Ben Foster has always been a method actor. He tells The Guardian that for Lone Survivor he ate dirt to understand the Navy Seal–in-Afghanistan experience. For Alpha Dog he used glaucoma medication in his eyes to approximate the look of crystal-meth addiction. And for a brief appearance as a homeless veteran in Rampart he lived on the streets of Los Angeles “pissing my pants like everyone else.” So maybe, knowing that history, it’s not surprising that Foster experimented with performance-enhancing drugs in order to play disgraced cyclist Lance Armstrong in the upcoming film The Program.

“I don’t want to talk about the names of the drugs I took,” he told The Guardian cautiously. “Even discussing it feels tricky because it isn’t something I’d recommend to fellow actors. These are very serious chemicals and they affect your body in real ways. For my own investigation it was important for me privately to understand it. And they work.” For the record, in 2013 Armstrong admitted to using E.P.O., testosterone, cortisone, human growth hormone, illegal blood transfusions, and other blood doping. The admission earned him a lifetime ban from the sport and he was stripped of all seven Tour De France titles.

Foster also did body work to emulate Armstrong’s distinct riding style, going so far as to reference computer-captured aerodynamics of Armstrong’s body “so I could get the hump in the back, the heels slightly out. It’s almost a duck pedal. It’s not a delicate ride. It’s violent, which is also why he’s such an exciting rider. It’s like he wants to break the bike.”

It’s one thing to copy someone’s body, but Foster was also intent on understanding Armstrong’s mind. And that pursuit came with a cost. “There’s a fallout,” he said. “Doping affects your mind. It doesn’t make you feel high. There are [behaviors] when you’ve got those chemicals running through your body that serve you on the bike but which, when you’re not. . . . 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 certainly isn’t the first intense actor to go to extremes for a role: Robert De Niro’s taxi-driving stint, Christian Bale’s drastic weight fluctuations, and Daniel Day-Lewis’s many, many experiments have all yielded award-winning performances. But there’s no evidence of anything quite this extreme in their history. At least not that they’ve admitted to.

Foster says he does have a line he won’t cross. When preparing for Alpha Dog, he wasn’t quite willing to dabble in crystal meth. He explained, “In all transparency, I rolled with those guys on Alpha Dog and I bought their drugs but you have to ask yourself how far you can go and still come back. I had been losing friends to crystal meth. The proximity to it was enough that I didn’t need to take that door.”

Foster’s next project is a complete 180 from the grim reality of Lance Armstrong. “I get to play a motherfucking wizard!” he said of his role in the upcoming video-game film Warcraft. “Walking in what is ostensibly a dress, with a staff, a wig and press-on nails, presents different challenges to riding a bicycle. Especially when you’re trying to open a Coke.” We can’t wait to hear what method experiments he tried for that role.