When James McAvoy showed up in the M. Night Shyamalan thriller 'Split' in 2016, his muscular frame might have been as surprising to the audience as the movie's twists and reveals. The actor didn't just look big as The Beast—compared to his typical physique, he was massive. For the sequel (or trilogy-capper, depending on how you look at it), 2019's 'Glass', McAvoy looked even more imposing in the role. 

That bulk didn't show up overnight. McAvoy worked with trainer Magnus Lygdback to pack on the pounds and crate the movement patterns that made the animalistic character even more unsettling. "We had about three months to pack on as much muscle mass as possible to make him look as freakish as possible," Lygdbeck told Men's Health when we met up at Ultra Body Fitness in L.A. to walk through one of the workouts he used during their prep.