The 24-year-old actress feared that her tiny stature might make her less influential as the deadly Black Widow, and took up the challenge to look convincing.
"I did a lot of stunt training, weight training and all that stuff for Iron Man. It took strength training to try to fit that mould," the Sun quoted her as saying
"I wanted to be able to look at something and go, ''Okay, I'm going to knock the s**t out of that person. To believe that is a challenge in itself, especially when you're 5''3" and fighting someone who's seemingly a giant.
"You have to be able to have conviction in that. That was just as much of a challenge as the actual physical part of it," she added.