Flexor reflexes in chronic spinal cord injury triggered by imposed ankle rotation

Brian D. Schmit*, Alicia Mckenna-Cole, W. Zev Rymer

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

50 Scopus citations


Hypersensitivity of the flexor reflexes to input from force-sensitive muscle afferents may contribute to the prevalence and severity of muscle spasms in patients with spinal cord injuries. In the present study, we triggered flexor reflexes with constant-velocity ankle movements into end- range dorsiflexion and plantarflexion positions in 8 individuals with spinal cord injuries. We found that all 8 subjects had coordinated increases in flexion torque at the hip and ankle following externally imposed plantarflexion movements at the ankle. In addition, end-range dorsiflexion movements also triggered flexor reflexes in 3 subjects, although greater loads were required to trigger such reflexes using dorsiflexion movements (compared to plantarflexion movements). These three-joint reflex torque patterns triggered by ankle movement were broadly comparable to flexion withdrawal responses elicited by electrocutaneous stimuli applied to a toe, although the amplitude of the torque response was generally lower. We conclude that excitation of muscle and joint-related afferents induced by end-range movements may be responsible for exaggerated flexion reflex responses in spinal cord injury. (C) 2000 John Wiley and Sons, Inc.

Original languageEnglish (US)
Pages (from-to)793-803
Number of pages11
JournalMuscle and Nerve
Issue number5
StatePublished - May 2000


  • Flexor reflex
  • Group III muscle afferents
  • Spasms
  • Spasticity
  • Spinal cord injury

ASJC Scopus subject areas

  • Physiology
  • Clinical Neurology
  • Cellular and Molecular Neuroscience
  • Physiology (medical)


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