Seasonal variation of physical, perceptual, and cognitive function measures in professional academy soccer players

Soccer match play and training have been documented to significantly impair players' physical function and affect their perceptual wellness, indicating the necessity of evaluating the response to mixed-content training across a soccer season (Deely et al., 2022, Front Physiol, 13, 911009; Brownstein et al., 2017, Front Physiol, 8, 831; Thomas et al., 2017, Med Sci Sports Exer, 49, 955-964). This study aimed to assess seasonal variation in physical, perceptual, and cognitive functions in response to training among professional academy soccer players, to identify whether players develop increased physical robustness or encounter greater physiological and psychological impairments due to the demanding training and match schedule. Ethical approval was granted for sixteen academy players (age: 18 ± 1 years) to undergo a range of tests at three seasonal points - early, mid, and late - at baseline, immediately post-strenuous training, and at 24, 48, and 72 h. The testing regime encompassed physical performance (countermovement jump CMJ, ten-to-five repeated jump test 10/5 RJT), cognitive function (Stroop task, Four-Choice Reaction Time FCRT test, Corsi Block Test), and perceptual responses via an adapted Short Questionnaire of Fatigue (SQF). Linear mixed modelling (LMM) was employed to analyse the impact of season phase and testing time-points on training response, incorporating testing measures as dependent variables. Jump performance varied across time-points, with performance maintained immediately post-training, although displaying decrements at 24 h (P < 0.001), 48 h (P < 0.01), and remained unresolved at 72 h (P < 0.05). Season phase exerted a fixed effect on physical function, with vertical jumps decreasing from both early- (P = 0.033, CMJ; P < 0.001, 10/5 RJT) and mid-season (P < 0.001, CMJ; P < 0.001, 10/5 RJT) to late-season. Perceptual measures—soreness, fatigue, and readiness to train—varied across the week, with immediate post-session impairments recovering by 48 and 72 hours. Cognitive function remained relatively stable across the training week, with only a decline in Corsi Block performance noted immediately post-session. An improvement in FCRT from early to mid-season was observed, though accuracy decreased from early to late-season. No interaction between season phase and training week time-points was found across any variable, indicating a consistent training response throughout the season, despite substantial impairments in physical function and declines in perceptual wellness observed post-training. The decrease in physical function during the late-season phase underscores the need for enhanced recovery focus and training load monitoring as the season progresses.