Abstract
A difference of alignment of rear foot between lying down and standing in patients who have sports disorders is often observed. The purpose of this study was to clarify the relationship between the alignment of the rear foot and activities of ankle flexor muscles during the calf-raise. We identified an alteration of the alignment of the rear foot between the prone position to standing by measuring leg heel angle under each condition, and classified subjects into three groups (varus, neutral, valgus) according to angle alteration. In addition, we measured activities of the tibialis posterior muscle, soleus muscle, medial head of the gastrocnemius muscle and lateral head of the gastrocnemius muscle during the calf-raise with surface electromyography. The varus group showed significantly greater activation of the tibialis posterior muscle than the valgus group. Activation of the medial head of the gastrocnemius muscle displayed similar findings with an increase from the valgus group to the neutral and varus groups. These results suggest that if alignment of the rear foot in standing is more varus than in lying prone, sports disorders are potentially more likely in therapeutic calf-raise exercises and in running during training.
