Exercise cardiac contractility in men and boys: a recovery echocardiographic study.

Previous reports have suggested that children possess limited cardiac functional reserve during exercise compared to young adults. In this study, echocardiography was performed immediately after maximal treadmill exercise to measure left ventricular dimensions and shortening fraction (SF) in college men, and these values were compared to previous results in a post-exercise echocardiographic study of prepubertal boys. Post-exercise SF, change in SF from rest, and percent change in SF from rest were all significantly greater in the post-pubertal subjects. In both men and boys changes in SF following exercise were related to reductions in left ventricular end-systolic dimension, with only minor reductions observed in end-diastolic dimension. These findings support the concept that prepubertal subjects may have inferior myocardial function with exercise when compared to young adults.