Soon after, the bitty, possibly concussed blonde, Rachel (Noa DiBerto), plus the film’s two other leads, Riley (Devery Jacobs) and her girlfriend Amanda (Kudakwashe Rutendo), are bumped up to a more advanced squad where their practices get even harder. Their new coach, a stern taskmaster named Eileen (Evan Rachel Wood), has to remind the squad to smile. Oh, yeah — isn’t cheerleading supposed to be cheerful?

The screenplay by Joanne Sarazen is as grim and obsessive as the girls. Yet, while football players can glower, cheerleaders can’t. It’s a fascinating emotional conflict, even though we only ever see the girls cheer by themselves, for themselves. Here, their sport is squarely center stage, never on the sidelines. The only interloper is a snotty friend-of-a-friend (Madison Seguin) who dares to insult cheerleading as anti-feminist. Riley shuts her down.

“We are athletes,” Riley growls.

It’s an obvious, fist-pumping moment until another cheerleader, Laila (Marlee Sansom), jumps in — this one aggrieved that her thighs were considered too big for the top-tier team. “It’s not just about what we do,” Laila sighs. “Don’t be stupid.”

The actors appear to be doing their own stunts. (Jacobs and DiBerto are gymnasts; Rutendo, a former cheer captain.) The smoothness with which they can deliver a line of dialogue and then hurl themselves into a cartwheel makes their characters feel real, even though their cuts and bruises and abrasions are given more screen time than their outside lives. I spent the first stretch of the film wondering when I’d learn their age or their grade, whether they’re planning to go to college or whether they go to school at all, given their 8 a.m. practices. I never found out because, I suppose, to the girls, the outside world doesn’t matter — particularly to Jacobs’s Riley, who emerges as the most cultish of the three. If Eileen ordered her girls to shave their ponytails, Riley would instantly grab a razor.

“Backspot” will probably draw comparisons to Peyton Reed’s cheeky-smart 2000 teen comedy “Bring It On,” but Sarazen seems far more inspired by Darren Aronofsky’s “Black Swan.” Like that 2010 Oscar winner, this is a body-horror-heavy portrait of sweaty, chest-heaving female fanatics. But where Aronofsky framed the world through Natalie Portman’s torment — we were never sure how much of her nightmares was real — after “Backspot’s” fabulous opening sequence, Sarazen takes us out of her athletes’ point of view and spins the camera around so we’re simply staring at Riley’s face. It’s easy to get so caught up in the breathless way the film shoots Riley, the camera spinning around her when she’s gone dizzy from stress or edging out of focus at the start of a panic attack, that we only gradually realize we don’t care that much about her character. Mostly, we take in Riley’s nervous tic of yanking out her eyebrows. It’s bone-chilling the first time; eventually, it’s just repetitious.

Sarazen is a sharp observer of details. Riley and Amanda’s relationship holds the screen with a warm, credible intimacy. The couple are old enough to shoulder some pressures of adulthood, but still so young that they playfully build themselves a bedroom cuddle fort. They don’t talk much about their home lives — one senses the characters feel it’d be tedious to say the obvious out loud — but the film gets across Riley’s mentally fragile mother (Shannyn Sossamon) as soon as she insists on pouring her daughter’s sports drink into a proper glass. Meanwhile, at Amanda’s affectionate working-class home, there’s a sublime moment when the girl tenses up as her mom (an effervescent Olunike Adeliyi) pulls out a celebratory store-bought cake. We read the quiet fear in Amanda’s face: Can they afford the splurge? As for DiBerto’s Rachel, she’s mostly comic relief — and she’s terrific.

The film is heavy on the dread, light on the narrative. It’s all about the tension in the gym where the adults are just as melodramatic as the girls. The coach’s assistant, played by Thomas Antony Olajide, half-jokes that if the girls dare sing Dexys Midnight Runners in Eileen’s earshot, “She’ll crack your skull open.” But this isn’t a film about rebellion or revenge or even great leaps in emotional growth. Instead, like that bungled toss at the beginning, it’s about micro-adjustments that help the girls find safer footing — like learning that it’s okay, once in a while, to admit when you’re in pain.

Unrated. At the Alamo Drafthouse Cinema DC Bryant Street. Contains underage drinking and gnarly flesh wounds. 92 minutes.