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Dont forget that cyclists are not the only group of athletes who can benefit from bicarbonate supplementation. Strength trainees who spend hours in the gym and train at high intensities will also benefit!

I know that most of you are into resistance not endurance training. So, before I even get into the discussion of the experimental procedures and the results of the latest study from the Institute of Sports and Preventive Medicine at the Saarland University in Saarbrücken, Germany, I would like to point you to an older SuppVersity article which indicates that bicarbonate supplementation is able to Up Your Squat (+27%) & Bench Press (+6%) Within 60 Min" (read more).

Now that youve hopefully put away your prejudices against "that endurance supplement", lets get to the previously mentioned study by Florian Egger, Tim Meyer, Ulf Such, and Anne Hecksteden (thanks to Conrad P. Earnest for bringing this to my attention).
To investigate the effects of BICA supplementation on performance during prolonged, high-intensity cycling to exhaustion in well-trained athletes, the scientists from the Saarland University recruited 6 male and 5 female "well-trained" cyclists (mean ± SD: age 24±8 y, BMI 21.3±1.7, VO2peak 67.3±9.8 ml/kg/min - the VO2peak value tells you that they were fit ;-).

In a double-blind, randomized cross-over design, the subjects underwent two stepwise incremental exercise tests and two constant load tests (with two phases) on an electrically braked cycle ergometer (Excalibur Sport, Lode, Groningen, The Netherlands).

Figure 1: Schematic representation of the general design.Time interval between tests is specified in days (d). Data are presented as means ± standard deviation respectively, with minimum (min) and maximum (max) values (Egger. 2014).

As the overview of the study design in Figure 1 tells you, each test type was completed twice. Once after the ingestion of 0.3 g/kg sodium bicarbonate (yes, thats roughly 24g for someone who weighs 80g and should not be consumed too fast, because otherwise it may trigger diarrhea) or a placebo supplement in form of 4 g sodium chloride that was chosen to make sure that any benefits that were observed were due to the natrium, not the bicarbonate content of sodium bicarbonate.
Both the plain salt and the sodium bicarbonate were solved in 0.7 l water. The outcome measures were simple: Only if the subjects were able to pedal significantly longer until they were exhausted in the standardized constant load test, sodium bicarbonate could be considered to have practically relevant performance enhancing effects (maximum performance in the stepwise incremental exercise test, i.e. maximal workload and VO2peak were used as secondary outcomes).

Figure 2: Blood lactate (BLa) concentrations after ingestion (post drink) and during constant load tests (mean ± SD) for the BICA and placebo trials (Egger. 2014)

The other parameters the scientists measured, i.e. the blood lactate [BLa], pH, and bicarbonate concentration, were merely used determine the mechanisms for the potential improvements in exercise performance.

Speaking of auxiliary measures, if you take a look at Figure 2 you will see that the blood pH dropped significantly right after the ingestion of the bicarbonate supplement and remained "low" throughout the trial and afterwards. An observation that does not come unexpected. Previous trials have after all shown that its the ability of bicarbonate to blunt the high-intensity exercise related perturbations in both blood and muscle acid-base that keeps the maximal work rate up and leads to performance increases compared to placebo supplements.
These performance decrements are caused by the accumulation of hydrogen ions (H+) in the myoplasm and their detrimental effects on myofilament interaction, glycolytic flux and sarcoplasmatic reticulum function. As Egger et al. point out

"[t]he ability of the body to prevent or delay these force limiting processes is determined by the capacity of its intrinsic buffering systems, which counteract the accumulation of H+ both inside and outside the cell," (Egger. 2014)

which explains why the benefits of both beta alanine (which increases the intra-cellular buffering capacity) and bicarbonate are most pronounced in athletes competing in high intensity sports.

Figure 3: Time to exhaustion and maximal workload (total) and maximal workload at the individual anaerobic threshold (IAT) during the bicarbonate and placebo trials (Egger. 2014).

Apropos ergogenic effects: I already gave it away in the headline. The consumption of the bicarbonate supplement lead to immediate increases in the time to exhaustion with 49.5 ±11.5 min being the maximum in the bicarbonate and 45.0±9.5 min being the maximum in the placebo condition.

The maximal workload in the stepwise incremental tests (BICA: 341±66 W; placebo: 339±67 W) and workload at IAT (BICA: 234±5.5 W; placebo 233±5.7 W), on the other hand, did not differ significantly.
References:

• Egger F, Meyer T, Such U, Hecksteden A. "Effects of Sodium Bicarbonate on High-Intensity Endurance Performance in Cyclists: A Double-Blind, Randomized Cross-Over Trial". PLoS ONE 9.12 (2014): e114729.
• Hobson, Ruth M., et al. "Effects of ?-alanine supplementation on exercise performance: a meta-analysis." Amino acids 43.1 (2012): 25-37.

No matter what this study says, I am pretty sure that the combination of bicarbonate + beta alanine would rule for Tour de France cyclists - at least during the dreaded time-trials.

In a recent study researchers from the Victoria University and the Queensland University of Technology observed that the combination of the carnonsine pre-cursor beta alanine and sodium bicarbonate will elevate the buffering potential of skeletal muscle in eight apparently healthy, recreationally active men (26.2 ± 1.9 year; 79.8 ± 2.11 kg; 179.0 ± 2.2 cm; VO2peak 51.0 ± 2.5 ml/kg/min) by increasing muscle carnosine and blood bicarbonate levels, respectively.

So much for the good news, the bad news however is that the performance increases on a repeated sprint test were non-signficant and the expected additive effects of beta alanine and baking soda (sodium bicarbonate) during a 110% cycling capacity test were non-existing.
The trial participants were asked to complete 2 exercise tests, over consecutive days, at the end of each of the four co-supplement periods (see fig.  1).

Figure 1: Design of the study. Each trial consisted of two exercise tests performed over consecutive days. A total of 12 weeks between trials 2 and 3 was implemented to ensure adequate supplement washout time participants randomised to ingest ?-alanine during the initial chronic supplementation. MRS Magnetic resonance spectroscopy, RSA repeated sprint ability test, CCT 110 %cycling capacity test. Solid  arrows depict crossover between acute supplementation (Pl and SB). Dotted arrows depict crossover between chronic supplementation (BAl and Pl; Danaher. 2014)

During the double-blind supplementation periods, the subjects consumed capsulated ?-alanine (4.8g/day for four weeks, 6.4g/day for two weeks) or the placebo calcium carbonate (CaCO3). To investigate the superimposition of NaHCO3 (baking soda) with ?-alanine, the acute administration of NaHCO3 occurred following each of  the 6-week periods of ?-alanine and placebo supplementation.

Figure 2: The non-existing increases in peak and average performance with beta alanine and - with the exception of one outlier - bicarbonate supplementation is disappointing; value expressed relative to placebo trial.

This required two trials of either 300 mg/kg body weight sodium bicarbonate or a not wisely chosen "placebo", i.e. CaCO3 (While I have seen this repeatedly, I am asking myself how smart it really si to use calciumcarbonate as a placebo for a bicarbonate, if the carbonate will form HCO3 as soon as it is cleaved from the calcium ion?) , that was administered only once 90 min prior to the exercise bouts of the respective trials and was split into 6 equal doses over the first 50 min of the 90-min pre-exercise period.
Reference:

• Danaher, Jessica et al. "The effect of ?-alanine and NaHCO3co-ingestion on buffering capacity and exercise performance with high-intensity exercise in healthy males." Eur J Appl Physiol (2014) 114:1715–1724

Study suggests, significant increases in mitochondrial builder PGC1-a with HIIT + bicarbonate

If this is not your first visit to the SuppVersity, I am confident youve read about the ergogenic effects of sodium bicarbonate aka baking soda before. If you havent here is the short version: Sodium bicarbonate will act as a systemic acid buffer during workouts. Thats in contrast to beta-alanine which works exclusively in the muscle, but has very similar, in some studies albeit significantly more pronounced and first and foremost acute beneficial effects on exercise performance.

No loading, no waiting, no hoping. You simply wash down 20g of bicarbonate (better 0.3g/kg body weight) before the race of your life and - as long as your tummy can stomach it - see / feel the benefits during the race.
In his thesis paper, Michael E. Percival investigated the effects of bicarbonate supplementation on the cellular adaptation process in response to high intensity interval training (HIIT).

"Acute and chronic high-intensity interval exercise is a potent stimulus to influence a number of physiological adaptations with implications for health and athletic performance. [...] Due to the intense nature of this training modality and associated disturbance to muscle pH, which has been implicated in fatigue, it has been hypothesized that augmenting the body’s natural buffering capacity through nutritional means may be a strategy to augment training adaptations. One way of doing this is through the ingestion of NaHCO 3 prior to exercise, which has shown to have ergogenic effects allowing athletes to perform more work with each training session. In addition, greater mitochondrial and performance adaptations are seen when HIIT is preceded by NaHCO3 ingestion even when work is matched (Edge. 2006; Thomas. 2007; Bishop. 2010)."

Percivals goal was now to finally establish what exactly it is that gives bicarbonate the adaptational edge, so to say. To this ends, Michael E. Percival had his subjects, nine active men (22 ± 2 y; 78 ± 13 kg, VO²peak = 48 ± 8 mL/kg/min; mean ± SD) perform the same 10 x 60 s HIIT cycling protocol on two occasions, either with

• 0.2 g/kg body weight sodium bicarbonate (BICARB) or 
• an equimolar dose of a placebo, sodium chloride (PLAC),

both ingested in two equally sized doses that were ingested 30 minutes after the breakfast - a means to minimize gastrointestinal distress | and in the study at hand it worked: There was not difference in gastrointestinal complaints between placebo and bicarbonate trial.

Figure 1: Pre vs. post PGC1a and muscular glycogen content (Percival. 2014)

The two trials were separated by 1 week, the subjects had to perform their 10 all out cycling bouts at an intensity of ~263 ± 40 W - more than enough to bring all of them up to the 90%+ heart rate zone. , interspersed by 60 s of recovery. Total work during each trial was identical for a given subject.

Figure 2: Bicarbonate increases mitochondrial respiration specifically during longer-duration exercise (Bishop. 2010) - the study at hand does not just confirm the results of the previous rodent study, it does also provide information about the underlying mechanism thats responsible for the accelerated mitochondrial adaptation w/ sodium bicarbonate.

The latter is important, because otherwise the significant differences in PGC1-a expression (see Figure 1), of which the study at hand indicates that they are the most probably reason for the previously cited significant adapational benefits from bicarbonate supplementation (compare Figure 2), could be a mere function of the training volume.

Based on the data from blood draws and needle biopsies from the vastus lateralis we can now conclude that it is the increase in PGC-1? mRNA, which was increased after 3 h of recovery to a greater extent in BICARB vs. PLAC (~7- vs. 5-fold, p < 0.05) that is responsible for the enhanced adaptations after chronic supplementation.

Speaking of which, as Ive previously pointed out, I truly believe that the serial loading protocol, as described by Driller et al. (2012) is the most promising dosing scheme for the long(er)-term use of sodium bicarbonate supplements (read my write-up for more information). Issues with increasing blood pressure or calcium loss as they have been reported for very high sodium chloride intakes in susceptible individuals should, as I repeatedly pointed out, not be an issue (Luft. 1990). In pre- and post-menopausal women on high-protein diets, the addition of small amounts of sodium bicarbonate is in fact an effective way to increase calcium retention and thus any potential negative effects on bone health that may arise as a consequence of protein-induced hypercalciuria (Lutz. 1984).
References:

• Bishop, David, et al. "Induced metabolic alkalosis affects muscle metabolism and repeated-sprint ability." Medicine and science in sports and exercise 36.5 (2004): 807-813.
• Bishop, David J., et al. "Sodium bicarbonate ingestion prior to training improves mitochondrial adaptations in rats." American Journal of Physiology-Endocrinology and Metabolism 299.2 (2010): E225-E233. 
• Carr, Amelia J., Will G. Hopkins, and Christopher J. Gore. "Effects of acute alkalosis and acidosis on performance." Sports medicine 41.10 (2011): 801-814. 
• Driller, Matthew W., et al. "The effects of serial and acute NaHCO3 loading in well-trained cyclists." The Journal of Strength & Conditioning Research 26.10 (2012): 2791-2797.
• Edge, Johann, David Bishop, and Carmel Goodman. "Effects of chronic NaHCO3 ingestion during interval training on changes to muscle buffer capacity, metabolism, and short-term endurance performance." Journal of applied physiology 101.3 (2006): 918-925.
• Hollidge-Horvat, M. G., et al. "Effect of induced metabolic alkalosis on human skeletal muscle metabolism during exercise." American Journal of Physiology-Endocrinology And Metabolism 278.2 (2000): E316-E329. 
• Luft, Friedrich C., et al. "Sodium bicarbonate and sodium chloride: effects on blood pressure and electrolyte homeostasis in normal and hypertensive man." Journal of hypertension 8.7 (1990): 663-670. 
• Lutz, Josephine. "Calcium balance and acid-base status of women as affected by increased protein intake and by sodium bicarbonate ingestion." The American journal of clinical nutrition 39.2 (1984): 281-288.
• Percival, Michael E. "Sodium bicarbonate ingestion augments the increase in PGC-1? mRNA expression during recovery from intense interval exercise in human skeletal muscle." Diss. McMaster University, 2014.
• Thomas, Claire, et al. "Effects of high-intensity training on MCT1, MCT4, and NBC expressions in rat skeletal muscles: influence of chronic metabolic alkalosis." American Journal of Physiology-Endocrinology and Metabolism 293.4 (2007): E916-E922.