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46 Clinical Biomechanics in Human Locomotion: Gait and Pathomechanical Principles 1st Edition
《人体运动的临床生物力学：步态和病理力学原理 第1版》
作者： Andrew Horwood, Nachiappan Chockalingam（英国）
2023.4.27出版 934页

尽管使足跟抬起的力量主要来自小腿三头肌，但正是在支撑中期的离心收缩过程中储存于跟腱内的能量释放，为足跟离地提供了所需的动力。足跟抬起的力量将位于跖趾关节（MTP）作为支点（F 和垂直虚线）之后的所有下肢质量抬起。这部分下肢质量包括后足和小腿，构成了需要移动的阻力（R - 灰色圆圈）。然而，由跖屈力驱动的足跟抬起所实现的远不止抬起 R 这么简单。通过迫使脚在踝关节处跖屈以对抗地面，跖屈力产生了一个向前倾斜的大地面反作用力（GRF），使身体的质心向前和向下加速，从而协助重力作用。这会使摆动腿下降约 1 厘米，加快与支撑面接触的速度，从而结束摆动阶段。尽管这种二级杠杆系统在步态的终末站立期主要不是将身体的质心向前移动（重力和摆动腿的离心力会起到这一作用），但它在这一阶段对步态的作用有助于将体重“推”向对侧肢体，为髋关节-骨盆-躯干的质心增加动量，这种动量可以持续到对侧的早期站立期。
Although the power that brings about heel lift derives primarily from the triceps surae muscles, it is the release of energy stored within the Achilles from the midstance eccentric muscle contraction that supplies the effort required to spring the heel off the ground. The heel lift effort raises all of the lower limb mass lying behind the metatarsophalangeal (MTP) joints acting as the fulcrum (F and vertical dashed line). This lower limb mass, consisting of the rearfoot and lower leg, provides the resistance to be moved (R—grey circle). However, plantarflexion-powered heel lift achieves so much more than lifting R. By forcing the foot to plantarflex at the ankle against the ground, the plantarflexion power generates a large GRF angled anteriorly that accelerates the body's CoM forward and downward, assisting gravity. This drops the swing limb around 1 cm to accelerate the rate of contact with the support surface, ending swing phase. Although this class two lever system does not primarily move the body's CoM anteriorly (gravity and centrifugal forces from the swing limb do that), the effort it applies to gait during the terminal stance phase helps "power' weight transfer onto the opposite limb, adding momentum to the HAT's CoM that can persist into contralateral early stance phase.