According to David Michôd, the director and co-writer of the film, "Christy Martin put women's boxing firmly on the map in the mid-'90s. She was the first female fighter to appear on the cover of Sports Illustrated and fought on the Mike Tyson undercard. Her husband, who was also her trainer, later attempted to murder her after her success. Our film is a heady blend of an inspiring underdog sports story and an intimate personal saga."
Sydney Sweeney gained 30 pounds to portray boxer Christy Martin. She also undertook roughly three and a half months of training, which involved an hour of weight training in the mornings, about two hours of kickboxing at lunchtime and another hour of weight training in the evenings. She said in an interview with W magazine, "My body was completely different. I didn't fit into any of my clothes. I'm usually a size 23 in jeans, and I was wearing a size 27. My breasts got bigger. And my bottom got huge. It was crazy! I was like, Oh my God. But it was incredible. I was so strong, ridiculously strong."
