Fig 1.
Flowchart of the inclusion-exclusion and further groups classification process.
Age classification is presented in years. Endurance classification has been performed based on speed/power at respiratory compensation point (RCP) which is currently described as a variable most closely corresponding to the critical power. Moreover, the selection of a variable different from VO2max to the classification of participants in terms of their endurance capacity, enable to make group assignments independent of the factor directly validated in the study. Abbreviations: EA, endurance athlete; CPET, cardiopulmonary exercise testing; SD, standard deviation; RER, respiratory exchange ratio; VO2, oxygen uptake(mL·min-1·kg-1); LA, lactate concentration (mmol·L-1); fR, breathing frequency (breaths·min-1); RCP, respiratory compensation point; HRpeak, peak heart rate during CPET (bpm); HRmax, maximal heart rate during CPET (bpm); F, female; M, male; HTEA, high-trained endurance athletes; REA, recreational endurance athletes, LTEA, low-trained endurance athletes.
Table 1.
Participants’ basic anthropometric characteristics.
Fig 2.
Regression analysis (RA) of predicted and observed VO2max for whole population (both males and females with included „transition” group) stratified by age.
95% confidence intervals are presented with grey color. Subgroups that did not meet the TRIPOD guidelines to consider their validation results as reliable (i.e n≥100) were marked with [‡]. Abbreviations: VO2max, maximal oxygen uptake. [A] RA for males and females for CE models; [B] RA for males and females for TE models; [C] RA for males for TE or CE models (Wilson et al. and Kokkinos et al.[1]); [D] RA for females for TE or CE models (Fitzgerald et al. and Kokkinos et al.[2]); [E] RA for males for TE or CE model (Kokkinos et al.[3]); [F] RA for females for TE or CE model (Kokkinos et al.[3]).
Fig 3.
Regression analysis (RA) of predicted and observed VO2max for HTEA stratified by age.
95% confidence intervals are presented with grey color. Subgroups that did not meet the TRIPOD guidelines to consider their validation results as reliable (i.e n≥100) were marked with [‡]. Abbreviations: VO2max, maximal oxygen uptake. [A] RA for males‡ and females‡ for CE models; [B] RA for males and females‡ for TE models; [C] RA for males for TE or CE‡ models (Wilson et al. and Kokkinos et al.[1]); [D] RA for females for TE‡ or CE‡ models (Fitzgerald et al. and Kokkinos et al.[2]); [E] RA for males for TE or CE‡ model (Kokkinos et al.[3]); [F] RA for females for TE‡ or CE‡ model (Kokkinos et al.[3]).
Fig 4.
Regression analysis (RA) of predicted and observed VO2max for REA stratified by age.
95% confidence intervals are presented with grey color. Subgroups that did not meet the TRIPOD guidelines to consider their validation results as reliable (i.e n≥100) were marked with [‡]. Abbreviations: VO2max, maximal oxygen uptake. [A] RA for males and females‡ for CE models; [B] RA for males and females‡ for TE models; [C] RA for males for TE or CE models (Wilson et al. and Kokkinos et al.[1]); [D] RA for females for TE‡ or CE‡ models (Fitzgerald et al. and Kokkinos et al.[1]); [E] RA for males for TE or CE model (Kokkinos et al.[3]); [F] RA for females for TE‡ or CE‡ model (Kokkinos et al.[3]).
Fig 5.
Regression analysis (RA) of predicted and observed VO2max for LTEA stratified by age.
95% confidence intervals are presented with grey color. Subgroups that did not meet the TRIPOD guidelines to consider their validation results as reliable (i.e n≥100) were marked with [‡]. Abbreviations: VO2max, maximal oxygen uptake. [A] RA for males‡ and females‡ for CE models; [B] RA for males and females‡ for TE models; [C] RA for males for TE or CE‡ models (Wilson et al. and Kokkinos et al.[1]); [D] RA for females for TE‡ or CE‡ models (Fitzgerald et al. and Kokkinos et al.[2]); [E] RA for males for TE or CE‡ model (Kokkinos et al.[3]); [F] RA for females for TE‡ or CE‡ model (Kokkinos et al.[3]).
Table 2.
Performance of selected models stratified by endurance level and sex.
Table 3.
Performance of selected models stratified by age and sex.