I have often heard the question, what contributes more to a swimmer’s overall speed, the swimming kick or pull? Of course, the answer depends on the strength and technique of each component, but for most reasonably good swimmers, I would say that the swim kick makes a bigger contribution to overall swim speed than the pull.
How can that be, particularly if one can pull 50 meters in 35 seconds and kick it in 40 seconds? Let’s analyze the two.
First, one must realize that from both the swimming kick and the swim pulling motion, there is a contribution toward propulsion and another toward frontal drag (there is also one toward lift, but we will ignore that for the moment). Even with a very strong kick, few would dispute that the propulsion power is greater from the pulling motion than from the kick. However, when the kick is done properly (tight and fast), the pulling motion is also a much greater contributor to frontal drag, the forces that slow a swimmer down.
The two major factors that determine the amount of frontal drag that is imposed on a swimmer moving through the water are the shape of the object and the speed of the object. Our shape is certainly influenced by our pulling and kicking technique, but let’s assume that we have already figured out that kicking tighter and faster and pulling with a high elbow will reduce frontal drag as much as possible. The only factor really left then is speed and, because of the high density of water, even small increases in speed result in large increases in frontal drag for a given non-streamlined shape, like a swimmer doing freestyle.
When we add the swimming kick to the pull to create the entire swimming motion, the increase in speed (even if slightly greater than our pulling speed) is enough to add significantly to the frontal drag imposed by our pulling motion (mostly from the upper arm). The net effect is that for a reasonably good kicker, the net speed of the swim kick is actually greater than the net speed of the pull, when both are used together.
Let’s look at an example.
I am currently training a swimmer from Ireland, Andy Hunter, who is trying to qualify for the Commonwealth Games in 2014. A few weeks ago, he swam in a 50 meter sprint at Ft. Lauderdale in the same heat as Cesar Cielo. Both were unshaved, but neither swimmer has a lot of body hair. Cesar swam 22.0 and Andy swam 25.7 and finished over 8 meters behind him.
When he got out of the pool, Andy, who is over 30 years old and very strong upper body, asked me, “How can he beat me by 8 meters in a 50 meter race?” Here is how I explained it.
Andy kicks a 50 meters with a board all out in 45 seconds (baseline speed of 1.1 m/sec), while Cesar kicks 50 meters in 30 seconds (baseline speed of 1.66 m/sec). Assuming that in the 50 both swimmers are kicking at maximum speed, when you add the net speed from propulsion and frontal drag of the pull to Cesar’s kick speed, it adds .64 m/sec to reach 2.3 m/sec. For Andy, because his baseline speed is slower, the pull actually contributes more net speed to his overall speed than Cesar, adding .83 m/sec to reach 1.9 m/sec. Even so, his overall speed is about .4 m/sec slower than Cesar’s, all because of the difference in kicking speed. By the time Cesar finishes his 22 seconds of swimming, gaining .4 meters every second, he is now 8.8 meters ahead of Andy. The difference in swimming kick speed is what separated them.
It is no surprise that Andy has been working very hard on his swim kick using kick sets, stretching and dryland/strength sets. As of last month, he had gotten his 50 kick time with a board down to 38 seconds or 1.3 m/sec and not surprisingly, he swam a shaved 50 meter in 23.3 seconds…a huge improvement.
Most coaches and swimmers do not understand nor appreciate how important the swimming kick speed is to the overall swim speed. Nor do they work the legs enough in practice. The legs really don’t get a recovery period during the race and they are moving at 3 times (or arguably 6 times, if one considers the upkick) the rate of the arms. The legs are essentially working constantly, kicking in both directions. The arms get a few important tenths of a second of recovery on each cycle. Relative to the arms, the legs must be much fitter in order to sustain their fast motion throughout the race.
When swimmers or parents ask me what it is that makes Michael Phelps, Ryan Lochte, Missy Franklin or Cesar Cielo so fast, the answer is in their swimming kick. Work your legs in practice and get yourself a faster swim kick and a faster swim.
-Gary Hall Sr.