mercredi 9 janvier 2013

Why did Janet Evans move her head so much ?

(The French version of this post is here)

All swimming lovers probably remember the so distinctive nod of Janet Evans's head.  

Rather than keeping her head well into the wave (as we all learn during swimming classes), Janet used to move her head up and down and pulled her head outside of the water continuously at each inhalation. 

One might think that it was a flaw, even though it did not prevent her from dominating the 800m freestyle for so many years.

If we look at her head movement and especially if we consider the precise timing of her head motion during the stroke cycle, we must say that it was not a flaw but rather an excellent technique that made her a even faster swimmer. It is interesting to notice that her successor at the London Olympics, the 15-year old US swimmer Katie Ledecky, has a very similar head motion. 

In fact, all this has to do with the timing of the inhalation during the stroke cycle. In theory, the best time for the inhalation is when the upper body finishes to roll up above the water, because in this case, the mouth is placed slightly above the water. 

The downside is that, at this moment:
- The underwater arm is already fairly low under the water,
- For most swimmers, a space between the shoulder and the head opens,
- to position the underwater arm in the correct manner is more difficult because of the position of the swimmer, which is rather unbalanced at that time: indeed, the swimmer is trying both to finish to roll, to inhale and to press hard with his arm: this makes a whole lot of things to do at the same time while keeping good balance. This is the reason why this phase of the cycle is often the most difficult to perform well. Many swimmers encounter serious technical and coordination difficulties during that phase and therefore lose a lot of speed.

One way to circumvene this difficulty is to inhale very early during the arm cycle, even before the roll is completed. And to achieve this, the swimmer needs to pull his head ahead of the water, like Janet!  

To end the inhalation before the underwater arm starts to catch can greatly simplify the coordination of the underwater arm and allow the swimmer to stay longer in a more shaped and hydrodynamic position.

Let see that :

Katie Ledecky (800m JO 2012) 
Katie's head pulls out of the water while her front hand is not even in the water:

Katie inhales while her hand is entering the water :

Katie finishes inhaling while her back arm just exits the water ; as she practices a shoulder driven freestyle, her front hand is still in the first quadrant under the water :

This is also obvious underwater : her head exits the water as her front hand just enters the water :

Katie finishes inhaling while her hand is in the front quadrant under water :

Janet Evans (800m JO Barcelona 1992)

For Janet, it is basically the same: her head is out of the water, while her hand enters the water :

Janet inhales at the very beginning of the catch:

Janet is more body driven. Kathie is more shoulder driven. In the case of hip driven freestyle, it is also useful to inhale early if you want to swim fast. Though since the arm tends to remain a bit longer in front of the swimmer, he has a bit more time to inhale and can keep his head lower. 

In conclusion, what looks like at first sight a flaw is - as of matter of fact - a rather excellent technique to swim fast for competitive swimmers

Happy laps!

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