Electric discharge patterns of ankle muscles during the normal gait cycle.

EMG patterns in ankle muscles were examined during normal gait cycles in 147 healthy asymptomatic adults. In all subjects, the tibialis anterior (Ta) showed marked activities around the toe-off and before the heel-strike, and the gastrocnemius lateral head (Gl) showed marked activity during the midstance phase but no activity in the early part of the swing phase. The Ta activity contributed to ground clearance, prevention of foot-drop, and shock absorption at the heel-strike. The Gl activity contributed to push-off from the ground and prevention of foot-drop. The Ta activity consisted of double bursts with (15% of subjects) or without (44%) electric silence in the midswing phase, continuous discharge (33%), and triple discharge patterns (8%). The Gl activity consisted of a single-peak (95%) pattern or double-peak (5%) patterns.