(Cover) - EN Showbiz - Natalie Portman concentrated so hard on perfecting dance routines for Black Swan she was often reprimanded for shooting scenes with her mouth open.

The actress has received critical acclaim for the role of ballerina Nina Sayers, winning a Golden Globe Award last night and she is tipped to receive an Oscar nomination.

She trained hard for the role, restricting her diet to lose weight and learning intricate ballet moves so her character was believable.

Natalie admits shooting was tough, not least because it took a lot of concentration to get the choreography right.

Yeah, it was really tricky because... I think the trickiest part was balancing the physical with the emotional because sometimes just to do a certain move you need so much concentration, she told Cover Media. My mouth would be hanging open, or Id have my concentration face which is all furrowed, I mean half the time they were just trying to get me not to have my tongue sticking out and then to add onto that I had to be acting in a scene.

The 29-year-old added although her character is quite naive, she is also an accomplished dancer. Marrying those two sides to Ninas character was incredibly tough, as they often pulled against each other.

Oftentimes there was demands that were contrary to one another that you need to be really confident to do your turns, and you need to be insecure in the scene, she explained. Having to do those at the same time was probably the most challenging. It was just constant attention, there was no break in the day. As soon as you would finish a shot, Id be warming up physically and getting ready for the next thing. It was good to keep that level going throughout.

Black Swan is released in the UK on January 21. (C) Cover Media