For nearly a century, the medical community has viewed the human body as a collection of specialized, somewhat isolated departments. The heart is for circulation; the muscles are for movement; the brain is for thought. Under this fragmented model, neurodegenerative diseases like Alzheimer’s were treated as local failures — internal storms within the skull that had little to do with the strength of one’s legs or the vitality of one’s grip. New research is revealing that skeletal muscle is not merely a mechanical tissue, but a sophisticated endocrine organ that communicates with the brain through a stream of molecular messengers called myokines. When we move, our muscles secrete proteins that travel through the bloodstream, can cross the blood-brain barrier, and can act as a maintenance crew for our neurons.