Lance Armstrong actor took performance-enhancing drugs for 'The Program' role

Ben Foster’s character research involved doping, which he stressed not only worked but also affected his mental state.

Disgraced cyclist Armstrong was stripped of his seven Tour de France titles in 2012 and, after years of denials, confessed to doping at the turn of 2013.

"For my investigation it was important for me privately to understand it. And they work," Foster told The Guardian. "Even discussing it feels tricky because it isn't something I'd recommend to fellow actors."

Foster declined to reveal which drugs he had taken, but claimed he had only just recovered from the ordeal.

"There’s a fallout,” he said. “Doping affects your mind. It doesn’t make you feel high. I’ve only just recovered physically. I’m only now getting my levels back.

"I don’t know how to separate the chemical influence from the psychological attachment I had to the character. If it’s working, it keeps you up at night. This is losing your marbles, right? They’re definitely rolling around. They’re under the couch but they’re retrievable.”

Foster, who was refused a meeting with Armstrong after landing the part, was torn on his opinion of the American.

"On one hand, he’s a lying doper who tricked the world," he said. "On the other, he’s a young man who faced cancer. It changes you. And when you go to war it changes you. That’s what Lance did – he went to war with his body. That shifts your consciousness.

"He started training within a culture that was doping: you’d have to go down 18 riders to find a clean one. He survives death, the story catches fire and he recognises that.

"He’s a smart man. He says, ‘I can do some good with this.’ He raised half a billion for cancer research. We just don’t like him because he was Jesus Christ on a bicycle. We’re mad he came back from the dead, saved the sick and then turned out to be full of shit. And we’re punishing him because he didn’t apologise in the way we’d like. Americans love a good apology. He wouldn’t do that."