Knitted footwear technology is poised to enhance sustainability and walkability alike.

On a recent Monday morning in Portland, Oregon—that walkable mecca routinely voted one of the country's most livable cities, and also home of the North American headquarters for Nike and Adidas—I found myself mesmerized by the feet of passersby. We look to our shoes not just to bring us from place to place but also to telegraph our identity. They're a little like cars in that sense, except we can buy a whole lot more of them, so we can change that identity from one day to the next. But despite the varying looks of shoes, the basics of making them haven't changed much. Until now.

Since pretty much the dawn of the Industrial Age, shoes have been made like this: pieces of leather and other materials cut and sewn together in what's called the "upper," then glued to a hard sole. Despite the machine element, much is still done by hand, with skilled workers needed to put the shoes together; materials are often sourced from different places, with shoes shipped back and forth several times before completion. But two years ago, in the lead-up to the London Olympics, Nike and Adidas released their first knitted running shoes: Flyknit for Nike, Primeknit for Adidas. Each sneaker's upper is machine-woven from a single piece of fused yarn. Less waste, less labor, and a cool new look.

Ever since, the two shoe giants have been waging a Flyknit vs. Primeknit war, with Nike suing Adidas for patent infringement (Nike lost that court battle; much as you can't patent a knitted sweater, it's tough to patent a knitted shoe). In March, Adidas released the first knitted soccer cleat, followed by a knitted cleat-and-sock hybrid; Nike's knitted neon Mercurial and Magista cleats are what you saw on Cristiano Ronaldo and other star players during the World Cup.

Feuding and football aside, knit technology just might transform the entire traditional shoemaking process. Athletic shoes make up 30 percent of all footwear sales, and Nike and Adidas dominate, with $14.5 billion and $9.5 billion in sales, respectively, in 2013. Widespread use of the knitting technique could boost the industry's efficiency—cutting down on materials, labor, shipping, and time, as the products can be made start-to-finish in one place. In its latest sustainability report, Nike states that a Flyknit running shoe is made with 80 percent less waste than a typical Nike design. Consider that Americans buy an average of seven pairs of shoes a year—that's more than two billion new pairs annually—and you begin to see the difference that a change in manufacturing could make.

Primeknit, a new shoe from Adidas, is made from knit-technology that could transform shoemaking. (Courtesy Adidas)

Sneakers, of course, aren't just for sports. What a star athlete wears one day informs what a teenager wears on the street the next. In 2012, the fashion crowd fell hard for the knitted-shoe look; every other man at that season's fashion shows was "suddenly rocking orange-and-electric-blue Nike Flyknits with his summer suit," Gilt Groupe's Tyler Thoreson later told the New York Times. Both Nike and Adidas fully intend the new technology to apply to lifestyle footwear, not just athletics, and smaller companies are already adopting the designs.

With more Americans than ever saying they prefer to live in walkable places, footwear has a role to play into the future of U.S. transportation. And for two of the world's biggest shoe companies, lifestyle footwear—what you wear when you're walking around all day, every day—is where the money is. Sustainability is their future.

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James Carnes, the global creative director of sport performance for Adidas, tells me that the conventional, high-waste method of making shoes is like working with a roll of cookie dough. "You always end up with something," he says. "You start with bulk materials and cut things out. But with leather and mesh, you can't roll it up and use it again. You end up creating waste, using thread, glue, and so on. Every single step is an additive process." Carnes says Primeknit was conceived first and foremost as a sustainability solution—how do we build products with zero waste?—but unlike other processes tried to date, it ended up being one that didn't sacrifice performance.

With knitting, you start with a single thread, and you only use as much yarn as you need. "Picture a flat pattern in a butterfly shape," says Carnes. "With the knitting process, you only make that. That's the breakthrough. You can build into the single knitted layer all the functionality you need, by adjusting the density of the knit in different areas"—a tighter weave to give the foot more arch support, say, or a thinner, breathable weave to create more airflow. The possibilities are limitless, he adds, because you can knit anything that can be made into a yarn: carbon, wool, Kevlar, even gold and stainless steel. Knitting also makes it easy to experiment with new colors and patterns.

Designers took inspiration from other knitted materials—fashion staples like sweaters, socks, and gloves, which are supple and movement-friendly; furniture and car upholstery, which stand up to hours of daily wear and tear. They've spent four years refining machines that can create a complete shoe shape as an outline, without the wasted square around it. The ultimate goal, says Carnes, is to have machines create the entire three-dimensional shoe shape, without any hand-sewing necessary.

Like 3-D printing, shoe-knitting is a self-contained process, one that saves time, money, and energy, and one that can benefit smaller companies, keeping production local to customers. Carnes says sooner or later this technology will be universal. It's already possible to buy a small-scale knitting machine for $60,000. "Maybe it's not home production yet, but we're getting there," he says. "The landscape is changing—that whole idea of having 100,000 workers to do these small processes, in giant facilities, with individual machines, is going away."

Jennifer Beaudry, who covers athletic and outdoor shoe trends for Footwear News, the industry trade magazine, says knit technology could be the culmination of a "big shift" in footwear design. "The knits are possibly the most elegant, most streamlined expression of that," she says. "Using one material, we can engineer it to do all the things that many pieces used to do. This is good not only for consumption, energy use, and waste, but good for the bottom line, which is obviously a good investment."

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Though the high-tech method was created for sports, knitting has opened the floodgates for creativity from a design standpoint, says Mikal Peveto, director of running at Adidas. I met Peveto at Adidas America for a preview of the new Prime Boost running shoe. (It was released in mid-July, marking the first time that Primeknit will be available in the United States, following the nullification of Nike's patent.) While there, I strolled the company's "village"—five brightly-hued buildings designed in a layout that encourages walking between the various offices, cafeteria, and gym, complete with outdoor soccer field. A bus line runs right by the Portland headquarters, and bikes and pedestrians were everywhere. Looking around, it occurred to me that you couldn't invent a better tableau for witnessing the company's designs in action.

The knitted Prime Boost, from Adidas, was released in mid-July. (Courtesy Adidas)

"This knitted process opens up the limited real estate of a shoe to be an unlimited canvas for colors, patterns, and what you can do with a shoe," Peveto told me. On the new shoe, he points out the way a heavy black weave signals where the usual reinforced toe cap would be, knitted continuously into softer, breathable black and white yarn at the top of the foot. A dramatic gradation to red separates the firmer, structured heel from the decorative "three stripes" iconography. The design potential extends directly to lifestyle shoes (the pixelated, street-cool Element Refine, released in April, also uses woven techniques). The combination of Primeknit with Boost—Adidas' immensely popular, light, efficiently-made soles—makes its manufacture easier on resources. Though it's merely a bonus for most customers, Peveto says "it allows us to have a new conversation with people" around sustainability.

"Let's be honest: This is beyond a need-based industry—it's also a desire-based object," says Peveto. "From an aesthetic standpoint, when our style group really gets into it, there's no horizon." Considering that Kanye West is now designing limited edition shoes with Adidas, and quite likely utilizing the Primeknit technology, style will have a big part to play in its continuing popularity.

Nike has already expanded its use of knit into just about every arena: running, soccer, training, even a Flyknit high-top basketball sneaker designed with Kobe Bryant. Though Nike representatives were cagey when I asked them to describe their technology or talk about specific new products on the horizon, the company's broader strategy of using knitted tech across all shoe categories is clear. Tony Bignell, Nike's vice president of footwear innovation, told me that designers are constantly exploring different ways the shoes can be knit together, as well as experimenting with new materials.

"It feels like a big breakthrough," he says. "Looking back in 20 years, maybe we'll laugh at how rudimentary these early designs are—kind of like with the first cars." The depth and breadth of the technology, he adds, is what feels the most promising, and the company has all hands on deck: Engineers with doctorates in biomechanics work alongside graffiti artists and industrial designers. Bignell describes Flyknit as akin to Nike Air cushioning, first introduced in 1987—a foundational technology for the company that would be used in just about everything going forward. "It's a nice trifecta of performance and style and sustainability benefits," says Bignell.

Tony Bignell, Nike's vice president of footwear innovation, describes Flyknit (above, the Racer) as "a nice trifecta of performance and style and sustainability benefits." (Courtesy Nike)

It may also be a big boost to production speed. The current product cycle for footwear—for something that's not a completely new model—is 18 months from design to delivery on the showroom floor. With machines that could produce shoes in North Carolina for customers in North Carolina, using local workers and cutting out global shipping time, knitted technology can allow companies to be more nimble. "We're only at the beginning," says Bignell. "With the reduction in waste, the more we can spread the technology across our categories, the better it is all around. Every sport is asking for how they can move faster, get stronger, stay cooler or warmer, at all ends of the spectrum. The challenge is just moving quickly enough."

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Adidas and Nike aren't alone in recognizing the need for the sustainable shoe. The North Face and Timberland have been environmental leaders with streamlining materials; dozens of smaller companies make shoes with recycled rubber and plastic, water-based glues, and fast-growing natural materials like bamboo, hemp, and cork. A Spanish company called One Moment debuted a biodegradable shoe in 2012; a Hungarian designer took recent inspiration from knit and sewn shoes like moccasins to create DIY shoes that come in three pieces of leather and are easily woven together with a colorful customized shoelace. One startup even designed a minimalist wool sneaker and sold it on Kickstarter.

None of these makers have the market share of Adidas and Nike, or the same-scale energy footprint. And, with the exception of The North Face and Timberland, none of these are likely to be most people's top choice for heavy walking or running—for looks or performance purposes. But the landscape is changing. Beaudry, the industry expert, points out that though a company like Nike has very tight control over its production, almost all factories are shared facilities that work with multiple clients and companies. That communal setting facilitates the cross-pollination of ideas.

Enter challengers like Athletic Propulsion Labs, or APL, a basketball shoe manufacturer that launched its first woven running shoe in June; APL's biggest claim to fame is that its Concept 1 basketball shoes were banned by the NBA in 2010 for giving "unfair competitive advantage" by increasing vertical leap. Its new TechLoom Pro sneaker, designed to rival Flyknit and Primeknit, comes in eye-catching colors like electric purple, blue, and orange.

"We felt that the industry was moving in a certain direction, and we wanted to be at the forefront of that," says co-founder Ryan Goldston, explaining the decision to commit research and development to a knitted upper. "With other materials, you're forced into a position where it's dictating what you can do. With this, you can efficiently create something all from one material, on one machine, and you can be much more creative with it—it's definitely lifestyle, and it works for basketball, training, tennis, soccer, running. It can hold up performance-wise across different disciplines. That's the most exciting part about it." And all of APL's shoes, he adds, are stylish enough to be carried at Saks Fifth Avenue.

Though it began with a patent war, the technology of the knitted shoe is quickly going mainstream. It's the story of innovation: any time something can be done better—and better and cheaper, with less waste—others will pick up on it. "In the very beginning phases, we had knitting as something that was on the forefront, but it has to be something that is eventually universal," Carnes of Adidas says. "It will be the best way to make shoes for our planet, because it has to be."

Back home, as an experiment, I bought myself a pair of retro-cool maroon and white Adidas Campus 80s Primeknits, ordered through a U.K. website, and hopped on the train to work. To be fair, I also picked up a pair of fiery orange and pink Nike Flyknits, and took them for a run along the waterfront near my office in downtown San Francisco. Perhaps the most significant observation to be made about these efficiently made, next-generation shoes is that they felt no different than the sneakers I already have. But out on the street, everyone told me how great they looked.

This article is part of 'The Future of Transportation,' a CityLab series made possible with support from The Rockefeller Foundation.

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