Sleep deprivation and recovery: Endurance racing as a novel model

The aim of this study was to investigate sleep-wake behavior and gain insights into perceived impairment (sleep, fatigue, and cognitive function) of athletes competing in two international multi-day adventure races. Twenty-four athletes took part across two independent adventure races: Queensland, Australia and Alaska, USA. Individual sleep periods were determined via actigraphy, and racers self-reported their perceived sleep disturbances, sleep impairment, fatigue and cognitive function. Each of these indices was calculated for pre-, during- and post-race periods. Sleep was severely restricted during the race period compared to pre-race (Queensland, 7:46 [0:29] vs. 2:50 [1:01]; Alaska, 7:39 [0:58] vs. 2:45 [2:05]; mean [SD], hh:mm). As a result, there was a large cumulative sleep debt at race completion, which was not 'reversed' in the post-race period (up to 1 week). The deterioration in all four self-reported scales of perceived impairment during the race period was largely restored in the post-race period. This is the first study to document objective sleep-wake behaviors and subjective impairment of adventure racers, in the context of two geographically diverse, multi-day, international adventure races. Measures of sleep deprivation indicate that sleep debt was extreme and did not recover to pre-race levels within 1 week following each race. Despite this objective debt continuing, perceived impairment returned to pre-race levels quickly post-race. Therefore, further examination of actual and perceived sleep recovery is warranted. Adventure racing presents a unique scenario to examine sleep, performance and recovery. Adventure, or expedition, racing is an ultra-endurance sport, carried out over multiple days, which presents an extreme test of athletic performance under conditions of severe sleep restriction and deprivation. However, limited research has been conducted to examine sleep and perceived impairment of athletes who choose this sport. Using actigraphy, the team-based nature of adventure racing was evident with severe sleep restriction synchronized between team members during the race. There was significant sleep debt accumulated across the race and was not recovered by the end of the measurement period. Furthermore, perceived impairment returned to pre-race levels quickly after race completion, despite the remaining sleep debt objectively observed. This study posits that adventure racing presents a unique context to study sleep, performance, and recovery.