Sydney Sweeney gained 35 pounds, suffered concussion filming new movie

Sydney Sweeney stars as boxer Christy Martin in a new biopic, telling the story of a trailblazer who faced domestic violence and fought for women in boxing.

Stephanie Giang-Paunon is an entertainment writer for Fox News Digital. Story tips can be sent to stephanie.giang@fox.com and on Twitter: @SGiangPaunon.

Sweeney portrays boxing trailblazer Christy Martin in the upcoming biopic, and said she gained 35 pounds to play the role, training like a professional fighter in her home state of Idaho.

"It was so much fun though, because I grew up in Idaho with my family, and my grandma’s my neighbor, and I turned her shed into my ‘Rocky’ gym," Sweeney told "Good Morning America." "I put flooring in and boxing bags, and I brought my trainers up there, and I had a boxing coach and a weight trainer. And every single day I would weight train in the morning and night, then I'd box for like two or three hours a day."