Comprehensive Analysis of Cardiopulmonary Exercise Testing Characterizes Age-Related Exercise Performance in Growing Children and Adolescents

Abstract

Background Cardiopulmonary exercise testing (CPET) estimates physical fitness level and cardiovascular reserve. How age-related growth and maturation affect exercise performance is complex, especially due to changes in body habitus during puberty. Methods Peak and submaximal CPET parameters by cycle ergometer were retrospectively analyzed to characterize how age and sex affect exercise performance during adolescence. Results One hundred sixty five young subjects were divided into six groups based upon their ages: ≤ 11 years old (yo) (24 males, 20 females), 12 to 15 yo (34 males, 41 females), and ≥ 16 yo (27 males, 19 females). Peak heart rate (HR) was comparable among all groups. Peak systolic blood pressure, peak oxygen consumption (VO2), peak work rate (WR), peak oxygen pulse (OP), and peak minute ventilation (VE) showed age-dependent increase in both sexes with more progressive increase in males than in females. Weight-indexed stroke volume estimate (D[VO2/kg]/DHR and peak OP/kg) was comparable in all male groups but was lower in female ³ 12 yo groups than in ≤ 11 yo group, whereas heart rate-dependency (DHR/D[WR/kg]) revealed continuous decrease with ages in males with no change in females. Regression lines between weight and peak VO2 demonstrated significant age-related increase of slope in males but not in females, suggesting age-related skeletal muscle enhancement only in males. Gradual increase in work efficiency (lower ΔVO2/ΔWR), ventilatory efficiency (lower ΔVE/ΔVCO2), and peak respiratory exchange ratio were noted with increase in ages independent of sex, indicating common functional maturation with age. Conclusion Age-related increase in exercise performance during adolescence is complex, characterized by the increased body size due to linear growth (males more than females), sex-dependent pubertal changes (more muscle mass and strength in males and more fat mass in females), and sex-independent enhanced functional maturation. This unique and simple CPET analysis can provide us with a wealth of data representing underlying exercise physiology of ordinary adolescents. These noninvasive biomarkers would help us better understand the cardiopulmonary reserve in those with borderline physical conditioning and those with subclinical cardiovascular abnormalities.