Copied from TI.
Hi Brad
Counsilman's position isn't quite as simple as saying the flutter kick provides no propulsion. Obviously, by itself, it does provide propulsion, and people like Popov can kick at pretty amazing speeds. But they can also pull at amazing speeds. And when they kick and pull together the result is even faster.
Here is a short excerpt from what Counsilman said about the kick in The Science of Swimming (1968):
The arm stroke in the crawl is the main source of propulsion and, in the case of most swimmers, the only source of propulsion. The kick serves primarily as a stabilizer and means of keeping the feet high in a streamlined position. As mentioned before, the lateral thrust of the kick serves to cancel out the effect of the recovering arm in disturbing body alignment.
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The question of whether the swimmer gets any propulsion from his kick depends on whether the feet can push water backward faster than the arms are pulling the body through the water. If in order to achieve this speed, the swimmer has to kick as hard as possible, would he not be better off to use this energy to pull himself through the water with his arms, using only enough energy in kicking to maintain body alignment?
He then describes an experiment where swimmers were towed at various speeds while kicking and not kicking.
... The tension on the rope was measured to see if it was greater, the same or less when kicking than when just being towed in a glide position. Generally at the lower speeds of under five feet per second, when the swimmer kicked at maximum effort, the tension on the rope decreased. However, when the swimmer was pulled at speeds greater than five feet per second, he not only did not contribute anything to the speed at which he was being towed, but, in some instances, actually created an increased drag as a result of his kicking... Some swimmers' kicks became ineffective at four feet per second.
... No crawl swimmer swimming a distance event (the 1500 meters event, for example)at a rate of four or five feet per second would be expected to kick as hard as possible for the full distance. The trend is exactly in the opposite direction. The longer the race the less emphasis placed on the kick by the swimmer.... If the swimmer kicks exceedingly hard, too much blood is channeled to the leg muscles and there is less blood available with which to pull the arms through the water, with the result that they fatigue more easily. I have long advocated a reduced emphasis on the kick, particularly in distance swimming. In recent years world records have been set in the distance events by swimmers with reduced kicks, some of whom kicked as few as two beats per arm cycle.
He concludes this section as follows:
From the fact that the kick is used as a stabilizer and neutralizer, and does not act as a propulsive force in the crawl stroke, it does not follow that less emphasis should be placed on conditioning the legs in workout. The movements of the legs are very important and at times quite vigorous. If they are not conditioned properly, they will fatigue and become less effective in their stabilizing role, thereby allowing hips and legs to drop too low and to move about laterally, creating unwanted resistance. If the kick is mechanically poor and does not move the swimmer effectively while he is on the kick board, it will perform its job less efficiently and may even create additional drag when he is swimming.
I believe that a person should have an efficient kick and that the legs should be conditioned. I also recommend that the swimmer kick while swimming: however I do not believe that the primary function of the kick is propulsion.
Popov and his coach might not altogether agree with Counsilman. I think if you look at modern sprinters, you will agree that the kick is a significant element and must provide some propulsion as well as the stabilizing and balancing effects. I'm not sure if anyone has done similar experiments to those that Counsilman did, but I'd be surprised if they haven't.
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