The highest intensity and the shortest duration permitting attainment of maximal oxygen uptake during cycling: effects of different methods and aerobic fitness level

The aims of this study were: (1) to verify the validity of previous proposed models to estimate the lowest exercise duration (T _LOW) and the highest intensity (I _HIGH) at which VO₂max is reached (2) to test the hypothesis that parameters involved in these models, and hence the validity of these models are affected by aerobic training status. Thirteen cyclists (EC), eleven runners (ER) and ten untrained (U) subjects performed several cycle-ergometer exercise tests to fatigue in order to determine and estimate T _LOW (ET _LOW) and I _HIGH (EI _HIGH). The relationship between the time to achieved VO₂max and time to exhaustion (T _lim) was used to estimate ET _LOW. EI _HIGH was estimated using the critical power model. I _HIGH was assumed as the highest intensity at which VO₂ was equal or higher than the average of VO₂max values minus one typical error. T _LOW was considered T _lim associated with I _HIGH. No differences were found in T _LOW between ER (170 ± 31 s) and U (209 ± 29 s), however, both showed higher values than EC (117 ± 29 s). I _HIGH was similar between U (269 ± 73 W) and ER (319 ± 50 W), and both were lower than EC (451 ± 33 W). EI _HIGH was similar and significantly correlated with I_HIGH only in U (r = 0.87) and ER (r = 0.62). ET _LOW and T _LOW were different only for U and not significantly correlated in all groups. These data suggest that the aerobic training status affects the validity of the proposed models for estimating I _HIGH.