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

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. Soccer-specific technical performance was negatively affected by mental fatigue condition only in U18 in the LSPT..