Effect of toe extension on EMG of triceps surae muscles during isometric dorsiflexion.

Abstract

The protocol for estimating force of contraction by triceps surae (TS) muscles requires the immobilization of the ankle during dorsiflexion and plantar flexion. However, large variability in the results has been observed. To identify the cause of this variability, experiments were conducted where ankle dorsiflexion force and electromyogram (EMG) of the TS were recorded under two conditions: (i) toes were strapped and (ii) toes were unstrapped, with all other conditions such as immobilization of the ankle remaining unchanged. The root mean square (RMS) of the EMG and the force were analyzed and one-tail Student's t-test was performed for significance between the two conditions. The RMS of the EMG from TS muscles was found to be significantly higher (~55%) during dorsiflexion with toes unstrapped compared with when the toes were strapped. The torque corresponding to dorsiflexion was also higher with toes unstrapped. Our study has shown that it is important to strap the toes when measuring the torque at the ankle and EMG of the TS muscles.