Plasma endotoxin and immune responses during a 21-km road race under a warm and humid environment

This study investigated the responses of plasma endotoxin and pro- and antiinflammatory cytokines during a 21-km road race in warm and humid conditions. The influence of carbohydrate-electrolyte (CE)-water (WA) drink mix ingested on leukocyte subset responses and the association between plasma lipopolysaccharide (LPS) concentration and fluid balance, exercise intensity, and body core temperature (Tc) were also studied.

Thirty runners provided blood samples before and after the half-marathon for leukocyte, LPS and cytokine analyses. Tc was measured by the ingestible telemetric temperature sensor and fluid intake and split-times were recorded at 3 km intervals. Exercise intensity was determined by matching running speed and heart rate during the race with the corresponding speed-oxygen uptake relationship and heart rate measured in the laboratory 2 to 6 weeks before the race.

Plasma LPS concentration increased from 1.9 +/- 1.9 pg/mL before, to 2.5 +/- 1.9 pg/mL after running (P <0.05). Peak plasma LPS concentration was 7.5 pg/mL. Plasma IL-1beta and TNF-concentration did not change significantly, whereas significant increases in IL-10 (50%), IL-1ra (23.2%) and IL-6 (65.2%) were observed after the race. No significant correlation between plasma LPS concentration and exercise intensity, hydration and Tc was observed.

Leukocyte subset responses were not related to the ratio of CE and water drink mix ingested. Running a half-marathon can induce mild endotoxaemia, which is not related to exercise intensity, fluid balance, and Tc responses. Mixing CE drink with water did not mitigate postexercise leukocytosis and lymphopenia.