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.

Excerpts:

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. …

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. …

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.