The 31-year-old actor says his difficult workouts are a thing of the past.
He told the September issue of Details magazine: "I haven`t cycled in a long time. I don`t run anymore. Do I take care of my body and take conditioning seriously? Yes. But exercisingregularly doesn`t fit the energy of the character I`m playing now." he says of An Enemy, in which he plays a man who seeks out his look-alike.
Jake says he`s become a different man since he shot the police thriller `End of Watch`, directed by David Ayer.
He continued: "Dave told me right off that this was going to affect my soul. `Friends are going to say, That`s the Jake I`ve always known, but somewhere deep inside, you`ll know otherwise.`"
Jake recalled about his preparation for the job: "[We had] fight training every morning at a Kenbo Karate dojo, and I got the s**t kicked out of me. Then [we went to] the shooting range, shooting past each other`s heads, with live ammo.
"There`s a simulated fire in the movie, but Dave wanted us to feel what that`s like, so he had us do a controlled burn."
Jake says the film - released September 28 - inspired him to go with his gut.
He revealed: "Every journey starts with fear. And I could say that`s what I want to embrace now. A real experience. And I want, overall, to trust what I know is right. There have been many times when I haven`t. It`s what I`m asking myself: Where is the line? What is the line? There`s so much context, it can be almost impossible to find."