Detection of Muscle Fatigue during Low-Level Isometric Contraction using Recurrence Quantification Analysis

Abstract

This study aimed to detect muscle fatigue during low-level isometric contraction using recurrence quantification analysis (RQA). It also examined whether the electrode configuration affects the sensitivity of detection of muscle fatigue. Five healthy subjects in their 20s participated in the experiment. They kept their dominant arm fixed parallel to the floor for 10 minutes. The surface EMG signal from the biceps bra- chii was recorded using unipolar and bipolar configurations. The RQA-based fatigue index was calculated as the percentage of determinism (%DET). The results can be summarized as follows. 1) %DET significantly increased with progression of fatigue. RQA is therefore capable of detecting muscle fatigue during low-level isometric contraction. 2) The %DET recorded by the unipolar configuration exhibited somewhat larger variation than that recorded by the bipolar configuration. The unipolar configuration appears to be more effective in detecting muscle fatigue by RQA. 3) %DET is more sensitive than a traditional index, median frequency (MDF), to fatigue-induced changes.Keywordsmuscle fatiguesurface EMGrecurrence quantification analysisisometric contraction