All athletes will develop special physical characteristics that are specific to their sport due to repetitive use of certain muscle groups as well as movement patterns required of that sport. Overhead athletes are no exception to this observation. Here are some of the physical characteristics to keep in mind of an overhead athlete upon initial evaluation – summarized from Wilk et al’s clinical commentary on shoulder injuries
Range of motion
In PT school, we’re all taught that normative values for external rotation and internal rotation (when measured in supine at 90° abduction) are 90° and 70°-90° respectively. That gives us a 160°-180° of TOTAL motion. It is important to keep the concept of total motion in mind, especially when dealing with overhead athletes. In baseball pitchers, there tends to be increased external rotation and decreased internal rotation. In a Wilk et al (2009) clinical commentary piece, Bigliani et al found that on average pitchers exhibited 118° of external rotation. Similarly, Reinold et al state that baseball pitchers ranged from 129°-137° of ER and 54°-61° of IR for a combined arc of 183°-198° of total motion. When looking at range of motion, I tend to stress the TOTAL arc of motion because the dominant/throwing arm will tend to have increased ER and decreased IR, but if the total arc of motion remains the same bilaterally then there isn’t a deficit; throwing tends to reduce IR. However in a baseball pitcher, if the total arc of motion is decreased when compared side to side, usually it will be due to a pathological loss of IR.
Laxity and Osseous Adaptations
Most throwers will have some form of acquired laxity that can be noted through a physical assessment. Most of it is due to repetitive stress on the capsule – increased posterior capsular laxity when compared to anterior capsule.
In Wilk et al’s clinical commentary on shoulder injuries they bring up osseous changes in the humeral head that I found interesting. They stated that in most studies, there was on average a 17° of humeral retroversion in the throwing arm. This can have impacts on posture as well as the relationship between the humerus and scapula. This can also explain the differences in ER/IR ROM when measured R vs. L, though the total arc of motion may remain the same.
Due to repetitive motions, every athlete has muscle imbalances somewhere along the kinetic chain. With baseball pitchers, often times their internal rotators on their throwing side are stronger than their external rotators and tend to have strong adductors as well. Proper balance between antagonist and agonist is crucial to providing dynamic stability around any joint. There is a theory that proposes the external rotators should be at 65% of the internal rotators strength for optimal stabilization around the glenohumeral joint.
Due to the aforementioned muscular imbalances, overhead athletes often will have changes to the resting position of their scapula and thoracic spine. The two more common postural changes include an anteriorly tipped scapula when the shoulder is at rest and an upwardly rotated shoulder when the shoulder was abducted to 90° due to increased activity of the adductors (pec minor) and protractors/internal rotators (subscapularis, serratus anterior, latissimus dorsi).
It is great to be able to identify these impairments and deficits, but if you are unable to treat them, then what’s the point? Treatment, including neuromuscular re-education and manual therapy tips, to follow in part 4. But first, we need to understand the biomechanics of an overhead athlete before we can treat. Continuing our assessment is Part 3: Biomechanics and Movement Patterns of the Overhead Athlete.
Reinold et al 2014 Current Concepts in the Evaluation and Treatment of the Shoulder in Overhead Throwing Athletes, Part 2
Wilk et al 2009 Shoulder Injuries in the Overhead Athlete