Are health- and skill-related truly separate components of physical fitness in youth?

Abstract Purpose The present study aims to examine whether various physical fitness measures form a single unified or a multidimensional construct in children and adolescents, utilizing the PROESP-BR surveillance database, which encompasses over 20 years of data. Methods Cross-sectional data from 61,460 Brazilian youth (6–18 years) were analyzed. Z-scores were calculated for seven fitness components: abdominal endurance, agility (change-of-direction speed), cardiorespiratory fitness, flexibility, speed, and lower and upper limb power. Dimensionality was examined using exploratory graph analysis (EGA), confirmatory factor analysis (CFA), and multigroup invariance testing across sex and maturity offset groups. Results EGA revealed a unidimensional structure, consistently replicated through bootstrapping. CFA confirmed this structure (CFI/TLI ≥ 0.96; SRMR/RMSEA ≤ 0.044). Multigroup CFA supported configural, metric, and scalar invariance across sexes and maturity offset groups. When a two-factor model was tested, five of seven fitness measures continued to load on a single latent construct. However, the two latent factors shared more variance than they retained uniquely ( R 2 = 0.612), supporting a single-factor solution interpretation of overall physical fitness. Conclusion Physical fitness in youth appears to be best conceptualized as a unified construct rather than distinct health- and skill-related domains. These findings challenge traditional classifications and support a more integrated approach to fitness assessment and promotion in youth.