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How It Works continued...


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."

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."

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