il-6 had previously been classified as a proinflammatory cytokine. therefore, it was first thought that the exercise-induced il-6 response was related to muscle damage. however, it has become evident that eccentric exercise is not associated with a larger increase in plasma il-6 than exercise involving concentric “nondamaging” muscle contractions. this finding clearly demonstrates that muscle damage is not required to provoke an increase in plasma il-6 during exercise. as a matter of fact, eccentric exercise may result in a delayed peak and a much slower decrease of plasma il-6 during recovery.