Sydney Sweeney has shared new photos of herself playing boxer Christy Martin in an upcoming biopic, in which she sports a '90s-style mullet and adds some extra muscle for the former athlete's role.

“Well thanks to some treats in the bushes the cat is out of the bag so here's a little BTS from my movie I'm working on,” Sweeney wrote on Instagram.

She stars as Martin in an untitled sports biopic directed by David Michod, which recently began production. Martin is a former professional boxer who competed from 1989 to 2012 and became super welterweight world champion in 2009. In 2010, she also survived an attempted murder by her husband James Martin. He stabbed Christy multiple times and shot her in her Florida home, but she survived. In 2012, James was convicted of attempted second-degree murder and sentenced to 25 years in prison.

“Over the past few months, I have been training intensively to bring to life the story of an incredible woman – a true champion who fought battles both in and out of the ring,” Sweeney wrote. “Her journey is a testament to resilience, strength and hope, and it is an honor to follow in her footsteps and share her powerful story with all of you. more coming soon 🙂 CHRISTY MARTIN.”

In 2020, Martin was elected to the International Boxing Hall of Fame on the organization's first ballot, which also included women.

The cast of the upcoming biopic includes Ben Foster as James Martin, Merritt Weaver, Katy O'Brien, Ethan Embry, Jess Gabor, Chad L. Coleman and Tony Cavalero. The film is produced by Anonymous Content, Black Bear Pictures, Fifty-Fifty Films, Votiv and Yoki Inc.