1. 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.
2. 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.
3. 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.
4. 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).
5. 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.
6. 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.
7. 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.
8. 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.
9. 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.