The effect of prior endurance training on nap sleep patterns.

PURPOSE: The use of daytime napping as a recovery tool following exercise is virtually unexplored. The objective of this study was to assess the quality of daytime nap sleep following endurance training in an athletic population, and to appraise the optimal circadian timing of the nap and the time interval between training and the nap.

METHODS: Six physically trained male subjects (22.5+/-2.4 y) performed four separate standardized 90-min endurance training sessions followed by a 90-min daytime nap either 1 or 2 h after training (time interval), commencing at either 10:30 or 11:30 (circadian timing). During the nap, sleep was monitored using polysomnography. Subjective measurements of sleep quality, alertness and preparedness to train following a nap were recorded using a visual analog scale.

RESULTS: The duration of slow wave sleep (SWS) was significantly greater during the 11:30 naps (13.7+/-9.0 min) compared with the 10:30 naps (6.9+/-8.8 min) (P=.049). There was no significant difference in SWS duration between a 1-h (10.6+/-10.2 min) or 2-h (10.0+/-9.0 min) time interval between training and the nap (P=.82). No other sleep variables differed significantly according to circadian timing or time interval.

CONCLUSION: Recovery naps commenced later in the morning contain more SWS than earlier naps. The data imply that daytime naps have a potential role as a valuable recovery tool following endurance exercise, given the suggested energy restorative functions of SWS.