Purpose: To compare the effect of different durations of nap opportunity during the daytime on repeated high-intensity short-duration performance and rating of perceived exertion (RPE).
Methods: Seventeen physically active men (age: 21.3 ± 3.4 years, height: 176.7 ± 5.9 cm, body mass: 71.8 ± 10.2 kg) performed a 5 m shuttle run test [to determine best distance (BD), total distance (TD), and fatigue index (FI)] under four conditions: a 25 min nap opportunity (N25), a 35 min nap opportunity (N35), a 45 min nap opportunity (N45), and control condition (no-nap) (N0). The sleep quality of each nap opportunity was evaluated using a scale ranging from 0 "no sleep" to 10 "uninterrupted, deep sleep throughout." The four conditions were performed in a random order. RPE was recorded after each repetition of the 5 m shuttle run test and the mean score was calculated.
Results: BD increased after N25 (+6%) and N45 (+9%) compared to N0 (p < 0.05) and was significantly higher after N45 compared to N35 (p < 0.05). Compared to N0, the three nap opportunity durations enhanced TD (p < 0.05) with greater enhancement after N45 compared to N25 (+8% vs. +3%) and N35 (+8% vs. +3%). For FI, no-significant differences were observed between the three nap opportunity durations and N0. The mean RPE score was significantly higher after N25 (+20%) and N0 (+19%) compared to N45 (p < 0.05). All participants were able to fall asleep during each nap condition with a sleep quality score of 6.9 ± 1.0, 7.0 ± 0.7, and 7.1 ± 0.8 for N25, N35, and N45.
Conclusion: A nap opportunity during the daytime was beneficial for physical performance and perceived exertion with the N45 being the most effective for improving performance and reducing fatigue during the 5 m shuttle run test. The implication of the present study is that athletes might benefit from a nap opportunity of 25, 35 or 45 min before practice or before a competition.
Keywords: exercise; fatigue; nap; sleep; sport.