© 2009 health magazinePhotos: Ericka McConnell

Jazz up your walk There’s nothing better than a summer walk—except a summer walk that lets you enjoy the great out-doors and hike your calorie burn. The secret: Add intervals (short bursts of high-intensity exercise). Celeb trainer Gunnar Peterson, who has worked with Jennifer Lopez and Penélope Cruz and is the author of G-Force: The Ultimate Guide to Your Best Body Ever, suggests this jazzed-up combo, which can burn as many as 300 calories in 40 minutes at high intensity.

• Walk 10 minutes• DO these intervals in quick succession: 10 squats, 10 push-ups, 20 crunches, 10 leg lifts• Walk 5 minutes• repeat intervals• Walk 3 minutes• repeat intervals• Walk 2 minutes• repeat intervals• Walk 10 minutes