Charlie Hunnam who plays Percy Fawcett arrives at The Lost City of Z UK premiere on February 16, 2017 in London, United Kingdom. Credit: Paul Cunningham - Corbis/Corbis via Getty Images

Sounds like something Christian Grey might say. Charlie Hunnam doesn't just hit the gym to work out. The Sons of Anarchy actor revealed that he also stays in shape by having lots of sex.

"I try to do it all. I also try to make love as often as I can. That's an important part of fitness. There's no reason you can't be active at 70. I want to run up mountains at that age," Hunnam, 36, told Men's Health in a new interview. "We are supposed to be very active animals. It's our DNA. Sweating is how I change my oil every day. I just feel happier, more positive, energized, and disciplined if I work out. … I train a lot every day because I'm f--king crazy."

Hunnam has been dating jewelry designer Morgana McNeils for 11 years. The couple currently reside in a $2.76 million pad in the Hollywood Hills.

The hunky actor, who will next star in Papillon, says that he's "interested in having a high fitness level across the board." He also enjoys running, swimming, hiking, jumping rope and taking part in Brazilian jiu-jitsu. He more recently worked out "like a mother--ker" to put on 20 pounds of muscle to play King Arthur in the upcoming Guy Ritchie-directed film, King Arthur: Legend of the Sword.

"When you're training every day in a combat discipline, it just gives you that eye of the tiger," Hunnam, who weighs 165 pounds, told the mag. "Then if someone acts aggressively toward you, I can run all the scenarios through my head — you know, like I'm going to step to the side and put an elbow through your face."

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