The key to bodyweight exercise is mixing it up. Challenge yourself. If you're not sore the next day, you didn't work out hard enough. "When you push yourself, you'll be building muscle, increasing bone density, strengthening ligaments, and burning calories for up to 36 hours after your workout," says Mark Lauren, author of 'You Are Your Own Gym.' When push-ups become too easy, switch to a different grip – wide, narrow, or staggered hands – or pause during the motion. Try one set on an incline, the next on a decline, and the next with one hand on a basketball. For all of the exercises below, aim for three sets of 10 reps unless noted otherwise. Time yourself and try to do them more quickly the next time around. If you can't finish a set, complete it with the easier version.
The No-Weights Workout: Squats
When squatting, keep your hands behind your head and squat as deeply as you comfortably can. Contract your abs before you descend, keep your back straight, and squat deeply, as if sitting in a chair.
Make it Hard
When you reach the bottom of the squat, jump as high as you can. This makes the move explosive, adding power and honing your nervous system to improve muscle response.
Credit: Photograph by John Loomis
With your feet shoulder-width apart, kick your right foot off the ground behind you and hold it. Drop into a squat. To make it more difficult, do a one-leg squat with your leg out in front of you, keeping it raised while lowering your body until your butt is about two inches off the floor.