MTV – Shailene Woodley and Theo James did use talented stunt doubles for some scenes in their new movie, “Divergent,” an adaptation of a YA novel set in dystopian future Chicago, but in a lot of the action sequences were filmed by the actors themselves. That’s thanks in part to the realistic approach director Neil Burger took to the movie.

“I can say as a director that both of these guys brought such strength to the action. There’s a lot of fighting in the movie,” Burger told MTV News at San Diego Comic-Con. In the Chicago of “Divergent,” society is divided into five factions based on personality traits like intelligence and honesty. Woodley’s Tris is a teenage girl who transfers from her home faction of Abnegation (selfless) to Dauntless (fearless). James plays her Dauntless mentor (turned-love interest), which means the two of them spent plenty of time training and fighting together.

“I say that Theo’s kind of a combination of Paul Newman and Bruce Lee. He can really fight,” Burger said. “Shai is not scared of anything and also did some fighting. [She] climbed on top of all sorts of crazy things — 75-foot tall ledges — and did all sorts of crazy stuff. I was trying to keep everything as real as possible, which made them have to be involved in everything and do it for real — and they did it.”

Woodley said that one of her favorite scenes to shoot involved a huge fight sequence during the climax of the movie. “Toward the end of the film there’s a really big scene where Tris and Four engage in a big fight,” she explained. “The way that the stunt coordinator and Neil created that in the way that [author] Veronica [Roth] wrote it in the book was really beautiful. Theo kicked ass in that scene so I’m excited to see it.”

Adds James, “So did Shai. She’s like a natural athlete even though she pretends not to be.”

“Well, my stunt double is really great,” Woodley demurs. “To be fair, she did most of that scene.”

“Divergent” hits theaters March 21, 2014.