We have seen that, to produce upright support, muscles pull on bones, but bones also pull on muscles, creating what is sometimes described as a tensegrity structure. Tensegrity structures are often compared to more traditional architectural designs such as columns, arches and walls, which are designed to resist compression and to bear weight. Whether made of bricks, girders, blocks of stone, dried dirt, or concrete, they have been used for centuries in the construction of cathedrals, coliseums, temples, aqueducts, and houses of all kinds. Even an arch is a compression structure that distributes downward pressure laterally to its base on either side.
A tensegrity structure, in contrast, combines compression members and tensile members to produce a strong, lightweight structure. The word “tensegrity” is a combination of “tensional” and “integrity”--a term coined by Buckminster Fuller, who also invented and utilized the concept. In tensegrity structures, the rigid members don’t bear weight but provide opposition to the tension members, which in turn pull on the compression members.
A fascinating study of tensegrity in action was carried out in 1995. It compared European men carrying heavy loads on their backs to Kenyan women carrying weight on their heads. The women, it turns out, carried 20% of their body weight with no additional expenditure of calories as compared to the men, who used far more effort. (study linked here) The study concluded that this was because the women altered their gait but did not alter their upright support mechanism when carrying a load on their heads, whereas the European men did and therefore had to use far more muscular effort to support their packs. In essence, each woman was able to carry the weight on top of her head and vertical spine without disturbing the tensegrity design of the musculoskeletal system, so that the load was distributed over the entire tensegrity structure rather than straining particular muscles.