Part II: The Importance of the Up Kick
One of my pet peeves is when coaches refer to the up kick on freestyle (or dolphin kick) as the ‘recovery phase’ of the kick. While the biomechanical strength of the down kick is at least double that of the up kick, the up kick also creates propulsion. A stronger up kick not only creates more propulsion, but it also creates a bigger vortex behind the foot, which leads to even more propulsion on the following down kick. To become a fast kicker, there is no recovery phase. By working the kick in both directions, just like a fish does, you can learn to kick faster.
The propulsion generated by the foot is highly influenced by the vortices caused by the swimmer’s body and moving feet. The foot on the up kick, for example, never moves backward relative to a fixed point in the pool. It moves upward and forward. Yet, the up kick can still generate propulsion because the foot is moving through a stream of water flowing forward behind the swimmer (vortex). So long as the stream is moving forward faster than the foot, or the foot is moving backward relative to the water, the foot can create propulsion.
When you turn the swimmer over onto his back, whether doing flutter or dolphin kick, the acceleration, deceleration and velocity curves all change significantly from those seen when kicking on the stomach. When the swimmer is on his back, suddenly the weaker down kick creates as much or more propulsion as the stronger up kick. The reason is that now the down kick pushes against a much stronger stream (vortex) than with the up kick, where the foot drops below the stream. The up kick contributes to the increased strength of the vortex for the following down kick. With less biomechanical strength, the down kick will now produce the same or more propulsion than the more powerful up kick. That is the influence of the vortex.
One of our favorite drills to teach the up kick is doing dolphin kick with fins underwater and on one’s side. We teach the swimmer to not let go of the water with the fin. In other words, we want the swimmer to feel the pressure of the down and up kicks at all times, snapping the fins down on the down kick and drawing the fins up quickly for the up kick. Sounds easy to teach, but in order for swimmers to really get it and practice it, The Race Club has a methodology.
Another great drill for developing the up kick is the vertical kick. If one relaxes on the up kick doing this drill, the head will drop down under water. The only way to keep the head above water at all times is by working both the up and down kicks hard.
Yours in Swimming,