CARDIOVASCULAR REACTIVITY, PHYSICAL ACTIVITY, AND METABOLIC SYNDROME IN YOUTH

Y.I. Coil 1, M. E. Holmes 1, J. C. Eisenmann 1; Iowa State University, Ames, IA

1 Michigan State University, East Lansing, MI

BACKGROUND: Metabolic syndrome (MetS) in U.S. adolescents has become an important public health issue in the last decade. Physical activity and diet are often associated with the MetS phenotype; however, stress and stress reactivity may also contribute to the MetS. These contributions have been shown in adults, but further etiological studies to examine MetS in youth are necessary.

PURPOSE: The purpose of this study was to provide preliminary data on the relationships between physical activity, cardiovascular reactivity to physical stress, and the MetS in 8-18 year old boys (n=37). Specifically, we examined whether the relationship between physical stress and MetS was modified by level of moderate to vigorous physical activity (MVPA).

METHODS: Habitual physical activity was assessed using the MTI Actigraph accelerometer. Cardiovascular response was measured during a stress protocol consisting of a 2 minute 30% maximal effort isometric handgrip challenge (HG) and 1 minute forehead cold pressor test (CPT), Changes in mean arterial pressure (MAP) from baseline to CPT was used as an index of cardiovascular reactivity(CVR). A continuous metabolic syndrome score (MSS) was generated by summing the age-standardized residuals for waist circumference, mean arterial pressure, glycosylated hemoglobin, and high-density lipoprotein-cholesterol.

RESULTS: In the total sample, the correlations between MVPA and CVR (r=-0.24), MVPA and MSS (r=-0.24), and CVR and the MSS (r= -0.19) were low. After separating the group into low, moderate, and high daily MVPA categories, the correlations between CVR and the MSS was r= 0.37 in the low MVPA group, r= 0.13 in the moderate MVPA group, and r= 0.19 in the high MVPA group.

CONCLUSIONS: Results from this preliminary study show evidence that time in MVPA per day may modify the relationship between cardiovascular reactivity and the metabolic syndrome. In particular, CVR was more strongly associated with a higher MSS in youth who engage in fewer minutes of MVPA per day compared to children with moderate to high daily MVPA.

*This work supported by a grant from the Center for Designing Food and Improving Nutrition, Iowa State University-USDA CRESS.