Abstract
Purpose This study investigated the rate of blood lactate accumulation ( v La) across six maximal sprint efforts and identified a breakpoint ( v La BP ) in the v La–power relationship. Methods Twelve physically active males completed 5, 10, 15, 20, 25, and 30-s all-out sprints in randomised order on separate days, with resistances set at 10 to 12.5% of body mass. The v La was calculated as the change in blood lactate between the resting and peak value (∆La) divided by the test duration. A piecewise linear regression was used to identify the v La BP and its corresponding power output (P- v La BP ) in the v La–power relationship. Pulmonary V̇O 2 responses were modelled using V̇O 2 data obtained from exercise and the subsequent 15-min recovery period. Results A distinct P- v La BP was identified at 795 ± 135 W and 11.2 ± 1.5 W·kg −1 , corresponding to a v La of 0.50 ± 0.10 mM·s –1 , ∆La of 6.50 ± 1.27 mM, and sprint duration of 13.3 ± 1.9 s. The v La did not increase significantly during the 30, 25, 20, and 15-s all-out sprint tests (0.41 ± 0.04 to 0.48 ± 0.10 mM·s⁻ 1 ; p > 0.05) but increased markedly in the 10 and 5-s tests (0.58 ± 0.14 mM·s⁻ 1 , p < 0.05; 0.7 ± 0.20 mM·s⁻ 1 , p < 0.01). V̇O 2 on-kinetics below the P- v La BP (30 and 15 s) was best described by linear function (R 2 ≥ 0.96; SEE ≤ 272 mL·min –1 ; p < 0.001), while the V̇O 2 data could not be modelled for sprints performed above the P- v La BP (10 and 5 s). Conclusion The present study demonstrated that the P- v La BP separates ranges of power outputs with discrete V̇O 2 kinetics which are characteristic of different subzones within the extreme intensity exercise domain.