Zac Efron Reveals Why Underwear Scenes In Iron Claw Were 'Uncomfortable'

While speaking with Metro UK, Efron explained just how uncomfortable he was getting down to his tighty whiteys in front of the cast and crew for his role in Iron Claw, calling the awkward experience something he's never dealt with before.

"It's a very uncomfortable arena just to be in, physically, of course, but a lot of that stuff, once you're doing it, it becomes a part of your body, sort of like dancing -- so you're in it,'" Efron said of the wrestling matches he trained to perform in the film.

The film tells the true story of the Von Erich family, who are plagued by both triumph and tragedy amid their rise to wrestling superstardom.

The 36-year-old actor, who played real-life wrestling legend, Kevin Von Erich in the film, continued, "One of the jarring moments that I wasn't expecting was when the wrestling stops, or there's a cut, or in between setups or takes -- you've just got to stand there with a whole crowd around, in your underwear. And there's nothing really going on."

Despite putting on 15 pounds of muscle and being in, quite possibly, the best shape he's ever been in, Efron said being that bare felt a "bit unnatural."

"That's a different kind of feeling. I've never experienced that one before," he added. "You just kind of gotta… like, where do you put your hands? On your hips? You can't help -- there are people everywhere, you can't look up and have somebody not looking back at you! So that was a bit unnatural."

Like all things, though, Efron said, "You get used to that too."

He added, "It was all very uncomfortable, but I think so is everything great when you're learning it."

Efron's incredible physical transformation for the part was documented in the months following the film's December release, with the High School Musical alum working out multiple times a day to get into fighting shape.

But getting to that peak of physical fitness came with its ups and downs, including Delayed Onset Muscle Soreness (DOMS) which can last between three to five days after a workout.

"It's a combination. You're sore a lot. It's called delayed onset muscle soreness (DOMS), and they get pretty debilitating. It's hard to move around and you just feel old," Efron explained. "But other than that, there's so much adrenaline. I think when you're in the ring wrestling, you kind of become invincible."

He continued, "I don't know what I could relate it to other than skateboarding when I was a kid -- but you can do incredible things and the pain is dissociated from your mind, until you get home later that night, and you're like, 'F--k man, what did I do?' and your ribs are broken or something.'"

In the end, the training paid off, with Efron, who starred in the film alongside Jeremy Allen White and Harris Dickinson, sharing that all those grueling hours in the gym went into the way he developed his character.

"There was so much of the way that you feel, the way that you walk, the way it changes your demeanor -- all of that goes into the character in one way or another, so it all became one kind of process," Efron shared before thanking the stunt team and those in the ring that helped make the wrestling scenes as real as possible.

"I can't give a big enough shout-out to the guys we worked with out there. We had an incredible stunt team, and the guys in the ring really took care of us. I think they recognized that we had an enthusiasm and a passion to make this as real as possible and that just fueled them to take extra care of us and teach us little nuances and point out things," he added. "We developed this real comfortable relationship where any tweak, any note, is welcome, and that really helped a lot."