There's a striking thing about the two-decade progression of running shoes lining the conference table in the Sports Research Lab of New Balance, the footwear company housed in one of the many repurposed textile mills in Lawrence, Massachusetts. Each shoe, each passing year, shrinks – from chunky soles with weights pushing 14 ounces on one end to the new RC 5000 on the other, which at 3.2 ounces is billed as the industry's lightest shoe. Take the laces out and you could mail it first-class with a single stamp.
The RC 5000 marks the latest step in the minimalist running movement, popularized in part by Christopher McDougall's book Born to Run. By some accounts, it was also ushered in when, in 2005, Nike designed and released the Free, a shoe intended to mimic the biomechanics of running barefoot. It had less padding than traditional shoes, and deep grooves in its sole allowed for more flexibility and promoted more foot motion through the strike. The first Free was a modest success; then, in 2006, Vibram introduced Five Fingers, a shoe that featured individual rubber toe pockets. It was originally designed for boaters, and didn't offer much protection, but Vibram found traction with athletes and runners. Because the shoes looked different, minimalism hit public consciousness. "Safe or not, Vibram stimulated the imagination in the running industry and created an opportunity for designers to rethink how they were doing things," says Brooks Sports Design Director Rich Zartman.
That "rethink" – as seen at New Balance in the creation of the RC 5000 – required designers and engineers to mix new materials, processes, and design techniques to get the shoe down to its radical weight. The RC 5000's sole, for example, is not the uniform 6mm-thick wedge found on the previous years' shoes on the table; instead, near the front of the shoe there are small, strategically placed rubber nubs attached to a thin film. "The outsole on this," says design manager JF Fullum, waving a shoe from a few years back, "is heavier than the whole shoe here." Instead of stitching and raised overlays of differing materials, the RC 5000 consists of ultralight, nearly translucent synthetic fabrics (including a slightly raised "structural" web of sorts on the exterior) that are heat-laminated together with an air mesh. The only visible seam is at the heel. This relentless subtraction can be seen in other New Balance shoes. The company's Minimus line of trail-running shoes uses a Vibram "T-Lite" sole – a collection of interconnected rubber "lugs" that look like a molecular model. The designers scrapped anything that wasn't strictly essential. "We looked at all the wear tests to see where people were actually using the rubber," says Sean Murphy, an engineering manager in advanced products. They studied the shoes in their research lab, complete with motion-capture sensors, a glass measuring plate in the floor (a window onto what's happening on the soles of shoes). Where runners weren't hitting, the lugs were removed.
And yet, for all the innovation, the tide of tradition can still hold sway. Take laces. "We've all tried to revolutionize that," jokes Stephen Brown, a product developer. "Slipper fits, sock fits." A special knotty lace was employed that tended to untie itself less. "Everyone in the industry has tried to drop laces," adds Fullum. "But you always go back."
In a room upstairs sits what may be the future of shoes: a 3D printer that spits out a shoe model in resin. It's easy to imagine a time when a runner's foot is laser-scanned – New Balance already has such a device to measure how elite athletes' feet change during the course of an event – and the data used to instantly churn out a precisely calibrated shoe, laces and all.
How a Better Running Shoe is Built with Less
"The 1990s were the dark ages of shoe design," says JF Fullum, head of New Balance's Design Innovation Studio. Manufacturers were adding foam, rubber, polyurethane, and plastic under the foot to control a runner's stride and create a more comfortable ride. "Now we're thinking about how the foot really moves," Fullum says. In 2012, there's a drive to build shoes with less, allowing feet to move uninhibitedly and stabilize based on more direct contact with the ground. That can be accomplished only with modern materials that are considerably lighter, stronger, and more flexible. Take the M890 V2, above: Its midsole foam is 30 percent lighter than traditional midsole cushioning but also more supple and responsive than its 1992 forebear, the M997. Most shoes in 1992 had robustly cushioned heels that were accentuated by a steep heel-to-toe drop (a 12mm-17mm height differential between where the heel and toes rest in the shoe), while this year's M890 V2 has a moderate slope (8mm) that enables a more efficient midfoot gait.