Boosting your heart rate keeps your heart in top form and burns serious calories—no gym membership required. Here are 18 simple, surprising tips to help you get your heart pumping this summer.

1. Move your workout into the water. The next time you’re at the beach or poolside, take a break from lounge-chair languishing and try a shallow-water workout instead. Walking through thigh-deep water burns nearly twice as many calories as walking on land.
Total burn: More than 210 calories per half-hour

2. Hold the ’07 Olympic trials in your backyard. The real Games may be a year off, but you can make your mark in the garden-rock shot put or sandbox long jump. Choose your favorite summer Olympic sport and tweak it to make it backyard-friendly. Then gather all the friends and family you can and go for the gold.
Total burn: 170 calories per half-hour

3. Adopt a stretch of park or beach and keep it clean. Picking up trash can help both your community and your heart. Start by recruiting buddies, then crank up some fast-paced tunes on your boom box or MP3 player and get to work. All that squatting and lunging will leave you—and the land—looking beautiful.
Total burn: 102 calories per half-hour

4. Take a bike tour of a nearby city. Explore new neighborhoods, or grab a friend and a map to create your own sightseeing trip. Your heart will be racing in no time.
Total burn: Around 270 calories per half-hour at a moderate pace

5. Pick your own berries. Get a full-body workout while you gather fresh fruit. Walk the fields at a nearby farm, pick to your heart’s content, then carry the berry-filled baskets back to your car. To find a local farm, visit pickyourown.org.
Total burn: 102 calories per half-hour

6. “Test out” playground equipment. 170 calories per half-hour

7. Crank up the iPod and get your groove on. 153 calories per half-hour

8. Go canoeing. 119 calories per half-hour

9. Scale the longest staircase in town. 272 calories per half-hour

10. Get spinning with a hula hoop. 153 calories per half-hour

11. Jog on the beach. 238 calories per half-hour

12. Twirl a jump rope. 340 calories per half-hour

13. Play a game of tennis—with no out-of-bounds. 238 calories per half-hour

14. Volunteer to walk dogs at a local shelter. 102 calories per half-hour

15. Take a self-defense class. 340 calories per half-hour

16. Listen to books on tape while walking the chapters away. 129 calories per half-hour

17. Cultivate a garden of your family’s favorite veggies. 136 calories per half-hour

18. Pack a picnic and hike to the perfect spot. 238 calories per half-hour

Note: All calorie estimates are based on a 150-pound woman.

By Bethany Lye