Nope, it's not a time machine you need if you want to be a decade younger. It's a treadmill. Or a bike. Or just a good pair of sneakers.

That's right. The most physically active folks in a recent study showed signs of being as much as 10 years younger on a cellular level.

Go Long on Protection
How does exercise do that? By keeping your telomeres long and healthy. What on earth are those, you ask? Simple. They're like the plastic tips on shoelaces. But in your body, they cap the ends of the DNA strands (chromosomes) in all your cells. Over time, your telomeres can shorten to the point where cells stop regenerating, and even die (think accelerated aging). Shortened telomeres also leave your chromosomes vulnerable to the kind of damage that may trigger diseases such as cancer. (Here's a whole slew of ways to keep your telomeres from getting shorter.)

Running from Old Age
The fact that exercise keeps your cells renewing themselves and protects your DNA is good motivation to get out there. But if you need another push:

• Get comfy. Watch this video to find out how you can measure your arch for the perfect exercise-shoe fit.
• Consider a quickie workout. It's good for you, too!
• Take breaks. Here's why taking a break during your workout is actually best.
• Get more out of less by following these 10 easy guidelines on form.

Find out why it's more important to exercise than to be thin.