From its opening shots, Murderball gleefully smashes preconceptions about quadriplegics. This valuable documentary approaches its subject-athletes vying for the wheelchair rugby world championship-head-on, with no apologies to the squeamish. Filled with compelling characters and unexpected twists, Murderball turns a potentially grim subject into an affirmation of human spirit.

Quad rugby is played on basketball courts. Teams are made up of quadriplegics who sit in wheelchairs modified with armor to withstand ramming. It is a full-contact sport in which players can be spilled out of their chairs. "It's basically kill the man with the ball," says team member Bob Lujano.

Directors Henry Alex Rubin and Dana Adam Shapiro (whose Maxim magazine article inspired the film) first catch up with the United States Paralympics team in Sweden, where they are defending their world title for the 11th consecutive year. But coach Joe Soares, a former star player who defected to the Canadian team, stages an upset, taking the championship away from the U.S. for the first time. "How's it feel to betray your country?" one of the U.S. players asks Soares.

The teams then prepare for the next championships in Athens. Through tryouts and practices, viewers not only learn more about the players, but get a chance to see how quadriplegics cope with daily life. Mark Zupan, the star of the team, is an intimidating presence at first, but as the filmmakers delve into his past, he becomes admirably forthright and forgiving. An underlying question in the film is whether Zupan will reconcile with Christopher Igoe, the friend who broke his neck in a truck accident.

Intriguingly, the film also follows Soares, a complex character whose outsized ego is matched by his impressive accomplishments. Unlike most quad rugby players, who come to the sport after accidents, Soares is a victim of polio. His maniacal drive is both appealing and frightening, especially when he is dealing with his young son Robert, who is more interested in classical music than in athletics.

Another branch of Murderball focuses on a rehabilitation center for patients recovering from spinal cord injuries. Keith Cavill, who broke his neck in a motocross accident, struggles to adjust to his physical limitations. When he sees a quad rugby chair, he instantly recognizes a way to channel his competitive drive. Alarmed nurses have to restrain him from ramming into an instructor's chair.

Rubin and Shapiro had the luck to stumble across fascinating stories that complement the intense sports rivalry between the U.S. and Canada, but also the insight and patience to capture the human side of their characters. Murderball has its share of ribald hijinks and practical jokes, as well as poignant encounters and some stinging confrontations. The film operates on so many levels that it doesn't have time to preach. And with characters as spirited as these, it doesn't need to.
-Daniel Eagan