San Francisco Frontiers - By the power of great skills: Nicholas Galitzine on He-Man transformation

But for actor Nicholas Galitzine, the transformation into the muscular 1980s hero required a Herculean effort.

"I wish I could just point the sword in the sky, and then transform," laughed Galitzine, who stars in the film which hits US theatres on Friday.

"But no...it was a massive undertaking," he told AFP.

For months, Galitzine's routine revolved around eating a lot (or a little, depending on the phase), lifting weights, and doing cardio whenever he had a spare minute.

"I knew it was going to be really, really hard, but I don't think I realized how mentally strong you have to be if you're going to do this thing," said the Briton, who spent much of the process enviously eyeing the food his friends were eating.

"You're working out five, six days in a row, and you come into work, and you just really, really, really don't feel like doing it.

"You have to tell yourself: 'no matter what, I'm not missing a workout today.'"

Before mastering the universe and his caloric intake, Galitzine turned heads as Prince Henry in the adaptation of gay romance "Red, White & Royal Blue," and wooed Anne Hathaway as a boy band singer in "The Idea of You."

The 31-year-old didn’t grow up watching He-Man's adventures, much less the 1980s big-screen adaptation of the Mattel character starring Dolph Lundgren, but he said he was drawn to the project as soon as he read the script.

The actor said he was "laughing almost all the way through it. And as soon as I finished the script, I called my agent and I said: 'I need to do this movie'."

Humor, he said, was a key part of the film directed by Travis Knight, co-founder of the stop-motion studio Laika, responsible for hits like "Coraline."

"How we meet Adam, there's a lot of comedy... he's a bit of a goofy guy, not totally comfortable in his own skin, so there was lots of material to play with."

The actor shared the screen with "Riverdale" star Camila Mendes, in the role of his friend Teela, and fellow Brit Idris Elba who plays Duncan, Adam's close friend and mentor.

The trio faces off against the evil Skeletor (Jared Leto) and Alison Brie, who plays his right-hand woman, the sorceress Evil-Lyn, in a fight for Eternia.

For Mendes, 31, taking on the role of a strong heroine was a longed-for opportunity.

"Teela is sort of that grounding force throughout the film," she told AFP.

That grounding role is seen in interplay between Teela and both Adam, and Duncan, her father.

"There's humor in watching Teela get frustrated with the two of them because they're sort of all over the place, and she's like, 'Oh, great, I have to do it myself once again,'" she laughed.

Mendes described the intense physical preparation for the role as "the happiest time" of her life.

"All I was doing was going to work and getting to twirl a sword around and twirl a bow staff around," she said.

"It was really cool."

V.Perez--SFF