Stretch reflex dynamics in spastic elbow flexor muscles

R. K. Powers*, D. L. Campbell, W. Z. Rymer

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

122 Scopus citations

Abstract

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.

Original languageEnglish (US)
Pages (from-to)32-42
Number of pages11
JournalAnnals of neurology
Volume25
Issue number1
DOIs
StatePublished - Jan 1989

ASJC Scopus subject areas

  • Neurology
  • Clinical Neurology

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