Abstract
Foot function deteriorates after varus sprain of the ankle joint, and impairs smooth body movement in some cases. Dysfunction of the peroneal muscles, such as muscle weakness and delayed reaction time, occurs after varus sprain, and great importance has been attached to strengthening of the peroneal muscles in exercise therapy. Our exercise therapy targets stable posture control in weight-bearing on the little toe side, and we consider that not only the peroneal muscles but also varus muscles of the foot are important with regard to muscle activity in this position. In this study, we investigated muscle activity of the varus muscles of the foot and plantar pressure distribution on the supporting side in inward step positions as an exercise menu. Compared to the baseline position regarded as 0 cm, muscle activity increased at an inward step distance of 10 and 20 cm, and significantly increased at 30 and 40 cm (p<0.01). It is suggested that the inward steps induced weight-bearing on the little toe side, and forced tilting of the lower leg outward, during which the varus muscles may have acted to brake the outward tilting of the lower leg. This suggests that the varus muscles of the foot are important for posture control in weight-bearing on the little toe side.
