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

Modulation of testing conditions such as resting lactate (La_rest) levels or carbohydrate intake may affect the calculation of the maximal glycolytic rate (νLa.max). To evaluate the impact of elevated La_rest 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: La_rest ≤1.5 mmol·L^-1; (II). Lactate+: La_rest ≥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 La_peak and La_rest lactate concentration (La_peak, mmol · L^-1). AcuteCHO led to an increase in La_rest 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 La_rest to below ≤1.5 mmol·L-1, is crucial to prevent the unintentional underestimation of νLa.max.