Documentaries about physically or mentally challenged people who overcome the odds to realize their dreams are usually pretty sappy affairs, but as the title suggests, this one is made of rather sterner stuff. In fact, from a marquee you might expect “Murderball” to be some high-tech action flick starring the likes of Sylvester Stallone or Arnold Schwarzenegger in their heyday. But no: it’s the story of the U.S. quadriplegic rugby team and their rivalry with a Canadian squad coached by a former U.S. player most of the current ones consider a turncoat.

At first, it must be said, you might think that spending nearly ninety minutes with these guys will be a chore not worth undertaking. As we’re introduced to the players, and to that turncoat coach as well, they seem like basically crude, rather brutal guys. And the game they play is hardly one for wusses. Using specially plated chairs that allow for quick motion and hard contact, it’s not just fast-moving but no-holds-barred stuff.

If “Murderball” remained on a general level throughout, it might have been very heavy going. But while it doesn’t stint on its coverage of the games, particularly the make-or-break (sometimes make-and-break) contests between the U.S. and Canada, it personalizes the subject in any effective way by focusing on two individuals. One is Coach Joe Soares, who took over leadership of the Canadian squad after he’d been cut (unfairly, he believed) from the American squad after years of stardom. At first he’s portrayed as a rough, hard-noised guy whose relationship with his son Robert, a kid whose interests incline more to making music than mayhem on the field or court, is tense; but his character mellows after he suffers a heart attack, and his reconciliation with the boy afterward is actually heartwarming. (In a fiction film his rush to make the kid’s recital might seem manipulative and cloying; here it’s still manipulative, but it doesn’t cloy.) On the other hand, there’s Mark Zupan, a hyper-aggressive U.S. player who seems at first a manic ruffian you wouldn’t like to meet in a late-night bar. Over the course of the picture, though, he emerges as a more rounded, even admirable fellow. The picture touches on his relationship with his girlfriend Jess (digressing to offer observations on how some women are attracted to quadriplegics, and how the disabled men can be instructed in the techniques of post-recovery sex). But more importantly, it sets up a test of friendship saga by introducing Chris Igoe, the buddy who was driving when the accident that cost Zupan so much of his mobility occurred. The two haven’t seen one another or spoken for years, but reunite when Igoe comes to see the U.S. team in the 2004 paralympics. Once again, the incident is touching despite the obvious calculation, yet–like the film as a whole–it doesn’t descend into bathos. And though Soares and Zupan are the figures around whom most of “Murderball” revolves, other players make strong impressions, too (mellowing from their severity over the course of the film as well), while subsidiary figures also make their mark–like Zupan’s father and a recently-injured young man, an athletic type whom we watch undergoing therapy, who’s fascinated and excited by the concept of quadrplegic rugby when Zupan visits the ward and introduces the patients to the game.

In fact, though the picture–necessarily for any sports flicks–naturally spotlights the competitions at which Soares’ Canadians and Zupan’s Americans clash (and Henry Alex Rubin’s spot-on camerawork and Geoffrey Richman’s expert editing bring the action home strongly), ultimately what you’re more likely to take away with you from “Murderball” are its characters. It’s the humanity on display, and the complexity and resilience it exemplifies, that’s memorable here–which, of course, is exactly as it should be in a good film, fiction or not.