Exercise Before Bed Could Ruin Your Sleep

Exercise is a good thing, but a good thing at the wrong time might not be so good. New research from Monash University in Australia shows that exercising too close to bedtime may disrupt your sleep in ways such as duration, timing and quality.

The study consisted of nearly 15,000 people having their sleep monitored for a year. That meant scientists had more than four million nights of data to analyze.

Participants wore a multi-sensor biometric device called a Whoop Strap that measured exercise, sleep, and cardiovascular data. That was used to examine the relationship between evening exercise, exercise intensity and sleep, as well as nocturnal cardiac activity like resting heart rate and heart rate variability.

Researchers found exercising four hours or less before bedtime was linked to study subjects falling asleep later and getting less sleep. They also had worse sleep quality, a higher resting heart rate and lower heart rate variability.

The results were adjusted for gender and age, as well as the day of the week, the season of the year and the fitness level of the participant. Researchers also took into consideration the previous night's sleep.

The study showed the more strenuous the workout and the closer to bedtime, the greater the impact on sleep disruption and nighttime cardiac activity. High strain exercises were those considered to have caused a sustained increase in breathing rate, core body temperature, heart rate and mental alertness.

"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," study author Dr. Josh Leota said. "However, findings from controlled laboratory studies are less conclusive, with many suggesting that evening exercise doesn't necessarily disrupt 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."

Leota recommended people conclude their workout at least four hours before bedtime. If not, then to tailor their routine to accommodate their need for quality sleep.

"If exercising within a four-hour window of bedtime, people could choose brief low-intensity exercises, such as a light jog or swim, to minimize sleep disruption and allow the body to wind down," he said.

Click here to read more in the journal Nature Communications.