THE EFFECT OF MENTAL FATIGUE ON SPORT-SPECIFIC PHYSICAL AND TECHNICAL PERFORMANCE

Introduction: Acute mental fatigue is defined as a psychobiological state that may arise during or after prolonged cognitive activities. Despite several studies showed that mental fatigue appears to impair sport performance, the scientific comprehension of this topic is still limited. Therefore, the aim of this thesis is to broaden the knowledge on the effects of mental fatigue on the sport-related performance. Study 1: This study aimed to investigate the effect of mentally demanding cognitive tasks on rowing performance in prepubertal athletes. Seventeen young rowers completed three separate testing sessions during which they performed three different cognitive tasks before completing a 1500 m time trial on the rowing ergometer. In the two experimental conditions, one hour of a standard cognitive task (Stroop task) and an arithmetic school test were used to elicit mental effort; in the control condition a time-matched, not demanding activity was carried out (painting). The performance of the time trial did not differ between conditions; physiological and perceptual measures recorded during the physical task were not affected by the conditions. Study 2: This study investigated the effect of a mentally demanding response inhibitory task on time trial performance in sub-elite under 23 cyclists. Ten under 23 road cyclists completed two separate testing sessions during which they performed two different cognitive tasks before completing a 30-min time trial on the cycle ergometer. In the experimental condition, 30 min of a standard cognitive task (Stroop task) was used to elicit mental fatigue; in the control condition, a non-demanding activity was carried out. Mean power output and cadence were negatively affected by the Stroop task, while heart rate (HR), rating of perceived exertion (RPE), blood lactate concentration, and heart rate variability (HRV) did not differ between the two conditions. Study 3: This investigation examined 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 (mentally fatiguing task) or 15 min of reading magazines (control task) performed in a randomised and counterbalanced order. Mental fatigue significantly reduced Yo-Yo IR1 distance in the three age groups, alongside an increase in HR and RPE. Mental fatigue reduced soccer-specific physical performance in U14, U16 and U18 players, without alteration of technical performance, except for LSPT in U18. Study 4: This study investigated whether 4 weeks of endurance training could improve tolerance to mental exertion in untrained participants. Twenty participants completed a 4-week training protocol in a randomised and counterbalanced order. Baseline and follow-up assessment were conducted over three sessions in the week preceding and following the training period. During session 1, participants completed an incremental maximal ramp test. During sessions 2 and 3 participants completed a 15 min cycling time trial preceded by either a mental exertion or control task (counterbalanced). Following baseline assessments, participants were randomised into a physical training or placebo group that completed the training intervention thrice weekly over four weeks. The physical training resulted in increases in peak oxygen consumption (VO2peak) relative to the placebo group. Physical training group increased their time trial distance following the mental exertion task to a greater extent than the placebo group. RPE during the time trial and perceptual measures of mental exertion did not significantly change between groups. Conclusions: This thesis provides insight into the effects of mental fatigue on sport-specific physical and technical performance, focusing in broaden the knowledge on different age-groups and evaluating, for the first time, the effect of an endurance training protocol on the ability to tolerate mental fatigue.