The stereotypical "Naruto Run", bent almost double with arms held parallel and swept back like an airplane's wings, is an eternal element of mockery from anime fans. Often this is (rightly) called out as a way to reduce on-screen motion and thus get away with less animation work, but what if there was an in-universe model for it that actually made sense? After some experimentation using shallow water to simulate the effects of a ki field, I noticed something. If you assume that the ki field is "light" ki with a lifting effect, then holding the body in that position drastically reduces the weight being pushed down the legs by nullifying gravity, allowing more of the muscle (and ki) energy in running to be dedicated to pure forward motion. Naruto running should therefore be understood as a martial arts version of the ekranoplan or hovercraft, using lift effects to generate faster motion along the ground. Practitioners of aikido or tai chi or qigong should be familiar with the light vs. heavy ki distinction, with "heavy" ki being used for rooting oneself to the ground and "light" ki being used for jumps or other upward motion.
This is of course all complete nonsense under our understanding of real physics, but it was fun to think about while I was at the beach.