Posts tagged: phelps vs. cavic

How to swim faster and still loose a butterfly race?

There are (at least) 4 reasons why somebody could loose a butterfly race in spite of swimming faster.

1. Butterfly has a specific velocity pattern. It suggests that horizontal velocity of the center of mass of a professional swimmer can vary from 1.5m/s to 2.2m/s, depending on the phase of the stroke. Have a look at the excerpt from “Swimming Fastest” book by Ernest W. Maglischo below:

What it practically means is that the center of mass of one swimmer swimming next to another one with the same speed but totally opposite phase could go forward and backwards relative to other swimmer’s center of mass by as much as 13cm.

In the chart above, blue and red lines show velocities of two swimmers in totally opposite phases of butterfly stroke. They are simplified as sine lines. Velocities are read on the left axis. Green line shows relative distance between these two swimmers. In the beginning, blue swimmer is 13cm behind the red one (read on the right vertical axis). Half way through the stroke, blue swimmer overtakes and gets into lead by 13cm. By the end of the full cycle, red swimmer is again in the lead by 13cm and so on.

So, if the timing devices were so sophisticated that swimmers could literally swim through the finish line (like runners do) and device would be able to detect when center of mass crosses the line, it would still be great portion of luck involved in all this. Unfortunate phase of the stroke could cost a swimmer around 7 hundredths of a second compared to the perfect timing case. I translated 13.4cm from the graph above to 7/100s by assuming average speed to be around 2m/s during the race.

2. There is no perfect timing device that I mentioned in previous point. Swimmers must touch the finish wall with both of their hands. On top of velocity pattern, swimmers are facing another “disturbance”. If they finish the arm stroke too close to the wall, they don’t have time/space to do another one, so they have to glide through the water. Gliding is decelerating, meaning velocity becomes slower and slower. It means that the swimmer who is behind but is lucky to finish his arm stroke far enough from the wall could have enough time for the last stroke, while the leading one could be maybe too close to the wall for another stoke and all this gives enormous advantage to the second swimmer to overtake the leading one who would be gliding to the finish wall.

Let’s assume that there is a distance from the finish wall that defines whether a swimmer will go for the last stroke or not. If a swimmer finishes the recovery after this point, he/she goes into gliding. Otherwise, a swimmer goes for another stroke. Let’s consider a limit case where blue swimmer is just little bit after this point and continues in gliding, while the red one is just a little bit before this point and goes for another stroke.

Since I have no idea how strong deceleration is during gliding through the water, I assumed that the speed will remain constant. This assumption will make the difference even smaller than in reality. From the diagram above, we can conclude that the red swimmer, who had a chance for another stroke, finished the race 36cm in front of blue swimmer. Since the blue swimmer was gliding at 1.5m/s towards the wall, it would take him additional 25 hundredths of a second to finish the race.

3. That’s not all. Rule says that swimmer must touch the wall with both hands simultaneously. In other words, swimmer must be touching the wall with both hands in order to be considered finishing the race. But no device today can detect if the swimmer touched the wall with only one or both hands. Basically, first hand that touches the wall will stop the clock. Have you ever tried to measure how taller you are with one hand raised up compared to both hands next to each other. Try to stand by the wall, facing it, with both arms raised up next to each other. Let someone stick the tape just above your fingers. Then keeping both arms straight up, lean your shoulders in order to make one arm “longer”. Again, let someone stick the tape just above the fingers of the “longer” arm. I managed to make 4cm difference. And I’m quite small compared to professional butterfliers. They definitely have broader shoulders, so they should be able to make even more difference. But even my 4cm of difference would mean at least 2 hundredths of a second difference. And nobody’s eye is capable of noticing one arm touching 2/100s before the other one.

4. And last point, the pads at the moment cannot detect touch of a hand unless there is certain pressure exerted by the hand on the pad. It means that there is a lag between the actual (optical) touch and mechanical detection of that touch. In 100m final butterfly in Beijing Olympics, Cavic touched the wall first (according to an Omega person), but Phelps won by 1/100s. So, pad itself could make a difference of at least 1/100s and maybe even more.

In conclusion, what’s the point in timing butterfly swimming races with precision of 1/100s when all four points above could make much more difference. I remember one technician of Omega saying that they can’t make measuring in 1/1000s because it’s difficult to make a pool to be of perfect length, but this statement goes into perspective compared to all four points above.

In recent race in London, 200m butterfly, Phelps lost to Le Clos by 5/100s although he was leading all the time. He was just so badly affected by points 1 and 2 that he lost an obvious advantage and a chance to win 3rd consecutive Olympic gold in this discipline.

But 4 years before that, in Beijing Olympics in 2008, Cavic “lost” to Phelps by 1/100s in the final race of 100m butterfly. Cavic lost some time due to unfortunate stroke phase (points 1 and 2), he had to do a long glide to the wall, while Phelps had time for one more stroke. But that didn’t cost Cavic gold medal. Phelps touched the wall much earlier with his right hand (spot bent fingers on his right hand and stretched ones on his left hand), which is against the official FINA rules and could bring significant advantage (point 3 above). Asymmetry of Phelps’ last stroke is quite obvious in the following two photos of Associated Press (link to Baltimoresun blog): Photo 1, Photo 2.

But that was not enough to beat Cavic neither. Cavic “lost” at the end because even the 4th point was “against” him. An Omega person admitted a year after the race (follow the link above) that Cavic did touch first, but with the smaller pressure (since he was gliding) than Phelps (who had enough time for the last stroke) who swam into the wall in full speed and although touching the first, it took more time for Cavic to exert minimum pressure to the pad in order to stop the clock. What an “unfortunate sequence of events” for Milorad Cavic.

Timing in butterfly is at the moment very far from perfect. Maybe in future, somebody will come up with a better solution than today’s mechanical pads. Until then, we will unfortunately watch many races where slower swimmers will beat the faster ones.

Update 21/04/2015: Couple of days ago, Mark Spitz, in his interview to Express Sports UK, shed more light on above discussed Beijing 2008 100m butterfly final race.

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