The news: the latest world records have almost all been made with Nike Vaporfly shoes on their feet. We mainly talk about two models: the Zoom Vaporfly 4% and the ZoomX Vaporfly Next%. Most recently, the women’s marathon record set by Brigid Kosgei in Chicago a few months ago stopped the clock at 2h14’04” and beat Paula Radcliffe’s unbeaten record since 2003 by more than a minute. And the day before, to make matters worse, his compatriot Eliud Kipchoge became the first man to run the distance of a mar athon (not an official marathon) in Vienna in less than two hours. At his feet, needless to specify, the 4% Vaporfly.
And one could stop here, thinking that we are still talking about stellar athletes who even with flip-flops on their feet would have posted incredible times. But the issue is a bit more complex and involves many more people, and we are talking about hundreds of thousands.
But let’s proceed in order.
4%
A percentage in the name of a shoe might seem like a marketing gimmick, and indeed it was initially interpreted that way. 4% was in fact the performance boost promised by these brand new shoes, launched in 2016 at Breaking2, the first attempt to go under two hours on 42,196 meters.
How was it obtained? First, with an incredibly responsive midsole compound called Pebax that promised (evidently delivering) to return 30 percent more energy expended by the runner than traditional shoes. And then there was and is the carbon plate sunk in that compound that adds propulsive force by charging on landing and discharging like a catapult on take-off.
Many cried out right away about mechanical doping and the unfair advantage such a solution gave to those who used them, the IAAF (i.e., the International Association of Athletics Federations) said the shoe did not violate regulations, and almost everyone, realizing where the market would go, set about making their own versions.
The survey
The achievements of elite athletes are one thing; those that we mere mortals can achieve are another. To consolidate them, however, there are data collected in considerable quantities, and they are those provided by one of the most widely used apps, namely Strava. As those who use it know, Strava records times, mileage, elevation changes, and even-if the runner wants it-the model of shoes used. It is by processing this data that a very significant sample of more than one million profiles who have run marathons or half-marathons since 2014 have been processed, obtaining data so detailed that it goes down to the level of shoe type. And thus being able to draw hypotheses supported by data on the benefits or otherwise that the type of shoe gave to the wearer.
Without delving into graphs and numbers, the most significant results that compared a few dozen models of shoes, the times obtained by the same runners with different models (in case they then ran a race first with one model and then switched in subsequent races to the Vaporfly) and other parameters gave an unequivocal picture: those wearing them ran 4-5% faster than with their previous shoes and 2-3% faster than runners wearing top shoes but of other brands.
The Nike Vaporfly phenomenon of the rest cannot be ignored, not least because since their introduction 41 percent of runners who have gone under 3 hours in a marathon use them, at least among those who use Strava (which, by the way, has such a large number of users that it can be considered very representative of the running universe).
One graph in particular is significant: it shows the probability of runners doing their personal best with a given model. Again, the Nike Vaporflys pull away from the competition by many points by scoring around 70 percent.
The solution?
One may turn one’s nose up at such data or be skeptical. Yet it cannot be overlooked that they are not from Nike and are freely collected using an app that has nothing to do with who makes these shoes and provided the data anonymously only for statistical purposes.
It could also be argued that we are not machines and that times obtained even in the same race but in different years do not mean much: so many variables can distort the data, such as weather, runners’ preparation, route, etc.
One thing, however, is indisputable, especially in statistical terms: the sample of data is very significant, and the larger it is, the more the error or exception to which a small number of data would be sensitive tends to disappear. In short, if there are 10 of us friends who run faster, we do not form a particularly representative sample; if in addition to the 10 of us there are hundreds of thousands of others, well, the discourse changes and seems to say only one thing: with the technical solution developed by Nike with the Vaporfly you go faster. It is a certain alchemy given by the midsole compound and the flexible carbon plate, and many other manufacturers can and already are adopting it.
This means only one thing: if they are not banned by the IAAF at least in official competitions, most shoes will be like this in the future. Most importantly, they will cost less than the 250 euros it takes today.
Better for everyone, right? Faster, spending the right amount.
(Via The New York Times)