Jeff Imada, BD2 Stunt Coordinator, Mentions Kristen

To prep for the final film, in which Kristen Stewart's character, Bella, transforms into a vampire, stunt coordinator Jeff Imada tells Us the actress "did drills, like martial-arts stick training. We'd do three hours of choreography on Saturdays, Kristen's day off. She's a pretty physical girl!" Even when Stewart broke her thumb, "she toughed it out," adds Imada. "She said, 'Keep going!'" 

Source | Via