Purpose: This work studied the acute effects in healthy adults of evening exercise timing on their quality of sleep and dietary intake over the following 12 h.
Methods: Sixteen men and women, (age: 22.3 ± 1.4 years; BMI: 20.8 ± 1.4 kg/m2, intermediate chronotype) took part in three randomized crossover sessions spread over three consecutive weeks: control session (CTL), 1 h exercise session at 6:30 pm (E6:30) and 1 h exercise session at 8:30 pm (E8:30), in which exercise finished 4 h and 2 h before habitual bedtime, respectively. Exercise was an outdoor run at 60% HRmaxth. Energy expenditure and sleep were ambulatories monitored by accelerometry under free-living condition. Ad-libitum dinner and breakfast were used to measure subsequent energy intake and proportion of that energy derived from each macronutrient.
Results: Evening exercise did not disrupt sleep. Improvement in sleep quality compared to the control condition was observed only when exercise was performed 4 h before habitual bedtime (WASO: p < 0.01; SE: p < 0.02). Interestingly, our results give insight into differences in sleep parameters response to evening exercise between habitually poor and good sleepers mainly when it comes to sleep efficiency and wake after sleep onset (all p < 0.01). There was no difference in calorie intake from ad-libitum dinner and breakfast. However, an association between improvement in sleep efficiency from acute exercise and reduction of energy intake the following morning was found.
Conclusion: Early evening exercise could offer a useful alternative for achieving better sleep in healthy young adults especially when it comes to poor sleepers.
Keywords: Accelerometry; Ad-libitum; College student; Energy balance; Sleep efficiency.