It may protect cells from aging

Mayo Clinic researchers studied the effects of HIIT on people over age 65. What they discovered may surprise you: Some age-related deterioration of muscle cells had actually been reversed.

HIIT seemed to change a cell's DNA in a way that boosted the muscle's ability to produce energy. It also triggered the growth of new muscle, helping counteract inevitable muscle loss that comes with aging.

These changes were more dramatic in the over-65 exercisers compared with a group of people under age 30 who did the same workouts. One possible takeaway: It's never too late to start and see big gains.