Although the underlying mechanisms responsible for cardiac dysfunction after prolonged exercise remains to be elucidated, it has reported cardiac deterioration following exhaustive exercise in the absence of underlying cardiovascular diseases, which has been attributed to cardiac fatigue. The objective of this study was to evaluate cardiac functions, exercise capacity, and flow-mediated dilatation in overreaching syndrome. We studied 13 male marathon runners who took part in a marathon. Cardiopulmonary exercise testing, transthoracic echocardiography and endothelium-dependent vasodilatation of the brachial artery were performed at before- and after-race. Peak oxygen consumption, left ventricular tissue Doppler imaging parameters and flow-mediated dilatation were decreased after-race values compared with before- race values. Overreaching syndrome could arise involves a physio-pathological trivest, cardio-vasculo-muscular axis, which include three vicious cycles. (C) 2007 Published by Elsevier Ireland Ltd.