Every movement is believed to have a mechanical efficiency, yet not known for running. The more you drop your feet to the front, the faster you will run backward. It is proven science, because nothing you can do will change that from happening. If you try to push and jump instead of vault, you will be wasting energy. The same is true if you increase your stride length beyond what you are forced to do by the speed of the run.
Right leg is shown over a two stride range.
Left leg, not shown, alternates the same way. The body always stays erect for efficiency and less back muscles stress. Standing still position requires very little muscle use. Frame supports the body. Quadriceps muscles lock knee as the body is shifted forward.