Cardiorespiratory fitness (CRF) reflects the integrated ability to deliver oxygen from the atmosphere to the skeletal muscles and to utilize it to generate energy to support muscle activity during exercise. Peak oxygen uptake (VO2) is internationally recognized as the criterion measure of youth CRF. It is well-documented that in youth peak VO2 increases with sex-specific, concurrent changes in a range of age- and maturity status-driven morphological and physiological covariates with the timing and tempo of changes specific to individuals. However, a recent resurgence of interest in predicting peak VO2 from field test performances and the persistence of fallacious interpretations of peak VO2 in 1:1 ratio with body mass have obfuscated general understanding of the development of CRF. Moreover, as spurious relationships arise when ratio-scaled data are correlated with health-related variables the use of this scaling technique has confounded the relationship of youth CRF with indicators of current and future health. This paper reviews the extant evidence and concludes that the interpretation of youth CRF and the promotion of young people’s health and well-being should be founded on scientific facts and not on fictions based on flawed methodology and specious interpretation of data.
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