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Two physiological factors are assumed in this paper to mainly determine the myoelectric manifestations of fatigue: (1) the decrease of the conduction velocity (CV) of motor unit action potentials (MUAP) (peripheral fatigue), and (2) the increase of MU synchronization by the central nervous system (central fatigue). To describe separately the peripheral and central components of the myoelectric manifestations of fatigue, we investigated the following indexes: (1) mean spectral frequency – MNF, (2) median spectral frequency – MDF, (3) root mean square – RMS, (4) average rectified value – ARV, (5) estimation of muscle fiber conduction velocity – ECV, (6) percentage of determinism – %DET, (7) spectral indexes defined as the ratio between signal spectral moments – FI_k, (8) MNF estimated by autoregressive analysis – MNF_AR, (9) MNF estimated by Choi–Williams time-frequency representation – MNF_CWD, (10) MNF …