TRAINING IN HYPOXIA VS TRAINING IN NORMOXIA IN HIGH-ALTITUDE NATIVES

To determine the interactions between endurance training and hypoxia o n maximal exercise performance, we performed a study on sedentary high -altitude natives who were trained in normoxia at the same relative (n = 10) or at the same absolute (n = 10) intensity of work as hypoxia-t rained subjects (n = 10). The training-induced improvement of maximal oxygen uptake (V over dot O-2max) in hypoxia-trained subjects was simi lar to that obtained in normoxia-trained sea-level natives submitted t o the same training protocol (H. Hoppeler, H. Howald, K. Conley, S. L. Lindstedt, H. Claassen, P. Vock, and E. W. Weibel. J. Appl. Physiol. 59: 320-327, 1985). Training at the same absolute work intensity in th e presence of increased oxygen delivery failed to provide a further in crease in V over dot O-2max. V over dot O-2max was not improved to a g reater extent by simultaneously increasing absolute work intensity and O-2 delivery during the training sessions. In addition, training in n ormoxia is accompanied by an increased blood lactate accumulation duri ng maximal exercise, leading to greater drops in arterial pH, bicarbon ate concentration, and base excess. We conclude that, in high-altitude natives, 1) training at altitude does not provide any advantage over training at sea level for maximal aerobic capacity, whether assessed i n chronic hypoxia or in acute normoxia; 2) V over dot O-2max improveme nt with training cannot be further enhanced by increasing O-2 availabi lity alone or in combination with an increased work intensity during t he exercising sessions; and 3) training in normoxia in these subjects results in a reduced buffer capacity.