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.