Abstract
To evaluate the changes in muscle energetics following NaHCO3 intake, we measured the phosphorus-31 nuclear magnetic resonance (31P NMR) spectra of human muscle in vivo during exercise. Seven male subjects performed two trials, a NaHCO3 (Alka, Tr.) and a NaCI trial (Cont. Tr.), on two occasions. 31P NMR spectra were obtained serially during leg-elevating exercises. Before and during exercise, the intracellular phosphocreatine (PCr), inorganic phosphate (Pi) and pH were determined from the NMR spectra. The decrease of intracellular pH during exercise showed a tendency to be inhibited by NaHCO3 intake, and the intracellular pH at the end of the exercise was 6.69 for Alka. Tr, and 6.51 for Cont. Tr. The decline of the PCr/ (PCr+Pi) ratio during exercise was not influenced by NaHCO3 intake. The PCr/ (PCr+Pi) ratio was related exponentially to the intracellular pH. A remarkable decline of PCr/ (PCr+Pi) ratio occurred until the intracellular pH fell to about 6.7, but did not decrease below that. It was suggested that the intake of NaHCO3 could decrease the rate of fall in the intracellular pH during exercise, and that the PCr store could be influenced by the intracellular pH when the pH was above 6.7, but not below that level.
