Exercise performance is regulated during repeated sprints to limit the development of peripheral fatigue beyond a critical threshold.

: We hypothesized that exercise performance is adjusted during repeated sprints in order to not surpass a critical threshold of peripheral fatigue. Twelve men randomly performed three experimental sessions on different days: one single 10 s all-out sprint and two trials of 10 × 10 s all-out sprint with 30 s of passive recovery in between. One trial was performed in the unfatigued state (CTRL) and one following electrically-induced quadriceps muscle fatigue (FTNMES). Peripheral fatigue was quantified by comparing pre- to post-exercise changes in potentiated quadriceps twitch force (Δ Qtw-pot) evoked by supramaximal magnetic stimulation of the femoral nerve. Central fatigue was estimated by comparing pre- to post-exercise voluntary activation of quadriceps motor units. The RMS of the vastus lateralis and vastus medialis EMG normalized by maximal M-wave amplitude (RMS.Mmax(-1)) was also calculated during sprints. Compared to CTRL, pre-existing quadriceps muscle fatigue in FTNMES (Δ Qtw-pot = - 29 ± 4%) resulted in a significant (P < 0.05) reduction in power output (- 4.0 ± 0.9%) associated with a reduction in RMS.Mmax-1. However, Δ Qtw-pot post-sprints decreased by 51% in both conditions indicating that the level of peripheral fatigue was identical, and independent of the degree of pre-existing fatigue. Our findings showed that power output and cycling EMG are adjusted during exercise for the purpose of limiting the development of peripheral fatigue beyond a constant threshold. We hypothesized that the contribution of peripheral fatigue to exercise limitation involves a reduction in central motor drive in addition to the impairment in muscular function.