When the first images and clips from director Paul W.S. Anderson's "Pompeii" appeared last year, the exploding fury of Mount Vesuvius was overshadowed by actor Kit Harington's abs. 

"On a practical level, I’m playing a gladiator and they were very, very fit men and they were fighters and they had to look a certain way and be a certain way and I thought I’d be doing the story an injustice if I didn’t go to the gym quite a bit,” he told Access Hollywood. “And then it becomes obsessional. Once you go along that path, it’s hard to slow down."

Harington, who plays the character of Jon Snow on HBO's hit series "Game of Thrones," says that proper nutrition was both the focus and the most difficult part of the process. 

"It’s 70 percent diet and 30 percent working out and you get into a regime and you just keep going,” he said. “It’s tough to start with. … You then have to maintain it throughout the film. … It’s not eating bad things, which is the hardest [part]."

The 27-year-old also revealed that he and co-star Adewale Akinnuoye-Agbaje went through a month-long "gladiator boot camp" prior to shooting that included four-hour workouts. 

“That involved four weeks prior to the movie’s starting, of going to this room with our wonderful stunt people and training very hard every day, and learning swordfights with one sword, and two swords,” he told Vanity Fair. According to Akinnuoye-Agbaje, the pair were also placed on a restrictive 1,800 calorie diet “designed specifically for our bodies to be attuned to lose fat and pop out muscles."

"Pompeii" hits theaters on February 21st. Check out a trailer below. 

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