Effects of pre-exercise alkalosis on the decrease in VO2 at the end of all-out exercise

International audience; Purpose This study determined the effects of pre-exercisesodium bicarbonate ingestion (ALK) on changes in oxygenuptake (V˙ O2) at the end of a supramaximal exercise test(SXT).Methods Eleven well-trained cyclists completed a 70-sall-out cycling effort, in double-blind trials, after oral ingestionof either 0.3 g kg−1 of sodium bicarbonate (NaHCO3)or 0.2 g kg−1 body mass of calcium carbonate (PLA).Blood samples were taken to assess changes in acid–basebalance before the start of the supramaximal exercise, and0, 5 and 8 min after the exercise; ventilatory parameterswere also measured at rest and during the SXT.Results At the end of the PLA trial, which induced mildacidosis (blood pH = 7.20), subjects presented a significantdecrease in V˙ O2 (P < 0.05), which was related to the amplitude of the decrease in minute ventilation (˙VE) duringthe SXT (r = 0.70, P < 0.01, n = 11). Pre-exercise metabolicalkalosis significantly prevented the exercise-induceddecrease in V˙ O2 in eleven well-trained participants (PLA:12.5 ± 2.1 % and ALK: 4.9 ± 0.9 %, P < 0.05) and thedecrease in mean power output was significantly less pronouncedin ALK (P < 0.05). Changes in the V˙ O2 decreasebetween PLA and ALK trials were positively related tochanges in the ˙VE decrease (r = 0.74, P < 0.001), but not tochanges in power output (P > 0.05).Conclusions Pre-exercise alkalosis counteracted the V˙ O2decrease related to mild acidosis, potentially as a result ofchanges in ˙V E and in muscle acid–base status during theall-out supramaximal exercise.