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1.
The Physiological Roles of Carnosine and β-Alanine in Exercising Human Skeletal Muscle.
Matthews, JJ, Artioli, GG, Turner, MD, Sale, C
Medicine and science in sports and exercise. 2019;(10):2098-2108
Abstract
Carnosine (β-alanyl-L-histidine) plays an important role in exercise performance and skeletal muscle homeostasis. Dietary supplementation with the rate-limiting precursor β-alanine leads to an increase in skeletal muscle carnosine content, which further potentiates its effects. There is significant interest in carnosine and β-alanine across athletic and clinical populations. Traditionally, attention has been given to performance outcomes with less focus on the underlying mechanism(s). Putative physiological roles in human skeletal muscle include acting as an intracellular pH buffer, modulating energy metabolism, regulating Ca handling and myofilament sensitivity, and scavenging of reactive species. Emerging evidence shows that carnosine could also act as a cytoplasmic Ca-H exchanger and form stable conjugates with exercise-induced reactive aldehydes. The enigmatic nature of carnosine means there is still much to learn regarding its actions and applications in exercise, health, and disease. In this review, we examine the research relating to each physiological role attributed to carnosine, and its precursor β-alanine, in exercising human skeletal muscle.
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Ergogenic Effects of β-Alanine Supplementation on Different Sports Modalities: Strong Evidence or Only Incipient Findings?
Brisola, GMP, Zagatto, AM
Journal of strength and conditioning research. 2019;(1):253-282
Abstract
Brisola, GMP and Zagatto, AM. Ergogenic effects of β-alanine supplementation on different sports modalities: strong evidence or only incipient findings? J Strength Cond Res 33(1): 253-282, 2019-β-Alanine supplementation is a popular nutritional ergogenic aid among the sports community. Due to its efficacy, already proven in the literature, to increase the intramuscular carnosine content (β-alanyl-L-histidine), whose main function is intramuscular buffering, β-alanine supplementation has become a nutritional strategy to improve performance, mainly in high-intensity efforts. However, although many studies present evidence of the efficacy of β-alanine supplementation in high-intensity efforts, discrepancies in outcomes are still present and the performance enhancing effects seem to be related to the specificities of each sport discipline, making it difficult for athletes/coaches to interpret the efficacy of β-alanine supplementation. Thus, this study carried out a review of the literature on this topic and summarized, analyzed, and critically discussed the findings with the objective of clarifying the current evidence found in the literature on different types of efforts and sport modalities. The present review revealed that inconsistencies are still found in aerobic parameters determined in incremental tests, except for physical working capacity at the neuromuscular fatigue threshold. Inconsistencies are also found for strength exercises and intermittent high-intensity efforts, whereas in supramaximal continuous mode intermittent exercise, the beneficial evidence is strong. In sports modalities, the evidence should be analyzed separately for each sporting modality. Thus, sports modalities that have strong evidence of the ergogenic effects of β-alanine supplementation are: cycling race of 4 km, rowing race of 2,000 m, swimming race of 100 and 200 m, combat modalities, and water polo. Finally, there is some evidence of slight additional effects on physical performance from cosupplementation with sodium bicarbonate.
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Amino acids and sport: a true love story?
Goron, A, Moinard, C
Amino acids. 2018;(8):969-980
Abstract
Among a plethora of dietary supplements, amino acids are very popular with athletes for several reasons (e.g., to prevent nutritional deficiency, improve muscle function, and decrease muscle damages) whose purpose is to improve performance. However, it is difficult to get a clear idea of which amino acids have real ergogenic impact. Here, we review and analyze the clinical studies evaluating specific amino acids (glutamine, arginine, leucine, etc.) in athletes. Only english-language clinical studies evaluating a specific effect of one amino acid were considered. Despite promising results, many studies have methodological limits or specific flaws that do not allow definitive conclusions. To date, only chronic β-alanine supplementation demonstrated an ergogenic effect in athletes. Much research is still needed to gain evidence-based data before any other specific amino acid can be recommended for use in athletes.
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Effects of beta-alanine supplementation on performance and muscle fatigue in athletes and non-athletes of different sports: a systematic review.
Berti Zanella, P, Donner Alves, F, Guerini de Souza, C
The Journal of sports medicine and physical fitness. 2017;(9):1132-1141
Abstract
INTRODUCTION Beta-alanine (BA) is a non-essential amino acid that can be synthesized in the liver and obtained from diet, particularly from white and red meat. Increased availability of BA via dietary supplement, may improve performance of athletes. The aim of this study was to conduct a review of the use of BA supplementation as an ergogenic aid to improve performance and fatigue resistance in athletes and non-athletes. EVIDENCE ACQUISITION In this systematic review, a search in PubMed and Bireme databases was performed for the terms "beta-alanine," "beta-alanine and exercise," "carnosine" or "carnosine and exercise" in the titles or abstracts. We included randomized, clinical trials published between 2005 and 2015. EVIDENCE SYNTHESIS Twenty-three studies were selected. Most of them included physically active individuals. The mean intervention period was 5.2±1.8 weeks, and mean BA dose was 4.8±1.3 g/day. The main outcome measures were blood lactate, pH, perceived exertion, power and physical working capacity at fatigue threshold. After BA supplementation, no statistically significant difference was observed in total work, exercise performance time, oxygen consumption and time to exhaustion. CONCLUSIONS BA supplementation seems to improve perceived exertion and biochemical parameters related to muscle fatigue and less evidence was found for improvement in performance.
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β-alanine supplementation to improve exercise capacity and performance: a systematic review and meta-analysis.
Saunders, B, Elliott-Sale, K, Artioli, GG, Swinton, PA, Dolan, E, Roschel, H, Sale, C, Gualano, B
British journal of sports medicine. 2017;(8):658-669
Abstract
OBJECTIVE To conduct a systematic review and meta-analysis of the evidence on the effects of β-alanine supplementation on exercise capacity and performance. DESIGN This study was designed in accordance with PRISMA guidelines. A 3-level mixed effects model was employed to model effect sizes and account for dependencies within data. DATA SOURCES 3 databases (PubMed, Google Scholar, Web of Science) were searched using a number of terms ('β-alanine' and 'Beta-alanine' combined with 'supplementation', 'exercise', 'training', 'athlete', 'performance' and 'carnosine'). ELIGIBILITY CRITERIA FOR SELECTING STUDIES Inclusion/exclusion criteria limited articles to double-blinded, placebo-controlled studies investigating the effects of β-alanine supplementation on an exercise measure. All healthy participant populations were considered, while supplementation protocols were restricted to chronic ingestion. Cross-over designs were excluded due to the long washout period for skeletal muscle carnosine following supplementation. A single outcome measure was extracted for each exercise protocol and converted to effect sizes for meta-analyses. RESULTS 40 individual studies employing 65 different exercise protocols and totalling 70 exercise measures in 1461 participants were included in the analyses. A significant overall effect size of 0.18 (95% CI 0.08 to 0.28) was shown. Meta-regression demonstrated that exercise duration significantly (p=0.004) moderated effect sizes. Subgroup analyses also identified the type of exercise as a significant (p=0.013) moderator of effect sizes within an exercise time frame of 0.5-10 min with greater effect sizes for exercise capacity (0.4998 (95% CI 0.246 to 0.753)) versus performance (0.1078 (95% CI -0.201 to 0.416)). There was no moderating effect of training status (p=0.559), intermittent or continuous exercise (p=0.436) or total amount of β-alanine ingested (p=0.438). Co-supplementation with sodium bicarbonate resulted in the largest effect size when compared with placebo (0.43 (95% CI 0.22 to 0.64)). SUMMARY/CONCLUSIONS β-alanine had a significant overall effect while subgroup analyses revealed a number of modifying factors. These data allow individuals to make informed decisions as to the likelihood of an ergogenic effect with β-alanine supplementation based on their chosen exercise modality.
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β-Alanine supplementation and military performance.
Hoffman, JR, Stout, JR, Harris, RC, Moran, DS
Amino acids. 2015;(12):2463-74
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Abstract
During sustained high-intensity military training or simulated combat exercises, significant decreases in physical performance measures are often seen. The use of dietary supplements is becoming increasingly popular among military personnel, with more than half of the US soldiers deployed or garrisoned reported to using dietary supplements. β-Alanine is a popular supplement used primarily by strength and power athletes to enhance performance, as well as training aimed at improving muscle growth, strength and power. However, there is limited research examining the efficacy of β-alanine in soldiers conducting operationally relevant tasks. The gains brought about by β-alanine use by selected competitive athletes appears to be relevant also for certain physiological demands common to military personnel during part of their training program. Medical and health personnel within the military are expected to extrapolate and implement relevant knowledge and doctrine from research performed on other population groups. The evidence supporting the use of β-alanine in competitive and recreational athletic populations suggests that similar benefits would also be observed among tactical athletes. However, recent studies in military personnel have provided direct evidence supporting the use of β-alanine supplementation for enhancing combat-specific performance. This appears to be most relevant for high-intensity activities lasting 60-300 s. Further, limited evidence has recently been presented suggesting that β-alanine supplementation may enhance cognitive function and promote resiliency during highly stressful situations.
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Evidence-based evaluation of potential benefits and safety of beta-alanine supplementation for military personnel.
Ko, R, Low Dog, T, Gorecki, DK, Cantilena, LR, Costello, RB, Evans, WJ, Hardy, ML, Jordan, SA, Maughan, RJ, Rankin, JW, et al
Nutrition reviews. 2014;(3):217-25
Abstract
This Department of Defense-sponsored evidence-based review evaluates the safety and putative outcomes of enhancement of athletic performance or improved recovery from exhaustion in studies involving beta-alanine alone or in combination with other ingredients. Beta-alanine intervention studies and review articles were collected from 13 databases, and safety information was collected from adverse event reporting portals. Due to the lack of systematic studies involving military populations, all the available literature was assessed with a subgroup analysis of studies on athletes to determine if beta-alanine would be suitable for the military. Available literature provided only limited evidence concerning the benefits of beta-alanine use, and a majority of the studies were not designed to address safety. Overall, the strength of evidence in terms of the potential for risk of bias in the quality of the available literature, consistency, directness, and precision did not support the use of beta-alanine by military personnel. The strength of evidence for a causal relation between beta-alanine and paresthesia was moderate.
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β-Alanine supplementation for athletic performance: an update.
Bellinger, PM
Journal of strength and conditioning research. 2014;(6):1751-70
Abstract
β-alanine supplementation has become a common practice among competitive athletes participating in a range of different sports. Although the mechanism by which chronic β-alanine supplementation could have an ergogenic effect is widely debated, the popular view is that β-alanine supplementation augments intramuscular carnosine content, leading to an increase in muscle buffer capacity, a delay in the onset of muscular fatigue, and a facilitated recovery during repeated bouts of high-intensity exercise. β-alanine supplementation appears to be most effective for exercise tasks that rely heavily on ATP synthesis from anaerobic glycolysis. However, research investigating its efficacy as an ergogenic aid remains equivocal, making it difficult to draw conclusions as to its effectiveness for training and competition. The aim of this review was to update, summarize, and critically evaluate the findings associated with β-alanine supplementation and exercise performance with the most recent research available to allow the development of practical recommendations for coaches and athletes. A critical review of the literature reveals that when significant ergogenic effects have been found, they have been generally shown in untrained individuals performing exercise bouts under laboratory conditions. The body of scientific data available concerning highly trained athletes performing single competition-like exercise tasks indicates that this type of population receives modest but potentially worthwhile performance benefits from β-alanine supplementation. Recent data indicate that athletes may not only be using β-alanine supplementation to enhance sports performance but also as a training aid to augment bouts of high-intensity training. β-alanine supplementation has also been shown to increase resistance training performance and training volume in team-sport athletes, which may allow for greater overload and superior adaptations compared with training alone. The ergogenic potential of β-alanine supplementation for elite athletes performing repeated high-intensity exercise bouts, either during training or during competition in sports which require repeated maximal efforts (e.g., rugby and soccer), needs scientific confirmation.
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Ergogenic effects of β-alanine and carnosine: proposed future research to quantify their efficacy.
Caruso, J, Charles, J, Unruh, K, Giebel, R, Learmonth, L, Potter, W
Nutrients. 2012;(7):585-601
Abstract
β-alanine is an amino acid that, when combined with histidine, forms the dipeptide carnosine within skeletal muscle. Carnosine and β-alanine each have multiple purposes within the human body; this review focuses on their roles as ergogenic aids to exercise performance and suggests how to best quantify the former's merits as a buffer. Carnosine normally makes a small contribution to a cell's total buffer capacity; yet β-alanine supplementation raises intracellular carnosine concentrations that in turn improve a muscle's ability to buffer protons. Numerous studies assessed the impact of oral β-alanine intake on muscle carnosine levels and exercise performance. β-alanine may best act as an ergogenic aid when metabolic acidosis is the primary factor for compromised exercise performance. Blood lactate kinetics, whereby the concentration of the metabolite is measured as it enters and leaves the vasculature over time, affords the best opportunity to assess the merits of β-alanine supplementation's ergogenic effect. Optimal β-alanine dosages have not been determined for persons of different ages, genders and nutritional/health conditions. Doses as high as 6.4 g day(-1), for ten weeks have been administered to healthy subjects. Paraesthesia is to date the only side effect from oral β-alanine ingestion. The severity and duration of paraesthesia episodes are dose-dependent. It may be unwise for persons with a history of paraesthesia to ingest β-alanine. As for any supplement, caution should be exercised with β-alanine supplementation.
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Beta-alanine supplementation in high-intensity exercise.
Harris, RC, Sale, C
Medicine and sport science. 2012;:1-17
Abstract
Glycolysis involves the oxidation of two neutral hydroxyl groups on each glycosyl (or glucosyl) unit metabolised, yielding two carboxylic acid groups. During low-intensity exercise these, along with the remainder of the carbon skeleton, are further oxidised to CO(2) and water. But during high-intensity exercise a major portion (and where blood flow is impaired, then most) is accumulated as lactate anions and H(+). The accumulation of H(+) has deleterious effects on muscle function, ultimately impairing force production and contributing to fatigue. Regulation of intracellular pH is achieved over time by export of H(+) out of the muscle, although physicochemical buffers in the muscle provide the first line of defence against H(+) accumulation. In order to be effective during high-intensity exercise, buffers need to be present in high concentrations in muscle and have pK(a)s within the intracellular exercise pH transit range. Carnosine (β-alanyl-L-histidine) is ideal for this role given that it occurs in millimolar concentrations within the skeletal muscle and has a pK(a) of 6.83. Carnosine is a cytoplasmic dipeptide formed by bonding histidine and β-alanine in a reaction catalysed by carnosine synthase, although it is the availability of β-alanine, obtained in small amounts from hepatic synthesis and potentially in greater amounts from the diet that is limiting to synthesis. Increasing muscle carnosine through increased dietary intake of β-alanine will increase the intracellular buffering capacity, which in turn might be expected to increase high-intensity exercise capacity and performance where this is pH limited. In this study we review the role of muscle carnosine as an H(+) buffer, the regulation of muscle carnosine by β-alanine, and the available evidence relating to the effects of β-alanine supplementation on muscle carnosine synthesis and the subsequent effects of this on high-intensity exercise capacity and performance.