It's in the trailer, the beginning of it, where I stand up and punch the glass out and then I leap out the window and fly through the air. And on the first take of that, it's this big epic punch and a leap through the air,

Corenswet's physical trainer breaks down the routine that helped the formerly svelte actor put on 40 pounds of muscle—and how he got Nicholas Hoult prepped for Lex Luthor.