Taking a well-deserved breather in the middle of your workout could help you burn more body fat than exercising continuously, according to the results of a study published in the June edition of the Journal of Applied Physiology. Researchers at the University of Tokyo found that when individuals took a 20-minute rest between two half-hour bouts of exercise, they burned more fat than when they exercised non-stop for 60 minutes.

Blood tests performed on the exercising volunteers revealed that taking a break during physical activity resulted in higher levels of fatty acids and glycerol, chemical compounds that are released when body fat is used for energy. Even in the "recovery" period following exercise, fat breakdown was greater when the subjects took a mid-workout breather than when they exercised continuously.

You might welcome the addition of a 20-minute break to your workout routine — if your schedule allows it. If time is tight and your goal is to exercise as quickly and as effectively as possible, you may need to adopt a different strategy.

Researchers at the University of New South Wales recently reported that short bouts of vigorous, "sprint"-type exercise resulted in significant improvements in muscle strength and endurance capacity. Bursts of high-intensity exercise were found to produce changes similar to training methods involving long hours of exercise each week.

For the study, the researchers asked 45 overweight women to participate in cycling exercises three times a week over a 15-week period. One group of women participated in a 20-minute cycling session during which they alternately sprinted for 8 seconds and pedaled lightly for 12 seconds.

The other group of women simply cycled on the stationary bikes at a continuous, regular pace for 40 minutes. At the end of the study, the women who had performed short bouts of sprinting had lost three times more weight than those who had engaged in slow, steady cycling.

The researchers attributed the impressive weight loss results of this type of "interval training" to the effects of the hormones adrenaline and noradrenaline. Both are released in substantial quantities during vigorous exercise, and both promote the accelerated breakdown of fat in the body.

The findings of the recent study weren't entirely unexpected. In a similar study published in the Journal of Physiology in 2006, researchers at McMaster University in Canada compared the effects of interval training to those of continuous exercise.

For the study, 16 healthy college students were asked to participate in six training sessions during a two-week period. Eight of the subjects were assigned to an "endurance" group, while the other eight were assigned to a "sprint" group.

In each of the six training sessions, subjects in the endurance group were asked to engage in continuous, moderate-intensity cycling for 90 to 120 minutes. Subjects in the sprint group were asked to perform between four and six 30-second bursts of "all-out" cycling, with each maximum-intensity effort followed by a four-minute recovery period.

At the end of the two week study period, the subjects in the endurance group had spent a little more than 10 hours working out, while those in the sprint group had spent just over two hours exercising. Despite the eight-hour difference in total training time, the two groups showed similar improvements in performance and endurance.

Although this study was designed specifically to evaluate the effects of adding vigorous bouts of exercise to a cycling workout, the fat-burning phenomenon associated with sprinting occurs in other types of physical activity. Whether you're walking, swimming, or dancing, you can increase the effectiveness of your workout by adding regular bursts of high-intensity effort.

As you become stronger and more physically fit, you'll be able to step up the intensity of your exercise. The better shape you're in, the less time you need to spend exercising to get the same results.

For extremely fit athletes, for example, just six minutes of very vigorous exercise can be as beneficial as an hour of leisurely activity.

If you're just starting a fitness program, you'll need to spend a little more time exercising, preferably at least 30 minutes to an hour a day. The good news is that now you don't have to feel guilty about stopping to rest.

Taking a mid-workout breather can do more than just make exercise more enjoyable: it could boost your body's ability to burn fat.

Rallie McAllister, M.D., M.P.H., is a family physician in Kingsport, Tenn., and author of "Healthy Lunchbox: The Working Mom's Guide to Keeping You and Your Kids Trim." Her Web site is http://www.rallieonhealth.com. To find out more about Rallie McAllister, M.D., and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate Web page at www.creators.com.

COPYRIGHT 2007 CREATORS SYNDICATE, INC.

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