This weekend marks the opening of Kormákur’s $55 million feature film, Everest, one of Hollywood’s most anticipated movies of the fall. With a star-studded cast that includes Jake Gyllenhall, Jason Clarke, Josh Brolin, Michael Kelly, Emily Watson, Keira Knightly, and Robin Wright—there is no shortage of A-listers in the credits. The movie is based on a true story and follows two groups of climbers as they attempt to scale the world’s highest peak.

I attended the premiere of the film last week at the TCL Chinese Theater in Hollywood, and had no idea what to expect. Sure, the trailer looked good, but don’t they all? It’s the other 99% of the movie that typically never lives up to the hype.

I was skeptical when I first heard there was another Everest movie in the works. While there have been a couple of fabulous mountaineering films released in the past, the majority have been cheesy and ridiculous. I’ve climbed Everest twice, so I know what the mountain looks like and what it feels like. I wondered if the new movie would be another adrenaline-junkie film that would mainly appeal to Cliffhanger devotees. I prepared myself for disappointment, because here’s the thing: You can’t out-Stallone Stallone.

But as Kormákur addressed the 3-D goggled audience before the start of the film, he made it abundantly clear that he “didn’t want to sanitize the people and the events.” Rather, he hoped to “humanize them and make them real.” He went on to explain that he shot in temperatures as low as -22F and at altitudes of 16,000 feet. He said he took the cast and crew as high as any insurance company would allow them to go. He wanted his actors to feel the stress and discomfort that’s associated with being up high, because that was the only way he could make sure that what came across in the final cut did indeed feel authentic.

They filmed a great deal of the movie in Nepal, with the balance filmed in the Dolomites in Italy and on a sound stage. I caught up with actors Michael Kelly and Jason Clarke (separately) after the screening, and talked to them about what it was like to film at altitude in the cold temperatures. They both mentioned how difficult it was to be flown right to the shooting location. They didn’t have time to properly acclimatize and were plagued with the headaches, nausea and insomnia that commonly accompany altitude sickness. Bummer for the actors, but another brilliant Kormákur move as far as “keeping it real,” since Everest climbers deal with these ailments on the mountain.

So, how did Kormákur get his celebrity cast and crew to deal with such uncomfortable conditions on top of an already-grueling shoot schedule? He did what any good leader would do: He went through the hardship with them. In his own words: “I think what’s helpful is that I will stay right there with them, in the same conditions, show them what they need to do…So they are more likely to work with you than if you’re sitting someplace warm and telling them, ‘Keep going.’”

Bingo. It’s important for leaders to show their teams that they’re willing to make the same sacrifices and endure the same hardships as everyone else. As a leader, you can never expect the people on your team to be willing to endure anything that you are not willing to endure. By getting out there with his cast and crew, Kormákur was building trust and loyalty—two incredibly important aspects of high-performing teams. And he needed these actors to perform, because they were re-creating scenes that would require them to withstand some of the most physically challenging conditions they had ever experienced.

You may know how the story unfolds: On May 10^th, 1996, several groups of climbers left Camp 4 (which is situated at a place called the South Col at 26,000 feet) and headed for the summit, marching higher and higher into what is known as the “Death Zone.” They call it the Death Zone for a pretty good reason: because once you hit an altitude of about 26,000 feet, human life can no longer be sustained and your body is literally starting to die. Your muscle mass is deteriorating as you climb further and further up. And the more your body decays, the more the mountain demands from you. Summit day’s recipe is one part irony and one part cruelty as you’re tasked with making life or death decisions as your brain is oxygen starved and you’re suffering from hypoxia.

(SPOILER ALERT) The deadliest storm ever to hit the mountain enveloped the climbers who were stranded up high on the mountain. Visibility went to zero. Ferocious winds and ice tore at peoples’ skin. Human beings froze like statues and became part of the landscape on the mountain. Among those who died in the storm were two of the world’s best, most experienced mountaineers. The cold hard reality of mountaineering is that sometimes no matter how good you are, and no matter how experienced you are, things can still go wrong. And plenty did.

Everyone’s efforts to make Everest feel authentic paid off. The mountain scenes feel as real as any documentary. The cinematography and special effects are nothing short of spectacular. After the movie ended, I approached Kormákur and told him that he had made the most realistic mountaineering movie I had ever seen. Variety reported that he was on cloud nine after my comments. At least I know that he’s used to the altitude.

Alison Levine has climbed the Seven Summits and skied to both the North and South Poles. She is the author of the New York Times bestseller On the Edge: Leadership Lessons from Mount Everest and Other Extreme Environments.

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