A long late-night run may help you meet your daily exercise goals, but can lead to disrupted sleep.
New research from Monash University found exercise too close to bedtime may affect sleep duration, timing and quality, with more strenuous workouts closer to bedtime coinciding with greater disruptions to sleep and nighttime cardiac activity.
Study first author Josh Leota said 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.
Dr Leota said it was the first and largest study to identify this and involved an international sample of 14,689 people monitored across one year, resulting in four million nights of data, with results were adjusted for gender, age, weekday, season, general fitness and the prior night’s sleep.
He said high strain exercise included activities that led 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.”
Dr Leota said intense exercise in the evening could keep the body in a heightened state of alertness, which was why public health guidelines had 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.
Read the full study: Dose-response relationship between evening exercise and sleep.
