Question: "Can I quit the gym this summer and still stay in shape by exercising outside?"
In fact, trading in your treadmill workouts for trail running, or even in-line skating, will likely give you a better workout, says Tina Vindum, founder of Outdoor Action Fitness, an outdoor-fitness instruction program in Marin County, California. "Outdoor workouts can burn more calories per minute and tone your muscles more completely than doing the same thing inside," she says. "Natural terrain also challenges and refines your balance in ways that a flat gym floor or machine never will."
Work It: The trick is to go for a balance of cardio and strength training. Each week, try one activity that incorporates upper-body strength (like tennis), one for lower-body strength (cycling) and one that works all your muscles (hiking with walking poles).