The tendency to compartmentalize mind and body never made sense to me. The brain is adapted to navigating the physical world, so it should be unsurprising that physical exercise is a prerequisite to proper functioning. Why else would the "memory palace" be a thing? If our memory/perception is inherently spatial, then it relies on a privileged observer capable of interacting with its environment. The rest of the nervous system is basically just feeding you training data when you exercise.