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Sodium Bicarbonate Ingestion and Boxing Performance

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Abstract

Boxing is a sport that consists of multiple high-intensity bouts separated by minimal recovery time and may benefit from a pre-exercise alkalotic state. The purpose of this study was to observe the ergogenic potential of sodium bicarbonate (NaHCO3) ingestion on boxing performance. Ten amateur boxers volunteered to participate in 2 competitive sparring bouts. The boxers were prematched for weight and boxing ability and consumed either 0.3 g.kg(-1) body weight (BW) of NaHCO3 (BICARB) or 0.045 g.kg(-1) BW of NaCl placebo (PLAC) mixed in diluted low calorie-flavored cordial. The sparring bouts consisted of four 3-minute rounds, each separated by 1-minute seated recovery. Blood acid-base (pH, bicarbonate [HCO3(-)], base excess [BE]), and performance (rates of perceived exertion [RPE], heart rate [HR] [HR(ave) and HR(max)], total punches landed successfully) profiles were analyzed before (where applicable) and after sparring. The results indicated a significant interaction effect for HCO3(-) (p < or = 0.001) and BE (p < 0.001), but not for pH (p = 0.48). Post hoc analysis revealed higher presparring HCO3(-) and BE for the BICARB condition, but no differences between the BICARB and PLAC conditions postsparring. There was a significant increase in punches landed during the BICARB condition (p < 0.001); however, no significant interaction effects for HRave (p = 0.15), HRmax (p = 0.32), or RPE (p = 0.38). The metabolic alkalosis induced by the NaHCO3 loading elevated before and after sparring blood buffering capacity. In practical application, the findings suggest that a standard NaHCO3 loading dose (0.3 g.kg(-1)) improves punch efficacy during 4 rounds of sparring performance.
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SODIUM BICARBONATE INGESTION AND BOXING PERFORMANCE
Siegler, Jason C;Hirscher, Kristian
Journal of Strength and Conditioning Research; Jan 2010; 24, 1; ProQuest Central
pg. 103
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
... The participants in the examined studies ranged from 16.1 to 29.9 years old, meaning that they included junior to senior athletes. The level ranged from amateur to professional in both sexes, with a majority of male athletes (n = 726) compared with female athletes (n = 78) and nondetermined gender because the studies did not report it (n = 150) [27,34,37,45,57,58,[63][64][65]69]. Most studies focussed on grappling disciplines (n = 33) , followed by striking disciplines (n = 15) [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41], mixed disciplines (n = 1) [75] and combat sports in general since they were not identified in the methodology (n = 2) [76,77]. ...
... The level ranged from amateur to professional in both sexes, with a majority of male athletes (n = 726) compared with female athletes (n = 78) and nondetermined gender because the studies did not report it (n = 150) [27,34,37,45,57,58,[63][64][65]69]. Most studies focussed on grappling disciplines (n = 33) , followed by striking disciplines (n = 15) [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41], mixed disciplines (n = 1) [75] and combat sports in general since they were not identified in the methodology (n = 2) [76,77]. In the case of NEAs, caffeine was the most evaluated supplement (n = 26) [23][24][25][26][27][28][29][30][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58] ...
... An acute dose of 0.3 g/kg of sodium bicarbonate for 1 or 3 days improved the number of throws, power and TTE in combat sports [27,[32][33][34]63]. This finding is similar to studies with racquet sports, where specific skills and TTE tended to improve [94]. ...
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Nutritional ergogenic aids (NEAs) are substances included within the group of sports supplements. Although they are widely consumed by athletes, evidence-based analysis is required to support training outcomes or competitive performance in specific disciplines. Combat sports have a predominant use of anaerobic metabolism as a source of energy, reaching peak exertion or sustained effort for very short periods of time. In this context, the use of certain NEAs could help athletes to improve their performance in those specific combat skills (i.e., the number of attacks, throws and hits; jump height; and grip strength, among others) as well as in general physical aspects (time to exhaustion [TTE], power, fatigue perception, heart rate, use of anaerobic metabolism, etc.). Medline/PubMed, Scopus and EBSCO were searched from their inception to May 2022 for randomised controlled trials (RCTs). Out of 677 articles found, 55 met the predefined inclusion criteria. Among all the studied NEAs, caffeine (5-10 mg/kg) showed strong evidence for its use in combat sports to enhance the use of glycolytic pathways for energy production during high-intensity actions due to a greater production of and tolerance to blood lactate levels. In this regard, abilities including the number of attacks, reaction time, handgrip strength, power and TTE, among others, were improved. Buffering supplements such as sodium bicarbonate, sodium citrate and beta-alanine may have a promising role in high and intermittent exertion during combat, but more studies are needed in grappling combat sports to confirm their efficacy during sustained isometric exertion. Other NEAs, including creatine, beetroot juice or glycerol, need further investigation to strengthen the evidence for performance enhancement in combat sports. Caffeine is the only NEA that has shown strong evidence for performance enhancement in combat sports.
... The mean time of sports experience of the study participants was 11.5 years (5-20) and the mean age was 20.5 years (18)(19)(20)(21)(22)(23)(24)(25)(26). The mean body mass of the samples was 81 kg (53.7-81.2). ...
... Most survey participants were experienced athletes (national or international) in their respective sports. Artioli et al. [14] analyzed judokas who had local (three), Table 1 Evaluation of studies selected by the Physiotherapy Evidence Database (PEDro) scale 1 random distribution by groups; 2 concealed allocation; 3 similarity of groups at baseline; 4 blinding of subjects; 5. blinding of therapists; 6 blindness of the evaluators; 7 data from more than 85% of subjects; 8 all subjects received the treatment or control condition; 9 statistical comparisons between groups; 10 point measures and measures of variability [17] Yes Yes Yes Yes Yes No Yes Yes Yes Yes 9 Siegler and Hirscher [18] Yes Yes Yes Yes Yes No Yes Yes Yes Yes 9 Lopes-Silva et al. [4] Yes Yes Yes Yes Yes No Yes Yes Yes Yes 9 Tobias et al. [11] Yes Yes Yes Yes Yes No Yes Yes Yes Yes 9 ↔ no. throw ↔ LA regional (two), and national (one) levels. ...
... In the studies by Durkalec-Michalski et al. [16•] and Durkalec-Michalski et al. [17], the athletes were members of the Polish wrestling team and/ or top fighters in national competitions. Siegler and Hirscher [18] analyzed 10 top boxers from a UK amateur boxing club. In Lopes-Silva et al. [4], the nine athletes were black belts in Taekwondo. ...
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Purpose of Review To verify the effects of sodium bicarbonate (NaHCO3) supplementation on biochemical and physical measurements of combat sports athletes. Recent Findings A systematic review of articles indexed in three databases (PubMed, CAPES journal, and Google Scholar) was carried out until October 2020, using descriptors related to NaHCO3 supplementation in combat sports. First, 38 articles were identified. Next, eight articles were selected through the inclusion and exclusion criteria. The methodological quality of the articles was assessed using the Physiotherapy Evidence Database (PEDro) scale (8 and 9 points). Blood lactate, rating of perceived exertion, Special Judo Fitness Test, Dummy throw, and mean and peak powers for Wingate were evaluated. Random effects meta-analysis was used, the effect size was adjusted by corrected Hedges’ g, and the heterogeneity is explored by I². The results were obtained through weighted average and 95% CI, and the significance limit was set as p < 0.05. Summary NaHCO3 supplementation had a significant effect on increasing blood lactate (p = 0.006) of the athletes studied. However, the performance measures (rating of perceived exertion, power, and specific performance) did not show a significant difference (p ˂ 0.05). In conclusion, NaHCO3 supplementation causes a significant increase in blood lactate, indicating an ergogenic effect on buffer, which can delay the onset of fatigue and contribute to the performance of combat sports athletes. New experimental studies need to be published that assess the effect of acute and chronic NaHCO3 supplementation in specific combat sports tests and in women.
... Exercise during competitions in combat sports such as kickboxing, boxing, taekwondo, and wrestling requires very good anaerobic capacity, which, as demonstrated by studies, can be improved by administering sodium bicarbonate [22][23][24]. Combat sports are also characterized by an open task structure, which means that cognitive functions must be maintained at an appropriate level during a fight [25]. The following cognitive abilities have been most often studied in combat sport athletes because the levels of these features are in a great part related to athletic skills. ...
... This sport differs from kickboxing in its task structure and variety of attacks, but the requirements for general physical fitness, technical skills, and the type of attacks using the upper limbs are very similar. Bout intensity assessed based on lactate and post-exercise changes in magnitude and direction for ABB and gas saturation in boxers [13,22] are also consistent with our findings. We also conducted our ABB and gasometry observations during the short-term recovery period. ...
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Background: Acid–base balance (ABB) is a major component of homeostasis, which is determined by the efficient functioning of many organs, including the lungs, kidneys, and liver, and the proper water and electrolyte exchange between these components. The efforts made during competitions by combat sports athletes such as kickboxers require a very good anaerobic capacity, which, as research has shown, can be improved by administering sodium bicarbonate. Combat sports are also characterized by an open task structure, which means that cognitive and executive functions must be maintained at an appropriate level during a fight. The aim of our study was to analyze the changes in ABB in capillary blood, measuring levels of H+, pCO2, pO2, HCO3􀀀, BE and total molar CO2 concentration (TCO2), which were recorded 3 and 20 min after a three-round kickboxing bout, and the level of technical and tactical skills presented during the fight. Methods: The study involved 14 kickboxers with the highest skill level (champion level). Statistical comparison of mentioned variables recorded prior to and after a bout was done with the use of Friedman’s ANOVA. Results: 3 min after a bout, H+ and pO2 were higher by 41% and 11.9%, respectively, while pCO2, HCO3􀀀, BE and TO2 were lower by 14.5%, 39.4%, 45.4% and 34.4%, respectively. Furthermore, 20 min after the bout all variables tended to normalization and they did not differ significantly compared to the baseline values. Scores in activeness of the attack significantly correlated (r = 0.64) with pre–post changes in TCO2. Conclusions: The disturbances in ABB and changes in blood oxygen and carbon dioxide saturation observed immediately after a bout indicate that anaerobic metabolism plays a large part in kickboxing fights. Anaerobic training should be included in strength and conditioning programs for kickboxers to prepare the athletes for the physiological requirements of sports combat.
... Sodium bicarbonate is a popular nutritional supplement, with studies exploring its effects on exercise performance dating back to the 1930s [1]. The effects of sodium bicarbonate supplementation have been investigated for different exercise tasks, varying in duration and intensity (e.g., high-intensity running or cycling, 200-m swimming, boxing, resistance exercise, 2000-m rowing, and repeated-sprint performance) [2][3][4][5][6][7][8][9][10][11]. However, the findings have been inconsistent, with studies reporting ergogenic, ergolytic and no significant effects [2][3][4][5][6][7][8][9][10][11]. ...
... The effects of sodium bicarbonate supplementation have been investigated for different exercise tasks, varying in duration and intensity (e.g., high-intensity running or cycling, 200-m swimming, boxing, resistance exercise, 2000-m rowing, and repeated-sprint performance) [2][3][4][5][6][7][8][9][10][11]. However, the findings have been inconsistent, with studies reporting ergogenic, ergolytic and no significant effects [2][3][4][5][6][7][8][9][10][11]. Some of the inconsistencies between findings may be due to differences in the population analyzed, sodium bicarbonate supplementation protocols, exercise protocol, and performance outcomes. ...
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Background We aimed to perform an umbrella review of meta-analyses examining the effects of sodium bicarbonate supplementation on exercise performance. Methods We systematically searched for meta-analyses that examined the effects of sodium bicarbonate supplementation on exercise performance. The methodological quality of the included reviews was evaluated using the Assessing the Methodological Quality of Systematic Reviews 2 (AMSTAR 2) checklist. Grading of Recommendations Assessment, Development, and Evaluation (GRADE) framework for downgrading the certainty in evidence was used, which included assessments of risk of bias, inconsistency, indirectness, imprecision, and publication bias. Results Eight reviews of moderate and high methodological quality met inclusion criteria. Using the GRADE framework, evidence for the ergogenic effects of sodium bicarbonate supplementation on peak and mean power in the Wingate test and Yo-Yo test performance was classified as being of moderate quality. The evidence for these outcomes did not receive a point on the indirectness GRADE item, as “serious indirectness” was detected. Low-quality evidence was found for the ergogenic effect of sodium bicarbonate supplementation on endurance events lasting ∼45 s to 8 min, muscle endurance, and 2000-m rowing performance. Evidence for these outcomes was classified as low quality, given that risk of bias, indirectness, and publication bias were assessed as “unclear”, “serious”, and “strongly suspected”, respectively. The ergogenic effects ranged from trivial (pooled effect size: 0.09) to large (pooled effect size: 1.26). Still, for most outcomes, sodium bicarbonate elicited comparable ergogenic effects. For example, sodium bicarbonate produced similar effects on performance in endurance events lasting ∼45 s to 8 min, muscle endurance tests, and Yo-Yo test (pooled effect size range: 0.36 to 0.40). No significant differences between the effects of sodium bicarbonate and placebo were found for general mean power, muscle strength, and repeated-sprint ability. Conclusion Based on meta-analyses of moderate to high quality, it can be concluded that sodium bicarbonate supplementation acutely enhances peak anaerobic power, anaerobic capacity, performance in endurance events lasting ∼45 s to 8 min, muscle endurance, 2000-m rowing performance, and high-intensity intermittent running. More research is needed among women to improve the generalizability of findings.
... Similar studies have also been conducted with athletes competing in boxing, karate, taekwondo, and wrestling [32,34,68,100,143]. In a study including amateur boxers [100], 0.3 g/kg of sodium bicarbonate ingested 60 min before exercise increased the number of punches performed during four rounds of sparring, where each round lasted 3 min with a 1-min rest interval. ...
... Similar studies have also been conducted with athletes competing in boxing, karate, taekwondo, and wrestling [32,34,68,100,143]. In a study including amateur boxers [100], 0.3 g/kg of sodium bicarbonate ingested 60 min before exercise increased the number of punches performed during four rounds of sparring, where each round lasted 3 min with a 1-min rest interval. Sodium bicarbonate ingestion also prolonged the time to fatigue during a Karate-specific aerobic test in 8 karate athletes, and it increased attack time during simulated taekwondo combat [68,143]. ...
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Based on a comprehensive review and critical analysis of the literature regarding the effects of sodium bicarbonate supplementation on exercise performance, conducted by experts in the field and selected members of the International Society of Sports Nutrition (ISSN), the following conclusions represent the official Position of the Society: 1. Supplementation with sodium bicarbonate (doses from 0.2 to 0.5 g/kg) improves performance in muscular endurance activities, various combat sports, including boxing, judo, karate, taekwondo, and wrestling, and in high-intensity cycling, running, swimming, and rowing. The ergogenic effects of sodium bicarbonate are mostly established for exercise tasks of high-intensity that last between 30 s and 12 min. 2. Sodium bicarbonate improves performance in single- and multiple-bout exercise. 3. Sodium bicarbonate improves exercise performance in both men and women. 4. For single-dose supplementation protocols, 0.2 g/kg of sodium bicarbonate seems to be the minimum dose required to experience improvements in exercise performance. The optimal dose of sodium bicarbonate dose for ergogenic effects seems to be 0.3 g/kg. Higher doses (e.g., 0.4 or 0.5 g/kg) may not be required in single-dose supplementation protocols, because they do not provide additional benefits (compared with 0.3 g/kg) and are associated with a higher incidence and severity of adverse side-effects. 5. For single-dose supplementation protocols, the recommended timing of sodium bicarbonate ingestion is between 60 and 180 min before exercise or competition. 6. Multiple-day protocols of sodium bicarbonate supplementation can be effective in improving exercise performance. The duration of these protocols is generally between 3 and 7 days before the exercise test, and a total sodium bicarbonate dose of 0.4 or 0.5 g/kg per day produces ergogenic effects. The total daily dose is commonly divided into smaller doses, ingested at multiple points throughout the day (e.g., 0.1 to 0.2 g/kg of sodium bicarbonate consumed at breakfast, lunch, and dinner). The benefit of multiple-day protocols is that they could help reduce the risk of sodium bicarbonate-induced side-effects on the day of competition. 7. Long-term use of sodium bicarbonate (e.g., before every exercise training session) may enhance training adaptations, such as increased time to fatigue and power output. 8. The most common side-effects of sodium bicarbonate supplementation are bloating, nausea, vomiting, and abdominal pain. The incidence and severity of side-effects vary between and within individuals, but it is generally low. Nonetheless, these side-effects following sodium bicarbonate supplementation may negatively impact exercise performance. Ingesting sodium bicarbonate (i) in smaller doses (e.g., 0.2 g/kg or 0.3 g/kg), (ii) around 180 min before exercise or adjusting the timing according to individual responses to side-effects, (iii) alongside a high-carbohydrate meal, and (iv) in enteric-coated capsules are possible strategies to minimize the likelihood and severity of these side-effects. 9. Combining sodium bicarbonate with creatine or beta-alanine may produce additive effects on exercise performance. It is unclear whether combining sodium bicarbonate with caffeine or nitrates produces additive benefits. 10. Sodium bicarbonate improves exercise performance primarily due to a range of its physiological effects. Still, a portion of the ergogenic effect of sodium bicarbonate seems to be placebo-driven.
... tance-based trial(Correia-Oliveira et al., 2017;Gough et al., 2019Gough et al., , 2018aGough et al., , 2018bGough et al., , 2021Deb et al., 2017;Northgraves et al., 2014;Hilton et al., 2020;Voskamp et al., 2020;Kilding et al., 2012;Callahan, Parr, Hawley, & Burke, 2017;Driller, Williams, Bellinger, Howe, & Fell, 2012b, 2012a, six studies used a time-based trial(Deb et al., 2017;Vanhatalo et al., 2010;Dalle et al., 2019;Driller, Gregory, Williams, & Fell, 2012a;McNaughton, Dalton, & Palmer, 1999;Siegler & Hirscher, 2010;Bellinger, Howe, Shing, & Fell, 2012) and only one study utilized a work-based trial(Stephens et al., 2002). ...
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This study aimed to investigate the isolated effects of NaHCO3 on cycling time-trial performance. Furthermore, we investigated whether the ingestion time of NaHCO3, standardized or individualized based on time to peak, could be effective in improving cycling time-trial performance. A systematic review was carried out on randomized placebo-controlled studies. A random-effects meta-analysis assessed the standardized mean difference (SMD) between NaHCO3 and placebo conditions. Eighteen studies were qualitatively (systematic review) and quantitatively (meta-analysis) analysed concerning mean power output (Wmean) (n = 182) and time performance (n = 201). The reviewed studies showed a low risk of bias and homogenous results for Wmean (I2 = 0%) and performance time (I2 = 0%). Overall, when compared to placebo, the NaHCO3 ingestion improved the Wmean (SMD: 0.42; 95% CI: 0.21-0.63; P = 0.001) and performance time (SMD: 0.22; 95% CI: 0.02-0.43; P = 0.03). Similarly, the NaHCO3 ingestion using a time-to-peak strategy improved the Wmean (SMD: 0.39; 95% CI: 0.03-0.75; P = 0.04; I2 = 15%) and performance time (SMD: 0.34; 95% CI: 0.07-0.61, P = 0.01, I2 = 0%). The present findings reveal that NaHCO3 ingestion has the potential to increase the overall performance time and Wmean in cycling time trials. HighlightsNaHCO3 is an effective strategy to increase cycling time-trial performance.The standardized protocol did not improve the cycling time-trial performance parameters.The individualized time-to-peak NaHCO3 ingestion has a positive effect on time and Wmean during cycling time-trial performance.
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The aim of this systematic review was to evaluate the effects of consuming sodium bicarbonate (NaHCO 3 ) and to gain insight into the nature of any changes in performance following NaHCO 3 supplementation among combat sport athletes. The analysis of the results provides compelling evidence in favor of acute or chronic NaHCO 3 supplementation as an ergogenic substance which could have an impact on several aspects of performance in judo [23, 31, 32], taekwondo [17, 20], karate [17, 33] [28, 29], wrestling [18, 19], jiu-jitsu [32] and boxing [16]. Acute or chronic NaHCO 3 supplementation is effective in the improvement of several variables of physical performance in combat sports during testing and simulated matches. Enhanced performance resulted in the increased capacity of the glycolytic system. However, the positive effects of its use are most often visible following the onset of fatigue. In addition, the use of NaHCO 3 is associated with an increased concentration of lactate in the blood. This systematic review provides data relevant for sports professionals and athletes alike regarding the use of NaHCO 3 as a supplement, prior or during training and matches.
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Nine healthy male subjects who were all participating in athletic events volunteered to take part in this study, the aim of which was to determine whether there are specific dosages of sodium bicarbonate (HCO3-) that are useful as an ergogenic aid as far as anaerobic performance times are concerned. A control, placebo (CaCO3 500 mg kg-1) and five dosages of bicarbonate (100, 200, 300, 400 and 500 mg kg-1) were used. The anaerobic test consisted of pedalling a Repco Exertech cycle ergometer for 1 min during which total work (kJ) and peak power (W) were measured. The subjects completed more work in the 200 (P < 0.05), 300, 400 and 500 mg kg-1 (P < 0.005) trials with most work being undertaken in the 300 mg kg-1 trial (41.9 kJ min-1). Peak power was not significantly different from the control until the 300 mg kg-1 dose, and there were no further changes from this with increasing doses of HCO3-. The highest level of peak power achieved was 1295 +/- 72.8 W at the 300 mg kg-1 dosage. Blood pH indicated that after ingestion of all but the 100 mg kg-1 dose, a state of alkalosis was achieved (P < 0.005), and this was also indicated by changes in base excess. Bicarbonate levels increased post-ingestion in all but the 100 mg kg-1 dose, with these changes reflecting the changes that occurred in the work output. Blood lactate (BLa) levels increased post-exercise (P < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)
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Intense muscle contractions result in large changes in the intracellular concentrations of electrolytes. The purpose of this study was to examine the contributions of changes in intracellular strong ions to calculated changes in steady-state membrane potential (Em) and muscle intracellular H+ concentration ([H+]i). A physicochemical model is used to examine the origin of the changes in [H+]i during intense muscle contraction. The study used the isolated perfused rat hindlimb intermittently stimulated to contract at high intensity for 5 min. This resulted in significant K+ depletion of both slow (soleus) and fast (white gastrocnemius, WG) muscle fibers and a release of K+ and lactate (Lac-) into venous perfusate. The major contributor to a 12- to 14-mV depolarization of Em in soleus and WG was the decrease in intracellular K+ concentration ([K+]i). The major independent contributors to [H+]i are changes in the concentrations of strong and weak ions and in CO2. Significant decreases in the strong ion difference [( SID]i) in both soleus and WG contributed substantially to the increase in [H+]i during stimulation. In WG the model showed that the decrease in [SID]i accounted for 35% of the increase in [H+]i (133-312 nequiv/L; pHi = 6.88-6.51) at the end of stimulation. Of the main contributors to decreased [SID]i, increased [Lac-]i and decreased [K+]i contributed 40 and 60%, respectively, to increased [H+]i, whereas a decrease in [PCr2-]i contributed to reduced [H+]i. It is concluded that decreased muscle [K+]i during intense contractions is the single most important contributor to reduced Em and increased [H+]i. Depletion of PCr2- simultaneous to the changes in [Lac-]i and [K+]i prevents larger increases in [H+]i and helps maintain the intracellular acid-base state.
Article
The mechanisms of lactate and pyruvate transport across the plasma membrane of rat skeletal muscle under various pH and ionic conditions were studied in skeletal muscle sarcolemmal (SL) membrane vesicles purified from 22 female Sprague-Dawley rats. Transport by SL vesicles was measured as uptake of L(+)-[U-14C] lactate and [U-14C] pyruvate. Lactate (La-) transport is pH-sensitive; stimulations to fivefold overshoot above equilibrium values were observed both directly by a proton gradient directed inward, and indirectly by a monensin- or nigericin-stimulated exchange of Na+ or K+ for H+ across the SL. Isotopic pyruvate could utilize the transporter, and demonstrated pH gradient-stimulated overshoot and cis-inhibition characteristics similar to those of lactate. Overshoot kinetics were also demonstrated by pH gradient formed by manipulation of external media at pH 5.9, 6.6, and 7.4 and intravesicular media at 6.6, 7.4, and 8.0, respectively. Carbonyl cyanide m-chlorophenylhydrazone, an H+ ionophore, was used as a "pH clamp" to return all stimulated uptake courses back to equilibrium values. Lactate uptake was depressed when internal pH was lower than external pH. These data strongly suggest that La- and H+ are either cotransported by the carrier, or transported as the undissociated HLa, and can account for the majority of the lactate uptake at pH 7.4. The mechanism does not require cotransport of either K+ or Na+. However, an inwardly directed Na+ gradient without ionophore in the absence of a pH gradient doubled La- transport; treatment with amiloride, an inhibitor of the Na+/H+ exchanger, abolished this stimulation, suggesting that this transporter may be an important coregulator of intracellular pH, and could disrupt 1:1 H+ and La- efflux stoichiometry in vivo. We conclude that the majority of La- crosses the skeletal muscle SL by a specific carrier-mediated process that is saturable at high La- concentrations, but flux is passively augmented at low intracellular pH by undissociated lactic acid. In addition, a Na+/H+ exchange mechanism was confirmed in skeletal muscle SL, does affect both lactate and proton flux, and is potentially an important coregulator of intracellular pH and thus, cellular metabolism.
Article
To study the kinetics of lactate transport in an isolated, nonmetabolizing system, skeletal muscle sarcolemmal membrane vesicles were purified from 22 female Sprague-Dawley rats. L(+)-[U-14C] Lactate at 10 concentrations demonstrated saturation kinetics with a Vmax of 139.4 nmol/mg/min, and an apparent Km of 40.1 mM. Threefold higher initial rates of L(+)-lactate uptake were seen at 37 degrees C than at 25 degrees C, indicating temperature sensitivity. Transport was stereospecific for the L(+) isomer: isotopic D(-) uptake rates remained linear at concentrations from 1 to 200 mM, and 1 mM D(-) remained 6-fold lower in net uptake after 60 min than the L(+) isomer. Furthermore, unlabeled 10 mM D(-)-lactate in the external medium could only inhibit 1 mM isotopic (L(+) uptake by 12%, whereas unlabeled 10 mM L(+)-lactate and pyruvate inhibited 82 and 71%, respectively. Additionally, 10 mM beta-hydroxybutyrate and acetoacetate could moderately inhibit (27 and 32%, respectively) 1 mM L(+)-lactate transport, but the unsubstituted aliphatic monocarboxylates (formate, acetate, propionate), tricarboxylic acid cycle intermediates (malate, succinate, oxaloacetate, alpha-ketoglutyrate, citrate), amino acids (alanine, aspartate, glutamate), and palmitate or adenosine in 10-fold excess could not effectively inhibit 1 mM L(+)lactate uptake under cis-transport conditions. 4,4'-Diisothiocyanostilbene-2,2'-disulfonic acid could inhibit L(+)-lactate transport by only 13%, so that lactate transport does not appear to be affected directly by Cl- or HCO3- fluxes. It was demonstrated that KCl could not evoke a membrane potential-induced overshoot of lactate uptake in the presence or absence of valinomycin. Moreover, gluconate could substitute for Cl-, indicating that Cl- flux does not contribute to a membrane potential-dependent component of the transport mechanism, suggesting an electroneutral translocation process. Protein-modifying reagents significantly inhibited 1 mM L(+)-lactate transport during pH-stimulated conditions (p-chloromercuriphenyl-sulfonic acid, 83%; N-ethylmaleimide, 86%; HgCl2, 56%; mersalyl, 63% inhibition). We conclude that the skeletal muscle lactate transporter is a membrane-bound protein, specifically associated with the sarcolemma, that demonstrates saturation kinetics, competition, stereospecificity, and sensitivity to temperature as well as various ionic cis-inhibitors. The lactate transporter is a potentially important regulator of lactate flux across skeletal muscle, and may help to regulate intracellular pH and intermediary metabolism during lactic acidosis.
Article
A review of the available records indicates that there have been a substantial number of fatalities in boxers due to intracranial injuries sustained in the ring in comparison to the numbers engaged at both amateur and professional levels. The number of such fatalities has decreased steadily in recent years owing to different measures taken by boxing authorities to decrease the physical hazards in the ring and to improve monitoring of boxers during bouts by referees and physicians. The considerable concern about the long-term effects of repeated brain injury as the result of boxing in producing chronic encephalopathy is adequately justified by the many studies of live boxers and pathologic examinations of brains of former boxers made and recorded over the years since 1952. These indicate clearly a significant relationship between the numbers of bouts fought and the presence of severity of chronic encephalopathy. Because it is unlikely that currently adopted protective measures will substantially reduce these hazards, even though they have apparently reduced direct fatalities, a reasonable approach to prevention would be to reduce the number and severity of blows to the head. This might be done by making any blow to the head in boxing a foul and a reason for disqualification. Another approach would be the elimination of boxing.
Lactic acid is formed and accumulated in the muscle under conditions of high energy demand, rapid fluctuations of the energy requirement and insufficient supply of O2. During intense exercise sustained to fatigue muscle pH decreases to about 6.4-6.6. Force generation does not appear to be limited by the high H+ ion concentration per se but is more related to the PCr level. Phosphofructokinase may be inhibited by high H+ concentration but the inhibition is adequately overcome by increases in the activators AMP and ADP. A high concentration of H+ will decrease PCr by a direct effect on the creatine kinase equilibrium and indirectly by an increase in ADP. The effect of acidosis on glycolysis and on the PCr level will result in a decreased rate of ADP rephosphorylation, and it is suggested that ADP increases transiently above the steady-state level in the contracting muscle fibre. It is further suggested that the function of Na-K-ATPase is impaired by the increase of ADP resulting in an altered ionic balance over the muscle cell membrane. Muscle fatigue is thus considered to be due to an insufficient rate of ADP rephosphorylation resulting in a block in the activation process or in the excitation/contraction coupling.