Myoelectric stimulation on peroneal muscles with electrodes of the muscle belly size attached to the upper shank gives the best effect in resisting simulated ankle sprain motion

Ankle sprain is a common sports related injury that may be caused by incorrect positioning of the foot prior to and at initial contact during landing from a jump or gait. Furthermore a delayed reaction of the peroneal muscle may also contribute to the injury mechanism. A recent study demonstrated that myoelectric stimulation of the peroneal muscles within 15. ms of a simulated inversion event would significantly resist an ankle spraining motion. This study further investigated its effect with three different electrode sizes and three different lateral shank attachment positions. Twelve male subjects with healthy ankles performed simulated ankle supination spraining motion on a pair of mechanical sprain simulators. A pair of electrodes of one of the three sizes (large, medium, small) was attached to one of the three positions (upper 1/4, middle, lower 1/4) along the lateral shank to deliver an electrical signal of 130. V for 0.5. s when the sprain simulator started. Ankle kinematics data were collected by a tri-axial gyroscope motion sensor and the peak inward heel tilting velocity was obtained to represent the effect in resisting the simulated ankle spraining motion. Repeated measures one-way analysis of variance was performed and showed a significant drop from 273.3 (control, no stimulation) to 215.8. deg/s (21%) when small electrodes were attached to the upper 1/4 position. Decrease was found in all other conditions but the drops (11-18%) were not statistically significant. The small electrodes used in this study fitted the width of the peroneal muscle belly at the upper 1/4 position, so the electrical current may have well flowed to the motor points of the muscles to initiate quick contraction.