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 (pSPM) and two standard measures of variability, mean square error (m.s.e.) and the coefficient of variation (CV), 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 m.s.e. and speed or m.s.e. and Froude number. A positive linear relationship, however, was found between CV and walking speed and CV and Froude number. The spatial distribution of variability was highly disparate when assessed by m.s.e. and CV: relatively high variability was consistently confined to the medial and lateral forefoot when measured by m.s.e., while the forefoot and heel show high variability when measured by CV. In absolute terms, variability by CV was universally low (less than 2.5%). From these results, we determined that variability as assessed by m.s.e. is independent of speed, but dependent on speed when assessed by CV.

行走过程中，步参数变异可使人体适应底物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步参数的生物力学变异，但目前尚无研究关注体-环境界面处的变异情况。本研究采用足底压力统计参数映射（pedobarographic statistical parametric mapping, pSPM）以及两种经典变异度指标——均方误差（mean square error, m.s.e.）与变异系数（coefficient of variation, CV），评估了不同受控步行速度下足底压力的幅值与空间变异特征。通过约化主轴法与pSPM回归分析发现，m.s.e.与步行速度、m.s.e.与弗劳德数（Froude number）之间均不存在稳定的线性相关关系。然而，CV与步行速度、CV与弗劳德数之间则呈现显著正线性相关。采用m.s.e.与CV所得到的变异度空间分布差异显著：以m.s.e.衡量时，较高的变异度始终集中于内、外侧前足区域；而以CV衡量时，前足与足跟区域则表现出较高变异度。从绝对数值来看，CV所表征的变异度普遍较低（低于2.5%）。基于上述结果，我们得出结论：以m.s.e.评估的变异度与步行速度无关，而以CV评估的变异度则依赖于步行速度。