Individual differences in knee extensor fatigue induced by sustained middle-level contraction

This study investigated whether the individual differences in knee extensor fatigue induced by sustained middle-level contraction are explained by one or more indices of muscle fatigue. Twenty-four healthy young men performed a sustained fatiguing contraction to task failure at 40% of maximal voluntary contraction (MVC) torque of the knee extensors. The evoked triplet torque (TQtri) and MVC torque (TQMVC) of the knee extensors were measured before and after the fatiguing task. Voluntary activation was also determined before and after the fatiguing task. These values after the fatiguing task were normalized to those before. The normalized TQMVC was significantly correlated with the normalized TQtri, but not with the normalized voluntary activation. The current results suggest that the individual differences in knee extensor fatigue induced by sustained middle-level contraction is more affected by the peripheral fatigue than the central fatigue.