"It is more than the simple athleticism of the mens sana in corpore sano. The conception of the body as perfect instrument of the increasing intelligence pervades." (Ezra Pound)
Our spiritual lives begin in the body. Anyone who has ever learned how to do anything with their hands (to draw, or play the piano, for example) or even someone who has simply spent some time "getting into shape" (swimming, for example, or running) knows that it is not merely a bodily change. The body changes, but so does the way we think and feel. I want to say that physical exercise (or training in any art) transforms the musculature and the imagination. We experience a change in both our volition and our intelligence, which is experienced as a transformation of experience itself.
Mastery of any set of stylized movements, whether those required to play a fugue on a piano or those required to run 10 kilometers at a steady pace over hilly terrain, requires the formation of the appropriate muscles and their coordination in activity (what scientists probably talk about as the formation of "neuronal pathways"). It is a shaping of the flesh. This reshaping of the fleshy basis of experience (what Kant called "the conditions of the possibility of the experience of objects") is what transforms our imagination. The new flesh yields up new images in the confrontation of sensory stimulus and motor impulse.
The images occasion thoughts and feelings and, from these, belief and desire. These latter, "propositional", states have content, which is "represented" in science and politics. The presence that is here re-presented, however, is the body.