Induced alkalosis and caffeine supplementation: effects on 2,000-m rowing performance


Journal Title (Medline/Pubmed accepted abbreviation): Intl. J. Sport. Nutr.Exerc.Metab.
Year: 2011
Volume: 21
Page Numbers: 357-364

Summary of background and research design:

Background: The 2,000-m rowing event requires very high intensity for about 6-8 min. Sodium bicarbonate (SB, baking soda) is a popular ergogenic aid because it can increase the concentration of bicarbonate in the blood, thus providing a larger buffering capacity against acid buildup and maintaining a healthy blood pH. However, SB may cause gastrointestinal discomfort which could offset any performance benefits that it might provide. Caffeine is the most popular ergogenic aid used in sports today. There is a wealth of evidence that caffeine can improve performance in short-term, high intensity sprint events.  

Hypothesis: The combination of SB and caffeine would increase power output during a 2,000-m rowing event. In addition, SB would increase pH of the blood regardless of caffeine ingestion.

Subjects: Eight rowers, 6 male and 2 female, (age undisclosed).

Experimental design:randomized, double-blind, placebo-controlled, cross-over design
 

Treatments: (Taken with 600 mL water)
90 min before the row (gelatin capsules):
            SB: sodium bicarbonate, 0.6 g/kg body mass, or
            P1: placebo, an equal number of capsules with corn flour
then, 30 min before the row (gelatin capsules):
            C: caffeine, 6 mg/kg body mass (about 450-500 mg), or
            P2: placebo, an equal number of capsules with glucose

Participants consumed each possible combination of treatments one time each (4 sessions).

Protocol: The participants reported to the laboratory on 6 occasions, 2 practice sessions and then the 4 experimental sessions. They arrived to the laboratory fasted at 6:00 am. They consumed the first treatment dose and rested for 1 hr. At t= -30 min they consumed the second treatment dose. At t=0 they performed a 7 min warm up and then performed the 2,000-m row on a stationary row machine with the goal of completing the row in the fastest time possible. Urine and blood samples were collected, and after the 2,000-m test they completed a posttest questionnaire regarding side effects and if they could identify their treatment. Pairwise comparisons were made between treatments to determine the likelihood that differences were worthwhile.


Summary of research findings:
  • There was an increase in power output and a decrease in the time it took to complete the 2,000-m test with caffeine regardless of SB ingestion.
  • SB supplementation did not appear to increase performance.
  • There was an increase in urine pH with SB supplementation compared to the placebo (6.75 ± 1.2 with SB + P2, 6.76 ± 0.95 with SB + C, and 5.94 ± 0.53 with P1 + P2).
  • All 8 subjects reported side effects from the SB, including nausea, diarrhea, and dizziness. After the caffeine, some subjects reported increased heartbeat, increased alertness, or other symptoms common with caffeine over-ingestion.

Key practice applications:

Caffeine appeared to increase activity in the central nervous system which led to an increase in performance of about 2% during the 2,000-m row. There was no observed benefit on SB ingestion without or in addition to caffeine, despite the increase in pH in the blood and the urine. This may be because the supplements were taken on an empty stomach, exacerbating gastrointestinal distress.


Limitations:

Races are not usually performed fasted, and it is known that food can affect caffeine absorption and, potentially gastrointestinal discomfort from SB. It would be interesting if this study was repeated with breakfast co-ingestion.

 

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