Individual variation in the erythropoietic response to altitude training in elite junior swimmers.

OBJECTIVES Inter-individual variations in sea level performance after altitude training have been attributed, at least in part, to an inter-individual variability in hypoxia induced erythropoiesis. The aim of the present study was to examine whether the variability in the increase in total haemoglobin mass after training at moderate altitude could be predicted by the erythropoietin response after 4 h exposure to normobaric hypoxia at an ambient Po(2) corresponding to the training altitude. METHODS Erythropoietin levels were measured in 16 elite junior swimmers before and after 4 h exposure to normobaric hypoxia (Fio(2) 0.15, approximately 2500 m) as well as repeatedly during 3 week altitude training (2100-2300 m). Before and after the altitude training, total haemoglobin mass (CO rebreathing) and performance in a stepwise increasing swimming test were determined. RESULTS The erythropoietin increase (10-185%) after 4 h exposure to normobaric hypoxia showed considerable inter-individual variation and was significantly (p<0.001) correlated with the acute erythropoietin increase during altitude training but not with the change in total haemoglobin mass (significant increase of approximately 6% on average). The change in sea level performance after altitude training was not related to the change in total haemoglobin mass. CONCLUSIONS The results of the present prospective study confirmed the wide inter-individual variability in erythropoietic response to altitude training in elite athletes. However, their erythropoietin response to acute altitude exposure might not identify those athletes who respond to altitude training with an increase in total haemoglobin mass.