Systemic Responses of Inflammation-Related Factors Following Eccentric Exercise in Humans

Background: Exercise-induced muscle damage is followed by muscle adaptation which has been associated with an inflammatory response and is influenced by a crucial balance between pro- and anti-inflammatory cytokines. This study investigated the pattern of systemic cytokine responses for several hours after muscle-damaging exercise. Methods: Nine healthy, young men volunteers performed 50 maximal eccentric muscle actions with each leg using the knee extensors. Serum levels of interleukin (IL)-1α, IL-2, IL-6 and IL-10, transforming growth factor (TGF)-β1 and tumor necrosis factor (TNF)-α were measured by ELISA before and at 6, 48 and 120 hours post-exercise. Results: Volunteers reported significant muscle soreness and their serum creatine kinase (CK) activity increased gradually up to 120 hrs post-exercise (p<0.05). Circulating levels of IL-1a remained unaltered and TGF-β1 increased slightly over time, while IL-2 showed a moderate increase 48 hrs following eccentric exercise (p>0.05). Levels of TNF-α and IL-10 exhibited a similar pattern of response over time, showing a nearly 50% and 100% increase, respectively, 6 hrs post-exercise, while IL-6 increase significantly 6 and 48 hrs post-exercise (p<0.05). Conclusion: These findings suggest that eccentric exercise might trigger a systemic, predominantly anti-inflammatory, acute cytokine response as part of the adaptation process to muscle damage, where IL-6 may be especially involved.