Scarlett Johansson had to "mentally challenge" herself to get beaten up every day on the set of The Avengers.

The 27-year-old actress plays the role of Black Widow in the forthcoming Joss Whedon-directed action adventure film, and she admits it was tough to get used to the fighting scenes but she realized she had to get them done in early takes so it would hurt less.

"I think just kind of going back day after day, knowing that you're going to get the crap kicked out of you and do it willingly is sort of a challenge in itself, a mental challenge. But also I have to say that every time you fail at a stunt, it hurts until you get it right," she said, speaking at the world premiere at the El Capitan Theatre in Los Angeles.

Black Widow is one of the only characters in the film to have not had her own movie - with Chris Evans appearing in Captain America and Chris Hemsworth in Thor - but Scarlett believes it made no difference when they shot the ensemble piece: "She's really the first female superhero. There's a huge rich background for me to kind of pick from and play with and layer."