Left ventricular performance of the athletic heart during upright exercise: A heart: Rate-controlled study

RUBAL. B.J., J.M. MOODY, S. DAMORE, S.R. BUNKER, AND N.M. DIAZ. Left ventricular performance of the athletic heard during exercise: A heard rate-controlled study. Med. Sci. Sports. Exerc., Vol. 18. No. 1. pp.134-140, 1986. This study compares the left ventricular performance of chronically conditioned pentathletes(N = 10) with less-conditioned subjects (N = 10) during dynamic upright exercise. The pentathletes were found to have a superior treadmill performance [24 ±4 vs 17 ± 2 min (SD), P < 0.01], reduced resting heart rate (41 ±13 vs 62 plus;6 bpm, P <0.01), and increased left ventricular mass (254 ±85 vs 179 ±35 g, P <0.05) compared to the control group. Radionuclide ventriculography and heart rate controlled-bicycle ergometry were employed to examine changes in left ventricular ejection fraction, end-diastolic volume, end-systolic volume, arid stroke volume. Heart rate was controlled by adjusting the resistance of the ergometer until stable heart rates of 90, 110, 130, and 150 bpm were achieved. Following heart rate stabilization,^99mTc images were acquired during 3-min stages at each target heart rate level. In the pentathletes, left ventricular ejection fraction, end-diastolic volume, and stroke volume increased (P <0.01) during exercise, and end-systolic volume tended to decrease. No difference was noted in left ventricular ejection fraction between groups when heart rates were matched. However, the exercise-induced changes in end-diastolic volume and stroke volume were greater (P <0.01) in the pentathletes. In conclusion, the athletes studied relied on the same mechanism as the less-conditioned subjects for improving pump performance during exercise stress, but the athletes' ability to mobilize a greater end-diastolic volume accounts for their larger stroke output during each stage of heart rate-matched exercise.