Peripheral And Central Fatigue Development And Short-term Recovery During All-out Repeated Sprints

Abstract

Recent evidence suggests that power output during repeated sprints of short duration is adjusted by the central nervous system to restrain the development of locomotor muscle fatigue to a critical threshold. This adjustment of power output might involve a complex interplay between peripheral and central determinants of muscle fatigue. The rate of peripheral and/or central fatigue development and its influence on the pattern of power output during repeated sprints remain however largely unknown. PURPOSE:We aimed to determine the contribution of peripheral and central fatigue to power output reduction during repeated sprints and whether power output levels off when a critical threshold of peripheral fatigue is reached. METHODS: On separate days, twelve healthy subjects performed the following tests: 1, 4, 6, 8 and 10, 10 s all-out sprints, each with 30 s of passive recovery between sprints, as well as 8, 10 s sprints, each with 10 s of passive recovery to test the influence of varying the work / recovery ratio on our hypotheses. Peripheral fatigue was quantified via changes in pre- to post-exercise potentiated quadriceps twitch force evoked by supramaximal electrical stimulation of the femoral nerve (ΔQtw, 0.5 through 6 min recovery). Central fatigue was estimated via changes in pre- to post-exercise voluntary quadriceps activation (ΔVA). EMG during sprints was normalized by maximal M-wave amplitude (ΔRMS.Mmax-1). RESULTS: From the 1st to the 6th sprint, we found a significant and gradual reduction in ΔQtw (- 47 ± 3 %), ΔRMS.Mmax-1 (- 7 ± 1 %) and power output (- 25 ± 2 %). During the 4 subsequent sprints, no additional reduction of quadriceps fatigue, RMS.Mmax-1 or power output was found but VA was significantly reduced compared to baseline (- 11 ± 2 %). Recovery of Qtw, post-sprints (0.5 through 6 min), was reduced progressively following sprint #1 through #6, with no further reduction thereafter (through sprint #10). CONCLUSIONS: Both peripheral and central fatigue contribute to the reduction of power output during repeated sprints. The leveling off of power output and RMS.Max-1 when the same degree of peripheral fatigue was reached, independently of the work / recovery duration ratio, suggest that central motor drive was restricted to limit excessive development of peripheral muscle fatigue.