Importance of proper scaling of aerobic power when relating to cardiometabolic risk factors in children

Background: The relationship between cardiometabolic risk factors (CMRF) and aerobic power (VO _2max) scaled as mL O2 per kilogram body mass is controversial because mass includes both fat and fat-free mass, and fat mass is independently associated with the CMRF. Aim: To examine common units used to scale VO _2max and their relationships to mean blood pressure (MBP), total cholesterol (TC), HDL cholesterol, triglycerides (TG), insulin resistance (HOMA-IR) and cumulative risk score (z-score). Subjects: 1784, 8-18 year-old youths, 938 girls and 886 boys. Methods: Fasting blood samples were obtained. VO _2max was estimated in mL/min from cycle ergometry and scaled to body mass (kg), fat free mass (kgFFM), body surface area (m ²), height (cm) and allometric (mL/kg ^0.67/min). Results: Unadjusted correlations between CMRF and many of the scaled VO _2max units were significant (p < 0.0001), especially for MBP, HOMA-IR, HDL and z-score, with lower correlations for TC and TG. After adjusting for ancestry, sex, height and body fat associations were greatly weakened (r < 0.09), except for MBP. Conclusions: On a population basis, the physical characteristics of the child, especially body fat, are more related to CMRF than any scaled units of VO _2max; thus care is needed when relating fitness and health issues.