Fix Your Kick!
The biggest problem many swimmers have is an asymmetrical kick
One of the biggest problems many swimmers have is an asymmetrical kick. It shows up in butterfly, backstroke and freestyle on the starts and streamlines, as well as in both freestyle and backstroke flutter kicks. Many swimmers put a great deal of pressure on the water with the tops of their feet when kicking but nothing with the bottoms (the upstroke in butterfly and freestyle and the downstroke in backstroke are areas of untapped propulsive force). There are several drills to work on this problem.
Kick butterfly on a streamline, all underwater, starting on your front, then rotating to the side, back and other side for four kicks each. Most people are OK on the front because of a strong down kick in this position but the minute they go to the side or back they have problems. This indicates that the kick is not balanced. Do this 25 yards at a time, breathing whenever necessary. It’s about finding the balance and making sure there is propulsive force in both the up and downward portions of the kick.
Underwater Flutter Rotation
Do this just like the four-kick rotation, only with eight kicks. Breathe as needed.
Kicking on Your Back
Kicking fly on your back is all about being able to kick both directions. When swimmers get a wash of water moving up towards their face while kicking fly on their backs, typically it means that they are pushing at the water with the tops of the feet and not kicking down with the bottoms of the feet. For backstroke keep the knees under the water and hold a kickboard on top of the knees to prevent the pawing at the water that also indicates an asymmetrical kick.