Background: Arterial stiffness, wave reflections, endothelial dysfunction and carotid intima-media thickness (cIMT) are predictors of cardiovascular events. Marathon running is an extremely vigorous aerobic exercise.

Methods: We enrolled 3 groups of regularly-trained marathon runners and 3 groups of matched recreationally-active controls. Aortic stiffness was evaluated with carotid-femoral pulse wave velocity (PWV), wave reflections with augmentation index (AIx), endothelial function with flow-mediated dilation (FMD) and nitroglycerine-mediated dilatation (NMD) of the brachial artery and early atherosclerosis with cIMT. PWV was studied in 49 runners (trained for 11.6±9.1 years) and 46 controls. IMT was measured in 36 runners (trained for 13.1±9.5 years) and 19 controls. FMD and NMD were assessed in 21 runners (trained for 14.5±8.5 years) and 17 controls.

Results: Marathon runners had significantly higher systolic, diastolic, pulse (aortic and brachial) and mean pressures (P<0.05 for all) and higher PWV compared to controls (6.89±1.0m/s vs. 6.33±1.03m/s, P<0.01). Athletes exhibited lower cIMT (0.58±0.10mm vs 0.63±0.80mm, P<0.05) and higher FMD (8.59±4.1% vs 6.25±1.6%, P<0.05). AIx, AIx@75 and NMD did not differ.

Conclusion: While marathon runners have higher FMD and decreased IMT compared to controls, indicating better endothelial function and lower subclinical atherosclerosis, they also have increased PWV. Increased aortic stiffness may be the result of elastic component damage due to excessive exercise burden; however, it may also represent an adaptive process that leads to a higher, but favorable -for this type of running- travel for waves, and possibly relates to why marathon runners reach their peak later in life compared to other athletes.