Remember the Fountain of Youth? Sixteenth-century Spanish conquistador Ponce de Leon searched relentlessly for it, when it might have resided within him all along—in the form of sweat. "Exercise can absolutely tighten your muscles and give you the appearance of being younger," says Kansas City-based personal trainer Serena Merrill, a senior exercise consultant for the American Council on Exercise. "And if the moves you do are functional—meaning, they mimic actions you perform in your everyday life—they can actually help you to move more easily and function younger, too."
Even better: You don't even need to produce a fountain of sweat. Just a trickle will do. Eat your heart out, Ponce.