Credit: Andrew H. Walker/FilmMagic

Embodying the role of a ballerina in the new psychological thriller Black Swan wasn't easy for Natalie Portman.

A year before shooting, she had to undergo extreme ballet, cross-training, and swimming. In the end, the petite, 5'3" actress, 29, shed 20 lbs.

"I think it was just the physicality of it all that was the most extreme," she told Monday at IFP's 20th Annual Gotham Independent Film Awards in NYC. "I mean, I had never gotten that much training - to be doing five-to-eight hours a day of [it] was really a challenge."

How did she do it? "With discipline!" she told Us.

Despite the physical demands of the role, Portman, a vegan, said she was happy to throw herself into the part, for which she is already generating Oscar buzz.

"I think the most important thing is coming to work as prepared as you can be every day and working as hard as you can every day," she told Us. "If you do that, you can always ensure that you have an amazing experience."

Would she ever undergo similar training for a film role again?  

"I think I would do this kind of training again because it's just so rewarding," she told Us. "It's always one of those things where, when you put in a lot, you get out a lot."

She said she'll even incorporate some of the skills she learned into her day-to-day life.  

"Not ballet," she told Us, "but I'll always dance!"