Accuracy of physical working capacity (PWC170) in estimating aerobic fitness in children

Physical working capacity, the workload at a heart rate of 170 bpm (PWC170), has been utilized as a marker of maximal oxygen uptake. The precision of PWC170 in predicting VO2max in children has not been fully evaluated. In this study, 35 children (18 boys and 17 girls, mean ages 10.5 and 9.9 years, respectively) underwent maximal cycle testing to assess the relationship between VO2max and PWC170. These measures correlated closely in absolute terms (r = 0.71 and 0.70 for girls and boys, respectively), but the relationship was weaker when both were expressed per kg body weight (r = 0.65 and 0.48, respectively). When VO2max was calculated from the regression equation of VO2max versus PWC170, the mean error from measured VO2max was 3.4 ml.kg-1.min-1 (SD 2.5) for the girls and 2.8 ml.kg-1.min-1 (SD 2.6) for the boys. These findings indicate that although mean predictability of VO2max from PWC170 is good, the variability is wide, with a 10-15% error at one standard deviation. PWC170 provides only a crude estimate of VO2max and should not be used to predict individual maximal aerobic power.