Nike’s Vaporfly edge is not due to carbon

The study looked at the performance of high-end shoes on 12 trained male distance runners, size 10-11 US, who had run at least three times per week in the previous three months. Each runner had also recorded a running performance of less than 5:30 minutes, 5 km (or equivalent running performance for distances of 3 km to the marathon) in the past year and had the ability to run below the lactate threshold at the tested run economy of 16 km / h speed. It’s a little over 6 mins / mile or 3.75 mins / km, so the fastest end for amateur runners.

Researchers selected seven carbon shoes based on availability at the time, with Adidas being a notable omission. These included: Nike AlphaFly, Nike Vaporfly 2, Saucony Endorphin Pro, Hoka Rocket X, Asics Metaspeed Sky, New Balance RC Elite and Brooks Hyperion Elite 2. The eighth carbon-free comparison shoe was the Asics Hyperspeed (from £ 89).

The shoes were tested over two sessions, in a random sequence over 8×5 minute trials, running on a treadmill at 10 mph with a 5 minute rest in between. On the second visit, the shoes were tested in reverse / mirror order.

The metabolic and mechanical running data of each runner was collected and averaged during the visits. All the changes in running economy, i.e. the ability to run at faster speeds while working at the same physiological intensity, were recorded.

“I had used the Hoka Carbon X for marathon training and was about to purchase the second generation,” says Dustin Joubert, lead author of the study. “But before I spent $ 200, I decided to do a little case study on myself and found that there was no advantage over my regular racing flats. I did the same with the Alphafly and found out that I was a 4% responder. It was then that I realized that the playing field was clearly not level.

“If you also look at the elite landscape, everyone is running in Nike or Adidas, and you get a pinch of Asics Metaspeed in there,” Joubert explains. “You can’t always blindly trust the anecdote, but, as sports scientists, we should probably sometimes follow the anecdote. If all the elites have understood this or are skeptical enough, then perhaps there is a message for consumers too.

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

Despite the influx of new carbon competitors, Joubert and his research partner Garrett Jones found that Nike carbon runners still provide runners with a crucial performance advantage. Only Asics closed the gap with its Metaspeed Sky (£ 225). But perhaps more surprisingly, they also found that some carbon shoes offer little to no significant benefit over a traditional running shoe. Therefore, some of us had better save our money.