ESTROGEN REPLACEMENT INFLUENCES PEAK CARDIAC OUTPUT IN EXERCISE TRAINED POSTMENOPAUSAL WOMEN 1009

Abstract

The purpose of this study was to determine if peak cardiac output in exercise trained postmenopausal women is affected by estrogen replacement. Subjects were 22 women between 3 and 10 years past menopause who engaged in endurance exercise at least 3 times per week form more than a year. Twelve subjects had been taking estrogen replacement for at least a year (E) while 10 had never taken estrogen replacement (NE). There were no significant differences between groups in frequency, intensity, or duration of training bouts. O2 consumption and sub-maximal cardiac output was assessed using open circuit expired gas analysis and the DeFares CO2 rebreathing paradigm. Peak cardiac output (QMAXL/min) and cardiac index(QMAXIL/min/m2) were calculated by regressing sub-maximal cardiac output values on corresponding O2 consumptions, then extrapolating to the peak O2 consumption value (PVO2L/min). The mean R2 value for these regressions was.92 (sd=.08). Peak heart rate(PHR) was assessed with ECG, and peak arteriovenous oxygen difference(PAVO2Dml/L) and peak stroke volume index (PSVIL/m2) were calculated using the Fick equation. Plasma estradiol (E2pg/ml) was assessed using radioimmunoassay. All data were analyzed using analysis of variance. Table QMAXI and PSVI were higher in the E group while PAVO2D was lower. It was concluded that estrogen replacement may play a role in facilitating a training induced increase in maximum cardiac output in postmenopausal women.