Surface Electromyographic Study of Peroneus Longus Activation during Ankle Eversion and Heel Lift

Prophylactic and rehabilitative ankle training programs rarely incorporate ankle eversion exercises of the weight bearing leg during one-legged stand. Such training may be necessary for the optimal PL function and dynamic ankle control. In this study, we compared a PL exercise that involved eversion of the inverted ankle of a weight bearing leg against the heel lift (HL), a popular PL strengthening exercise. The PL activation patterns were studied in 20 university students (7 male and 13 female). The self-reported dominant legs of the subjects were tested in this study. After recording the surface electromyographic (EMG) activity level of their PL maximal voluntary isometric contractions (MVIC), the subjects performed HL, and ankle eversions of the weight bearing ankle during one-legged stand. Ankle eversions were initiated from two inverted ankle positions, 20 degree inversion (EV1) and 25 degree inversion (EV2). The ankle position and the PL muscle activity were recorded with an accelerometer affixed to the dorsum of the foot and a surface EMG electrode over PL respectively. The ranges of motion for HL, EV1, and EV2 were 25, 29, and 31 degrees respectively. Expressed as percentage of MVIC, the average normalized EMG linear envelopes for EV1 (73%) and EV2 (74%) were significantly greater than HL (64%). These results demonstrated that eversions of the inverted ankle of the weight bearing leg elicited stronger PL activation that may result in better lateral ankle strength and dynamic control. Incorporation of weight bearing ankle eversions may enhance effectiveness of PL exercise and balance.