Harnessing the power of high-intensity interval training

Adding short bursts of ramped-up exercise to your workout may be good for your waistline as well as your heart health.

For decades, competitive athletes have added brief bouts of strenuous exercise to their workouts to boost their performance. Known as interval training, this practice is now moving into the mainstream, bolstered by emerging evidence of its health benefits for all sorts of people, including those with heart disease.

"There's a growing consensus that interval training helps people lose weight and may have cardiovascular benefits," says cardiologist Dr. Stephen Wiviott, associate professor of medicine at Harvard Medical School. Also known as high-intensity interval training (HIIT), these workouts alternate between periods of high-intensity and lower-intensity activity. You can do intervals during any type of exercise — walking, running, cycling, swimming, or even while doing calisthenics, such as jumping jacks, push-ups, or squats. A longtime distance runner, Dr. Wiviott started doing HIIT workouts at his local CrossFit gym about a year ago. "Even though I was exercising for shorter periods of time, I lost body fat and felt better," he says. His positive experience spurred him to explore the evidence supporting HIIT.