Sleep Deprivation and Ultra-endurance Performance: Assessment and Countermeasures

Considered a psychobiological state similar to mental fatigue, sleep deprivation can be defined as a period of extended wakefulness for, at least, 24 hours. Ultra-endurance events are often described as exercise bouts lasting more than six hours, or running distances covered longer than a traditional marathon.

The first aim of this thesis was to explore the sleep and performance of athletes in ultra-marathons longer than 161 km (100 mi). A moderate association between sleep duration and race time was found. Before the first sleep episode, athletes remained awake for more than 24 h. Ratings of perceived exertion (RPE), sleep bouts, sleep time, and sleepiness increased over the course of the race, whereas running speed decreased. As a consequence of the psychophysiological demands of ultra-endurance exercise and the exacerbated sleep loss, it has been suggested that perception of effort plays a key role in pace regulation during ultra-marathon events.

The second aim was to investigate the use of caffeine as a countermeasure for the detrimental effects of sleep deprivation on endurance performance. After one night of sleep deprivation, 6 mg·kg-1 of caffeine improved 30-min running time trial performance by 5.54%. Caffeine reduces perception of effort, allowing participants to sustain a higher running speed at a lower RPE. Therefore, we propose that caffeine can be used to counteract the negative effects associated with sleep deprivation on endurance performance.

The third aim was to study the effects training for a mountain ultra-marathon on sleep deprivation tolerance. Three bouts of exercise after one night of sleep deprivation over a 14-week period did not improve tolerance to the negative effects of sleep deprivation on endurance performance. One night of sleep deprivation reduces time to exhaustion by 28% when running at 75% of peak treadmill speed. Better sleep deprivation tolerance was associated with better chances to finish a ~340-km mountain ultra-marathon race.

The main findings presented in this doctoral research thesis are: 1) a moderate positive association between sleep-related parameters and race time, suggesting that faster runners sleep less and spend less time in activities (i.e., restoring food/drinks at the checkpoints, resting, sleeping) other than moving towards the finish line. 2) The use of caffeine as a measure to counteract the negative effects of sleep deprivation on endurance performance. 3) Three exercise bouts in a sleep deprived state over a 14-week period did not reduce the negative effects of sleep deprivation. These findings might be particularly useful for athletes and/or coaches in the field of ultra-marathon and ultra-endurance performance. Sleep assessment during a mountain-ultra marathon and the countermeasures provided might help to plan their races accordingly.