Prediction of maximal oxygen uptake by bioelectrical impedance analysis in overweight adolescents.

Aim. Maximal oxygen uptake (VO 2max ), the gold standard for measurement of cardiorespiratory fitness, is frequently difficult to assess in overweight individuals due to physical limitations. Reactance and resistance measures obtained from bioelectrical impedance analysis (BIA) have been suggested as easily obtainable predictors of cardiorespiratory fitness, but the accuracy with which ht 2 /Z can predict VO 2max has not previously been examined in overweight adolescents. Methods. The impedance index was used as a predictor of VO 2max in 87 overweight girls and 47 overweight boys ages 12 to 17 with mean BMI of 38.6±7.3 and 42.5±8.2 in girls and boys respectively. The Bland Altman procedure assessed agreement between predicted and actual VO 2max˙ Results. Predicted VO 2max was significantly correlated with measured VO 2max (r 2 =0.48, P<0.0001). Using the Bland Altman procedure, there was significant magnitude bias (r 2 =0.10; P<0.002). The limits of agreement for predicted relative to actual VO 2max were -589 to 574 mL O 2 /min. Conclusion. The impedance index was highly correlated with VO 2max in overweight adolescents. However, using BIA data to predict maximal oxygen uptake over-predicted VO 2max at low levels of oxygen consumption and under-predicted VO 2max at high levels of oxygen consumption. This magnitude bias, along with the large limits of agreement of BIA-derived predicted VO 2max , limit its usefulness in the clinical setting for overweight adolescents.