Change in interleukin (IL)-6, 8, and 10 and its association with an increase in core temperature following a 7-mile running race in the warm weather.

The purposes of this study were 1) to investigate if cytokines were increased following a running road-race, and 2) to examine associations between cytokines and hyperthermia. Seventy-seven recreational runners participated in this study which occurred at the 7-mile race in the heat (ambient temperature, 25.0-26.7°C; %RH, 56.7-79.0 ± 5.0%). Before and following the race, blood draws were performed to measure circulating inflammatory cytokines. Core temperature was measured using an ingestible thermistor throughout the race. Core temperature was significantly higher at post-race (39.5 ± 0.7°C) than pre-race (36.9 ± 0.4°C, p < 0.001). IL-6, IL-8, and IL-10 significantly increased at post-race (IL-6, 48.0 ± 22.3 pg⋅ml^-1; IL-8, 63.8 ± 23.9 pg⋅ml^-1; IL-10, 29.2 ± 20.0 pg⋅ml^-1) compared to pre-race (IL-6, 28.4 ± 13.6 pg⋅ml^-1; IL-8, 53.2 ± 19.4 pg⋅ml^-1; IL-10, 18.6 ± 11.9 pg⋅ml^-1, p < 0.001). A greater increase in core temperature pre- to post-race was predicted by the faster finish time, a greater increase in IL-6, and greater body mass loss during the race (r² = 0.298, p < 0.001). Small associations were found between IL-8 and core temperature at post-race (r = 0.255, p = 0.025). In conclusion, cytokines concentrations and core temperature increased following the race. Moreover, post-race hyperthermia is associated with increased IL-6, faster finish times, and higher body mass losses.