corrections in the whole musculature by precisely determining the latencies of muscle activities during…
Apoptosis-related Proteins in Skeletal Muscle Fibers of Spinal Muscular Atrophy
1997
There is evidence that apoptosis in spinal muscular atrophies (SMA) is not restricted to motor neurons but also affects muscle fibers. Studying the expression of several apoptosis-associated proteins we found constant expression of bax in muscle fibers, which promoted cell death. The expression of bax correlated with defective innervation of muscle fibers was also indicated by upregulation of N-CAM. While in early-onset SMA atrophic as well as normo- and hypertrophic muscle fibers displayed expression of bax, muscle fibers in late-onset SMA and peripheral neuropathies showed bax-expression only in atrophic fibers. Other investigated apoptosis-associated factors comprised interleukin-1 beta …
Hip Muscle Strength Recovery after Hip Arthroscopy in a Series of Patients with Symptomatic Femoroacetabular Impingement
2014
International audience; Purpose: The aim of the study was to prospectively evaluate hip muscle strength in a series of patients with symptomatic FAI after hip arthroscopy. Methods: Hip muscle strength of eight patients (age: 29 +/- 10 years) was evaluated preoperatively and 2.5 years after hip arthroscopy, and was compared to eight matched controls. Maximal voluntary contraction (MVC) strength was measured for all hip muscle groups. At follow-up, we used the symptom-specific well-being outcome to assess the acceptability of the health state related to the hip. Results: Patients showed MVC strength increases for all hip muscles (9-59%, P<.05). At follow-up, only hip flexor MVC strength was l…
Concurrent Criterion-related Validity, Reliability, and Responsiveness to Treatment of the Figure-of-Four Position for Measurement of Anterior Hip Jo…
2018
Abstract Objective The objective of this study was to examine the intra- and intertester reliability, concurrent criterion-related validity, and responsiveness to treatment of the “figure-of-four” position. Methods A total of 52 asymptomatic male soccer players participated in this study. The intraclass correlation coefficient (2, 1) was used to determine intra- and intertester reliability of the figure-of-four position. Pearson product moment correlation coefficients examining the association between the figure-of-four position and goniometric measurements of hip extension and external rotation were used to establish concurrent validity. To evaluate responsiveness to treatment, the figure-…
Efficacy and safety of rituximab treatment in early primary Sjögren's syndrome: a prospective, multi-center, follow-up study.
2013
Introduction Primary Sjögren’s syndrome (pSS) is an autoimmune disorder affecting exocrine glands; however, a subgroup of pSS patients experience systemic extra-glandular involvement leading to a worsening of disease prognosis. Current therapeutic options are mainly empiric and often translated by other autoimmune diseases. In the last few years growing evidence suggests that B-cell depletion by rituximab (RTX) is effective also in pSS. Patients with early active disease appear to be those who could benefit the most from RTX. The aim of this study was to investigate the efficacy and safety of RTX in comparison to disease modifying anti-rheumatic drugs (DMARDs) in early active pSS patients. …
Motor recruitment during action observation: Effect of interindividual differences in action strategy
2020
Abstract Visual processing of other’s actions is supported by sensorimotor brain activations. Access to sensorimotor representations may, in principle, provide the top-down signal required to bias search and selection of critical visual features. For this to happen, it is necessary that a stable one-to-one mapping exists between observed kinematics and underlying motor commands. However, due to the inherent redundancy of the human musculoskeletal system, this is hardly the case for multijoint actions where everyone has his own moving style (individual motor signature—IMS). Here, we investigated the influence of subject’s IMS on subjects’ motor excitability during the observation of an actor…
Reduced reflex sensitivity persists several days after long-lasting stretch-shortening cycle exercise
1999
The mechanisms related to the acute and delayed secondary impairment of the stretch reflex function were investigated after long-lasting stretch-shortening cycle exercise. The results demonstrated a clear deterioration in muscle function immediately after fatigue, which was accompanied by a clear reduction in active and passive reflex sensitivity. For active and passive stretch reflexes, this reduction was biphasic ( P < 0.05 to P < 0.001). However, for the ratio of the electrically induced maximal Hoffmann reflex to the maximal mass compound action potential, only one significant reduction was seen immediately after fatigue (71.2%, P < 0.01). A similar significant ( P < 0.01) d…
Neural and mechanical responses of the triceps surae muscle group after 1 h of repeated fast passive stretches
2004
Experiments were carried out to examine interaction between mechanical changes of the muscletendon unit and reduced reflex sensitivity after repeated and prolonged passive muscle stretching (RPS). There is some evidence that this interaction might be relevant also during active stretch-shortening cycle type of fatigue tasks. The results demonstrated a clear deterioration of voluntarily and electrically induced muscle contractions after RPS. Maximal voluntary contraction (MVC), average electromyographic activities of the gastrocnemius and soleus muscles, and maximal twitch contraction decreased on average by 13.8, 10.4, 7.6, and 16.8%, respectively. In addition, there was a 14% lengthening …