Abstract
PurposesTo investigate longitudinally (1) the contribution of morphological covariates to explaining the development of maximum cardiac output ({dot{text{Q}}} max) and maximum arteriovenous oxygen difference (a-vO2 diff max), (2) sex differences in {dot{text{Q}}} max and a-vO2 diff max once age, maturity status, and morphological covariates have been controlled for, and, (3) the contribution of concurrent changes in morphological and cardiovascular covariates to explaining the sex-specific development of peak oxygen uptake (dot{{V}}{mathrm{O}}_{2}).MethodsFifty-one (32 boys) 11–13-year-olds had their peak dot{{V}}{mathrm{O}}_{2}, maximum heart rate (HR max), {dot{text{Q}}} max, and a-vO2 diff max determined during treadmill running on three annual occasions. The data were analysed using multilevel allometric modelling.ResultsThere were no sex differences in HR max which was not significantly (p > 0.05) correlated with age, morphological variables, or peak dot{{V}}{mathrm{O}}_{2}. The best-fit models for {dot{text{Q}}} max and a-vO2 diff max were with fat-free mass (FFM) as covariate with age, maturity status, and haemoglobin concentration not significant (p > 0.05). FFM was the dominant influence on the development of peak dot{{V}}{mathrm{O}}_{2}. With FFM controlled for, the introduction of either {dot{text{Q}}} max or a-vO2 diff max to multilevel models of peak dot{{V}}{mathrm{O}}_{2} resulted in significant (p < 0.05) additional contributions to explaining the sex difference.Conclusions(1) With FFM controlled for, there were no sex differences in {dot{text{Q}}} max or a-vO2 diff max, (2) FFM was the dominant influence on the development of peak dot{{V}}{mathrm{O}}_{2}, and (3) with FFM and either {dot{text{Q}}} max or a-vO2 diff max controlled for, there remained an unresolved sex difference of ~ 4% in peak dot{{V}}{mathrm{O}}_{2} .
Highlights
Peak oxygen uptake ( V O2 ), the highest V O2 elicited during an incremental exercise test to exhaustion, is internationally recognized as the ‘gold standard’ measure of youth cardiorespiratory fitness
Longitudinal relationships by sex between HR max, Qmax, and a-vO2 diff max, respectively, with body mass (BM) and with fat-free mass (FFM) are illustrated in Figs. 1 and 2
Model 2.5 shows that with loge FFM controlled for, loge a-vO2 diff max was Directly comparing values of Qmax and a-vO2 diff max data across methodologies must be done with extreme caution (Warburton and Breder 2018), but the present data are in accord with values from cross-sectional studies which used CO2 rebreathing with aged children and adolescents (Gilliam et al 1977; Miyamura and Honda 1973: Yamaji and Miyashita 1977)
Summary
Peak oxygen uptake ( V O2 ), the highest V O2 elicited during an incremental exercise test to exhaustion, is internationally recognized as the ‘gold standard’ measure of youth cardiorespiratory fitness. The influence of concurrent changes in morphological and physiological covariates on the development of peak V O2 during childhood and adolescence remains to be elucidated (Armstrong and McManus 2017). Multilevel allometric modelling (Rasbash et al 2018) allows the effects of age, maturity status, morphological covariates, and physiological covariates to be partitioned concurrently within an allometric framework to provide a sensitive interpretation of the development of peak V O2. The application of multilevel allometric modelling has provided new insights into the role of morphological covariates in the development of cardiorespiratory fitness during childhood and adolescence (Armstrong and Welsman 2019a, b; Nevill et al 1998). Even with FFM controlled for, an unexplained sex difference in peak V O2 remained with boys’ values significantly (p < 0.05) higher than those of girls (Armstrong and Welsman 2019a, b)
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