Hollywood star Sydney Sweeney has revealed the astonishing physical changes she underwent to portray legendary boxer Christy Martin in an upcoming biographical film, describing how months of grueling workouts completely reshaped her body.

The Emmy-nominated actress, best known for her breakout performance in HBO's hit series Euphoria, is set to bring to life the inspiring yet turbulent story of one of boxing's most iconic female athletes.

Sweeney recently shared jaw-dropping photos showcasing her dramatically muscular physique after undergoing an intensive training regimen. The transformation pictures quickly went viral, leaving fans stunned by her athletic makeover.

In an exclusive interview featured in the latest issue of W Magazine, Sweeney detailed the extreme measures she took to authentically embody Martin's powerful frame, including packing on more than 30 pounds (14 kg) of muscle through a punishing daily routine.

"I committed fully to becoming Christy," Sweeney explained. "For three and a half months straight, my days consisted of weight training first thing in the morning, two-hour kickboxing sessions at midday, and another round of strength conditioning at night - all while following a carefully designed nutrition plan."

The physical changes were so dramatic that none of Sweeney's regular clothes fit anymore. "Normally I wear size 23 jeans," she revealed with amazement. "By the end I was wearing size 27! My body felt completely transformed - I'd never been so strong in my life."

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