From the moment the first images of Jake Gyllenhaal at UFC 285 hit the internet, fans marveled at the physical transformation he made for his role as Dalton, the MMA-fighter-turned-super bouncer leading the new Prime Video reimagining of '80s cult classic Road House.

Gyllenhaal hit the Octagon in the most shredded shape the world has seen him over a 20-plus year Hollywood career, with abs that jut out from his stomach like the molded torso of a kids' superhero costume. The physique tune-up clearly took time and effort, so the real question to ask is how he managed to pack on so much muscle while cutting down to an absurd level of leanness.

Jason Walsh, Gyllenhaal's longtime trainer, has the answers.