People cite many reasons for why they don’t exercise in the evening. “Too busy” and “too tired” are the most common excuses. But there’s also the longstanding popular belief that engaging in vigorous exercise in the evening should be avoided because it can interfere with getting a good night’s sleep.
A small but intriguing new study from Australia suggests, however, that we may not have to worry about the sleep bit. Its authors found that 30 minutes of high-intensity exercise in the evening doesn’t affect sleep — and may even help quash late-night hunger pangs.
The study also found that people’s physical performance — specifically their ability to do sprints while cycling — was higher when exercising later in the day.
The study was published online Friday in the journal Experimental Physiology.
How the study was done
For the study, researchers at Charles Sturt University in Bathurst, Australia, recruited 11 healthy but relatively inactive (less than 150 minutes of exercise per week) middle-aged men. Their mean age was 49, and none had sleep problems or medical conditions that affect sleep.
The men were brought into a lab on three different days to exercise for 30 minutes on a cycling machine. (They had restrained from exercising for the previous 24 hours.) The exercise was a high-intensity workout — six one-minute, all-out sprints followed by four minutes of rest.
Each workout was done at a different time of the day: morning (6 to 7 a.m.), afternoon (2 to 4 p.m.) and evening (7 to 9 p.m.). The participants’ sleep — including their sleep stages and how often they awoke during the night — was monitored the evening after the workout with a take-home polysomnography device. The men also filled out questionnaires about their post-exercise appetite and food intake.
Blood tests were taken before and after each exercise session.
The study found that exercising in the evening had no significant impact on sleep patterns, including time falling asleep, time waking up and total sleep time. Nor did it have an effect on sleep efficiency, although the men tended to spend a bit more time in non-dream sleep after an evening workout than when they exercised at other times of the day.
The study also found that exercising in the afternoon and in the evening — but not in the morning — was associated with greater reductions of the hormone ghrelin.
Importantly, however, the study did not find that the participants reported being less hungry — or ate less food — after their afternoon or evening workouts.
The men were able to put more oomph into those workouts, however.
“Power output during the sprint efforts was higher for the afternoon and evening trials compared to the morning trial, indicating that participants were able to perform better during latter parts of the day. Therefore, time-of-day may also need to be considered when planning training schedules,” said Penelope Larsen, the study’s lead author and a Ph.D. student in sports health, in a released statement.
The study comes with several significant limitations — most notably, it’s small size and the fact that all its participants were middle-aged Australian men.
Still, the findings are consistent with other research that has suggested that vigorous exercising close to bedtime does not — despite the widespread belief — interfere with sleep.
“In the future, we hope to conduct similar studies recruiting women to determine whether sleep and appetite responses may be different depending on sex,” said Larsen.
“This study only considered a single bout of exercise,” she added. “Therefore, it would be beneficial to investigate long-term sleep and appetite adaptions to high-intensity exercise training performed either in the morning, afternoon or evening.”
After all, exercise is key to good health.
No more excuses.
FMI: You can download and read the study in full through Experimental Physiology’s website.