Increased resting lactate levels and reduced carbohydrate intake cause νLa.max underestimation by reducing net lactate accumulation

Modulation of testing conditions such as resting lactate (Larest) levels or carbohydrate intake may affect the calculation of the maximal glycolytic rate (νLa.max). To evaluate the impact of elevated Larest as well as reduced and increased carbohydrate availability on νLa.max in running sprints (RST), twenty‐one participants completed five 15‐s RST tests on a running track under five different conditions: (I). baseline: Larest ≤1.5 mmol·L⁻¹; (II). Lactate+: Larest ≥2.5 mmol·L⁻¹; (III). CHO−: carbohydrate intake: ≤ 1 g·kg⁻¹ BW d⁻¹ for 3 days; (IV). CHO+: carbohydrate intake: ≥ 9 g·kg⁻¹ BW d⁻¹ for one day; and (V). acuteCHO: 500 mL glucose containing beverage consumed before RST. νLa.max was significantly reduced in lactate+ and CHO− conditions compared to the baseline RST, due to a reduction in the arithmetic mean delta (∆) between Lapeak and Larest lactate concentration (Lapeak, mmol · L⁻¹). AcuteCHO led to an increase in Larest compared to baseline, CHO− and CHO+ with a high interindividual variability but did not significantly reduce νLa.max. Therefore, avoiding low carbohydrate nutrition before νLa.max testing, along with carefully adjusting Larest to below ≤1.5 mmol·L‐1, is crucial to prevent the unintentional underestimation of νLa.max.