Scope: Currently there are several reference values for evaluating cardiorespiratory fitness in children. However, one of the most commonly used reference model seems to overestimate normal exercise capacity. We aimed to compare the reference values of peak VO2 between the Bongers model and the newly published Z-score model on a population of children and adolescents referred for CPET.

Methodology: This is a cohort study including 195 healthy young people with exercise symptoms as well as children with different pathologies. All included subjects completed CPET on a bicycle according to a standard protocol. Their exercise values were recorded and the predicted peak VO2 values were compared using the two methods using Bland-Altman, one-sample t-test, linear regression, Welch’s t-test and Chi-2.

Findings: Subjects were aged 14.1 ± 0.6 years. The predicted values between Bongers and the z-score model were not consistent. The Z-score model seems to better estimate the predicted value of our population, since the difference between observed and predicted VO2 was smaller than according to the Bongers model, whether in the entire cohort (-258.2 ± 402.2 vs. -559.7 ± 536.7 mL/min) or in healthy children (-393.6 ± 337.5 vs. -685.3 ± 415.8 mL/min).

Conclusions: The new Z-score model seems to better predict normal CRF in our population of healthy children and in children with various conditions than the Bongers model. This new equation was developed from three populations from different countries and with a wide diversity of ages and BMI, making it applicable to a more heterogeneous population.

Limitations: Our subjects without known condition were referred to us for exercise symptoms. We cannot therefore consider them as healthy in “strictu sensu”. However, as they all had a normal cardiological examination, we had considered them as healthy.