Ban the Nike Vaporfly & other carbon fiber devices for future performance credibility

21 Mar 2017 Posted by

So having suggested an increase in the frequency of short “thought crossed my mind” posts the other day, this is a longer one(!), on the Nike Vaporfly Elite shoe that will be worn in Nike’s Breaking 2 attempt (and which has been worn by numerous runners before, too).

The article originated with an email exchange I had with someone who knows the shoe, and who got me thinking about the concepts, which I’ve expanded on over the last couple of weeks.  Basically, I think there are two historical cases in play: The Pistorius advantage, which draws a direct line to this, and the Speedo LZR Racer swimsuit and subsequent suits, which illustrate a couple of conceptual issues.

To sum my position up, I think the addition of any device that purports to act as a spring (and the Vaporfly Elite clearly has this) should be banned for the credibility of performances both now and into the future.  Here are my (amended) thoughts in response to the email discussion

Question on your shoe take: nearly every top end track spike has carbon fiber or some similar element to stiffen the shoe and has for some time. Should these be banned as well? What about spikes with plastic structures?

The carbon fiber plate is getting a lot of attention, but my understanding is that the real “spring” quality comes from the foam. The plate is more for smoothness of foot transfer (a la track spikes).

I’m not trying to ask ‘gotcha’ questions but rather flesh out your stance.

Hey. No problem.

My position would be that any device inserted into the shoe, and which purports to add to energy return or elastic recoil or stiffness should be banned.  That means the carbon fiber plate, or plastic etc but not necessarily the gels/air patches that offer cushioning, and not the foam, either.  Since Kram raised it on Twitter, I also don’t think that orthotics meet that standard to be banned.  I’m talking specifically about a device that is there to ‘spring’ by offering elastic recoil, and that’s what a carbon fiber plate is doing when it’s curved in the way that this particular one is.

There’s been some semantic ‘tap-dancing’ around this from Nike and a few journalists carrying that message, but I’ve no doubt this was intended to work like a spring.  People just need to get the pogo stick image out of their minds, because a spring does not have to work like that.

As for the foam, of course it contributes some energy return, but I’d be hard-pressed to believe that it’s the main source of the energy return, rather than the carbon fiber plate, curved as it is.

The article written by a patent lawyer that I linked to yesterday made abundantly clear that a patent application dating back last year was for a ‘spring’ – Nike were specific about what they were applying for then.  The first clue was in the name – they called it, literally, a “spring plate”.  Next, their own words in that patent document:

“In conventional footwear, little or none of this mechanical energy is recovered to contribute back to ongoing movement. Reducing this energy expenditure and/or improving the energy recovery can potentially improve locomotion efficiency …”

Note the “little to none of this mechanical energy” bit – that tells you that conventional midsoles/foam don’t return energy.  The carbon fiber insert is the solution to the problem.

Now, I’m told that this version of the shoe has a different carbon fiber plate in it, and that it is not curved for its spring-properties.  Instead, it is designed to unload the calves in the face of increased stiffness from the plate.  That may be another benefit, and the testimony of a few athletes does suggest that the Vaporfly achieves this, because they say they don’t experience anything like the local muscle fatigue and pain at the end of, or after, long runs.

This may well be true, but I think is intriguing mainly as the mechanism by which a spring would reduce the O2 cost (by unloading the muscle-tendon), as is purported to happen.  If I were assessing the shoe, I’d measure O2 cost and muscle activation simultaneously, with the hypothesis that posterior calf muscle activation will be lower because the spring in the shoe is doing the energy recovery and propulsion, rather than muscles.

Whether this carbon fiber plate is functionally different to that applied for in the patent, one has to take at face value for now. I find it difficult to believe that a previous focus on energy recovery and locomotion efficiency using a curved spring plate was set aside to create a curved spring plate that didn’t do the very same thing.  So to me, it’s pretty clear what the Vaporfly Elite’s curved plate has the capacity to do.  It’s also clear if you understand how the Pistorius case led, in a direct line, to this point, but more on that below.


Regulation without precision in measurement

One of the core problems in this whole thing is that I can’t see a way to regulate a line that divides any device from being there just for some stiffness or smoothness of foot transfer, or being there to make a (possibly) large contribution to energy return, like Nike are claiming in that application. In other words, at what point would that device become “too effective” as a spring?

I don’t think anyone can answer that question clearly, because the instruments we have are too blunt, and the outcomes (economy, performance) are too complex for them.  It’s thus impossible to give a value in response to the question “How large is the advantage?”.  All we know is that a) there is theoretical reason to believe the advantage exists, and b) it might be significant.

In the case of the Nike Vaporfly, we know both those things only because Nike have said so, which may be marketing, but I think a theoretical basis needs to be acknowledged, because a spring made in this way would provide an advantage.

That takes us back to Oscar Pistorius, who gives us a conceptual illustration of the problem – the technology that allowed him to run 45.3s in 2012 was viewed as “fine, tolerable”, because:

a) the research couldn’t cleanly provide an answer to the question “Is this a nett advantage?”, and

b) let’s face reality, he wasn’t “too fast”.

Had Pistorius been running sub-44s, I dare say the interpretation of the research that DID exist would have been quite different.  So the first potential problem in that situation was that a better athlete comes along, and with the same technology might run 43.3s, or even faster.

Then you’d be scrambling to ban the technology, and it would very obviously be because he was too fast, and that’s all kinds of discriminatory.  So in my opinion, if you can’t eliminate this as a possible future outcome because the magnitude of the advantage can’t be quantified with precision, then I think the technology should be banned presently.

The same is true for these shoes, though to a much lesser extent, mainly because the frequency of elite runners with access and opportunity is much higher, so we’re far less likely to be shocked by a new athlete.


Technological advances and credibility

However, the second possibility is technological improvement.

Any future improvement of 1% to those carbon fiber prosthetics would’ve made Pistorius an Olympic finalist, and 2% makes him an Olympic champion, entirely thanks to technology.  How do you legislate against that when you can’t measure the influence that a lab-measured variable (say, energy loss) has on the actual performance to begin with?

It becomes a problem only when it becomes too obvious, but it’s not too obvious until it’s too late!  And thus cutting that technological progression off at the outset is important.  Applying the same model to competitive situations, how do you know that Athlete X is not beating Y because of that small (or large) advance in tech?  You can’t, but it’s happening already – Kara Goucher verbalized this very well in an interview published yesterday.

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So let’s say you have Prototype X – it is worth a small amount, so people say fine, it’s legal, it’s just a carbon fiber plate and some foam, nothing new, there’s all kinds of justification going on. Nobody really knows how much it will improve performance, there are some theories, disputed/unproven, about 1%, and so on.  It can’t be measured, but the effect is not clearly obvious and ridiculous, so you let it go.  File it under “Progress”.

Then you mess about with the curve of that spring plate, maybe the material or its integration into the midsole when you design Prototype Y. It works a little better than in X.  Now it’s 2% to 3% better.  All this is happening behind closed doors, top secret.

Then you move on to Z, curved, optimized, and it REALLY works.  4%.  You name the shoe accordingly. Suddenly prototype Z has knocked 90s off a half marathon time, 3 minutes off a marathon, and nobody knows whether they’re watching a special human performance from a great athlete, or whether they’re seeing engineering at work like in Formula 1.

Meanwhile, and this is even more critical at the elite level, nobody knows whether they’re watching something fundamentally unfair because only one athlete has Prototype Z and the rest are now relegated to inevitable defeat by ‘technological exclusion’.

An athlete finishes fourth at the Olympic Trials, an Olympic dream is over, and the margin was attributable to a shoe only one of them had.  Or a medal is decided by the same.

That to me is the situation that should be avoided, and the biomechanics are too complex to assess with certainty in the margins we’re talking, which is I why I’m saying any external device inserted for the purpose of energy return should be banned, and I think this regardless of whether that device is rigorously proven to work or not (because proof is going to be impossible in the absence of a stupid performance leap).

I’m also reliably informed that they’re trying to curve the carbon fiber uniquely for each of the three runners, given their footstrike and take off angle, and maybe some other biomechanical variables, because they’re searching for the perfect curve that propels the runner forward on take-off.  This possibility is mentioned in the patent application too.

What does that tell you?  I think it is crucial.  In the Pistorius blades, this was called something like Active tibial translation (my memory is hazy on the exact name) – the shape of the blade was such that you’d compress it on landing and it would return that energy horizontally as your mass moved over it.  A slingshot effect.  Turning compression into “forward displacement”.  That’s a spring, however you skin it, and while it’s much harder to achieve in an insole, it’s what this shoe is doing.

So I don’t think it’s just the foam, but you’re right that it’s not just the carbon fiber at issue. I think the former (foam) should be regulated for a physical property, and the carbon fiber plate should be banned. And that’s in all shoes, now and in future, and should’ve been in the past.

So the ‘conservative’ way (which is something I’m not usually, but am on this) is to say “No X, Y, Z allowed”, and then you ‘ll never have to resolve these potentially unsolvable problems.

I think all that’s fair. Although some of this depends on how rapid tech can advance, no? My understanding of what did the LZR suits in wasn’t that they were better than the old suits but that they kept getting better all the time. Perhaps that’s misremembered but it seems to me that a one time equilibrium shift (cinder to synthetic tracks, say) after which it’s all just tinkering again can be accounted for. It’s when you get into the arms race territory and the ground is constantly shifting that everyone gets a bit queasy.

This conservative route does involve a lot of turning back the clock though. Every middle distance spike since I have been an athlete has some sort of ‘artificial’ stiffness to it. Nike, at least, has been putting carbon fiber ‘shanks’ in theirs for 8 years or so, but the plastic has been there forever.

Thanks for sharing your thinking!

Yeah, I appreciate that. I am not too fussed by the track vs road difference – I see it in much the same way that track bicycles are different to road bicycles (less now than say 20 years ago when the space race basically entered track cycling, another relevant historical precedent for this discussion), in terms of things like gears, no breaks, wheels etc.

But I appreciate that not everyone might agree, so I take your point, and I can’t stand here and say there’s a specific reason to disagree. I just feel track and road can be viewed separately without a problem.

The swimsuit issue is interesting, and really important to think about as a concept in order to provide context on this one.

I covered the swimsuits closely at the time, it was a fascinating debate. What happened was a major win for Speedo, because they launched that suit before the Beijing Games, too close for anyone else to match them, but long enough for it to be clear that and obvious right away that it was so effective that if you didn’t have it, you were at a huge disadvantage.

So the size of the effect mattered a great deal in this instance – that suit, the LZR was not conceptually different to suits since about 2000 when Ian Thorpe swam in a full suit.  Since 2000, a number of suits had developed the technology, reducing drag, making speeds faster (swimming is ripe for this influence, for reasons not worth going into here, but which I’ve written on before).

Anyway, the LZR did it better.  Much better.  It had the polyurethane panels, the corset design, ultra-sonically bonded panels (so no seams). I honestly couldn’t tell anyone how much each of these various devices each made, I don’t know whether anybody could, but the effect of all the changes was profound.

The LZR was so revolutionary that swimmers who did not have it won only 2 medals at the Beijing Games, and more importantly, only 2 Olympic records survived those games. It was a huge change. What happened then was that rival brands copied it, and advanced it by being even more aggressive.

For instance, the LZR had panels of polyurethane, one of the rivals made almost an entire suit of it. Swimmers started wearing more than one suit, thicker suits, tighter, more buoyant.  So the concepts that had led to advancements were driven more aggressively to create even more success, and because there was absolutely no regulation, FINA were powerless to do anything about it!

That’s why I said earlier that I think the policy should be “future proof” in the sense that once it starts, it’s like a truck rolling down a steep hill.  Rather leave the handbrake up and don’t let it roll in the first place.

I can easily foresee that happening here, that ‘arms’ race between manufacturers, IF the performance advantage is as large as claimed (I don’t necessarily think it is, though I think it’s greater than anything before.  To return to my previous concept, I think we were at Version X, this is Y, and what comes next is Z, and I’m not crazy about that idea)

Back to swimsuits – a number of swimmers, not lucky enough to be sponsored by Speedo, jumped ship and swam in the LZR in Beijing, basically saying “Sorry, but we’re not willing to risk not winning medals out of loyalty to you as a sponsor”. That of course sets up some kind of circular argument about why so many swimmers won Olympic medals in that suit, which I’m aware of (going back to my earlier point), but the more important one is that those in the suit were smashing Olympic and World records in every event but for two!

So I can see how this becomes the swimsuit issue – a marketing coup, perhaps, but also a situation where the performance can’t be trusted because the advantage is coming from technology that not everyone has access to.

Call me old-fashioned, but I want to see

  1. Equal racing, as far as this is possible, and shoes have never, in my opinion, been decisive to the outcome of a race, and nor should they be. If this shoe works, then that would potentially change;
  2. Performance evolution that can be trusted to have occurred as a result of human physiology, not engineering advances in an unequal way.

The Nike Vaporfly Elite may not disrupt either of those points – the effect on economy and performance might well be too small, and points 1) and 2) will remain intact.

But, the situation has presented itself as a conceptual one now, and whatever decision is taken here will have ramifications for the future, and if it’s not the Vaporfly then it may be something better, maybe from another manufacturer, in one, three or ten years, and I’d rather not be reactive then when you can arrive at a clean policy now. That’s why the IAAF should ban the addition of any device or material into the shoe other than foam that meets certain restricted requirements.

Thanks for stimulating the discussion, and for sharing your thoughts, really very interesting and good for me to be “forced” to formalize mine.


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