For me, the true test of a documentary is how much it makes me care about a subject I previously cared nothing about. Recent films that have passed the test: “Blackfish” (orcas in captivity), “Bending Steel” (self-made strongman), “Drew: The Man Behind the Posters” (guy who created cool hand-drawn movie posters). And now the new documentary “The Crash Reel” (snowboarders).

Playing at Space Gallery on Saturday, “The Crash Reel” focuses on Kevin Pearce, a snowboarding prodigy who rose to the heights of the sport, vying for a 2010 Olympic berth while dueling with, and actually surpassing eventual gold medalist Shaun White. While still a teenager, Pearce went pro, scored countless endorsements, and started besting White in competitions around the world.

And then he fell.

In footage, the fall, after missing a training move on a 22-foot half pipe, doesn’t look especially dramatic. We’ve all certainly seen worse, thanks to Youtube and the ubiquitous “crash reels” that come out of extreme sports competitions like the X Games. But Pearce landed squarely on his face, was choppered to a hospital and diagnosed with a traumatic brain injury that left him comatose, then facing months of intensive rehabilitation.

The film, from Oscar-nominated filmmaker Lucy Walker (“Devil’s Playground,” “Blindsight”) follows Pearce and his close-knit family as he slowly recovers and contemplates a comeback.

By the numbers, so far, for a sports documentary, except that “The Crash Reel” turns into less the expected “athlete overcomes obstacles” tale and more about the way “extreme sports” are a poorly regulated tragedy waiting to happen, and how Pearce learns, with his family’s help, that all those macho jock platitudes serve to distract young, invincible-feeling athletes from the fact that youth, and health, are fragile commodities indeed.

As an avid non-skier/snowboarder/risker of well being by showing off, I admit to feeling a little worn out by the beginning of the film, a typical montage of best buds bro-ing out on the slopes and saying “dude” a lot. But Walker’s approach serves a purpose, showing the beginning of a breezy, feel-good ski film before yanking the board out from under the viewer once the lively, graceful Pearce goes down and his toothy, cocky grin becomes the glassy, terrified stare of a young man suddenly unable to think clearly or move his limbs.

As Pearce’s rehab progresses, we see him try to reassert his formerly world-class physicality with heartbreaking results, and witness how his dogged determination to return to pro snowboarding (and the physical and mental limitations from his injury) try the understanding of his warm, supportive family (including his Down syndrome-afflicted little brother David, a Special Olympian who should probably get his own movie next).

So is “The Crash Reel” saying you snow-fiends should hang up your boards? Not really. If there’s a target here, it’s more the proponents of extreme sports, who, promoters and fans alike, insist on more and more dangerous stunts to whet the public’s appetite for spectacle.

Apart from pointing out the lack of insurance and safeguards for athletes, the film makes the point that other dangerous sports such as car racing eventually put limits on how fast and how perilous their sports should be. Not so for the X Games, where the ethos of “higher, faster, more dangerous” rules.

Of course, pushing the physical limits of what humans can achieve is the essence of athletic competition, and I love the Olympics as much as anyone.

But after we see the montage of crippled and dead extreme athletes (in harrowing footage), and Pearce’s effort to impart what he’s learned to a twice-brain-injured snowboarder who has chillingly lost the ability to control his impulses, the X Games announcer who pays tribute to deceased freestyle skier Sarah Burke with the pronouncement, “It’s said that the brave do not live forever but the cautious do not live at all” seems like just the sort of person who should see “The Crash Reel” before he goes on TV again.

Dennis Perkins is a Portland freelance writer.