Skeletal muscle is the only organ system you can voluntarily control, and it directly determines your health, fertility, brain function, and longevity. Dr. Gabrielle Lyon reveals how resistance training and proper nutrition prevent Alzheimer's, cardiovascular disease, and metabolic decline starting now—not at 60. Your choices today determine which version of you exists in 30 years. Skeletal muscle functions as an endocrine organ releasing myokines that affect brain health, mood, neurogenesis, and systemic inflammation through intensity and duration of exercise.