Short bursts of resistance exercise at night ‘may improve sleep length’

They found that three-minute bursts of activity, which they refer to as breaks, every half hour for four hours may be all that is needed to improve sleep length.

“These results add to a growing body of evidence that indicates evening exercise does not disrupt sleep quality”

Study authors

The authors of the study, published in the journal BMJ Open Sport & Exercise Medicine, acknowledge that the findings run counter to usual recommendations that discourage exercise before bed.

They note that intense exercise is normally discouraged before going to bed, on the grounds that it increases body temperature and heart rate, which can result in poorer sleep quality.

The researchers, from the University of Otago, also highlighted that poor sleep was associated with an increased risk of cardiometabolic disorders, such as coronary heart disease and type 2 diabetes.

As a result, they recruited 30 non-smokers, aged 18 to 40, to their study, which was funded by the Health Research Council of New Zealand.

All the participants reported clocking up more than five hours of sedentary time during the day at work and two hours in the evening.

Participants wore an activity tracker continuously on their non-dominant wrist for seven consecutive days and were asked to record when they did not wear it, when they went to bed and woke up.

They were also asked to record any physical activity when not wearing the activity tracker.

Each of them completed two four-hour sessions in a controlled laboratory environment on the same day of the week, starting at around 17:00-17:30, and separated by a minimum period of six days.

In one session, participants remained seated for four hours. In the other, they did three minutes of simple resistance exercise every 30 minutes over the four-hour period.

Each activity break included three rounds of three exercises – chair squats, calf raises, and standing knee raises with straight leg hip extensions for 20 seconds each, in time with a video recording.

Data showed that, before the experiment, participants spent an average of seven hours 47 minutes asleep, 10 hours 31 minutes sitting, and four hours 55 minutes doing vigorous physical activity a day.

The results, which are based on 28 participants, showed that after the activity breaks, participants slept for an additional 27 minutes on average, compared with prolonged sitting.

The average sleep duration after the activity breaks was seven hours 12 minutes, compared with six hours and 45 minutes after prolonged sitting.

Participants woke, on average, at 7:35 am after the prolonged sitting intervention and 8:06 am after regular activity breaks.

There were no significant differences in uninterrupted sleep or number of awakenings between the two interventions, indicating that activity breaks did not disrupt sleep, said the researchers.

The researchers emphasised that further studies, involving larger numbers of people in their normal home environment and for a longer period, were now needed.

However, they said: “These results add to a growing body of evidence that indicates evening exercise does not disrupt sleep quality, despite current sleep recommendations to the contrary.”

They noted: “Adults accrue the longest periods of sedentary time and consume almost half their daily energy intake during the evening, added to which insulin sensitivity is lower at this time.”

By extending sleep duration, especially in those who sleep less than the recommended nightly total, activity breaks may potentially reduce cardiometabolic disease risk over the long term, they said.