Steven E. Robbins, Gerard J. Gouw, Jacqueline McClaran, and Edward Waked. “Protective Sensation of the Plantar Aspect of the Foot,” Foot & Ankle, 14(6), 1993, pp. 347-352.
Excerpts:
Compared with the hairy skin of the thigh, plantar skin required approximately 600% greater abrading loads to reach pain threshold. …
We conclude that plantar skin is well protected through sensory feedback from abrasive injuries when barefoot. This information combined with previous reports suggests that risk of injury when normally shod individuals perform barefoot locomotion should be low. …
The results of studies examining barefoot activity have consistently shown that the unshod human foot is characterized by excellent mobility, primarily in the region of the forefoot, thickening of the plantar skin up to 1 cm, better alignment of the phalanges with the metatarsals causing the digits to spread, an absence of foot deformities, and mobility of the arches on loading. …
Furthermore, optimum foot development occurs in the barefoot environment, and, therefore, children should be encouraged to partake in barefoot activity. …
Another aspect of barefoot safety is risk of puncture wounds. A report has shown that when the plantar surface is subjected to localized load via sharp deforming objects, it deforms so as to contain the object in the void created by the deforming object, thus resisting perforation. Whereas the risk of plantar surface puncture wounds must be greater when barefoot if compared with wearing shoes, this skin defense makes the sole of the foot reasonably resistant to penetration. …
Observations from countries where barefoot activity is the norm indicates that plantar skin eventually becomes robust and permits extremely long duration of barefoot locomotion at high average velocities, without signs of damage to plantar skin, or for that matter other lower extremity injuries. …
In conclusion, this experiment continues to enlarge the body of knowledge suggesting how well the human foot is adapted for safe locomotion, unencumbered by footwear…