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While any exercise is good exercise, scientists out of the University of Leicester in the U.K. say there’s one form of exercise that really seems to slow time’s tide: walking fast.

Using data from 400,000 British adults enrolled in the U.K. Biobank, the researchers determined those who walked briskly were determined to be 16 years younger in terms of “biological age” when they reach middle age.

At play here are parts of our DNA known as telomeres. They’re the end-caps chromosomes and the longer they are, the less you age.

And as it turns out, those who walked fast, had really long telomeres, the researchers said. In fact, they didn’t need to hit the gym or do anything else other than put one foot in front of the other, quickly.

It’s not known why telomeres’ length slows aging, but scientists know that when telomeres divide, they get shorter, and when they can’t divide anymore, they start dying. Dying cells have been linked to age-related diseases and aging in general.

“While the physical, mental, social and health benefits of walking are well-documented, this study is one of the first of its kind to compare genetic data with both self-reported walking speeds, as well as actual measurements of movement intensity from wearable activity tracking devices worn by participants,” the scientists said in a release.