Abstract

To determine whether endurance exercise training can improve left ventricular function in response to beta-adrenergic stimulation young healthy sedentary subjects were studied before and after 12 wk of endurance exercise training. Left ventricular function was evaluated by two-dimensional echocardiography under basal conditions and during beta-adrenergic stimulation induced by isoproterenol infusion. Fractional shortening (FS) under basal conditions was unchanged after training. At comparable changes in end-systolic wall stress (d-es), the increase in FS induced by isoproterenol was significantly larger after training. Furthermore there was a greater decrease in end-systolic dimension at similar changes in d-es in the trained state during isoproterenol infusion. There were no concurrent changes in end-diastolic dimension between the trained and untrained states during isoproterenol infusion, suggesting no significant changes in preload at comparable levels of d-es. Under basal conditions, end-diastolic dimension was increased after training, with no significant change in left ventricular wall thickness-to-radius ratio after training, consistent with volume-overload hypertrophy. The results indicate that endurance exercise training enhances the left ventricular contractile response to beta-adrenergic stimulation without affecting basal contractility in young subjects. Verf.-Referat