Back when "Man of Steel" was still filming, most people had no idea who Henry Cavill was. Sure, you could look him up on IMDb, but seeing that he was in "Stardust" or "The Tudors" wasn't enough to help you imagine him as Superman. Then we saw the pictures.

Not that first official image of him in the update suit in front of the bank vault. We're talking about the paparazzi photos of Cavill, post-oil rig sequence, bearded, in raggedy pants and shirtless. That's when it clicked for a lot of people.

And as we learn in an exclusive featurette from the upcoming Blu-ray release of "Man of Steel," that level of super-human fitness wasn't easy to come by. Cavill took on a rigorous work-out routine that didn't always leave him feeling invisible. As he describes in the clip from the home video release, getting into shape was all about pushing him far enough to feel physically drained, but not bad enough to never come back.

It was cast trainer Mark Twight who put Cavill through his paces and turned him into Superman. "Mark is probably one of the most incredible people I have ever met," Cavil said. "The things he has helped me achieve -- I can only speak for myself, really -- but he has opened my eyes to seeing past what I thought were my limits, the ability the crush me in the gym just enough that I can't walk out properly and I feel horrible and feel a little sick, but I still want to come back."

"Man of Steel" is available on Blu-ray and DVD now.