The 49-year-old actor portrays Marcus Acacius in the long-awaited sequel and though he insisted he wasn't ordered to get in shape for the film, he wanted to be in good physical condition to avoid injury.
And while Pascal got "stronger than [he's] ever been" as a result, he admitted his plan "didn't work".
Told how co-star Paul Mescal, 28, had said training for the movie was fun, Pedro responded to Entertainment Tonight: "Yeah, I bet it was. I bet it was fun for him. Maybe it would've been fun for me too, if I was 20 years younger.
"I was in no single directive from the movie to get in any kind of shape, but I did. Mainly so that I wouldn't get hurt, and it didn't work. I got hurt anyway.
"I got stronger than I've ever been just so that I can play the character, really."
The former Game of Thrones actor admitted his natural fitness levels have changed as he's gotten older so he wanted to make sure he could push himself.
He added: "I'm definitely getting to the point where I can't just wake up and do stuff like that, so I got ready for that.
"I used to be able to wake up and do that stuff, but things have changed and so I knew I wanted to be able to do those things.
"I trained, and rehearsed obviously, a lot, to be able to do it."
Mescal recently explained he wanted to look "big and strong" in the movie.
He told Entertainment Tonight: "I just wanted to be big and strong and look like somebody who can cause a bit of damage when s*** hits the fan.
"I think also, sometimes, one could, in striving for that perfect look, end up looking more like an underwear model than a warrior.
"Muscles start to grow, and that can be deemed aesthetic in certain capacities, but there is something about feeling strong in your body that elicits just a different feeling.
"You carry yourself differently. It has an impact on you psychologically in a way that is useful for the film."
21°C