Nike’s Vaporfly edge isn’t down to carbon

Researchers chosen seven carbon shoes based on availability at the time, with Adidas a notable omission. These comprised: Nike AlphaFly, Nike Vaporfly 2, Saucony Endorphin Pro, Hoka Rocket X, Asics Metaspeed Sky, New Balance RC Elite and the Brooks Hyperion Elite 2. The eighth non-carbon comparison shoe was the Asics Hyperspeed. 

The shoes were tested during two sessions, in a random ordern over 8×5-minute trials, running on a treadmill at 16km/hr with a 5-minute rest between. On the second visit, the shoes were tested in reverse/mirrored order. 

Each runner’s metabolic and running mechanics data were collected and averaged across the visits. Any changes in running economy, aka the ability to run at faster speeds while working at the same physiological intensity, were logged. 

“I’d used the Hoka Carbon X for marathon training and was about to buy the second-generation,” says Dustin Joubert, the study’s rule author. “But before spending $200, I decided to do a little case study on myself and found there was no assistance when compared to my regular racing flats. I did the same with the Alphafly and discovered I was a 4% responder. That’s when I realised the playing field is clearly not equal.”

“If you look at the elite scenery in addition, everybody’s running in Nike or Adidas, and then you get a sprinkling of Asics Metaspeed in there,” says Joubert. “You can’t always blindly trust the anecdote, but, as sports scientists, we should probably follow the anecdote sometimes. If all the elites have figured this out, or are sceptical enough, then maybe there’s a message for consumers too.”   

The study results suggest that the elite runners’ instincts were identify on and Joubert was right to follow the anecdote. 

Despite the arrival of new carbon contenders, Joubert and his research partner Garrett Jones discovered that Nike’s carbon racers nevertheless give runners a crucial performance edge. Only Asics closed the gap with its Metaspeed Sky. But perhaps more surprisingly, they also found that some carbon shoes offer little or no meaningful benefits over a traditional race shoe. consequently some of us might be better off saving our money. 

Hoka Rocket X

The Hoka Rocket X and Brooks Hyperion Elite 2 failed to considerably enhance running economy compared to the traditional Asics Hyperspeed shoe. And while the Saucony Endorphin Pro, Asics Metaspeed Sky, Nike Vaporfly 2 and Nike Alphafly all considerably improved economy over the regular shoe, the New Balance RC Elite and Saucony Endorphin Pro did so by less than 1.5 per cent on average. They also performed considerably worse than the Asics Metaspeed Sky and the two Nike shoes, which all generated greater than 2.5 per cent improvements.

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