Michael Fassbender clearly took us up on our Assassin’s Creed workout program. The first trailer from the upcoming Assassin’s Creed action film was recently released and people are already talking about Michael Fassbender’s “buff” physique. So how can us mere unfuturistic mortals pull off some of those leaps and bounds? We spoke to the game developers Mike Mennillo and Mohamed Gambouz and, as it turns out, Assassin’s Creed ‘s character movement is more realistic than you might think. 

“We take a lot of references from parkour athletes,” Art Director Mohamed Gambouz explained. “It makes [the characters] more believable and we try to follow that same kind of silhouette and build for the models.”

Mennillo went on to tell us the secret to moving like an assassin. You absolutely HAVE to train legs. “Assassins don’t skip leg day,” Mennillo jokes. “They do a lot of leg training; we have a lot of stuff with the whole wall climbing system, the whole leaping and grabbing objects to swing. It’s very intensive so they need upper body strength, but the biggest thing—because they’re always jumping, they need the grip and the legs.”

The Assassin’s Creed movie will hit theaters nationwide this December.