The proposed project has the long-term objective of elucidating the relationship between physical activity and cardiovascular health in children varying in ethnicity, gender and health status. There are two specific aims. The first is to test the hypothesis that controlled physical training (PT) will reduce blood pressure, at rest and in reaction to forehead cold and exercise stressors, in 8-9 year olds who are high in both blood pressure and body fatness. Subjects will be divided equally on gender and pressure and body fatness. Subjects will be divided equally on gender and ethnicity (black/white). Both resting and reactive blood pressure are correlated with left ventricular mass and are predictive of future essential hypertension. The underlying hemodynamic regulators of blood pressure, cardiac output the total peripheral resistance, will be measured with impedance cardiography to explore hemodynamic mechanisms through which training has a favorable influence on blood pressure and left ventricular mass.
The second aim i s to test the hypothesis that physical training will reduce percent body fat, as measured with dual energy x-ray absorptiometry (DEXA). Children above the 70th percentile in both blood pressure and fatness will be randomly assigned, within ethnicity and gender, to a physical training or waiting list control group. After the physical training group undergoes 4 months of training, all subjects will be retested and these data will be used to test the primary hypotheses. The initial control subjects will then perform 4 months of physical training, after which they will be retested. The data from this second phase will be added to the data of the initial physical training group to explore interactions of training with gender and ethnicity. The initial physical training group will be brought back 4 months after cessation of training to see of the changes elicited by the training are reversible. To document the stimulation provided by the training, heart rate will be monitored during training sessions. To observe the time course of changes between the full lab testing sessions, skinfolds and resting blood pressure will be measured monthly. Diet and free living physical activity will be assessed to help explain changes in body composition. Aerobic fitness will be measured with treadmill tests of maximal oxygen consumption.
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