Reduction of Hb levels during the racing season in nonsideropenic professional cyclists

Hematological variables of 40 professional cyclists, all receiving intravenous iron supplementation, were followed during a 15-month period. Mean values for red blood cells (RBC), hemoglobin (Hb), and hematocrit (Ht) were significantly lower during the racing season (RS) than during the nonracing periods (NRP) (RBC: RS = 4.53±0.34 millions/mm3, NRP = 5.09±0.36 millions/mm3; line 7 of abstract: Hb: RS = 14.2±0.9 g/dl, MRS =15.2±0.9 g/dl; Ht: RS = 40.7±2.7% NRP = 44.4±2.9%; P<0.001 for all). However, mean values for ferritin and mean corpuscular hemoglobin (MCH) were significantly higher during the racing season (ferritin: RS = 422±398 ng/ml, NRP=311±321 ng/ml, P<0.05; MCH: RS=31.5±1.3 pg, NRP=30.0±1.4pg; P<0.001). These results suggest that the reductions in RBC, Hb, and Ht found in professional cyclists during the racing season are not the consequence of a diminution of iron stores but rather of reduced erythropoiesis and increased RBC destruction.