 57 participants aged 15 to 19 years old were grouped into nap and no nap groups. Both groups took part in a 15-day protocol that started with 2 9-hour adaptation and baseline nights, followed by two successive cycles of sleep restriction 5-h time-in-bed TIB; 01:00-06:00 and recovery 9-h TIB; 23:00-08:00 intended to simulate the weekday sleep loss and weekend attempt to catch up that are familiar to high school students. The nap group received a 1-hour nap opportunity at 14:00 following each sleep-restricted night, while participants in the no nap group watched a documentary. Sleep was monitored with polysomnography on 9 selected nights. Cognitive performance, subjective sleepiness, and mood were assessed 3 times daily 10:00, 15:45, and 20:00. 