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Nicholas M. Edwards, Heidi J. Kalkwarf, Jessica G. Woo, Philip R. Khoury, Stephen R. Daniels and Elaine M. Urbina

Purpose:

The objective of this study was to characterize the relationship between objectively-measured physical activity (PA) and cardiovascular risk factors in 7-year-old children and test the hypothesis that it differs by race.

Methods:

Cross-sectional study of 308 7-year-old children drawn from a major US metropolitan community. PA (moderate-to-vigorous, MVPA; light, LPA; and inactivity, IA) was measured by accelerometry (RT3). Cardiovascular risk factors included BMI, blood pressure, and serum lipids, glucose and insulin concentrations. General linear modeling was used to evaluate the independent associations between PA measures and cardiovascular risk factors and interactions by race.

Results:

In black children, greater time spent in PA was independently associated with lower levels of triglycerides (MVPA and LPA, both p < .01), glucose (MVPA, p < .05), and insulin (MVPA, p < .01); these associations were not evident in white children. Across races, greater inactivity was independently associated with greater low-density lipoprotein cholesterol in overweight participants (p < .01) but not in normal weight participants. No PA measure was associated with BMI, systolic blood pressure, or high-density lipoprotein cholesterol.

Conclusions:

In this cohort of 7-year-old children, the relationship between PA and some cardiovascular risk factors differed by race. These findings may have implications for targeting of PA promotion efforts in children.

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Samuel G. Wittekind, Nicholas M. Edwards, Philip R. Khoury, Connie E. McCoy, Lawrence M. Dolan, Thomas R. Kimball and Elaine M. Urbina

Background: We aimed to (1) compare a subjective and objective measure of habitual physical activity (PA), (2) determine the association of PA and cardiovascular risk factors, and (3) test the hypothesis that PA is an independent determinant of target organ damage in youth. Methods: Cross-sectional analysis of youth with and without type 2 diabetes [mean age = 22 (3.9) y]. PA was measured with International Physical Activity Questionnaire and Actical accelerometer. Target organ damage was assessed with echocardiography and peripheral arterial testing. Subjects were stratified into tertiles of total PA, and differences were tested by analysis of variance and χ2 tests. General linear models tested for independent associations. Results: The correlation between International Physical Activity Questionnaire and accelerometry was weak (r = .23, P = .0003). Less active subjects had worse cardiovascular risk profiles and target organ damage, including stiffer arteries (P < .01). These outcome differences did not reach statistical significance when adjusted for covariates, such as lipid levels and glycemic control. Conclusion: Survey assessment of PA is complicated by inaccurate reporting. There is a strong association of habitual PA with cardiovascular risk factor clustering. PA may exert its beneficial effect on arterial stiffness in obese youth through improved glycemic control.