Changes in circulating cytokines and markers of muscle damage in elite cyclists during a multi-stage competition

The purpose of this study was to determine the changes in the basal and post-exercise plasma markers of muscular damage, lipid peroxidation and cytokines in eight male well-trained semiprofessional cyclists, in response to a three consecutive-day cycling competition. Serum markers of oxidative and muscular damage - creatine kinase activity, lactate dehydrogenase activity, myoglobin and malondialdehyde (MDA), creatinine and nitrite levels - followed a sawtooth-type representation throughout the competition. MDA showed an accumulative pattern, evidenced in the post-race values of the third stage which were significantly higher with respect to the values of the first stage. Cortisol levels were significantly influenced by an interaction between the exercise and the stage factors, with higher values on the 4th day. Plasma cytokine levels were only determined before the first stage and post-race, after the third stage. The exercise increased TNFα, IL6, IL2 and IFNγ levels, whereas IL1β was unchanged. In conclusion, cyclist stages induced oxidative and cellular muscle damage which is partially recovered to basal values by the next morning. Repetitive stages during the cycling competition accumulated plasma muscular damage and lipid peroxidation markers and pro-inflammatory cytokines, probably as a result of local inflammatory responses.