The Impact of Throwing on an Athlete’s Shoulder

Jul 20, 2016

Kevin Davi

by Kevin Davi
PT | Sun City Location

Many young athletes and parents of athletes who participate in sports that involve throwing, whether it’s baseball, softball, football, or otherwise, worry about the impact these sports will have on their shoulders. A high level of stress is placed on the shoulder joints during these activities, but participation in these sports does not have to mean an inevitable injury, thanks to the body’s incredible ability to adapt. Here’s what you should know about the impact of throwing on your shoulder.
Part 1: For Athletes
Understandably, shoulder injuries of soft tissues are common in athletes participating in overhead throwing sports. These athletes are subject to high forces placed on the glenohumeral joint (shoulder joint). This is due to the tradeoff between stability and mobility that takes place. More stable joints are stronger and less likely to be injured, but more mobility allows great capability to reach for and manipulate objects. Relative to other weight-bearing joints, the shoulder sacrifices stability for mobility. In comparison, our knee joint sacrifices mobility for stability, because this allows us to bear weight without collapsing. Lower stability in the shoulder joint places a heavy strain on our soft tissues, such as the rotator cuff muscles and anterior shoulder capsule, during throwing sports.
Participation in throwing sports has an observable impact on the shoulder. Studies of baseball players at the collegiate and professional levels have shown vast differences in the shoulder anatomy of the players compared to non-throwing athletes. Imaging has been used to study and measure the amount of torsion (or twist) in the humerus bone. These studies have shown throwing athletes to have, on average, between 10 and 19 degrees more torsion than non-throwing athletes and even the athlete’s own non-dominant shoulder.
This phenomenon of adaptation in bone is known as Wolf’s Law. Wolf’s Law states that bone will adapt to the forces placed on it. Theoretically, this allows the shoulder to reach the loading phase of throwing (the fully cocked position) while placing less stress on the front of the shoulder. This means that throwing athletes’ bodies naturally allow them to use their shoulders more forcefully without injury.
Crockett et. al (2002) believes that adaptations of the bone occur at a young age, and it becomes an advantage because it allows more external rotation without straining the anterior capsule (front of the shoulder). He also concluded that a well-monitored, age-appropriate pitching program should be implemented in Little League baseball for this reason, because if a child’s arm adapts early, they will be less likely to become injured later. This is why he says the concept of ‘saving my child’s arm’ in Little League with the intent that they will pitch when their arms become stronger in high school, or even later, may be a bad idea.
Part 2: For the Physical Therapist
Different methods of measuring shoulder range of motion are affected by the amount of retroversion, or how much a shoulder is tipped back, which makes assessment of soft tissue difficult. Comparing side-to-side differences in total arc of motion seems to be the best method of assessing whether or not soft tissue differences exist. However, figuring out which soft tissues are contributing to total arc of motion cannot be determined without first measuring retroversion using imaging technology.
If you participate in a throwing sport, it is normal to experience changes in your shoulder and lessened shoulder stability. However, due to the body’s adaptive abilities and intervention from physical therapists, you can participate in throwing sports without experiencing a shoulder injury. If you have more questions about shoulder strength, mobility, or injury, then please contact your local Foothills Arizona Sports Medicine clinic today.
 
References:
Changt, C.B., Litchfield, R., Griffin, S., & Thain, L.M. (2007). Humeral head retroversion in
competitive baseball players and its relationship to glenohumeral rotation range of motion. Journal of orthopedic & sports physical therapy, 37(9), 514-520.
Crockett, H.C., Gross, L.B., Wilk, K.E., Schwartz, M.L., Reed, J., O’Mara, J., Reilly, M.T., Dugas, J.R.,
Meister, K., Lyman, S., & Andrews, J. (2002). Osseous adaptation and range of motion at the glenohumeral joint in professional baseball pitchers. Am J Sports Med, 30(1), 19-26.
Myers, J.B, Oyama, S., Goerger, B., Rucinski, T., Blackbum, T. & Creighton, A. (2009). Influence of
humeral torsion on interpretation of posterior shoulder tightness measures in overhead athletes. Clin J Sport Med. 0(0), 1-6.
Osbahr, D.C., Cannon, D.L., & Speer, K.P. (2002) Retroversion of the humerus in the throwing
shoulder of college baseball pitchers. Am J Sports Med. 30, 347-353
Pieper, H.G. (1998). Humeral torsion in the throwing arm of handball players. Am J Sports Med 26.
247-253
Reagan, K.M., Meister, K., &Horodyski, M.B., et al. (2002). Humeral retroversion and its relationship
to glenohumeral rotation in the shoulder of college. Am J Sports Med, 30, 354-360

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