Cardiopulmonary responses to exercise

Abstract

AbstractDuring exercise, children and adolescents adopt a different breathing pattern and hyperventilate for a given metabolic demand compared to adults. The ventilatory threshold occurs at a higher percentage of peak oxygen uptake (V.O2peak) and the phase I delay and phase II ventilation time constant at the onset of exercise increase with age. After a rapid rise at the onset of exercise, stroke volume (SV) stabilises at ~50–60% V.O2peak. A continuing increase in heart rate (HR) is responsible for further increases in cardiac output (Q.) which rises in a curvilinear manner, with diminishing circulatory efficiency at near V.O2peak compensated for by an increase in arteriovenous oxygen content difference. Multiplicative allometric modelling of data has confirmed the importance of analysing sex-specific, concurrent changes in age-, growth-, and maturation-driven covariates when exploring the development of cardiopulmonary data. In all cases with age and fat-free mass (FFM) controlled for, maturity status does not make a significant, independent contribution to explaining the development of peak/maximum cardiopulmonary variables. Peak breathing frequency and HRmax are largely independent of sex, age, growth, maturity status, and V.O2peak. Pulmonary ventilation does not appear to limit the V.O2peak of healthy youth but even with FFM controlled for, SVmax or Q.max make an independent, significant contribution to explaining the development of cardiopulmonary fitness. Further longitudinal studies covering the prepubertal, pubertal, and postpubertal years and incorporating multiple covariates are necessary to elucidate fully the development of maximum cardiopulmonary variables and cardiopulmonary fitness.