The influence of heart rate on echocardiographic assessment of aerobic training

The purpose of this investigation was to determine if echocardiographic measures of ventricular structure and function ascribed to aerobic training might be an artifact of heart rate (HR) differences between trained and untrained subjects. Comparisons were made at rest, of 10 young, male, aerobically well‐trained athletes [((VO2)max 65>ml/kg/min] and 10 young, healthy controls [((VO2)max<56ml/kg/min]. Additionally, the echocardiographic responses to low (HR=80 beats/min) and moderate intensity (HR=120 beats/min) supine cycling exercise were analyzed. Echocardiographic measures were made as described by Sahnet al. (1978). Results of echocardiographic comparisons between groups, both during supine rest and at a constant heart rate of 80 beats/min during supine cycling confirmed that athletes had significantly greater left ventricular mass (LV mass) and end‐diastolic size per square meter of body surface area (p<0.05). When supine cycling loads were increased to elevate HR to 120 beats/min in groups of 7 athletes and 5 controls, athletes exhibited a progressive and significant (p<0.05) enlargement of left ventricular end‐diastolic size (LVEDS), while left ventricular end‐systolic size (LVESS) showed negligible change. The control group showed little change in LVEDS, but decreased LVESS significantly (p<0.05). Contractility measures, i.e., estimated ejection fraction (EF) and velocity of circumferential shortening ( (Vcf) increased in both groups in a similar manner. It was concluded that echocardiographic differences in ventricular structure and function observed between aerobically trained and untrained subjects are not an artifact of heart rate differences. Clearly, aerobic training results in increased LV mass and diastolic size which allows for further dilitation with supine exercise. Aerobic training does not appear to alter indices of myocardial contractility.