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A recent study published in the open access journal BMJ Open Sport & Exercise Medicine suggests that short bouts of resistance exercise in the evening may enhance sleep duration. The study’s findings propose a potential revision of current guidelines that discourage exercise before bedtime, which are based on concerns that it might elevate body temperature and heart rate, leading to poorer sleep quality.
The research team aimed to investigate if activity breaks could positively impact sleep, given their known benefits on post-meal metabolism. Poor sleep is linked to an increased risk of cardiometabolic disorders, such as coronary heart disease and type 2 diabetes.
Study Design and Participants
To explore this hypothesis, the researchers recruited 30 non-smoking adults aged 18 to 40, who reported over five hours of sedentary time at work and two hours in the evening. Participants wore activity trackers on their non-dominant wrists for seven consecutive days to monitor their physical activity and sleep patterns. They recorded periods without the tracker, their bedtime, wake time, and any additional physical activities that were not detected by the tracker.
Each participant took part in two four-hour sessions in a controlled lab setting, separated by at least six days. During one session, participants remained seated for four hours. In the other, they performed three minutes of simple resistance exercises every 30 minutes, including chair squats, calf raises, and standing knee raises with straight leg hip extensions.
Key Findings
The activity tracker data revealed that participants averaged seven hours and 47 minutes of sleep per night, spent 10 hours and 31 minutes sitting, and engaged in nearly five hours of vigorous physical activity daily. Three-quarters of participants achieved the recommended seven hours of sleep per night.
After incorporating the activity breaks, participants slept an average of 27 minutes longer compared to prolonged sitting. The average sleep duration increased from six hours and 45 minutes to seven hours and 12 minutes. Notably, the activity breaks did not significantly affect sleep efficiency or the number of nighttime awakenings.
The study observed no significant differences in activity patterns in the 24 hours following each intervention. However, regular activity breaks resulted in 18 fewer minutes of total physical activity than prolonged sitting, amounting to less than 2% of total wake time.
Implications and Future Research
Despite the study’s small sample size and controlled lab environment, which may not reflect real-life behavior, the researchers suggest that their findings support the idea that evening exercise does not disrupt sleep quality. They emphasize the need for further studies involving larger groups of participants in their natural home settings over extended periods.
The study’s authors highlight that these findings add to the growing evidence that evening exercise does not adversely impact sleep, despite current recommendations. They note that evening is when adults typically experience the longest sedentary periods and consume almost half of their daily energy intake, coupled with lower insulin sensitivity.
By extending sleep duration, especially for those sleeping less than the recommended amount, evening activity breaks could potentially reduce the risk of cardiometabolic diseases over time. The simplicity of the resistance exercises, which require no equipment and can be done while streaming content, might encourage adherence to this routine.
The study concludes that while evening exercise may not negatively affect sleep, the underlying mechanisms remain unclear and warrant further investigation.
Reference
Evening regular activity breaks extend subsequent free-living sleep time in healthy adults: a randomised crossover trial, BMJ Open Sport & Exercise Medicine (2024). DOI: 10.1136/bmjsem-2023-001774
