The freestyle technique of the straight arm shifting arm is somewhat controversial. I have found that some coaches either believe that using this technique may be more likely to cause shoulder problems, or that young swimmers are not strong enough to use the straight arm arming technique.
I have not found any evidence that these two concepts are true. We advocate the use of straight arm booms in the 50m freestyle and in the end of all freestyle (including medley) matches. If the swimmer is particularly comfortable using a straight arm, we also consider using this technique in the 100m freestyle.
By straightening the arm, the amount of work required for the swimmer to move the arm over the water is increased by a factor of four. The only reason swimmers make moving their arms more difficult is to get more power and speed. This is especially important in short distance races. The extra energy and speed of the straight arm arm are obtained by what we call a coupling process. The increased kinetic energy of the straight arm shifting arm increases the propulsion of the stroke and kick.
If you watch Nathan Adrian's 100m freestyle, you will see his last 8 meters moving from a high elbow to a straight arm, which increases the speed and frequency of the stroke. Compared to any swimmer I remember, Nathan has won more gaps in the game. He was the most famous match in the London Olympics 100m freestyle final.
Although some well-known swimmers use straight-armed freestyle techniques (Janet Evans, Leah Smith, Lotte Fries) in longer races, they are known for their strong professionalism. It is one thing to increase the arm movement by 30 seconds, and keeping the high-intensity arm within 15 minutes is another matter.
The vast majority of shoulder problems are tendinitis or impact problems, which are mainly caused by overtraining. Since we are advocating the use of this technique in short-distance sprints, we have not seen the possibility of causing any type of shoulder problems, especially when done correctly, as long as the training duration and distance are shorter.xx
所有仰泳者都使用直臂移臂。1936年奥林匹克运动会的Adolph Kiefer（他以1: 08获胜）是最后一位成功使用曲臂移臂的精英仰泳选手。在仰泳中使用曲臂移臂会导致严重的力量损失。