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Oct. 12, 2012 -- Don’t have time to exercise? That excuse no longer works. Increasing evidence, including new research presented this week, shows that even short workouts that include surges of very high intensity can boost fitness and potentially shrink the waistline.

In the new study, exercise physiology graduate student Kyle Sevits of Colorado State University and his team demonstrated that a mere 2.5 minutes of giving it your all on an exercise bike can burn up to 220 calories.

That doesn’t mean that you can do an entire workout during a commercial break. Instead, those 2.5 minutes should be divided into five 30-second sprint intervals, each followed by a four-minute period of light, resistance-free pedaling. All told, that is less than 25 minutes, during which you will burn more calories than if you did 30 minutes of moderate cycling.

"You burn a lot of calories in a very short time," says Sevits. "Nearly all the calories are burned in those 2.5 minutes; you burn very few during the rest period."

He also points to additional benefits that come from interval training, including increased insulin sensitivity and glucose tolerance, both of which are important for overall good health.

“This kind of research could help motivate people to get fitter and burn more calories,” says Heather Gillespie, MD, a sports medicine specialist at UCLA Medical Center in Santa Monica. She was not involved in the research. “It’s a very small study, but it’s very promising and adds more evidence to the benefits of interval training.”

Sprinting in the Lab

For the study, Sevits and his colleagues recruited 10 healthy men with the average age of 25. For three days, the recruits prepared for the study by eating a strict diet based on their caloric needs so that the researchers could be sure they were neither overfed nor underfed. Then they were checked into the lab.

The rooms where they spent the next two days were outfitted with equipment that allowed the researchers to measure the number of calories each recruit burned during their stay. They stuck to the same diet while they sat in front of the computer or watched movies. On one of the days, though, they had to exercise.

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