Sydney Sweeney Brain Damage Fears After A-Lister Admits She Went Full 'Raging Bull' for New Boxing Movie 'Christy'

Sydney Sweeney has sparked concern among fans after revealing she suffered a concussion – with insiders fearing she could have inflicted lasting brain damage on herself while filming brutal fight scenes for her new boxing biopic, Christy.

The 28-year-old Euphoria star, who plays U.S. boxing legend Christy Martin in the film, insisted on "real punches" during filming – telling costars to "hit me hard" despite warnings from producers about safety.

The shoot, insiders say, was so intense Sweeney ended up with a bloodied nose and suspected mild brain trauma after several takes went too far.

According to sources, Sweeney's determination to make the film as authentic as possible pushed her body to the limit. "Sydney wanted it to look real, no faking, no pulled punches," said one insider. "But when you're taking hit after hit for hours, it's dangerous – she was dizzy and disoriented more than once. People were genuinely worried she'd done herself serious harm."

Sweeney herself admitted the fights in Christy were far from staged.

She said: "The girls and all the fights you see are real. When I walked in and I met with everyone, I said, 'I want you to hit me. And I want you to hit me hard. And can I hit you?' So when you watch all those fights, we're actually hitting each other. We were knocking each other out, we were getting bloody noses. I got a concussion. We were actually fighting."

Her costar Katy O'Brian, who plays Martin's rival Lisa Holewyne, is said to have shared similar concerns as Sweeney's inner circle over her "method" approach to boxing – similar to that taken up by Robert De Niro for Raging Bull and Daniel Day-Lewis when he starred in The Fighter.

A source said: "It was as if Syd wanted to prove she could go as hard as the likes of De Niro. There were fears someone was going to get seriously hurt during this shoot."

To prepare for the role, Sweeney underwent an extraordinary physical transformation, gaining more than 35 pounds of muscle over three months through a punishing training schedule. She said: "I built my own 'Rocky' gym in my grandma's shed, and I trained back home in Idaho. I worked with my weight trainer in the morning and night, and then I had a boxing coach I worked with every day for two to three hours."

Sweeney's new film chronicles Martin's rise to fame as the WBC female super welterweight champion – and her harrowing escape from an abusive marriage to her former trainer and husband Jim Martin, who was convicted of attempted murder in 2010.

Sydney said portraying Christy's personal trauma was also emotionally draining.

"Everything that happens within the house towards the end of the story of her life in the film weighed on me emotionally," she said. "But the one I had the hardest time doing and just processing was when she asked for her mom's help. I have such amazing parents and I can go to them for anything. And I couldn't imagine how hard it was for Christy and for others that deal with that as well. And it broke my heart while I was making that scene."

Christy was a frequent visitor to the set – accompanied by her Pomeranian, Champ – and has praised Sydney's dedication to capturing her spirit. But according to one insider, the actress' commitment may have gone "way too far."

"Sydney wanted to honor Christy's toughness," said the source. "But there's a fine line between realism and risk. At one point, the medic on set warned that another concussion could mean long-term damage. And there are now fears she could end up 'punch-drunk in the future."

Despite those fears, Sweeney remains proud of her work. "I think Christy has changed me," she said. "I felt like I became the most free and powerful version of myself afterwards."