Blood glucose threshold and the metabolic responses to incremental exercise tests with and without prior lactic acidosis induction

This study compared the metabolic-ventilatory responses and the glycemic threshold identified during lactate minimum (LM) and individual anaerobic threshold (IAT) tests. In addition, the ability to determine the anaerobic power, aerobic-anaerobic transition (Trans) (e.g. ventilatory threshold; VT) and the maximal oxygen consumption (̇VO_2max) all within a single incremental treadmill test (IT) was investigated. Fifteen physically fit men [25.9 (5.5) years; 77.4 (6.5) kg] performed the following: test 1, IT for IAT; and test 2, LM: 30-s Wingate test followed by 8 min rest and then an IT that was the same as test 1. Blood lactate concentration [lac], glucose concentration [gluc], pH, PO₂, PCO₂, basc excess (BE) and ventilatory variables were measured. At the beginning of the IT for LM, the ventilation, PO₂ and ̇VO₂ were higher and the pH, BE and PCO₂ were lower in relation to IAT (P<0.05, while no differences were observed after reaching LM intensity during IT. Moreover, the Trans could be identified by [lac] (IAT. LM), minute ventilation [V_Ei VT identified during IAT protocol (VT-IAT) and VT identified during LM protocol (VT-LM)], and [gluc] (IGT, GM) during the IT for IAT and LM. The velocities (kilometers per hour) corresponding to IAT (12.6 ± 1.6), VT-IAT (12.5 ± 1.7), IGT (12.6 ± 1.6), LM (12.5 ± 1.5), VT-LM (12.3 ± 1.5), and GM (12.6 ± 1.9) were not different from each other and the LM and IAT protocols resulted in the similar ̇VO_2max. We concluded that: (1) after reaching the LM the metabolic responses during IT are similar to IAT; (2) performing a Wingate test prior to an IT does not interfere with the Trans and VO_2max attainment; (3) and the IGT and GM can predict the Trans.