Jake Gyllenhaal Reveals His Grueling Boxing Training for 'Southpaw' in New Exclusive Clip

The actor trained for eight months to play a boxer in the July drama

Photo: Scott Garfield/The Weinstein Company

Jake Gyllenhaal‘s remarkable transformation into fictional boxer Billy Hope for the upcoming drama Southpaw didn’t just happen overnight – the actor underwent intense training for eight months to gain the body and mindset of a fighter.

In an exclusive behind-the-scenes clip, Gyllenhaal, along with the movie’s director, Antoine Fuqua (best known for Training Day), opens up about his jaw-dropping new physique, and the work that went into it.

“I knew nothing about boxing when I started really, and I knew that in order for me to pull it off in any way, I was just gonna have to learn to do it,” the actor, 34, says. “And when I set my mind to something I just won’t stop until I do it. It’s something I pride myself on, and it’s something I hate about myself.”

Fuqua, who trained with the star to help motivate him, says he told Gyllenhaal he needed him to not only portray a boxer, but also to become one.

“I was starting to see him get his own swagger, getting his own rhythm as a fighter,” Fuqua says in the clip.

Gyllenhaal’s trainer, Terry Claybon, says he had to start from the bottom with the star as he had no previous boxing experience.

“We started off from the ground level – he didn’t know anything,” Claybon says. “He had no boxing experience so whenever I start a fighter off, I’m always starting them off as if they want to be a professional fighter.”

Jake Gyllenhaal’s Changing Looks

In addition to boxing basics, Gyllenhaal was also subjected to intense strength training. His daily routine included flipping and hitting a 300-pound tractor tire and doing 1,000 situps a day.

“Jake is really, really dedicated to his training,” says Claybon. “He was always on time, he was always the one who wanted more. He was always seeking more knowledge.”

Gyllenhaal, who gained 15 pounds of muscle throughout the process, is still a regular at the boxing gym, according to the trainer.

“He was up there fighting to prove that he can pull this movie off and do a good job,” said Clayton. “And he did.”

Southpaw hits theaters July 24.

• Reporting by Ana Calderone