Effects of temperature and fatigue on the electromechanical delay components

Introduction: Neuromuscular activation can be influenced by both muscle temperature (Tm) and fatigue. Methods: To assess the effects of Tm and fatigue on the electromechanical delay (EMD), 15 participants performed voluntary isometric contractions of different intensities under neutral (TmN ), low (TmL ), and high (TmH ) Tm, before and after a fatiguing exercise. During contraction, electromyogram (EMG), mechanomyogram (MMG), and force (F) were recorded from the biceps brachii muscle. The EMD and the latencies between EMG and MMG (\u394t EMG-MMG, which includes the electrochemical processes of EMD) and between MMG and F (\u394t MMG-F, which includes the mechanical processes of EMD) were calculated. Results: TmL increased only \u394t EMG-MMG, both before and after fatigue. Fatigue lengthened EMD, \u394t EMG-MMG, and \u394t MMG-F under all Tm to a similar extent. Conclusions: While fatigue increased all EMD components, muscle cooling affected only the electrochemical but not the mechanical processes of EMD. Muscle Nerve, 2013