Altitude training has been used by athletes since 1968 under the premise that the changes associated with acclimatisation would provide an advantage when competing at sea level. Initial responses to hypoxia at altitude include hyperventilation and increased heart rate as the body attempts to improve alveolar oxygenation and haemoglobin saturation. The hyperventilation leads to an increase in blood pH due to the increase in expiration of CO2. Acclimitisation to altitude occurs after a period of two to three weeks. Alkaline excretions via the kidney compensates for the increase in blood pH. The alkaline excretion also reduces the buffering capacity of the blood and therefore the tolerance to the accumulation of lactic acid. Altitude training results in an increase in the oxygen carrying capacity of the blood. These changes include an increase in haemoglobin concentration and an increase in the haematocrit, with a concurrent reduction in plasma volume (Sutton, Reeves, Groves, Wagner, Alexander, Hultgren & Cymerman, 1992). Other changes as a result of altitude training are; increased water loss through evaporation as the result of increased ventilation and reduction of the water carrying capacity of the air and; a reduction in stroke volume and maximal HR consequently resulting in a lower maximum cardiac output (Sutton,et al, 1992). It was thought that the increased oxygen carrying capacity of the blood as a result of acclimitisation, would provide the athlete with an advantage over those who trained at sea level. However it appears that these possibly advantageous adaptations might be outweighed by the decrease in stroke volume and heart rate which is also experienced and the resultant reduction in the intensity of the training that is able to be performed at altitude. In summary, athletes training at altitude are unable to train as intense at high altitude as because even though they are able to reach the same percentage VO2 max, their maximum is less. The physiological adaptations to altitude are not all necessarily beneficial at sea level. Although the increase in haemoglobin may be helpful, the decrease in plasma volume and possible decrease in alkaline reserve may be disadvantageous (Rose, Houston, Fulco, Coates, Sutton & Cymmerman, 1988).