Hey. I'm a serious runner, and lately I've become very interested in biomechanics and running form. One thing I've found very interesting is a subset of running systems based around the concept of using gravity for forward motion. The general idea is that by keeping a straight body, but bending forwards at the ankles, one goes into something of a freefall forwards. The legs are then swung under the body to catch it in its fall. The benefit, obviously, is that the job of providing forwards momentum shifts from the muscles of the legs to gravity. Does that actually make sense from a physics perspective? Something doesn't seem right about it to me, but I'm a high-school student just taking Honors Physics this year.