That time you spend on the treadmill could be doing more than trimming a few pounds and toning up your muscles. A new study indicates that regular exercise is good for parts of the body you can’t even see.

Telomeres [TELL-uh-meers] are small structures within your cells that help keep DNA in good condition as your cells divide. Researchers writing in the journal Circulation say the more you exercise, the less your telomeres deteriorate. That means your cells won’t wear out as fast.

The researchers studied more than a hundred adults. Some participated regularly in high-endurance athletic training, while others did not exercise much. Tests of the participants’ blood showed that the athletes’ white blood cells produced more protein and other materials that protect telomeres, and ultimately DNA, than the non-exercisers’ cells did.

The scientists acknowledged they can’t be sure if the physical activity itself, or the health benefits of long-term intense exercise, led to the change. But tests on mice agreed with the data from humans, showing that those who ran on wheels in their cages had more of these protective substances than the sedentary mice did.

Good telomere health can help slow the progression of age-related diseases, the researchers said.

The CDC says at least two-and-a-half hours of moderate aerobic activity each week is enough to reduce your chances of dying early. This means that even people with fit figures can benefit from regular workouts. And it proves that you’re never too young… or too old… to start exercising. So get moving!