LEFT-VENTRICULAR FUNCTION IN TRAINED AND UNTRAINED HEALTHY-SUBJECTS

Left ventricular function was compared in 18 normal sedentary controls (mean age 28 yr, range 22-34 yr) and 9 endurance-trained athletes (mean age 19 yr, range 15-25 yr) at rest and during supine bicycle exercise. Gated radionuclide angiocardiograms were performed at rest and at each level of graded maximal supine bicycle exercise. Heart rate, blood pressure, left ventricular ejection fraction and the relative changes in left ventricular end-diastolic and end-systolic volumes were assessed. Athletes attained a much greater work load than controls (mean 22.1 kpm[kilopound meter]/kg body wt vs. 13 kpm/kg body wt). Both groups achieved similar increases in heart rate, blood pressure and ejection fractions. In the controls, the mean end-diastolic volume increased to 124% of that at rest (P < 0.02) during exercise and the mean end-systolic volume decreased to 81% of the rest level (P < 0.02). The mean end-diastolic volume did not significantly change during exercise in the athletes, and the mean end-systolic volume decreased to 64% of rest (P < 0.05). Although trained and untrained healthy subjects had similar increases in the left ventricular ejection fraction during exercise, different mechanisms were used to achieve these increases. Untrained subjects increased end-diastolic volumes while trained subjects decreased the end-systolic volumes. The ability of athletes to exercise without increasing preload may be an effect of training and might have important implications in reducing myocardial O2 demand during exercise.