Actor Jake Gyllenhaal received a daily beating from teenagers in martial arts training while preparing for new film End Of Watch.

The Brokeback Mountain hunk had to undergo a gruelling exercise regime to bulk up for movie, in which he and co-star Michael Pena play cops who become targets for gangsters after confiscating money and guns from a notorious cartel during a routine traffic stop.

Gyllenhaal spent months hitting the gym to get in shape, but he was still no match for the youngsters he had to go up against while at a Kenpo karate school in Los Angeles.

He says, "Five days a week we would go to Echo Park to this dojo run by the best friend of David Ayer, the writer/director, and Michael and I would fight these 14 to 20-year-old kids. I don't even have a fight scene in the movie but the director wanted me to get into that attitude of what it was like to get beaten up or get into a fight.

"We simulated that every morning so I was constantly sore and in pain getting hit in the face and body. So, for five months before I started shooting, I had the c**p beat out of me."

The fight training wasn't the only part of the movie preparation that hurt - the actor recently revealed he was zapped by a stun gun as part of a painful bonding experience with the rest of the cast.

He and Pena also spent five months on the mean streets of Los Angeles with police partners and the sheriff's department, working a 12-hour night shift three times a week to get into character as crack cops.

He tells WENN, "It took a while to create that trust but by the time it came to make the movie in 22 days for $7 million we had enough training. It was an intense process because we had little resources and little time but we had so much experience in training for five months that making the movie paled in comparison to that.

"The experience on the street in the south end of Los Angeles with the police officers that do this job every day of their lives was incredibly intense and it changed my life and put everything into perspective."