Exercise too close to bedtime may affect sleep duration, timing and quality, new research led by Monash University has found. More strenuous workouts closer to bedtime coincided with greater disruptions to sleep and nighttime cardiac activity.
Published in Nature Communications, the study found that exercising four hours or less before bedtime was linked to falling asleep later, getting less and worse quality sleep, and having a higher resting heart rate and lower heart rate variability. It is the first and largest study to identify this.
The study involved an international sample of 14,689 people monitored across one year, resulting in four million nights of data. They wore a multi-sensor biometric device (WHOOP Strap) to record exercise, sleep and cardiovascular data.
Monash and WHOOP researchers examined the relationships between evening exercise, exercise strain, sleep and nocturnal cardiac activity, including resting heart rate and heart rate variability.
The combination of later exercise timing and higher exercise strain was associated with delayed sleep onset, shorter sleep duration, lower sleep quality, higher nocturnal resting heart rate and lower nocturnal heart rate variability.
The results were adjusted for gender, age, weekday, season, general fitness and the prior night’s sleep. High strain exercise includes activities that lead to sustained increases in breathing rate, core body temperature, heart rate and mental alertness.
Examples include HIIT workouts (high-intensity interval training), football and rugby games or a long run.
First author Dr Josh Leota, from the Monash University School of Psychological Sciences, said he wanted to shed light on “the important yet puzzling” link between the timing of exercise and sleep.
“Intense exercise in the evening can keep the body in a heightened state of alertness, which is why public health guidelines have previously advised against working out too close to bedtime. However, findings from controlled laboratory studies are less conclusive, with many suggesting that evening exercise doesn’t necessarily disrupt sleep,” he said.
“These studies have relied on small sample sizes and laboratory settings, and rarely involved exercise bouts that elicit substantial cardiometabolic demand on the body, calling into question the external validity of such findings.”
Dr Leota said the new study’s findings suggested that if people were aiming to improve sleep health, they may benefit from concluding exercise at least four hours before their bedtime.
“If exercising within a four-hour window of bedtime, people could choose brief low intensity exercises, such as a light jog or swim, to minimise sleep disruption and allow the body to wind down,” he said.
Senior author Dr Elise Facer-Childs, from the Monash University School of Psychological Sciences, said the results demonstrated a clear and consistent relationship across all outcome variables.
“Evening exercise—particularly involving high levels of cardiovascular strain—may disrupt subsequent sleep, resting heart rate, and heart rate variability, thereby impairing a critical stage of the recovery process,” Dr Facer-Childs said.
“Our novel and timely findings have significant implications for public health messaging around timing, duration and intensity of exercise and present a critical step towards improving population sleep health—an issue of central importance given two in three Australian adults report at least one sleep problem and one in five adults fail to achieve the recommended seven or more hours of sleep per night."
DOI: 10.1038/s41467-025-58271-x
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