I just came across an interesting analysis of the underwater kick by Genadijus Sokolovas: Video Analysis of Underwater Kick (https://learning.fina.org/video-analysis-of-underwater-kick/). It appears to be recently posted on Fina.org, although the article is not dated.
The article analyzes various phases of the underwater kick--essential knowledge for all coaches and swimmers. At the end of the article the author gives recommendations on how to improve the underwater kick. His recommendations are good except for his suggestion to wear shoes, which I don't agree with. The impact on technique and balance, reduction in range of motion and prohibiting feel for water make kicking with shoes detrimental to improving underwater kick. They do make kicking harder, but they don't improve your kick. I have written about this before:
Because of their weight, running shoes pull swimmer's legs down therefore encumbering streamlined body position and balance. Getting out of balance hinders the swimmer's technique.
Another downside of swimming with shoes is that shoes restrict ankle movement and minimize the range of motion of swimmer's feet resulting in a less efficient kick.
Yet another important reason against kicking in shoes is that the shoes prohibit feel for water. If the swimmer doesn't feel the water he can never achieve maximum efficiency.
In fact, we invented DragSox to address the need to create resistance while maintaining technique and feel for the water.
- DragSox don't add any weight, only resistance without negatively affecting swimmer's body position.
- Unlike shoes that pull the swimmer's leg down, DragSox pull the swimmer back forcing him to work harder. DragSox don't restrict ankle movement in any way.
- And finally, DragSox enhance the feel for water. As the swimmer kicks in DragSox, the material waves slightly to and fro across the feet in absolute accord with each phase of the kick sensitizing the sensory receptors as it touches the skin.
To summarize, if you want to improve underwater kick, don't kick in shoes. Your legs might get stronger but you won't get faster.