Final answer:
Olympic runners train at higher elevations because the body adapts to lower oxygen levels by producing more hemoglobin and releasing oxygen more effectively to tissues, which enhances performance at sea level.
Step-by-step explanation:
Olympic runners and other athletes train at higher elevations to improve their performance due to the body's physiological adaptations to lower oxygen levels. At high altitudes, due to a decrease in air pressure and oxygen concentration, the body experiences hypoxia. To compensate, it produces more hemoglobin, improving the oxygen-carrying capacity of the blood. This adaptation takes about 10 days and results in enhanced performance at sea level, where oxygen is more plentiful. Additionally, at higher altitudes, a greater amount of BPG (bisphosphoglycerate) is produced by erythrocytes (red blood cells), which promotes the release of oxygen from hemoglobin into the tissues. Altitude training can lead to an increase in erythrocyte concentration when acclimating to the lower plasma volume, due to increased urination at high altitudes.
Furthermore, different human populations have developed unique adaptations to high-altitude environments over time. Indigenous populations in the Andes have naturally higher concentrations of hemoglobin, whereas Tibetans breathe more rapidly to compensate for the shortage of oxygen. The training at high altitude is a non-genetic way for athletes to gain some of these performance advantages.