The first thing I warned Mandy Lieveld about is that I hunch like a female Bernie Sanders. “When I walk in heels, it’s like I’m bending under gravity,” I told her. Lieveld, a former model who instructs others in how to traverse the gantlets known as “runways” in fashion shows, seemed undaunted.Lieveld’s job is to teach models — and non-models — how to stride the runway with confidence. She is something of an haute strut savant, transforming gaits from awkward baby-deer steps into militant marches for brands such as Michael Kors, Versace and Bottega Veneta.I learned of Lieveld, 40, through the author Zoe Dubno, who was tapped to walk in Rachel Scott’s inaugural Proenza Schouler show in February. Though flattered, Dubno felt a bubbling panic.“I have kind of a Groucho Marx walk,” Dubno said. Worst of all, she would have to walk in heels — which she considered vertiginous torture devices otherwise reserved for hobbling around her brother’s wedding.The casting team at Proenza Schouler hired Lieveld, and after two days of coaching, she transformed Dubno’s gait from a comedian’s clomp to a supermodel’s stroll.I was intrigued. Could I benefit from the Lieveld treatment? Could she rectify my (undiagnosed but long suspected) scoliosis and transform my slouching-toward-Key Food thud? I booked a 90-minute lesson ($750 for one-on-one coaching) with the posture whisperer in midtown Manhattan.Story continues below this adArmed with a pair of 3.3-inch silver Jimmy Choo heels, I arrived at a cheery, mirrored room that Lieveld rents on the 16th floor of the Ripley-Grier Studios, a rehearsal space that is forever teeming with Broadway hopefuls.Immediately, she instructed me to open my chest, as if “there is sunshine” that I am greeting with my body. She frequently used the word “relax.” She adjusted my shoulders, which lessened the tension between my shoulder blades. She spoke about her methodology of “CNS” qualities — that’s “confident, natural and strong” — that she says modeling agencies and casting directors are often looking for in their models.Lieveld, who is from the Netherlands, has been working as a walking coach for over 10 years. At 6-foot-1, Lieveld was tall, even for the Dutch. As a teenager, people began to comment that she should become a model.“I started with modeling, and I thought, ‘Wow, we have to do all these things, and nobody was teaching you how to do it,’” she said. “So that was in the back of my mind.” Eventually, Lieveld entered a dance academy, where she practiced ballet and modern jazz, and learned more about the power of poise.Story continues below this adHer dance career was stopped short when, at 21, she was diagnosed with myasthenia gravis, a muscular disease that almost paralyzed her. “It makes you realize that you have to do the things in life that you love,” she said.She entered the University of Amsterdam, where she majored in psychology. “I realized that’s really good for models because you need confidence: You deal with rejections,” Lieveld said of the benefits of studying the human mind. “So I finished my bachelor’s and then my master’s, and then I was like: ‘You know what? I’m just going to try to be a model coach.’”On the runway, a single misstep can be devastating. And the way we walk says a lot about who we are and how we feel. Nicole Maleh, a clinical psychologist in Westchester, New York, said that adolescents often slouch purposely, to hide themselves, while adults slouch unconsciously. “It’s like: ‘I don’t want to get in the way. I don’t want people to interact with me. I just want to go on and go on about my day,’” she said.Maleh also chalks up our views of walking up to evolution. “Imagine a community of apes living in the jungle,” she said. “The alpha male stands up with his chest puffed out. His gait is really confined, and he takes big steps, but they’re very measured. Whereas if you see the general community, their arms are swinging around and they’re acting a little more goofy.”Story continues below this adBut no ape population has ever had to deal with the very specific hardship of walking a runway in shoes that are a size too small. Lieveld offers tricks for everyday scenarios and helpful mnemonics to deal with catwalk variables and help her models feel comfortable. Throughout our lesson, she often said, “splash, splash, splash,” to describe the way to imagine your foot hitting the floor: as if splashing in a puddle. “It’s not really ‘stamping,’ she said, “but it’s more the energy.”There were other colorful tips, like her declaration that “the core is the engine of your walk.” She advised me to tighten the engine of my own walk if ever I’m feeling wobbly in heels. “You can still breathe, you can still talk, but it’s just that contraction makes it feel more stable,” she added. At one point, Lieveld gave me an umbrella to shimmy behind my back and between my arms, a trick sometimes used in horse riding. The placement opened up my chest and felt quite nice, a gentle lumbar stretch.To nail the stern “Blue Steel” facial expression, she tells her models to pretend as if they have two laser beams coming out of their eyes. “It’s like if somebody looks at you and think, ‘I know your secrets,’” she said.At the end of the session, Lieveld showed me the “before and after” videos she had recorded. The slump has been exorcised from my spine. Now I walk erect, with a snappy supermodel stomp — and in heels, no less! My motion has purpose. There is one more question, though: What about falling?Story continues below this ad“Sometimes,” she said, “the biggest advice is just get up and get yourself out there again.”This article originally appeared in The New York Times.