Purpose It has been suggested that napping is the best recovery strategy for athletes. However, researches on the impacts of napping on athletic performances are scarce. The aim of this study was to determine the effects of a 30-min nap after a partial sleep deprivation, or a normal night condition, on alertness, fatigue, and cognitive and physical outcomes. Methods Thirteen national-level male karate athletes were randomized to experience nap and no-nap conditions, after either a reference or a partial sleep deprivation night. The nap lasted 30 min at 1:00 pm. The postnap testing session started at 2:00 pm by quantifying subjective alertness and fatigue. Cognitive and physical performances were respectively measured before and after the karate-specific test (KST) by simple reaction time (SRT) test, lower reaction test (LRT), mental rotation test (MRT), squat jump (SJ), and counter movement jump (CMJ) tests. Results After a reference night, the nap improved alertness and cognitive outcomes (SRT, LRT, and MRT). No effects on subjective fatigue and physical performances were found. After a partial-sleep deprivation, the nap restored subjective alertness and the decrement in performances caused by sleep loss in most of the tests (MRT, LRT, and KST), but no effects were observed in subjective fatigue and CMJ. After the fatigue induced by KST, there was an ergogenic effect of the nap on the physical performances (CMJ and SJ), and a partial psychogenic effect on the cognitive performances (LRT). Conclusions A 30-min nap enhances cognitive outcomes. It is also an effective strategy to overcome the cognitive and physical deteriorations in performances caused either by sleep loss or by fatigue induced by exhaustive trainings in the afternoon.

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