The aim of this study was to address the question if the VO₂ kinetics is further improved as the aerobic training status increases from trained to elite level athletes. Maximal oxygen uptake (VO₂max), work-rate associated to VO₂max (IVO₂max) and VO₂ kinetics of moderate (Mod) and maximal exercise (Max) were determined in fifty- five subjects. Then, they were assigned into three groups: low (LF), intermediate (IF) and high (HF) aerobic fitness level. In average, the VO₂max of LF, IF and HF groups were, respectively, 36.0 ± 3.1, 51.1 ± 4.5 and 68.1 ± 3.9 ml·kg·min^-1 (p ≤ 0.05 among each other). VO₂ kinetics mean response time of both exercise intensities were significantly faster (p ≤ 0.05) in HF (Mod, 27.5 ± 5.5 s; Max, 32.6 ± 8.3 s) and IF (Mod, 25.0 ± 3.1 s; Max, 42.6 ± 10.4 s) when compared to LF (Mod, 35.7 ± 7.9 s; Max: 57.8 ± 17.8 s). We can conclude that VO₂ kinetics is improved as the fitness level is increased from low to intermediate but not further improved as the aerobic fitness level increases from intermediate to high.

• Currently, it is reasonable to believe that the rate-limiting step of VO kinetics depends on exercise intensity.

• The well known physiological adaptations induced by endurance training are likely the most extreme means to overcome rate-limiting steps determining VO kinetics across exercise intensities.

• However, exercise adaptation leading individuals to the high-end of aerobic fitness level range (VOmax > 65 ml.kg.min-1) is not able to further improve VO kinetics during both, moderate and maximal intensity exercise.