Accessible Summary:

Purpose:  To test the hypothesis that foot morphology changes observed as normally shod subjects adapt to barefoot activity is explained as a response to plantar tactile stimulation.

Synopsis: The plantar was uniformly deformed by an penetrometer with spherical deforming ends of different sizes at three locations on the plantar surface: heel, metatarsal-phalangeal joints and distal digits. Pain threshold was recorded.  Pain threshold to small deforming objects was lowest at the metatarsal-phalangeal joints and highest at the heel with the distal digits being intermediate. Difference in pain threshold across the plantar surface to contact with small rigid objects when barefoot can explain raising of the medial arch through intense plantar flexion of the digits, thereby sparing the area with the lowest pain threshold.

Significance: This report indicates that detailed foot mechanics when barefoot is a response to tactile information.  It further supports the hypothesis that mechanics of locomotion when barefoot is largely mediated through tactile sensory input.