Produced, edited, and copyrighted by
Professor Brent S. Rushall, San Diego State University
Volume 6, Number 3: February 12, 2001


Dear Brent:

The following is today's chapter in yet another tiresome debate on I am only sending it to you because you may not have yet seen the quoted journal articles:

Subject: Swimming Technique & Shoulder Injury
Date: 09 February, 2000

Finally got the full text copies of the new articles on impingement in front crawl swimming from my medical library. [Yanai, Hays, & Miller. (2000). Shoulder impingement in front-crawl swimming: I A method to identify impingement. Medicine and Science in Sports and Exercise, 32, 21-29; and Yanai & Hay. (2000). Shoulder impingement in front--crawl swimming: II Analysis of stroking technique. Medicine and Science in Sports and Exercise, 32, 30-40.

These are complex papers and I will, over the next few days, try to explain the research and conclusions described in these articles. Some of the more important findings are as follows:

  1. Impingement (in a group of 11 male collegiate varsity swimmers) was present in all swimmers, for a mean of 25% of the total stroke time. But, it was not present in all phases of all strokes. In some stroke cycles in all swimmers, no impingement was present at all. This indicates that impingement is a function of technique and that technique may be modified to avoid impingement, which is felt to be the major cause of serious shoulder injuries in swimming.
  2. As a function of total impingement time, 40% of total impingement time was at hand entry and catch, 40% was during recovery, and only 20% was during the actual "pull" phase of the stroke. During recovery and pull, impingement was largely a result of internal rotation (counterclockwise orientation of the right hand during recovery and pull and clockwise orientation of the left hand during recovery and pull). Thus, close to 60% of impingement could be avoided simply by avoiding or reducing internal rotation during recovery and pull. As I have suggested elsewhere, this may be achieved by (1) a straight arm over the water recovery with thumb forward, rather than downward or (2) a more traditional bent elbow recovery, but with the recovering hand immediately "feathered" to a thumb forward position upon exit from the water. Additionally, during catch and pull, the thumb should be kept slightly forward (toward the direction of the head) of the little finger at all times.

With regard to the 40% of impingement that occurs at the time of hand entry and initial catch, here is what the authors had to say:

"At, and shortly after, arm entry, the hand is subject to resistive forces from the water. A swimmer is accustomed to having a complete elevation of the shoulder during this period so that he can reach well forward to "catch the water." Such an arm position causes the fluid force exerted on the hand to generate a large moment about the shoulder joint because of the long moment arm associated with that arm position. This large moment tends to elevate the arm forcibly to, or beyond, the maximum active elevation angle. Such a forcible elevation of the arm might generate a large compressive force on the subacromial structure, with accompanying shoulder pain caused by impingement (Note: This is the same position used for the "impingement test" described by Neer and Welch" [Neer & Welch. (1977). The shoulder in sports. Orthop Clin North Am, 8, 583-591.

The above direct research supports my hypothesis (based on anatomical principles) that the "long forward" position in crawl stroke is likely to be a prime contributor to shoulder injury. It is logical to expect that increasing the emphasis on the "long forward" is likely to result in an increased incidence of shoulder injury.

It was stated that "improved balance" could be a mitigating factor. In fact, the opposite is more likely to be the case. Elsewhere in the article the authors noted that increasing the "tilt angle" through lateral bending of the trunk (as occurs, for example during the "loping stroke" head lift and as advocated in a prior publication in the orthopedic literature (Penny & Smith. (1980). Prevention and treatment of swimmer's shoulder. Canadian Journal of Applied Sport Sciences, 5, 195-202), serves to lessen impingement forces associated with the forward reach. By assuming a perfectly flat and balanced position in the water, and - especially - combined with a position in which the recovering hand is carried forward of the head at the same time the lead hand is still fully outstretched in the water, tilt angle will be MINIMIZED and impingement force will be MAXIMIZED.

How to resolve the above facts with the reports elsewhere on this newsgroup that such "front quadrant swimming" serves to, in fact, reduce rather than increase incidence of shoulder injury is a paradox for which I see no obvious explanation.

Larry Weisenthal
Huntington Beach, CA

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