Starting an acting career at age 10 ensures some loss of childhood. Or, in Jake Gyllenhaal‘s case, a deferred one.

Playing an action hero in Prince of Persia: The Sands of Time, the video game adapted for the big screen that opens Friday, Gyllenhaal experienced some of the kid time he missed the first time around.

“It can be argued how much of a childhood I had,” Gyllenhaal says, looking back on his first role in 1991 as Billy Crystal’s son in City Slickers, followed by a key part in October Sky (1999) and his breakout title role in the cult favoriteDonnie Darko (2001). “I don’t think I wanted to be a kid then. And now I do. I think that’s primarily the reason for doing this.”

He’s in good company

Hollywood has found much to be childish about in recent years. From toys (Transformers, G.I. Joe) to comic books (Iron Man) to campy ’80s television (Charlie’s Angels), the industry is trolling the recesses of our childhood.

And, for the most part, it has worked. Comic-book adaptations have been the industry’s stalwart the past five years, and in 2008 The Dark Knight became the third-highest-grossing movie of all time with $533 million.

But to the chagrin of filmmakers, comic-book devotees are not necessarily gamers. And of the 28 video games translated to the big screen, only one, Lara Croft: Tomb Raider, crossed the $100 million mark, earning $131 million in 2001, according to Box Office Mojo. Most video-game movies do an average of $32 million.

“I’ve gotten two questions since I started making this movie,” says Persia director Mike Newell. “The first is: ‘Why are you doing this to my game?’ The other is, ‘It better be good.’ I guess that’s not a question, but you get the sense of it.”

The not-so-veiled threat was enough to keep Newell’s ear to the ground for “Net grumblings,” positive and negative, about Prince of Persia. And it turned the typically reserved Gyllenhaal into Adonis mode.

Lightening up

At 29, Gyllenhaal is in the prime of his career. For someone so young, he has tended to play notably somber roles, such as the gay cowboy in 2005’s tragic Brokeback Mountain, the violent Marine in 2005’s Jarhead, the driven police detective in 2007’s Zodiac and the black-sheep sibling in last year’s Brothers.

With this epic action-adventure tale set in a mystical land, Gyllenhaal goes lighter, or at least less tortured. He plays Prince Dastan, an orphan adopted by the King of Persia. Brave and pure, Dastan proves his mettle through his efforts to save the world from dark forces intent on destruction and domination.

“For a while I thought that to be a skilled actor you had to do things that were torturous,” he says. “Now I feel more like having fun and enjoying myself.”

And the actor is no stranger to the video game.

“I played Prince of Persia when I was 8 years old,” he says. “I took a 20-year hiatus from playing video games. I don’t play a lot now, but I did for the movie. My joke is that I do a lot of research before I do any movie. Playing video games was my research. I played Scheherazade (a Nintendo video game) in the trailer.”

But it will take more than exuberance among the stars to push Persia to profitability, says industry analyst Michael Pachter, managing director of Equity Research.

Gamers are already used to star-studded (voice) casts, top-notch effects and budgets that can, in the instance of the original Grand Theft Auto, reach $100 million.

“These aren’t kids who are easily impressed,” Pachter says. “If you look at the (video games) that moderately worked, they’d be Lara Croft and Resident Evil, and both had great stories. That’s the key. Mario Brothers may be a fun game, but no one wants to see a movie of someone butt-stomping mushrooms.”

Newell brings a non-gamer’s perspective. The director of Mona Lisa Smile and Harry Potter and the Goblet of Fire says he asked his assistants to educate themselves on the game series, which began in 1989, but little more. He says he considers the video game simply a powerful diving board into these new waters.

Video games “don’t start with human emotions, as most stories do,” Newell says. “So you have to teach yourself to use the character’s world — his guns, his clothes — to color the water. But then you have to paint the human gymnastics, and that’s fun.”

Newell says of all the challenges he faced in adapting the game, getting Gyllenhaal to play ball wasn’t one of them.

“He turned not just into a video-game star,” Newell says. “He became an action star. He’s always been known as a thoughtful guy. But he dove into making his body fit the armor, too.”

Channeling Indiana Jones

During the making of Persia, Gyllenhaal says, he was reminded of the Indiana Jones series and The Goonies, movies that he has enjoyed since he was a boy.

“I just try to do the movies that I love to watch,” he says. “In this movie we’re wearing these big belts and I was thinking of Star Wars. I was wearing a suit that made me think of Aladdin. Those are the things that touch the kid in you.”

But he had to work out like a grown-up to pull off the action sequences in the deserts of Morocco. The plan was to get in tiptop shape — not just to look the part and impress audiences with his toned shoulders and muscular pecs, but to convince filmmakers he could do some of his own stunts.

“I had trained pretty intensely,” he says, adding that a quartet of stuntmen were also a significant part of his princely persona.

“Even though five guys actually do make up the character, I didn’t want to do the lines and then fall onto a pad,” he says. “I knew that if I got myself into good enough athletic shape where I had confidence that I could pull it off, people would see that I could and they’d let me do more. And it actually worked out that way.”

But it took a bit of on-the-job convincing.

“At first, everyone was really wary and weird about it,” says Gyllenhaal. “Then I’d slowly do one thing after the next and they’d put me into something a little bit more dangerous.”

Adrenaline-fueled peril presented itself in a variety of ways.

“I was most scared about the big jumps,” he says. “As we got farther and deeper into shooting, five months into shooting, we were trying stuff. There’s a jump I do where there’s like a 20-foot gap between two buildings and a pretty significant drop, like 35 feet, which terrified even the stunt guys.”

But the most harrowing stunt, to Gyllenhaal’s mind, was one that didn’t actually involve him. Oddly, it included an errant bird.

“The scariest scene in the movie is when Alfred Molina kisses an ostrich,” he says. “They are terrifying animals. Anything with a brain the size of a pea and claws that can tear your face apart is really scary.”

The ostriches left a big impression on the animal-loving Gyllenhaal.

“I’ve worked with wolves in movies (on The Day After Tomorrow), and on this set they treated ostriches like wolves,” he says. “They literally told us they’ve been known to rip off people’s faces. So when Fred kisses the ostrich, to me that performance is braver than Robert De Niro in Raging Bull.”

Overall, Gyllenhaal found the Persia shoot an exhilarating, if demanding, one.

“It was incredibly technical, down to the crowds and sword fighting,” he says. “I did the sword fights thousands of times. I was a complete idiot at the beginning. I had no previous experience, and in fact I have two left feet, so the balance of being able to fight with two swords took a long time to learn.”

But Newell says that Gyllenhaal was not only the film’s muscle, but its emotional core.

“With video (game adaptations), you’re always looking for the human equivalent,” Newell says. “You need an actor who can almost breathe emotion. I knew from Brokeback Mountain (Gyllenhaal) could do that. And it didn’t hurt that he could build that kind of physique and look good on a horse.”