Effects of bicarbonate ingestion on the respiratory compensation threshold and maximal exercise performance.
Six males performed cycle ergometer exercise on two occasions in random order. Each exercise was preceded by a 2-h period in which matched capsules were administered orally, containing either starch (C) or NaHCO3 (E) in a dose of a 0.2 g.kg-1 body wt; pre-exercise blood pH and [HCO3-] were 7.34 +/- 0.01 and 23.7 +/- 0.5 mM (mean +/- S.E.) for the C study, and 7.41 +/- 0.01 and 28.6 +/- 1.3 mM for the E study (p less than 0.001 and p less than 0.01, respectively). Exercise was continuous and maintained for 10 min at 40% of maximal oxygen uptake (40% VO2max), followed by 15 min at 12 W above the respiratory compensation threshold ([+RCT]) which was determined by the increase of the ventilatory equivalent for carbon dioxide (VE.VCO2(-1)), and for as long as possible at 95% VO2max. Endurance time at 95% VO2max was significantly longer in E than in C (2.98 +/- 0.64 min vs. 2.00 +/- 0.44 min, p less than 0.05). The rate of increase in arterialized venous lactate (LA) was higher in E than in C from rest to exercise at [+RCT], while there was no significant difference in the hydrogen ions ([H+]). Consequently, [H+].LA-1 (nM.mM-1) was significantly lower in E than in C. The change of VE.VCO2(-1) was shifted downward in E compared to C during exercise with the lowest value being observed at the same exercise stage. These results suggest that the respiratory responses to exercise are not affected by the higher level of [HCO3-] induced by NaHCO3 ingestion, and appear to reflect the net change of plasma [HCO3-] or [H+]. Also, induced metabolic acidosis has little effect on [H+] appearance in blood.
Laboratory for Exercise Physiology and Biomechanics, Faculty of Education, University of Tokyo, Japan.
K
K
Iwaoka
S
S
Okagawa
Y
Y
Mutoh
M
M
Miyashita
D000136:Acid-Base Equilibrium / Q000187:drug effects; D000328:Adult; D000471:Alkalosis / Q000503:physiopathology*; D001639:Bicarbonates / Q000097:blood / Q000494:pharmacology; D001784:Blood Gas Analysis; D015444:Exercise; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007773:Lactates / Q000097:blood; D008297:Male; D011659:Pulmonary Gas Exchange; D012119:Respiration; D012129:Respiratory Function Tests; D013997:Time Factors
D001639:Bicarbonates; D007773:Lactates