人和一切物体所以能够运动是由于外力的作用,牛顿第一定律告诉我们:“物体如果不受外力的作用将保持静止或匀速直线运动状态”。在跑的过程中人体受哪些外力的作用,这些外力对跑的影响如何呢?现分述如下:1.重力:地面上的一切物体都受地球的吸引,我们就把这种吸引力叫做重 People and all objects are able to exercise because of external forces, Newton’s first law tells us: “If the object will not be subject to external forces will remain stationary or uniform linear motion.” What are the external forces on the human body in the course of running? How are these external forces exerting on the running? These are as follows: 1. Gravity: All objects on the ground are attracted by the earth, and we call this attraction the weight