Analysis of Heel Raise Exercise with Three Foot Positions

Prior research revealed activation differences between the medial (MG) and lateral (LG) gastrocnemius when performing heel raise exercise with neutral (N), internally-rotated (IR) and externally-rotated (ER) foot positions. Studying underlying biomechanics may help explain activation differences. The purpose was to compare ankle (AN), knee (KN), and hip (HI) contributions (initial joint angles) to attaining each initial foot position, ankle flexion-extension range of motion, ankle mechanical energy expenditure, repetition time, and percent cycle concentric-eccentric transition between N, IR, and ER foot positions. Twenty healthy subjects (11 male, 9 female) with resistance training experience performed twelve repetitions of free-weight (135% body mass) heel raise exercise using N, IR and ER foot positions in a counterbalanced order. Forefeet were elevated .05m onto separate forceplates. Electromagnetic sensors secured along dominant lower limb recorded kinematic data. Dependent variables were averaged across five selected repetitions. No significant differences existed for repetition time (P=.209), percent cycle concentric-eccentric transition (P=.668), ankle mechanical energy expenditure (P=.590), and ankle flexion-extension range of motion (P=.129) between foot positions. Post hoc comparison of a significant joint by foot position interaction (P<.001) demonstrated IR>N>ER for the initial HI and KN angles, whereas for AN, ER>IR and N. Between joints: AN<KN and HI for N and AN<KN<HI for IR. Although it was expected the IR/ER/N positions would induce large start AN angle changes, our results reveal the greatest changes at the HI followed by the KN. Small AN differences may be explained by beginning dorsiflexed (close-packed position). Further research is needed to explain the MG and LG activation differences previously reported.