The Von Erichs were a popular Texas wrestling clan in the 1980s, brothers whose trademark was the Iron Claw wrestling hold.

“The Iron Claw” tells their mostly tragic story. Zac Efron is Kevin the eldest, Jeremy Allen White (“The Bear”) is Kerry. Maura Tierney plays their doting mother Doris while Holt McCallany (Netflix’s “Mindhunter” series) commands as the Von Erich patriarch Fritz, a supreme example of destructive toxic masculinity.

Efron, 36, stands out as the one who most closely resembles their larger-than-life physiques.  “The footage we saw of Kevin in the ring was electric,” Efron said in a post-screening Q&A. “His athleticism in the combat — how light he was on his feet! It looked real. It was real.

“He just had this incredible physique to complement that. I knew going into it that, physically relating to Kevin, I was going to get into that shape.

“To do that,” he discovered, “you have to be obsessed. Before every take, push-ups, pull ups, to get pumped up. It takes over your life. All you’re doing is eating, training, sleeping. And wrestling.

“That’s what the Von Erlichs were doing in real life. Our prep for this movie was we all started hanging out in the ring. Really, our lives outside of that were non-existent.

“That really helped me figure out Kevin’s mindset. Just going into that mode that it was never enough. That really worked. It helped me understand what he was going through. And for 160 days a year! Not just for one movie.”

As people die, as tragedy strikes the Von Erlichs, Efron discovered “an incredibly loving person” in Kevin. “He will go to any length to support and protect the people he loves. One of the beautiful things about this story is he goes through some difficult moments. He gets knocked down — and keeps getting up. That’s why there’s something awesome about Kevin.

“He didn’t have the showmanship on the microphone. But as far as the wrestling went, his physicality was unparalleled.

“I knew I was playing somebody who is still alive. It’s a fine line to make sure it’s an honest portrayal without going so hard it’s an impersonation.

“Knowing he was going to see it was very motivating. I just wanted to make him proud. For filming I didn’t talk to him. Then at the Dallas premiere I got an hour and a half.

“The lengths that he went to for his family – and still does to this day!  He says, ‘It was all about family. And love.’ And he’d do it all again.”

“The Iron Claw” opens Friday