Effects of mental fatigue on soccer-specific performance in young players

The aim of this study was to investigate the effects of mental fatigue on soccer-specific physical and technical performance in young players. Twelve under-14 (U14), twelve under-16 (U16) and twelve under-18 (U18) soccer players completed the two parts of the investigation. Part one assessed the soccer-specific physical performance using the Yo-Yo Intermittent Recovery Test, Level 1 (Yo-Yo IR1). Part two assessed the soccer-specific technical performance using the Loughborough Soccer Passing and Shooting Tests (LSPT, LSST). Each part was preceded by 30 min of Stroop task or 15 min of control task performed in a randomised and counterbalanced order. Subjective ratings of mental fatigue were higher after the Stroop task compared to the control in U14, U16 and U18 in both parts. Mental fatigue significantly reduced Yo-Yo IR1 distance, alongside an increase in heart rate and ratings of perceived exertion, and this effect was moderated by age as older players showed greater declines in performance. For LSPT, original time, penalty time and performance time were significantly higher in the mental fatigue condition than in the control condition in U18. For LSST, points per shot, shot speed and shot sequence time were not significantly different between conditions in U14, U16 or U18.