Abstract

The common finding upon exposure to hypoxia is a transient increase in haemoglobin concentration and haematocrit because of a rapid decrease in plasma volume followed by an increase in erythropoiesis per se. Both nonathletes and elite endurance athletes have maximal reticulocytosis after about 8-10 d at moderate altitude. Training periods of 3 weeks at moderate altitudes result in individual increase of haemoglobin concentration of about 1-4. Normal erythropoietin reaction upon exposure to hypoxia comprises initially increased levels followed by a decrease after about 1 wk. Thus, the maintenance of a high erythropoietin concentration is not a prerequisite for a sustained increase in erythrocyte formation at high altitude. Adequate iron stores are a necessity for haematological adaptation to hypoxia. However, at moderate altitude, there is a need for rapid mobilisation of iron and even if the stores are normal there is a risk that they cannot be mobilised fast enough for an optimal synthesis of haemoglobin. Data from healthy athletes training at moderate altitudes suggest a true increase in haemoglobin concentration of about 10/wk. Complete haematological adaptation occurred when sea level residents have similar haemoglobin concentrations at moderate altitude compared with residents. The normal difference in haemoglobin concentrations can be estimated to be about 12 between permanent residents at sea level and at 2500 m above sea level. This difference indicates a necessary adaptation time of about 12 wks. Verf.-Referat (gekuerzt)