Leukocyte Subset Changes in Response to a 164-km Road Cycle Ride in a Hot Environment

The purpose of this observational study was to determine the circulating leukocyte subset response to completing the 2013 Hotter’N Hell Hundred recreational 164-km road cycle event in a hot and humid environmental condition. Twenty-eight men and four women were included in this study. Whole blood samples were obtained 1–2 hours before (PRE) and immediately after (POST) the event. Electronic sizing/sorting and cytometry were used to determine complete blood counts (CBC) including neutrophil, monocyte, and lymphocyte subsets. The concentration of circulating total leukocytes (103·μL−1) increased 134% from PRE to POST with the greatest increase in neutrophils (319%, p