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.步行过程中，步态参数的变异性可使人体适应地面基质变化或足部与环境接触时可能出现的意外扰动。尽管已有大量文献阐述了步态参数的生物力学变异性，但目前尚无研究关注身体-环境交互界面处的变异性。本研究采用足底压力统计参数映射（pedobarographic statistical parametric mapping），以及均方误差（mean square error）和变异系数（coefficient of variation）两种经典变异性度量方法，评估了不同受控步行速度下足底压力的幅值与空间分布变异性。通过约简主轴回归（reduced major axis）与pSPM回归分析的结果显示，均方误差与步行速度、均方误差与弗劳德数（Froude number）之间均未存在一致的线性关系。但研究发现，变异系数与步行速度、变异系数与弗劳德数之间存在正线性相关。通过均方误差与变异系数评估得到的变异性空间分布差异极大：采用均方误差度量时，较高的变异性始终集中于前足内侧与外侧区域；而采用变异系数度量时，前足与足跟区域则表现出较高的变异性。从绝对数值来看，基于变异系数计算得到的变异性普遍较低（<2.5%）。基于上述结果，我们得出结论：以均方误差衡量的变异性与步行速度无关，而以变异系数衡量的变异性则随步行速度变化。