PROLONGED SUBMAXIMAL ECCENTRIC EXERCISE IS ASSOCIATED WITH INCREASED LEVELS OF PLASMA IL-6

To study the relationship between exercise-related muscle proteolysis and the cytokine response, a prolonged eccentric exercise model of one leg was used. Subjects performed two trials [a branched-chain amino a cid (BCAA) supplementation and a control trial]. The release of amino acids from muscle during and after the eccentric exercise was decrease d in the BCAA trial, suggesting a suppression of net muscle protein de gradation. The plasma concentrations of interleukin (IL)-6 increased f rom 0.75 +/- 0.19 (preexercise) to 5.02 +/- 0.96 pg/ml (2 h postexerci se) in the control trial and in the BCAA supplementation trial from 1. 07 +/- 0.41 to 4.15 +/- 1.21 pg/ml. Eccentric exercise had no effect o n the concentrations of neutrophils, lymphocytes, CD16+/CD56+, CD4+, C D8+, CD14+/CD38+, lymphocyte proliferative response, or cytotoxic acti vities. BCAA supplementation reduced the concentration of CD14+/CD38cells. This study shows that the concentration of IL-6 in plasma is in creased after prolonged eccentric exercise and suggests that the cytok ine response is independent of the muscle proteolysis that occur durin g exercise.