Laboratory of Biomechanics and Physiology of Locomotion, Institute of NeuroScience, Université Catholique de Louvain , Louvain-la-Neuve , Belgium.
Laboratory of Neuromotor Physiology, Institute for Research and Health Care, Santa Lucia Foundation , Rome , Italy.
J Appl Physiol (1985). 2018 Aug 1;125(2):642-653. doi: 10.1152/japplphysiol.01020.2017. Epub 2018 Apr 26.
During walking, the elevation angles of the thigh, shank, and foot (i.e., the angle between the segment and the vertical) covary along a characteristic loop constrained on a plane. Here, we investigate how the shape of the loop and the orientation of the plane, which reflect the intersegmental coordination, change with the slope of the terrain and the speed of progression. Ten subjects walked on an inclined treadmill at different slopes (between -9° and +9°) and speeds (from 0.56 to 2.22 m/s). A principal component analysis was performed on the covariance matrix of the thigh, shank, and foot elevation angles. At each slope and speed, the variance accounted for by the two principal components was >99%, indicating that the planar covariation is maintained. The two principal components can be associated to the limb orientation (PC1*) and the limb length (PC2*). At low walking speeds, changes in the intersegmental coordination across slopes are characterized mainly by a change in the orientation of the covariation plane and in PC2* and to a lesser extent, by a change in PC1*. As speed increases, changes in the intersegmental coordination across slopes are more related to a change in PC1 , with limited changes in the orientation of the plane and in PC 2. Our results show that the kinematic patterns highly depend on both slope and speed. NEW & NOTEWORTHY In this paper, changes in the lower-limb intersegmental coordination during walking with slope and speed are linked to changes in the trajectory of the body center of mass. Modifications in the kinematic pattern with slope depend on speed: at slow speeds, the net vertical displacement of the body during each step is related to changes in limb length and orientation. When speed increases, the vertical displacement is mostly related to a change in limb orientation.
在行走过程中，大腿、小腿和脚的抬高角度（即，肢体与垂直方向之间的角度）沿着一个受约束在一个平面上的特征环协同变化。在这里，我们研究了环路的形状和平面的方向如何随着地形坡度和行进速度的变化而变化，这反映了节段间的协调。十位受试者在不同坡度（-9°至+9°）和速度（0.56 至 2.22 m/s）的倾斜跑步机上行走。对大腿、小腿和脚抬高角度的协方差矩阵进行主成分分析。在每个坡度和速度下，两个主成分解释的方差>99%，表明平面协同变化得以维持。这两个主成分可以与肢体方向（PC1*）和肢体长度（PC2*）相关联。在较低的行走速度下，跨坡度的节段间协调变化主要表现为协同变化平面的方向和 PC2的变化，其次是 PC1的变化。随着速度的增加，跨坡度的节段间协调变化与 PC1的变化更为相关，协同变化平面的方向和 PC2的变化有限。我们的研究结果表明，运动模式高度依赖于坡度和速度。在本文中，行走时下肢节段间协调的变化与身体质心轨迹的变化有关。随着坡度的变化，运动模式的改变取决于速度：在低速时，每个步长中身体的净垂直位移与肢体长度和方向的变化有关。当速度增加时，垂直位移主要与肢体方向的变化有关。
