Neuromuscular Fatigue in English Premier League Academy Football Players: Within- and Cross- Season Responses.

Objectives: To examine the within- and cross- season neuromuscular fatigue (NMF) responses in English Premier League (EPL) U-18 academy football players. Design: Twenty-five players from the same team completed weekly countermovement jump (CMJ) and isometric adductor (IADS) and posterior chain (IPCS) strength tests for a full competitive season. Methods: Sports Global positioning system measures of training and match total (TD) high-metabolic load (HML) and sprint (SD) distance were recorded daily and converted into exponentially weighted moving average seven- and twenty-eight- day values. Results TD28 (p<.001), HML28 (p<.001), and SD28 (p=.002) shared negative relationships with CMJ jump height, but there was no main cross-season effect (p=.137). TD28 (p=.016) and HML28 (p=.012) positively related to IPCS but there was no effect of SD28 (p=.653), SD7 (p=.549), TD7 (p=.080) or HML7 (p=.104). Cross season, IPCS followed a curvilinear response whereby performance increased across the beginning of the season and decreased towards the end of the season (p= .003). There was no effect of training load or time on IADS performance (p >.094). Conclusions: Neuromuscular status, signalled by CMJ jump height changes fluctuates across the season in response to sustained changes in training and match load, but there is no evidence of a main cross-season linear effect. Total training and match volume exert moderating effects on the internal training load dose, and in-turn, important moderating effects on NMF, particularly when composed of high volumes of high-intensity and SD workloads. The posterior chain might be particularly susceptible to fatigue towards the end of the season.