Finding the Secret Sauce: Demystifying Carbon-Fibre Plates

FOUR YEARS AGO, Nike launched the Vaporfly 4%, enthralling us with the promise its name implied: running economy improved by 4 percent.

- AMANDA FURRER

Before the shoe's release, Eliud Kipchoge wore the Vaporfly while attempting to run a marathon in less than two hours, in 2017's Breaking2 Project. He eventually succeeded two years later in the Alphafly Next%, the Vaporfly's beefed-up, controversial descendant.

It takes a superhuman like Kipchoge to break what was once thought an impossible barrier, but stats show the average runner can also benefit from running in super-shoes. In 2019, Strava data showed runners ran 4 to 5 percent faster in the Vaporfly or Next% compared to runners wearing an average running shoe.

Trailing Nike, other brands dove in, releasing their own rendition of super-shoes, adding a smidge of original flavour (e.g. Saucony's Speedroll tech; the decoupled midsole on the Puma Fast-R). But there are two common denominators these models share: a responsive midsole foam and a carbon-fibre plate.

The midsole foam is usually made from a polyether block amide thermoplastic (also known as Peba, or the Arkema-trademarked Pebax). Examples include Nike's ZoomX, Puma's Nitro Elite, and Saucony's PwrrunPB. Compared with standard foam (EVA), Peba is lighter, more compliant, and more resilient.

"Typically, foams act as a cushioning ingredient and plates act as a stiffening ingredient," said Rebekah Broe, director of product and performance footwear at Hoka, on a video call.

The plate limits flexibility, acting as a propulsion agent in the gait cycle. It works in harmony with the responsive foam sandwiching it, thus delivering even higher energy return as you run.