“The Iron Claw” Cast Say They Felt 'Very Vulnerable' Wearing 'Tiny Spandex' Briefs (Exclusive)

"And we were full-body shaved by our wonderful makeup department," Harris Dickinson tells PEOPLE

In The Iron Claw, Zac Efron, Jeremy Allen White and Harris Dickinson play the legendary Von Erich brothers, who made history in the world of pro wrestling in the early 1980s. The three got close fast while training in the ring months before production got underway in Baton Rouge.

Another thing that drew them together? Their "tiny" wardrobes.

"We definitely had to put vanity aside and get used to inhabiting these clothes," Efron, 36, tells PEOPLE in this week's issue of first trying on "these tiny spandex sort of things," as Dickinson, 27, describes the wrestling garments.

"Those were the early days of meeting each other as well," Dickinson (Triangle of Sadness) says. "And we were full-body shaved by our wonderful makeup department."

Adds White (The Bear), 32: "I felt very vulnerable all the time. The wardrobe was so important to the men at the time. You had to commit... or else."

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Related: Zac Efron's Iron Claw Costar Stanley Simons Sang a High School Musical Song to Him on Set (Exclusive)

The actors ate thousands of calories a day and trained for months to play Kevin Von Erich (Efron), Kerry Von Erich (White) and David Von Erich (Dickinson), sibling wrestling champions who deal with familial struggles and try to live up to the expectations of their father, famed wrestler Fritz Von Erich (Holt McCallany).

Kevin is the only surviving Von Erich brother, a group that also includes Mike Von Erich, played by Stanley Simons, and Chris Von Erich, who is not depicted in the film.

The retired professional wrestler, now 66, appeared at the world premiere in Dallas in November alongside the cast, where he told PEOPLE that Efron "had a tough job" in stepping into his shoes.

"It's not easy to be me. I wrestled seven years World Class, but then I wrestled 22 years," Kevin said. "That's a whole lot to cram into a movie, but he was able to do it ... he's a real star. They all are."

For more on The Iron Claw, pick up this week's issue of PEOPLE, on newsstands Friday.

The Iron Claw is in theaters Dec. 22.

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