Channing Tatum has told how the greatest challenge of playing wrestler Mark Schultz in Foxcatcher was the lack of dialogue.
The 21 Jump Street star spent at least five months training to prepare for his role in Bennett Miller's dark drama, the big-screen adaptation of Olympic wrestling gold medallist Schultz's autobiography, which co-stars Mark Ruffalo and Steve Carell.
Channing's previous films have seen him dance, strip and take part in action stunts, but he revealed at the Toronto International Film Festival that Foxcatcher had been physically challenging in a whole new way.
He explained: "I don't know if I can compare this to Magic Mike, but it's definitely physical. My way into Mark Schultz was physicality - the way he walks, he's a man of very few words.
"Wrestlers talk almost with their bodies. There's a whole language in the way they move and how they compete with each other.
"Mark doesn't talk a lot, so getting a lot across with very little to say, was a bit of a challenge. Mark is a complicated person., you don't know why he is the way he is and you have to sort of go along on the ride with him, It's really what's going on underneath the surface of the story rather than what's actually physically happening."
And he admitted playing a real person felt like a big responsibility.
Channing said: "You're definitely not making it up, you're having to be honest to something that is real, someone that is real who's going to watch this film.
"Mark was so honest with me from day one. From the first conversation that we had he was almost arrestingly honest about everything that he went through in his life. And you go, 'Oh God how am I going to put this man's life into 90 minutes?' And the real answer is you can't so you try to get the essence of who he was."
The Office star Steve Carell makes a rare non-comic turn in the film as paranoid schizophrenic millionaire-turned-murderer John du Pont.
Speaking about this change of direction he said: "I approach things the same way, there's really nothing to lose. I don't do anything to prove anything to anyone. It's fun to take on challenges and see if you can make it work."
But he admitted it had been hard to shake off such a dark character afterwards.
"It was hard to let go of," admitted Steve. "Not to sound too actor-y with it, but yeah it was a very complicated and dark character so it was a little bit hard to let go of it afterwards, but I'm certainly glad I was a part of it."
Mark Ruffalo, who portrayed Channing's screen brother, fellow Olympian Dave, was a competing wrestler himself when he was younger.
He said: "I understood what that life was like and the loneliness and difficulty of that life. Unfortunately I was a right-handed wrester and Dave Schultz is a lefty. So I had to unlearn everything that I'd learned about wrestling, except what it took to be a wrestler, which was invaluable to me."