Some authors have concluded that chronic overloading with locomotion is inevitable in modern man because of inherent lower extremity fragility. Accordingly, footwear, such as running shoes, which attempt to attenuate shock waves through interposition of yielding layers between the plantar surface and ground, are presumed essential for safe running, and are also promoted for use during walking. However, this supposition seems inconsistent with reports indicating that habitually unshod humans are not subject to chronic overloading during running. By taking this into account, the lower extremity must be inherently durable, and chronic overloading must be a consequence of wearing footwear, and probably due to increased shock with their use.

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It has been observed that locomotion in barefoot-adapted subjects (normally unshod, or customarily shod after allowing several weeks of barefoot adaptation) differs from customarily shod subjects in that those barefoot adapted 'grasp' with their digits when they walk...

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Obviously, the ideal solution to the running related injury problem in shod populations lies in barefoot locomotion, since protective adaptations seems to be optimized for this state. Normally shod people would have to allow sufficient time for adaptation of the plantar skin and intrinsic foot musculature (perhaps 6 weeks), and run barefoot frequently, perhaps daily, to sustain this adaptation. However, once adapted, the foot is extremely durable.

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The lower extremity is inherently durable, and, when unencumbered by footwear, it can endure running without signs of chronic overloading, because a vigilant system restrains shock. The use of modern athletic footwear, in addition to being inferior to older footwear in moderating shock during running, renders the lower extremity susceptible to injury because of design flaws introduced by the preoccupation with optimization of plantar comfort.

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The obvious solution to the problem of chronic overloading in shod runners is to promote barefoot running.