United Kingdom, Aug. 26 -- Dwayne 'The Rock' Johnson "ripped open" trauma from his past to play MMA star Mark Kerr.

The wrestler-turned-movie star has revealed he had to "tap into" painful memories to portray the troubled athlete in new sports drama The Smashing Machine and he found the experience both "scary" and "freeing".

Johnson, 53, told Vanity Fair magazine: "You have to be willing to tap into all the stuff that you've gone through, and this was stuff that I had not explored on camera or otherwise.

"I'm not a big therapy person, even though I'm an advocate for whatever it is you need. I found it so scary, but also, so nourishing and freeing. I ripped it open."

The Smashing Machine tells the story of Kerr's rise to fame and his b...