Effect of Exercise Intensity on the Cytokine Response to an Acute Bout of Running

We compared the effects of exercise intensity (EI) on the cytokine response to an acute bout of running. Ten males (mean ± SD VO(2max)= 56.2 ± 8.1 mL·min(-1)·kg(-1)) completed three, counterbalanced, 8-d trials. After three control days, on day 4, participants completed 60 min of running at 55%, 65%, and 75% VO(2max). The cytokines tumor necrosis factor (TNF)-α, interleukin-1β (IL-1β), IL-6, and IL-1 receptor antagonist (ra), and creatine kinase were measured during and for 3 h after exercise and on four follow-up days (FU1-FU4). RER was higher at 75% V(O2max) compared with both 55% (P < 0.001) and 65% (P < 0.01) VO(2max). IL-1β was undetectable in six participants. There was a small (18%-27%) increase in TNF-α during exercise but no effect of EI. IL-6 concentrations peaked at the end of exercise, with a greater increase at 75% VO(2max), resulting in higher concentrations at the end of exercise and at 30 min after exercise compared with 55% (P < 0.001) and 65% VO(2max) (P < 0.01). IL-1ra concentrations peaked at the end of exercise at 75% VO(2max), resulting in higher (P < 0.05) concentrations at 1-2 h after exercise compared with 55% and 65% VO(2max). Creatine kinase was increased at FU1 and FU2, but there was no effect of EI. Sixty minutes of treadmill running at 75% VO(2max) results in a greater increase in IL-6 but not TNF-α compared with 55% and 65% V(O2max). The higher IL-1ra concentrations at 75% VO(2max) might be related to the higher IL-6 concentrations that precede them.