Nike’s VaporFly ZoomX running shoes have been making headlines for their use of a carbon fiber plate that’s being attributed to faster marathon times, including the first marathon completed in under two hours. Carbon fiber is often a popular choice in sporting equipment because it’s lightweight and durable, but what does the carbon fiber plate in a running shoe actually do?
Keep reading to find out what the buzz is all about in carbon fiber footwear and how it’s impacting more sports than marathon running.
Where is the Carbon Fiber in a Running Shoe?
Carbon fiber in a running shoe is generally a stiff plate that’s part of the sole of the shoe. It’s usually fixed in a lightweight foam with a shoe profile and heel height that vary from shoe to shoe, but are valuable for specific running styles. The plate doesn’t take up much of the sole. For example, in the Brooks Hyperion Elite, the carbon fiber plate is only one millimeter thick with a raised spine of 0.5mm through the midsole of the shoe.
Nike isn’t the only footwear provider adding carbon fiber to their running shoes. In fact, Brooks, New Balance, Saucony, and Hoka One One all have shoes available or in development with the notorious carbon fiber plate. With the recent ruling by World Athletics that will allow Nike’s VaporFly ZoomX shoe at the Tokyo 2020 Olympic games and clarifies the use of foam and carbon fiber in shoes, expect to see more shoemakers turning out carbon fiber kicks in the near future.
Carbon fiber consumer products can often run at higher price tags than their counterparts, but these shoes generally cost between $140-$250, which is highly comparable to other professional-level running shoes.
Why Carbon Fiber?
We know carbon fiber is lightweight, especially compared to the metals it often replaces in automotive, aerospace, and industrial applications. And weight is valuable for speed in any race, which makes carbon fiber an important material in a racing bicycle. But running shoes nowadays are mostly made of lightweight foams and polyester fabrics, so what assistance does carbon fiber offer runners that these materials don’t?
The goal of using carbon fiber plates in athletic shoes is rooted in the idea of improving energy return, particularly at the “toe-off,” or where an athlete’s toe pushes off the ground. The carbon fiber plate is shaped with a curve at the arch that bends slightly downward under the ball of the foot. The intent is to store energy when the heel strikes the ground and release the athlete’s own energy back to them at the toe-off, giving a boost. When combined with springy, lightweight foams like Brook’s DNA Zero and Nike’s ZoomX, the energy return is enhanced even more.
Additionally, scientists have found that the carbon fiber plate is beneficial for stabilizing the ankle joint, reducing the load on the calves, and keeping the toes straight—all important for a strong running form and lowering the risk of injury. In fact, Brooks Hyperion Elite shoe was built to improve support in addition to speed.
What’s the Benefit of Increased Energy Return?
When it comes to running, increased energy return does improve speed with that extra boost on a runner’s toe-off. The foam and carbon fiber combinations also produce lighter shoes, with the lightest, the New Balance FuelCell 5280, weighing in at only 5.3oz (VaporFlys weigh 6.6oz). The improved speed is valuable for competitive long-distance runners where every second counts.
Other sports can benefit from the shock absorption and increased energy return, too. The company, VKTRY, produces a line of carbon fiber shoe insoles that are suited for a variety of sports. Unlike the stiff plates in running shoes, VKTRY’s insoles are flexible and use layers of different lengths of carbon fiber arranged in different directions. VKTRY uses an algorithm to determine which insole will meet an athlete’s needs, based on their sport and physical attributes.
The increased energy return is beneficial for jumping athletes, like basketball and volleyball players, where they experience higher jumps and less force on landing. VKTRY originally concocted their insoles for bobsledders, using the energy return to give more force behind their running starts, but athletes in football, baseball, and beyond are finding improved performance with the flexible carbon fiber insoles. An independent study of the insoles found they provided a 9% rate of force development over not using them.
Carbon fiber shoes are just hitting their stride in professional sports, and plenty of runners will likely utilize them during this summer’s games. At PCMI, we’re experts in carbon fiber casting for automotive, aerospace, and industrial applications, and we have our own innovative casting process for carbon fiber composites. Learn more about our cost-effective carbon fiber casting solutions in the link below.