Shifting From Morning to Afternoon Physical Training Is Associated With Improved Sleep Health, Morale, and Operational Readiness in Soldiers.

INTRODUCTION: Sufficient sleep is critical to optimal physical, cognitive, and mental health, yet two-thirds of U.S. Army Soldiers chronically obtain less than the daily recommended 7 or more hours of sleep. Early morning physical training (PT) could impede the amount and quality of sleep soldiers obtain, thereby impairing overall health and operational readiness. MATERIALS AND METHODS: This study examined the effects of a behavioral intervention, in which PT was shifted from morning to afternoon (at 2:00 PM), on measures of sleep health, mental health, and morale. Thirty-seven active-duty soldiers completed surveys along with cognitive and physical testing at 2 timepoints: after ∼30 days following a morning PT schedule (6:30 AM) and again after ∼30 days of an afternoon PT schedule. RESULTS: Although total sleep duration per 24 hours was not found to differ between PT schedules (t28 = -0.31, P = .38), measures related to general sleep health were significantly improved. Specifically, sleep quality (Pittsburg Sleep Quality Index; t33 = 2.60, P < .01), daytime sleepiness (Epworth Sleepiness Scale; t33 = 2.88, P < .01), and insomnia symptomology (Insomnia Severity Scale; t33 = 2.14, P = .02) were all significantly improved after shifting to afternoon PT. Furthermore, although subjective mental health metrics of stress and anxiety remained similar (low to moderate) between PT schedules, morale was significantly improved following an afternoon PT schedule (t34 = -2.04, P = .03). CONCLUSIONS: These findings indicate that a simple intervention of shifting PT timing from early morning to afternoon to allow for more opportunity to sleep, supported by leadership, can lead to improved sleep health and morale, which can improve overall operational readiness for active-duty service members.