The Rock describes difficult transformation for ‘The Smashing Machine’ role

Dwayne “The Rock” Johnson stopped by “The Tonight Show” last night to promote his new movie.

“The Smashing Machine” — with Johnson playing the lead role of MMA legend Mark Kerr — will be released in theaters this Friday (October 3). Johnson has received praise, and even potential Oscar buzz, for his performance. He told Jimmy Fallon that the role required him to transform in a variety of different ways to play the muscular but soft-spoken Kerr.

“We had a physical transformation, and certainly an emotional transformation, and a vocal transformation too as well.”

“It was about 22 prosthetics,” Johnson said. “I had to put on just over 30 pounds of muscle. Which, by the way, what you realize is — you know how you have some actors who say, ‘Hey, I had to put on weight. I went to McDonald’s every day.’ Mark Kerr had just this quality of muscle, like fast-twitch quality of muscle — because he was a [freestyle] wrestler. And I had to still put on this weight, still be able to move like an MMA fighter.”

Johnson described the conversation where director Benny Safdie told him that he’d need to add muscle for the role.

“He said to me, ‘Hey DJ, I don’t know how to tell you this and I don’t know if you’ve ever heard this.’ He goes, ‘You’re going to have to get bigger.’ And I go, ‘Okay, here we go,'” Johnson said.

Now, Johnson has gone in the opposite direction and slimmed down for his next project with Safdie. Johnson will star in the movie “Lizard Music,” playing a man in his 70s whose best friend is a chicken.

Johnson’s full “Tonight Show” appearance can be watched below: