Dancer Kurt Froman (Movin’ Out) was sitting on his couch nursing a sprained ankle, sidelined from his major job with Tony-winning choreographer Twyla Tharp, when ballet choreographer Benjamin Millepied sent him a Facebook message: “Would you be available to start training two actresses for a Darren Aronofsky film?”

Suddenly, Froman shifted from performer to ballet trainer to the stars, his first gig the high-profile Black Swan working with Mila Kunis and Natalie Portman—the latter of whom went on to win the Academy Award for her work in the film.

“[Benjamin] needed someone who he trusted to train them and partner them, and be a go-between,” says Froman. “He knew that I was such a fan of [director] Darren Aronofsky’s work that I would have an understanding of Darren’s visual style and what his needs were, so it was kind of a perfect opportunity.”

Froman began training the women in September 2009 for a shoot start of December 2009; he worked with them four hours a day every day, teaching them basic ballet technique and training them for the movie’s specific and intricate dance sequences.

While movies often use dance doubles, as Black Swan did, it’s still crucial for actors to be able to perform as much of the dance as possible to minimize the need for heavy editing, to smooth transitions within that editing, and to create authenticity.

“If it’s an actress who has less experience dancing, most often the easiest thing to achieve is making their upper body look as perfect as possible,” says Froman.

But with Froman’s latest project, Red Sparrow starring Jennifer Lawrence, director Francis Lawrence insisted she execute 100 percent of the dance. “Francis Lawrence really was adamant from the start that Jennifer Lawrence has to be able to follow the footprint onstage for lighting purposes, as well as editing purposes,” says Froman. Even Froman was unsure that Lawrence (or anyone without prior training) would be able to do the fast solo material due to its complexity. But “she completely mastered every single bit of that material. She did every single section—the solo included,” says Froman. “It’s amazing what, in four months, an actor can achieve.”

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And Froman’s domain extends beyond dance sequences. Audiences need to believe these actors are ballerinas, even when they’re not dancing. “One of the biggest things, I think, for a non-dancer is just understanding dancers hold their arms from their backs,” Froman explains. “When I was working with Jen, as well as with Mila and Natalie, getting them used to holding their backs that way and understanding that their arms are an extension of their backs, that’s the first thing that I need to instill in them and I have to remind them of that the entire time. I would constantly have my fingers between [Jen’s] shoulder blades so that she would squeeze my fingers.”

Froman squeezes years of muscle memory into four months—hence the need for daily training.

But the ballet trainer works on more than the physical. He helps these actors enter the psyche of a dancer. “Giving them some background of what—especially female—dancers go through, so that all that character work is there” is part of his job. “On top of that [I teach them] what the ballet is about. So you’re giving them a ton of background material so that they understand what it’s like to be a modern ballet dancer, as well as how they would approach their choreography, as well as getting their body to respond.”

As a trainer, Froman’s experiences range from teaching non-dancers intense choreography on films like Red Sparrow and television shows like Z: The Beginning of Everything to coaching the young boys of Billy Elliot the Musical to working privately with Oscar nominee Rooney Mara to help her feel more comfortable in her own skin before playing a rock musician.

“On my first gig I thought, ‘This is the coolest experience. I’ll never have another opportunity to do something like this so take it all in,’” Froman remembers. “But if you have a good reputation, people start thinking of you as the go-to person to get an actor in shape or actor to feel comfortable dancing or moving to music or even just comfortable in their own body. There’s a real need for someone like me to be involved in the film industry.”

Time for you to learn a snippet of choreography. Watch the video below to learn a piece from Broadway’s The Great Comet!