Arm Motion

Written By Sherry Werner

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Arm Motion

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For the last few months I have talked about footwork and the legs, hips and trunk in pitching. You probably have gotten the message that I feel that it is important to use the whole body in pitching to assist the arm in delivering the ball. In order to ensure efficient usage of the leg and trunk contributions, proper arm motion is also important. The arm has to be in synch with the rest of the body and be in the correct position relative to the body throughout the pitch to maximize force transfer.

As the ball is taken out of the glove, the arm begins its “windmill.” Once the top of the motion is reached, the arm should be fairly straight to increase leverage. The longer the lever, the less muscle force is necessary to impart the same velocity to the ball. A straight arm also stretches the muscles of the arm and shoulder, which leads to greater force production.

Also at the top of the motion, the arm needs to rotate at the shoulder joint so that the hand and ball face third base (for a right-handed pitcher). This rotation allows the arm to continue through the rest of the “windmill.” If the arm does not turn outward, the geometry of the bones and muscles of the shoulder joint will not permit a smooth path of the throwing arm.

For the pitchers I have studied, the path of the ball is not circular, but more oval-shaped. This path occurs in a plane very close to the body. As the arm passes the ear at the top of the motion and again as it passes the hip near release, it should be in close proximity to the body. When the ball is moved through a plane near the body it is easier to control the release point. Control problems occur when the arm moves out of the plane and away from the body. This happens most often when a pitcher’s windup causes the shoulders to open ahead of the hips. A right-handed pitcher who brings the glove and ball to the right hip will tend to have this problem. It is important for the shoulders to stay square (closed) to the target as the pitch is initiated. If the arm stays in a plane close to the body and does not have to adjust back into that plane for release, the pitch has a “built-in” control mechanism.

As the arm nears the release point, the elbow begins to bend (flex) and the wrist should be cocked (extended) in preparation for a rapid wrist snap (flexion) at release. In Biomechanics, proximal to distal sequencing is a term used to describe an efficient pattern of movement where the most proximal (closest to the center of the body) joint reaches maximum speed ahead of the next most proximal joint, down the chain until the most distal (farthest from the center of the body) joint reaches its maximum speed. This sequence is smooth and the force transfer is very efficient. In pitching, the shoulder (proximal) joint begins to flex once it reaches the top of the motion. Next, the elbow begins to bend (flex) and finally wrist snap occurs as the ball is released.

Wrist and elbow flexion should continue through release and the follow through. Although the ball is headed toward the catcher’s mitt as the follow through occurs, this is a critical phase of pitching. The energy and forces produced throughout the pitch remain in the throwing arm after ball release. This energy must be dissipated by the arm and body during the follow through. Continuing to bend the elbow and wrist after ball release shortens the arm lever and acts to decrease shoulder stress.

During the delivery phase of pitching, the anterior (front) shoulder muscles contract to propel the ball. Once ball release occurs, however, the posterior (back) shoulder muscles come into play to slow down and stop the arm’s motion. Strengthening of the pitching arm is important, but the posterior muscles are often overlooked. Strong posterior shoulder muscles can minimize shoulder flexion after ball release, which in turn decreases shoulder stress.

In past issues I have stressed the importance of strengthening the musculature of the feet, legs, hips and trunk. Because of the loads placed on the elbow and shoulder joints in pitching, it is equally imperative to strengthen the arm and shoulder girdle. In the studies that have been carried out on windmill pitching so far, the magnitude of force pulling on the shoulder joint at release has been, on average, 100 percent body weight. Reducing this stress with proper pitching mechanics and increasing the joint’s ability to absorb these loads through strength training are our only avenues to reduce the chance of chronic overuse injuries in pitching.

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Sherry Werner: PhD is currently a biomechanics consultant with TMI Sports Medicine, and Tulane Institute of Sports Medicine, and a pitching instructor at the Sherry Werner Fastpitch Academy. She has held research positions at the United States Olympic Training Center. She received a MS degree in Biomechanics from Indiana University, and a PhD in Biomechanics from The Pennsylvania State University.
Dr. Werner's research has focused on the effects of throwing motions at the shoulder, elbow and wrist. Past projects include data collection and analysis of elite softball pitchers during the 1996 Olympic Games. Sherry also released an instructional pitching DVD with Jennie Finch in 2011.

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