An estimated 100 million participants enjoy swimming at all levels. Swimming has no impact activity and few inherent risks except for overuse problems. Stroke characteristics in swimming have four phases: reach/catch/pull/recovery. Arm action provides the main (75%) propulsion in all strokes except breaststroke.
Elite swimmers rely on their shoulders for an average of 13,000 meters per week. In addition, competitive swimmers swim six days per week over a ten month period, attaining approximately two million strokes per year. Extremes of the shoulder movement during swimming tend to cause glenohumeral joint (GHJ) laxity and these repeated stresses may result in cumulative micro trauma within the shoulder joint. The repetitive nature of swimming apparently predisposes the shoulder to mechanical and anatomical deficiencies which may lead to a spectrum of overuse injuries such as an undesirable increase in joint laxity, tendonitis and impingement of the rotator cuff.