On Repeatability of MU Fatiguing in Low-Level Sustained Isometric Contractions of Tibialis Anterior Muscle

Abstract

The objective of this study was to investigate the repeatability of Motor Units (MUs) fatiguing profiles during repetitive low-level isometric contractions of the Tibialis Anterior muscle. This feature could be used in a wearable robot for lower limb rehabilitation. We focused on the analysis of MU firing rates and the Motor Unit Action Potential (MUAP) shapes. We successfully tracked several MUs across different contraction repetitions to see the changes in their properties. We evaluated the presence of muscle fatigue and found that the mean MU firing rates decrease while the MUAP shapes do not change across the epochs and contractions. Results suggest that the global EMG descriptor (Mean Frequency) changes are mainly caused by changes in MU firing rate and recruitment patterns and not due to the changes in the MUAPs shape.KeywordsMNFFiring rateMUAP shapeFatigueHDsEMG