Yanai, T., & Hay, J. G. (1996). The mechanics of shoulder impingement in front-crawl swimming. Medicine and Science in Exercise and Sports, 28(5), Supplement abstract 1092.

An analysis of the arm movement patterns in crawl stroke swimming and range of arm movements that resulted in shoulder impingements was made on elite male collegiate swimmers (N = 11).

More than 70% of impingements in the swimming stroke occurred at and immediately after the entry. The other 30% occurred at the initiation of a backward motion of the hand with vigorous, simultaneous internal rotation and horizontal abduction of the stroking arm. The attainment of a large body roll did not appear to reduce the amount of impingement.

Implication. In crawl stroke, shoulder impingements occur mainly on entry. Two actions can be instituted to reduce the amount and/or severity of impingement: (a) bend the arm at the elbow as the entry is made and hold or increase the bend as the hand-forearm is positioned to developed propulsion, and (b) do not exaggerate an "overtaking" stroke pattern since that restricts the positioning of the shoulder socket and its capacity to accommodate upper arm positions which are necessary to produce significant propulsion.

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