translation.en: We have an arch in our foot that acts like a spring, short toes that are better for pushing off than for grasping tree limbs, and when we run, we can turn our torso and our shoulders like this while keeping our heads straight.
translation.zh: 我们的脚上有一个类似于弹簧的拱， 短的脚趾对于抓住树干而言更适合 蹬出， 并且在我们奔跑时， 我们可以转动我们的身体和肩膀 如同保持头部向前一样。