- Hit the playground! "It's honestly better -- and far more fun -- than any gym," says Stefko. The monkey bars and mini-rock wall build upper-body muscle. Jumping off the climbing structures boosts bone density and leg strength. Heck, even the swings can be a good core workout. It's like an outside circuit course.
- Play a game. Kick-ball, tag, jumping rope, wheelbarrow races -- they're classics that absolutely count toward your child's daily activity requirement. For younger kids, try Move Like an Animal (it's a huge hit with the children Stefko works with). Call out the name of a critter and challenge your child to mimic the way it moves: hop like a frog, balance on one leg like a flamingo, stretch like a cat, and so on.
- Speed wash the car. Kill two birds with one sponge: Get that heart rate up and make the family car spotless. See how fast you can get it soaped, scrubbed, and hosed down—and try to best it next time.
- Check out a class. Take your child to an open gym at the local gymnastics center and let her try out the equipment, or head to the indoor climbing wall or skate park for a lesson. One-offs like this are good because they let your kid try out a bunch of different activities to see what she likes best -- without the time and money commitment of full-on, three-days-a-week lessons (which your child may end up hating).
- Use people power. Ditch the car and walk or bike when you can. Pedal to the pool, playground, or pizza shop, and trek the mile to school on foot.
- Inspire her. "Bring your kid to a sporting event -- a Major League Baseball game or a high school volleyball match -- so she can see and be motivated by the athletes," suggests Stefko. Before or after the game, kick around a ball together, shoot baskets, or play a little backyard volleyball.
Wobble hobble. Have your child place a water balloon between his knees and race to the finish line without dropping it. In just 15 minutes, he'll burn nearly 70 calories. Perfect for summer playdates. Benefits: cardio, coordination, balance, mood booster.
Backyard bowling. This is the sneaky-fitness version of “reduce, reuse, recycle.” Grab empty plastic bottles from the recycling bin and set them up like bowling pins. Take turns trying to knock them down with a soccer ball or kickball. Benefits: cardio, flexibility, balance, coordination
Garden party. Help your child choose some fruits and veggies to grow, plot out the garden, and tend the plants. (Hint: Opt for lower-maintenance items like tomatoes, zucchini, and carrots—kids have been known to forget a watering or two!) This idea is a better-health tri-fecta: Digging and planting is serious activity, it's something fun the whole fam can get involved in, and you get super-fresh, organic food out of the deal. Don't have room? Volunteer at a local community garden. Benefits: strength, cardio, flexibility, mood booster.