There's no way to jump forward in the process, only backward. You can see this breadcrumb trail in action in Figure 1.
您不可能跳转到过程的前面，而是只能向后跳转。
2
So, the action of extending the leg backward creates a forward and upward movement (the flight phase).
因此，腿向后伸展的作用力，产生一个向前向上的运动(腾空阶段)。
3
In different working conditions, fast, slow walk, only one person can be in the air continuously complete upper and lower, forward and backward, turning all the action.