Ventilation and blood lactate increase exponentially during incremental exercise

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Abstract
This study examined whether the ventilatory (V) compensation for metabolic acidosis with increasing O2 uptake (VO2 ) and CO2 output (VCO2) might be more in accord with the theoretical expectation of a progressive acceleration of proton production from carbohydrate oxidation rather than a sudden onset of blood lactate (BLa) accumulation. The interrelationships between V, VO2, VCO2 and BLa concentration, [BLa], were investigated in 10 endurance‐trained male cyclists during incremental (120+15 W min‐1) exercise tests to exhaustion. Regression analyses on the V, VCO2 and [BLa] vs VO2 data revealed that all were better fitted by continuous Y=A. exp. [B .V O2] + C rate laws than by threshold linear rate equations (P< 0.0001). Plots of V vs VCO2 and [BLa] were also non‐linear. Ventilation increased as an exponential V= 27 ± 4 . exp . [0.37 ± 0.03 . VCO2] function of VCO2 and as a hyperbolic function of [BLa]. In opposition to the ‘anaerobic (lactate) threshold’ hypothesis, we suggest these data are more readily explained by a continuous development of acidosis, rather than a sudden onset of BLa accumulation, during progressive exercise.

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