[Source: AP]

At one point deep into “Christy,” the boxer Christy Martin, played with ferocious commitment by Sydney Sweeney, describes how she feels being in the ring. It’s not what you’d expect.

It’s where she finds quiet, she says.

Such a line at the beginning of this two-hour plus film would have been laughable, given that the ring is obviously hectic, loud, bloody — and terrifying, to most of the world.

But when Martin says it, we get it. The ring is where Christy can be in control. Outside — and especially at home, in the bedroom — is where life gets truly scary.

“Christy,” directed by David Michôd, begins as a solid sports biopic, the based-on-true-events story of Martin, a hot-tempered teen from coal-mining country who fell into boxing and became a trailblazer for women in the sport. That’s the triumph part.

But then comes the tragedy: the horrific abuse that she suffered at the hands of her trainer and husband, Jim Martin. And that’s of course where the boxing montages stop. In its final act, “Christy” goes darker than anything we’re prepared for.

The mashup of genres may feel a bit tonally rough, but it ultimately works, not least because of its unifying factor: Sweeney, who imbues her no-holds-barred portrayal of Martin with both sweetness and rage, with brio and real vulnerability.

The actor’s background in MMA fighting was clearly essential for the role, for which she bulked up considerably (a la De Niro in “Raging Bull”) and trained extensively. (She also donned a brown mullet wig and wore brown contact lenses, further distancing herself visually from Sydney Sweeney the movie star.)

We begin in 1989 in small-town West Virginia, where Martin lives with her parents, a loving but weak father (Ethan Embry) and an obtuse and intolerant mother (Merritt Wever).

This is not the environment in which a gay teenager can hope to thrive or even survive. Fearing her inclinations, they threaten to send her to a priest.

Which is why, when Christy gets the chance to make $500 in a boxing match thanks to a local promoter, she grabs it. At the gym, she meets a trainer, Jim (Ben Foster, a bumbling and eventually chilling villain in an ugly combover).

He has no interest at first, and sends a man to spar with her and “break a rib if you have to.” She cleans the guy’s clock.

Soon Christy’s living away from home in a cheap apartment, training full time. “I think I’ve found my thing,” she says. Unfortunately, being trained by Jim also means having to submit to him in other ways.

She goes home, but he lures her back with promises of better fights in Florida, life near the beach, and a meeting with super-promoter Don King.

Well, Christy doesn’t get the beach but she does get … a husband. Jim, increasingly jealous and paranoid, makes a highly unpleasant marriage proposal. Christy obviously feels she has no choice.

Ultimately, she gets her meeting with King.

The promoter likes her pluck, and offers her a contract. “Coal miner’s daughter,” he says approvingly (Chad L. Coleman, bringing humor to the role).

He also likes that she wears pink.

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