Effects of lower extremity rotation on muscle activity during heel-raise exercise

BACKGROUND: The heel raise exercise is important during the rehabilitation of a lower extremity injury. This exercise can be performed with varying foot positions, yet little is known about the effects of lower extremity position on muscle activation of the calf muscles when performing the heel raise exercise, specifically in the sitting position. The objective was to analyze the effect of lower extremity rotation on muscle activation of the triceps surae when performing the heel raise exercise in sitting and standing positions. METHODS: Twelve healthy college students volunteered for the study. Surface electrodes were placed on the right lateral and medial gastrocnemius and soleus muscles and maximum voluntary isometric contraction was used to normalize the measurements. Each participant performed 10 repetitions of the heel raise exercise with their lower extremities positioned in neutral, maximal internal rotation and external rotation in both sitting and standing. Multiple 2 x 2 ANOVAs with P≤ .05 were used to examine differences between and within muscles for each phase and position. RESULTS: A significant muscle main effect was identified, P=0.005, during the concentric phase in the sitting position. Post hoc tests did not show significant differences within each of the three muscles. Similarly, during the eccentric phase in sitting a significant main effect for muscle, P=0.037, was found, but post hoc tests did not reveal significant within muscle differences in muscle activation. CONCLUSIONS: The results indicate that lower extremity rotation does not significantly affect muscle activation of the triceps surae when performing the heel raise exercise.