You've heard it before: Lifting weights and doing exercises like push-ups and planks will help you get (and stay) slim and build muscle. Turns out the same holds true for kids. In a recent study, teens who completed a three-month training program lost fat and got up to 50% stronger. Young people who pump iron have greater bone density and are less likely to suffer from injuries. What's more, these exercises are easy to do at home with your kids. All you need is a stability ball and 5- to 10-pound dumbbells. (As you and your workout partners get stronger, you may need heavier weights.) Three times a week, try this plan developed by Debi Pillarella, M.Ed., an American Council on Exercise (ACE) spokesperson who specializes in family fitness.
Lie facedown resting on forearms. Push up onto toes, keeping the body as straight as possible. Draw the belly button toward the spine, squeeze your glutes and abs and hold for 30 seconds. Rest one minute, then do the move again. (Repeat once.) As you get stronger, tack on more time in 15-second increments.