Research shows that current recommendations that discourage exercise before bedtime are being revised

Findings from a small comparative study published in the open access journal BMJ Open Sports and Exercise Medicine suggest that ‘activity breaks’ with resistance exercise at night can improve sleep length. A three-minute break every 30 minutes over a four-hour period may be sufficient, the findings show.

Current recommendations discourage vigorous exercise before bed because it increases body temperature and heart rate, which can result in poorer sleep quality, the researchers say.

Although activity breaks may improve metabolism after a meal, it is not clear whether they have any impact on sleep. Poor sleep is associated with an increased risk of cardiometabolic diseases, such as coronary heart disease and type 2 diabetes, the researchers explain.

To investigate this further, the researchers recruited 30 non-smokers aged 18 to 40 for their study. They all reported doing more than five hours of sitting at work during the day and two hours in the evening.

To record habitual physical activity and sleep patterns, participants wore an activity tracker worn continuously on their non-dominant wrist for seven consecutive days. And they were asked to record the periods when they weren’t wearing it, the time they went to bed and when they woke up.

They were also asked to record any physical activity when they were not wearing the activity tracker, such as swimming or contact sports, and to record activities known to be inaccurately identified by the tracker, such as stationary cycling or yoga.

Each participant completed two four-hour sessions in a controlled laboratory environment on the same day of the week, starting around 5:00–5:30 PM, with a minimum of six days apart.

In one session, participants sat for four hours; in the other, they did three minutes of simple resistance exercises every 30 minutes over a four-hour period. The participants then returned to their normal, real-life environment.

Each activity break included three rounds of three exercises: chair squats, calf raises, and standing knee raises with straight hip extensions of 20 seconds each, timed with a video recording of a person doing the same exercises.

The Activity Tracker data showed that before the experiment, participants slept an average of seven hours and 47 minutes, sat for 10 hours and 31 minutes, and spent four hours and 55 minutes per day in vigorous physical activity.

Three in four slept the recommended seven hours a night, while the rest slept less than that (21%) or more than nine hours (4%).

The results, which are based on 28 participants, show that participants slept an average of 27 extra minutes after activity breaks, compared to sitting for long periods of time.

The average sleep duration was seven hours and 12 minutes, compared to six hours and 45 minutes after prolonged sitting. And while the time at which participants tried to go to sleep was more or less the same, the average wake-up times differed. Participants woke up on average at 7:35 a.m. after the prolonged sitting intervention and at 8:06 a.m. after regular breaks.

Furthermore, there were no significant differences in sleep efficiency – uninterrupted sleep – or the number of awakenings during the night between the two interventions, indicating that breaks did not disrupt subsequent sleep, the researchers say.

There were no statistically significant differences in activity patterns in the 24 hours after each intervention. But compared to sitting for long periods of time, regular breaks resulted in 18 minutes less total physical activity – less than 2% of total waking time.

The researchers acknowledge several limitations to their findings. For example, the study involved small numbers of participants and was conducted in a laboratory setting, which may not reflect real-life behavior.

Further research among larger numbers of people in their normal home environment, and for a longer period, is therefore necessary, the researchers emphasize.

But nevertheless, they say, “These results add to a growing body of evidence indicating that evening exercise does not disrupt sleep quality, despite current sleep recommendations to the contrary.”

And they point out that “adults accrue the longest periods of sedentary time, consuming almost half of their daily energy intake in the evening, with insulin sensitivity being lower at this time.”

By increasing sleep duration, especially in those who sleep less than the recommended nightly total, activity breaks could potentially reduce the risk of cardiometabolic disease in the long term, they suggest.

The resistance exercises used in their study are easy to perform, require no equipment and can even be done while streaming content, potentially increasing the chances of sticking with the routine, they add.

They emphasize: “Although existing research indicates that evening exercise does not adversely affect sleep, the mechanisms by which it does so are [it] influences on sleep quality remain unclear.”