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Sherpa Performance on Top of the World

May 12, 2008 8:00 AM

Nearly one year ago, Scott McIntosh, M.D., M.P.H., spent a few minutes on top of the world—literally. McIntosh, assistant professor of emergency medicine, summited Mount Everest last May while conducting physiological research with the SuperSherpa Expedition.

“Our role was to look at the Sherpas’ physiology and why they are so good at what they do at high altitudes,” he said. Sherpas are native to the Himalayan Mountain region of Nepal and are legendary for their strength and stamina on the 29,035-foot ascent up Everest, the world’s highest peak.

Stacie Wing-Gaia, Ph.D., R.D., principal investigator and assistant professor of nutrition, said the study results of this first all Sherpa expedition provide a starting point for more study. Next month, she plans to submit a case study for publication in an altitude-related journal.

The researchers suspected that the Sherpa’s aptitude had something to do with their history of habitating the Himalaya region for 25,000 years, genetically predisposing them to better performance at higher altitudes.

“If we took anyone from here and put them on the summit of Everest, they would be unconscious in about two minutes and dead in five minutes,” explained McIntosh. Everest contains about one-third of the oxygen at sea level. Attempting to summit the mountain requires three weeks’ acclimation for most climbers. Sherpas need only 10 days.

Prior to the expedition’s departure, the chief subjects of the study, Apa Sherpa and Lhakpa Sherpa, two of the world’s most accomplished Everest mountaineers who now live in Utah, underwent tests for strength, physical fitness, body composition, respiratory and heart rates. The results weren’t particularly impressive, according to McIntosh. But as soon as the team reached Base Camp (elevation 17,800 feet), the Sherpas began to stand out.

McIntosh and co-investigator Staci Nix, R.D., instructor of nutrition in the U’s College of Health who was stationed at Base Camp, monitored the Sherpas to measure their total energy expenditure, weight, hydration, body composition, oxygen saturation, and heart and respiratory rates. McIntosh was monitored for comparison purposes.

Early in the climb, the Sherpas’ oxygen saturation levels measured in the mid- to high-70s while McIntosh was in the low 60s. An Emergency Department patient who arrived with a saturation level below 90 would be put on oxygen and rushed to the Surgical Intensive Care Unit, according to McIntosh.

They also found the Sherpas used 3,600 kilocalories a day. By comparison, a Tour de France rider expends around 7,000 to 8,000 kilocalories during a day in the saddle, McIntosh said. “To me, this means the Sherpas are very efficient at what they do.”

Because of intestinal illness, loss of appetite, dehydration or other problems, the average Everest climber loses 20 percent of body weight. But none of the Sherpas lost weight and, in fact, one guide gained weight. This could be related to their resting metabolic rate, which is believed to play a role in altitude-induced weight loss. Most Everest climbers’ resting metabolic rate increases 7 percent to 28 percent, but the Sherpas’ resting metabolic rate did not rise.

The Sherpas did show significant dehydration. Yet they didn’t exhibit the usual symptoms—headaches and nausea. Because of language barriers and cultural differences, the team was unable to measure the Sherpas’ appetite and dietary intake, and Wing-Gaia would like to someday quantify that information. “There is still so much to learn about the Sherpas high-altitude performance that could open the path to helping lowlanders better adjust to high altitude and treat acute mountain illnesses.”

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