Mental Fatigue and Sleep Deprivation: Effects, Mechanisms and Countermeasures in Endurance Exercise Performance

Mental fatigue and sleep deprivation are two common conditions in our modern societies, affecting millions of healthy people. Whereas mental fatigue is considered a psychobiological state caused by prolonged and demanding cognitive activities, sleep deprivation can be defined as a brain state caused by at least 24 hours of wakefulness. The first aim of this thesis was to investigate the acute effects of mental fatigue, sleep deprivation and subsequent recovery sleep on endurance exercise performance. The second aim was to evaluate the effects of two innovative training interventions, Brain Endurance Training (BET) and Sleep Deprivation Training (SDT) on endurance performance. It was hypothesized that: 1) 50-min of mentally-demanding cognitive task and 25-h of sleep deprivation would impair endurance performance and that the following night of recovery sleep would be enough to restore rested endurance performance; 2) six weeks of BET (alone) and six weeks of SDT (combined with physical training) would improve endurance performance. The first and second study do not provide reliable evidence that mental fatigue and sleep deprivation reduce endurance performance during a half-marathon and a 20-min cycling time trial, respectively. However, an alternative statistical analysis used in study one, suggests that the hypothesis that mental fatigue is harmful cannot be rejected. The third study shows that BET is not effective in physically-inactive males. The fourth study reveals that SDT in combination with physical training might be beneficial to counteract the effects of sleep deprivation on endurance performance. In conclusion, the findings do not provide statistical evidence of a negative effect of mental fatigue and sleep deprivation on endurance performance. However, it might be prudent to avoid them prior to races. The use of BET alone does not enhance endurance performance. Nonetheless, the combination of SDT with a physical training program might be beneficial in preparation for an endurance/ultra-endurance event.