Cardio-respiratory adaptation to physical exercise and hypoxia after a high-altitude expedition.

Seven young, male subjects were tested before and immediately after 6 weeks high-mountain expedition. Cardio-respiratory measurements were performed at rest and during standard physical excercise (10 min, 100 W) when breathing atmospheric air or hypoxic mixture (14% O2 in N2). After the expedition an increased V o2 max (16% an average) and diminished heart rate response to submaximal exercise were found. This was observed during air and hypoxic mixture breathing. There was significant increase in stroke volume and cardiac output during the exercise. No significant differences in ventilatory parameters were found nor at rest or during exercise under condition of breathing atmospheric air or hypoxic mixture. No changes in erythrocyte count or haemoglobin concentration in the blood were found. The physiological changes which developed during high-mountain expedition were more dependent on physical that hypoxic training.