Adaptations in β-adrenergic cardiovascular responses to training in older women

To determine whether endurance exercise training can alter the β-adrenergic-stimulated inotropic response in older women, we studied 10 postmenopausal healthy women (65.4 ± 0.9 yr old) who exercised for 11 mo. Left ventricular (LV) function was evaluated with two-dimensional echocardiography during infusion of isoproterenol after atropine. Maximal O₂ consumption increased 23% in response to training (from 1.35 ± 0.06 to 1.66 ± 0.07 l/min; P = 0.004). Training had no effect on baseline LV function, end-diastolic diameter, LV wall thickness, or LV mass. The increase in LV systolic function in response to isoproterenol was unaffected by training. Furthermore, neither the systolic shortening-to-end-systolic wall stress relationship nor the end-systolic wall stress-to-end-systolic diameter relationship during isoproterenol infusion changed with training. We conclude that older postmenopausal women can increase their maximal O₂ consumption with exercise training without eccentric LV hypertrophy or enhancement of β-adrenergic-mediated LV contractile function. These observations provide an explanation for the finding that maximal cardiac output and stroke volume are not increased in older women in response to training.