Zac Efron didn’t realize how much he needed a hug.

He’d transformed himself into a mass of muscle and repressed emotion to play professional wrestler Kevin Von Erich in the new film “The Iron Claw.” It was a taxing role and unlike anything he’d done before, both physically and psychologically. He often found himself with real bruises from recreating fights in the ring. Downtime between shots, too, was usually spent lifting.

But he didn't appreciate how much it was affecting him until he and Lily James sat down to film the first date between his character and the woman who would marry him. Pam tells Kevin that he has oldest brother syndrome. Kevin tells her that he’s not actually the oldest: That brother died in an accident when he was 6 and Kevin was 5. He says he’s fine, but Pam gets out of her seat, walks around the table and drapes her arms around Kevin, who seems to melt in the warmth of a love that’s not conditional.

“It felt very needed, that hug,” Efron told The Associated Press in a joint interview with James. “It was the first time I’d embraced anyone in months without it being a fake punch, or someone trying to submit me or get me to tap out.”

Efron is half-laughing but also not. If you know anything about the Von Erichs, sometimes referred to as the Kennedys of wrestling, you know that the tragic death of the oldest brother is not the last that they would endure. In fact, the completely true account of what would transpire was too much for even the film to bear: By the time Kevin was 35 he’d have lost his four remaining brothers, three to suicide. For “The Iron Claw,” in theaters Friday, writer-director Sean Durkin made the decision to take the youngest, Chris, out entirely.

“The Iron Claw” is still primarily about the relationship between the brothers David (Harris Dickinson), Kerry (Jeremy Allen White) and Mike (Stanley Simons) and their father Fritz (Holt McCallany), a wrestler who dreamt of greatness for himself and his family at any cost. Kevin told Durkin that he just wanted audiences to know how much the brothers loved one another.

As a lifetime wrestling fan who grew up following the Von Erichs, who presided over the Texas wrestling scene in the 1970s and '80s, Durkin was fascinated by ideas of American masculinity, trauma and grief, as well as Kevin’s relationship with Pam that somehow survived through it all.

Though Kevin had spoken a lot about his life after the deaths, there wasn’t much Pam “out there,” Durkin found. But instead of a hinderance, it provided an opportunity to be creative and make it personal. He’d already decided that he wanted to write and figure out the story before getting in touch with his real-life subjects.

James joined the project a bit later than everyone else. Efron recalled a “collective jump for joy" upon finding out that she'd said yes. Though they didn't know one another beforehand, they quickly established a natural rhythm that would prove to be magic on camera and off.

“It’s so nice when you meet someone at work and it just instantly kind of clicks,” James said. “Zac made me feel so welcome and at home in our scenes, which are so special and effortless.”

Part of that they attribute to Durkin’s preference for filming long, uninterrupted takes that helped them get out of their own heads. After five minutes, Efron said, you simply forget that the camera is there. But Durkin thinks something even more special happened when it was just them.

“The second we started filming, it was like everything fell away and they were just totally present with each other and just fully responding,” Durkin said. “It was really fun to watch.”

It's not just that you're watching two people fall in love. Pam shows Kevin a different way of living and a different kind of love than he had known, which becomes even more essential as everything he thought he knew about life crumbles around him.

“She's a slight horse whisperer. I was really intrigued by this woman that has such emotional intelligence and directness. She's not afraid to be fragile.” James said. “When Pam just goes around and hugs him, you get the feeling that he never experiences that kind of physical, gentle intimacy. It felt really moving to do that moment because she kind of knew what he needed.”

The hug is a cathartic moment for Kevin, who has been taught to hold back his emotions in real life.

“It was the first time that it really wasn’t about winning or losing and, for Kevin, about being himself and finding meaning outside of the gym and the ring and the world of his family," Efron said.

But Efron didn't expect to feel it too.

“It was overwhelming in the best possible way," he said. "I almost didn’t know how to deal with it. It felt very close to the character."

Efron's committed performance has earned him some of the highest praise in his career. And the fact that he hadn't done anything like it before is part of the reason Durkin wanted him.

“He had the athletic background, the dance background and the physicality and those are great building blocks to being a wrestler. And he has a clear hunger for doing tough work,” Durkin said. “But the ultimate thing was meeting him and seeing how kind and sweet he is as a person. It’s quite a silent role in a lot of ways and having that core was crucial.”

While filming, he said, “A lot of my direction to Zac was ‘don’t cry yet.’ Even in moments where it’s impossible, just hold it in and keep holding it in.”

For Efron, the exploration of repressed emotions resonated. Spending time with Kevin has only helped reinforce its importance.

“I think a lot of men deal with this,” Efron said. “Repressed emotion never leads to good things. It’s something that I’ve definitely had to work on over the course of my career and life. That this movie was about that was intriguing to me. It felt personal.”

But it wasn’t all tears and bruises. They had some genuinely fun scenes to look forward to as well, including line dancing at Kevin and Pam’s wedding.

“It’s just the coolest thing I’ve ever done on camera,” James said.

“You rocked that scene,” Efron responded. “By the way, I didn’t know you had rehearsed. I thought you just knew that dance. I was blown away, I was like, what is going on? How do you know this? Aren’t you British?”

For both, the film was a “real ride" and flush with creative energy and freedom.

“It definitely rekindled something inside me,” Efron said. “I’m in love with this process more than ever. I really needed it. I really did.”