Joe Carman and Clayton Hoy in "The Cage Fighter." Sundance Selects

The straightforward, elemental documentary “The Cage Fighter” suggests that many of the clichés of boxing and wrestling movies — about not being able to resist a last fight, about the ring’s lure being a force more powerful than love — aren’t clichés at all, but simply true to life.

With a bare-bones, direct-cinema style and only scant context, the movie — the first directorial feature from Jeff Unay, who has worked in visual effects — plunges viewers into the world of Joe Carman, a mixed martial arts fighter in Washington State. In the first scene, Mr. Carman is 39, hardly a prime age for grappling. The question that emerges is whether he knows it’s time to call it quits.

Trailer: ‘The Cage Fighter’

A preview of the film.

By SUNDANCE SELECTS on January 30, 2018. Image courtesy of Internet Video Archive. Watch in Times Video »

Mr. Unay often shoots Mr. Carman in wide screen at close range, emphasizing the physical strain of his routines, whether he’s running, training or doing mechanical work for a ferry system. Part of the secret of the movie’s interest is that Mr. Carman is not invincible or a former superstar. We’re told that he doesn’t even make money off cage matches.

Yet the damage they do to his home life is real. “It’s the only time in my life when I feel proud of myself,” he tells dismayed family members who have just learned that he is fighting again, despite having promised his ill wife never to get back in the ring. Fighting, he says, allows him to feel that he likes himself. Mr. Carman is shown throughout the film as a loving parent (we see him dancing with his daughters and making them pancakes), but he can’t check his pride. Fighting means being in a cage in more than one sense.

“The Cage Fighter” is hardly epic in scope or originality, but it is uncommon to watch this degree of open self-flagellation on screen. Mr. Carman insists to one of his daughters that having a black eye doesn’t count as being “hurt” and visits a doctor who wonders whether his symptoms indicate post-concussion syndrome. He appears in court when an ex-wife wants to relocate and sits stoically when the judge implies that he is the less dependable parent.

“The Cage Fighter” is not riveting from moment to moment, but Mr. Unay allows the movie’s themes to click into place beautifully toward the end, when Mr. Carman shares a moment of rapport at a bar with a competitor — and learns, to his surprise, that his younger rival is every bit as mortal.