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THE PITCHER’S SHOULDER
A CASE STUDY

Submitted by
Robert W. Wainwright, P.T., Director
Kinematic Consultants, Inc.
645 Ocean Road
Point Pleasant, New Jersey 08742
908 714-1907 FAX 908 714 1913

History: The subject of this study is a 22 year old rookie pitcher for a major league baseballteam. During his rookie season, he developed anterior shoulder pain. The pain progressed over a period of time. He was treated with ice and modalities by the team trainer. Eventually the pain disabled him from active pitching. The team physician diagnosed the problem as possible rotator cuff tear. He was treated conservatively with physical therapy modalities and exercise. The treatment modality of choice was an Ariel CES, Arm Leg Unit. The emphasis was on [Figure 1] The Calibration Cube many pitches as he is strengthening the small rotator cuff muscles. At the end of an eight week rehabilitation program, the subject was allowed to resume pitching on a graduated basis. When the subject was able to pitch at approximately 70% of full speed, a kinematic analysis was performed, utilizing the Ariel Performance Analysis System.

Goal of the Study: To determine if the subject’s pitching style was dynamically contributory to excessive shoulder stress.

The Study: The subject was position in front of an indoor pitching range. Two camera’s were utilized to film the subject at 60 Hz. The camera angles were approximately 45 degrees and 135 degrees from the throwing direction. The field was calibrated with a 6’x 5’ x 3’ calibration cube with known x,y,z coordinates for 16 positions. [see Figure 1]

[Figure 1] The Calibration Cube

The subject was asked to warm up with as needed. The trials were noted and the subject was asked to give feedback as to which pitches were good, in his opinion. The "good" pitches were logged and noted for analysis. [see Figure 2]

[Figure 2] The Subject

Upon completion of the data collection phase, the video footage was transferred to the computer hard disk and was digitized, transformed, smoothed and analyzed, utilizing the APAS system, in accordance with accepted scientific methodology. The resulting subject file is represented as a 3 dimensional stick figure that can be computer animated at one frame intervals or as continuous event.

[Figure 3] Kinematic Stick Figure of the "Pitch"

Analysis: A biomechanical analysis was performed on the subject’s pitching style. As noted, he was not pitching at full speed, due to injury recovery, therefore this analysis addresses the relative joint positions and forces, in relation to his right shoulder, as opposed to speed and accuracy.

Graph #1 addresses the relative speeds of his right side joints, prior to and at ball release. Efficient ballistic sport events will follow a sequential delivery and forward passage of peak joint linear velocities from the ground up through the wrist and hand.

It is noted that this pitcher peaks his linear hip, shoulder, elbow and wrist velocities in proper sequence but there is a significant drop in peak velocities, approximately .4 seconds before ball release, at the elbow and wrist joints.

Graph II addresses the issue of total body momentum at ball release, linear and rotational. Each measure of momentum should reach its peak at ball release for maximum efficiency.

It is noted that the subject’s linear reaches peak approximately .3 seconds prior to ball release and his rotational momentum reaches peak at ball release. This indicates a pre-release linear braking motion of the body. This action will place higher stress on the anterior of the shoulder joint as it positions itself for energy transfer to the elbow, wrist and hand.

Graph III addresses the relative position of shoulders vs. hips.

It is noted that at ball release the subject’s shoulders are only 17 degrees forward of his hips at ball release. This indicates poor utilization of trunk rotational torque in the delivery of the pitch.

Graph IV address the relative position of the subject’s right shoulder vs. his center of gravity, at ball release. It is noted that the relative position of his right shoulder to center of gravity indicates his 21.5 inches forward of his c.g. at ball release.

Discussion: The subject’s basic form is good but there is room for improvement in all aspects of his delivery. He is noted to have a pre-mature braking action of forward momentum. This causes him to release the ball in an upright posture that places the burden of shoulder capsule stress in the anterior compartment. This release posture is verified by examining the relatively close positioning of shoulders vs. hips and right shoulder vs. center of gravity.

Conclusion: Within a reasonable degree of scientific probability, the subject’s pitching technique is contributing to an acute overuse syndrome, anterior right shoulder.

Recommendations: From a biomechanical prospective, to minimize shoulder stress in this subject’s pitching technique, it was recommended that he strive to relax his shoulder and utilize better control of trunk torque in the delivery of forces from the ground through the hand. He should delay ball release somewhat until his body is in a more forward flexed posture and the upper arm segment is skewed more towards a parallel ground position. This will shift the stress point to the superior shoulder and away from the anterior shoulder capsule. The additional body stretch and torque will eventually translate to higher kinetic energy and faster ball delivery. It was stressed that changing his pitching style will adversely effect his accuracy and ball delivery ability until he re-adjusts his body coordination. It will be necessary for him to work on total body flexibility in order to achieve new ball release position.

Outcome: The subject is adjusting to his new pitching style. He is currently pain free and pitching at 100% effort. He is looking forward to Spring Training for a second chance.

Overview: Modern technological application of the principles of Biomechanics can be an extremely useful tool in problem solving sports medicine questions. The clinician must be prepared to make judgements based on objective data, when addressing the issue of returning the injured athlete to his or her sport. Often adjustments can be made in sport technique to de-stress the injured body part, either on a temporary or permanent basis. In the case presented here, permanent change was necessary to allow this athlete to return to his sport and pursue his dream.

Tools such as the Ariel Performance Analysis System, allow the clinician to derive pivotal information about an athlete’s performance. This data often means the difference between success and failure for the ailing athlete. Reduced cost and increased accessibility to this technology, will mean that future school, amateur, and recreational athletes will have a better chance to stay healthy and prolong their sports endeavors.

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