Changes in erythropoiesis assessed by reticulocyte parameters during ultralong distance running.

Objective: To investigate the possibility of early changes in erythropoiesis during prolonged exercise being reflected in reticulocyte parameters.

Design: This was a case-control field study of hematological variables in a group of ultramarathon runners competing in a 6-day track race.

Setting: A 6-day ultramarathon in Colac, Australia.