Altitude and hypoxia training--a short review.

The importance of oxygen transport and consumption in the body for endurance performance is the reason why altitude training as preparation for competitions at sea level has become popular. In hypoxia maximal O2 uptake decreases. Thus for equal work load training at altitude is harder and stimulates adaptation processes more than sea level training. A specific altitude training effect, however, can only be proven if a relative equal load (in % of VO2max) is more effective than during sea level training. In only three of 10 investigations with this design has a significant improvement of either maximal performance, VO2max or endurance been found, in two there was a nonsignificant tendency. When training in hypoxia combined with living in normoxia was investigated two of four groups improved. Living in hypoxia with training in normoxia is probably more effective but only preliminary publications are available. Summarizing, a small specific altitude effect on performance capacity seems to exist, which may be counteracted by negative influences like reduced stimulation of muscular metabolism. A series of single physiological changes at altitude might have positive or negative implications on training success: training of respiratory muscles, increase of hypoxic ventilatory stimulation, reduced heart training by vegetative "braking", increase of red cell and plasma volume (the latter after descent), right shift of the oxygen dissociation curve, increase of oxidative muscle enzymes (only after hypoxia training), shift from fat and muscle glycogen to blood glucose combustion, reduced lactic acid and ammonia production, increase in buffer capacity.