Why might marathon runners choose to train at altitude?

• A. To decrease red blood cell production
• B. To increase partial pressure of oxygen
• C. To stimulate erythropoietin production and increase red blood cells
• D. To avoid any adaptation in oxygen carrying capacity

Answer: (C)

Altitude training works because the lower oxygen environment creates a hypoxic stimulus that increases erythropoietin production by the kidneys, which drives more red blood cell production in the bone marrow. More red blood cells raise the blood’s oxygen-carrying capacity, helping marathon runners deliver more O2 to working muscles during long efforts, especially after returning to sea level. The optical idea here is to boost the body’s oxygen transport system, so performance can improve with training that exploits this adaptation. The oxygen partial pressure is actually reduced at altitude, not increased, and the body does develop greater oxygen transport capacity rather than avoiding adaptation.