The real star of the film, which opens on Oct. 2, may be the sport of roller derby. Based on Shauna Cross's novel "Derby Girl" and her personal experiences as a derby skater for the Los Angeles Derby Dolls, Ms. Cross's screenplay called for its protagonist -nicknamed "Babe Ruthless" -to scrimmage while skating around an angled track, among other physical challenges.

 

First popularized around the time of the Great Depression, female roller derby has evolved since its inception. Its most current version, which places an emphasis on genuine athleticism over fake stunts and hits, has roots in Austin, Tex. and migrated to big cities like Los Angeles, where Ms. Cross picked it up and skated under the name "Maggie Mayhem."

 

 

Ms. Page (the star of the quirky 2007 comedy "Juno") trained for three months prior to production, first on her own with Alex Cohen, a radio host who also skates with the L.A. Derby Dolls, under the moniker "Axles of Evil," and then as part of a cast-wide boot camp. As a Canadian, the actress grew up on ice skates, but still needed to learn how to maneuver on four-wheeled quad skates, master the art of falling, and, for a climactic moment, jump over a huddle of girls collapsed on the track. In line with Ms. Barrymore's insistence that no hidden wires or secret pulleys be used, she ended up doing about, in her estimation, 99 percent of her own skating and stunts.

 

Ms. Cohen, who also helped co-stars Kristen Wiig, Eve and Juliette Lewis find their footing for the movie's athletic sequences, says she began her skate training with the basics, such as the correct way to put on an elbow pad. "A lot of the preparation is not necessarily intuitive," she says.

 

Luckily, most of the cast survived accident-free, if not completely bruise-free. "A lot of skating is about confidence, and not getting freaked out," Ms. Cohen says. "Nobody wants permanent liver damage."