What is the primary consequence of exercising at high altitude?

When exercising at high altitude, the primary consequence often experienced is decreased stroke volume initially. At high altitudes, the partial pressure of oxygen decreases, which can lead to lower oxygen availability for the muscles. This results in a reduced ability for the heart to pump an adequate amount of blood and oxygen to meet the demands of exercise, particularly in the early stages of acclimatization. As a result, stroke volume, which is the amount of blood the heart pumps with each beat, may decrease due to a combination of factors including reduced plasma volume and increased heart rates not compensating sufficiently.

Over time, individuals may acclimatize to high altitude, which can lead to adaptations such as increased cardiac output and improved oxygen utilization, but initially, the decreased stroke volume can limit exercise performance. In contrast, the other options do not reflect the immediate physiological challenges posed by high altitude. For instance, oxygen availability decreases rather than increases, core body temperature typically remains stable with altitude changes, and while peripheral circulation can adjust, the impact on stroke volume is often more immediate and pronounced.