Keira Knightley says bodybuilding for a new film role left her insecure about her appearance.

Knightley, 18, underwent three months of intense physical training for her role as Guinevere in King Arthur.

"I've seen pictures of myself - I'm big," said Knightley, who trained under Ed Chow who got Angelina Jolie into shape for Tomb Raider. "You can see proper muscles.

"It freaked me out because it didn't feel like me anymore - the shape was completely different," she told Vanity Fair magazine.

Source: Press Release