Serious athletes have long known about the benefits of high-intensity interval training—alternating periods of short, intense anaerobic exercise with less intense recovery periods—and they’ve been reaping the rewards, too.

The idea is simple: less total time required to make a big change—more bang for your buck, says Brent C. Ruby, Ph.D., the director of the Montana Center for Work Physiology and Exercise Metabolism at the University of Montana. But the perks go far beyond saving time and expediting results—and years of research prove it. So if you're not already on board with HIIT, read on to get seriously motivated to start.