In Million Dollar Baby, Swank is Maggie Fitzgerald, product of a poor, trailer-trash family, who at 31 works long hours as a waitress but dreams of becoming a champion. To that end, she persuades Clint Eastwood to become her trainer and guide her through the world of championship boxing.
To play the female pugilist, Hilary put on 20 pounds of muscle, working out fiercely for over three months, pounding the punching bag so she could climb into the ring and look like a credible, two-fisted destroyer.
Today, those muscles have softened and she looks more, um, rounded in a cream silk blouse with a large black butterfly bow, blue jeans and high heel shoes as she sits in a Beverly Hills Hotel sipping bottled water.
Glamour in front of the camera is a quality that has so far eluded her, Swank admits. "It's something that I've probably made a conscious effort about because I was so intent on being taken seriously and doing good roles and not being the arm candy or playing the girlfriend who has nothing to do."
Hilary says when she read the script, she knew she wanted to step into the ring.
"I was able to push myself to the limit again and break through mental, physical and emotional barriers all of the time. That's my passion. I really like a challenge and I like to see how far I can go. I don't know if I'll do that for the rest of my life or if I'll have that energy. But this movie was great."
In the film, trainer Eastwood is at first reluctant to work with her. Women who become fighters, he snaps, "are freak shows."
But Hilary says she has great respect for the real women boxers she met who helped her hone her skills as a boxer.
"Many were trying to climb out of poverty. And boxing can do it for them. So I identified strongly with those ladies because I too grew up in a trailer park surrounded by poor people. To me, every woman has a princess inside of them no matter where they're from and no matter how much money they have. They all have their own stories to tell and each one is fascinating. That's why I became an actor, because I really love people. Everyone has a unique story."
The slender star said she knew she had to look the part of a hungry fighter out to win the world championship to make the role convincing for audiences. She didn't do the Renee Zellweger thing in Bridget Jones's Diary and eat herself silly.
"I knew I had to look like a boxer, and my job was to step into a fighter's shoes and experience that way of life because I didn't have a clue about boxing. I mean, who would want a job where you get hit — and you hit other people?"
She trained for almost five hours a day, six days a week for three months until she had built up the requisite muscles. And she lifted weights for two hours a day.
"I also ate about 210 grams of protein a day. Your body can only assimilate so much protein at a time. So I had to eat every hour and a half. I was drinking egg whites. I drank flax seed oil. I needed to rest and to sleep nine hours a day because if your muscles don't really rest, they don't recover and can't grow."
That meant waking up in the middle of the night, drinking a protein shake and then going back to sleep. "I couldn't go nine hours without eating," she explains.
Every week, she broke through new fitness barriers.
"The analogy I use is about runners. They never thought they could run a mile in four minutes, and so when it happened, other athletes realized they too could break the barrier. And dozens did. I felt it was all about the power of the mind."
However, she's the first to admit there were days when she wanted to quit: "I'd wake up and say, 'Oh, I can't do it today. I'm really tired and I'm really sore. My shoulder hurts, my lips are bloody and swollen and my head aches.'"
But she stuck it out, with encouragement from her co-star and director Eastwood and her husband, actor Chad Lowe (brother of Rob).
So how did Chad feel waking up every morning in bed with a muscle bound Wonder Woman?
"Oh, he loved it," Hilary laughs. "He was inspired by how good a shape I was in. He even sparred with me a couple of times, but I couldn't get him to stay the whole four and a half hours every day."
But her husband's chief role, she says, was to give her mental support. "He's my best friend. He's a mentor and teacher at times and my closest confidant. That's the great thing about our relationship. It's really beautiful."
Hilary says the role of Maggie was not as big a stretch for her as one might imagine.
"There are a lot of parallels, I think, with Maggie's life and mine. Maggie was living her dream and there was a line that went, 'I've never felt good doing anything else. If I don't do this, I've got nothing.' I've often felt that way about acting. There's nothing else that I feel like doing. If I don't have it, what am I going to do? And in this case especially, it was a dream come true for me to work with Clint Eastwood."