經常游泳的人通常有旋轉家受傷的問題，這個小運動對於肩部的保健，或甚至受傷的復健都有良好的作用。尤其是手背用力推水(相當網球反拍動作)，因為所有泳式都沒有這個方向施力的動作。

Shoulder Exercises

This exercise is good for rotator cup, it could help increase shoulder strength as well as mobility, and it's a good warm-up workout, too.  I think it could be a workout of rehab helping address rotator cup injuries.  Doing the move with your back of the hand would be more beneficial because we seldom move our hand/arm that way, I think that could exercise the antagonists to the muscles we employ during swimming.  The weak antagonist is often the reason that caused sports injuries.