Effect of sodium bicarbonate on muscle metabolism during intense endurance cycling.

Introduction: Sodium bicarbonate (NaHCO3) ingestion has been shown to increase both muscle glycogenolysis and glycolysis during brief submaximal exercise. These changes may be detrimental to performance during more prolonged, exhaustive exercise. This study examined the effect of NaHCO3 ingestion on muscle metabolism and performance during intense endurance exercise of similar to60 min in seven endurance-trained men. Methods: Subjects ingested 0.3 g(.)kg(-1) body mass of either NaHCO3 or CaCO3 (CON) 2 h before performing 30 min or cycling exercise at 77 +/- 1% (V)over dotO(2peak) followed by completion of 469 +/- 21 kJ as quickly as possible (similar to30 min, similar to80% (V)over dotO(2peak)). Results: Immediately before, and throughout exercise, arterialized-venous plasma HCO3- concentrations Acre higher (P < 0.05) whereas plasma and muscle H+ concentrations were lower (P < 0.05) in NaHCO3 compared with CON. Blood lactate concentrations were higher (P < 0.05) during exercise in NaHCO3, but there was no difference between trials in muscle glycogen utilization or muscle lactate content during exercise. Reductions in PCr and ATP and increases in muscle Cr during exercise were also unaffected by NaHCO3 ingestion. Accordingly, exercise performance time was not different between treatments. Conclusion: NaHCO3 ingestion resulted in a small muscle alkalosis but had no effect on muscle metabolism or intense endurance exercise performance in well-trained men.