"That's one small step for [a] man, one giant leap for mankind."
These are, of course, the famous words of "moonwalker" Neil Armstrong (20/07/69). That is nearly half a century ago, and gosh it only seems yesterday. Most certainly, it could be argued, the footwear industry and more particularly the division of synthetic materials benefited from the billions of dollars spent on the space program. What an irony, the ultimate human quest to reach the stars, resulted in people walking, running and jumping on this Earth. As witnessed in professional sports, no competitor would be without the aerospace influence in their footgear.
Thermoplastic materials (memory foam) change shape when heated and put under pressure, then retain the new shape when the high temperature is reduced. Friction between the foot and the inside of the shoes causes increase in local temperatures to over 140 degree centigrade which may result in tender spots, blisters and callous. Expanded polyethylene provides excellent isotatic properties that act like a waterbed. High pressure points are reduced, local temperatures lessened and damage to the tissues minimised. These plastics are by-products of oil refining and provide a very cheap and valuable resource. Nowadays most athletic trainers and sports shoes incorporate memory foam inlays as standard fit.
Foot Orthoses, are made from hard plastic and look like arch supports.
When body weight is applied as the person stands and walks over curved plastic the peak torque is equivalent of a medium sized elephant pirouetting. Yet the plastic does not deform. Semi-rigid plastics, common in the manufacture of most foot orthoses originate from the space industry and now provide the means the basis for allopathic management of the leg and foot.
An other innovative material incorporated into sport shoes is viscoelastic. These are truly out of this world materials and are both liquid and gas. By intellegent manipulation of the polymer structures, viscoelastics appear as soft solids. You may have already witnessed them but been unaware of their origins. If you have ever been terrified by those horrible sticky stretchy spider like toys children throw at the wall and they stick, only to peel off without leaving a mark. To the touch these feel like wet jelly and no matter how dirty they become a simple wash under the tap freshens them up. Viscoelastic is regularly trapped within the sole structure of running shoes. Positioned to reduce peak shock during stance phase the material is hard wearing, has superb elastic memory and is extremely light in weight. For example, the shock generated at normal heel strike would equate to the G-Force applied to the head in a car crash resulting in a whiplash injury.