Is it wiser to train in the afternoon or the early evening to sleep better? the role of chronotype in young adolescent athletes

Study objectives: To examine the effect of the timing of high-intensity exercise (afternoon vs. evening) on adolescent athletes' bedtime psychological state, sleep quality, sleep staging, and next-day wellness/sleepiness according to chronotype.

Methods: Forty-two young athletes (morning type: n =12, intermediate type: n =14; evening type: n=16) completed a randomized crossover study under free-living conditions. The counterbalanced sessions include: (AEX) afternoon (1:00 - 3:00 pm) and (EEX) evening (5:30 - 7:30 pm) high-intensity exercise. Sessions were conducted over three days each and were separated by a 1-week washout period. The time in bed was fixed (10:30 pm - 7:30 am). Sleep was assessed through ambulatory polysomnography.

Results: The effect of high-intensity exercise on sleep differs significantly depending on the time of exercise with lower sleep efficiency: SE (-1.50%, p
Conclusions: Exercise timing and chronotype affect the psychological state at bedtime and objective sleep in adolescent athletes. This also alters next morning signs of pre-fatigue and wellness which suggest that the consideration of both features is important to adolescent athletes' recovery.