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Sensitivity Mapping of the Human Foot: Thresholds at 30 Skin Locations

Background: Mechanoreceptors in the skin provide sensory input for the central nervous system about foot placement and loading. This information is used by the brain to actively control or regain balance and is important to establish memory traces for subsequent movement. A sensitivity map of the human foot could help to understand the mechanisms of the foot as a sensory organ for movement adjustment and balance control. Materials and Methods: Touch and vibration perception threshold values from 30 plantar and dorsal foot locations were determined in more than 40 women and men between 20 and 35 years. Semmes Weinstein monofilaments and a vibrotactile neurothesiometer were used for skin sensitivity threshold detection. Results: Large sensitivity differences were present between the 30 different foot sites. Gender effects were not present for touch but women had better sensitivities for vibration (p < 0.01), especially on the dorsal aspect of the foot. Age, in our cohort of 20- to 35-year-olds, did not have an influence on vibration or touch sensitivity. The heel had the highest detection thresholds for touch but was very sensitive for vibration stimuli. Compared to the dorsum, the plantar foot was substantially more sensitive, especially for vibration detection. Conclusion: The results suggest that primarily the fast adapting plantar mechanoreceptors are important in assisting balance control during human locomotion. Clinical Relevance: The sensitivity map of the foot will help in understanding the function of the foot as a sensory organ and could be useful in creating footwear for better balance control and for the design of comfortable shoes.