If I may intervene, my dear boy.....
I do believe that my good friend and colleague Mr. Lees was inferring from the phrase (and the context of your original usage of it) - correctly, in my view - that it signified striking the surface of the earth with the legs approximating a running action whilst being held in mid-air and then subsequently being dropped onto the surface, effectively from a static start, but not at rest - at speed (thereby usually rendering it exceptionally difficult to gauge the required speed in order to ensure a smooth transition from mid-air to the surface of the ground without falling flat), although of course, doing the same from an actual static start often has the same result. I do not believe that the subsequent landing on the ground after leaping to vault a hurdle - when the forward motion of one's body is inherent, and the momentum is therefore easily maintained, is what is implied by this particular metaphor.
I do hope that this has been helpful.
