Diagnostic thresholds of cardiorespiratory fitness for identifying cardiometabolic risk in youth

Cardiorespiratory fitness, measured as peak oxygen uptake (VO₂peak), is a key marker of metabolic health in youth, but age- and sex-specific diagnostic thresholds for identifying elevated cardiometabolic risk (CMR) remain undefined. This study aimed to establish age- and sex-specific VO₂peak cut-points for elevated CMR by (i) conducting a cross-sectional diagnostic analysis that compared the diagnostic accuracy of commonly used VO₂peak estimation equations (Barnett, Léger, Matsuzaka) to select the best-performing index, and (ii) performing a systematic review and meta-analysis to synthesize and validate findings.

To establish diagnostic thresholds of VO₂peak for identifying CMR in youth, we conducted a two-part study. First, a cross-sectional analysis was performed using data from 1059 children aged 8-11 years. Second, a systematic review and meta-analysis were conducted to synthesize evidence from existing observational studies. The literature search included four databases. Eligible studies included cross-sectional or cohort designs with participants aged 3-18 years, and reported cardiorespiratory fitness as VO₂peak along with composite measures of CMR. We included 14 studies comprising a total of 20,780 children and adolescents. Optimal VO₂peak thresholds for identifying elevated CMR were 43.2 mL/kg/min for boys and 41.9 mL/kg/min for girls aged <13 years, and 40.0 mL/kg/min for boys and 38.5 mL/kg/min for girls aged ≥13. These thresholds demonstrated moderate-to-strong diagnostic performance, and corresponded to the 20th-40th percentiles of international normative data.

We report novel age- and sex-specific VO₂peak thresholds for elevated CMR in youth, with good diagnostic performance, to aid early identification and prevention.