RESUMEN
PURPOSE: Poor cardiorespiratory fitness is associated with increased all cause morbidity and mortality. In children with obesity, maximum oxygen uptake (VÌO2max) may not be achieved due to reduced motivation and peripheral fatigue. We aimed to identify a valid submaximal surrogate for VÌO2max in children with obesity. METHOD: Ninety-two children with obesity (7-16 years) completed a maximal exercise treadmill test and entered a three-month exercise and/or nutrition intervention after which the exercise test was repeated (n = 63). Participants were required to reach VÌO2max to be included in this analysis (n = 32 at baseline and n = 13 at both time-points). The oxygen uptake efficiency slope (OUES) was determined as the slope of the line when VÌO2 (L/min) was plotted against log VÌE. Associations between the maximal OUES, submaximal OUES (at 3, 4, 5 and 6 min of the exercise test) and VÌO2max were calculated. RESULTS: In the cross-sectional analysis, VÌO2max (L/min) was strongly correlated with 5-min OUES independent of Tanner puberty stage and sex (R2 = .80, p < .001). Longitudinal changes in VÌO2max were closely reflected by changes in 5-min OUES independent of change in percent body fat (R2 = .63, p < .05). CONCLUSION: The 5-min OUES is a viable alternative to VÌO2max when assessing children with obesity.