There are many possible reasons for SS to develop. SS injury and pain from impingement and other related issues seems to occur under one or more of the following circumstances (Anderson, Hall, & Martin, 2000; Bak & Fauno, 1997; Costill, Maglischo, & Richardson, 1992; Johnson, Gauvin, & Fredericson, 2003; Maglischo, 2003; Pollard & Croker, 1999; Tuffey, 2000; Otis & Goldingay, 2000; Weisenthal, 2001). SS is considered an impingement related injury that seems to develop through a mechanism related to overuse or instability (Anderson, Hall, & Martin, 2000; Bak & Fauno, 1997; Baum, 1994; Chang, 2002; Costill, Maglischo, & Richardson, 1992; Johnson, Gauvin, & Fredericson, 2003; Koehler & Thorson, 1996; Loosli & Quick, 1996; Maglischo, 2003; mayo Clinic, 2000; Newton, Jones, Kraemer, & Wardle, 2002; Pink & Jobe, 1996; Pollard, 2001; Pollard & Croker, 1999; Reuter & Wright, 1996; Richardson, Jobe, & Collins, 1980; Tuffey, 2000; Otis & Goldingay, 2000; Weisenthal, 2001):
- faulty stroke mechanics
- sudden increases in training loads or intensity
- repetitive micro traumas related to overuse
- training errors (such as unbalanced strength development)
- use of training devices like hand paddles
- higher levels of swimming experience
- high percentage of freestyle swum in practices
- weaknesses in the upper trapezius and serratus anterior
- weakness or tightness of the posterior cuff muscles (infraspinatus and teres minor) or a hyper mobile or very lax shoulder joint.
Swimmers perform a great number of overhead arm motions in the course of a normal practice week; Pink and Jobe (1996) estimate that some swimmers may complete as many as 16,000 shoulder revolutions in a one week period, while Johnson, Gauvin, and Fredericson (2003) estimate this number could be as high as 1 million per year. To gain a sense of scale, Pink and Jobe (1996) compare swimmer's arm motions with 1,000 weekly shoulder revolutions for a professional tennis player or a baseball pitcher (Pink & Jobe, 1996).
Given the swimmer's quantity of movements and the range of those movements, micro traumas are inevitable, and damage from repeated micro traumas can develop into SS (Bak & Fauno, 1997; Chang, 2002; Costill, Maglischo, & Richardson, 1992; Johnson, Gauvin, & Fredericson, 2003; Pink & Jobe, 1996; Pollard & Croker, 1999; Otis & Goldingay, 2000). It appears that there are three main syndromes behind SS (Pollard & Crocker, 1999; Weisenthal, 2000):
- instability
- impingement
- tendonitis
Tuffey (2000) lists the triad of problems involved with SS as:
- biceps tendonitis
- subacromial bursitis
- rotator cuff tendonitis usually in the supraspinatus muscle.
Richardson, Jobe, and Collins (1980) summarize SS as a chronic irritation involving the humeral head and rotator cuff interacting with the coracoacromial arch during shoulder abduction resulting in an impingement, as do Otis and Goldingay (2000).
