Eldoret Kenya 2017, Eliud Kipchoge is putting the Nike ZoomX Vaporfly Elite through its paces. Kipchoge has played a pivotal role in working with Nike to redefine the racing shoe. Nike has worked alongside Kipchoge through all versions of the Vaporfly, through to the Alphafly which helped him break the 2 hour marathon. Kipchoge will run 300-500 miles in a shoe before he’s finished testing it, while keeping a detailed journal of his likes and dislikes of the shoe. 

“Every day, I keep writing the marks from 1 to 10, concerning the comfortability of the shoe, the traction, the absorption of the impact and the material used. The number one feedback was the impact from the ground.” Eliud Kipchoge. Behind The Design 2020. 

While traditional running shoes (flats) traditionally kept a low profile, the Nike ZoomX Vaporfly went on to be extremely lighter, softer and more responsive. The large stack height in the shoe accompanied by a carbon plate was unheard of in racing flats. Historically, big stacks of foam and rubber would make running shoes heavier - hence why running companies would make thinner, more responsive racing flats for the big day. But the number of runners actually wearing these minimal, fast race specific shoes was very small. Nike set out to change that. 

Nike’s previous running shoe foam returned 60-65% of the energy put in by the runner. The original ZoomX foam on the other hand returned approximately 85%. Then sandwiched between the ZoomX foam is a curved, stiff carbon fibre plate. Nike had to get the right balance of stiffness with the shoe. Stiffer shoes have a big benefit on running economy, but too much stiffness can shift the workload from the foot up into the calf. Over 26.2 miles, this would cause fatigue, but the specific geometry of the ZoomX Vaporfly Elite reduced that problem. 

Kipchoge continues to help Nike in developing running shoe prototypes. We have now seen developments of the upper material - shifting from FlyKnit, 3D printed FlyPrint, Vaporweave and now AtomKnit. The Vaporfly has continued to power all level of runners to the finish line, as Nike continue to push the boundaries of running shoes. 

Images: @letsrundotcom