The effect of varying footwear configurations on the peroneus longus muscle function following inversion.

BACKGROUND The ankle is one of the most commonly injured joints with inversion injury affecting its lateral ligament complex being the commonest of all. Shoes are one of the known risk factors for such an injury. OBJECTIVE This study seeks to examine the impact of varying shoe configurations on the protective function of the peroneus longus muscle during unanticipated foot inversion. METHODS The peak amplitude, latency and post-peak average amplitude of the ipsilateral peroneus longus muscle were recorded by surface electromyography following unanticipated inversion of the feet of 35 subjects in a two-footplate tilting platform from 0° to 20°. The test conditions were barefoot, standard training shoe, shoe with a sole flare, and an above the ankle laced boot. RESULTS Analysis revealed significant differences in peak muscle contraction between shod and unshod conditions. The standard shoe and the flared sole design showed greater statistically significant differences from the unshod condition, than the boot. The muscle was responding earlier in the shod conditions compared to the barefoot. The post-peak average amplitude with the standard shoe and the flared sole shoe were significantly different from the barefoot condition. CONCLUSION Albeit no marked differences could be demonstrated between the tested shoes, the inherent construct of the laced boot probably attempts to protect the ankle-subtalar joint complex evidenced by evoking a less strong peroneus longus muscle's protective response.