Hardy did not do 2,500 push-ups a day to prepare for Bronson.

Contrary to popular belief, Tom Hardy did not do 2,500 push-ups a day in preparation for the role of Bronson. The confusion and reason for this rumor is that Charlie Bronson himself was the one doing 2,500 push-ups a day around the time Hardy was meeting with him to gather information for the film script. Hardy himself denied this rumor during an interview in late 2009 with Michael Slenke from Interview Magazine:

SLENSKE: But you were doing some crazy training for that too, like 2500 push-ups a day?

HARDY: No, Charlie does 2500 push-ups a day, I didn't do that. I had to put on a lot of weight as quick as possible and I only had five weeks to do it, and a lot of that was fat. I ate everything. To be honest, I lost about 14 pounds of fat on this last film, and gained 28 pounds of muscle. I was heavier than I was on Bronson.

http://www.interviewmagazine.com/film/tom-hardy-bronson#page2

I'll be updating the trivia section with this information. I've already updated the Wikipedia page for this film with this information.