Changes in motoneuron excitability in hemiplegic subjects after passive exercise when using a robotic arm

Objective: To test the hypothesis that motoneuron excitability in stroke subjects is influenced by peripheral sensory input through passive exercise to the hemiplegic upper extremity. Design: Case-control prospective study. Setting: Physical medicine and rehabilitation inpatient and outpatient clinic at a tertiary Veterans Affairs medical center. Participants: Nineteen hemiplegic adult subjects with a history of a cerebrovascular event. Intervention: A standardized passive exercise program was performed on the right upper extremity by using a robotic arm. Nerve conduction study of the median nerve was obtained before and after the exercise. Maximum onset and peak amplitudes of the Hoffmann reflex (Hmax) and motor response (Mmax) wave were recorded. Main Outcome Measures: Hmax, Mmax, and Hmax/Mmax ratio. Results: Immediately after passive exercise, there was no significant alteration in the Hmax (P=.94), Mmax (P=.60), or Hmax/Mmax ratio (P=.53) as compared with pre-exercise evoked responses. Conclusions: Peripheral proprioceptive input with passive exercise does not cause appreciable change in the Hmax/Mmax ratio, suggesting that motoneuron excitability of the affected upper extremity in stroke subjects is not influenced by passive robotic intervention.