Jake Gyllenhaal "wakes up" when he's hit in the face.
The 'Southpaw' actor - who stars as a boxer in his latest movie - has admitted he didn't mind being punched for his role.
He said: "I got hit pretty hard in the face. All the producers ran [over]. I don't think out of real worry for me, but just the fact that we were only two weeks into shooting.
"There is something jarring about being hit in the face. I don't know how to explain it. It wakes me up."
Whilst the 34-year-old star understands it would be "initial instinct" to move away, he learnt moving towards his aggressor was the right course of action.
He explained: "Your initial instinct is to lean out. It's the instinct to lean in that took me five months.
"Hitting someone - I don't have as much of a problem with that."
Meanwhile, Jake's co-star Rachel McAdams - who watched the Hollywood star get "pummelled" during filming - has admitted she was "very worried" about him.
She told Details magazine: "They were always playing hardball - there was never any letting up.
"I was very worried for him, but I knew he had it under control."