Running title: Cardiovascular function after the London Marathon

ABSTRACT Prolonged exercise has been shown to result in an acute depression in cardiac function. However, little is known about the effect of this type of exercise on vascular function. Therefore, the purpose of the present study was to investigate the impact of an acute bout of prolonged strenuous exercise on vascular and cardiac function and the appearance of biomarkers of cardiomyocyte damage, in 15 male (32±10 years) non-elite runners. The subjects were tested on two occasions, the day before and within an hour of finishing, the London marathon (229±38 min). Function of the brachial and femoral arteries was determined using flow mediated dilatation (FMD). Echocardiographic assessment of cardiac strain, strain rate, tissue velocities and flow velocities during diastole and systole were also obtained. Venous blood samples were taken for later assessment of cardiac troponin I (cTnI), a biomarker of cardiomyocyte damage. Completion of the marathon resulted in a depression in femoral (