(a–p) m.s.e. variation maps represent the distribution and magnitude of the combined mean m.s.e. in each pixel across the plantar surface of the foot at each speed trial in all subjects. Intra-subject spatial variability measured by the mean m.s.e. is highest and confined almost exclusively to the lateral and medial forefoot in all subjects; however, there is no consistent increasing or decreasing relationship between mean m.s.e. and speed.