Background-The question of whether training-induced left ventricular hypertrophy in athletes is a physiological rather than a pathophysiological phenomenon remains unresolved. The purpose of the present study was to detect any abnormalities in cardiac function in hypertrophic hearts of elite cyclists and to examine the response of myocardial high-energy phosphate metabolism to high workloads induced by atropine-dobutamine stress. Methods and Results-We studied 21 elite cyclists and 12 healthy control subjects. Left ventricular mass, volume, and function were determined by cine MRI. Myocardial high-energy phosphates were examined by 31 P magnetic resonance spectroscopy. There were no significant differences between cyclists and control subjects for left ventricular ejection fraction (59Ϯ5% versus 61Ϯ4%), left ventricular cardiac index (3.4Ϯ0.4 versus 3.4Ϯ0.4 L ⅐ min Ϫ1 ⅐ m Ϫ2 ), peak early filling rate (562Ϯ93 versus 535Ϯ81 mL/s), peak atrial filling rate (315Ϯ93 versus 333Ϯ65 mL/s), ratio of early and atrial filling volumes (3.0Ϯ1.0 versus 2.6Ϯ0.6), mean acceleration gradient of early filling (5.2Ϯ1.4 versus 5.8Ϯ1.9 L/s 2 ), mean deceleration gradient of early filling(Ϫ3.1Ϯ0.9 versus Ϫ3.2Ϯ0.7 L/s