Echocardiographic study of cardiac dimensions and function in the endurance-trained athlete

Adaptive cardiac responses to isotonic training were studied with echocardiographic measurement of cardiac dimensions and function in 20 endurance runners whose maximal aerobic capacity on the treadmill was 4.88 ± 0.13 (mean standard error of mean) liters of oxygen/min. They were compared with 26 young sedentary control subjects whose capacity was 3.34 ± 0.11 liters of oxygen/min (P < 0.001). A modest degree of right and left ventricular chamber enlargement and left ventricular hypertrophy was observed in endurance runners (left ventricular mass index 140 ± 6 g/m² compared with 107 ± 4 g/m² in sedentary control subjects, (P < 0.001). Resting heart rate was slower in endurance runners (51 ±2 versus 62 ±2 beats/min, P < 0.001) and resting left ventricular function as evaluated with ejection fraction and maximal posterior wall shortening velocity and mean circumferential shortening velocity (V_CF) was comparable or slightly depressed in endurance runners (0.98 ± 0.03 versus 1.02 ± 0.05 circumferences/sec [difference not significant]). This study suggests that isotonic training results in adaptive changes in ventricular volume and mass, slower heart rates that may be associated with more efficient pumping function (that is, increasing stroke volume) and insignificant alterations in resting ejection phase indexes of left ventricular function.