Rates of maximal blood lactate accumulation in the extreme intensity exercise domain: implications for training...

This study investigated the rate of blood lactate accumulation (vLa) across six maximal sprint efforts and identified a breakpoint (vLa_BP) in the vLa-power relationship.

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 vLa 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 vLa_BP and its corresponding power output (P-vLa_BP) in the vLa-power relationship. Pulmonary V̇O₂ responses were modelled using V̇O₂ data obtained from exercise and the subsequent 15-min recovery period.

A distinct P-vLa_BP was identified at 795 ± 135 W and 11.2 ± 1.5 W·kg^-1, corresponding to a vLa 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 vLa 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). V̇O₂ on-kinetics below the P-vLa_BP (30 and 15 s) was best described by linear function (R² ≥ 0.96; SEE ≤ 272 mL·min^-1; p < 0.001), while the V̇O₂ data could not be modelled for sprints performed above the P-vLa_BP (10 and 5 s).

The present study demonstrated that the P-vLa_BP separates ranges of power outputs with discrete V̇O₂ kinetics which are characteristic of different subzones within the extreme intensity exercise domain.