Danny Boyle pushed James Franco to the limits on the set of their latest film - asking him to work seven days a week.
127 Hours is based on the true story of Aron Ralston, played by James, an American mountain climber who amputated his own arm to free himself after being trapped by a boulder for nearly five days in 2003.
Speaking at the Toronto Film Festival, the Oscar-winning filmmaker talked about the challenges he had making it.
"Obviously the film is incredibly inert in one sense and I thought it would be absolutely catastrophic if it felt inert, so we had this byword that we all talked about, that it was an action movie about a guy who can't move.
"I tried to get James to work seven days a week," he revealed.
"We'd force everyone to keep working and pushing, pushing, pushing in the hope that that would bleed into the film, that sense of restlessness," Danny said.
The Slumdog Millionaire director went on: "We had this idea which I tried to convey to all the actors really, certainly all the crew, that we would make the film at a tremendous pace.
"I believed it would affect the texture of the film, the feeling of the film."