Efficacy of constant load verification testing to confirm VO₂ max attainment

Although maximal oxygen uptake (VO₂ max) has been measured for almost 100 years, it is unknown when 'true' VO₂ max is attained. Primary (the VO₂ plateau) and secondary criteria are used to confirm VO₂ max incidence, but frequency of the VO₂ plateau varies, and secondary criteria are relatively invalid. The verification test (VER) seems to elicit similar estimates of VO₂ max versus the incremental value (INC), yet existing data are limited by small populations and use of inadequate criteria to confirm 'true' VO₂ max. We investigated the efficacy of VER by analysing data from 109 participants who underwent INC followed by VER at 105% or 110% of peak power output (PPO). Differences in VO₂ max between VER and INC were analysed, and intraclass correlation coefficient (ICC), standard error of the mean (SEM) and minimum difference (MD) were computed. Results showed that VO₂ max was significantly higher (2%, P<0·05) in INC versus VER, VO₂ max was highly related between protocols (ICC = 0·99) and SEM and MD were low. However, 11% of participants did not reveal 'true' VO₂ max as the verification value was higher than INC by 3·0% - 3·3%. Fitness level altered the difference in VO₂ max between INC and VER in study one, as lower fitness individuals showed a larger difference in VO₂ max between protocols, although gender did not affect the difference in VO₂ max between protocols. Our data show that VER does not verify 'true' VO₂ max in all individuals, which may be related to their fitness level.