Get off the pavement
Take advantage of the varied terrain nature has to offer. While most cardio machines will only let you go forward and up, outside you can also tackle downhills, test your lateral movement skills and more. "Try boulder bounding up dry riverbeds, then "slaloming" downhill through the trees," says Tina Vindum, founder of OutdoorFitness.com in Marin County, California. "I combined that with body-weight exercises using logs, boulders, tree limbs."
Look for props
Even if you don't have access to hiking trails or a body of water, it's usually easy to find a park or playground. Vindum suggests using benches for dips and push-ups. Think monkey bars are only for kids? They're also good for stretching and practicing pull-ups. Put your legs to work doing step-ups and calve raises on curbs.
If you do the same workout over and over, not only will your mind lose interest, your body will get bored and you'll plateau. Lucky for you, no two workouts are the same outdoors. Either the wind is different or the temperature has changed or you just pick a different route, so your body has to adapt. You have no excuse for doing the same workout in the same place two days in a row.
Using nature as your gym can save you money, but there's one piece of gear you shouldn't skimp on: shoes! Make sure they fit well and are made for outdoor terrain. You want grippy, lugged soles that bite into dirt and a wider outsole for more stability on rocks and other uneven surfaces; you may want added ankle support too. Sunscreen and water are must-haves year round. Also, check the weather report and plan your workout accordingly. In order to beat the heat, pollution, and damaging UV rays, exercise first thing in the morning.
You're more likely to get in a sweat session when it doesn't seem like a chore. Try to recapture that sense of fun you had when you were a kid playing on the jungle gym or frolicking outside. It doesn't have to be drudgery—make it up as you go.