Circulating levels of peripheral blood leucocytes and cytokines following competitive cycling.

The objective of the study was to determine if prolonged and strenuous cycling leads to a polarized cytokine response, and/or unique mobilization of circulating leucocyte populations. Resting venous blood samples were collected from 6 amateur cyclists, 24 hr before, and at 10-25 min and 150 min after completion of a 250-km road race (race time: 404 +/- 3.5 min). Total leucocyte counts were significantly elevated following competition. Cell counts of CD3+CD8bright+ lymphocytes were depressed by 50% 150 min after competition. A significant increase in CD4+ cells expressing the IL-2R alpha chain was evident 150 min after competition. IL-6 concentrations were greatly increased, both at 10-25 min and 150 min after competition. Resting TNF-a concentrations were approximately doubled at both time points after competition. Plasma levels of IFN-gamma, IL-10 and IL-12 were below detection thresholds at all time points. These results suggest that performance of a 6.5 h competitive cycle-race does not induce a Type-1 or Type-2-dominated cytokine response, but one that is typical of a proinflammatory cytokine response.