Gastrocnemius Muscle Activity in Human Locomotion

Abstract

Simultaneous and synchronized EMG and cinematographic recordings of four male subjects were used to correlate the intensity of medial gastrocnemius muscle activity with the motion of lower limb segments, as they walked on a treadmill and on the floor. For both walking media the invariable retardation of forward shank motion, which is requisite for mid-stance knee extension, was often associated with an early smaller concentration of EMG, and a later more major envelope of muscle activity was constantly synchronous with the retardation of forward thigh motion, which necessarily occurs at the transition from knee extension to knee flexion. A mechanical linkage is suggested between restraint of forward thigh motion and the initial elevation of the heel from the ground. Plantar flexion of the ankle and upward thrust of the shank appear to be related to residual post-activity tension of the gastrocnemius muscle.