Why Didn’t Saint Laurent’s No-Heel Shoe Break on the Runway? A Physics Professor Explains

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The “physics-defying” shoe at Saint Laurent Fall 2017Photo: REX

I work in fashion and I’m not a “math person,” meaning I’ve failed the subject since my elementary school years, was perpetually stuck in remedial classes, and have been scarred with a pathetic SAT score. But I never really cared: I write and can add one plus one. That’s enough, right? Well, apparently not, if I want to understand the working dynamics of the impossible-looking footwear we saw at yesterday’s Saint Laurent Fall 2017 show.

For Anthony Vaccarello’s second Saint Laurent collection, he released sets of glitzy boots, laden with disco ball mirror chips for that Studio 54 glammed-out effect. But the most head-turning shoes were the most minimalist. No really, there was barely anything to them: A pair of sleek black patent leather heels stepped out onto the runway without a traditional heel. Instead, the angled shank was connected to a decorated heel that lay flat on the ground. Curious as to how it looked on the runway, I texted my colleague who attended the show. “Those looked painful,” she wrote back. When I asked her if they appeared possible to walk in, she flatly replied with: “No. But the models did, so they must be.”

Difficult footwear is nothing new on the runway: Naomi Campbell teetered—and then famously tumbled—in 9-inch-high Vivienne Westwood platform-chopine heels back in 1993. At Marc Jacobs Resort 2017, models looked as if they were walking on a Slip ’N Slide in their shaky heels. There is also Iris van Herpen: The label is known for conceptual shoe creations, which often come sans heels and appear weighty and hefty-looking, making them seem as if they have a relatively solid balance. But those delicate heel-less kicks at Saint Laurent? Their structure looked so thin that I couldn’t understand why the shoe didn’t violently snap from underneath the model’s foot. How did they stay in one piece? And how did that newbie model Aviv Schneider sassily glide in them?

Aviv Schneider walking in the Saint Laurent shoes

To get an educated answer—keep in mind, I have never taken a physics class in my life because I couldn’t pass basic algebra—I emailed Columbia University’s professor and chair of physics, Michael Tuts. “Essentially, the foot exerts a force on the shank. That force is then transmitted to the flat heel, which, in turn, exerts a force on the ground at both ends of the flat heel,” writes Tuts. “In that sense, it is not different from the regular shoe where the foot exerts a force on the shank and the shank exerts a force on the ground through the actual vertical heel and the toe, which is in contact with the ground.”

But would it ever be possible for Vaccarello’s Saint Laurent shoe to fail? Tuts had a few theories and included an illustration explaining how and why the no-heel shoe structure works—and even what could potentially go wrong. “From the physics point of view, there is a safety concern, namely for the new shoe, the bottom piece has to extend past the point where most of the weight is pressing down on the shoe,” he wrote. “If the bottom piece is too short, then you will tip over backward. If the bottom piece is long, then it will be stable.” In other words, the heel and the shank have to be equal in length. The takeaway? Good physics makes a good shoe. And, yes, your teachers were right: You sometimes do need to use math in the real world.

Professor Michael Tut's diagram of how the Saint Laurent “heel-less” shoe worksPhoto: Courtesy of Professor Michael Tuts