Skinny farm kid Garrett Hedlund transformed himself into Tron‘s hero. All it took was hard work and the threat of a skintight suit.

Other kids practiced to make the track team. Garrett Hedlund didn’t have time for that, so he chased cows instead.

His family’s 400-acre cattle farm in northern Minnesota was at the end of the bus route, 2 hours from school. When he arrived home, he spent his time plowing fields and mending fences. But Hedlund wanted to be the fastest kid in his grade school, so chasing wayward bovines during weekend cattle runs became his practice. “Everybody else would drive a truck or a four-wheeler, but I’d go out in my boots,” says Hedlund, the country lilt still in his voice despite 8 years of living in Los Angeles. “When a spooked cow took off, I’d run as fast as I could to chase him back to the herd.”

Soon he was one of the best runners at his school. His speed propelled him into wrestling, football, and cross-country. These things tend to snowball: You prove to yourself that you can succeed at one endeavor, and that gives you the confidence to try another. “You’re gaining the strength to conquer obstacles,” Hedlund says.

Perseverance became habit, and that habit kicked in when Hedlund made the leap to acting. He had to train heavily for supporting roles in Troy and Friday Night Lights. But then he reached leading-man territory with the big-budget Tron: Legacy, and all that prep just wasn’t enough.

“When Garrett came in, he was a little skinny and a little soft,” Tron‘s lead training instructor Logan Hood says. Hedlund’s character is a futuristic gladiator, a guy who’s playing a video game from the inside as he hurls discs at opponents and competes in a vicious version of motorcycle roller derby. “We needed him to look more like an action her – lean with muscle mass.”

For men with competitive spirits – and Hedlund counts himself among them – a challenge can be rousing in itself. But vanity is also a fine motivator, and Hedlund had reason to worry: He’d be wearing a skintight action-hero bodysuit throughout the movie. “They do a body scan so they can formulate the suit around you. It’s three-quarters of an inch of foam rubber that fits you like a glove,” he says. “If you have a belly, your scan’s going to have a belly.” In other words, he needed to shape up. Fast.

Hedlund had been there before. His career sputtered for years because he was either too big or too small for the roles he wanted. He was passed over for the role of a soldier-type guy. Too thin. So he worked out and put on weight. But then he was too bulky for the skinny-intellectual part that came up next. Eventually, being able to quickly transform his body (and convince skeptical casting agents that he could do it) became a matter of survival.

There are easy ways to shape-shift, of course: You can starve yourself, or overeat, or just do curls all day long. But Hedlund knew such tactics would be unsustainable and downright dangerous. He’d be yo-yoing through cycles of muscle-imbalance injuries, plus giving in to the inevitable bounce-back binges that follow extreme dieting.

Real weight control requires commitment; once you build a healthy foundation, your body will transform in whatever way you need it to. So during those lean years of his acting career, long before he could afford a gym membership, he regularly ran 2.2-mile loops around the reservoir near his L.A. apartment. Then he’d head home for what he calls “a living-room prison workout” of pushups, situps, pullups, squats, and squat thrusts.

But squat thrusts alone don’t make an action hero. Which is why Hedlund turned to Hood, a former Navy SEAL who had helped train the conspicuously toned cast of 300. Hood had 9 weeks to do with Hedlund what normally would take 6 to 12 months. The plan: “Garrett didn’t repeat any workouts, which helped keep him engaged,” the trainer says. “If you don’t know what you’ll be doing when you walk into the gym, you don’t fall into a rut.”

Hedlund didn’t love the work at first. “But then he started to connect the dots: Doing stuff he didn’t like was going to make him good at the things he does like,” Hood says.

In addition to slimming him down and hardening him up, Hood focused on Hedlund’s shoulders. Strength there is key for any physical demand, action sequences included. Without strong shoulders, you’re more likely to injure yourself.

Hedlund started as a sloucher, but by the time filming began, he was walking into the gym with swagger. It wasn’t just confidence showing, though: It was the result of stronger core and back muscles, which helped his posture and gave him a visible physical confidence. “If he stands taller and pulls his shoulders back and down, he looks more imposing, more heroic,” Hood says. “Body-fat percentage doesn’t matter. It’s really about how you look.”

And how you feel.

“You might think the thinner version of yourself is going to be the most positive or confident, but that’s not how it is for me,” Hedlund says. “When I’m over 200 pounds, that’s when I’m the most confident version of myself.”

But he’s also comfortable with a less sculpted self. Perfection is never what he strives for. That’s an impossibility; being afraid to screw up only limits you. It’s why Hedlund says he thinks of life as a new car- one you’ve already scratched. Now you’re free to roam a little looser, to take gravel roads, no longer fearing a ding or a dent.

There are many correct ways to do something, and a setback isn’t the same as a failure. That singular insight is the source of his confidence, he says. It’s what allowed him to overcome all the bumps a farm kid hits as he auditions and struggles and finally breaks through in Hollywood.

Where did he learn that? Maybe back home: When Hedlund was 10, his best pal was a steer he raised for competition. The animal won a blue ribbon. “I came home from school one day and the steer was hanging from the tractor bucket,” he says. It was a shock; he was so focused on nurturing it that he never considered what came next. But after a good cry, he had no choice but to accept that dinner came from the backyard. “Now when somebody says, ‘I saw a bird die when I was 3 years old and I don’t eat meat,’ I’m like, ‘Are you kidding me?’ ” he says. “I eat steak. I eat everything.”

You’re slapped down, you learn, you adjust and move on.

This winter will be huge for him. His career will change. Tron is a legend relaunched, and Country Strong puts him alongside Gwyneth Paltrow and Tim McGraw in the kind of open land that was his first training ground. There’s an endless horizon when you live at the end of the road in Minnesota. There’s also an endless yearning for forward progress. Garrett Hedlund is on his way.