Natalie Portman wowed at IFP's 20th Annual Gotham Independent Film Awards at Cipriani in NYC, but the actress reveals that dropping a whopping 20 pounds for her starring role in Black Swan was quite the challenge."I think it was just the physicality of it all that was the most extreme," she told Us Weekly last night. "I mean, I had never gotten that much training - to be doing five-to-eight hours a day of [it] was really a challenge." A year before shooting began, the 5'3" actress got in shape by doing a combination of extreme ballet, cross-training, and swimming, and when asked if she'd do it all over again, she replied, "I think I would do this kind of training again because it's just so rewarding. It's always one of those things where, when you put in a lot, you get out a lot."