Foot shape and plantar pressure relationships in shod and barefoot populations.

This study presents population-based multivariate regression models for predicting foot plantar pressure from easily measured foot metrics in both shod and barefoot populations for running and walking tasks. Both shod and barefoot models were trained on 50 participants and predicted plantar pressure from anthropometric measurements using a 'leave-one-out' validation with R2 values of 0.72-0.78 across walking and running in both populations. When the model was blindly tested on 16 new data sets, the model performed just as well with R2 values of 0.76-0.79 across both populations. Walking and running peak plantar pressure were predicted with similar levels of accuracy in both populations. It was revealed that forefoot plantar pressure was more sensitive to the hallux-toe distance in barefoot people with shod participants showing little response to this foot characteristic. Lateral forefoot plantar pressure was sensitive to the arch index in both shod and barefoot participants but only for walking. During running, the arch index was not a useful determinant of lateral forefoot pressure. Hence, habitually barefoot people who adopt minimalist footwear should consider additional support in the medial forefoot and walking footwear should include forefoot support stratified by arch index (foot type), but running footwear is challenging due to the variability in strike patterns.