The effects of foot orthotics on the EMG activity of selected leg muscles during gait.

Foot orthotics have been successfully used to treat muscular overuse leg injuries in athletes. The purpose of this study was to examine the effects of foot orthotics on the electromyographic (EMG) activity of the tibialis anterior, peroneus longus, and gastrocnemius muscles during walking. Ten volunteers with leg symptoms resulting from compensatory subtalar joint pronation were fitted with foot orthotics. The duration of tibialis anterior EMG activity following heel strike and the average EMG activity of the tibialis anterior, peroneus longus, and gastrocnemius muscles were collected with surface electrodes. Comparisons were made between the orthotic and nonorthotic conditions. A t-test for nonindependent samples with a significance level of p < 0.05 was used for data analysis. There was a statistically significant increase in the duration of tibialis anterior activity following heel strike in the orthotic condition. There were no significant differences in the average EMG activity for any of the three muscles between the orthotic and the nonorthotic conditions. This study suggests that foot orthotics had minimal effects on the muscles studied and that further research is necessary to determine the effectiveness of orthotics on the EMG activity of other leg muscles.