Lace up those sneakers. Exercise — specifically high-intensity interval training — slows down the aging process.

Any kind of exercise is better than none, a study conducted by the Mayo Clinic noted. But it's the high-intensity interval training — HIIT, as it's commonly known in fitness circles — that best reverses age-related changes at the cellular level.

And although this works for people of all ages, it seems to offer more benefits to older people.

HIIT involves short bursts of intense aerobic activity, intermixed with longer stretches of moderate exercise. Participating in this kind of training encourages cells to make more proteins to fuel the energy-producing cellular mechanism. This, in turn, arrests the aging process.

The study, published in the journal Cell Metabolism, found that younger people participating in HIIT showed a 49 percent increase in mitochondrial capacity while an older group saw 69 percent. (Mitochondria are the cells' powerhouses, responsible for producing the molecule that transports chemical energy within cells.)

"Based on everything we know, there's no substitute for these exercise programs when it comes to delaying the aging process," said Dr. Sreekumaran Nair, senior author of the study and a Mayo diabetes researcher. "These things we are seeing cannot be done by any medicine."

The study, funded by the National Institutes of Health, used two sets of volunteers: The younger set ranged from 18 to 30 and the older volunteers were between 65 and 80. Those studied were then divided into three supervised exercise training programs that lasted three months.

The HIIT group did three days a week of cycling, with high-intensity bouts alternating with low-intensity pedaling, and two days a week of moderately difficult treadmill walking. A strength training group worked out with weights for lower- and upper-body muscles two days each week, while the third group cycled and lifted weights five days a week, but less strenuously than the two other groups.

Not surprisingly, the researchers found that strength training was most effective for building muscle mass and for improving strength — important because both qualities decline with age — but the group that participated in HIIT earned the best results at the cellular level. HIIT seemed to reverse the age-related decline in both mitochondrial function and muscle-building proteins.

So, how should you plan for your exercise week?

"If people have to pick one exercise," Nair said, "I would recommend high-intensity interval training, but I think it would be more beneficial if they could do three to four days of interval training and then a couple of days of strength training."