Analysis of EMG activity and temporal components of gait during recovery from perturbation.

In ten able-bodied adults, gait was unexpectedly displaced in order to induce rapid dorsiflexion at heelstrike. Electromyographic (EMG) data were collected bilaterally from the tibialis anterior (TA) and gastrocnemius (G) muscles, and electrogoniometric data monitored joint angle changes in the ankle. Analysis of the data indicated initial EMG responses in the G of the perturbed limb and the TA of the contralateral limb at latencies of approximately 100 msec. It appeared that G activity served to decelerate the dorsiflexion of the ankle of the perturbed limb, whereas the TA accelerated dorsiflexion in the swing limb. Analysis of later EMG activity and foot-ground contact indicated that recovery after perturbation was easily completed during stance of the perturbed limb. Because of the comparatively minimal degree and velocity of displacement, further study with similar protocols might be considered appropriate to study balance problems in clinical populations.