The physiological cornerstone of running performance is aerobic capacity, or the body’s ability to extract oxygen from the environment and use it to release energy from muscle fuels. The human aerobic system includes the heart and lungs, the arteries and capillaries that deliver blood to the muscles, the blood itself, and mitochondria, which are little “factories” within muscle cells where oxygen is used to release energy from metabolic fuels. Running induces changes in all of these organs that serve to increase aerobic capacity.
