Jake Gyllenhaal slept for 14 hours after finishing 'Southpaw'.

The 34-year-old actor - who stars as Billy 'The Great' Hope, the reigning junior middleweight boxing champion, in the new movie - has revealed how the energy-sapping role caused him to feel physically and mentally exhausted.

Jake recalled: ''It was 5am in New York City when we wrapped.

''We'd shot way into the night and I still had my prosthetics on. Usually they are carefully removed, but this time I literally ripped them off, like Arnold Schwarzenegger tearing his face off in 'Total Recall'.

''I then went home and fell asleep for 14 hours, the first time I've done that since I was 16 years old.''

Jake underwent an intense fitness regime for the role, which included doing 2,000 press-ups a day and a five-mile run, and admitted he was worried he wouldn't look convincing in the ring.

He told the Independent newspaper: ''I had five months to learn, and I know that it takes me a long time to learn a skill, and also to come across like I've been doing it since I was six years old.

''Therefore, I decided to train twice a day so it would give me an advantage, and it would seem like 10 months of training. It's difficult for me to use words like hard or miserable when I'm talking about a movie where really I feel grateful for the opportunity.''