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Stretch reflex dynamics in spastic elbow flexor muscles
Author(s) -
Powers R. K.,
Campbell D. L.,
Rymer W. Z.
Publication year - 1989
Publication title -
annals of neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.764
H-Index - 296
eISSN - 1531-8249
pISSN - 0364-5134
DOI - 10.1002/ana.410250106
Subject(s) - hypertonia , stretch reflex , spastic , reflex , elbow , physical medicine and rehabilitation , triceps reflex , electromyography , medicine , h reflex , psychology , anatomy , withdrawal reflex , anesthesia , cerebral palsy
Previous studies of stretch reflexes in patients with spastic hypertonia have emphasized the dynamic character of stretch reflex output. In contrast, our own studies of stretch reflex dynamics in spastic elbow flexor muscles of 14 hemiparetic human subjects have shown that stretch‐evoked torque displays a relatively weak dependence on stretch velocity, and there is generally no preferential enhancement of dynamic as compared with static reflex output. Moreover, stretch reflex dynamics are broadly similar in voluntarily activated spastic and normal elbow flexor muscles. These findings support our hypothesis that spastic hypertonia results primarily from a decrease in stretch reflex threshold. The strong velocity dependence of stretch‐evoked electromyographic activity in initially inactive spastic muscles could be due to a decrease in reflex threshold with increasing stretch velocity, rather than an abnormal velocity‐dependent increase in stretch reflex responsiveness.