When Sydney Sweeney was first approached with the possibility of playing Christy Martin, she couldn’t believe that she hadn’t heard the story of "The Coalminer’s Daughter."

As boxing fans know, Martin’s story is so extraordinary, equal parts harrowing and inspirational, that viewers who hadn’t followed Martin’s life and career would think that "Christy", which hits theaters on Friday, was simply a Hollywood construction. But once the uninitiated were made aware that this is indeed a true story with very little embellishment in the film’s writing, they likely had the same response as its leading star when she read it for the first time.

How is it that the story of a woman who escaped abject poverty to become a paradigm-shifting boxing star before surviving drug addiction and an attempted murder by an abusive husband who suppressed her sexual identity in tandem with her own mother before finding love with a former in-ring opponent was not a motion picture already?

And how is Christy herself not an even bigger star outside of the boxing circles where she is heralded?

“I was inspired every single day. I was inspired the moment I read the script and I couldn't stop thinking about her,” Sweeney told The Ring. “I think that Christy's story is going to unlock so much for so many people. I mean, she touches on so many different challenges in life, and she's overcame so much, and she's an amazing role model and advocate. She's absolutely incredible, and knowing how special of a human being she is, every single day I felt that, and every single day I felt the importance of telling her story.”

The question of how everyone doesn’t know about Martin’s story is likely moot now, as Sweeney’s performance in becoming Martin, combined with her wattage as one of Hollywood’s brightest stars, is likely to further immortalize her in the way underappreciated fighters (see: Jim Braddock, Vinny Paz) have been in the past.

Martin is certainly no stranger to the spotlight, having fought on pay-per-view, and enjoyed the requisite publicity in magazines and on talk shows, but has settled into a role as regional promoter and commentator on Don King events. Now, she admits that the forthcoming, and maybe long-lasting attention after being immortalized on-screen, feels a little daunting.

“It’s just now starting to sink in for me,” said Martin. “I think that I have a weight on my shoulders to continue to change people's lives. I have to live up to it now. [Sweeney] did what she did, a tremendous job, and we're gonna bring the story to so many people. But now, the true me has to not backslide. I can't go backwards. I can't screw up and let someone down. A lot of people are sending me positive, 'you're inspiring me' messages."

Sweeney grew up grappling and kickboxing, training under “The Godfather of Grappling” Gene Labell, who helped pioneer mixed martial arts with his bout against middleweight boxing contender Milo Savage in the early 1960s, and worked as a boxing judge in California in the 2000s. That background, an understanding of what a true physical struggle feels like, of having to suppress or invoke emotions to push oneself in combat, shined through in Sweeney’s portrayal of Martin in the ring.

Boxing movies have often been maligned for their cartoonish portrayal of the sport for the purposes of dramatization, but Sweeney managed to portray a true-to-form Martin. Working in the film’s favor is that Martin’s fights did often devolve into reckless brawls, one of the reasons why she became as popular as she was. Go watch the final moments of Martin’s career, voluntarily eating punches from Mia St. John before their emotional embrace at the bell—it’s a movie scene already. That particular fight didn’t factor into the film, but many of Martin’s high and low in-ring points did, which Sweeney worked with co-writer/Director David Michôd, Director of Photography Germain McMicking, Stunt Coordinator and Fight Choreographer Walter Garcia to reenact in a frame-by-frame facsimile as much as possible.

In researching her role, Sweeney was blessed with dozens of hours of footage at her disposal just in terms of Martin’s fights alone. She was able to capture the idiosyncrasies of Martin as a fighter from a technical standpoint. Early in fights she would use the technically sound double jab, right hand, left-hook combination, one Sweeney breaks out shadowboxing consistently throughout the film, but once the fight broke out, it looked like a fight. Sweeney captured those moments, the physical and sometimes emotional dichotomy of technical adherence and a desire to both hurt and entertain.

But her source material wasn’t just on film. Sweeney also had Martin by her side often throughout filming, and was able to both get her feedback but also observe her mannerisms in real-life and in real time.

“I dive into my characters and having Christy as a real person who was with me by my side during all of it changes the entire process and helps immensely and was a gift. And so when I have that kind of access, but then also just a plethora of material to study as well, feel like when I go into it, I lose myself completely. And I don't even remember half the time what I'm doing. And that's the fun of all the art. I feel free and I become somebody else.”

Sweeney did effectively have to become somebody else in terms of a physical transformation for the film. In order to get up to speed skill-wise and be ready appearance-wise for filming, Sweeney built what she’s described as a Rocky-style gym in her grandmother’s garage, and endured a gruelling twelve-week training camp, as if she were preparing to move up in weight for a real fight. She had two separate weight-training sessions in the morning and at night, sandwiched between a three-hour boxing training session in the afternoon. In between those sessions, there were a lot of protein shakes, as she put on 35 pounds in total for the role.

"I worked the hardest on my left hook, because that was Christy's signature. And I've got a pretty good left hook. I think what would actually get me through a fight, though, is I can take a hit. I know that I've got to stay away from getting hit, but I have such determination that I'm not going to be taken down, that I feel like I wouldn't get knocked out, because I would just keep pushing through anything that was coming at me,” said Sweeney.

Sweeney was able to put that hypothesis to the test, and also get first-hand experience as to what it was like to be in the ring with Christy Martin by actually doing it. The two had a sparring session during production in which all of the other cast members and production team watched and cheered on. As the session went on, Martin couldn’t believe that she was “getting hit with (her) own combinations.”

"I actually got in and sparred with her, so we know she's for real. I was surprised, actually, at the perfect punches, the straight punches. It's not easy. She did boxing, she's done combat sports, but she only did boxing for, like she said, two and a half, three months. That's a short amount of time. I did it for my life and it took me that long to learn to throw those punches," joked Martin. "In two and a half months she was able to copy everything that I was doing."

The weight, both the iron she had to hoist and the muscle mass she had to add, were only part of the heft of the daunting role for Sweeney. The film grapples with incredibly heavy topics, from domestic abuse to sexuality, misogyny and homophobia. That weight was understandably most felt by Martin, who was essentially watching a real-time reenactment of her most painful and frightening moments. Michôd noted that Martin often steered clear of Ben Foster, who portrayed her ex-husband Jim Martin, on set, understandably finding being around him to be unsettling.

“Well, the fun days were the fun days. The boxing days. The boxing days were what we enjoyed. Yeah, we enjoyed those days. The other stuff, it was tough. And some of it, we really had to stay away because I couldn't let my heavy energy affect her work. So I kind of kept distance from [Sweeney] on the really heavy days. But then when we were having the good boxing days, we were having a blast.”

Thoughout the process, Sweeney and Martin seem to have developed a genuine bond, attending the International Boxing Hall of Fame weekend together in June, and taking in a World Series game at Dodger Stadium recently as well.

Sweeney has also seemingly caught the boxing bug permanently, suggesting that you might see her ringside at fights—or even in the ring itself.

“There was a moment in the middle of filming where I was like, should I give it all up and fight? Because I love this. And Christy said she'd sign me up, so this isn't as hypothetical as you actually think it is. I'd totally do charity boxing. That'd be so sick. I'd have to train again and take a little time off to be able to do so,” said Sweeney. “No one's offered to get me into the ring. I have gotten some interesting DMs from some boxers though,” said Sweeney, slyly, not revealing any names.

She’s done enough work making a boxer even more famous, for now.