Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P50502 (Hip)
 7,003 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Myotatic reflexes can be enhanced following brief static contractions. Since static contractions are often used as precursors to muscle stretch, rationale underlying these techniques were questioned and re-examined through electromyography (EMG). Twenty-one female gymnasts performed three methods to produce hamstring stretch: static (S), contract-relax (CR), and contract-relax with agonist (hip flexors) contraction (CRAC). Hip joint angles and intra-individual electromyograms were statistically compared across stretch conditions. In 12 subjects, the CRAC method elicited significantly greater hamstring EMG activity (P < 0.05) than the other techniques. A higher level of muscle activation was associated with the S method in only one subject. No significant differences in EMG activity across stretch conditions were found in eight subjects suggesting that the relative effectiveness of the stretch techniques varied across individuals. Involuntary paroxysmal tremor activity was occasionally visible in EMG records of most subjects at the low levels of muscle activation. While apparently contributing to increased muscle stiffness, the CRAC technique produced the largest gains in hip flextion. Rank orderings of minimum pain and maximum perceived stretch effectiveness were significantly related with one another, and with decreasing EMG activity, but not with range of motion.
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PMID:Electromyographic investigation of muscle stretching techniques. 745 8

Stiff-knee gait is a common walking problem in cerebral palsy characterized by insufficient knee flexion during swing. To identify factors that may limit knee flexion in swing, it is necessary to understand how unimpaired subjects successfully coordinate muscles and passive dynamics (gravity and velocity-related forces) to accelerate the knee into flexion during double support, a critical phase just prior to swing that establishes the conditions for achieving sufficient knee flexion during swing. It is also necessary to understand how contributions to swing initiation change with walking speed, since patients with stiff-knee gait often walk slowly. We analyzed muscle-driven dynamic simulations of eight unimpaired subjects walking at four speeds to quantify the contributions of muscles, gravity, and velocity-related forces (i.e. Coriolis and centrifugal forces) to preswing knee flexion acceleration during double support at each speed. Analysis of the simulations revealed contributions from muscles and passive dynamics varied systematically with walking speed. Preswing knee flexion acceleration was achieved primarily by hip flexor muscles on the preswing leg with assistance from biceps femoris short head. Hip flexors on the preswing leg were primarily responsible for the increase in preswing knee flexion acceleration during double support with faster walking speed. The hip extensors and abductors on the contralateral leg and velocity-related forces opposed preswing knee flexion acceleration during double support.
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PMID:Contributions of muscles and passive dynamics to swing initiation over a range of walking speeds. 2023 44