The Oscar nominee admits she was self-conscious about how she would look on camera in sexy underwear and wanted to tone up before she had to shed her clothes.
But filmmaker Russell stopped her from doing so - because he wanted to ensure her portrayal of Charlene, a working-class barmaid, was as realistic as possible.
Adams tells Parade magazine, "David said, 'This is kind of how we see her dressing (in lingerie).' And I said, 'I'm getting in a gym, 'cause there's no way I'm going to end up not looking my best.' (But) he said, 'I want you to look like a girl who drinks beer!'"