Nepalese porters carry seemingly crushing loads with what appears to be little difficulty. Their approach, which uses a head strap known as a namlo to support a basket, contributes to their being the most energy efficient human transporters in the world, a new report indicates.

Guillaume J. Bastien and his colleagues at the Université Catholique de Louvain in Belgium studied porters traveling to a weekly bazaar in the town of Namche near Mount Everest. The town is located at an elevation of 3,500 meters and the journey to get there from the Kathmandu valley, which includes ascents reaching up to 8,000 meters, takes between seven to nine days. The researchers weighed randomly selected porters and their loads as they approached the village. On average, male porters carried around 90 percent of their body mass and females lugged loads weighing around 66 percent of their body mass. One ambitious male porter was transporting goods that weighed nearly twice as much as he did.

The researchers then asked eight of the male porters to carry various loads around a track at different speeds while their oxygen consumption was measured. The team reports that the Nepalese men exhibited more economical energy use for all loads than control subjects did. (For comparison, the team collected data from a group of Europeans using standard backpacks.) Indeed, cargo that weighed less than 20 percent of a porter's body weight had such little impact on his energy use that it was essentially carried without cost. Previous studies of unique carrying methods had examined African women who balance huge loads on their heads. They were thought to be the peak of efficiency, carrying loads approaching 60 percent of their body weight and outperforming army recruits who used backpacks. But for all but the lightest loads, the Nepalese porters performed better, suggesting they now carry the title of the world's best haulers. The results appear in the current issue of the journal Science.

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