But researchers say that parents can make a difference, even at this difficult age. It's vital, they say, that parents help their children find an activity they like -- and help them keep up with it.
"The key here is letting the child choose," says Jim Sallis, PhD, a physical educator also at San Diego State. "If the kid wants to take a karate or aerobics class, it's the parents' job to help them find the class, or drive them there, or do whatever it takes to make that happen." In fact, kids whose parents transport them back and forth are the most likely to stick with their sports.
When teenagers start high school, they run up against a more adult impediment to exercise: a lack of time. When after-school activities, jobs, and socializing all become increasingly important, a fitness routine can easily fall by the wayside. At this stage, it's crucial for parents to help adolescents find activities they can fit into their schedules -- and encourage them to carve out the time to do them. Non-competitive activities -- salsa dancing or kayaking, perhaps -- are likely to be attractive because they can be enjoyed with peers of all fitness levels.
Of course, the onus to address this problem isn't entirely on parents. The Centers for Disease Control and Prevention (CDC) is trying to get kids of all ages walking to school again, since only one out of every ten children does so these days. In May, the CDC will publish a community-based walk-to-school program guide that includes tools for assessing the condition of sidewalks and tips on how to keep kids safe. ("If a stranger offers you a ride, say 'NO!' ") Some high schools are introducing health clubs -- complete with hair dryers -- to try to entice teens to work out. And fitness educators are setting up junior high and high school programs designed to teach teens about the importance of creating a personal fitness regimen.
So far, research suggests that kids involved in some of these programs are less likely to be sedentary than kids who take traditional PE. "Opportunity is the critical element here," says Chuck Corbin, PhD, a physical activity educator at Arizona State University in Phoenix. "If you give kids an opportunity to be active and help them find something that clicks, then they stand a much better chance of making exercise a lifelong habit."