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Cardio training is a lot like building muscle, since the heart is a muscle. To make the heart stronger, it has to be challenged. There is never a rest and recovery period for the heart, since it has to beat each and every minute of our lives.

The Myths of Easy Cardiovascular Fitness

For tens of millions of people, cardio training is a brisk walk around the block. A few minutes of walking, running, swimming, skiing, climbing, or maybe just rolling down the window to let the wind massage your face when you are driving your car is thought to strengthen the heart and make the cardiovascular system more resistant to high blood pressure, heart attack, and stroke. The truth is, however, real cardiovascular fitness just isn't that easy.

The idea of interval training is to work out hard for short periods while "coasting" or exert minimal effort in between. Interval training is often promoted as a way to lose more weight while working out less. Here is how it works.

Scientists at the Garvan Institute and the University of New South Wales in Australia recruited a group of overweight women to participate in a 15-week cardio fitness experiment. The women were asked to ride a stationary bike just 20 minutes per workout, three times per week. The interval training consisted of sprinting (pedaling as hard as they could) for 8 seconds, followed by 12 seconds of cycling lightly, repeating the intervals 60 times in 20 minutes. The scientists recruited a second group of women to do work out of stationary bikes for 40 minutes per session three times per week, doing twice as much exercise as the women in the experimental group.

At the end of 15 weeks, the women who had done interval training lost 3 times as much weight as the women who had put in twice as many hours on their stationary bikes. And the scientists also learned that making women work out harder did not help them lose more weight. Among overweight women, doing an 8-second sprint followed by 12 seconds of light cycling was more effective for weight loss than doing a 24-second sprint followed by 36 seconds of light cycling. The constant "shifting of gears" activates fat burning enzymes and keeps them going throughout the whole routine.

The Australian researchers believe the same principle could be applied to other forms of cardiovascular exercise, such as walking, running, and swimming. There is, however, an important "catch" in the findings.

While interval training was much more beneficial than steady-state cardiovascular exercise, the results were less than overwhelming. After the 15 weeks of working one hour a week, the women who did interval training had lost an average of 5.5 pounds (about 2.5 kilos). And even the "sprints" were not done at maximal speed. The overweight women exercised at only 60% of the maximum heart capacity, not the 75% to 80% usually recommended by trainers.

Still, if you are content to lose weight slowly, interval training for just an hour a week is an excellent way to go. You get much more weight loss than if you just pedaled the bike at an easy rate for twice as long, and the risk of injury is minimal. Don't do interval training on outdoor surfaces unless you are wearing non-skid shoes and walking or running on a non-skid surface, and don't do your exercise routine in extremes or heat or cold.

  • Trapp, E.G. & Boutcher, S.H. Fat loss following 15 weeks of high intensity, intermittent cycle ergometer training. University of New South Wales, Sydney, Australia.
  • Photo courtesy of cuegalos on Flickr: