Anyone ever come to the countries of the East, or Africa, hit the ease with which the locals are on the head pretty hefty loads. Women Kenyan Luo tribe, for example, are able to carry a load equal to almost 70% of their body weight. Research physiologists argue that the transport of loads on the head - the most economical to the human body. A proof of this is the laws of physics, in fact, moving the load at a constant speed on a horizontal surface, a man virtually no work except expended on overcoming the forces of friction.
And so it is done, it is necessary either to drive the load with acceleration, or to raise it. The latter option is the case when walking, when the body of man is raised and lowered. So the main forces spent to lift the body and the load at each step. Wherein the head is raised and lowered with a vertical amplitude less than the whole body. And this feature is elaborated in an evolutionary way: the brain protects against shocks, springs served as a spring with a double bend the spine. Although, of course, a great role in carrying goods on her head plays a workout that produces besides a beautiful and smooth gait. Although people are not familiar with this method, the transfer of goods, such experiments to better myself not to.