In late June, among the first hundred or so runners at Grandma’s Marathon in Duluth, Minn., there was a distinct sea of bright red shoes that seemed to float along the course. Same thing at the front of the California International Marathon (CIM) last December.
While we’ve become accustomed to seeing this among the mostly-Nike-sponsored elites at World Marathon Majors, it was clear Nike’s Vaporfly 4% Flyknit was also the overwhelming shoe of choice for these mostly-unsponsored elite and semi-elite runners near the front of the pack. Why? Not only was the Vaporfly spit out of a massive Nike hype machine, the shoe and its carbon-plate technology had proven itself with Olympic medals, major marathon wins and Eluid Kipchoge’s 2:01:39 world record at the 2018 Berlin Marathon.
The Vaporly 4% was the first of what has become a new generation of super shoes made from new materials and radically innovative designs aimed at dramatically improving running performance. Even with prices ranging from $180 to $250, they’ve become all the range among amateur runners shooting for a half-marathon or marathon racing goal.
“Those shoes are all about improving your efficiency as a runner, and that might mean upping your cadence, giving you a bit more pop in every stride or just making you feel faster and more fluid,” says Dan O’Keefe, a customer experience manager at Naperville Running Co. in suburban Chicago. “They’re not for everyone, so you’ve really got to be a performance-oriented runner to be willing to spend $250. But the bottom line—and the reason so many runners are buying them—is that the technology has proven itself to work.”
With the Vaporfly 4% Flyknit and Nike’s subsequent Zoom X Vaporfly Next% model leading the way, you can find a host of these next-generation shoes changing the face of road racing. So much so that they’ve made regular lightweight performance trainers and racing flats—shoes that typically cost $100 to $120—obsolete on race day and hard workout days.
It Started with the Foam Wars
Six years ago, when Adidas released its revolutionary Boost midsole foam, it not only re-asserted the German company as the most dominant global brand in long-distance racing shoes but it also set off a firestorm inside the R&D labs of just about every other shoe manufacturer. Boost, made from TPU pellets thermally welded together, was the first midsole foam to serve up high levels of both shock-absorbing cushiness and bounce-back responsiveness.
As Adidas-sponsored runners Wilson Kipsang (2:03:23 in 2013) and Dennis Kimetto (2:02:57 in 2014) lowered the world record in the marathon wearing Boost-enhanced racing flats at the Berlin Marathon—and generating excitement about the possibility of a sub-2-hour marathon—other brands were rushing to source and develop innovative foams, re-think shoe geometry and experiment with new materials to enhance the shock absorption, improve efficiency and reduce energy loss in every stride. Nike launched a special project within its internal research lab to aggressively go after the world’s first sub-2-hour marathon, including, of course, the ultimate marathoning shoe.
Over the next several years, Hoka One One (RMAT), Saucony (Everun), Brooks (DNA AMP), Puma (Ignite) and Altra (EGO) debuted multi-compound materials that combined traditional EVA foam with rubber, polyurethane and air. Those new foams graded out well in laboratory tests and earned rave reviews in new footwear models, but it was only the tip of the feather when it came to lightweight and resilient foams. A few years later, Nike discovered a super-light and extremely energetic material that would eventually become its squishy and springy ZoomX foam.
While the lightweight, dual-purpose foams have played a big role, it’s been the advent of stiff carbon-fiber propulsion plates embedded in the midsole that have become the biggest buzz in marathon running. The semi-curved plates act like a levering device, enhancing forward propulsion by moving the foot through the gait cycle as quickly and efficiently as possible without excess muscular force in the forefoot at the toe-off phase.
The idea of using carbon-fiber elements in a running shoe isn’t new. Reebok incorporated a lightweight carbon-fiber support bridge under the arch of its Graphite Road shoes in the 1990s. In the early 2000s, Adidas built a carbon-fiber propulsion plate in its ProPlate racing flat, while Zoot Sports used one into its Ultra Race triathlon racing shoes in 2007. More recently, a start-up brand called Ampla developed a shoe called the Fly with a carbon-fiber spring-like flange intended to load under pressure and launch forward as a runner’s foot landed and then lifted off the ground.
None of those gained much acclaim, partially because the shoes never proved their worth with new records or stunning analytical data, especially with their relatively high price tags. Nike changed all that when unveiled its VaporFly Elite two years ago in Monza, Italy, where Kipchoge came up just short of running the world’s first sub-2-hour marathon with an eye-popping 2:00:25 in an unsanctioned time trial exhibition. The idea behind the VaporFly Elite, as well as the VaporFly 4% and the new VaporFly Next% shoes, was that the plate was acting as a lever (and not a spring) that saved energy in the forefoot and reduced lost energy the ankle.
A recent study published in Footwear Science and presented last month at the Footwear Biomechanics Symposium confirmed that the more radical the curve in the plate, the greater the energy that is saved in the forefoot and less the energy that is lost in the rearfoot.
Although the science is new, shoe brands have been researching prototypes with carbon-fiber plates for several years and many are now rolling out their own models. Hoka One One brought two carbon-plate shoes to market in the past year, the EVO Carbon Rocket and the CarbonX, while New Balance will debut its FuelCell 5280 in September. Meanwhile, Skechers, Brooks, Saucony and 361 Degrees USA are scurrying to release their own carbon-fiber enhanced models within the next several months.
“It’s not even about racing all-out,” says Mike Wardian, a Hoka-sponsored competitive masters marathoner and ultrarunner. “I think the addition of the carbon-fiber plate just facilitates and efficient stride in a way that a shoe with only foam cannot. It doesn’t matter if you’re running super fast or tempo pace or even a slower pace. It’s guiding your foot and maximizing your ability to run smooth and efficiently.”
Super Foams and Beyond
But while the carbon-fiber plates play a role, it’s the newfangled foams that are most impressive.
Nike’s ZoomX foam has tested out with an 85 percent energy return rate, believed to be the highest ever put into a running shoe. (Most premium running shoe foams have an energy return rate in the 50 to 70 percent range.) A University of Colorado study, released in early 2019, revealed, in fact, that the foam returned 45 times more energy than the plate.
Earlier this year, Skechers unveiled Hyper Burst, an extremely responsive featherweight foam created by saturating a solid piece of EVA with carbon dioxide that has been heated and pressurized into a super critical fluid state. After saturation, the CO2 returns to its normal gas state, creating thousands of bubble-like cell structures trapped within the EVA midsole, making it lighter and more resilient than traditional foams. Skechers won’t reveal energy-return figures for Hyper Burst, but it feels significant running at tempo pace or above.
So were will shoes go from here? The possibilities are limitless, says Hoka One One co-founder Jean-Luc Diard, global vice president of innovation with the brand’s parent company, Deckers Inc. If you compare the evolution of running shoes over the past 30 years to other sports equipment, cars or cell phones, the spectrum of variation is much greater for those other consumer products, he says, which suggests there is much more innovation to come in running shoes.
“The foot is what it is; we can’t change it,” Diard says. “But we can change the interface between the foot and the ground, and that’s what’s important. If you look at a shoe purely as an extension of the foot, you limit yourself in your thinking. But when you look at it as a piece of equipment that can offer a dynamic blend of attributes—how it provides comfort, how it contributes to performance, how it interacts with terrain—then you start to push the boundaries of how shoes can be designed.”
Some of Today’s Super Shoes:
New Balance FuelCell 5280, $200
5.1 oz. (men’s), 5.6 oz. (women’s)
10mm heel-toe offset (39mm/29mm)
A shoe designed for racing the mile on the roads, the FuelCell 5280 has a full-length carbon-fiber plate and an extremely soft midsole foam that bottoms out when heel striking. This shoe is meant to be run very fast and feels a bit like a pair of track spikes, so heel-striking shouldn’t be an issue. The full-length, multi-direction plate is designed to flex at initial impact and then stiffen for propulsion at toe-off. Although there is little structure in the chassis of this shoe, it features a comfortably snug fit and moderately supportive knit upper.
Nike Zoom Vaporfly 4% Flyknit, $250
6.7 oz. (men’s/unisex sizing)
10mm heel-toe offset (39mm/29mm)
This is the updated version of the original 4% shoe that turned heads two years ago with Kipchoge’s 2:00:25 simulated marathon in Nike’s Breaking2 Project. This version with the Flyknit upper debuted to the public in September 2018, just after Kipchoge wore it to run a record-shattering 2:01:39 at the 2018 Berlin Marathon. It’s a super-light shoe that gives off a prominent, energetic levering sensation as the foot rolls to the forefoot and on through toe-off. Wear-testers suggest making sure the shoe is a good fit for your foot, as many have reported that it fits a bit loose in the heel and slightly snug in the forefoot because of a low-volume toe box. Also, this model isn’t ideal for a consistent heel-striking gait because the soft foam and unstructured rear of the shoe make it a bit wobbly.
Nike Zoom X Vaporfly Next%
6.6 oz. (men’s/unisex sizing)
8mm heel-toe offset (40mm/32mm)
The Next% shoe debuted on Nike’s elite runners in Boston and London in spring 2019—taking Kipchoge to a 2:02:37 victory in London, the second-fastest marathon of all-time. Nike took the learnings of its original 4% shoe and developed a new shoe with more rear-foot cushioning, a new hydrophobic upper, a lower heel-toe offset, a higher stack height and a more bulbous outsole geometry with better traction in the forefoot. The result is a slightly lighter, snappier and more stable shoe. While the Next% is generally considered to be an improvement to the 4%, the flimsy tongue isn’t ideal and can cause irritation if not laced while completely flat.
Nike Zoom Pegasus Turbo 2, $180
7.3 oz. (men’s), 6.1 oz. (women’s)
10mm heel-toe offset (28mm/18mm)
When testing prototypes of the original Nike VaporFly Elite, wear-testers liked the versions without a carbon-fiber plate so much that the brand opted to release it as a performance trainer model in its popular, do-everything Pegasus line. The initial version of the Pegasus Turbo (with a single-density Zoom X midsole) was moderately energetic but extremely soft and mushy. The second edition has been improved with a new, softer mesh upper, a two-layer midsole (Zoom X and React foams) and less padding on the tongue and ankle collar. Turbo 2 is a tad lighter, more stable and snappier. While no percent-performance gains are promised, testers find themselves going faster with less perceived effort in these quick-turnover shoes.
Hoka One One EVO Carbon Rocket, $160
7.3 oz. (men’s/unisex shoe)
1mm heel-toe offset (28mm/27mm)
Hoka quietly released this lightweight, moderately cushioned racer with a carbon-fiber plate last winter after Cam Levins set a new Canadian marathon record of 2:09:25 in his debut at the distance last October in Toronto. It’s pegged as a 5K to half marathon racer with a softer foam directly under the foot and a more durable, energetic foam below the carbon-fiber plate. With a snug, athletic fit from its two-layer mesh upper and a low-to-the-ground feel for the ground from heel to toe, the Carbon Rocket feels light and fast the moment you slip it on.
Hoka One One CarbonX, $180
8.8 oz. (men’s); 7.1 oz. (women’s)
5mm heel-toe offset (35mm/30mm)
This shoe also received plenty of hype right out of the gate when Jim Walmsley set a new world best for 50 miles (4:50:07 during an exhibition time trial held in Sacramento in May). Unlike the squishy Nike shoes with stiff carbon plates, the Carbon X feels moderately soft and very stable, allowing a wider range of runners (and slower paces) to benefit from the propulsion provided by the carbon-fiber plate. It feels smooth and consistent running at faster speeds, but it takes a bit of practice before finding a rhythm at moderate paces.
Skechers Performance GoRun Razor 3 Hyper, $130
6.4 oz. (men’s/unisex shoe)
4mm heel-toe offset (24mm/20mm)
Skechers debuted its one-of-a-kind HyperBurst midsole foam, which delivers high amounts of cushioning and responsivness. While it feels soft, it doesn’t bottom out but instead serves up an energetic boost in every stride. Although it’s a low-to-the-ground racing flat, the nature of that foam is such that it can hold its own for longer race distances, even up to a marathon for a strong and agile runner. There’s not much to the upper, but the lacing system reliably cinches the foot to the chassis with help from a few TPU overlay bands. The fit is snug and narrow, although there is a twinge of wiggle room in the toe box. A version with a carbon or Pebax plate is rumored to be released imminently.
Brian Metzler is the author of Kicksology: The Science, Hype, Culture and Cool of Running Shoes. (2019, VeloPress)