Courtesy of Gary Hall Sr., 10-time World Record Holder, 3-time Olympian, 1976 Olympic Games US Flagbearer and The Race Club co-founder.
Happy Feet, Happy Swimmer — Part I
Recently, I have spent a great deal of time using the Race Club Velocity Meter technology to analyze the dolphin kick. After all, the dolphin kick has become so important in all of the swimming strokes that it is now considered The Fifth Stroke. The Velocity Meter allows one to study the velocity and acceleration/deceleration of the swimmer’s body throughout the kicking cycles.
The Fifth Stroke
Surprisingly, not a lot of scientific research has been done on the propulsion of the dolphin or flutter kick. In one of our recent videos, The Fifth Stroke Part I, Olympic Champion Roland Schoeman demonstrates a powerful dolphin kick with and without fins. These exquisite slow motion video images enable us to see the extraordinary flexibility of the ankle, particularly during the down kick, coupled with strong legs, which enables such great kick propulsion to take place.
The maximum propulsion from the kick occurs at the beginning of the down kick with a flick of the foot toward plantar flexion of the ankle. The more plantar flexion of the ankle, the more foot surface area is available to push backward in the water, creating propulsion.
The Down Kick & The Up Kick
While it is only during the down kick that the foot is actually moving backward in the water, I was surprised to find that there is some propulsion on the up kick, even though the foot is moving forward during this motion.
This can only be explained by the fact that the previous down kick and the swimmer’s body creates a stream of water moving forward and downward that is greater than the speed of the foot moving forward. Within this hydrodynamic system, the foot can still produce propulsion while it is moving in a forward direction. Acceleration of the body occurs in the up kick from the time the legs are horizontal with the body upward to nearly the end of the upstroke.
Down Kick x2 Power of Up Kick = Velocity
The velocity of the swimmer in the water reached after the down kick is about twice that of the velocity after the up kick. With the exponential relationship between velocity and frontal drag, that would mean the down kick likely produces roughly four times greater propulsive force than the up kick. Regardless, both the up kick and the down kick are important, so the fast kickers are working the legs in both directions.
In freestyle, I consider the speed of the kick to be the baseline speed of the swimmer before the arm pull is added in. It is almost as if a swimmer has a choice of swimming in a pool or a stream. With no kick propulsion, the swimmer is swimming in a pool where there is no current. With a kick, the swimmer is now swimming with the current in a stream. The stronger and faster the kick, the faster the current is moving in the stream. With a strong kick, when you add the arm pull, a swimmer can rip down the stream.
The kick is even more important in fly, breaststroke and backstroke than it is in freestyle. Yet it is important in all four strokes. Work on ankle flexibility, leg strength for the kicking motions and leg fitness to sustain those motions and you will see great improvement in your swimming times.
Watch The Fifth Stroke Swimisode:
Yours in swimming,
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