Applied biomechanics of swimming

Marilyn M. Pink, George T. Edelman, Russell Mark and Scott A. Rodeo

When clinicians think “overhead athlete,” swimming is one of the sports that come to mind. Some of the other sports include throwing and pitching, volleyball, and tennis. In the past, the mechanics of the “overhead athlete” were sometimes viewed collectively. Most of the “overhead” sports are mechanically at risk during humeral abduction and elevation with external rotation. That is not the case with the swimmer. It is now clear that the requirements of each sport are distinct, and the precise requirements are able to be defi ned. Thus, this chapter provides an opportunity to describe the specifi c biomechanics of swimming as they relate to the clinician.
One unique aspect of swimming mechanics is that the power comes from the muscles of the shoulder girdle. In most sports, there is a ground reaction force and power is transmitted from the legs through the trunk and scapula and out the arms. In swimming, however, the body is being pulled over the arms. Thus the arms are the propulsive mechanism, and the shoulders are quite vulnerable, especially if the scapula cannot act as a stable base for the glenohumeral control muscles. Therefore, one of the primary foci of this chapter is the shoulder.
Because the shoulder is the focus, the most visually apparent pathomechanical clue to impending injury is that of axial rotation and humerus position. The visually apparent pathomechanics are discussed, as are the pathomechanics that are harder to see. These pathomechanics are related to their effect on shoulder injury. In addition, shoulder muscle fi ring patterns in the normal and the painful shoulder are discussed. The emphasis of this chapter is identifying injury early and taking steps to minimize anatomic damage. 
To identify the subtle signs of impending injury, a bridge between the coach and on-deck personnel and the medical team must be built. Hence, this chapter presents such a framework and offers the clinician a problem-solving approach to minimize anatomic damage in the swimmer’s shoulder. 
Swimmer Characteristics

Unfortunately, approximately half of competitive swimmers develop shoulder pain severe enough to cause them to alter their training schedule at some point during their swimming career. 1 In a survey of 532 collegiate swimmers and 395 master swimmers, not only did approximately half the swimmers have a history of 3 or more weeks of shoulder pain that forced them to alter their training, but more than half of the injured swimmers also had a recurrence. These data point to the need for long-term intervention in the competitive swimmer. 
In a separate unpublished survey of 233 competitive swimmers on 17 collegiate teams, the location of pain was queried, as were the positions during the stroke of the most intense pain. 2 The anterior-superior region of the shoulder was identifi ed in 44% of the swimmers as the area of pain. 
Diffuse pain was identifi ed in 26% of the swimmers, with lesser frequencies reported for the anterior-inferior region of the shoulder (14% of the swimmers), posterior-superior region (10% of the swimmers), and posterior-inferior region (4% of the swimmers). It is likely that swimmers who identified diffuse pain had not acknowledged the pain when it was more localized, and the inciting symptoms were masked by inflammation or more severe damage.

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