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Work out fast and furious
How often, as you're plodding along on the treadmill, do you see a guy enter the gym, blast through a gonzo circuit and leave while you're still at it? And how often do you return from an endless power walk to hear your man grunting to the latest extreme dude workout—CrossFit, Insanity, P90X?
The male sex is wise to a fitness tactic that science recently confirmed: Short bursts of vigorous exercise—known as high-intensity interval training, or HIIT—dramatically boost the body's calorie-torching abilities. "HIIT workouts change you on a genetic level," says Pamela Peeke, MD, author of Body for Life for Women. "You're challenging your muscles and your metabolism and pushing the volume of oxygen in the lungs, driving up calorie burn."
Make It Yours
Many go-to guy workouts incorporate principles of HIIT, but if those seem too aggressive, don't worry. "Kickboxing, hip-hop, even spin count—there are all kinds of high-intensity classes now," Dr. Peeke says. And they may not take much of a time commitment. A 2012 study at Colorado State University found that people who worked out on a stationary bike for less than 25 minutes, with just a few sprints mixed in, torched an additional 200 calories a day, due to an afterburn effect. If you haven't worked out in ages, though, ease into high-intensity workouts.