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Interval training can boost exercise effects while reducing a workout’s length

Want to cut the length of your workout while maintaining or even increasing the benefits? Try interval training, a type of cardiovascular workout in which you alternate bursts of peppier exercise with slower-paced recovery periods. Intervals make you work more efficiently: Your overall intensity is greater, so the length of your workout can be cut by about 20 percent. Plus, a growing body of evidence suggests that this approach yields health benefits comparable or superior to traditional exercise, including:

Protecting the heart. Interval training has been linked to improved levels of HDL (good) cholesterol, says Cedric Bryant, chief science officer at the American Council on Exercise. A recent review in the journal Integrative Medicine Alert concluded that intervals are as effective as continuous moderate exercise, “if not more so, for increasing maximum exercise capacity, improving insulin resistance and blood pressure, reducing body fat, and raising HDL.” And a large 2006 epidemiological study in Norway linked a single weekly session of high-intensity exercise with a significantly lower risk of cardiovascular disease over a 16-year span.

Boosting metabolism. Our bodies use different energy sources — such as glycogen and ATP, a molecule that stores energy in your cells — during more intense movements. “Like a drag-racing car that uses all of its gasoline in seconds, these energy sources lead you to burn more calories while increasing your metabolism,” says Anthony Slater, a certified strength and conditioning specialist at Core Performance, a corporate wellness group in Norwell, Mass.

Increasing vigor. The older you get, the less time you spend running around, and that change is tied to the age-related decline in the quality of life. “If you can train at higher intensities, then easier movements, like simply walking and talking with friends, will become much easier,” Slater says.

Controlling diabetes. “Interval training has been found to significantly improve insulin sensitivity in diabetes patients, encouraging tissue in the body to take up sugar from the blood more rapidly in response to insulin,” Bryant says. In a small 2009 study in the journal Clinical Science, three months of twice-weekly interval training reduced fasting glucose levels in obese teenagers more than other exercise approaches. The increased benefit was still apparent nine months later.

Working in intervals

Start by replacing one or two of your regular aerobic workouts (such as cycling, swimming or walking) with interval sessions of the same activity, using the chart below as a guide. You should get short of breath and feel a burning sensation in your muscles during the “speed” phases, and they should be intense enough that you can speak only a couple of words immediately after them, Bryant says.

As you become accustomed to the program, you can add more high-intensity segments while shortening both the speed and recovery periods. Eventually, you might be able to gradually adjust the speed and recovery intervals until they’re equal. But experts suggest progressing slowly in the first month.

Note that high-intensity exercise of any type carries a risk of cardiac events and musculoskeletal injury. According to Bryant, research has found that some adults with cardiovascular disease can safely do interval training in a supervised setting. But see a physician first if you’ve been given a diagnosis of cardiovascular disease or are at an increased risk. You may need a doctor-
supervised exercise test before starting.

Copyright 2013. Consumers Union of United States Inc.

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