Fight choreography videos are always cool to watch because you never truly appreciate the amount of work that goes into the final sequence you see on screen. Boxing movies are almost equally as captivating because you can't improvise the outcome. Every move has to have meaning and a result or the fight will look fake. So actors have to memorize round by round what they're going to do. It can really grill an actor both mentally and physically, especially when you're simultaneously directing the film. Watch this clip of Sylvester Stallone and Carl Weathers walking through a fight for Rocky!