Purpose: The purpose of this study was to determine the technical causes of shoulder impingement experienced by front-crawl swimmers. Methods: The shoulder movements exhibited during performance of the front-crawl stroke were measured using three-dimensional videography, and the instances at which each shoulder was experiencing impingement were identified. Results: On average, impingement occurred 24.8% of the stroke time (%ST). In one or more phases of the stroke cycle, each subject experienced impingement in some trials and not in other trials. This suggests that stroke technique, and not just anatomical differences, accounted for individual susceptibility to shoulder impingement. No significant difference was found between the mean values for %ST for slow and fast stroking speeds and for trials with and without hand paddles. Use of a unilateral breathing technique was often associated with a small magnitude of tilt angle (an effect of the scapular elevation/abduction on one side and depression/adduction on the other side) on the breathing side; in such cases a high incidence of shoulder impingement was observed for the shoulder on the ipsilateral side. Swimmers at high risk of experiencing shoulder impingement had three characteristics in their stroking techniques: (a) a large amount of internal rotation of the arm during the pull phase, (b) a late initiation of external rotation of the arm during the recovery phase, and (c) a small amount of tilt angle. Conclusions: A swimmer should be able to reduce the risk of developing shoulder impingement by altering the technique to eliminate the three characteristics.
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