External validation of VO2max prediction models based on recreational and elite endurance athletes

Figures

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  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.

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  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]).

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  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]).

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  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]).

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  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]).