Does Training Late Effect Sleep Quality?
A look at how evening exercise timing and intensity affect sleep.
This large-scale study investigated how evening exercise's timing and intensity (strain) affect sleep quality, duration, and nocturnal autonomic function in physically active adults.
Key Points
Aim:
To determine whether the combination of later exercise timing and higher exercise strain disrupts sleep and nocturnal autonomic activity, and to establish practical recommendations for minimising negative impacts.
Methods:
Sample: 14,689 adults (mean age ~38; 74% male) tracked over one year, yielding over 4 million nights of data.
Data Collection: Participants wore a validated wrist-worn biometric device to objectively measure exercise timing, intensity (strain), sleep onset, duration, quality, resting heart rate (RHR), and heart rate variability (HRV).
Analysis: Examined dose-response relationships between how close to bedtime exercise ended, the strain of the exercise, and sleep/autonomic outcomes.
Results
Timing and Strain Matter:
The later and more strenuous the exercise, the more likely it was to delay sleep onset, shorten sleep duration, reduce sleep quality, increase nocturnal RHR, and decrease nocturnal HRV.
Safe Window:
Exercise ending 4 or more hours before sleep onset (regardless of strain) did not negatively affect sleep or nocturnal autonomic function.
Negative Effects When Closer to Bedtime:
If exercise ended within 4 hours of sleep onset, especially with higher strain, negative effects increased in a dose-dependent way:
Sleep onset: Maximal strain exercise ending 2 hours before sleep onset delayed sleep by 36 minutes; if ending 2 hours after, by 80 minutes.
Sleep duration: Maximal strain exercise ending 2 hours before sleep onset reduced sleep by 22 minutes; if ending 2 hours after, by 43 minutes.
Sleep quality: Maximal strain exercise ending 2 hours before sleep onset reduced sleep quality by 0.87 percentage points; if ending 2 hours after, by 5.6 points.
Nocturnal RHR: Increased by up to 15% (9.4 bpm) after maximal strain exercise ending 2 hours after sleep onset.
Nocturnal HRV: Decreased by up to 32.6% (14.6 units) after maximal strain exercise ending 2 hours after sleep onset.
Light/Moderate Exercise:
Light or moderate exercise that ended more than 2 hours before sleep had negligible or no negative effects on sleep or autonomic function.
Consistency Across Demographics:
Effects did not differ by gender, age, or BMI.
Practical Takeaways
Finish strenuous exercise at least 4 hours before bedtime to avoid negative impacts on sleep and recovery.
If exercising closer to bedtime, opt for lighter or moderate-intensity sessions to minimise disruption.
Monitor recovery: High-strain sessions, especially late in the evening, can impair both sleep quality and the body’s overnight recovery processes (as indicated by higher RHR and lower HRV).
Sleep health and performance: For athletes and fitness peeps, proper management of exercise timing and intensity can help maximise both training adaptation and sleep quality.
Related
Key Takeaways
Strenuous evening exercise close to bedtime can significantly disrupt sleep and overnight recovery.
Allow at least a 4-hour buffer between high-intensity workouts and sleep.
Lighter exercise is generally safe even if performed closer to bedtime.
These findings apply broadly, regardless of age, gender, or body type.
Bottom Line:
Avoid high-intensity workouts within 4 hours of bedtime for the best sleep and recovery. If you must work out late, keep it light or moderate. This approach helps ensure your sleep quality, duration, and overnight recovery are not compromised.
Reference
Leota, J., Presby, D. M., Le, F., Czeisler, M. É., Mascaro, L., Capodilupo, E. R., Wiley, J. F., Drummond, S. P., Rajaratnam, S. M., & R., E. (2025). Dose-response relationship between evening exercise and sleep. Nature Communications, 16(1), 1-9. https://doi.org/10.1038/s41467-025-58271-x