Swimmer's shoulder

Swimming Technique, Apr-Jun 2000 by Weisnthal, Larry M

Most swim coaches and orthopedic physicians do not really understand swimmer's shoulder. It is important to understand the anatomy of the shoulder as well as the techniques and methods for avoiding injury.

This is the first of a taco-part series on swimmer's shoulder:

Shoulder injuries in swimming are most often caused by impingement. Impingement is worst at 90 degrees (mid-recovery and mid-pull through) and 180 degrees of elevation (position of the long forward reach). It is made worse by internal rotation of the arm.

The keys to shoulder-friendly swimming technique are to avoid internal rotation during recovery and pullthrough, to reduce the extent and duration of forward reach, and to delay the application of pull forces until the leading hand has descended well below the position of long forward reach.

Injuries to the shoulder are the cause of considerable lost training time and many shortened swimming careers. Numerous studies have documented that between 25 to 35 percent of high level competitive swimmers experience interfering shoulder pain. Also, 60 to 75 percent of these swimmers will have a serious shoulder problem at some time during their careers. In addition to lost training time, these injuries are the cause of considerable medical expense, emotional distress and abandoned careers.

Given the magnitude of this problem, it is obvious that one of the major goals of both coach and swimmer would be to avoid or minimize these injuries. Coaches and swimmers alike should have the same level of knowledge of techniques and training methods for injury avoidance as they have for techniques and methods for swimming fast. Sadly, it is obvious that even the greatest coaches often have little understanding of mechanisms of injury as well as techniques and methods for avoiding injury.

Conversely, orthopedic surgeons and other medical professionals have a clear understanding of mechanisms of injury, but too often have an incomplete understanding of the nuances of swimming technique which contribute to this injury.

The situation could be greatly improved if swim coaches had a better understanding of anatomy and if orthopedic surgeons had a better understanding of swimming technique.

Try raising your arms over your head. Now, move them around. Better yet, mimic crawl and butterfly, straight overhead and reaching for the ceiling. Strive for maximum forward (upward) "extension" (actually forward flexion/abduction, in proper anatomic terms) as you rotate your hips. Can you feel the stress and strain?

The human upper extremity was not designed nor did it evolve to do movements like this. In contrast to running (or even throwing), competitive swimming is a completely unnatural activity for which humans did not evolve and to which it is often impossible to adapt.

Simplified Anatomy

The head of the humerus is joined to the shoulder blade (scapula) at a very small indentation in the scapula called the glenoid.

There is a thin rim of cartilage around the glenoid called the labrum. This sometimes tears, which can contribute to pain and cause a clicking sound. Tom cartilage doesn't heal.

The humerus is joined to the scapula by a sheath of dense ligaments known as the joint capsule.

Over the joint capsule inserts a sheath of tendons collectively called the rotator cuff. This is a coalescence of the tendons of four different muscles which originate from various positions on the scapula and insert on the proximal humerus to rotate it. These muscles are called the teres major and minor, subscapularis and supraspinatus. It is the last of these muscles and its tendon which causes most of the trouble.

The supraspinatus originates in a groove on the top surface of the scapula. It is a skinny muscle which runs along the top of the scapula, then ends in a tendon which eventually interdigitates with the other tendons of the other three muscles which collectively form the rotator cuff.

The function of the supraspinatus is to move the arm away from the body. (In anatomic parlance, the "arm" is what lay people call the "upper arm," as opposed to the forearm, which is below the elbow.) The supraspinatus is responsible for the first 15 degrees of this "away" motion (properly called abduction), until the much larger/stronger deltoid muscle is in place to take over and abduct it the rest of the way.

The problem with the suprapinatus (besides being a small muscle doing a big job) is that the tendon has to travel underneath an outcropping of scapular bone called the acromion before it can attach to the humerus. If the arm had been designed to work overhead, the acromion would have been entirely redesigned with respect to position and shape.

But the problem is that the acromion forms a roof (I call it a "carport") over the supraspinatus tendon, which does a dandy job of protecting it from injury (e.g., a blow from a club or when some oaf claps you on the shoulder, saying "How 'bout them Dawgs!"). It is also a rigid structure which grinds into the supraspinatus tendon when the latter is elevated during overhead arm activities (like swimming).