Liew Bernard X W, Morris Susan, Masters Ashleigh, Netto Kevin
School of Physiotherapy and Exercise Sciences, Curtin University, GPO Box U1987, Perth, WA 6845, Australia.
School of Physiotherapy and Exercise Sciences, Curtin University, GPO Box U1987, Perth, WA 6845, Australia.
J Biomech. 2017 Nov 7;64:253-257. doi: 10.1016/j.jbiomech.2017.09.028. Epub 2017 Oct 6.
Direct kinematic-kinetic modelling currently represents the "Gold-standard" in leg stiffness quantification during three-dimensional (3D) motion capture experiments. However, the medial-lateral components of ground reaction force and leg length have been neglected in current leg stiffness formulations. It is unknown if accounting for all 3D would alter healthy biologic estimates of leg stiffness, compared to present direct modelling methods. This study compared running leg stiffness derived from a new method (multiplanar method) which includes all three Cartesian axes, against current methods which either only include the vertical axis (line method) or only the plane of progression (uniplanar method). Twenty healthy female runners performed shod overground running at 5.0 m/s. Three-dimensional motion capture and synchronised in-ground force plates were used to track the change in length of the leg vector (hip joint centre to centre of pressure) and resultant projected ground reaction force. Leg stiffness was expressed as dimensionless units, as a percentage of an individual's bodyweight divided by standing leg length (BW/LL). Leg stiffness using the line method was larger than the uniplanar method by 15.6%BW/LL (P < .001), and multiplanar method by 24.2%BW/LL (P < .001). Leg stiffness from the uniplanar method was larger than the multiplanar method by 8.5%BW/LL (6.5 kN/m) (P < .001). The inclusion of medial-lateral components significantly increased leg deformation magnitude, accounting for the reduction in leg stiffness estimate with the multiplanar method. Given that limb movements typically occur in 3D, the new multiplanar method provides the most complete accounting of all force and length components in leg stiffness calculation.
在三维（3D）运动捕捉实验中，直接运动学-动力学建模目前代表了腿部刚度量化的“金标准”。然而，目前的腿部刚度公式中忽略了地面反作用力和腿长的内侧-外侧分量。与目前的直接建模方法相比，考虑所有三维因素是否会改变腿部刚度的健康生物学估计尚不清楚。本研究将一种新方法（多平面方法）得出的跑步腿部刚度与目前的方法进行了比较，新方法包括所有三个笛卡尔坐标轴，而目前的方法要么只包括垂直轴（直线法），要么只包括前进平面（单平面法）。20名健康的女性跑步者以5.0米/秒的速度穿着鞋子在地面上跑步。使用三维运动捕捉和同步地面测力板来跟踪腿向量（髋关节中心到压力中心）长度的变化以及合成的地面反作用力。腿部刚度以无量纲单位表示，为个体体重除以站立腿长（BW/LL）的百分比。使用直线法得出的腿部刚度比单平面法大15.6%BW/LL（P <.001），比多平面法大24.2%BW/LL（P <.001）。单平面法得出的腿部刚度比多平面法大8.5%BW/LL（6.5 kN/m）（P <.001）。内侧-外侧分量的纳入显著增加了腿部变形量，这解释了多平面法中腿部刚度估计值的降低。鉴于肢体运动通常发生在三维空间中，新的多平面方法在腿部刚度计算中对所有力和长度分量提供了最完整的考虑。
