Exercise-induced differences in cardiac output, blood pressure, and systemic vascular resistance in a healthy biracial population of 10-year-old boys.

Previous studies have documented systolic blood pressure differences in response to dynamic exercise when blacks were compared with whites. This study was performed to validate these data and to determine if the cardiac output and systemic vascular resistance responses to exercise are different in a biracial population of 10-year-old boys. Nineteen blacks and 31 whites underwent maximum supine graded exercise tests with Doppler determination of cardiac output and measurement of systolic and diastolic blood pressure and systemic vascular resistance. The blacks had a body surface area that was marginally larger than that of the whites, but no differences were noted in height or weight. Working capacities, when indexed by weight, were virtually identical between the two groups. No differences were noted in either systolic or diastolic blood pressure during preexercise, maximum exercise, or early and late recovery. White males had significantly higher cardiac indexes during preexercise, maximum exercise, and early and late recovery. Black males had greater systemic vascular resistance during preexercise, maximum exercise, and early and late recovery. Thus, the black children's blood pressure responses to exercise were comparable with those of the white children but they had a greater systemic vascular resistance and lower cardiac index. These racial differences may serve as potential markers for the prehypertensive state.