Systemic Cytokine Changes In Children During Prolonged Intense Exercise

Abstract

Among the multiple components of the immune response to exercise, a key role is played by systemic changes in pro- and anti-inflammatory cytokines. Despite consensus on their overall importance, however, the kinetics of individual cytokines during and following exercise are still unclear, with some studies reporting exercise-induced systemic elevations while others reporting no change. This conflicting information is particularly scarce in children, who display different metabolic and immunologic responses compared to adults. PURPOSE: To define the kinetic profiles of key pro- and anti inflammatory cytokines in children during intermittent, intense exercise. METHODS: 21 healthy children (13.9 ± 0.8 yrs, 8M/13F) performed 10 bouts of 2-min cycling at ∼80% VO2max, separated by 1-min intervals. Blood samples from a forearm I.V. line were drawn at baseline, after every other exercise bout, and 10, 20, and 30 min post exercise; plasma was stored at −80°C for later cytokine assays. RESULTS: Most cytokines initially decreased reaching a nadir ∼10–15 min into exercise, then increased to above-baseline by end-exercise (IL-1 α, IL-6, IL-8), or remained moderately decreased throughout the study (IL-4, IL-1RA, TNF-α, GM-CSF, Eotaxin, EGF). A second nadir also occurred immediately after exercise for most cytokines, with return to baseline by 30 min post. CONCLUSION: Key immuno-modulatory cytokines display individual nadirs/peaks at different time points during intense exercise in healthy children, suggesting that detection of absolute changes relative to baseline depends on exercise duration, sampling timing and possibly on exercise type and intensity.Figure