The Menopause Alters Aerobic Adaptations to High-Intensity Interval Training

Introduction Postmenopausal women have lower resting cardiac function than premenopausal women, but whether the menopause influences maximal cardiac output and hence exercise capacity is unclear. It is possible that premenopausal and postmenopausal women achieve similar improvements in maximal aerobic capacity (V˙O2max) and cardiac output with exercise training via different regional left ventricular muscle function ("LV mechanics"), as suggested by in vitro and animal studies. The aim of this study was to investigate the effects of the menopause on LV mechanics and adaptations to exercise training. Methods Twenty-five healthy untrained middle-age women (age, 45-58 yr; 11 premenopausal, 14 postmenopausal) completed 12 wk of exercise training. Before and after exercise training, (i) V˙O2max and blood volume were determined, and (ii) LV mechanics were assessed using echocardiography at rest and during two submaximal physiological tests-lower-body negative pressure and supine cycling. Results The increase in V˙O2max after exercise training was 9% smaller in postmenopausal than premenopausal women, concomitant with a smaller increase in blood volume (P < 0.05). However, cardiac output and LV volumes were not different between premenopausal and postmenopausal women (P > 0.05) despite altered regional LV muscle function, as indicated by higher basal mechanics in premenopausal women during the physiological tests after exercise training (P < 0.05). Conclusions These findings are the first to confirm altered LV mechanics in postmenopausal women. In addition, the reduced aerobic adaptability to exercise training in postmenopausal women does not appear to be a central cardiac limitation and may be due to altered blood volume distribution and lower peripheral adaptations.