Although push-ups seem old-fashioned, they’re a surprisingly practical compound exercise that requires no extra equipment. Importantly, pushups don’t just tax the muscles in your arms and chest, they also require muscles throughout your body to stabilize your motion. And if you’re one of the many new exercisers who can’t complete a single push-up, there are two practical variations you can start with: wall push-ups and bent-knee push-ups (shown in the picture here).
Here’s how to do a classic push-up:
1. Lie chest-down on an exercise mat. Put your hands, palms down, on either side of your body at shoulder level. Keep your feet together, toes down.
2. Straighten your arms to push yourself up, breathing out. Keep your back straight,
your abdominal muscles tight, and your toes on the floor.
3. Pause, then lower yourself until your chest nearly touches the floor, breathing in. If you can, push yourself back up and continue with another repetition.
If a standard push-up is too hard (as it is for many), start with a bent-knee push-up. Before you begin, while you’re lying face-down, bend your legs into a right angle and lift your feet off the ground. (You can watch a demonstration at www.mayoclinic.com/health/modified-push-up/MM00735.) If that’s still too taxing, try a wall push-up. First, stand and face a wall. Then, lean against the wall and place your hands on either side at shoulder level. Finally, push against the wall. It’s essentially the same exercise, except now gravity is on your side.
Source of Information : Oreilly - Your Body Missing Manual