Buffering and H+ ion dynamics in muscle tissues

Effects of serial and acute enteric-coated sodium bicarbonate supplementation on anaerobic performance, physiological profile, and metabolomics in healthy young men

Background

Previous studies have reported that sodium bicarbonate ingestion may enhance high-intensity exercise performance and cause severe gastrointestinal distress. However, enteric-coated sodium bicarbonate may reduce gastrointestinal symptoms of sodium bicarbonate after oral administration. This remains to be confirmed. This study aimed to verify the effects of serial and acute enteric-coated sodium bicarbonate supplementation on anaerobic performance, physiological profile, and metabolomics in healthy young men.

Methods

Healthy young males (n = 12) ingested 0.2 g/kg body mass of enteric-coated sodium bicarbonate (ES) in serial enteric-coated sodium bicarbonate (SES, continuous ES supplementation for 5 days) and acute enteric-coated sodium bicarbonate (AES, acute ES supplementation before exercise) or a placebo (PL) in a randomized crossover design. After each supplement protocol, the participants completed four Wingate anaerobic tests (WAT). The first three Wingate tests (testing anaerobic capacity) were performed with a 5-min passive recovery between each. After the third Wingate test, participants were required to complete a 50-min recovery followed by a fourth WAT test (testing the recovery of anaerobic capacity after 50-min intervals). Blood lactate (BLA), heart rate (HR), and ratings of perceived exertion (RPE) were measured in all conditions during the test, as was the subjective gastrointestinal–symptoms assessment questionnaire (GSAQ). Mean power (MP) and peak power (PP) were recorded after four WATs. Urine samples were collected before the test and 50 min after the 3rd WAT.

Results

Serial enteric-coated sodium bicarbonate supplementation improved anaerobic capacity in the third bout of WATs, as observed based on an increase in mean power (SES vs. PL (613 ± 57 vs. 542 ± 64 W), P = 0.024) and peak power (SES vs. PL (1,071 ± 149 vs. 905 ± 150 W), P = 0.016). Acute ES supplementation did not affect anaerobic capacity. The occurrence of gastrointestinal symptoms after enteric-coated sodium bicarbonate supplementation was minimal and no difference compared to placebo in the current study. In particular, serial enteric-coated sodium bicarbonate supplementation had no gastrointestinal side effects before the test. The AES and SES groups had a trivial effect on blood lactate compared to the PLA group. There was no significant difference in HR and RPE among the three groups. Based on targeted metabolomics analysis, the 50 min after the third WAT, the levels of lactate (P < 0.001), L-Malic acid (P < 0.05), and oxaloacetate (P < 0.05) were significantly higher in the SES group than in the PL group. Compared with the AES group, the levels of lactate and fumarate in the SES group were significantly increased (P < 0.05).

Conclusions

Our study indicates that serial enteric-coated sodium bicarbonate supplementation positively improves anaerobic performance among healthy young men. However, acute ingestion of enteric-coated sodium bicarbonate did not improve anaerobic exercise performance. Either with serial or acute supplementation doses, enteric-coated sodium bicarbonate produced fewer gastrointestinal symptoms and no difference compared to placebo, especially with no gastrointestinal side effects after serial supplementation. Serial and acute supplementation of enteric-coated sodium bicarbonate might tend to promote lactate clearance. Furthermore, serial enteric-coated sodium bicarbonate ingestion may cause changes in the metabolism of lactate, L-Malic acid, oxaloacetate, and fumarate 50 min after exercise, which presumably may promote the tricarboxylic acid cycle and lactate clearance.

The influence of progressive-chronic and acute sodium bicarbonate supplementation on anaerobic power and specific performance in team sports: a randomized, double-blind, placebo-controlled crossover study

Background

The aims of this study were to verify the effect of progressive-chronic and acute sodium bicarbonate (SB) supplementation on the anaerobic capacity, blood acid-base balance, and discipline-specific performance in team sports disciplines.

Methods

Twenty-four trained male field hockey players completed a randomized, placebo-controlled, crossover trial of either progressive-chronic (increments from 0.05 up to 0.2 g/kg) or an acute one-off dose (0.2 g/kg) supplementation protocol. Before and after treatments, athletes completed an exercise protocol that comprised of a discipline-specific field performance test conducted between two separate Wingate anaerobic tests (WAnTs).

Results

Progressive-chronic SB supplementation improved anaerobic capacity in the first bout of WAnTs, as observed based on an increase in mean power (MP: 575 ± 71 vs. 602 ± 67 W, p = 0.005, ~ + 4.7%), peak power (PP: 749 ± 94 vs. 777 ± 96 W, p = 0.002, ~ + 3.7%), power carry threshold (P_CT) at 97%_PP (727 ± 91 vs. 753 ± 93 W, p = 0.002, ~ + 3.6%) and average power over P_CT (739 ± 94 vs. 765 ± 95 W, p = 0.001, ~ + 3.5%). Acute SB supplementation had no effect on anaerobic capacity. However, an improvement in time during discipline-specific field performance test was observed after progressive-chronic (919 ± 42 vs. 912 ± 27 s, p = 0.05; ~ - 0.8%) and acute (939 ± 26 vs. 914 ± 22 s, p = 0.006, ~ 2.7%) SB supplementation. Acute SB supplementation also improved post-exercise parameters of acid-base balance (based on blood pH, bicarbonate concentration and base excess) compared to no supplementation or placebo.

Conclusions

Our study indicates that both chronic and acute SB supplementation positively supports discipline-specific performance among field hockey athletes. Moreover, the chronic protocol supported anaerobic power indices before the inset of exercise-induced fatigue but had no significant impact afterwards. However, only the acute protocol significantly affected the buffering capacity, which can be used to determine athlete's performance during high-intensity sporting events. This study design therefore highlighted that future studies focusing on sodium bicarbonate supplementation in team sports should concentrate on the efficiency of chronic and acute supplementation in varying time frames.

The Effect of Beta-Alanine versus Alkaline Agent Supplementation Combined with Branched-Chain Amino Acids and Creatine Malate in Highly-Trained Sprinters and Endurance Athletes: A Randomized Double-Blind Crossover Study

The study aimed to verify the effect of intra- (beta-alanine—BA) versus extra- (alkaline agents—ALK) cellular buffering agent supplementation, combined with customarily used branched-chain amino acids (BCAAs) and creatine malate (TCM) treatment in natural training conditions. Thirty-one elite athletes (11 sprinters and 20 endurance athletes) participated in the study. Eight-week randomized double-blind, crossover, combined supplementation with BA-ALKpla_BCAA&TCM and ALK-BApla_BCAA&TCM was implemented. In the course of the experiment, body composition, aerobic capacity, and selected blood markers were assayed. After BA-ALKpla_BCAA&TCM supplementation, total fat-free mass increased in sprinters (p = 0.009). No other differences were found in body composition, respiratory parameters, aerobic capacity, blood lactate concentration, and hematological indices after BA-ALKpla_BCAA&TCM/ALK-BApla_BCAA&TCM supplementation. The maximum post-exercise blood ammonia (NH₃) concentration decreased in both groups after BA-ALKpla_BCAA&TCM supplementation (endurance, p = 0.002; sprint, p < 0.0001). Also, lower NH₃ concentrations were observed in endurance athletes in the post-exercise recovery period. The results of our study indicate that combined BCAA, TCM, and BA supplementation is more effective than combined BCAA, TCM and ALK supplementation for an increase in fat-free mass and exercise adaptation, but not for aerobic capacity improvement. Besides, it seems that specific exercise stimuli and the training status are key factors affecting exercise performance, even in athletes using efficient supplementation.

The Effect of a New Sodium Bicarbonate Loading Regimen on Anaerobic Capacity and Wrestling Performance

Gastrointestinal side effects are the main problem with sodium bicarbonate (SB) use in sports. Therefore, our study assessed the effect of a new SB loading regimen on anaerobic capacity and wrestling performance. Fifty-eight wrestlers were randomized to either a progressive-dose regimen of up to 100 mg∙kg⁻¹ of SB or a placebo for 10 days. Before and after treatment, athletes completed an exercise protocol that comprised, in sequence, the first Wingate, dummy throw, and second Wingate tests. Blood samples were taken pre- and post-exercise. No gastrointestinal side effects were reported during the study. After SB treatment, there were no significant improvements in the outcomes of the Wingate and dummy throw tests. The only index that significantly improved with SB, compared to the placebo (p = 0.0142), was the time-to-peak power in the second Wingate test, which decreased from 3.44 ± 1.98 to 2.35 ± 1.17 s. There were also no differences in blood lactate or glucose concentrations. In conclusion, although the new loading regimen eliminated gastrointestinal symptoms, the doses could have been too small to elicit additional improvements in anaerobic power and wrestling performance. However, shortening the time-to-peak power during fatigue may be particularly valuable and is one of the variables contributing to the final success of a combat sports athlete.

The effect of chronic progressive-dose sodium bicarbonate ingestion on CrossFit-like performance: A double-blind, randomized cross-over trial

Background

Sodium bicarbonate (SB) has been proposed as an ergogenic aid, as it improves high-intensity and resistance exercise performance. However, no studies have yet investigated SB application in CrossFit. This study examined the effects of chronic, progressive-dose SB ingestion on CrossFit-like performance and aerobic capacity.

Methods

In a randomized, double-blind, cross-over trial, 21 CrossFit-trained participants were randomly allocated to 2 groups and underwent 2 trials separated by a 14-day washout period. Participants ingested either up to 150 mg∙kg^-1 of SB in a progressive-dose regimen or placebo for 10 days. Before and after each trial, Fight Gone Bad (FGB) and incremental cycling (ICT) tests were performed. In order to examine biochemical responses, blood samples were obtained prior to and 3 min after completing each exercise test.

Results

No gastrointestinal (GI) side effects were reported during the entire protocol. The overall FGB performance improved under SB by ~6.1% (p<0.001) and it was ~3.1% higher compared to post placebo (PLA_post) (p = 0.040). The number of repetitions completed in each round also improved under SB (mean from baseline: +5.8% to +6.4%). Moreover, in ICT, the time to ventilatory threshold (VT) (~8:25 min SB_post vs. ~8:00 min PLA_post, p = 0.020), workload at VT (~218 W SB_post vs. ~208 W PLA_post, p = 0.037) and heart rate at VT (~165 bpm SB_post vs. ~161 bpm PLA_post, p = 0.030) showed higher SB_post than PLA_post. Furthermore, the maximum carbon dioxide production increased under SB by ~4.8% (from ~3604 mL∙min^-1 to ~3776 mL∙min^-1, p = 0.049). Pyruvate concentration and creatine kinase activity before ICT showed higher SB_post than PLA_post (~0.32 mmol∙L^-1 vs. ~0.26 mmol∙L^-1, p = 0.001; ~275 U∙L^-1 vs. ~250 U∙L^-1, p = 0.010, respectively). However, the small sample size limits the wide-application of our results.

Conclusions

Progressive-dose SB ingestion regimen eliminated GI side effects and improved CrossFit-like performance, as well as delayed ventilatory threshold occurrence.

Nutritional Strategies to Modulate Intracellular and Extracellular Buffering Capacity During High-Intensity Exercise

Intramuscular acidosis is a contributing factor to fatigue during high-intensity exercise. Many nutritional strategies aiming to increase intra- and extracellular buffering capacity have been investigated. Among these, supplementation of beta-alanine (~3–6.4 g/day for 4 weeks or longer), the rate-limiting factor to the intramuscular synthesis of carnosine (i.e. an intracellular buffer), has been shown to result in positive effects on exercise performance in which acidosis is a contributing factor to fatigue. Furthermore, sodium bicarbonate, sodium citrate and sodium/calcium lactate supplementation have been employed in an attempt to increase the extracellular buffering capacity. Although all attempts have increased blood bicarbonate concentrations, evidence indicates that sodium bicarbonate (0.3 g/kg body mass) is the most effective in improving high-intensity exercise performance. The evidence supporting the ergogenic effects of sodium citrate and lactate remain weak. These nutritional strategies are not without side effects, as gastrointestinal distress is often associated with the effective doses of sodium bicarbonate, sodium citrate and calcium lactate. Similarly, paresthesia (i.e. tingling sensation of the skin) is currently the only known side effect associated with beta-alanine supplementation, and it is caused by the acute elevation in plasma beta-alanine concentration after a single dose of beta-alanine. Finally, the co-supplementation of beta-alanine and sodium bicarbonate may result in additive ergogenic gains during high-intensity exercise, although studies are required to investigate this combination in a wide range of sports.

Prediction of aerobic and anaerobic capacities of elite cyclists from changes in lactate during isocapnic buffering phase

This study predicted aerobic and anaerobic capacities using relative changes of arterial blood lactate during the isocapnic buffering phase (relative [La]ISBP). Fourteen male professional cyclists (sprint-trained [n = 6] and endurance [n = 8]) performed 2 exercise sessions to exhaustion on a cycle ergometer; 1 incremental standard test to determine the isocapnic buffering phase, buffering capacities, and relative [La]ISBP and 1 supramaximal exercise test to determine maximal accumulated oxygen deficit (MAOD). The time between Lactate threshold (LT) and respiratory compensatory threshold (RCT) was considered to be the isocapnic buffering phase. Total buffering capacity was calculated as Δ[La]·ΔpH. Bicarbonate buffering was calculated as Δ[HCO3]·ΔpH, and the difference between -Δ[La]·ΔpH and Δ[HCO3]·ΔpH was considered as nonbicarbonate buffering. The lactate concentration for LT (p ≤ 0.05) and RCT (p ≤ 0.05), and relative [La]ISBP (p < 0.01) were significantly lower for endurance cyclists than for sprint-trained cyclists. A significant difference was found for bicarbonate buffering capacity between groups (p < 0.01). A significant correlation was found between relative [La]ISBP with (Equation is included in full-text article.)(r = -0.71, p ≤ 0.05) and MAOD (r = 0.73, p < 0.01). Relative [La]ISBP was useful for predicting aerobic power (R = 51%) and anaerobic capacity (R = 53%). These results demonstrated that relative [La]ISBP is an important variable in intermediary metabolism and in addition to (Equation is included in full-text article.)and LT is recommended for better evaluation of performance of athletes who show nearly equal contributions from the aerobic and anaerobic energy systems during exercise.

Effects of gas exchange on acid-base balance

This paper describes the interactions between ventilation and acid-base balance under a variety of conditions including rest, exercise, altitude, pregnancy, and various muscle, respiratory, cardiac, and renal pathologies. We introduce the physicochemical approach to assessing acid-base status and demonstrate how this approach can be used to quantify the origins of acid-base disorders using examples from the literature. The relationships between chemoreceptor and metaboreceptor control of ventilation and acid-base balance summarized here for adults, youth, and in various pathological conditions. There is a dynamic interplay between disturbances in acid-base balance, that is, exercise, that affect ventilation as well as imposed or pathological disturbances of ventilation that affect acid-base balance. Interactions between ventilation and acid-base balance are highlighted for moderate- to high-intensity exercise, altitude, induced acidosis and alkalosis, pregnancy, obesity, and some pathological conditions. In many situations, complete acid-base data are lacking, indicating a need for further research aimed at elucidating mechanistic bases for relationships between alterations in acid-base state and the ventilatory responses.

Pulmonary gas exchange and acid-base balance during exercise

As the first step in the oxygen-transport chain, the lung has a critical task: optimizing the exchange of respiratory gases to maintain delivery of oxygen and the elimination of carbon dioxide. In healthy subjects, gas exchange, as evaluated by the alveolar-to-arterial PO2 difference (A-aDO2), worsens with incremental exercise, and typically reaches an A-aDO2 of approximately 25 mmHg at peak exercise. While there is great individual variability, A-aDO2 is generally largest at peak exercise in subjects with the highest peak oxygen consumption. Inert gas data has shown that the increase in A-aDO2 is explained by decreased ventilation-perfusion matching, and the development of a diffusion limitation for oxygen. Gas exchange data does not indicate the presence of right-to-left intrapulmonary shunt developing with exercise, despite recent data suggesting that large-diameter arteriovenous shunt vessels may be recruited with exercise. At the same time, multisystem mechanisms regulate systemic acid-base balance in integrative processes that involve gas exchange between tissues and the environment and simultaneous net changes in the concentrations of strong and weak ions within, and transfer between, extracellular and intracellular fluids. The physicochemical approach to acid-base balance is used to understand the contributions from independent acid-base variables to measured acid-base disturbances within contracting skeletal muscle, erythrocytes and noncontracting tissues. In muscle, the magnitude of the disturbance is proportional to the concentrations of dissociated weak acids, the rate at which acid equivalents (strong acid) accumulate and the rate at which strong base cations are added to or removed from muscle.

The teleost pseudobranch: a role for preconditioning of ocular blood supply?

The physiological relevance of the teleost pseudobranch as a remnant of a reduced gill arch is still unclear. Numerous hypotheses have been proposed regarding its physiological role, but direct confirmatory evidence is lacking. The close relationship by serial blood flow arrangement with the fish eye's choroid rete has sparked the idea that pseudobranchial preconditioning of blood pH may facilitate initiation of the Root effect and thus support the establishment of high oxygen tensions for retinal diffusive supply. This idea was critically tested by studies on isolated pseudobranchs in situ (Oncorhynchus mykiss), perfused with RBC/Ringer or RBC/plasma suspensions of widely varied composition (pH 7.4-8.2). Detailed analysis of inflowing as compared to effluent perfusates indicated normal aerobic metabolism expressed by a rise in Pco2 (+0.39 +/- 0.13 mmHg x +/- SD), an oxygen utilization of 25% and a high oxygen consumption of approximately 400 nmol g(-1 ) min(-1). Upon passage of the pseudobranch, pH (corrected for Haldane effect) was only slightly acidified (-0.03 to -0.10), [HCO3(-)] and [lactate] were slightly enhanced (+0.51 mmol l(-1) or 0.13 mmol l(-1), respectively). In order to test for yet unknown plasma components involved in pseudobranch function, a second series of experiments was conducted using RBC-suspensions in fresh plasma instead of Ringer, with results closely resembling those of the RBC/Ringer series. Lacking any physiologically significant correlation with the level of perfusate pH, the obtained data indicate pseudobranchial basic metabolic activity rather than pH regulatory characteristics. Also the observed absolute changes in pH are negligible in terms of pH regulation towards the Root-threshold. Accordingly, the present experiments as well as plausibility evaluation of mechanisms do not support the idea of blood pH pre-adjustment prior to entry into the choroid rete structure of the teleost eye to facilitate the Root-mediated oxygen release.

Lactic acid buffering, nonmetabolic CO2 and exercise hyperventilation: a critical reappraisal

It has been suggested that hyperventilation and the disproportionate increase in VCO2 versus VO2 above the ventilatory threshold (V(TH)) in ramp exercise are due to the production of nonmetabolic CO2 in muscle because of lactic acid buffering by plasma bicarbonate entering the cell in exchange with lactate [Wasserman, K., 1982. Dyspnea on exertion. Is it the heart or the lungs? JAMA 248, 2039-2043]. According to this model, plasma standard bicarbonate concentration decreases in a approximately 1:1 ratio with the increase in plasma lactate concentration, 1 mmol of CO2 is generated above that produced by aerobic metabolism for each mmol of lactic acid buffered, and nonmetabolic CO2 produced in the muscle is partly responsible for hyperventilation because of the resulting increase in the CO2 flow to the lungs. The present report shows that this model is not consistent with experimental data: (1) bicarbonate is not the main buffer in the muscle; (2) the decrease in standard bicarbonate concentration is not the mirror image of the increase in lactate concentration; (3) buffering by bicarbonate does not increase CO2 production in muscle (no nonmetabolic CO2 is produced in tissues); (4) the CO2 flow to the lungs, which should not be confused with VCO2 at the mouth, does not increase at a faster rate above than below V(TH). The disproportionate increase in VCO2 at the mouth above V(TH) is due to hyperventilation (not the reverse) and to the low plasma pH which both reduce the pool of bicarbonate readily available in the body.

Determination of pH by microfluorometry: intracellular and interstitial pH regulation in developing early-stage fish embryos (Danio rerio)

Microfluorometric techniques were applied in vivo for continuous monitoring of specific acid-base parameters in zebrafish (Danio rerio) embryos during early stages of ontogeny. Dextran-coupled pH-sensitive single-excitation/dual-emission dye SNARF-1 was pressure-injected into individual cells or the interstitial space of 16- to 256-cell embryos,and pH was continuously recorded during subsequent development for time periods of up to 8 h. A novel calibration technique was developed, essentially characterized by in vitro inorganic buffer calibration of the optical system and mathematical post-processing according to the effects of in vivo dye modifiers through a correlation established by direct comparison of optical techniques with pH microelectrodes. This approach results in high accuracy of microfluorometry, comparable with that of pH electrodes, and a recovery only limited by the physical stability of the utilized optical system.

Intracellular pH (pHi) in Danio rerio embryos between 1k-cells stage and the end of epiboly was found to be well regulated to a mean value of 7.55±0.13 (± s.d.), a range distinctly more alkaline than typical values for adult fish but in accordance with embryonic pHi of a few non-fish species shortly after fertilization. Also, interstitial pH (pHint) was significantly higher (8.08±0.25) than values for extracellular pH in adult fish. Distributions of HCO3- across membranes and between interstitium and ambient fluid compared with respective potentials strongly suggest that pH in these early stages of ontogeny is already adjusted by active transfer processes. Non-respiratory changes in ambient pH between 7.7 and 8.5 did not significantly affect pHi, a result potentially attributable to low membrane leakage rate or to the potency of active transfer mechanisms. In order to assess the pH regulatory systems more quantitatively,embryos were exposed to ambient changes of carbon dioxide partial pressure(PCO2). The direct impact of PCO2 changes on cell pH was alleviated by cell non-bicarbonate buffering and subsequent rapid, almost complete, compensation by changes in cell[HCO3-] as an expression of transmembrane transfer of acid-base relevant ions. On the basis of these results, we conclude that the regulatory potency of embryonic cells is well developed, is active to resist extensive homoiostatic stress and is efficient to maintain critical metabolism in adverse conditions, even at early stages of ontogeny.