Time spent in the drudgery of strenuous exercise is a
well-documented turn-off for many people who want to get in better shape. In a
new study, researchers show that exercisers can burn as many as 200 extra
calories in as little as 2.5 minutes of concentrated effort a day—as long as
they intersperse longer periods of easy recovery in a practice known as sprint
interval training. The finding could make exercise more manageable for would-be
fitness buffs by cramming truly intense efforts into as little as 25 minutes.