It doesn't take long to understand the level of commitment Zac Efron brings to "The Iron Claw" as Texas wrestling brother Kevin Von Erich. Just one look at the taut mass of muscle and sinew he's become for the role will do the trick.

It's also clear from the get-go how invested writer-director Sean Durkin was in telling the true-life tale of the Von Erich family wrestling dynasty, which — shockingly, to those of us unfamiliar with the story — suffered a set of tragic losses almost too staggering to imagine. It's hardly a spoiler alert to say that Kevin, by 35, was the only surviving brother of an original six. (He is now 66). Indeed, so devastating is the story that Durkin felt the need to excise brother Chris, one of three lost to suicide, from this retelling entirely.

Durkin has said he was a committed wrestling fan from his childhood in England, where he scoured magazines to learn more about the exploits of the Von Erichs, who made their name in the colorful, high-flying, entertainment-heavy wrestling world of the '70s and early '80s. And from that affection stems perhaps both the strength and weakness of "The Iron Claw." It's a film that tells its stunning tale with heart and conviction, yet seems somehow reticent about pointing a truly critical finger at either the brutality of a sport that broke this family, or the man who seemed to give his sons no choice in the matter: family patriarch Fritz Von Erich.

It is with Fritz that we begin. In a 1950s-era prologue rendered in black-and-white, the eventual patriarch and promoter (an excellent Holt McCallany) is in the ring himself, displaying his famed "Iron Claw" maneuver: a punishing two-handed grip on a doomed opponent's skull, crushing it like a vice.

Waiting in the parking lot is Fritz's wife, Doris (Maura Tierney) and their young kids. Doris is shocked that Fritz has acquired a spiffy new car to attach to their trailer, something they can't afford, but he tells her it's all part of the persona he's building: You need to be the toughest and the strongest, and then nothing will be able to hurt you.

Flash forward to 1979, and Fritz has passed the dream of becoming heavyweight champion onto his remaining sons. (One of them has died at a young age in a terrible accident.) Kevin is doing his best to be the son who gets there first. Among his exploits in the ring, Kevin climbs up on top of the ropes to attack from the air, leaping onto an opponent. These fight scenes are vivid and exciting, although if you're like me, eventually you'll be shouting at the screen, begging for it all to stop, lest one more son get hurt.

But at the kitchen table, there's never talk of stopping. Fritz tells Kevin, David and Mike that they all need to work harder to win that coveted championship belt. Mike, the youngest, is interested in music, but Fritz doesn't care. Privately, Kevin seeks out his mother and asks her to intervene on Mike's behalf. But Doris relies only on her faith; this wrestling business is between the men, she says. (It is horrifying to watch her, powerless, as the sadness multiplies.)

Who will achieve Dad's dream first? Will it be David, who's a great talker and taunter in the ring? Or Kevin, who possesses great physical strength but is awkward and unable to master the art of self-promotion? Suddenly, brother Kerry, a discus thrower with Olympic hopes, enters the scene. When President Jimmy Carter declares the United States won't be sending a team to Moscow in 1980, Fritz decrees that Kerry (Jeremy Allen White) will join his brothers in the ring.

There are a few lovely scenes of the brothers bonding, playing football, doing what brothers do. But the pace of the film, with its wrestling sequences and successive tragedies, doesn't allow for much relationship development. An exception is Kevin's relationship with Pam (a lovely and soulful Lily James), who woos the shy Kevin and eventually marries him, their wedding a brief joyful moment (with an infectious family line-dancing scene).

But tragedy is not far off. For those unfamiliar with the Von Erich tale, we won't reveal more plot here, other than to say that loss does not soften Fritz. At one funeral, he orders his grieving sons to remove their sunglasses, then forbids them to cry.

Efron, with his rock-hard physique and '70s mullet, turns in some of the most affecting work of his career. White, too, is excellent if more inscrutable as Kerry, initially the golden boy until his own brush with disaster sends him into a downward spiral. Harris Dickinson as David and a heartbreaking Stanley Simons as Mike round out the strong ensemble. But the film does not spend a lot of time on the emotional tissue that connects the brothers, who seem more bound by loyalty and mutual hardship than anything else.

The film's emotional ending brings well-earned tears, thanks to Efron's delicate portrayal. But when we're informed by means of an epilogue that the Von Erich family in 2009 was admitted to the WWE Hall of Fame, it's hard not to consider a question that the film doesn't seem to be attacking head-on: Was any of this worth it?