Physiological differences in cardiopulmonary exercise testing between children and adults

Purpose: This study examines age- and sex-related physiological differences in cardiopulmonary exercise testing (CPET) between children and adults, focusing on ventilatory thresholds (VT) and oxygen uptake efficiency slope and plateau (OUES; OUEP). Methods: The cross-sectional analysis comprised 24 children (7–11 years), 20 moderately- trained (MTA) and 20 well-trained (WTA) adults (20–30 years). They performed a maximal CPET on a cycle ergometer, while respiratory responses were measured. Linear regression models analyzed differences by age and sex of the key outcome parameters VT1, VT2, OUES and OUEP. Results: Children exhibited higher absolute VO2 at VT1 (d=.66) and VT2 (d=.58) values than MTA but slightly lower VO2 at VT2 values compared to WTA (d=.35). Adults demonstrated higher OUES (MTA: d=.37; WTA: d=1.45) and OUEP (MTA: d=.81; WTA: d=.60) values than children. However, children had higher relative OUES when adjusted for body mass (OUESrel) (MTA: d=.1.80; WTA: d=.87). Males demonstrated higher values as females for VO2 at VT2 (d=.81), OUES (d=.79) and OUEP (d=.41), respectively. In contrast, females had higher VO2 at VT1 (d=.59) and VT2 (d=.44) relative to VO2peak as males. Conclusion: These findings suggest that compared to adults, children rely more on oxidative metabolism, reflected in higher ventilatory thresholds relative to their aerobic capacity. Absolute OUES and OUEP increased with age, but OUESrel values indicate that maturation influences efficiency more than body mass, reflecting underlying metabolic and physiological differences. These age- and sex-specific patterns highlight the need for further longitudinal research to clarify the roles of growth and training on these parameters.