Do power naps save sleepiness? Cognitive benefits of brief sleep during a 100 miles ultramarathon.

OBJECTIVES

This study aimed to investigate the effects of short naps on perceived sleepiness and cognitive vigilance during extreme sleep deprivation in ultra-endurance racing. It tested whether baseline cognitive performance predicts nap decisions and if 20-min naps enhance objective cognitive function while reducing subjective sleepiness.

DESIGN

An observational field study was conducted during the 2022, 2023, and 2024 editions of the Ultra-Trail du Mont-Blanc® (170 km; ∼10 000 m elevation gain).

METHODS

Sleep was recorded via wrist accelerometery for 52 completing runners (43.9 ± 8.3 years). Subjective sleepiness (Karolinska Sleepiness Scale, KSS) and reaction time (Psychomotor Vigilance Test, PVT) were assessed at five checkpoints (CP0-CP4). At CP1-CP3, participants chose between a 20-min sleep opportunity (nap group, NG) or remaining awake (awake group, AG). Measurements occurred at checkpoint entry (ENT) and 1 km post-checkpoint.

RESULTS

Finishers slept an average of 28.4 ± 21.9 min. Linear mixed-effects models confirmed robust circadian modulation of both sleepiness and reaction times. Nap decisions were primarily driven by subjective sleepiness rather than objective vigilance deficits. While 20-min naps produced immediate reductions in KSS 1 km post-checkpoint, cognitive benefits (PVT) manifested more gradually, with significantly faster reaction times observed only at subsequent checkpoints.

CONCLUSIONS

Brief naps serve as an effective reactive strategy to reduce perceived drowsiness and provide partial protection against late-race performance decline without compromising overall race completion times.