What is a key adaptation of the cardiovascular system to high-altitude training?

The key adaptation of the cardiovascular system to high-altitude training is increased red blood cell production. When training at high altitudes, the body is exposed to lower oxygen levels in the environment. In response to this hypoxic condition, the kidneys release a hormone called erythropoietin (EPO), which stimulates the bone marrow to produce more red blood cells. This increase in red blood cell production enhances the blood's oxygen-carrying capacity, allowing for improved oxygen delivery to the muscles during physical activity, which is crucial for endurance performance.

This adaptation is significant because it helps athletes improve their aerobic capacity and stamina when they return to lower altitudes, where more oxygen is available. This physiological change can lead to better performance in endurance sports as the body becomes more efficient in utilizing the available oxygen, thereby benefiting overall athletic performance.