The highest work rate associated with a predominantly aerobic contribution coincides with the highest work rate at which VO2max can be attained

Purpose 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. Methods Fifteen male individuals participated in this study. The upper boundary was estimated using i) linear relationship between time to achieve VO2max and time to task failure (P-UPPERBOUND), ii) hyperbolic relationships between time to achieve VO2max vs. power output, and time to task failure vs. power output (P-UPPERBOUND'), and iii) precalculated VO2max demand (IHIGH). ALP was estimated by aerobic, lactic, and phospholytic energy contributions using VO2 response, blood [lactate] response, and fast component of recovery VO2 kinetics, respectively. Results 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 VO2 during exercise at ALP was not statistically different from VO2max (p > 0.05), but VO2max 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). Conclusion ALP may provide a new perspective to intensity domain framework.