Analysis of Muscle Fatigue Using Electromyography Signals in Gastrocnemius Muscle during Isometric Plantar Flexion

Abstract

Fatigue during plantar flexion and the gastrocnemius muscles causes an increase in mediolateral sway and postural control impairment. The purpose of this study is to analyze the variation in the surface electromyography (sEMG) characteristics during isometric plantar flexion. For this, sEMG signals are recorded from the medial and lateral gastrocnemius muscle from 8 subjects and a minimum of 3 trials each, leading to a total of 25 trials per leg. The subjects performed isometric plantar flexion and are asked to hold the position until fatigue. The result shows that the endurance time of each subject vary. On comparing the endurance between legs, a marginal difference is observed. The recorded signal is nonstationary in nature. On visual inspection, the signals show an increase in amplitude with fatigue. The features such as RMS show an increase in value with 20.31% in right leg and 13.93% in the left leg for the signals from medial and lateral gastrocnemius. The proposed muscle fatigue index is a co-contraction based feature and provides better separation between non-fatigue and fatigue. The P-values obtained indicate that the proposed feature performs better than the conventional RMS value with a significance level of P<0.01. This study can be extended to analyze other neuromuscular conditions.