Here's a piece on the workout that the actors in 300 were put through to get in shape. As the article describes, basically the costume was "a pair of leather underpants and a red cape." (I foresee an Oscar for Best Costume Design!)
Did I mention that I loved this movie?
Hmmm... Three months, two hours a day, six days a week... If someone were to come out with the "300 Twelve Week Workout," I'd buy that book!