Why modern marathon racing shoes should be legal and celebrated as the technological advancements
By Brian Metzler
There’s been a lot of chatter this week about Tigst Assefa’s new women’s world record in the marathon of 2:11:53 that she set on September 24 in Berlin. It was an amazing run to be sure, as she chopped more than 2 minutes off the previous record and won the race by nearly six minutes. Plus, she did it by running negative splits, running the first half in a blazing fast 66:20 first half (that was already well ahead of world record paces) and then coming back even faster in 65:33 for the second half.
But the biggest focus this week has been about her shoes. She was wearing the much-ballyhooed Adizero Adios Pro Evo 1 racing shoes that the German footwear maker announced only a week before the race. It’s the brand’s next-gen marathon racing supershoe that is not only considerably lighter than every other shoe in that category (with a spec weight of just 4.8 ounces!), but it also has a different shape that helps create a hyper-responsive, energy-returning gait cycle.
If you’re a running shoe geek like me—or even just an age-group marathoner interested in the evolution of running shoes—there’s a lot of excitement and skepticism about how much the shoes might have helped her run such an incredible time.
Did the shoes help her break the world record? Yes, absolutely they did. Without the advanced technology of that shoe—a new formulation of Lightstrike Pro foam, a curvy carbon-fiber plate and, perhaps most importantly, a revamped geometry with a first-of-its-kind forefoot rocker, placed at 60 percent of the length of the shoe—there’s no way she would have run as fast as she did.
But let’s keep in mind that she also cranked out a 2:15:37 effort (then the third-fastest time in history) en route to winning the 2022 Berlin Marathon wearing a pair of Adidas Adizero Adios Pro 3 shoes. And the previous women’s world record of 2:14:04 set by Brigid Kosgei at the 2019 Chicago Marathon was also set wearing an advanced pair of supershoes (Nike’s Vaporfly Next% shoes).
Every brand has its own version of a marathon racing supershoe—for example, Hoka’s Rocket X 2, Nike’s Vaporfly 3, ASICS’s Metaspeed Sky+ and Puma’s FAST-R—but it’s the competition between brands and the lowering of world records that’s really the driving force (along with highly trained athletes) behind the innovation that’s moving the needle in the sport.
Even though the current supershoe revolution started in about 2017, the competitive arms race between running shoe manufacturers has been going on for decades. From the late 1970s to the early 2000s, though, most running shoes were built on EVA midsoles, which meant brands were just trying to come up with lighter upper materials and outsole configurations to create the most optimal race shoes of those eras.
There’s no question that recent advances in shoe technology have changed the game of marathon running, both for elite professionals and dedicated age-group runners. The technological improvements in shoes over the past six years makes it impossible to even compare times from other eras. If you’re an age-group runner who set your marathon PR wearing conventional racing shoes with an EVA foam midsole, comparing it to the recent PR your running partner, co-worker or neighbor just set is an apples-to-oranges argument.
It’s not that runners weren’t running fast in shoes with more basic foams, though. When Haile Gebrselassie became the first runner to break the 2:04 plateau (2:03:59 at the 2008 Berlin Marathon), he wore in a pair of Adizero Adios shoes that had a midsole made of compression molded EVA foam and Adidas’ proprietary Adiprene foam. Compared to modern materials, those foams were nothing special and, in fact, quite rudimentary in that they didn’t offer very much energy return at all. Plus, there was no carbon-fiber plate acting as a propulsive lever inside the shoes.
The point is that hard work and smart training are still the biggest components to an optimal performance on race day. The only difference you need to be lacing up a pair of modern supershoes to achieve your best time.
When Dennis Kimetto ran a 2:02:57 to win the Berlin Marathon in 2014 and Mary Keitany ran 2:17:01 to win the 2017 London Marathon, they were wearing Adidas Adizero Adios Boost 2.0 shoes. The initial Boost midsole foam that was released in 2013 was the original high-rebound superfoam that helped take the marathon shoe arms race to the next level, but that material became ridiculously outdated once Nike developed its first shoes with its Pebax-based ZoomX foam and carbon-fiber propulsion plates.
But now that we’re on the verge of the men’s world record dipping below 2 hours—and yes, Kipchoge already famously ran 1:59:40 in an unsanctioned time trial in Vienna in 2019, so we know it’s possible—and the women’s world record dropping below 2:10, a lot of skeptics are concerned that the shoe technology has gone too far. However, I’m not one of those skeptics.
Should those types of shoes be banned? Absolutely not! But there are some caveats.
My take has always been that the shoes should be legal based on three separate criteria. First, the shoes need to be vetted out by World Athletics and posted on its approved list before anyone runs in them. Secondly, to ensure a level and fair playing field at every race, the shoes need to be readily available to everyone and not proprietary to a singular brand that’s making them only for their sponsored athletes. (Whether runners choose to wear a model made by the band that sponsors them or another brand’s shoes is up to them.) And thirdly, and most importantly, the shoes cannot provide additional energy to a runner’s stride.
But the key to that is understanding that last point is that supershoes are not artificially or mechanically providing a boost of energy, but instead only returning more (or losing less) of the energy the runner is putting into each stride. Essentially the foam and the plate in each shoe is capturing the downward energy of each stride and helping convert as much as possible into the forward energy of the next stride while also reducing the harmful blunt force impact as a runner’s foot hits the ground. It’s similar to the idea that cutting higher tax rates does not give workers more money in every paycheck, it just lets them keep more of their earnings.
If each of those criteria are met, then these supershoes should be legal and celebrated as the technological advancement of sporting equipment that can benefit both elite runners and age-groupers like you and me. Does the sport need to do a much better job at rooting out performance-enhancing drugs and elite-level dopers? Yes, absolutely it does. But that’s an entirely different conversation. From a pure footwear point of view, Aseffa’s Adidas Adizero Adios Pro Evo 1 racing shoes have taken marathon running to the next level.