The effect of fatigue on the underwater arm stroke motion in the 100-m front crawl.

The purpose of this study was to indicate the effect of fatigue on the underwater right arm stroke motion during the 100-m front crawl. The arm stroke motions of eight male competitive swimmers were captured three-dimensionally at 60 Hz in the positions of 15 m and 65 m from the start. The hand velocity, the arm angular velocities and the relative contribution of the arm angular velocities to the hand velocity were computed at each instant during the arm stroke motion. A significant decrease of the hand velocity and the peak angular velocity of shoulder adduction were observed in the second half than in the first half. The contribution of shoulder adduction was especially large in the pull phase and subsequently that of shoulder horizontal abduction became dominant in the push phase. However, in the second half, the contribution of shoulder adduction tended to decrease while that of shoulder internal rotation tended to increase. Thus, it is quite likely that the arm stroke motion of swimmers were driven to be influenced by induced fatigue and resulted in an increase in the contribution of shoulder internal rotation to compensate the decreased contribution of shoulder adduction angular velocity.