Classical altitude training can cause an increase in total hemoglobin mass (THM) if a minimum "dose of hypoxia" is reached (altitude ?2 000 m,?3 weeks). We wanted to find out if repetitive exposure to mild hypoxia during living and training at low altitude (<2 000 m) for several weeks, often performed by elite athletes, might also have significant effects on erythropoiesis. THM, erythropoietin (EPO), soluble transferrin receptor (sTfR) and ferritin were determined in 8 elite runners before and after each of 2 training camps at low altitude interspersed by 3 weeks of sea-level training and at the same time points in a control group (CG) of 5 well-trained runners. EPO, sTfR and ferritin were also repeatedly measured during the altitude training camps. Repeated measures ANOVA revealed significant increases in EPO- and sTfR-levels during both training camps and a significant decrease in ferritin indicating enhanced erythropoietic stimulation during living and training at low altitude. Furthermore, significant augmentation of THM by 5.1% occurred in the course of the 2 altitude training camps. In conclusion, repetitive living and training at low altitude leads to a hypoxia-induced increase in erythropoietic stimulation in elite 400 m and 800 m runners and, apparently, might also cause a consecutive augmentation of THM.
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