Steven E. Robbins, Gerard J. Gouw, and Adel M. Hanna. "Running-related injury prevention through innate impact-moderating behavior," Medicine and Science in Sports and Exercise, 21(2), 1987, pp. 130-139.

The purpose of these experiments was to test the Robbins and Hanna hypothesis, which relates differences in discomfort from localized deformation at certain positions on the planter surface to protective behavior (instrinsic foot shock absorbtion). A penetrometer was used to quantify the relations between localized load and pain and between load and depth of deformation. The magnitude of load required to elicit pain varied significantly (P<0.005) in relation to position on the plantar surface. With a load of 9 kg and a 10mm sperical end on the penetrometer, 6% of the sample reported pain at the heelpad. 32% at the distal first digit, and 66% at the first metatarsal-phalangeal joint. This pattern was predicted by the Robbins and Hanna thesis. Two deformation patterns were observed which were best explained by deformation constraint by tight trabecular tehtering of the epithelial membrane at the heelpad and distal first digit and unrestricted deformation due to loose trabecular tethering of the epithelial membrane at the first metatarsal-phalangeal joint. These data provide insight into how, when barefoot, the plantar surface resists perforation yet provides protection to local bony structures. These data further support the notion that plantar sensory feedback plays a central role in safe and effective locomotion.

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These data provide insight into how, when barefoot, the plantar surface resists perforation yet provides protection to local bony structures. These data further support the notion that plantar sensory feedback plays a central role in safe and effective locomotion.

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A relation has been reported between barefoot activity and raising of the main longitudinal arch, presumably by increased intrinsic foot muscle tone. The subjects with the greatest reduction in arch span performed barefoot activity outdoors. This suggests that surface irregularities causing local deformations on the plantar surface contributed to intrinsic foot muscular activation.

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When compared to locomotion with existing footwear, these mechanics of the bare foot may offer improved balance during locomotion. This is compatible with the preference of many gymnasts and dancers for being barefoot to wearing footwear.