On April 15, 2013, two homemade bombs exploded in Boston, near the finish line of the city’s famed marathon. Three people died. Hundreds were injured. Sixteen people lost limbs. In the movie Stronger, which premieres this month, Jake Gyllenhaal portrays survivor and double amputee Jeff Bauman, who came to embody the motto that emerged after the tragedy, “Boston Strong.”

The movie, based on his book of the same name, dramatizes Bauman’s recovery and his path back to walking.

“It’s a story of what it takes to move beyond a dark place into light, into hope, into life,” says Gyllenhaal, who spent months with Bauman to prepare for the role. The two are now close friends. Bauman, 31, considers Gyllenhaal an older brother.

“When we started to hang out, I’d catch him trying to copy some of my mannerisms,” Bauman recalls of working with and getting to know Gyllenhaal. “He put so much effort into the story.”

Role Prep

For Gyllenhaal, 36, film is a family affair: His father is an Emmy-nominated film and television director, his mother an Oscar-nominated screenwriter, his older sister, Maggie, a Golden Globe-winning actor and 2010 Academy Award nominee.

Gyllenhaal made his screen debut at age 10, when he played Billy Crystal’s son in the 1991 comedy City Slickers. Five films later, in 2001, he starred in the cult hit Donnie Darko. He received an Academy Award nomination for Best Supporting Actor for his role as Jack Twist in Brokeback Mountain, the tale of a complex romance between two cowboys. He went on to star in many notable films, including Zodiac (2007), Source Code (2011), and Prisoners (2013).

Gyllenhaal combines abundant talent with an often punishing work ethic. To prepare to play a Los Angeles police officer in End of Watch (2012), he spent 5 months doing ride-alongs with the Los Angeles Police Department. He witnessed a murder the first night. He trained as a boxer for Southpaw (2015); his 5-month regimen, which included 2,000 situps daily, added 28 pounds of muscle to his 6-foot frame.

In the previous year’s Nightcrawler, he played Lou Bloom, a relentless cameraman who profited from the television news demand for crime, violence, and gore. To better capture Bloom’s gaunt, hungry persona, Gyllenhaal reportedly ran 15 miles a day and followed a kale and chewing gum diet. He shed 30 pounds. Recently, though, he says he has started to step back from this sort of self-inflicted punishment.

“I used to go so far into creating a character that it only felt legitimate if it was painful,” he says. “But as you grow older, you evolve, if you’re open to it. Now, I feel there must be joy, there must be humility. I’m trying to cultivate more of that. The journey of making Stronger has taught me a lot about that.”

His lessons in joy came, in part, from laughter. To Gyllenhaal’s surprise, humor after tragedy became a dominant theme, both in the film and on set.

“It’s that humor, that wonderful perspective, that got Jeff through,” says Gyllenhaal. “That’s a huge part of the movie, and its life-affirming tone brought a different perspective than I’ve ever had on events like this. We were laughing all the time.”

He and Bauman even poked fun at Gyllenhaal’s reputation for total immersion in the characters he portrays. “Jeff and I always joked that I didn’t go all the way,” says Gyllenhaal, laughing. His legs, after all, remain intact.

Road to Recovery

The film — the first made by Gyllenhaal’s production company, Nine Stories — does not flinch from Bauman’s pain. He was standing just a few feet from one of the bombs when it blew up. The blast mangled his legs, and doctors amputated both of them about 4 inches above the knee. The film depicts the removal of Bauman’s sutures during an agonizingly long scene. Viewers watch the hands and hear the voices of the surgeon and nurses as they work. (The surgeon in the scene was Bauman’s real-life surgeon, Jeffrey Kalish, MD, of Boston Medical Center.)

“It was very important that we elongate that scene, that we show the pain that he goes through,” says Gyllenhaal. “Things like this bombing happen in the world all the time, but what we don’t hear so much about is the recovery of the people who survive, how their lives are changed, what they feel.”

David Crandell, MD, led an essential part of the recovery after the bombing. The medical director of the amputee program at Spaulding Rehabilitation Center in Boston, he treated all but one of the lower leg amputees, including Bauman.

After an amputation, patients work through muscle-building exercises to prepare for their prosthetics. They also focus on wound management. Infection remains a risk even after the initial injury has healed. Patients must be careful about hygiene and signs of trouble, such as abrasions or blisters that can happen if the prosthetic does not fit properly. Minor irritations can become major problems if infection sets in.

Patients also need to be prepared mentally for life without legs. To that end, rehab doctors often pair a new amputee with a peer who has had an amputation. That, says Crandell, conveys a powerful message: “When you see someone walk in the room with their prosthesis, it gives you the idea that, despite where I am right now, life is possible.”

Bauman’s prosthetic legs cost approximately $100,000 each when they were fitted nearly 3 months after the April bombing and were among the most technologically advanced then available. Still, says Crandell, he and the other survivors — as well as anyone who faces the loss of a leg — do all the work.

“People think that when you have an amputation, technology will fix it,” says Crandell. “But the wearer provides all the power. Their new legs are not robotic. They just help control the force that the wearer creates.”

For the film’s final moments, which portray Bauman’s first steps on his new legs, Gyllenhaal spent months studying the very particular ways Bauman moves. He also worked with Bauman’s physical therapist at Spaulding and was fitted for a pair of Genium prosthetics, identical to Bauman’s. Gyllenhaal says he’s awed by what amputees like Bauman must accomplish.

“Jeff had to recalibrate everything in his body and mind so that he could walk with these new legs,” he says. “That process was very important for me to understand.”

Trauma also brings with it significant, sometimes debilitating psychological fallout. For weeks, Bauman had night terrors and woke to the sound of explosions. Crandell says many of the survivors had similar experiences, symptoms of acute stress disorder, often a precursor of posttraumatic stress disorder (PTSD).

Bauman had other, persistent troubles, such as depression and symptoms of PTSD. He lost sleep for 3 years. Last year, though, he began therapy for his emotional injuries. It’s brought him closer to his 3-year-old daughter, Nora, and enabled him to return to college this year.

“I’m working really hard at my trauma, at my depression,” he says. “I’m dealing with everything head-on by talking.” Still, he has yet to settle fully into his new life. “It’s hard to find my new normal with Jake Gyllenhaal playing me, you know?”

Work Hard. Repeat.

Throughout the production, Gyllenhaal ran up to 15 miles a day to keep in shape and unwind. He recognizes the irony in running while making Stronger, but he says that it became a way to acknowledge the gratitude he felt that he was able to do it. He drinks a lot of water to stay hydrated, but his overall philosophy on diet and, in a broader sense, lifestyle, focuses on balance. Enjoy yourself — within reason — and you will be healthier in body and spirit. Work hard, but make time to relax and rejuvenate.

“I do know that rest is really important in order to give your all, so I have started to learn how to do that,” he says.

But Gyllenhaal likely will never be easy on himself. His dedication to the art and craft of acting and to the characters he portrays won’t allow it. Doubt also drives him. Would he have been strong enough to face what Bauman endured? He doesn’t think so. Was all the work he did to prepare for this part enough, having never lived with pain like Bauman’s?

“That’s what I grappled with, that I’ll never be able to understand,” says Gyllenhaal.

So he pushed himself as hard as he could and now has to trust that he got it right.

“It’s inexplicable how much responsibility I felt and still feel towards Jeff,” he says. “I think he knows that. I hope he knows that. All that matters is that he knows how much I tried.”

Traumatic events like the Boston Marathon bombing often do more than physical damage. They can also cause psychological harm. Symptoms include:

Nightmares and flashbacks that vividly recall the event
Changes in how you feel and how you view the world and other people. For example, you may feel less safe, less interested in things you once enjoyed, or numb.
Avoidance of thoughts or situations that remind you of what happened
Hyper-arousal, which means you’re easily startled, always on guard, and have trouble with sleep

Symptoms like these may be normal in the first 3 days, says psychiatrist and trauma specialist Eric Bui, MD, PhD, of Massachusetts General Hospital in Boston. They become a real concern if they continue for more than a month.

“That’s when we call it posttraumatic stress disorder, or PTSD,” says Bui, “and that’s when we can start treatment.”

The most effective treatments include:

Trauma-focused cognitive behavioral therapy: Talk therapy that addresses and helps you change the way you think about the trauma
Medications: The most common are antidepressants such as paroxetine (Paxil) and sertraline (Zoloft).

Recognize when you need help, Bui urges: “Even if it is difficult to talk about what happened, I encourage you to seek trauma-focused therapy.”