Ashlee Simpson seems to have two sources of inspiration for her "Invisible" video — "Million Dollar Baby" and Chumbawamba's "Tubthumping" — because when she gets knocked down, she gets up again.

It's something Simpson can relate to, given all the punches she's taken thanks to a couple of nationally televised embarrassments (see "Ashlee Blames Gastric Distress For 'SNL' Lip-Synch Snafu" and "Ashlee Simpson Shrugs Off Orange Bowl Booing").

"It's a really cool concept," Simpson said. "It's basically about life, about finding the courage to get back up and keep fighting, which I think everybody deals with every day."

(Check out photos of Ashlee on the set of her video.)

Taking her punches this time in a boxing ring, Simpson plays a pugilist à la Hilary Swank's "Million Dollar" character, and to help channel a bit of Maggie Fitzgerald's fighting spirit, the singer shot the clip at the same facility used in the movie. She also took a few crash-course boxing lessons, where she found her previous experience as a dancer came in handy.

"I had one day of training, and right now," on the second day of shooting, "I'm one sore beyotch," she joked.

Because the emphasis of the video, directed by Marc Webb (Simpson's "Boyfriend," Hilary Duff's "Wake Up"), is how she takes it on the chin, Simpson couldn't use a stunt double and had to take more than a dozen falls on her face. That was intense, she said, but what was harder was repressing her sense of humor. "I giggle all the time, and I laugh at everything," Simpson said, "and Marc told me to be tough and not laugh in the ring. That was difficult."

What made things a bit easier, she said, was thinking about how her fans stuck by her when she was down in the dumps, and as a tribute to them, her character is fueled by one fan's devotion.

"There's a girl that when I get knocked out, I look at her," Simpson said of the video. "She's my fan and she stands by me, and that really helps me get up and keep going."

Simpson's new song, however, isn't a tribute to fans but instead seems to address detractors who think they have her all figured out. The "Invisible" chorus taunts, "You're the one who looked right through me/ Now you're saying that you knew me/ When I was invisible."

The song, which Simpson recorded with label executive Ron Fair in the producer's chair, should be available by late June/ early July, according to a label representative; a snippet is currently streaming on the singer's Web site. Simpson kicks off her summer tour Monday in Santa Barbara, California (see "Ashlee Simpson Ready To Hit Road For U.S. Summer Tour").