" You know what kind of nerves are in your feet? The same ones that network into your genitals. Your feet are like a minnow bucket full of sensory neurons, all of them wriggling around in search of sensation. Stimulate those nerves just a little, and the impulse will rocket through your entire nervous system; that’s why tickling your feet can overload the switchboard and cause your whole body to spasm. "

― Christopher McDougall , Born to Run: A Hidden Tribe, Superathletes, and the Greatest Race the World Has Never Seen