Healthcare (Commonwealth Union) – New research led by Monash University suggests that working out too close to bedtime can negatively impact how long you sleep, when you fall asleep, and how well you sleep. As sleep is a vital part of our lives the need to get effective sleep is often a key area of focus in research.
More intense exercise in the hours leading up to bedtime was linked to greater disturbances in sleep and nighttime heart function.
Published in Nature Communications, the study revealed that physical activity within four hours of going to bed was associated with delayed sleep onset, shorter and poorer quality sleep, elevated resting heart rate during the night, and reduced heart rate variability. This marks the first and largest study to document these patterns.
The research tracked 14,689 participants worldwide over the span of a year, collecting data from over four million nights using a WHOOP Strap—a wearable device that measures activity, sleep, and cardiovascular metrics.
Researchers from Monash and WHOOP analyzed how evening exercise and workout intensity affected sleep outcomes and heart activity during the night, focusing on metrics such as resting heart rate and heart rate variability.
The researchers have found that engaging in intense physical activity later in the day was linked to falling asleep later, reduced total sleep time, poorer sleep quality, a higher resting heart rate during the night, and decreased heart rate variability while sleeping.
These findings were controlled for factors such as gender, age, day of the week, season, overall fitness level, and sleep quality from the previous night. High-intensity workouts are those that significantly elevate breathing, body temperature, heart rate, and mental stimulation.
Examples of such activities include high-intensity interval training (HIIT), playing football or rugby, or going on a long-distance run.
Dr Josh Leota, the lead author from Monash University’s School of Psychological Sciences, stated that he aimed to explore the “important yet puzzling” relationship between when we exercise and how it affects our sleep.
He pointed out that while intense evening workouts can leave the body in a heightened state of alertness—leading public health advice to discourage late-night exercise—evidence from controlled lab studies tells a more nuanced story. He further pointed out that most of these studies suggest evening exercise doesn’t always interfere with sleep.
“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 stated that the study’s results indicated that those looking to support better sleep might benefit from finishing their workouts at least four hours before going to bed.
He indicated that for those who do choose to exercise closer to bedtime, opting for short, low-intensity activities like a gentle jog or swim could help reduce the risk of sleep disturbances and give the body a chance to relax.
Senior researcher Dr Elise Facer-Childs, also from Monash University’s School of Psychological Sciences, said the findings revealed a consistent pattern across all measures.
Dr Facer-Childs elaborated that engaging in vigorous evening workouts—especially those that put significant strain on the cardiovascular system—can negatively affect sleep quality, resting heart rate, and heart rate variability, which are all crucial for effective recovery.
“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.”
