Emma Stone "loved" gaining 15 pounds of muscle for her role in 'Battle of the Sexes'

Asked how she went about bulking up for the role, she said: "A lot of weightlifting, a lot of protein shakes. I never did it before and I loved it."

Emma, 28, admitted she initially struggled to cope with the physical demands of adding the extra muscle.

But, over time, the actress got used to her workout regime and she eventually started to enjoy the challenge.

She told 'Entertainment Tonight': "For the first three weeks, you hate your life, and I know a lot of people hate exercising. I did. And then after three weeks when you're, 'I can lift this? I can do this?' It just becomes addictive.

"It's just really incredible to feel strong. It feels so good."

Steve Carell plays the role of Riggs in the new movie, which marks the first time he's worked with Emma since he starred as her father in 2011's 'Crazy Stupid Love'.

And Steve admitted he relished being reunited with the talented actress.

He shared: "She's played my daughter and now she's playing my adversary in this. In this next one, I want her to play my mother. She could do it. She's that good."

As well as being a fan of Emma's skills in front of the camera, Steve reassured fans she's similarly likeable off screen, too.

Of his co-star, the American comedian added: "She's, like, the most delightful person in the world."