Khanthee Thao
Anatomy & Physiology
Dr. Maridy Troy
April 17, 2009
Volleyball Spike The deltoids or shoulders consist of three heads. The anterior heads are on the front of the arm. The medial heads are the sides of the arm, and the posterior heads are on the rear or back side of the arm. All three heads of the deltoids are attached to the humerus. Two of the muscles are attached to the humerus by the collar bone. They are the anterior deltoids and the medial deltoids. The posterior is attached to the humerus by the scapula (Marieb, 2006). Each head of the deltoids are responsible for different movements. The anterior deltoids move the arms out front, in a position called flexion. The medial deltoids move the arms out to the sides of the body which is known as lateral. And the posterior deltoids help move the arms to the dorsal side of the body. This is known as hyper-extension (Marieb, 2006).
These movements, such as hyperextension, flexion, and lateral are important to volleyball spikes. The flexion position moves the arm upwards to help assist the vertical jump. The medial helps assist the anterior deltoids. The muscle that helps the prime mover is known as synergist (Marieb, 2006, p.196). During this position the posterior deltoids are known as the antagonist, because it is the opposing muscle of the prime mover. The posterior deltoids is responsible for moving the arms downwards during the swing. During this downward swing of the spike the anterior deltoids are now the antagonist, since it is opposite of the prime mover. A sport that requires a lot of shoulder movement is volleyball. According to Lister (2005) the shoulder is susceptible to injuries because volleyball, like swimming, tennis, baseball and other sports that involve overhead arm movement, subjects the shoulder to repetitive abduction and external rotation followed by extension, and internal rotation, in addition, contact with the ball when spiking occurs at the point of maximal arm abduction, which may increase impingement forces. In conclusion the three deltoids are very important to the spiking technique in volleyball. Each head of the deltoid has its own responsibility, from raising the arm to lowering the arms. But it is also important to know that the shoulders are most susceptible to injuries, since it is used a lot.

Reference
Marieb E. (2006). Essentials of Human Anatomy & Physiology
Singh I. (2006). Anatomy and Physiology for Physiotherapists
Lister J. (2005, November 10). Volleyball Pr-rehabilitation to Prevent Injury. Retrieved April 19, 2009, from http://www.theacc.com/genrel/111005aac.html