The Effects of Heel Elevation on Postural Adjustment and Activity of Lower-Extremity Muscles during Deep Squatting-to-Standing Movement in Normal Subjects

Abstract

The effects of various heel elevations on postural adjustment and lower-extremity muscle activity during the squat-to-stand (SQ-ST) movement were investigated. Eight healthy male subjects participated in the experiment, which involved rising from a deep squat with three different heel elevations: a full squat (FS), in which the plantar aspects of the feet were in full contact with the floor (0 degree), slope squat (SS), in which a 15-degree wedge was applied underneath the foot, and tiptoe squat (TS), in which subjects lifted their heels to their preferred height by extending the metatarsophalangeal joint. Electromyograms were taken of the extensor digitorum brevis (EDB), tibialis anterior (TA), rectus femoris (RF), and gastrocnemius (G) muscles. The results showed that heel elevation significantly affected the postural adjustment: TS caused significantly smaller anterior displacement in the knee and the hip during ankle dorsiflexion and minimized the duration of the forward movement required to stand. On the other hand, EDB activity strongly increased in TS. However, use of foot slope appeared to decrease activities of RF, TA, and EDB. These findings suggest that the use of a foot slope to achieve a squat-to-stand movement may be appropriate to assist patients with weak lower-extremity muscles.