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

✍ Scribed by Brian D. Schmit; Alicia McKenna-Cole; W. Zev Rymer

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 668 KB
• Volume: 23
• Category: Article
• ISSN: 0148-639X
• DOI: 10.1002/(sici)1097-4598(200005)23:5<793::aid-mus18>3.0.co;2-t

✦ Synopsis

Hypersensitivity of the flexor reflexes to input from forcesensitive 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 endrange 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.