The actress explained that it was important for her to show that Snow White could be just as heroic as her male counterpart the Huntsman (Chris Hemsworth).
"As soon as the armour goes on, you feel untouchable - but it's a different thing for a 5'5", 110 lbs girl to go into battle," Stewart said, reports Parade.
"When we first meet Snow White, she's been in prison for over ten years, and the land she knew has been destroyed. She has to find a way to survive, so she becomes an action hero out of instinct. I did fight training with a cardboard sword and foam shield, and I definitely gave the guys a good whacking occasionally."
The actress continued: "When I got to the set, it was like, 'No, you look like a ninja. Forget the choreography and try not to die'. The real sword was heavy - my arms got so ripped, I would look down and not recognise myself.
"Snow White is such a cool character. I respect her compassion; she struggles with the idea of taking up arms. But I am slightly more aggressive. That's not a struggle in real life for me."
Stewart recently revealed that she would love to star in a Snow White and the Huntsman sequel in the future.
Snow White and the Huntsman is now playing in the UK and the US.
Photo gallery: Snow White and the Huntsman premiere:
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