Five hundred years ago, Ponce de Leon landed in Florida, searching for the Fountain of Youth. (Spoiler alert: Scholars say that's a myth; the tale was invented by rivals to make the explorer look foolish, and by the 17th century the myth became accepted fact.) However, hundreds of water sources (including a magnesium-and-radium-rich fountain in Punta Gorda, Fla., and "liquid Viagra" that bubbles up in Fiuggi, Italy) are said to deliver perpetual youthfulness.

But we know the real Fountain of Youth is inside YOU: It's the sweat that comes from physical activity.

A new eight-year study looked at 3,500 folks around age 65: Those who'd always gotten moderate or vigorous exercise were seven times more likely to have healthy aging; even those who didn't exercise until they were already old tripled their chances of a healthy old age.

When you're sweatin' and smilin', dementia and depression, as well as heart disease, cancer and Type 2 diabetes, just happen less often.

The two keys to keeping active - or to getting movin' - as you age: Having a group or partner to do it with, and finding an activity you enjoy. So sign up for a group class at the gym or get a workout buddy or online coach to support you. And experiment with walking, jogging, cycling, swimming, yoga and strength-building or flexibility exercises to see what sustains your interest. Then sweat it out for at least 30 minutes daily!

P.S. You cut the risk of stroke 20 percent by sweating four times a week.

© 2013 Michael Roizen, M.D. and Mehmet Oz, M.D.
Distributed by King Features Syndicate, Inc.