Alterations in VO₂max and the VO₂ plateau with manipulation of sampling interval

BACKGROUND: The most accepted criterion for confirming attainment of VO(2)max is a plateau in oxygen consumption (VO(2)) at VO(2)max, but its incidence varies. AIMS: To compare VO(2)max and VO(2) plateau incidence across various sampling intervals, and to examine predictors of the change in VO(2) (DeltaVO(2)) at VO(2)max. METHODS: Sedentary, recreationally-active, and endurance-trained subjects (n = 108, age = 24.2 +/- 6.2 year) completed incremental exercise on the treadmill or cycle ergometer. Gas exchange data were obtained breath-by-breath and time-averaged every 15, 30, and 60 s. VO(2)max attainment was verified with the Taylor et al. (1955) criterion (DeltaVO(2) at VO(2)max < or =2.1 ml kg(-1) min(-1)). Multiple regression was used to examine predictors of DeltaVO(2) at VO(2)max. RESULTS: VO(2) plateau incidence was higher using breath-by-breath (81%) and 15 (91%) and 30 s time averaging (89%) versus 60 s averaging (59%). Compared to 60 s averaging, VO(2)max was significantly higher (P<0.05) when data were obtained breath-by-breath and with 15 and 30 s time-averaging compared to 60 s sampling. VO(2)max was not related to VO(2) plateau incidence. Respiratory rate was a significant predictor of DeltaVO(2) at VO(2)max in endurance-trained subjects. CONCLUSION: More frequent data acquisition revealed higher VO(2)max and incidence of the VO(2) plateau compared to 60 s time averaging. Secondary criteria to verify VO(2)max attainment should not be used, as they do not discern between subjects who do and do not reveal a plateau in VO(2) at VO(2)max.