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 (V̇O_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, base excess (BE) and ventilatory variables were measured. At the beginning of the IT for LM, the ventilation, PO₂ and V̇O₂ 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 [V̇ _E; 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 V̇O_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 V̇O_2max attainment; (3) and the IGT and GM can predict the Trans.