Muscle Force and Myoelectric Manifestations of Muscle Fatigue in Voluntary and Electrically Elicited Contractions

This chapter deals with the association between surface electromyography (sEMG) and force/fatigue and outlines this association, and the tools to study it. It considers myoelectric manifestations of muscle fatigue as investigation tools. The association between relative decrease of conduction velocity and relative decrease of spectral variables is based on the relations between conduction velocity and power spectrum and between fiber type and fiber size. Muscles are made of fibers which classified into three main types: slow oxidative fibers, fast oxidative glycolitic fibers, and fast glycolitic fibers. Analysis of variance (ANOVA), coefficient of variation (CoV), standard error of the mean (SEM), and intraclass correlation coefficient (ICC) are repeatability of sEMG measurements and fatigue indicators tools. The agreement between sEMG-based estimation of fatigue and perceived exertion, at least in isometric fatiguing contractions, is of considerable interest in occupational medicine.