To uncover the secrets of longevity, Chris Hemsworth put his body on the line

Chris Hemsworth plunged into Arctic waters, dangled a thousand feet over a canyon while climbing a rope, fasted for four days, and prepared for his own eventual death–all in the pursuit of living longer.

In Limitless With Chris Hemsworth, a six-part National Geographic documentary streaming on Disney , the actor doesn’t just rely on a physique honed during a decade of playing Thor in movies. In his quest to improve life-extending habits, he challenges both mind and body. His and ours.

Experts guide him. Some of their tips may sound familiar: Eat less, exercise more, but others are less appealing: Accept reality. Take control of your stress. (What wild baboons can teach us about aging)

Before this project, Hemsworth had “always trained specifically for a movie,” where the goal might have been “to have abs this summer or whatever. It was superficial. It was more superficial.

Limitless–which took more than two years to complete, given pandemic shutdowns and breaks for Hemsworth’s movies–stemmed from a 2006 film that producers Darren Aronofsky and Ari Handel had written: The Fountain, about a man searching for everlasting youth. Handel recalls a line that still resonates today: “Death, it’s a disease, like any other.” There is a cure. A cure–and I will find it.”

Nearly two decades ago, they worried the idea was implausible for audiences. Now, with an aging population and high-tech companies “trying to beat death and reaching for immortality in a lot of different ways,” Aronofsky says, it doesn’t seem as far-fetched.

The team created a series about longevity with Nutopia, a production company. It was both informative and entertaining. Although Hemsworth is not able to perform complex stunts, there are lessons for viewers at home. Jane Root, executive producer of Nutopia, says that it’s less about extending life but more about improving your chances of living a fulfilled and happy life. How active? In Norway, to study extreme temperature’s effects on the body, Limitless had Hemsworth swim and surf in a fjord’s 36-degree water. Aronofsky–who managed a numbing dip himself–said it was “an amazing experience to … see Chris really pushing himself to the edge.”

To push that hard takes exceptional drive, says Ross Edgley, who coached Hemsworth’s fjord swim. A sports scientist and the only person to swim around Great Britain (some 1,790 miles), Edgley also helped him train for the movie Thor: Love and Thunder. “People know Chris as the actor, but not a lot of people know him as the athlete,” he says. Hemsworth was a hurdler in school and still surfs. (Athletes are going faster, higher, and farther–thanks to technology and smarts)

In Limitless, Hemsworth plays underwater hockey during a four-day fast, part of a test to measure fasting’s potential benefits. Hemsworth jokes about being hungry, but tends to keep his mood light. But there’s a dark moment when Peter Attia, a preventative care physician, tells Hemsworth, then 37, that blood tests reveal he has 10 times the average risk of developing Alzheimer’s disease because of genetic traits. Attia says that daily exercise, good sleep and stress reduction may help lower this vulnerability.

” “It was initially quite scary,” Hemsworth said. “But now, because of this information, there’s an opportunity to live an even better life.”

Hemsworth’s extreme feats in the series include walking on a two-foot-wide construction beam 900 feet above Sydney Harbor. Yet, it’s the simple scenes of the finale–an episode about accepting death and reality–that help us understand why we long to live longer. Hemsworth experiences some aspects of old age for a few minutes at a time. He wears an MIT-designed suit that adds weight and restricts movement, hearing, and vision, mimicking how he might feel in his late 80s. He listens to people who are close to death and reflects on what matters. He is then led to an older woman and seated with her back to him. The second he touches her shoulder, he recognizes Elsa Pataky, his wife, who is wearing extensive aging makeup. He turns to her and they hug.

The show team didn’t warn Hemsworth of this encounter. They wanted his natural reaction. He suddenly realizes he is nearing the end of his days and is trying to figure out why he will sweat, freeze, or starve. Is it all down to love?

“Absolutely,” Hemsworth says, a smile creasing his face. “One of the first questions I had from Peter Attia was, What does your life look like in 20 years … in 30? What does your death look like?”

Hemsworth pauses. Then he says, “A good death for me would be having lived a good life.”