The unity of mind-body is apparent by exercise. One of the best mental exercises is ambulation: walking and running. The regularity of physical exercise affects cognitive quality. Conversely, mental exertion can fatigue the body.
Mental stimulation is mental exercise. Rote routine is its antithesis: the mental equivalent of physically sitting still.
Novel situations and problem-solving challenges quicken the mind. Reading, learning new constructs, such as a new language, and all sorts of arts and crafts are mental exercise, as they create a concentrated focus for the mind, and present an explorative, interpretative experience.
Exercise in natural settings is especially mentally invigorating and mood-enhancing. In pleasant weather, the park provides a better workout than the gym.