SOLE
THERE ARE FEW SECRETS SURROUNDING NIKE’S ALPHAFLY, YET SCIENTISTS STILL STRUGGLE TO EXPLAIN WHY THE ALPHA SUPER SHOE IS SO SUPER
T HE PUBLIC’S FIRST LOOK at Nike’s Alphafly wasn’t pretty. In August 2018, the anonymous Instagram account @protosofthegram posted a blurry, cropped photo of disembodied ankles sprouting from a nondescript black upper attached to a chunky slab of what looked like the Vaporfly’s ZoomX foam. The caption stated that an air unit was hidden in the forefoot and that the legs belonged to Eliud Kipchoge. This was the first hint of how Nike planned to follow up on its record-breaking Vaporfly, though Kipchoge had already been testing prototypes since January.
In the two years leading up to that point, Nike’s new Vaporfly, then unique for its thick, bouncy Pebax foam midsole and carbon-fibre plate, had upended the less-is-more maxim governing racing flats by winning – sometimes sweeping – nearly every major marathon it entered. 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.
More photos of the new prototype, midsole seemingly (and bewilderingly) thicker than the Vaporfly’s, surfaced every few months until, in October 2019, in Vienna, Kipchoge wore a polished version of the still-unnamed shoe to clock the first sub-two-hour marathon in recorded history at the Ineos 1:59 Challenge. The following June, the Air Zoom Alphafly Next% was released and, last year, was updated as the Alphafly 2. Meanwhile, Kipchoge has worn Alphaflys to lower his official world record to 2:01:09 and claim his second Olympic marathon gold medal.
While the new shoe, with its added air chambers, is an obvious evolution from the Vaporfly, the Alphafly is mechanically familiar: a generous block of responsive foam stabilised by a heel-to-toe carbon-fibre plate. That’s no longer a mystery. But how, exactly, does that system translate physiologically to the fastest marathon(s) ever run? That’s what biomechanists are still trying to work out.
THINKING BIG
THE PREMISE OF THE Alphafly is simple, says Carrie Dimoff, the Nike director of innovation who leads the Alphafly development team. ‘If we can store more of your energy, we can return more of that energy and you can run more efficiently.’
All of running is energy maintenance, from our shoes to our stride. ‘We’re essentially giant springs as we run,’ says Geoffrey Burns, a sports physiologist at the US Olympic Training Center. In the air, between footfalls, we’re gathering potential energy both from the forward motion of our previous step and as gravity pulls us down.
