Development of of pseudoanemia in marathon runners during a 20-day road race

Abstract

RBC [red blood cell] count, blood Hb concentration and related hematologic factors in 12 male marathon runners during a 20 day, 312 mile road race. The RBC and Hb levels decreased significantly, from 5.17 million/mm3 and 16.0 g/dl, respectively, to 4.36 million/mm3 and 13.4 g/dl. Although the runners became marginally anemic during the race, their running speeds were not significantly changed. There were no abnormal clinical signs other than rare instances of hematuria. A sudden increase in long-distance running mileage above the regular training level may cause sports anemia, a functional pseudoanemia that, in mild cases, does not impair endurance performance.