Examining based-time cardiopulmonary responses during a cycling time-to-exhaustion test considering maturity offset among trained youth male soccer players

This study aimed to investigate the potential relationship between maturity offset and cardiopulmonary responses, and to determine at which relative time points these responses differ markedly throughout the exercise duration. Ninety-two trained youth male soccer players performed progressive cycling to exhaustion on an ergometer with simultaneous breath-by-breath assessment of key cardiopulmonary parameters, including oxygen uptake (VO 2 ), carbon dioxide production (VCO 2 ), minute ventilation (VE), oxygen saturation (SpO 2 ), heart rate (HR), and heart rate reserve (HRR). The quantile and functional concurrent regression analyses revealed that maturity offset significantly and variably associated with the magnitude, distribution, and time-dependent changes in cardiopulmonary responses. The findings revealed maturity-dependent cardiopulmonary response patterns; VO 2 and VCO 2 showed positive maturity effects across all quantiles, and inter-individual variability decreased with advancing maturation as the lower (τ = 0.10) and upper (τ = 0.90) quantiles converged toward the median at later maturity stages. Furthermore, functional concurrent regression analyses revealed that relationships with maturity offset were more pronounced in VO 2 and VCO 2 from the 10% iso-time onward (p < 0.001), and in VE from the 40% iso-time onward (p < 0.001). In contrast, estimated maturity offset effects on VO 2 peak, HR and HRR were only transient, appearing in early-to-mid exercise stages (p < 0.050) but diminishing toward later time points. These findings suggest that maturity advantages in cardiopulmonary responses become more pronounced at starting or relatively moderate intensities (≥10−40% of iso-time points), whereas cardiovascular capacity showed smaller differences and tended to converge toward maximum effort. Practitioners should consider maturity offset when interpreting CPET profiles in youth athletes.