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.

The scientific literature suggests that barefoot activity may be beneficial. There is a current trend in recreational barefoot activity in children and adults, and barefoot running among athletes. Although the type of skin over most of the body (hairy skin) seems to be easily injured by painful abrading loads, little is known about protection provided by plantar sensory feedback against damage from excessive wear during barefoot locomotion. To evaluate this, we administered a volley of 35 painful abrading loads to glabrous and hairy skin sites over a 5-min period, and examined its effects for signs of cutaneous injury in a sampale of 12 normally shod healthy male subjects. Compared with hairy skin of the thigh, plantar skin required approximately 600% greater abrading loads to reach pain threshold. Furthermore, painful stimulation produced visible redness and hypersensitivity in all subjects at the hairy skin site 24 hr after stimulation, whereas only 8% reported hypersensitivity and none showed erythema at the plantar area 1 day later. We found that planter skin possesses a higher pain threshold to abrading stimuli than hairy skin. In face, loading of the plantar area was limited to innocuous levels due to intolerable pain. 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.

Excerpts

Compared with the hairy skin of the thigh, plantar skin required approximately 600% greater abrading loads to reach pain threshold.

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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.

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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.

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Furthermore, optimum foot development occurs in the barefoot environment, and, therefore, children should be encouraged to partake in barefoot activity.

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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.

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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.

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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 . . .