Relationships between measures of fitness, physical activity, body composition and vascular function in children

The prevalence of obesity and physical inactivity in Western countries has increased rapidly. Both are modifiable risk factors for cardiovascular disease. Atherosclerosis begins in childhood and endothelial dysfunction is its earliest detectable manifestation.

We assessed flow-mediated dilation (FMD) in 129 children (75 female; 10.3+0.3 yrs; 54 male; 10.4; 0.3 yrs). FMD was normalised for differences in the eliciting shear rate stimulus between subjects (SR(AUC)). Fitness was assessed as peak oxygen uptake during an incremental treadmill exercise test (V O(2)peak). Body composition was measured using a dual-energy X-ray absorptiometry (DEXA) scan. Physical activity (PA) was assessed using Actigraph accelerometers. The cohort was split into tertiles according to FMD% and also FMD% corrected for SR(AUC) to gain insight into the determinants of vascular function.

Across the cohort, significant correlations were observed between FMD%/SR(AUC) and DEXA percentage fat (r=-0.23, p=0.009) and percentage lean mass (r=0.21, p=0.008), and also with PA performed at moderate-to-high intensity (r=0.363, p=0.001). For children in the lowest FMD%/SR(AUC) tertile, a stronger relationship with all PA measures was observed, particularly with high intensity PA (r=0.572, P=0.003). Regression analysis revealed that high intensity PA was the only predictor of impaired FMD%/SR(AUC).

These data suggest that traditional risk factors for CHD in adult populations impact upon vascular function in young people. Furthermore, it appears that individuals with impaired FMD may benefit from performing high intensity PA, whereas no relationships exist between FMD and lower intensities of PA or between PA and FMD in those subjects who possess preserved vascular function a priori.