Bazaar skills Heglund and his colleagues travelled to Nepal and watched porters carrying their loads up to a weekly market at the town of Namche. They asked a selection of these porters to walk around a flat track at various speeds while carrying several different loads. The energy expended by these individuals was determined by measuring their oxygen consumption and carbon dioxide production through a mask. The team then compared the results with work on women of the African Kikuyu and Luo tribes. These women can carry head loads of up to 20% of their body weight without expending extra energy. Additionally, they carry loads of up to 60% of their body weight at a considerably cheaper metabolic cost than army recruits carrying equivalent backpack loads. At light loads, the Nepalese porters and the African women were about equally efficient. But the heavier the load, the better the Nepalese became at expending minimal energy. Heglund and colleagues have previously shown that the African women conserve energy by swinging their bodies like a pendulum3. But the Nepalese porters had a different gait. "They didn't use the same energy saving mechanism as the African women," says Heglund. The team plans to study this next.