The Fittest People in the World Rarely Break a Sweat
What Nepali Sherpas are teaching researchers about exercise science.
Andrew Murray has spent thousands of hours trekking the world's topmost trails. At the earth's crown, he notices a lot of things: the looming peaks, the lack of vegetation, and the way light plays in the thin air. But as a physiologist, he fixates on the people carrying his stuff. "You'll be huffing and puffing your way up what looks like a fairly gentle slope, but you're held back by the low oxygen," he says. "Then a porter will breeze by you, he's maybe much older than you, and he's carrying your bags and other people's bags, walking like it's a stroll in the park." Murray says this at-altitude fitness is most striking in the Sherpas, an ethnic group in eastern Nepal famous for mountaineering.
His observation is more than happenstance: Nepali Sherpas have evolved to perform like superhumans at altitude, according to a study Murray led that was recently published in Proceedings of National Academy of Sciences. That's what his team from Cambridge University concluded after they discovered that the Sherpas are able to use oxygen more efficiently in low-oxygen environments.
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As you gain altitude, your body responds by producing more oxygen-carrying red blood cells. Previous studies have found that Sherpas do ramp up their red blood cell production when climbing, but at not nearly the rate of lowlanders—which means they actually have less oxygen in their blood than we do while climbing. Murray and his team wanted to know the Sherpa's trick.
To conduct the study, the scientists took thigh muscle biopsies on a group of Sherpas and Westerners at low altitudes. The groups—who were matched for age, sex, and general fitness level—then trekked from Katmandu to Everest Base Camp. Once they arrived at the 17,600-foot camp, the scientists again took the biological measurements.
The biopsies contained the magic: The Sherpas' mitochondria—tiny power plants within human cells that power our bodies—produce more ATP, or energy, using less oxygen at altitude. They also found that the Sherpas used fat as fuel more efficiently. "It's interesting because the Sherpas are actually unremarkable at sea level," Murray says. "You don't see them winning marathons. Their adaptations is not one that gives them super performance at sea level, but it does at altitude when the oxygen is scarce."
In other words, Westerners have the engine of a gas guzzling four-by-four, while the Sherpas are more like a sensible hybrid that sips fuel. When fuel is abundant—at low altitude—both engines get the job done. But when you climb into a fuel-scarce, high-altitude environment, the more efficient engine is optimal. It can help you climb farther, faster, and with less effort.
Even more striking, the team of scientists retook the biological measurements of both groups after they'd spent two months at Everest Base Camp and found the energy levels in the muscles of the lowlanders dropped. Yet like a flower exposed to the sun, the Sherpa muscle energy levels steadily increased despite having less oxygen.
Although the sport of mountaineering was pioneered by westerners, Sherpas hold the world record for most Everest ascents—Apa Sherpa and Phurba Tashi Sherpa both summited the peak 21 times. They also hold the majority of speed summiting records. Pemba Dorje climbed from Everest's South Base Camp to summit with supplemental oxygen in eight hours and ten minutes, while Kazi Sherpa completed the feat without supplemental oxygen in 20 hours and 24 minutes.
The new findings are important as a first step in developing treatments for intensive care unit patients suffering from hypoxia, or a lack of oxygen, Murray says. Hypoxia occurs in healthy people at high altitude, and also in critical care patients, where it's life threatening. Currently, doctors add oxygen to these patient's blood. But that thickens the blood and can cause complications like clogged blood vessels.
Murray's research is in its infancy, but the ultimate goal is to develop a method—a pill, perhaps—that allows patients to become more Sherpa-like, and use what little oxygen they have more efficiently, thereby leading to better health outcomes.
Ultimately, if you want the genetically-gifted oxygen-sipping qualities of a Sherpa, you'll have to be reborn as one. "They've adapted and evolved over thousands of years," Murray says. But Westerners can still get some of the unique fitness benefits of Sherpas, whose jobs entail carrying gear uphill among the camps of Everest. Carrying weight for distance is a fundamental physical skill, one that Westerners rarely practice today, according to Doug Kechijian, a doctor of physical therapy and owner of Resilient Performance PT in New York City.
Walking while loaded down with a weight equal to anywhere from 15 to 50 percent of your bodyweight—whether it's a in a backpack, held at your sides, or worn in the form of a weight vest—gives you a new fitness stimulus, Kechijian says. This kind of training may also improve your endurance, according to a study conducted by the Mountain Tactical Institute. And performing loaded carries may fill gaps in your strength, and increase your lifting performance across the board, according to a study in the Journal of Strength and Conditioning Research.
"If you're planning on mountaineering, this training is essential," Kechijian says. But even if you're just trying to burn off the cheeseburger you ate for lunch, walking while loaded down burns about three times the calories compared to plain old walking, research shows. And that's without any of the lung and leg burning anguish of running.
Training like a Sherpa is also beneficial for injury-prone runners: "Running is a skill, and many people do it wrong," says Kechijian. It's also impactful. Run too often with questionable mechanics and you get injured. Walking doesn't take much skill. Doing it while weighed down improves your endurance, but with less of the impacts of running. Translation: Less risk of injury.
If you want to try it, Kechijian has many of his clients toss on a weighted vest, crank a treadmill's incline to its max, then walk for twenty minutes to a half hour. Conversely, you could just toss some weight in a backpack—start with 20 to 30 pounds—and go for a walk.
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