The Mysterious Strengths of a Sherpa
RENEE MONTAGNE, host:
A typical Sherpa roams the Himalayas carrying a load that weighs more than he does. Scientists wanted to know how this was humanly possible, so they set up a laboratory along one of the busiest Sherpa routes in Nepal. NPR's Jon Hamilton reports on what they learned.
JON HAMILTON reporting:
The lab was run by Belgian scientists. They picked a spot along a 60-mile footpath that zigs and zags from the Kathmandu Valley to Namche, a town near Mt. Everest. The path is steep and just wide enough for two yaks to pass. Pretty much everything in Namche has been carried up this route by Sherpas and other Nepalese porters. Norman Heglund says the porters carry anything they can sell.
Mr. NORMAN HEGLUND (Catholic University of Louvain): They'd have, say, a 50-kilo sack of rice and two or three cases of Coca-Cola. They'd sell the rice to the locals and try and peddle the Coke to the tourists.
HAMILTON: Heglund is a physiologist at the Catholic University of Louvain in Belgium. He wanted to know how much energy the porters expended carrying their loads. That meant asking porters to put on a mask that measured their oxygen use as they carried specific loads. Heglund says it was pretty easy to find subjects for his experiment.
Mr. HEGLUND: I would get up early just at dawn, and the porters would already be going by. They start before dawn in the morning, and they continue carrying their loads all day long, and they continue until after dusk in the evening.
HAMILTON: On one day, the scientists counted more than 500 male porters, about 100 female porters and 32 yaks. The youngest porter was 11, the oldest 68. And the experiment was pretty interesting, too. It showed that when a porter carried a load, his or her metabolism increased, but only about half as much as a European's would. So a Sherpa can carry more weight using less energy. Heglund says the porters seem to have physically adapted to carrying very heavy loads very slowly. He says he realized just how slowly while watching a group carrying cow skins.
Mr. HEGLUND: They were coming out of this gorge, it was a very steep incline, and they were working as a team, and they would all start up together, and they would only climb uphill for 15 seconds, and that's not that many steps, and then they would all rest together, and they would rest for about 45 seconds.
HAMILTON: Resting is easy because porters carry a special hiking stick that they can place under their load at any time. Some scientists have wondered whether the porters are more efficient because they use their heads to carry most of the load. A strap around the forehead supports a wicker basket on their back. Tim Griffin is a research fellow at Duke University. He studies the biomechanics of walking and running.
Mr. TIM GRIFFIN (Duke University): So one of the things that's always intrigued scientists about the head load carrying is that it's raising the center of mass to a higher position in the body. And could that, in some way, be somehow facilitating more effective walking mechanics that we don't really understand quite yet?
HAMILTON: An earlier study of African women who carry heavy loads on their heads found that the method did make them more efficient walkers, but the Nepalese porters seemed to have some other advantage. Griffin says maybe they have developed muscles that simply worked more efficiently, but how? Griffin says tortoises may provide a clue. Research shows these turtles have extremely efficient muscles, and, like the porters, they move very slowly.
Mr. GRIFFIN: Perhaps the speed at which they walk may have something to do with it in terms of not just a short-term feature, but maybe a kind of long-term adaptation. Maybe there's something that if you walk slowly with heavy loads, that may be able to alter the muscle fibers in some way.
HAMILTON: It's still not clear how. But Griffin thinks that once scientists understand what's going on with tortoise muscles, they'll be one step closer to solving the Sherpa mystery. The research was published in this week's issue of the journal Science. Jon Hamilton, NPR News.
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