Laboratory of Biomechanics and Physiology of Locomotion, Institute of NeuroScience, Université catholique de Louvain, Louvain-la-Neuve, Belgium.
Laboratory of Biomechanics and Physiology of Locomotion, Institute of NeuroScience, Université catholique de Louvain, Louvain-la-Neuve, Belgium.
J Biomech. 2019 Jan 23;83:298-304. doi: 10.1016/j.jbiomech.2018.12.024. Epub 2018 Dec 27.
When running, energy is lost during stance to redirect the center of mass of the body (COM) from downwards to upwards. The present study uses a collision-based approach to analyze how these energy losses change with slope and speed. Therefore, we evaluate separately the average collision angle, i.e. the angle of deviation from perpendicular relationship between the force and velocity vectors, during the absorptive and generative part of stance. Our results show that on the level, the collision angle of the absorptive phase is smaller than the collision angle of the generative phase, suggesting that the collision is generative to overcome energy losses by soft tissues. When running uphill, the collision becomes more and more generative as slope increases because the average upward vertical velocity of the COM becomes greater than on the level. When running downhill at a constant speed, the collision angle decreases during the generative phase and increases during the absorptive phase because the average downward vertical velocity of the COM becomes greater. As a result, the difference between the collision angles of the generative and absorptive phases observed on the level disappears on a shallow negative slope of ∼-6°, where the collision becomes 'pseudo-elastic' and collisional energy losses are minimized. At this 'optimal' slope, the metabolic energy consumption is minimal. On steeper negative slopes, the collision angle during the absorptive phase becomes greater than during the generative phase and the collision is absorptive. At all slopes, the collision becomes more generative when speed increases.
跑步时，能量在支撑阶段会从向下转移到向上，从而损失了身体质心（COM）的能量。本研究采用基于碰撞的方法来分析这些能量损失如何随坡度和速度而变化。因此，我们分别评估了支撑阶段吸收和产生阶段的平均碰撞角，即力和速度矢量之间偏离垂直关系的角度。研究结果表明，在水平面上，吸收阶段的碰撞角小于产生阶段的碰撞角，这表明碰撞是产生的，以通过软组织克服能量损失。当上坡跑步时，随着坡度的增加，碰撞变得越来越具有生成性，因为 COM 的平均向上垂直速度变得大于水平面上的速度。当下坡跑步且速度恒定时，在产生阶段碰撞角减小，在吸收阶段碰撞角增大，因为 COM 的平均向下垂直速度变得更大。因此，在水平面上观察到的产生和吸收阶段的碰撞角之间的差异在约-6°的浅负斜率上消失，此时碰撞变得“准弹性”，碰撞能量损失最小。在这个“最佳”斜率下，代谢能量消耗最小。在更陡的负斜率上，吸收阶段的碰撞角大于产生阶段的碰撞角，碰撞是吸收性的。在所有坡度下，随着速度的增加，碰撞变得更加具有生成性。
