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Preexercise metabolic alkalosis induced via bicarbonate ingestion accelerates O₂ kinetics at the onset of a high-power-output exercise in humans

¹Department of Muscle Physiology, AWF-Kraków, ²Faculty of Applied Mathematics, AGH University of Science and Technology Kraków, ³Cancer Institute-Kraków, and ⁴Faculty of Biotechnology, Jagiellonian University, Kraków, Poland

Submitted 7 November 2003 ; accepted in final form 18 October 2004

The present study investigated the effect of preexercise metabolic alkalosis on the primary component of oxygen uptake (O₂) kinetics, characterized by ₁. Seven healthy physically active nonsmoking men, aged 22.4 ± 1.8 (mean ± SD) yr, maximum O₂ (O_{2 max}) 50.4 ± 4 ml·min^–1·kg^–1, performed two bouts of cycling, corresponding to 40 and 87% of O_{2 max}, lasting 6 min each, separated by a 20-min pause, once as a control study and a few days later at 90 min after ingestion of 3 mmol/kg body wt of NaHCO₃. Blood samples for measurements of bicarbonate concentration and hydrogen ion concentration were taken from antecubital vein via catheter. Pulmonary O₂ was measured continuously breath by breath. The values of ₁ were calculated by using six various approaches published in the literature. Preexercise level of bicarbonate concentration after ingestion of NaHCO₃ was significantly elevated (P < 0.01) compared with the control study (28.96 ± 2.11 vs. 24.84 ± 1.18 mmol/l; P < 0.01), and [H⁺] was significantly (P < 0.01) reduced (42.79 ± 3.38 nmol/l vs. 46.44 ± 3.51 nmol/l). This shift (P < 0.01) was also present during both bouts of exercise. During cycling at 40% of O_{2 max}, no significant effect of the preexercise alkalosis on the magnitude of ₁ was found. However, during cycling at 87% of O_{2 max}, the ₁ calculated by all six approaches was significantly (P < 0.05) reduced, compared with the control study. The ₁ calculated as in Borrani et al. (Borrani F, Candau R, Millet GY, Perrey S, Fuchsloscher J, and Rouillon JD. J Appl Physiol 90: 2212–2220, 2001) was reduced on average by 7.9 ± 2.6 s, which was significantly different from zero with both the Student's t-test (P = 0.011) and the Wilcoxon's signed-ranks test (P = 0.014).

acid-base status; oxygen uptake; oxygen uptake kinetics; oxidative phosphorylation

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