Living at altitude increases aerobic power at sea level mainly by increasing the ability of the circulatory system to transport oxygen to the muscles. During approximately the first three weeks of training at altitude the amount of substance known as EPO increases. This stimulates the production of extra red blood cells. With extra red blood cells the capability of the blood to provide oxygen to the muscles is increased. This is especially beneficial to runners or other athletes in aerobic events lasting two minutes or longer.

Merely living and training at a high altitude is not very beneficial for an athlete. To gain the most benefit it is necessary for the athlete to live in conditions such as those at altitude and to train in conditions that are like those where the competition will take place, typically close to sea level. This can occur in one of three ways: The athlete does in fact live at high altitude and train at low altitude (The least practical solution); The athlete lives at high altitude and trains with an oxygen mask to simulate sea level; or the athlete lives and trains at sea level but makes use of altitude house or tent, where there is more nitrogen in the air.

There can be problems associated with training at high altitude however. If insufficient iron is present within an athlete’s diet or body then there will be no increase in the number of red blood cells, and therefore no benefit to the altitude training. Since living at altitude has a detraining effect, there will then be a disadvantage to the training. Living at excessive altitude can exacerbate this same detraining problem and thus make this more than make up for any benefits that may have been gained.

Finally, living at altitude makes one more susceptible to the effects of malnutrition and vitamin deprivation. Hypoxia leads to a decreased appetite and thus decreased calorie intake.