Sydney Sweeney underwent a remarkable transformation to portray professional boxer Christy Martin in a biopic portraying the athlete’s life. The actress gained 30 pounds of muscle and embarked on intensive training to capture both the physical and mental essence of Martin’s journey. This preparation took place primarily in 2024, leading up to the film’s world premiere at the 2025 Toronto International Film Festival.
The process was both challenging and exhilarating, with Sweeney describing it as an uplifting experience that empowered her. The Sydney Sweeney Christy Martin transformation involved rigorous workouts and a substantial increase in food intake to achieve a boxer’s physique.
Intense Training Regimen and Emotional Preparation
Sweeney dedicated about three and a half months to intense training that included morning weight training sessions, midday kickboxing workouts lasting around two hours, and additional weight training in the evening. According to her interviews, the regimen was demanding but enjoyable, allowing her to feel a close connection to Christy Martin’s physical strength and spirit.
She also faced the emotional weight of portraying Martin’s difficult story, which involved overcoming abuse and shattering gender stereotypes within professional boxing. Sydney viewed this challenge as a welcome opportunity to push herself beyond physical transformation into embodying the resilience needed for the role.
“It was probably one of the most amazing, fun experiences,”
Sydney told E! News’ Francesca Amiker before the 2025 Toronto film premiere.
“I was a very happy person, and I became so strong. I felt so good. I mean, I just felt Christy’s power.”
“Christy’s story isn’t a light one, it’s physically and emotionally demanding, there’s a lot of weight to carry,”
she said in an interview with Deadline.
“But I love challenging myself. Christy Martin not only legitimized female boxing, she overcame gender stereotypes and fought through emotional, physical and financial abuse.”
Visual Transformation on Set in North Carolina
Filming took place in North Carolina, where Sydney Sweeney’s appearance significantly changed to match Christy Martin’s. She switched from her signature blonde look to a shorter brunette hairstyle, typically held back with a navy bandana during shoots. Her wardrobe consisted of athletic and casual pieces that reflected a professional boxer’s practicality, including oversized sweatshirts, baggy sweatpants, and loose-fitting shorts.
Her costar Ben Foster, who portrays James Martin—the former boxing coach and Christy’s husband—also modified his appearance for the film. Foster, known for his usual beard, appeared clean-shaven with a blonde wig and various athletic outfits to embody his role.
Commitment to Collaboration and Craft
Sydney embraced a proactive approach to the filmmaking process, emphasizing collaboration on set to deepen her investment in the role. Her hands-on attitude allowed her to contribute ideas and engage fully with the production, a dynamic she finds essential in her growth as an actress.
“I am a very hands-on collaborator,”
Sydney shared with The Los Angeles Times in March 2024.
“I like being able to give ideas, be a part of it, help come up with solutions. It just changes the whole process. It’s so hard for me now to be on a set and not be able to help in any type of way and be able to take action. And being able to actually have a voice and have a valued opinion—it means so much.”
Inspiration and Future Ambitions
Beyond this transformation, Sydney Sweeney remains driven by a strong sense of personal growth and ambition. Reflecting on her career and aspirations, she sees her future self as a source of motivation and strives to make choices that her older self would respect.
“I look up to the older version of myself,”
she told Women’s Health in 2023.
“When I was 10, I looked up to the 25-year-old version of myself, and now I look up to my 50-year-old version. I hope I make the decisions she would be proud of.”
The Impact of the Christy Martin Portrayal
Sydney Sweeney’s transformation to portray Christy Martin represents more than just a physical change; it highlights the powerful narrative of a woman who fought arduous battles both inside and outside the ring. By embodying Martin’s strength and resilience, Sweeney shines a light on the challenges female athletes face, particularly in male-dominated sports like boxing.
The film’s debut at the Toronto International Film Festival is anticipated to draw attention to Martin’s legacy and Sweeney’s dedication, potentially inspiring audiences and elevating the conversation around female empowerment in sports and entertainment.
