Cross country skiers and triathletes (M = 17; F = 5) were observed while training at sea level and living in simulated normobaric hypoxia (sea level pressure but altitude oxygen reduction). The simulated environment was experienced for 12-16 hours per day. The study lasted 25 days. VO2max was measured before, immediately after, and one week after the experience while red cell mass and erythropoietin (EPO) were measured before, on days 2, 11, 18, and 25, and 4-7 days after. On days 2 and 25, EPO was 60% and 14% higher than the before measure. EPO was not related to the increase in red cell mass, which changed +5% between before and immediately after the acclimatization period. VO2max changed in a different and delayed manner. It was only after the seven days post-experience that it improved by +3%, for there was no significant change during the experience itself. The absence of any relationships between VO2max, red cell mass, and EPO concentration is puzzling. These factors are supposed to be interrelated. For example, EPO is purported to increase the oxygen carrying capacity of the blood, which is principal the reason for its popularity among endurance cyclists, but that was not observed here. In a similar vein, EPO is supposed to increase the concentration and number of red cells in the blood. However, here EPO concentrations and red cell mass were unrelated while VO2max was unrelated to either factor. This study raises more questions than it answers and seems to "shake" some popular understandings about hemodynamics and usable oxygen capacity. Implication: An artificial environment of sea level pressure with simulated altitude oxygen reduction stimulates changes in red cell mass, EPO, and VO2max, but in a seemingly unrelated manner.
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