After sitting at the office for hours during the day, we tend to go home and sit a few hours more before bedtime.

Not good for you: Cancer, heart disease and diabetes are more likely to creep in with all that sitting, fixed in place.

To offset the negative effects of sitting down too long requires a lot of physical activity.

This is best done in chunks that break up the sitting sessions.

So where do you find the time?

The evening, going into the night, is an obvious option.

But for years, the advice was to avoid exercise at night, particularly close to bedtime.

It was thought that late-in-the-day vigorous exercise, especially, can cause poor sleep by raising your body temperature, heart rate and adrenaline levels.

And the cumulative effects of poor sleep include an increased risk of hypertension, diabetes, obesity, depression, heart attack and stroke.

So … if your sloth doesn’t get you, your lack of sleep will.

That damn rock and a hard place!

Relax. The advice against exercising before bedtime has softened.

Vigorous exercise should be completed within an hour of hitting the hay.

But gentler forms of exercise are probably OK up to the point of taking off your slippers.

A small new study found that three minutes, every half hour, of simple resistance exercise – in the evening – “could help you sleep for longer that night”.

In other words, instead of exercise having a neutral or negative effect on sleep, these three-minute breaks from sitting still delivered more sleep.

What was the study? 

Researchers from the University of Otago recruited 30 non-smokers, aged 18 to 40.

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

To establish “habitual physical activity and sleep patterns, participants wore an activity tracker worn continuously on their non-dominant wrist for seven consecutive days”.

Periods they didn’t wear the tracker, the time they went to bed, and when they woke up, were all recorded.

They recorded any physical activity when not wearing the activity tracker, such as swimming or contact sport. They also reported activities “known to be inaccurately identified by the tracker, such as stationary cycling or yoga”.

Then the experiment began in earnest. 

On two days, about a week apart, they spent four hours in a lab from about 5pm.

In one of the sessions, the participants sat for the entire four hours.

In the other session, they completed “an equipment-free, three-minute resistance exercise program every half hour”.

These included three rounds of three exercises: Chair squats, calf raises, and standing knee raises with straight leg hip extensions for 20 seconds each.

Each exercise was done “in time with a video recording of a person doing the same exercises”.

When the four hours were up, the participants “returned to their normal, real-life environment”. That is, they went home or to the pub. 

The results

Based on 28 participants (there were two dropouts), the results showed that “after the activity breaks, participants slept for an additional 27 minutes on average, compared with prolonged sitting”.

The average sleep duration was 7 hours 12 minutes, compared with 6 hours and 45 minutes after prolonged sitting.

And while the time at which participants attempted to go to sleep was more or less the same, average wake times differed.

Participants woke, on average, at 7.35am after the prolonged sitting intervention and 8.06am after regular activity breaks.

There were no significant differences in uninterrupted sleep between the two interventions. Nor were their differences in the number of awakenings during the night.

This indicates that activity breaks didn’t disrupt sleep.

This was a fairly small study in a lab setting.

Further studies “involving larger numbers of people, in their normal home environment, are needed”.