Pushups are definitely a test of your strength and endurance. They're also an exercise that requires no equipment and can be done virtually anywhere, by anyone, at any fitness level. From the beginner who starts out with wall pushups to the advanced athlete who favors the plyo pushup; you'll all benefit from incorporating the pushup into your strength training routine.
The primary muscles that are activated when you perform a pushup are the pectorals, the anterior and medial deltoids and the triceps brachii. The pectorals are the large chest muscles. The anterior and medial deltoids are located on the front and sides of the shoulders. Finally, the triceps brachii is the horse-shoe-shaped muscle located on the back of the arm.
Stabilizing muscles support the body while you perform an exercise. The stabilizing muscles that are targeted when you perform a pushup are the rectus abdominus, obliques and quads. Synergist muscles help another muscle perform an exercise; and during a pushup your synergists are the pectoralis major, the anterior deltoids and the triceps brachii.
To perform a standard pushup, place your palms on the ground, shoulder-width apart, fingers pointing forward. While keeping your body rigid -- being careful not to allow your hips or knees to raise up or drop down during any point in the exercise -- lower your torso to the ground, allowing your elbows to spread out. To raise up, press upward through your arms until your elbows are fully extended.
Pushup for Arms
To specifically target the arms (triceps brachii), you can perform a variation on the standard version of the pushup by placing your hands closer together on the ground rather than shoulder-width apart. The change in hand placement takes the emphasis off the chest muscles and places more emphasis on the triceps. When lowering to the ground, keep your elbows close to your sides. Your elbows should flare back instead of out to the side like they do in the standard pushup.
Whether you're a beginner to exercise or more advanced, there's a pushup for every level of fitness. Pushups that are suitable for a beginner include the modified T pushup, the modified halfway pushup, which is performed on your knees and wall pushups which are performed standing with your hands against a wall. For the intermediate, recommended pushups include the full T pushup, the dive-bomber pushup and the staggered-arm pushup. Advanced pushups include the T push-up with leg raise, the pushup with leg lift and the plyo pushup. Check out the American Council on Exercise's exercise library or ExRx.net for instructions on how to perform most pushups.