[croes]

>A lot of this is perception vs. reality,” he said. “If you were to talk to many very accomplished coaches, they would say the pool has to be a minimum 3 meters deep. Most of our research shows that anything over 2 meters is frivolous. … Obviously, some depth is very important. But after a certain point, it's diminishing return.

Maybe it's just the swimmers and not the pool as such

[lou1306]

But a lot of the swimmers themselves are not able to go anywhere near their personal bests: this is a sharp reversal from past Olympics, where many athletes reached new personal records.

Plus, they are the worldwide foremost experts on competitive swimming. Definitely I would be more interested in their evaluation of a swimming pool rather than trust "research results" from the company that built the pool in question.

[viraptor]

> they are the worldwide foremost experts on competitive swimming

On swimming, sure. But not fluid dynamics. It's a bit like music listeners shouldn't be treated as experts on music quality, or you'll get the audiophile nuts who need gold connectors. Some combination of personal experience for comfort and objective measurements for performance would be much better.

[dsr_]

It's strange that you would pick on gold connectors. Gold is an excellent conductor and does not corrode in air, so it makes a great plating material. In the quantities needed for plating, it's not too expensive, either.

Silver corrodes relatively quickly and is expensive; that's a bad tradeoff against copper, which is much cheaper and nearly as conductive. So: gold-plated connectors on copper wires are extremely common.

None of that makes an audible difference, as it turns out: humans can't tell the difference between silver, copper, gold, aluminum, or even iron wires at audio frequencies and realistic (sub-kilometer) lengths with comparable resistance. All the advantages are material costs vs longevity without maintenance.

Also, most music listeners are not experts on music quality or sound reproduction quality (two very different things). Many music listeners are experts on their own preferences. Everyone is entitled to their own preferences.

[viraptor]

Picking on it exactly because there's no difference in sound, but the extreme audiophiles will claim they hear it anyway. https://ventiontech.com/products/toslink-to-mini-toslink-opt... - "gold-plated connectors resist corrosion for optimal signal transfer over time." - it's an optical cable!

[mensetmanusman]

There is an audible difference after being in a high temp high humidity environment for 5 years :)

[viraptor]

Audible difference from an OPTICAL cable not corroding at ends? One where the gold plated parts are only the frame that holds it in the socket?

[warkdarrior]

Have you tried not listening to music underwater??

[kergonath]

> It's strange that you would pick on gold connectors. Gold is an excellent conductor and does not corrode in air, so it makes a great plating material. In the quantities needed for plating, it's not too expensive, either.

It’s not strange at all. Gold plating improving quality sounds truthy but is absolutely false. I have yet to read a serious study, at least single blind, showing any meaningful difference. And I have yet to read a serious engineering study showing any meaningful difference in characteristics. Steel plated jacks are just fine, and optical connectors make the whole thing irrelevant. As you write yourself:

> None of that makes an audible difference, as it turns out

> Also, most music listeners are not experts on music quality or sound reproduction quality (two very different things). Many music listeners are experts on their own preferences. Everyone is entitled to their own preferences.

Indeed. But their preference have no effect on Physics. If they are happy to get gold-plated ruthenium cables with diamond coatings, more power to them. It does not make these cables any better.

Theo are entitled to their own preferences, not their own reality.

[SoftTalker]

"I reject your reality and substitute my own!"

[teddyh]

> Gold is an excellent conductor

Actually, gold is a worse conductor than both copper and silver, and only a little better than aluminum.

> and does not corrode in air

This is the real reason for plating contacts in gold. But gold wires would be a bad idea, since they would be worse than both copper and silver wires.

[Gud]

Parent didn’t say gold was a better conductor than silver or copper though. How does gold compare to copper- or silver oxide? Which was the point parent was making.

[teddyh]

The text was unclear; perhaps they did not believe that gold is a superior conductor to copper and silver. But in my experience, many people do think that, and I thought it would be useful to point out that this is not true.

[bluGill]

Parent did say gold was a good conductor which is arguable false.

[ssl-3]

Aluminum is also an excellent conductor.

[SoftTalker]

But also corrodes more than copper, making it unsuitable for household wiring unless special precautions are taken.

[BoringTimesGang]

You're comparing the science of electronics and sound (well understood, rigorous) with sports science (cesspit of low-N, hard to study well). In sports, anecdata are valuable - putting guff in a journal doesn't make it any less guff.

[aleph_minus_one]

> Plus, they are the worldwide foremost experts on competitive swimming. Definitely I would be more interested in their evaluation of a swimming pool rather than trust "research results" from the company that built the pool in question.

But they are very prone to psychological effects.

[mrguyorama]

Professional athletes are MORE superstitious than other people, and are prone to serious amounts of bias in how they attribute outcomes.

[croes]

Maybe they all change their behavior because they know the pool is less deep as they are used to.

Some kind of placebo effect or fear of coming to close to the ground.

Many athletes are superstitious.

[AtlasBarfed]

There's Olympic gold medals on the line.

People are going absolutely as hard as they can.

There's no way an Olympic pool for the actual Olympics should be that shallow. If athletes prefer a deep pool, the pool should be deep.

Swimming is one of the premier sports at Olympics. It's also a facility that has one of the most reuse if built properly.

You don't think a Paris aquatic center wouldn't get tons of reuse in world championships and other types of top end level events if they'd built a fast pool

It's a mystifying decision. Especially since one of the standout athletes on the French Olympic team is a swimmer, and it appears that their decision now cheap out on the pool cost him a world record on the Olympic stage on his home soil

[swores]

Placebo or fear can absolutely be a possibility regardless of how badly they want to do well because it's the Olympics.

Firstly, if a swimmer were to wrongly worry about hitting the floor even if there is 0% that any of their races ever saw them go as low as this floor, it could be in the back of their mind that going as low as they usually do might cause them problems and therefore seem logical to avoid.

Secondly, humans are not perfectly rational machines. Many a football (soccer for any Americans) player has come back from a nasty injury and found themselves unable to play as boldly as they used to, even though the odds of getting injured haven't changed just their perception of it.

I do agree that if the athletes feel it's needed then they should be listened to, just explaining that it's possible for both things to be true, that the depth doesn't create any physical problems yet still lead to changed behaviour from the swimmers.

[RaftPeople]

> Placebo or fear can absolutely be a possibility regardless of how badly they want to do well because it's the Olympics.

But it seems unlikely all swimmers would be impacted equally by psychological effects. Some thrive some wither, lots of variation.

[stingrae]

> It's also a facility that has one of the most reuse if built properly. You don't think a Paris aquatic center wouldn't get tons of reuse in world championships and other types of top end level events if they'd built a fast pool

They didn't build a dedicated aquatic center. "The pool here in suburban Paris — a temporary vessel plopped into a rugby stadium"

[AtlasBarfed]

So you agree they cheaped out?

Paris allegedly spend 1.5 billion to clean up the Seine presumably for fringe events like open water swimming and triathlon.

Again: premier top-of-program sport in Olympics primetime. All they had to do was dig a hole in a rugby field.

[Someone]

> People are going absolutely as hard as they can.

Not necessarily. If they think the pool is slower, they’ll think they will have to swim for a bit longer, and may (possibly subconsciously) adjust their power output to allow for having something left when they have swum for as long as they think it would take them in a fast pool.

[bobthepanda]

In fact a lot of the upcoming olympics specifically don’t have as much new construction because of the white elephant criticisms of the Olympics leading to most developed host candidates declining and/or having hosting referenda rejected.

The Athens 2004 and Rio 2016 venues in particular are not doing very well post-Games.

[bregma]

> There's Olympic gold medals on the line. People are going absolutely as hard as they can.

They don't have to outswim the bear. They just have to outswim the silver medalist.

[duggan]

As much as it's about winning the medals, this is about setting personal and world records, too.

[kergonath]

Regardless, they have to make do with what they have. Nobody is moaning that the weather affects triathlon timings.

[a_c_s]

Right, if you are swimming in multiple events then it doesn't necessarily make sense to swim as hard as you can in the early events if that is going to tire you out for the latter events.

[beAbU]

The pool is a temporary structure, La Defence is a multi purpose venue. The pool is literally a tub on top of a rugby field.

Perhaps this is why its shallower than normal.

[Kon-Peki]

All major competitions will be in temporary pools from now on. It’s a major spectator sport with growing popularity, but as seen in 2008, 2012, 2016, etc purpose-built facilities for that crowd size are failures.

Paris is swimming in a rugby stadium. It is loud and exciting. The US trials this year were in a temporary pool at the NFL stadium in Indianapolis with 60,000 seats filled! LA 2028 has already announced that they will be using a temporary pool in an NFL stadium and will have 38,000 seats. Brisbane 2032 hasn’t said anything as far as I’ve heard, but you can bet that’s also what they will do.

Edit - I was wrong about LA swimming capacity. It is going to be at the NFL stadium in Inglewood, but as of now they are only aiming for 38,000 seats

[aldonius]

> Brisbane 2032

The current plan is a temporary pool in a new inner-city arena (15k seats) for the major swimming events, with diving, artistic swim and water polo prelims at an existing (to be refurbished) sports centre.

[ben7799]

I had read in one of the other articles about this issue that you are correct, that is exactly why the pool is shallower than usual.

The building was going to need structural modifications to make the pool standard depth.

[xhkkffbf]

Experience shows that the pools don't get much reuse. Look at the abandoned venues in Beijing. After all, there's only one world championship each year and dozens of very nice pools already on the planet.

BTW, it's not clear the decision was purely monetary. Raising the water level means ruining the view of the closest seats. The spectators would be that much further away.

[s1artibartfast]

When you measure human performance, placebo matters.

[stonemetal12]

Considering touching the bottom results in disqualification it isn't a superstitious fear.

[echoangle]

Being good at swimming doesn’t mean you can evaluate the pool performance better than everyone else. I trust someone running a CFD analysis of a pool more than a competitive Olympic swimmer when it comes to the effect of pool depth. It’s very hard to make accurate statistical assessments from intuition.

Edit: maybe I’m not making myself clear:

I don’t doubt they are slower in the current pool than they were before. But I doubt they can accurately tell you that it’s because of the pool depth. There are other factors that could also influence the performance, and I’m not sure the swimmers can accurately determine which factor is the primary difference.

[defrost]

Competitive Olympic swimmers in G20 countries aren't always rocket scientists and brain surgeons ... BUT .. thay are frequently coached by teams that include leading sports scientists with degrees in fluid dynamics | applied mathematics | etc.

Australia, as one example, took swimming (and a few other sports) next level with a plethora of studies on all things performance related.

Any theorectical results from, say, CFD, would be parallel tested in real conditions and|or modelled in a scale pool (like a wind tunnel for water).

Those who competed at that level in sport in the larger countries almost certainly heard first hand bleeding edge results from cutting edge sport science.

[Kon-Peki]

The powerhouse swimming nations (USA, China, Australia, Canada, UK, etc) are so far ahead of everyone else it isn't even close anymore.

My niece was not fast enough to be invited to the trials this year (missed by .03 seconds in her favorite event), but her time would have put her into the second heat in Paris. She's the ~150th fastest person in the USA, but would have come in ~25th place in the Olympics. It's the same situation in China, Australia, Canada, UK, etc.

Most countries only have a small handful of elite swimmers. The power nations can each provide 20-50 swimmers fast enough to get to the semi-finals in every single event. They're analyzing and optimizing for everything. This is why most of the elite swimmers not from these countries go and train in the powerhouse countries. And why the powerhouse countries don't care that they do. I'd bet that 90% of all the medal winners this year do their training in 5 countries.

[toast0]

If she's likely to continue to be fast again in 4 years, it might be time to venue shop her team? Have any connection to other countries not in the top? Even if not, 4 years might be enough time to develop a connection. Being 25th in the Olympics is way cooler than being 150th in the USA, even if they're objectively the same speed. Also, you may need to adjust her speed if the Olympics pool is slower than the trials speed; but still it's way cooler to be any place in the Olympics than 150th faster in the USA --- maybe unless you're in the know for swimming.

Venue shopping might feel ick, but I don't think it's too bad if you're in the competitive envelope, as opposed to what's perhaps a tradition of less then competitive entrants in some events.

[TylerE]

Feels like you're missing a variable here. If your nieces time in a fast pool would be 25th in Paris, that means her time in Paris will be slower than that, because now she's in the slow pool, right?

[_heimdall]

You don't necessarily need to do an in depth study of the pool when every Olympic swimmer in it fails to meet their own personal records. A study may be useful to understand why depth still matters beyond the 2m point, but a study isn't needed to show that swimmer performance is impacted.

[thaumasiotes]

> You don't necessarily need to do an in depth study of the pool when every Olympic swimmer in it fails to meet their own personal records.

This is a weird standard. Out of 200 people doing anything, how many do you expect to set a personal record? Say you drive to the grocery store. Are you setting a time record for the trip more than 0.5% of the time?

[Scarblac]

These athletes plan their whole training and fitness regime for years so that they are at their absolute best at this particular day.

Tbh I don't do much of that sort of thing for my grocery store trips at all.

[thaumasiotes]

> These athletes plan their whole training and fitness regime for years so that they are at their absolute best at this particular day.

The only way this could actually happen is if they intentionally sandbag their performance starting several years in advance -- and continuing indefinitely -- which would prevent them from qualifying for the Olympics in the first place. It's not a possibility.

[BoringTimesGang]

The motivation of a commute is not comparable to the motivation of a swimmer in 4th place of a medal event, etc.

[thaumasiotes]

So what? Is the motivation of a swimmer in 2nd place in a non-Olympic event comparable? Is the motivation of a swimmer who wants to work toward the Olympics comparable? Is the motivation of a swimmer trying out for the Olympics comparable?

Every Olympic athlete, with the possible exception of the Jamaican bobsled team, has been equally motivated at dozens or hundreds of officially-measured points in the recent past. Why do we expect personal records at the Olympics?

[echoangle]

Or maybe there’s something else going on? There are a lot of other variables in a pool except depth, no? Maybe water tension, density, viscosity? Someone else mentioned the walls of the pool also influencing the wave properties in the pool. Just noticing the pool being more shallow and people swimming slower doesn’t mean that’s the reason.

[mmmrtl]

Explain to us how water "tension", density, and viscosity are variables that would change? It's just water, and temperature is set at ~25 C. The shape of the pool and gutter setup are the only major factors at play, assuming the filtration system isn't causing major currents.

[echoangle]

It’s not demineralized water though, have you ever added a tiny bit of soap to water and it immediately reduced the surface tension? I’m not saying there’s soap in the water in France obviously, but there’s a lot of other additives that could theoretically affect water properties even with a fixed temperature.

Edit: for example, compare salt and fresh water properties here: https://ittc.info/media/4048/75-02-01-03.pdf#page2

At 25 degrees, fresh water has a Viscosity of 0.000890 Pa⋅s and sea water has 0.000959 Pa⋅s. That’s an 8% difference in viscosity by adding NaCl to water. Is it that strange that there could be a 1% difference in viscosity for example by having different additives in the pool water?

[ff317]

Yeah but it's not just "water", as in plain H2O. All water has different things dissolved or mixed into it. In pools there's commonly several chemicals added to that water: to correct the pH for humans, to sanitize, control corrosion of metal, avoid calcium deposits on other surfaces, etc. It's entirely possible that the additives in the water could be way off of normal and somehow affect things like viscosity or surface tension.

[_heimdall]

Rereading your last comment and I think I just misunderstood it, sorry! I first read it as saying a study would be needed to know if something about the pool was anything them down, but you were still specifically talking about whether the depth is the issue.

[echoangle]

Yes, I think a lot of people misunderstood the point, I’m ESL so maybe i didn’t write it up properly. I was just talking about the effect of pool depth, not doubting that something is different this time.

[freejazz]

So to be clear, you have no idea, you just insist on discounting the experiences of the swimmers because you can?

[_heimdall]

I misread the earlier posts here when I started dow this comment path, but I actually agree with them. There seems great evidence, including the swimmers', experience to say that something about the pool slows them down. It seems less clear that the depth is the issue, it could be something else or a combination of factors related to the pool that cause it.

[boringg]

While part of it may be true. The athletes who spend 1000s of hours can probably intuit something being different.

[echoangle]

The can maybe intuit being slower, but I doubt they can accurately tell you that it’s because of a different pools depth. There are a lot of other variables that could be the reason.

[AnthonBerg]

Do you have links available to any peer-reviewed scientific literature on which you base your theory that – just to make sure we’re on the same page — the theory that it is difficult to the point of impossibility for people to correctly ascertain that the depth and construction of the pool they swim in has no effect on their swimming dynamics, efficiency, and competitive performance?

[echoangle]

Isn’t that the null hypothesis?

I have these data points:

1) The pool is shallower than normal in this Olympic

2) The pool seems to be slower this Olympic

3) swimmers seem to think it’s because the shallower depth

4) people responsible for building the pool say the effect of depth is negligible

5) there are other things that can be different about the pool except depth because the pools aren’t strictly standardized in their properties

My only claim was that point 3 doesn’t tell me a lot because I find it very plausible that you can’t really detect the reason for the slowness just from swimming. I don’t have positive proof of that though.

[fullspectrumdev]

I was always told that CFD is not a substitute for “actually going and testing”.

It will get you a fair amount of the way there, but at some point you have to go and actually do the thing to validate your model.

[sdwr]

I trust someone who's life is getting that 2/10 of a second to know when the 2/10 of a second is impeded.

The how can be argued

[CoastalCoder]

Even CFD analysis is a model though, with all that implies.

Would a large, blind empirical study be more trustworthy?

[Eddy_Viscosity2]

Yes and no. The empirical study could identify correlations and the strength of those correlations, but does nothing to say why they are correlated (maybe just spurious). But a CFD analysis may give you insight into what may be happening to cause the issue, which can then lead to a hypothesis that can then be tested further. All models are wrong, but some are useful.

[echoangle]

Only if the depth is the only variable that’s changed. You can’t just use two entirely different pools at different times and locations and conclude that the depth is the reason for different performance.

[lou1306]

Sure, it is not necessarily the pool depth. But that is almost surely the one factor that deviates the most from the "average". Paris is 50-100m above sea level which is pretty unremarkable gravity- and pressure- wise. Its water is unlikely to be macroscopically different from that of other French or Western European cities.

I am aware the above may be proportionality bias, but at the same time there is some kind of "reverse proportionality bias" at play here: the assumption that since the effect of a shallow pool are too small, they can't significantly affect the athletes. Human behaviours are very nonlinear, and even very small sensory inputs may very well "throw off" an experienced swimmer.

[tanewishly]

A CFD analysis is based on a model - an abstraction of reality. If the CFD analysis found everything is okay, yet reality shows it isn't, I wouldn't trust the competency of the person behind the analysis.

[echoangle]

But CFD didn’t say that everything is ok, it said that pool depth has a very small effect. So either CFD is wrong or something else is wrong with the pool that’s not depth.

[MrPatan]

Intuition forms because it works. When it doesn't it's remarkable to the point of writing books and movies about it.

[echoangle]

Intuition is a heuristic that lets you form decisions fast without a lot of effort. But I wouldn’t say having a wrong intuition is that uncommon that I would write a book every time I had a wrong intuition. I have intuitions all the time about stuff and when I check, it turns out I was wrong. That’s also why I wouldn’t make important decisions based purely on intuition. Intuitions form because sometimes, you need quick decisions and it’s better to do something wrong some of the time than take longer to make a better decision.

[Rayhem]

When it works we call it intuition. When it doesn't we call it superstition. There are all sorts of availability biases at work here; none of which really support the use of intuition as a valuable, predictive resource. After all, if your intuition fails to predict something, there must be some lurking variable somewhere that you failed to account for. Not that the intuition is wrong /s.

[djtango]

The thing is, depth discussions have been going on for decades and these swimmers literally live in the pool. When people spend literally 40+ hours a week in water I trust them well before I trust scientists because it takes scientists so much longer to catch up and measure what the practitioners are observing.

Like this reminds me of Beckham/Ronaldo doing free kicks. They had a deep understanding of controlling the ball well beyond what scientists knew how to measure and explain what they're doing.

[Xcelerate]

I trust the swimmers’ intuition far more than an ad-hoc CFD analysis. Plus the shape of the pool itself isn’t necessarily the only variable that might be affecting the race times.

The gold standard would be an empirical randomized controlled trial to compare two pools, assuming you could hide “which pool” from the participants.

[echoangle]

I don’t doubt that they are slower, I doubt that it’s the pool depth. To be more accurate, i have no idea if it the pool depth, but a swimmer saying that it is doesn’t tell me a lot. I’m not sure if the intuition of a swimmer can differentiate between the pool depth effect and other effects that could influence performance. I don’t doubt that something is making them slower, but i don’t believe it’s pool depth until there’s better evidence.

[djtango]

It's pretty amazing that people here are willing to wade into a field and contest what is accepted amongst practitioners. Olympians literally spend around 40 hours a week in the pool if not more. Places like team USA and other well funded teams have an army of coaches and scientists trying to eke out every basis point of performance as their full-time job.

As a swimmer, I remember everyone lauding over how cool the Beijing Water Cube was because it was a uniform 3m deep which made it excellent for racing in - this was 16 years ago in 2008.

Since the Paris Olympics were accepted the regulation recommendation for pool depth has been revised from 2m to 2.5m

So clearly people vested in the sport and live and breathe it have seen enough evidence (including the sleepy regulatory board) to advise deeper pools.

If you wanted another possible explanation for how depth may affect the swim - a crucial part of the swim is the dive and also the underwater kicking. Both of those may have separate dynamics to swimming on the surface.

[Scarblac]

Wouldn't they notice the extra turbulence affecting their legs?

[echoangle]

Looks like they don’t if you look at the quotes in the article. Nobody said “I can feel the turbulence reflected from the bottom of the pool slowing me down”, they just said they notice they are slower and the article claims they think it might be depth-related.

[derbOac]

At the end of the article it notes thqt quote is coming from the company who built the pool.

On some swimming forums competitors were complaining about the bidding process for the pool construction and giving a different opinion, noting that the depth is less than what was recommended by international standards bodies. There's also something about video equipment at the bottom of the pool?

I'm not sure what to think, as there are things to consider both ways, but there's a bit more out there than swimmers versus pool officials.

[ianburrell]

The Olympic swimming is held in temporary pools in an indoor arena. Temporary pools explain the shallow depth and high walls. It isn't construction problem but decision to not use permanent pool.

Temporary pools seem to be thing recently. The US trials were held in one.

[SoftTalker]

You can set up a temporary pool in a huge venue such as a football stadium and get higher attendance, or stated differently, you can accomodate a one-time need for that much spectator capacity for an event like the Olympics when you will never need that again in the lifetime of the facility.

[toast0]

Maybe not the same level of attendance, but you can build a permanent pool with temporary stands for the Olympics, and use the larger than necessary deck in other ways after the Olympics.

[qzw]

Notice the “most of…” and “diminishing returns”. The vagueness is doing a lot of heavy lifting in that statement. Since world records are often broken by mere tenths or hundredths of a second, I would think that an Olympic games would err on the side of extra spending for exactly those diminishing returns. The excitement and extra viewership from having many new WRs would more than offset the added cost anyway.

[Xcelerate]

I doubt that. What is P(set of slower times across swimmers | pool is not slower)? Seems like it wouldn’t be too hard to calculate if we make a few reasonable assumptions about observational data.

And if you don’t like inferring causation, one could just directly perform an experiment to test this pool vs another pool using swimmers who didn’t quite make the Olympics.

[etempleton]

There are more things that influence if a pool is fast or slow than just the depth.

How the pool gutters neutralizes or doesn’t neutralize waves; water temperature; the design of the lane lines; design of the starting block; the electronic touch sensors(how hard are they - do you get a good solid feel for push off?); etc

Depth is probably only part of the reason the pool is slow. It would be very unlikely everyone happens to be slow at the Olympics this year.

[rscho]

Perception is everything. If the pool 'feels fast', you'll feel like you're on your way to your best, which is a huge boost to your motivation. The converse is also true.

[roughly]

I mean, "diminishing effects" - these folks are the absolute apex of swimming struggling for the absolute maximum speed in the water that any person has ever achieved (under the watchful eye of someone with a stopwatch, at least). Small effects don't matter unless you're going for a world record, and then they might.