Increased H(max):M(max) ratio in community walkers poststroke without increase in ankle plantarflexion during walking.

OBJECTIVE: To investigate whether changes in H-reflex response at midswing and midstance are related to excessive plantarflexion during walking in community walkers poststroke compared with control subjects without stroke.
DESIGN: Survey of functional walking handicap in a random sample of an annual stroke cohort followed by H-reflex and M(max) testing of a smaller sample.
SETTING: Community and laboratory testing. PARTICIPANTS: Forty individuals with stroke (IWS group) completed the functional walking handicap survey, 10 of whom agreed (with 10 age-matched controls) to enroll in a study of of the H(max):M(max) ratio in soleus during walking. INTERVENTION: Electromyography during treadmill walking. MAIN OUTCOME MEASURES: Functional Walking Handicap Scale, soleus H(max):M(max) ratio, and the ankle joint's angle of displacement.
RESULTS: Nine of the 10 stroke patients were community walkers. All had significantly (p <.05) more variable ankle movement during walking than the controls. The H(max):M(max) ratio was significantly (p <.01) increased in the IWS group because of a decrease in M(max) response without significant (p >.05) increase in H(max) response.
CONCLUSIONS: Individuals with community-level walking ability after stroke have significantly (p <.05) less repeatability of ankle joint movement than controls at both midswing and midstance. Simultaneous soleus H(max) and M(max) testing showed a significant (p <.01) reduction in the H(max) and H(max):M(max) ratio at midswing in controls only. This inhibition at midswing was lost by the IWS group without significant increase in H(max), suggesting that central synaptic excitability was within the normal range, and possibly accounting for the absence of excessive ankle plantarflexion during walking in the IWS group with community level walking ability.