This document discusses the effects of exercise on various body systems. It outlines how aerobic endurance training leads to increased muscle fiber size, vascularization, energy stores, and force exertion. It also describes adaptations like increased mitochondria, lactate tolerance, and fat metabolism efficiency. Additionally, it notes that exercise results in increased red blood cell volume and lower blood viscosity to enhance oxygen transport. Finally, it compares breathing during exercise versus rest, noting exercise involves deeper, faster breathing using primary muscles while expiration is more active.