Soccer

What kids can gain: Balance. Foot dexterity is a must to juggle the ball while finding teammates to pass to or a goal to shoot at. And the constant running is a big boon to their endurance levels and cardiovascular health.

What kids risk: Routine hazards include shin splints (pain in the front of and inside the lower legs), ankle twists, and the like. The bigger issue stems from heading the ball, which has been linked to concussions and possible brain injury. And it can happen whether the move is done correctly or not.

How to keep them safe: The American Academy of Pediatrics (AAP) now recommends no purposeful heading of the ball before age 10, says Teri McCambridge, M.D., chair of the AAP Council on Sports Medicine and Fitness. And some coaches encourage players to hold off until 13, says Karl Dewazien, coaching director for the California Youth Soccer Association North. Younger kids' brains are just more susceptible to injury. You also need to protect your child by limiting games. "We're in a time where coaches are bragging about playing their kids in 120 to 140 games a year," Dewazien says. "The pros don't even do that. You need 48 to 72 hours to rest between games, not 40 minutes."