And in the month after those first mysterious photos, Kipchoge, wearing Vaporflys, would claim his first marathon world record in 2:01:39 at the 2018 Berlin Marathon.

In the two years prior, Nike's new Vaporfly, unique for its thick, bouncy Pebaxbased foam midsole and carbon-fiber plate, had upended the less-is-more maxim governing racing flats by winning-sometimes sweeping-nearly every major marathon it entered. This was the first spark of speculation on how Nike planned to follow up on its world-beating Vaporfly, though Kipchoge had already been testing prototypes since January. There, atop the red Kenyan soil, Kipchoge is wearing a nondescript black upper attached to a chunky slab of what looked like the Vaporfly's ZoomX foam. WHEN THE PUBLIC first noticed Nike's new Alphafly, it didn't look like much: In August 2018 the French Instagram account posted a photo of Eliud Kipchoge flanked by smiling runners. THE FASTEST MARATHON SHOE EVER Runner's World US | IsTHERE ARE FEW SECRETS SURROUNDING NIKE'S ALPHAFLY, YET SCIENTISTS STILL STRUGGLE TO EXPLAIN WHY THE SUPER SHOE IS SO SUPER.

Download fastest marathoner