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Interval Exercise Boosts Fitness

Don't Sweat It

WebMD Feature

Feb. 25, 2002 -- If the image of a bobbing, straining you, pounding on the treadmill for a gasping half-hour at a whack, is interfering with your New Year's resolution to dispose of that extra holiday weight, don't despair. It turns out that exercising in short spurts may do you just as much good as sweating over the long haul.


A study from the University of Wisconsin-Oshkosh, in the October 2001 issue of the Journal of the American College of Nutrition, showed that three 10-minute bouts of exercise, and two 15-minute bouts, and one 30-minute bout were each just about equally effective in increasing aerobic capacity and reducing body fat.


W. Daniel Schmidt, PhD, chairman of the department of physical education and health promotion at the university and lead investigator of the study, which involved overweight female college students, says the study shows that exercise divided into several short periods had positive effects on both heart fitness and weight loss and was comparable to exercising in fewer, longer sessions. (The nonexercising control groups, incidentally, increased both body weight and body fat content over the 12 weeks studied.)


One catch: The students also followed a restricted-calorie diet. Schmidt says he is not sure that exercising in spurts is ideal for the treatment of obesity, since a diet must also be followed. But research done recently at Laval University in Quebec shows that this type of exercise -- the technique is called interval training -- can indeed rev up metabolism quicker than regular, constant aerobic exercise.

How It Works

When exercising, your body uses one of two systems to produce energy --the aerobic system and the anaerobic system.


The aerobic system uses oxygen to convert carbohydrates in your body to energy, and it can fuel long, sustained exertion. The anaerobic system, by contrast, grabs energy stored in your muscles in the form of glycogen to fuel short bursts of activity like sprinting or lifting heavy objects. This system doesn't draw on oxygen and only provides energy for brief activities. It also pours out lactic acid as a byproduct and causes that achy, used-up feeling.


According to the American Council of Exercise (, interval training may allow you to enjoy the benefits of anaerobic exercise without the burning muscles. It involves alternating high-intensity and lower-intensity exercise within a single workout. The Swedes have given it the name fartlek, which means, "speed play."


In the Laval University study, for example, participants alternated between 3 minutes of moderate-intensity step aerobics and 1 minute of high-intensity stepping, repeating the cycle eight to ten times.


According to Wayne L. Westcott, PhD, fitness research director at the South Shore YMCA in Quincy, Massachusetts, interval training is "absolutely the best" for both beginners and high-end athletes. "High-end athletes all train that way," he says. "It's not necessarily the easiest, but it is the best."

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