Effects of unaccustomed and accustomed exercise on the immune response in runners

Purpose: To test the hypothesis that long-term immunological response may be different after accustomed concentric and unaccustomed eccentric exercise in endurance-trained men. Methods: Fourteen highly endurance-trained male runners performed two bouts of high-intensity exercise with at least 2-wk intervals between bouts. Concentric exercise consisted of a 60-min level run with a targeted heart rate of 80% V̇O_2peak. Eccentric exercise was conducted lying on a specially designed exercise rack, eliciting eccentric action of the musculus quadriceps femoris. Blood samples were taken before and 1, 6, 24, 72, and 144 h after exercise to determine creatine kinase (CK), C-reactive protein (CRP), and interleukin-6 (IL-6). Lymphocyte subset distribution was assessed using flow cytometry. Results: We found a significant (P < 0.05) increase of CD4⁺ (eccentric: 17%; concentric: 20%), CD3⁺/CD4⁺ (16 vs 19%), CD25⁺ (45 vs 29%), CD25⁺/CD4⁺ (27 vs 50%), HLA-DR⁺ (20 vs 15%), HLA-DR⁺/CD4⁺ (16 vs 67%), and CD19⁺/CD45 ⁺ (52 vs 103%) positive lymphocytes 1 h after both exercise bouts. However, eccentric exercise resulted in a significantly higher and longer (6 h) increase of CD25⁺/CD4⁺ and HLA-DR⁺/CD8 ⁺ lymphocytes and a peak increase of CK at 72 h. IL-6 and CRP increased only after concentric exercise within the first 24 h. Both exercises resulted in a decrease of monocyte activation (LFA-1: CD18⁺/ CD11a⁺) after 6 h, with an increase for the eccentric exercise part after 24 h (P < 0.05). Conclusion: Accustomed concentric exercise mainly induced an acute-phase response, with increased CRP, IL-6, and activation of CD4⁺ lymphocyte subsets. Unaccustomed eccentric exercise provided a delayed increase in CK and activation of monocytes and CD4⁺ and CD8⁺ subsets. Therefore, the immunological reaction depends not only on the type of contraction but also on the adaptation to the exercise.