Comparison of different VO2max equations in the ability to discriminate the metabolic risk in Portuguese adolescents

There is increasing evidence that cardiorespiratory fitness (CRF) is an important health marker already in youth. This study aimed to determine the ability of five VO2max equations to discriminate between low/high Metabolic Risk in 450 Portuguese adolescents aged 10–18. We measured waist and hip circumferences, fasting glucose, total cholesterol, HDL-cholesterol, LDL-cholesterol, triglycerides, and blood pressure. For each of these variables, a Z-score was computed. The HDL-cholesterol was multiplied by −1. A metabolic risk score was constructed by summing the Z scores of all individual risk factors. High risk was considered when the individual had ≥1 SD of this score. Cardiorespiratory fitness (CRF) was measured with the 20-m shuttle run test. We estimated VO2max from the CRF tests using five equations. ROC analyses showed a significant discriminatory accuracy for the Matsuzaka and Barnett(a) equations in identifying the low/high metabolic risk in both genders (Matsuzaka girls: AUC = 0.654, 95%CI: 0.591–0.713, p < 0.001, VO2max = 39.5 mL kg−1 min−1; boys: AUC = 0.648, 95%CI: 0.576–0.716, p < 0.001, VO2max = 41.8 mL kg−1 min−1; Barnett(a) girls: AUC = 0.620, 95%CI: 0.557–0.681, p < 0.001, VO2max = 46.4 mL kg−1 min−1; boys: AUC = 0.628, 95%CI: 0.555–0.697, p = 0.04, VO2max = 42.6 mL kg−1 min−1), and the Ruiz equation in boys (AUC = 0.638, 95%CI: 0.565–0.706, p < 0.001, VO2max = 47.1 mL kg−1 min−1). The VO2max values found require further testing in other populations as well as in longitudinal studies; the identification of adolescents who have low CRF levels can help detect youth with an increased risk of metabolic disease.