Although the push-up targets many muscles in the body, including the chest, back and abdominal muscles, the prime mover of the elbow joint during the exercise is the triceps brachii muscle on the back of your upper arm. The triceps extends the elbow joint, enabling you to press the weight of your body up against gravity.
To perform a push-up, begin in a plank position with your elbows straight. Your wrists should be about shoulder-width apart. Keeping your entire body from your ankles to your head in one straight line, bend your elbows to lower your body toward the floor. Your elbows may want to flare out slightly, but work to keep them close to your body. Lower until your chest touches the floor, then press with your arms to return to the starting position while maintaining a flat back.
As the name implies, the triceps brachii muscle has three heads. The long head, located on the inner upper arm, originates on the shoulder blade under the shoulder joint. The lateral head on the outer arm and the medial head on the inner arm both originate on the upper arm bone, or humerus. All three heads cross the back of the elbow to insert through a common tendon onto one of your forearm bones called the ulna. The function of the triceps is extend, or straighten, the elbow joint, although the long head also helps to extend the shoulder.
Keeping your elbows close to the sides of your body during a push-up targets the triceps muscles and may protect your shoulders. The close-grip variation of the push-up, in which your hands are positioned a little closer than shoulder-width, further emphasizes the involvement of the triceps. Lessen the push-up intensity by placing your hands on an elevated surface such as a bench or box. To increase the intensity, elevate your feet.
Before your push-up workout, warm up your body, including your arms and shoulders, with easy dynamic movements, such as arm swings. The American College of Sports Medicine recommends performing strength-training exercises, such as push-ups, two to three days per week. To build strength, aim for two to four sets of eight to 12 repetitions each, resting two to three minutes between sets. Allow at least 48 hours between workouts. To stretch your triceps while standing, reach your right arm overhead and bend your elbow, dropping your forearm behind your head. With your left hand, pull your right elbow toward your head. Repeat, switching arms.