TIFF 2016: Brie Larson's Free Fire shoot left her covered in bruises

Brie Larson’s next role is pretty far from her best actress-winning turn from last year’s Room. In Ben Wheatley’s new shoot-’em-up thriller Free Fire, Larson plays the lone woman among a group of trigger happy thieves and ne’er-do-wells.

“There’s actually not a ton of dialogue, it’s more physical than anything else,” Larson, 26, said at the PEOPLE / EW / InStyle Portrait Studio in Toronto, where Free Fire premiered as part of the Toronto International Film Festival’s Midnight Madness section on Thursday night.

As Larson explained, the physical embodiment of playing the role became really important, as her character gets shot in the leg early in the film. “For the following month, everyday I was crawling on the floor that had tons of rocks and things on it,” Larson said. “So I had to sort of figure out, because I had one arm that’s bad too, you’re just sort of scooting and lifting your butt up and slamming it back down. You’re trying to crawl for your life.”

But the result of that commitment to authenticity? A bunch of terrible black-and-blue marks.

“I slowly got the most disgusting and intense bruises all up one side of my leg,” Larson said. “It became progressively more and more painful and more and more awful looking. My job is so weird. This is what I’m doing. How do I explain this to people?”

Free Fire also stars Armie Hammer, Sharlto Copley, Jack Reynor, Sam Riley, and Cillian Murphy. A24 will release Wheatley’s film in theaters next year.