Although maximal oxygen uptake (VO max) has been measured for almost 100 years, it is unknown when 'true' VO max is attained. Primary (the VO plateau) and secondary criteria are used to confirm VO max incidence, but frequency of the VO plateau varies, and secondary criteria are relatively invalid. The verification test (VER) seems to elicit similar estimates of VO max versus the incremental value (INC), yet existing data are limited by small populations and use of inadequate criteria to confirm 'true' VO 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 VO 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 VO max was significantly higher (2%, P<0·05) in INC versus VER, VO max was highly related between protocols (ICC = 0·99) and SEM and MD were low. However, 11% of participants did not reveal 'true' VO max as the verification value was higher than INC by 3·0% - 3·3%. Fitness level altered the difference in VO max between INC and VER in study one, as lower fitness individuals showed a larger difference in VO max between protocols, although gender did not affect the difference in VO max between protocols. Our data show that VER does not verify 'true' VO max in all individuals, which may be related to their fitness level.