New research suggests that short bursts of exercise may be better than long drawn-out PE classes in fighting childhood obesity.
In a study of Scottish schoolkids, researchers found that those who did 30-second sprints interspersed with breaks for just a few minutes produced better results than youngsters exercising more moderately for 30 minutes.
According to experts, this approach could be used in schools to improve the fitness of pupils, with the time saved spent teaching them about health and nutrition.
Professor Julien Baker and Duncan Buchan, from the University of the West of Scotland, conducted tests with teenagers at Holy Cross High School in Hamilton.
The pupils were split into three groups of 25. One group carried out high intensity activity, exercising three times a week for four minutes, with 30 seconds of sprinting followed by 30 seconds of rest.
The next group carried out moderate activity, exercising three times a week for 30 minutes. The last control group just did their usual PE lessons.
At the start and end of the eight-week study, the researchers measured body fat, blood pressure, activity and agility as well as testing blood for signs of good cardiovascular health.
Baker said the short bursts of exercise appeared more effective at improving health.
"The high intensity exercise group exercised for about 80 per cent less time," the Scotsman quoted him as saying.
"But this group improved more than the moderate intensity group.
"There was significantly reduced blood pressure in the high intensity group than the other groups. The blood profiles were better and body fat went down in this group, too," he added.