Quantifying the effect of afternoon moderate-intensity exercise on sleep quality and quantity in healthy adult males using polysomnography.

Objectives: To investigate the effect of afternoon moderate-intensity cycling exercise on objective and subjective sleep in healthy adult males.

Design: Repeated-measures, counter-balanced, crossover study design.

Methods: To assess the effect of moderate-intensity afternoon exercise on sleep quality and quantity, 12 healthy adult males who were identified as good sleepers (<5 on Pittsburgh Sleep Quality Index) completed either moderate-intensity cycling exercise for 40 min at 70 % HRmax at ~15:30 h or sedentary activities. Polysomnography was used to measure sleep during a 9-hour sleep opportunity (23:00 h to 08:00 h). Sleep was subjectively assessed using questionnaires 30 min after waking.

Results: There were no statistically significant changes in objective or subjective sleep quality or quantity between conditions. The inter-quartile range for total sleep time (exercise: 51.5 min vs no exercise: 13.4 min) and sleep efficiency (exercise: 9.5 % vs no exercise: 2.5 %) suggests that there was more individual variability in subsequent sleep after afternoon exercise compared to no exercise. Exercise appeared to have a moderate effect on reducing total sleep time (mean ± SD; control 493.7 ± 12.6 min vs exercise: 471.5 ± 55.2 min; Cohen's d: -0.56), sleep efficiency (control 91.4 ± 2.3 % vs exercise: 87.3 ± 10.2 %; Cohen's d: -0.56), and delaying REM onset latency (control: 76.1 ± 45.1 min vs exercise: 102.8 ± 46.9 min; r: 0.33), although the results did not reach statistical significance (p > 0.05).

Conclusions: Healthy adult males can complete moderate-intensity exercise in the afternoon without compromising subsequent sleep. Individual responses in objective sleep outcomes may vary after exercise.