Tons of Cargo
During their field research, Heglund and his teammates flagged down porters and weighed the loads of study volunteers on the approach to Namche one day. More than 500 men and about 100 women carried about 30 tons of material to the market that day, the researchers estimated.
On average, the men and women respectively bore 93 percent and 66 percent of their body weight, the researchers report.
"It's quite impressive to see those guys walking with such heavy loads," said Heglund's teammate Bénédicte Schepens. She added that the feat is particularly impressive because "they're [generally] not very well equipped [and] have very bad shoes."
A porter's gear is simple but effective: The load goes into an oversized basket, or doko, which rests against the back. A strap runs underneath the doko and over the crown of the head, which bears most of the weight. Each porter also carries a T-shaped walking stick called a tokma.
When on the move, porters sometimes pause more than they walk. "On a steep incline," Heglund said, "they'll walk for as little as 15 seconds and rest for 45." At each stop, they use their tokma to support their load, which allows a standing rest.
A Good Puzzle
Around the world, many people use their heads to bear burdens, said Rodger Kram, an expert on human and animal locomotion at the University of Colorado in Boulder. "It's amazing how universal carrying loads on the head isexcept in Western Europe and North America," he said.
But their "enormous loads" set the Nepalese apart, Kram added. "It's a good scientific puzzle, how they [conserve] energy when walking."
The researchers behind the new study haven't fully pieced it together.
African women use a particular gait to conserve up to 80 percent of each stride's momentum, Heglund has found. But it only works on flat ground, and there's little of that in Nepal.
Heglund said the porters' "energy transfer is about 65 percent, the same as you or I." That may be. But they certainly don't struggle beneath their burdens as the rest of us might.
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