A pushup is a classic muscle-building move that tones the arms, the chest, the front of the shoulders and the triceps. According to "The New York Times," a 40-year-old man should be able to perform 27 pushups and a woman should be able to perform 16. If you can't achieve this number right off the bat, work your way up. Whether performed on the toes or as a modified pushup on the knees, practicing proper form is vital to protecting your back and neck from strain. Once you know the proper form, you can perform this weight-bearing exercise almost anywhere.
Get in a kneeling position, then bend forward and place your hands on the floor, slightly wider than shoulder-width apart. While your wrists don't have to be directly under your shoulders, they should be aligned with the shoulders, neither in front of them nor in back of them. Keep the fingers loosely (not locked) together and point them straight forward. Your arms should be straight, but not locked at the elbows.
Step your legs back, one at a time (for a full pushup). Your feet should be closer than shoulder-width apart, but not locked together at the ankles, and your body should make a straight line. Look at yourself in a mirror to ensure that your bottom is not in the air, your back is not curved and your shoulders are not sloping in.
Perform a modified pushup, by crossing your feet at the ankles and keeping your body in a straight line -- much like the posture in Step 2. Keep your head as part of this straight line. Don't let it dip below your shoulders.
Inhale while you lower yourself to the floor. Your goal should be to almost, but not quite, touch your chest -- not your head -- to the ground. As a general rule, stop the motion when your elbows reach a 90-degree angle.
Exhale as you push back upward. Maintain the same straight-line form and don't lock your elbows as you reach the top of your pushup.
Before repeating, check your form to make sure you haven't shifted after the effort of the first pushup.