Sensitivity and Reproducibility of a Fatigue Response in Elite Youth Football Players

Fitzpatrick, J.F., Akenhead, R., Russell, M., Hicks, K.

This study aimed to establish firstly, the sensitivity of subjective wellness, jump performance, and tri-axial accelerometer measures to training-induced fatigue and secondly, the reproducibility of this training-induced fatigue response. In 14 elite youth football players, morning assessments of subjective wellness (fatigue, sleep quality, muscle soreness, stress, and mood), jump performance (countermovement jump height [CMJ], squat jump height [SJ], and drop jump contact time [DJ-CT], height [DJ-JH], and reactive strength index [DJ-RSI]) and tri-axial accelerometer data (PlayerLoadTM [PL], the individual movement planes of PL [anterior–posterior [PLAP], mediolateral [PLML], and vertical [PLV]) and the percentage contribution of each component plane) were collected before (-24 h and immediately prior) and after (+24 h, +48 h) a standardized strenuous training session on two occasions to assess the reproducibility of a training-induced fatigue response. Sensitivity was assessed via the signal-to-noise (S:N) ratio of the changes in fatigue measures +24 h post-training and the minimum detectable change for each measure. DJ-RSI, PLML, and %PLV were found to be sensitive measures of training-induced fatigue, which displayed a reproducible response (S:N >1 on both occasions). CMJ, SJ, and all subjective wellness measures were not able to detect a reproducible fatigue response.

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