The Snow White and the Huntsman actress said that her role entailed raising her voice so much that it led to her injury.
Theron told MTV News: "I did enjoy just screaming at people. I screamed so much at people, I tore a stomach muscle, which I had never heard of before."
The actress, who announced in March that she had adopted a son named Jackson, added that the personality of her demanding character Queen Ravenna stuck with her even when she wasn't filming.
Theron joked: "Off set, you can joke about it, because you're in these costumes. I felt like I was being so high-maintenance: 'It hurts, oh gosh, I can't walk to craft service.'
"You become a big pain in the ass. I mean, I'm saying it was the costume. But it really wasn't. That's how I behaved."
Snow White and the Huntsman, which stars Kristen Stewart and Chris Hemsworth in the title roles, opens on May 30 in the UK and on June 1 in the US.
Watch a trailer for Snow White and the Huntsman below: