Training in height the works due to the atmospheric pressure differential between the level of the sea and the high altitude. At the level of the sea, the air is denser and is more gas molecules by liter of air. Due to the atmospheric pressure he is smaller in the high altitudes, the air he is less dense and there is less gas molecules by liter of air, which causes a diminution of the partial gas pressures in the body, that causes a variety of physiological changes in the body which they happen to high altitude.
The physiological adaptation that is in charge mainly of the obtained gains of yield of training in altitude, is a subject of discussion between the investigators. Some, including American investigators Ben Levine and Jim Stray-Gundersenaffirm that it is mainly the increase of volume of the red cell of blood. Others, like Australian investigator Chris Gore, and New Zealand investigating Will Hopkins, denies this affirmation and instead of the gains they are mainly the result of adaptations such as a change towards a economic way of the oxygen use.