When he crawls, he only front of the foot touches the floor, and if the shoes are too hard they will not allow his toes to move, which will cause friction and disturb his movements.

• 当他在爬行的时候，只有脚的前端会接触到地板，如果鞋子太硬，他可能没有办法移动他的脚趾头，而且这样的磨擦也会妨碍他的移动。