Electromyography Study of Forward-stepping Motion.

[Purpose] The purpose of this study was to investigate and evaluate the timing and amount of muscle activity during forward-stepping motion. [Subjects and Methods] Seven healthy subjects participated in this study. The task was to step forward from a static standing position. Timing and amount of muscle activity were measured during the task. Muscle activities of the stance leg and the swing leg were measured using surface electromyography (EMG). [Results] A high negative correlation was found between the rate of change in the amount of tibialis anterior muscle activity of the stance leg and the reaction time. High positive correlations were found between the rates of change in the gastrocnemius and soleus muscles and the reaction time of the swing leg. [Discussion] Forward-stepping motion can be accomplished using two strategies. One is to swing the leg out taking a step forward using the gastrocnemius and soleus muscles of the swing leg. The other is to take a step forward using the tibialis anterior muscle of the stance leg. Increasing the activity of the tibialis anterior muscle of the stance leg may lead to taking a step forward rapidly.