Impact of Scaling Peak Oxygen Uptake for Body Size and Composition to Assess Cardiometabolic Risk in Children.

Purpose: This study measured associations of peak oxygen uptake (V̇O2peak) with cardiometabolic risk factors and quantified cardiometabolic risk misclassification when scaling V̇O2peak for body size and composition, comparing population-specific and universal V̇O2peak cut-points.

Methods: In a population sample of 332 Finnish children (164 girls, 9-11 years), V̇O2peak was determined using a maximal cycle ergometer test and scaled for body mass (BM) and lean mass (LM) using ratio and allometric methods. A continuous cardiometabolic risk score was calculated from age- and sex-specific z-scores of traditional risk factors, with 'increased risk' defined as ≥1 standard deviation above the mean. Receiver operating characteristics curves assessed the ability of V̇O2peak to classify children at increased risk. Associations between V̇O2peak and cardiometabolic risk factors were measured using linear regression analyses. The type and extent of misclassification were calculated by comparing rank differences between allometric and ratio-scaled V̇O2peak, using directly measured cardiometabolic risk vs. V̇O2peak cut-points. Population-specific cut-points based on previously reported cut-points in this sample were compared with universal cut-points from existing meta-analyses.

Results: Scaling using LM, or allometric methods, attenuated associations between V̇O2peak and cardiometabolic risk factors. V̇O2peak scaled by LM-1, BM-0.49, or LM-1.04 demonstrated poor ability to classify increased cardiometabolic risk, whilst V̇O2peak scaled by BM-1 had the highest classification ability in girls and boys (AUC = 0.875 and 0.690 respectively, p < 0.01). Universal cut-points produced fewer false positive classifications than population-specific cut-points.

Conclusions: V̇O2peak appropriately scaled for body size and composition may have limited ability to distinguish cardiometabolic risk in children, with diminished associations with cardiometabolic risk factors. Screening for cardiometabolic risk in children using V̇O2peak ratio-scaled by BM may reflect body size, rather than fitness.