Watch Sydney Sweeney's transformation into boxer Christy Martin

Sydney Sweeney is ready to step into the ring.

The actress shared a few behind-the-scenes pictures (below) from her time on the set of the Christy Martin biopic in which she stars.

“Well the cats are out of the bag thanks to some stripes in the bushes so here are some BTS from my movie I'm working on,” she wrote in an Instagram caption to two photos of her in sweatpants with a brown one , curly hairstyle. “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.”

She concluded: “Their journey is a testament to resilience, strength and hope, and it is an honor to follow in their footsteps and share their powerful story with all of you.” More to come soon.”

David Michôd will direct the film, which is currently untitled and tells the true story of Martin's rise to become one of the most recognizable female boxers in 1990s America. Ben Foster, Merritt Wever, Ethan Embry and Katy O'Brian also star in the biopic.

Martin began her career in 1989 after meeting manager and future husband Jim Martin. She competed until 2012 and is currently the only female boxer to appear on the cover of Sports Illustrated.

But the athlete's life was not without many struggles. In 2010, her husband stabbed her repeatedly and shot her in the chest, leaving her presumed dead. She managed to muster the strength to run out of the house and flag down a passerby who took her to the hospital. Two years later, Jim Martin was sentenced to 25 years in prison for attempted second-degree murder with a firearm.

The boxer told CBS News that his abuse of her took many forms, including sexual and emotional. She explained that he got her addicted to cocaine and constantly supplied her with cocaine. He also blackmailed her and threatened to reveal her sexual orientation.

“The whole sexuality part is really difficult because I was so close,” she told the station. “First of all, I trusted Jim Martin, and he was 25 years older than me. He was my coach. I felt like this was someone that I could open up to and open my heart to and tell him all about my issues with sexuality, my issues with my family, just the issues in life, and all of that was countered used me.”