A mechanomyographic fatigue threshold test for cycling

The purposes of this study were twofold: 1) to derive the mechanomyographic mean power frequency fatigue threshold (MMG MPF_FT) for submaximal cycle ergometry; and 2) to compare the power outputs associated to the MMG MPF_FT to other neuromuscular and gas exchange fatigue thresholds. 9 adults (5 men and 4 women; mean±SD age=23.7±3.7 years; body weight=66.3±8.2kg) performed an incremental cycle ergometry test to exhaustion while expired gas samples, electromyographic (EMG), and MMG signals were measured from the vastus lateralis muscle. The non-significant correlations (r=0.17 to 0.66; p>0.05) among the physical working capacity at the fatigue threshold (PWC_FT), MMG MPF_FT, and gas exchange threshold (GET) suggested that different physiological mechanisms may underlie these 3 fatigue thresholds. A significant correlation (r=0.83) for the MPF_FT vs. respiratory compensation point (RCP) suggested that these fatigue thresholds may be mediated by a common physiological mechanism. In addition, the significantly lower mean values found for the PWC_FT (mean±SD=163±43 W), MMG MPF_FT (132±33 W), and GET (144±28 W) than MPF_FT (196±53 W) and RCP (202±41 W) suggested that these gas exchange and neuromuscular fatigue thresholds may demarcate different exercise intensity domains.