KANSAS CITY, Mo. » Turning your body into that of a god is a weird process.

Chris Hemsworth knows. Once he was tapped to play the title character in "Thor" (opening today), the Australian actor threw himself into a bodybuilding regimen that would transform his solid but unspectacular physique into one worthy of a Marvel superhero.

"I don’t naturally have the kind of weight Thor has," Hemsworth said. "I ate tons of protein. Worked out a lot. I’ve always been pretty active, but nothing on this scale.

"It’s deceptive. It’s such a slow process that when you look in the mirror every day you don’t realize the subtle changes. Everyone else around me was saying, ‘Oh, my God, you’re huge.’ And I’m looking in the mirror and thinking, ‘It’s not working. I’ve got to eat more!’"

In fact, Hemsworth said, he went a bit too far.

"I put on too much muscle. A few days before shooting was to begin we realized none of my costumes fit. I had to crash diet just to squeeze into them."

Hemsworth, 27, said that playing a comic-book hero has special challenges. Foremost among them is ensuring that Thor’s human side is as compelling as the action and special effects.

"Our big focus was on how to make Thor relatable. These are gods speaking to each other, but on the other hand, these are fathers and sons, brothers. We can all relate to that.

"So it was all about humanizing the gods and finding the truth in their lives. And once you find it, to not drift away into all the big colorful things a movie like this can become."

THE STORY finds the arrogant Thor banished from Asgard by his father, Odin (Anthony Hopkins). Sent to Earth, he must create a new life surrounded by mortals.

Grounding "Thor" was director Kenneth Branagh and a supporting cast that includes Oscar winner Natalie Portman, Idris Elba, Stellan Skarsgard, Ray Stevenson and Rene Russo.

While he’s best known for filming Shakespeare classics like "Henry V," "Hamlet" and "Much Ado About Nothing," Branagh grew up reading "The Mighty Thor" comic books, Hemsworth said.

"So, really, he became the perfect blend of fan and careful filmmaker. He knows story and character development. He certainly knows how to assemble a production. With a film like this it’s too easy to get lost in the effects, but Ken was all about story, character, the relationships. His vision of Thor was that of a man looking for his place in life, and he made sure we all concentrated on that."

Last week Hemsworth once again suited up as Thor as the follow-up, "The Avengers," went before the cameras.