The Effect of Foot Orthoses on Lower Limb Muscle Electromyographic Activity During Walking and Running

Abstract

1225 Foot orthoses are commonly used to treat painful conditions involving the lower limb muscles. No known research has determined the effect of foot orthoses on the posterior tibialis muscle activity, and studies on other muscles are limited. PURPOSE: To determine the effect of custom and prefabricated foot orthoses on the electromyographic (EMG) activity of select lower limb muscles. METHODS: Subjects with asymptomatic pes planus were tested with custom molded and prefabricated orthoses, and with no orthoses. EMG activity was measured in the posterior tibialis, tibialis anterior, and peroneus longus muscles during walking and running. Subtalar and sagittal ankle range of motion were simultaneously measured. RESULTS: There was a reduction in peroneus longus EMG activity with custom orthoses during walking (p = 0.0597), and a trend toward similar reduction with prefabricated orthoses. There were no changes in EMG activity in any of the other muscles studied, including the posterior tibialis. Electrogoniometric recordings demonstrated a reduction in frontal plane range of motion during running. Custom-molded orthoses appeared to provide more subtalar control than the prefabricated orthoses but changes did not meet statistical significance. CONCLUSIONS: This study suggests that the clinical benefits of orthoses in conditions affecting the tibialis posterior are more likely due to alterations in kinematics than changes in muscular activity. More supportive and/or restrictive orthotic devices may be required to reduce muscular activity.