Want better exercise results in less time? Try interval training to boost your workout

Alternating between high- and low-intensity exercise may spur faster fitness gains.

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Spend less time exercising and burn more calories: sounds too good to be true, right? But it may just be possible with interval training, a type of workout that uses short bursts of strenuous activity to ramp up your heart rate and boost your fitness.

Long popular with high-performance athletes, interval training — a workout that alternates between high-intensity and low-intensity activity — isn't just reserved for those seeking gold medals. "If done properly, it can be safe for the vast majority of people," says Dr. Meagan Wasfy, an instructor in medicine at Harvard Medical School and a cardiologist at Massachusetts General Hospital.