“Its underwater ripples are unique,” a scientist deciphers

How can we explain Léon Marchand’s exceptional performance on the castings?

His morphology, tall, rather slender – muscular but not too much – is perfectly adapted. It allows him to be hydrodynamic, that is to say to limit the waves. His underwater swimming technique is excellent. This is called undulation. It is practiced in these famous 15 meters of the flow. His great flexibility allows him to undulate enormously. Many swimmers practice undulation from the hips, using very little of the upper body. If you observe Léon Marchand closely, you will notice that he undulates from the head. His back then rounds, then his legs. So much so that he brings back to him the wave that he creates to propel himself.

Is it the mastery of this technique that explains his exceptional comeback during his victory on the wire in the 200 meters butterfly, Wednesday July 31?

In this race, it was during the glides that he gained time on all his opponents. After 150 meters and even beyond, he was second. The last glides allowed him to catch up despite a certain energy fatigue.

One could precisely imagine that it is difficult to produce such an effort at the end of a race…

Except that Léon Marchand is incredibly efficient in anaerobics. That is to say, metabolism, the way in which the body provides energy to the muscles during exercise, without any oxygen supply. When he is underwater and cannot breathe, especially when the effort to be provided is intense, he finds the necessary resources. Last asset to succeed in his glides: he produces very little lactate, as revealed by the small blood samples from the ear when leaving the pool. However, if this acid present in the body is necessary for the proper functioning of the muscles, it can also cause pain and a lack of oxygenation of the tissues. This biological predisposition gives him an extraordinary energy capacity.

Why is casting so important in swimming?

By moving, the swimmer creates a wave that slows him down. This can go towards the bottom of the pool and come back towards him. This is why we prefer deep pools, for example the recommended 3 meters, even if the one at La Défense-Arena is only 2.15 meters. In order to limit the size of the wave, there is a technique, simple in appearance, which consists of swimming underwater, about two or three layers of the body under water. We might be tempted to say to ourselves: why not swim the entire length underwater? Indeed, this would be the best way to break records. But to make competitions more open, the International Swimming Federation decided in 2010 to limit swimming underwater to 15 meters for each length, for each stroke.

Do the sinkings alone explain the fact that he outclasses all his opponents?

No, not entirely. His performances are explained by a champion’s mentality, a perfect swimming technique and a rare level of anaerobics that give him superior abilities to all his opponents. He is an incredibly complete swimmer.

* She is the author of Why do we lean when cornering? Sport explained by science in 40 questions, CNRS Ed., 168p.; €20.