What started as the study of animal motion in Kenya in the 80s by a bioengineer, developed into another study. Sparked by an interest in having observed the loads being carried by Kenyan women on their heads, Norm Heglund wanted to find out how the Kenyan women maintained a load and kept it balanced on their heads. Through experimentation, research, altering weight load and finding comparisons of other human-carrying capabilities, he was better able to understand the amount of energy spent when the body is in different states of motion and carrying changeable weight.
Heglund, had the women walk on a treadmill with loads on their heads and increased the weight to see how much they could carry. He measured the levels of oxygen and the metabolic rate. The outcome was surprising because he found that the women could carry up to 60-80 percent of their body weight, with some increase in their metabolic rate. To better understand this he tried another experiment.
Wanting to see what the effects would be on himself, he carried 15 percent of his body weight by adding weights to a bicycle helmet. He found that the only way that it was bearable was if his head maintained a vertical angle otherwise any misalignment would cause a serious injury. His findings led him to believe that the reason the Kenyan women could carry heavy loads and the way they walked was like the motion of a pendulum.
He recognized that the combination of motion, weight distribution, balance, and energy use was being efficiently used by the women. Their bodies seemed to be capable of aligning and adjusting to varying loads by using their bone structure rather than their muscles. When walking or running the body normally relies on muscles and tendons. Further study was done and a comparison was chosen against his findings.
A scientific study existed that was made in the 80s on the backpacks that new army recruits carried. Heglund wanted to compare the data against the Kenyan women. Having looked at the data Heglund found that when walking slowly the recruits used less energy than the Kenyan women but when they were going a faster speed and carrying a heavier load (over half of their body weight) the Kenyan women had an advantage that was close to two-folds. His conclusion was that the Kenyan women's efficient use of energy and their ability to carry heavy loads was in the way that they walked; like the movements of a pendulum. Studying the motion and balancing abilities of the human body is an ongoing process.
The pendulum has somewhat shifted and become more sophisticated, new developments of exoskeleton robotics can now be used to study the human body’s movements and effects of weight distribution and balance.
This is based on an article by Adam Piore for Nautilus