Hopefully you all can read this link. If not, look on the NYTimes website for The Upshot, and the story on the Vaporfly.
Fascinating story. Nike released the Vaporfly shoe last year, claiming it could make you 4% faster. Think about it – if you could run a 4 hour marathon, that means almost 10 minutes faster, at least by my math.
This story in the NY Times examined a pile of data culled from Strava, and the authors say the claim may be true. Astounding.
I think there may be a self-reporting bias in the data – those buying the shoe are looking to improve, and may be doing other things, like training better, and believing they will do better in the shoes. As we all know, the mental part of running is huge. To paraphrase Yogi Berra, "the game is 90% mental, the other half is physical." The data also come from a community (Strava) of eager beavers, who may be more prone than most to believe, and to unwittingly bias their self-reporting.
That said, the sample size is large, and the authors cut the data every which way and got the same results.
One alarming note was that while the shoes cost $250, if you can get them, they lose their effectiveness as quickly as 100 miles.