Leucocyte and erythrocyte counts during a multi-stage cycling race ('the Milk Race').

Venous blood samples were taken from eight competitors in mid-evening after a racing day, and in the early morning before the next day's race, three times during the course of the Milk Race, 1992. These were used to gather information about the changes in circulating leucocyte levels in response to the exceptionally high sustained daily workload required during a major multi-stage race. The primary objective was to provide knowledge of 'normal' values against which future clinical judgements of abnormality might be made in these unusual circumstances. During the race, estimated energy output was about 25 MJ (6000 kCal)/day. The mean total circulating leucocyte numbers (per litre of blood), and those of individual leucocyte classes (neutrophil, lymphocyte, monocyte, eosinophil and basophil) were all inside the normal range both in the morning and in the evening. Evening counts were, however, 30-50% higher than morning counts, for all classes except eosinophils. We conclude that individual clinical decisions about leucocyte levels can best be made using normal (sedentary man) values if a morning sample is taken.