Multiday acute sodium bicarbonate intake improves endurance capacity and reduces acidosis in men

En ny studie fra 2013 undersøkte hvordan bikarbonat inntak flere dager før en treningsøkt kunne forbedre prestasjon og dempe acidose. De to 0,3g/kg i 5 dager. Tid før utmattelse(Tlim) økte med 23%. Bikarbonat økte også plasmavolum. Av den grunn økte ikke pH selv om bikarbonatinntaket økte. Derfor konkluderer forskerne her med at det holder å ta det dagen i forveien. Eller det viser oss at vi ikke trenger å være redd for en akkumulering av bikarbonat ved langvarig inntak. De viser også til at bikarbonat inntak bidrar til å begrense syre-overskudd i musklene ved at basisk blod trekker H+ ut. Dette øker laktat-aktivitet og dermed utholdenheten. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3623762/

«Since during multiday NaHCO3intake, a high amount of Na+ is ingested and absorbed, detrimental effects on endurance performance are possible. In fact, a higher [Na+] leads to water retention and thereby results in PV expansion 20. An increase in PV decreases blood ion concentrations, and as such results in a diminished [HCO3], which in turn could counteract the benefits associated with NaHCO3 intake. It is therefore questionable, whether [HCO3] can be increased beyond the concentration reached after the first day of supplementation on all subsequent days of supplementation. Consequently, we hypothesized that PV expands following a high Na+ intake, limiting any further increase in [HCO3], and consequently Tlim, beyond that observed after the first day of supplementation.»

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3623762/bin/1550-2783-10-16-2.jpg

«In fact, it has been shown that an increased [HCO3] gradient between the intra- and extramyocellular compartment leads to an amplified H+-efflux from the muscle cell and delays the fall in intramyocellular pH 8,14«

«A fall in intramyocellular [H+] is associated with muscle fatigue due to 1) an inhibition of glycogenolysis and glycolysis 8, 2) increased muscular K+ release, 3) lesser contractility of the heart muscle 9, 4) inhibition of the sarcoplasmatic calcium release 10 and 5) inhibition of the actin-myosin interactions 11. Thus, delaying the fall in intramyocellular pH might postpone the fatigue process and prolong intact muscle function. Indeed, our results showed that the ingestion of NaHCO3 induced metabolic alkalosis, which in turn enhanced Tlim at CP and thus improved high-intensity exercise in the range of 10 to 20 min duration.»

«As shown in this study, the NaHCO3 intervention led to an increase in [Na+] and plasma osmolality after the first bolus administration. This increase was counteracted by an expansion in PV. The increase in PV was to such an extent that pre-exercise blood [HCO3], pH, and ABE remained constant during the 5 days of testing. «

«In accordance with our results, McNaughton et al.29 found an increase in plasma [Na+] after the first of five doses of NaHCO3 but no further increase of plasma [Na+] on the following days. «

» Second, the apparent PV expansion in response to the high ion intake (see above) blunted any further increase in [HCO3]. If the same mechanism would be true for the chronic supplementation protocol, the effectiveness of this protocol should be questioned, as it seems that [HCO3] cannot be increased limitlessly, i.e. that it probably reaches a ceiling. «

«A respiratory compensation mechanism is unlikely to have occurred in our study because there were no differences between the NaHCO3 and placebo intervention for VCO2 (P = 0.903, data not shown) and RER (P = 0.556, data not shown) during the resting measurements before the constant-load tests.»

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