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Interval Exercise Boosts Fitness

Don't Sweat It

Heart and Mind Benefit

"The most important phase of exercise for heart health," Westcott explains, "is immediately after the bout of exercise -- the recovery period. In interval training, you get multiple recovery periods [as you switch to low-intensity bouts] and thus an enhanced heart response."


Another important advantage of interval training is that it can help combat boredom. "Go into the standard gym," Westcott says: "Everyone is walking on treadmills or riding exercise bikes. Although these are expensive machines with readouts of every kind, usually the dials are covered by a towel or newspaper. The exercisers don't want to know how much longer they have or how much farther they need to go. They are bored."


Contrast this, he says, with getting on the bike and setting it for the first 5 warmup minutes at 50 watts, then jumping to 4 minutes at 125 watts. "That's 4, not 30," he emphasizes. "It's hard but you can do it."


For the next 4 minutes, dial down to 75 watts. "Suddenly, this seems easy, almost fun," Westcott exclaims. "You start enjoying it, instead of waiting for it to be over." Then back to 125 watts! "You should do three sets of the 125, 75, then a cool-down of 50 watts."

Boost Your Immune System

How do you decide your maximum? "Most people exercise at 70% of their maximum heart rate," Westcott says. "You can use the talk test: At maximum, all-out effort, you should not be able to talk except to say yes or no. At mid-effort, you could probably utter a sentence or two. And at low, effort, you should be able to hold a conversation."


To interval train for 30 minutes on the treadmill, Westcott says, don't walk 3 1/2 miles per hour for 30 minutes but instead try doing five intervals of 6 minutes each. Begin with 6 minutes at 3 miles per hour, then 6 minutes at 4, then another 6 minutes at 3, then 6 at 4, and finally a cool-down of 6 minutes at 3.

This gives you the same workout--30 minutes at an average of 3 1/2 miles per hour--but with more work effort than your body would normally produce.


As an added benefit, you may even boost your immune system. Researchers at Texas Christian University in Fort Worth recently did a small study on 10 volunteers. Exercisers had significantly higher counts of immune cells, and that immunity was highest after the second round of bike riding.


Jean Lawrence is a medical journalist based in Chandler, Ariz.


Beth Israel Deaconess Medical Center. Reviewed for medical accuracy by physicians at Beth Israel Deaconess Medical Center (BIDMC), Harvard Medical School. BIDMC does not endorse any products or services advertised on this Web site.


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