Abstract

Cardiovascular and haematological adaptations to endurance training facilitate greater maximal oxygen consumption, and such adaptations maybe augmented following puberty. Therefore, we compared left ventricular (LV) morphology (echocardiography), blood volume, haemoglobin (Hb) mass (CO-rebreathe) and in endurance-trained and untrained boys (n = 42, age = 9.0-17.1 years, = 61.6±7.2 mL∙kg∙min, and n = 31, age = 8.0-17.7 years, O2max = 46.5±6.1 mL∙kg∙min, respectively) and girls (n = 45, age = 8.2-17.0 years, O2max = 51.4±5.7 mL∙kg∙min and n = 36, age = 8.0-17.6 years, O2max = 39.8±5.7 mL∙kg∙min, respectively). Pubertal stage was estimated via maturity offset, with participants classified as pre- or post-peak height velocity (PHV). Pre-PHV, only a larger LV end-diastolic volume/lean body mass (EDV/LBM) for trained boys (+0.28 mL∙kgLBM, P = 0.007) and a higher Hb mass/LBM for trained girls (+1.65 g∙kgLBM, P = 0.007) were evident compared to untrained controls. Post-PHV, LV mass/LBM (boys:+0.50 g∙kgLBM, P = 0.0003; girls:+0.35 g∙kgLBM, P = 0.003), EDV/LBM (boys:+0.35 mL∙kgLBM, P<0.0001; girls:+0.31 mL∙kgLBM, P = 0.0004), blood volume/LBM (boys:+12.47 mL∙kgLBM, P = 0.004; girls:+13.48 mL∙kgLBM, P = 0.0002.) and Hb mass/LBM (boys:+1.29 g∙kgLBM, P = 0.015; girls:+1.47 g∙kgLBM, P = 0.002) were all greater in trained vs. untrained groups. Pre-PHV, EDV (R2adj = 0.224, P = 0.001) in boys, and Hb mass and interventricular septal thickness (R2adj = 0.317, P = 0.002) in girls partially accounted for the variance in O2max. Post-PHV, stronger predictive models were evident via the inclusion of LV wall thickness and EDV in boys (R2adj = 0.608, P<0.0001), and posterior wall thickness and Hb mass in girls (R2adj = 0.490, P<0.0001). In conclusion, cardiovascular adaptation to exercise training is more pronounced post-PHV, with evidence for a greater role of central components for oxygen delivery.

Abstract figure legend: Schematic diagram depicting cardiac structural and haematological differences between trained and untrained boys and girls, pre-peak height velocity (PHV) and post-PHV alongside cardiac and haematological variables contributions to the variance in O2max. Cardiac and haematological variables are greater in trained vs. untrained pre-pubertal children, and a greater number and magnitude of differences are observed at post-PHV. These variables provide significant predictive models for maximal oxygen consumption in children and are much stronger post-PHV, suggesting that other important determinants within the oxygen transport chain could account for the majority of variance in O2max before puberty.

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