A heavily loaded Nepalese porter on the route between the Kathmandu valley and Namche Bazaar in the Mt. Everest valley. The head strap (namlo), load basket (doko) and T-stick (tokma) for supporting the load during frequent rest periods are shown. The Nepalese porters can carry loads of 20% of their body weight for 'free', that is, for no increase in their metabolic rate over their unloaded rate at the same walking speed. Credit: Science.