Increased blood pH but not performance with sodium bicarbonate supplementation in elite rugby union players
Journal Title (Medline/Pubmed accepted abbreviation): Int. J. Sport Nutr. Exerc. Metab.
Year: 2010
Volume: 20
Page numbers: 307-321
doi (if applicable):

Summary of Background and Research Design

Background:High intensity, short duration activity relies on the anaerobic, glycolytic pathway which produces lactate and hydrogen ions (H+) as by products. Bicarbonate (HCO3-) is the most abundant acid buffer in blood. The bicarbonate pool is small and, when the concentration of H+ exceeds the blood's buffering capacity, the pH of the blood decreases and may inhibit contractile activity in skeletal muscle. Supplementation with sodium bicarbonate (NaHCO3) is predicted to increase the buffering capacity of the blood, but may contribute to gastrointestinal (GI) disturbances such as bloating, flatulence, and diarrhea. These GI intolerances may lead to decreased performance.

Research Question: Does supplementation with sodium bicarbonate increase the buffering capacity of the blood with minimal GI disturbances and lead to subsequent higher blood pH and increased performance?

Subjects: 25 elite male rugby players, age 21.6 ± 2.6.

Experimental design:Randomized, double-blind, placebo-controlled crossover trial

Treatments and protocol:Thirty min after consuming a standardized snack, participants consumed 500 mL of an isotonic sports drink, with either 0.3 g/kg body weight of sodium bicarbonate or 0.045 g/kg body weight of NaCl as a placebo. The subjects also consumed a minimum of 750 mL of additional water at that time. Sixty-five min later, they had 25 min warm-up followed by a rugby-specific repeated sprint test (RSRST) comprising 9 min of high-intensity repeated-sprint tests. During the entire protocol participants were able to drink water ad libitum. Whole blood was collected at baseline, after supplementation, and immediately after the sprints. GI discomfort questionnaires were completed at 30, 60, 90, and 120 min after the beverage ingestion and participants were asked to record any GI symptoms for the following 24 hrs.

Summary of research findings:
  • Performance in the RSRST was not statistically different between the two groups.
  • From the baseline value to just after the RSRST, blood pH dropped from 7.38 ± 0.01 to 7.19 ± 0.02 for the placebo group and from 7.39 ± 0.01 to 7.25 ± 0.02 for the NaHCO3 group (P < 0.001)
  • Bicarbonate levels were significantly higher for the NaHCO3 group just prior to and also post-exercise
  • GI disturbances were significantly more frequent and more severe after ingestion of NaHCO3. About ½ of the participants who ingested NaHCO3 experienced vomiting and diarrhea either just before or during exercise.

Interpretation of findings/Key practice applications:

  • NaHCO3 supplementation may provide higher buffer capacity of blood, but improvements in performance may be minimal.
  • Experimentation with sodium bicarbonate (NaHCO3) supplementation should be performed in a practice setting to assess the severity of GI intolerances.
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