Sex-Specific Longitudinal Modeling of Youth Peak Oxygen Uptake

Abstract

Purpose: To investigate peak oxygen uptake (VO 2) in relation to sex, age, body mass, fat-free mass (FFM), maturity, and overweight status. Methods: Multiplicative, allometric models of 10-to 18-year-olds were founded on 1057 determinations of peakVO 2 supported by anthropometry and estimates of maturity status. Results: Baseline models with body mass controlled for showed age to exert a positive effect on peakVO 2 , with negative estimates for age 2 , sex, and a sex-by-age interaction. Sexspecific models showed maturity status to have a positive effect on peakVO 2 in addition to the effects of age and body mass. Introducing skinfold thicknesses to provide, with body mass, a surrogate for FFM explained maturity effects and yielded a significantly (P < .05) better statistical fit in all models compared with those based on FFM estimated from youth-specific skinfold equations. With girls only, the introduction of overweight, defined by body mass index, resulted in a small but significant (P < .05) negative effect, with an age-by-overweight status interaction. Conclusions: FFM has a powerful influence on peakVO 2 in both sexes. Interpretation of the development of youth aerobic fitness and its application to health should reflect the sex-and maturity-associated variation in FFM.

Interpreting Aerobic Fitness in Youth: The Fallacy of Ratio Scaling

“…Interestingly, an inflated exponent was not observed for the girls with a similar within-study age range (study 10, Table 1 [8]), where the mass exponent was computed as b = 0.61. When added to the log-linear regression analysis here, and in contrast to the boys, age did not add significantly to the model; however, the addition of skinfold thickness did yield a significant, negative exponent as also observed in our recent longitudinal analysis of peakVO 2 in similar-aged girls (2).…”

Expert’s Choice: 2018’s Most Exciting Research in the Field of Pediatric Exercise Science

“…The 20mSRT has been proposed as a suitable and feasible health indicator for international surveillance in children and adolescents (90) and as a means of evaluating physical activity interventions (89). Others have argued that estimating/ predicting peakVO 2 from 20mSRT performance scores is untenable (10), the use of per-body mass ratio scaling is fallacious (10,168), the establishment of thresholds for cardiometabolic risk in children using current criteria is indefensible (9,10), and the use of field test performance estimates of peakVO 2 to evaluate physical activity interventions is specious (12). In this lively debate, Mintjens and colleagues' (107) thoughtful systematic review of longitudinal studies of the influence of CRF in childhood and adolescence on future cardiovascular risk factors is timely.…”

“…Unfortunately, the majority of papers that directly determined peakVO 2 only reported it in ratio with body mass. It has been demonstrated theoretically (169,170) and empirically (9,168) that ratio scaling has neither a sound scientific rationale nor statistical justification. Moreover it is age-and maturity-status-driven fat free mass, not body mass, which is the most powerful morphological influence on peakVO 2 (9).…”

“…It has been demonstrated theoretically (169,170) and empirically (9,168) that ratio scaling has neither a sound scientific rationale nor statistical justification. Moreover it is age-and maturity-status-driven fat free mass, not body mass, which is the most powerful morphological influence on peakVO 2 (9). Over 70 years ago Tanner (154) explained how spurious relationships arise when ratio-scaled data are correlated with other health-related variables and how children identified as "at risk" using this technique were likely suffering from "no more formidable a disease than statistical artefact" (154, p. 3).…”

Reflecting on Field Performance Tests of Pediatric Aerobic Fitness: After 30 Years, It Really Is Time to Move on

“…Perhaps they are just getting heavier and increasing body fat during adolescence-which is not the same as getting less fit! Why are overweight and obese youngsters so often classified as unfit using 20mSRT scores when rigorously determined and appropriately analyzed data suggest minimal aerobic fitness differences between normal and overweight children (2,11)? Perhaps this is a classic illustration of how ratio scaling underestimates fitness in heavier individuals?…”