Abstract
BACKGROUND: Cardiorespiratory fitness (CRF) is a vital indicator of health. However, accurately measuring peak oxygen consumption ( V˙ O(2peak)) to determine CRF in children can be challenging. The oxygen uptake efficiency slope (OUES) has been proposed as an alternative metric for predicting V˙ O(2peak) in children, but its accuracy and agreement with measured V˙ O(2peak) remain unclear. METHODS: A post hoc analysis was conducted in 94 children (ages 7-10 years) who completed an incremental cycle ergometer test to measure V˙ O(2peak). Body composition (Dual-energy X-ray absorptiometry) was measured, and fat mass index (FMI, kg/m(2)) and fat-free mass index (FFMI, kg/m(2)) were calculated. OUES was determined using all respiratory data (OUES(100%)) collected during the cycle ergometer test and using data only up to 60% of heart rate reserve (OUES(60%HRR)). Regression equations to predict V˙ O(2peak) (Pred- V˙ O(2peak)) were derived from simple and multiple linear regression analysis. Bland-Altman analysis assessed the level of agreement between Pred- V˙ O(2peak) and measured V˙ O(2peak). RESULTS: OUES(60%HRR) (β = 0.46, p < 0.0001), age (β = 56.0, p = 0.0004), White race (β = 173.3, p < 0.0003), FFMI (β = 0.98.6, p < 0.000), and FMI (β = -0.40.8, p < 0.000) were retained in the final model. The difference between measured V˙ O(2peak) and Pred- V˙ O(2peak) was not different from zero (p = 0.999). There was a positive association between the difference of measured V˙ O(2peak) and Pred- V˙ O(2peak) and the average of the two methods (β = 0.79, p = 0.0028). CONCLUSION: There was no mean bias between measured V˙ O(2peak) and Pred- V˙ O(2peak). However, magnitude bias was present even after considering other significant predictors of V˙ O(2peak) (FMI, FFMI, race, and age) in the regression equation. Caution is advised when using OUES to predict V˙ O(2peak) in children.