Ankle muscle activation during functional reach in hemiparetic and healthy subjects

To compare the differences of reaching ability and electromyography of ankle muscles between healthy and hemiparetic subjects.

This is a cross-sectional control trial. A total of 31 subjects with hemiparesis and 31 age-matched healthy adults meeting our selection criteria participated in this study. Subjects performed forward reach and lateral reach, in random sequence, in a sitting position. The average reaching velocity, reaching distance, and onset time and mean muscle activity of bilateral tibialis anterior and soleus were recorded.

Subjects with hemiparesis had slower movement velocity and less reaching distance than that of healthy subjects (P < 0.05). The distance for the lateral reach was shorter than that of the forward reach (P < 0.05). The high correlations between contralateral tibialis anterior and soleus were noted in forward (r = 0.66, P < 0.01) and lateral (r = 0.68, P < 0.01) reaching in healthy subjects, but such correlations were not established in subjects with hemiparesis. Except for the ipsilateral soleus, normalized electromyographic activities (percentage of maximal voluntary isometric contraction) during forward and lateral reach were higher for the hemiparetic subjects than that for the healthy subjects (P < 0.05).

The functional reach abilities and the ankle electromyographic activity patterns in hemiparetic subjects were significantly different from those of healthy subjects. The muscles in the affected ankle cannot be recruited timely and efficiently for the reaching task, even with relative recovery.