Natalie Portman drew on her ballet training from ages 4-13 for the role. She resumed ballet training a year before principal filming began. She trained with Mary Helen Bowers (formerly of the New York City Ballet) and the regimen included fifteen minutes of toe exercises (for her to be on point for dance scenes), substantial muscle toning, and swimming a mile a day. However, Portman has acknowledged having dance doubles (unnamed) in some interviews. Professional ballerinas Sarah Lane and Kimberly Prosa were the dance doubles for Natalie Portman. The special effects team also digitally placed Natalie Portman’s head on Sarah Lane’s body in several dance scenes. Lane did most of the heavy tricks, while Kimberly Prosa did the rest of the dance shots that were needed. According to both Prosa and Lane in separate interviews, Portman’s dance scenes in full body shots were actually the dance doubles. Prosa and Lane also said Portman was filmed dancing from the waist up, showing only face and arms, while the rest of her body dancing were that of the dance doubles.