Individuals often choose between starting their day with a workout or going to the gym after work to relieve stress. Both approaches have their merits, as regular exercise offers numerous benefits such as reducing the risk of colorectal cancer and increasing lifespan. Meeting the recommended 150 minutes of exercise weekly can also lower the risk of over 200 diseases.
However, those who prefer exercising at the end of the day may inadvertently affect their sleep quality. According to Elise Facer-Childs, the lead author of a recent study published on April 15 in Nature Communications, evening workouts, especially those involving significant cardiovascular strain, might disrupt sleep, resting heart rate, and heart rate variability. This disruption can impede a crucial recovery phase.
Conducted by researchers from Monash University in Melbourne, Australia, the study found that exercising within four hours before bedtime was associated with falling asleep later, obtaining lower quality sleep, and experiencing a higher resting heart rate alongside lower heart rate variability. These effects were particularly noticeable after high-intensity evening workouts like high-intensity interval training (HIIT), soccer games, or long runs.
The study analyzed data from an international cohort of 14,689 participants over one year, resulting in four million nights of data. The participants used fitness monitors (WHOOP Strap) to track exercise, sleep, and cardiovascular metrics.
Previous research indicates that exercise generally enhances sleep quality and can aid sleep disorders such as insomnia. A study released earlier this year showed that exercise increases melatonin production, the hormone instrumental in regulating sleep cycles, and helps individuals fall asleep more quickly.
While some studies claim that evening exercise does not disturb sleep, the study’s authors underline that these findings often lacked conclusive evidence. Co-author Josh Leota stated that previous studies used small sample sizes and laboratory conditions and rarely involved exercise sessions that required high cardiometabolic demand, questioning their external validity.
Leota further explained that intense evening exercise can leave the body in a heightened state of alertness, which is why public health guidelines have previously recommended against working out too close to bedtime. Sleep is essential not only for improved workout performance and reduced injury risk but also for general recovery.
Researchers also observed that individuals who exercised close to bedtime exhibited lower heart rate variability, which correlates with a shorter lifespan, obesity, cardiovascular disease, inflammation, poor mental health, and weakened immunity. These exercisers also had a higher resting heart rate, indicating that the heart works harder than necessary to pump blood, signalling decreased efficiency. A high resting heart rate is linked with greater body weight, increased blood pressure, and reduced physical fitness, as noted by the American Heart Association.
Based on the study’s findings, Leota suggested that those aiming to improve sleep health should consider exercising at least four hours before bedtime. Alternatively, if exercising within four hours of sleep, individuals might opt for low-intensity activities such as a light jog or swim to minimize sleep disruptions and allow the body to relax.
The original story can be found on Fortune.com.
