Background: Physical activity is associated with a lower risk of cardiovascular disease but the mechanism underlying this association is unclear. These benefits of physical activity might result from its effects on inflammation and endothelial function.

Aim: We investigated whether cardiorespiratory fitness and the level of physical activity are associated with biomarkers of atherosclerosis in athletes and nonathletes.

Methods: Forty six athletes and 46 age- and sex-matched subjects who did not exercise regularly were studied. All subjects underwent anthropometric measurements and maximal treadmill cardiopulmonary exercise tests. Physical activity level was assessed using the International Physical Activity Questionnaire-Short Form (IPAQ-SF). Blood samples were taken before and immediately after exercise. Serum interleukin (IL)-6, soluble CD40 ligand (sCD40L) and soluble intercellular adhesion molecule- 1 (sICAM-1) levels were determined using the ELISA method.

Results: In all participants, IL-6 level was significantly increased after exercise as compared to baseline (1.35 ± 2.6 vs. 1.46 ± ± 2.1 pg/mL, p = 0.01). Resting IL-6 and sCD40L levels were lower in athletes as compared to nonathletes (0.7 ± 0.92 vs. 1.8 ± 3.52 pg/mL, p = 0.003, and 888.8 ± 892.9 vs. 2367.7 ± 8743.4 pg/mL, p = 0.005, respectively), while sICAM-1 levels did not differ between the two groups. IL-6 level correlated negatively with peak oxygen consumption (r = –0.25, p = 0.035) and the IPAQ-SF score (r = –0.26, p = 0.02), and sCD40L level correlated negatively with the IPAQ-SF score (r = –0.4, p = 0.004). Conclusions: Intensive exercise training and high exercise capacity are associated with lower serum IL-6 and sCD40L levels. This may constitute an important factor limiting progression of atherosclerosis.