The highest work rate associated with a predominantly aerobic contribution coincides with the highest work rate at which VO_2max can be attained

To estimate the highest power output at which predominant energy contribution is derived from the aerobic system (aerobic limit power: ALP) and to compare ALP with the upper boundary of the severe intensity exercise domain.

Fifteen male individuals participated in this study. The upper boundary was estimated using i) linear relationship between time to achieve \(\dot{\text{V}}\) $\dot{\text{V}}$ O_2max and time to task failure (P_UPPERBOUND), ii) hyperbolic relationships between time to achieve \(\dot{\text{V}}\) $\dot{\text{V}}$ O_2max vs. power output, and time to task failure vs. power output (P_UPPERBOUND´), and iii) precalculated \(\dot{\text{V}}\) $\dot{\text{V}}$ O_2max demand (I_HIGH). ALP was estimated by aerobic, lactic, and phospholytic energy contributions using \(\dot{\text{V}}\) $\dot{\text{V}}$ O₂ response, blood [lactate] response, and fast component of recovery \(\dot{\text{V}}\) $\dot{\text{V}}$ O₂ kinetics, respectively.

ALP was determined as the highest power output providing predominant aerobic contribution; however, anaerobic pathways became the predominant energy source when ALP was exceeded by 5% (ALP + 5%) (from 46 to 52%; p = 0.003; ES:0.69). The \(\dot{\text{V}}\) $\dot{\text{V}}$ O₂ during exercise at ALP was not statistically different from \(\dot{\text{V}}\) $\dot{\text{V}}$ O_2max (p > 0.05), but \(\dot{\text{V}}\) $\dot{\text{V}}$ O_2max could not be attained at ALP + 5% (p < 0.01; ES:0.63). ALP was similar to P_UPPERBOUND and P_UPPERBOUND´ (383 vs. 379 and 384 W; p > 0.05). There was a close agreement between ALP and P_UPPERBOUND (r: 0.99; Bias: − 3 W; SEE: 6 W; TE: 8 W; LoA: − 17 to 10 W) and P_UPPERBOUND´ (r: 0.98; Bias: 1 W; SEE: 8 W; TE: 8 W; LoA: − 15 to 17 W). ALP, P_UPPERBOUND, and P_UPPERBOUND´ were greater than I_HIGH (339 ± 53 W; p < 0.001).

ALP may provide a new perspective to intensity domain framework.