Scientists find that exercising intensely for as little as 2.5 minutes a day can burn around 200 calories.

Researchers from Colorado State University and the University of Colorado Anschultz Medical Campus compared the number of calories burned in a group of male participants on two different days: one spent watching television and the other doing high-intensity exercise followed by long periods of recovery.

High-intensity exercise is where maximum physical effort is put into work the body as hard as possible, according to researchers testing the theory that a quick burst of sprinting is more productive than jogging or walking for a longer period of time.

The study involved five healthy male volunteers between the ages of 25 and 31. Lead researcher Kyle Sevits and his colleagues asked participants to eat a diet calculated to give their bodies exactly the right amount of calories so that they weren't over or under eating for three days.

Afterwards, participants were asked to spend one day being sedentary, watching TV or using the computer, and another day exercising. On the day of exercise, participants pedaled as fast as possible on an exercise bike set at high resistance for five, 30 seconds sets. Each of the five sets was separated by four-minute periods of recovery in which participants pedaled slowly with very little resistance.

Sevits and his team had coached the volunteers over an intercom system during the intense, 30-second, sprints and encouraged them to give 100 percent effort.

Researchers found that on the interval workout day, the men burned an average of an extra 200 calories despite devoting only a total of 2.5 minutes exercising.

"Research shows that many people start an exercise program but just can't keep it up," Sevits said in a statement. "The biggest factor people quote is that they don't have the time to fit in exercise. We hope if exercise can be fit into a smaller period of time, then they may give exercise a go and stick with it."

"Burning an extra 200 calories from these exercises a couple of times a week can help keep away that pound or two that many of us gain each year," he added.

The latest research will be presented at The Integrative Biology of Exercise VI meeting being held October 10 to 13 at the Westin Westminster Hotel in Westminster, CO.

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