Data from: The nature of functional variability in plantar pressure during a range of controlled walking speeds

During walking, variability in step parameters allows the body to adapt to changes in substrate or unexpected perturbations that may occur as the feet interface with the environment. Despite a rich literature describing biomechanical variability in step-parameters, there are as yet no studies that consider variability at the body – environment interface. Here, we used pedobarographic statistical parametric mapping and two standard measures of variability, mean square error and the co-efficient of variation, to assess the magnitude and spatial variability in plantar pressure across a range of controlled walking speeds. Results by reduced major axis, and pSPM regression, revealed no consistent linear relationship between mean square error and speed or mean square error and Froude number. A positive linear relationship however was found between co-efficient of variation and walking speed and co-efficient of variation and Froude number. The spatial distribution of variability was highly disparate when assessed by mean square error and co-efficient of variation: relatively high variability was consistently confined to the medial and lateral forefoot when measured by mean square error, while the forefoot and heel show high variability when measured by co-efficient of variation. In absolute terms, variability by co-efficient of variation was universally low (<2.5%). From these results we determined that variability as assessed by mean square error are independent of speed, but dependent on speed when assessed by co-efficient of variation.