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.