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Shifting physical training from morning to afternoon improves sleep health and morale in soldiers

Q: Does shifting physical training to afternoon increase total sleep duration?

No, the study found no significant difference in total sleep duration per 24 hours between morning and afternoon PT schedules (P = .38).

Q: What sleep outcomes improved after shifting to afternoon PT?

Sleep quality (PSQI), daytime sleepiness (Epworth), and insomnia symptoms (ISI) all significantly improved after ~30 days of afternoon PT.

Q: Did afternoon PT affect mental health or morale?

Morale significantly improved, while stress and anxiety remained at low to moderate levels and did not differ between schedules.

Q: How long was the intervention period?

Soldiers followed the morning PT schedule for ~30 days and then the afternoon PT schedule for ~30 days, with assessments at the end of each period.

In a study of 37 active-duty soldiers, shifting physical training from 6:30 AM to 2:00 PM for approximately 30 days did not change total sleep duration per 24 hours (t28 = -0.31, P = .38) but significantly improved sleep quality (PSQI; t33 = 2.60, P < .01), daytime sleepiness (Epworth; t33 = 2.88, P < .01), and insomnia symptoms (ISI; t33 = 2.14, P = .02). Morale also significantly improved (t34 = -2.04, P = .03), while stress and anxiety remained similar.

Last updated: Aug 10, 2026•0 RCTs•📖 Read as article →

Evidence Score

Evidence Score34/100

Human RCT☆☆☆☆☆

Meta-analysis☆☆☆☆☆

Mechanism★★★★★

Safety★★★★☆

Confidencelow

Study Evidence

Study 1. Shifting From Morning to Afternoon Physical Training Is Associated With Improved Sleep Health, Morale, and Operational Readiness in Soldiers.

observational

Negash B, Krslovic K, Fong C, Carlsson K, Krauss MAJS, Jones MAJR, Burke TM, Alger SE · Military medicine (2026)

Participants: 37

Duration: ~60 days (30 days morning PT + 30 days afternoon PT)

Intervention: Behavioral intervention shifting physical training from morning (6:30 AM) to afternoon (2:00 PM) for ~30 days

Outcome: Sleep quality (PSQI), daytime sleepiness (Epworth), insomnia symptoms (ISI), morale, stress, anxiety, total sleep duration

Effect Size: N/A (only t-values and P-values reported)

Population: 37 active-duty U.S. Army soldiers

Result: In a study of 37 active-duty soldiers, shifting physical training from 6:30 AM to 2:00 PM for approximately 30 days did not change total sleep duration per 24 hours (t28 = -0.31, P = .38) but significantly improved sleep quality (PSQI; t33 = 2.60, P < .01), daytime sleepiness (Epworth; t33 = 2.88, P < .01), and insomnia symptoms (ISI; t33 = 2.14, P = .02). Morale also significantly improved (t34 = -2.04, P = .03), while stress and anxiety remained similar.

PubMed: 42560254 DOI: 10.1093/milmed/usag054

Mechanism Graph

Morning PT requires early wake-up, reducing opportunity for sleep

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Shifting PT to afternoon allows soldiers to sleep later

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Improved sleep opportunity leads to better sleep quality and reduced daytime sleepiness

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Improved sleep health and morale enhance operational readiness

Limitations

⚠Small sample size (n=37) and single military unit, limiting generalizability
⚠No objective sleep measures (e.g., actigraphy or polysomnography); relied on self-report surveys
⚠Potential confounding factors such as seasonal changes, workload, or leadership support not controlled

Frequently Asked Questions

Does shifting physical training to afternoon increase total sleep duration?▼

No, the study found no significant difference in total sleep duration per 24 hours between morning and afternoon PT schedules (P = .38).

What sleep outcomes improved after shifting to afternoon PT?▼

Sleep quality (PSQI), daytime sleepiness (Epworth), and insomnia symptoms (ISI) all significantly improved after ~30 days of afternoon PT.

Did afternoon PT affect mental health or morale?▼

Morale significantly improved, while stress and anxiety remained at low to moderate levels and did not differ between schedules.

How long was the intervention period?▼

Soldiers followed the morning PT schedule for ~30 days and then the afternoon PT schedule for ~30 days, with assessments at the end of each period.

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References

1.Negash B, Krslovic K, Fong C, Carlsson K, Krauss MAJS, Jones MAJR, Burke TM, Alger SE. "Shifting From Morning to Afternoon Physical Training Is Associated With Improved Sleep Health, Morale, and Operational Readiness in Soldiers.." Military medicine, 2026. PMID: 42560254 DOI: 10.1093/milmed/usag054

Disclaimer: This content is for educational purposes only and is not medical advice. Evidence scores reflect the quality and quantity of available research, not clinical recommendations. Always consult a healthcare professional before starting any supplement or intervention.