Current in the Pool: A Contrarian Brings Some Rationality to the Discussion

This weekend, in conjunction with the Counsilman Center of Swimming Performance (a group that falls under the auspices of the department of public health, rather than engineering or statistical measurement) has issued several statements through the website calling into question what they believe to be a “flaw” or a “current” in the pool at the World Championships.

In their opinion, the fact that 17 out of 24 medalists in the 50 meter races came from lanes 5-through-8 is a statistical indication of some sort of devious back-draft in the pool, and have even gone so far as to call upon FINA to consider changing results.

While we await the Counsilman Center’s full report, we sit and pray that they find better information than that which they’ve provided. While we don’t have the backing of Indiana University here at SwimSwam, we have taken plenty of statistics classes, certainly enough to conquer this basic math, and enough to see even bigger flaws in the accusations than the supposed ‘flaws’ in the pool.

Let’s look at the claims, and discuss why they’re, in a word, terrible:

1. Thus, over the long haul, there should be more medals in lanes 1-4 than lanes 5 -8. But, in the finals of all of the 50s, if you look at the number of medals won by lanes 1-4 and 5-8 in the 4 individual 50 events, lanes 1-4 won only 7 medals and 5-8 won 17 medals. That’s a really big difference, especially because based on seed times as stated, you’d actually always expect more medals in lanes 1-4. 

Point one: this is nowhere near ‘over the longhaul’. The researchers are taking a sample size of 24: 8 50’s x 3 medals. Their theory is that 50’s are all that is relevant, because swimmers are only going in one direction (in other words, either with or against a current). That 24 in-and-of-itself is a tiny sample size, but even the proposal of a sample size of 24 is inflated. The sample size here is 8. 8 races. While this may be enough to notice a funny trend, remember that 3 medals per race is a human-initiated arbitrary award.

2. Were the results unexpected?

Out of those same 24 medals, 18 were won by the top four seeds coming out of the semifinals (specifically, lanes 3, 4, 5, and 6). Just because more of those were lane 6 and lane 5, are we to declare this a bias in the results? Lane 4 medaled in 6 of the 8 races, as one would expect in a final, so to even call the bias a “lane 1-4 bias” would be wrong.

3. Seed times are being used as a control.

The whole ‘flaw’ is based on the researcher’s expectation that seed times in the final should dictate the ‘expectations’ of placement in the final. To some extent, this is true. As noted above, the middle lanes, who were the fastest in the semi-finals, are expected to win most of the medals. But we’re really splitting hairs to say that lane 4 is a favorite over lane 5, lane 3 over lane 6, lane 2 over lane 7, and lane 1 over lane 8. Consider that those swimmers weren’t always in the same semi-finals, which means that they weren’t racing head-to-head under identical circumstances to earn those seeds.

Then consider how small of a separation in seeds we’re getting for these swims. In the men’s 50 back, lane 4 had a .06 second seed advantage over lane 5; same with 3 over 6; lane 2 over 7 had a .11 second seed advantage, and lane 1 and lane 8 had identical seed advantages. So now, we’re using the tightest-packed and most unpredictable races, the 50’s, to make sweeping trends about currents? I think not. We already know that seed times coming into a meet have little impact on actual outcome of the races, thanks to our pick ’em contest results.

4. “When you go back and do the same thing for the World Championships for 2009, lanes 1-4 won 15 medals and lanes 5-8 won 9. This is as it should be. When you do that for 2011, lanes 1-4 won 13 medals and lanes 5-8 won 11. Both of these events were run permanent pools, not temporary pools.”

Yeah, so now your sample size is two, even smaller than the 8. Look at the semi-finals. In the women’s 50 backstroke, the top four seeds from each semi-final made it to the final. Exactly as expected. In fact, 29 out of 48 swimmers who made the finals swam semi-finals were in lanes 1-4: which based on the methodology being used where seed times are the control is much more than the expectation (which should be half-and-half).

And, if you want to take the really obvious route, we’ll go back to 2007. There, 11 out of 24 medalists came from lanes 5-8. In 2005, 8 out of 24 medalists were from lanes 5-8. In 2003, it was 10 out of 24. In 2001, the first year of 50’s it was 12 out of 24.

So there, in a sample size of 136 races, by far the biggest of any proposed yet in this ‘whodunnit,’ any statistician worth his pay could come to a conclusion as to how 2013 fits into the trend: he would find that with this sample size, there’s no trend whatsoever. In list form:

Medals won by lanes 5-8:

2001: 12
2003: 10
2005: 8
2007: 11
2009: 9
2011: 11
2013: 17

See a trend there? Neither do we.

That’s because of the ‘human factor’. Statistics are applied best when done to random samples. Swimming races are not random samples. To find any sort of usable trend in a non-random event means an even huger sample size is needed to gain any credibility.

And lest we be too elementary, we’ll point out the ‘correlation-causation’ clause to anything.

Simply put, this is not something that can be declared with statistics. It is a test case for engineering. Of course, many times statistics help engineers know where to start looking, so there’s no problem with looking at statistics. But when statistics, especially such flawed ones, are concluded with a call to change the results of a World Championship, that’s when it becomes a problem.

If FINA is curious, it would become a relatively easy problem to test, and even if there was a small current found, these numbers wouldn’t prove it had any affect on medals, but until an engineer becomes involved, this is nothing more than a curiosity.

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10 years ago

The 50-meter races are always, always unpredictable. Florent Manaudou winning the 50 free in London — what were the odds on that outcome, again? Honestly, prior to the 2012 Olympics, how many of us were even aware of the fact that Laure Manaudou has a brother who swims? Exactly.

Swimming is an unpredictable sport, plain and simple. To call world championship results into question based on an odd little fluke in the 50-meter races is ridiculous. Should FINA look into the possibility of currents in temporary pools? Of course. But an observed “bias” in the results of the most unpredictable races in swimming is not enough to prove anything.

Reply to  kdub425
10 years ago

unless, of course, that bias makes these unpredictable races rather predictable.

Reply to  kdub425
10 years ago

The main reason to call the results into the question doesn’t come from the 50s, it comes from the 1500s.

Also, I wouldn’t put bias in quotes. And +1 to Robo Richard Simmons

Reply to  kdub425
10 years ago

If credible technicians would simply measure the current in the places I’ve stated early in the thread, then we’d have data to back up any claims. Even a small current about 0.50 inch per second running against a sprinter would add about 0.10 sec of time. That’s significant for a 50, but not so significant for other races where the times would off-set as you go from going against the current to going with the current.

10 years ago

Would it be worthwhile to compare the 1500 times to what the swimmers went at their qualifying meets? This would compare the same swimmers, probably using the same strategies, at the same point in training.

Just a thought.

10 years ago

Current effects can be significant. A current of just 1 inch per second (0.0254 meters/sec) flowing in the opposite direction of an elite swimmer doing a 50M freestyle would add approx +0.20 sec to the time.

10 years ago

I remember thinking after watching the men’s 50 free that it was odd that lanes 6-8 went 1-3; I had never seen that in a race at that level. But of course one can’t draw general conclusions from a single race. The data and analysis in the Councilman report are very convincing, however. The fact that this anomalous statistical deviations were not seen in prior world championships makes their conclusions very strong.

10 years ago

The full report can be found in the above link.

The term “current” was used by the athlete requesting help. Because of that, and the other reports that had surfaced using the same term, we continued calling it a “current”.

More importantly, the beauty of statistics is that even with a small sample size, significance is significance. Now we used our collective experience as scientists and swimmers, which everyone in this lab is, and thought the most probable cause was that a current-like scenario occurred. Rather than dwelling on semantics, I think we can all agree it is more important to take proper precautions in preventing future occurrences.

Reply to  Ben
10 years ago

Thanks for posting! Very well written paper.

10 years ago

Correction: in 2007 lanes 5-8 won 11/24 medals, not 13/24.

10 years ago

You guys should check the pool in Montreal before it starts tonight.

Dan O
10 years ago

The idea of a “trend” is ridiculous. But looking back at prior WCs is useful because the pools were different.

How about someone producing a diagram of very water intake and outlet in this pool? Was this Myrtha pool built differently from other Myrtha LCM pools?

Reply to  Dan O
10 years ago

Yeah prior WCs are also a great sanity check. Here’re the average deltas/stdevs by year across ALL 800s/1500s, men and women included (just lanes 0,1,8,9 in parens)

2009: 0.01s +/- 0.316 (-0.02 +/- 0.332)
2010 PanPacs: 0.01 +/- 0.296 (0.07 +/- 0.259)
2011: -0.004s +/- 0.303 (-0.01 +/- 0.287)
2013: 0.27 +/- 0.313 (0.399 +/- 0.311)

So we expect ~0, and we get ~0 for ’09, ’10, and ’11. We also expect the end lanes to have the same distribution as all lanes, and we get that too. But now, we get significantly non-zero in general and even more non-zero on the end lanes.

Can’t help you on the diagram though, hope somebody else can.

About Braden Keith

Braden Keith

Braden Keith is the Editor-in-Chief and a co-founder/co-owner of He first got his feet wet by building The Swimmers' Circle beginning in January 2010, and now comes to SwimSwam to use that experience and help build a new leader in the sport of swimming. Aside from his life on the InterWet, …

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