Notice how they make contact with the ground as they roll from heel to toe and then travel through the air to stride forward.
留意它们是如何从脚跟到脚趾接触地面，然后离开地面向前迈进。
2
Walking is also called heel and toe walking. The heel of the form foot hits the ground just before the toe of the back foot leaves the ground. So one foot is in contact with the ground at all times.
竞走也称作足踵和足趾走。前足踵着地后足趾才能抬起来。因此，必须有一只脚始终着地。
3
Nail polish (toe nail polish is also the case) is made of synthetic resin dissolved in solvent, mixed with pigments to color and blend, and therefore it has cut off contact with the external role.