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Suplementação de creatina no ganho de força e hipertrofia muscular em praticantes de treinamento de força: uma breve revisão narrativa
... Asimismo, en la industria del deporte se considera una ayuda ergogénica en actividades de mayor esfuerzo, principalmente donde predomina el sistema energético Cr/CrP (Hall, Manetta & Tupper, 2021). De acuerdo con la literatura, la suplementación con CrM favorece la recuperación entre series durante el EF intenso, siendo una estrategia efectiva para aumentar el contenido muscular ( (Anugrah et al., 2024;De Faria, 2018;Jurado-Castro et al., 2021). Según Hall et al. (2021), este suplemento provee efectos ergogénicos que contribuyen al aumento de la fuerza muscular (FM), la masa magra y la función muscular; a lo que se suman beneficios neurológicos . ...
El objetivo de esta revisión fue analizar los efectos de la suplementación con creatina monohidratada (CrM) en la masa muscular (MM) y rendimiento físico en adultos jóvenes entrenados, a través de la evidencia disponible. Se efectuó una revisión sistemática, basada en protocolo PRISMA 2020, utilizando las bases de datos PubMed y Google Scholar. Se incluyeron ensayos clínicos publicados durante 2010-2023 en idioma español, inglés o portugués. Se encontraron 87 estudios, 7 aprobaron los criterios de inclusión. Estas investigaciones reportan efectos significativos de la ingesta de CrM en la MM, fuerza muscular (FM) y potencia muscular de adultos jóvenes entrenados, a corto y mediano plazo. Concluimos que la suplementación con CrM es efectiva en la mejora de la composición muscular y el rendimiento físico de adultos jóvenes entrenados. Igualmente, el momento de la ingesta es importante, con mejores resultados al ingerirla post entrenamiento. Asimismo, las cantidades sugeridas corresponden a 0.1g x kg x día o bien, 5g diarios, con efectos significativos con ambas dosis.
... Justus Liebig em 1847, confirmou a existência da creatina como um componente regular da carne. O pesquisador destacou ainda que raposas selvagens que sobreviveram à caça têm 10 vezes mais creatina em sua carne do que raposas presas, sugerindo que o trabalho muscular pode levar ao acúmulo dessa substância (Faria, 2018). Research, Society andDevelopment, v. 10, n. 14, e89101421867, 2021 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v10i14.21867 4 A função básica da creatina no corpo humano está diretamente ligada ao metabolismo energético, portanto, reservas corporais insuficientes podem limitar a função física, especialmente em atletas com formas explosivas de esportes, como levantamento de peso olímpico, futebol e basquete, ou aumentar a massa muscular como a musculação (Bouzas et al., 2015). ...
Introdução: a suplementação da creatina tem sido amplamente utilizada para melhorar o desempenho atlético. Além disso, descobertas recentes indicam que este suplemento tem um importante efeito terapêutico em muitas doenças caracterizadas por atrofia, fraqueza muscular e doenças metabólicas (músculos, ossos, pulmão e cérebro). Objetivo: analisar por meio de uma revisão da literatura os efeitos do uso crônico da creatina sobre a função renal. Metodologia: trata-se de uma revisão argumentativa da literatura, de base técnica quantitativa descritivo-exploratória. As amostras pesquisadas foram advindas de periódicos, nacionais e internacionais, publicados entre os anos de 2011 e 2021. Os periódicos foram adquiridos dos bancos de dados eletrônicos Scielo e PubMed. Resultados: Diversos estudos, a maioria realizado em homenss realizando treinamento resistido três vezes por semana foram suplementados com monohidrato de creatina em diferentes concentrações, por 7 dias e comparados com controles pareados suplementados com dextrosol. Vários testes foram realizados, em alguns deles, amostras de sangue e urina foram coletadas antes e 30 dias após a suplementação no qual inúmeros parâmetros bioquímicos e função renal foram avaliados. A suplementação de creatina monohidratada não causou eventos adversos e, como esperado, promoveu aumento do desempenho e do peso corporal. Conclusões: o presente estudo não encontrou na literatura, evidências que sustentem que a creatina pode representar um risco para a saúde de homens saudáveis. No entanto, casos na literatura sugerem que a creatina pode prejudicar a função renal com o uso indiscriminado, para não trazer riscos à saúde, recomenda-se que indivíduos saudáveis que fazem uso regular desse suplemento não ultrapassem 5g / dia.
... Quando se trata mais especificamente dos treinamentos de força e a utilização de suplementos proteicos de origem tanto animal quanto vegetal é possível afirmar que estes se apresentam como efetivos, o que favorece potencialmente o ganho de massa magra, tonificação muscular, entre outros (Faria, 2018;Souza et al., 2018;Cordeiro et al., 2018;Souza & Cargnin-Carvalho, 2018). ...
Introdução: A suplementação nutricional de proteínas se apresenta como uma necessidade importante quando se trata do treinamento de força, sendo importante o conhecimento acerca da utilização destes suplementos em consideração a sua origem, seja animal ou vegetal. Objetivo: Este estudo teve como objetivo geral analisar, através dos achados bibliográficos, a importância do uso de proteínas de origem animal e vegetal nos treinamentos de força. Metodologia: Com o levantamento bibliográfico foi possível identificar que atualmente o mercado conta com uma gama bastante diversificada de suplementos proteicos tanto de origem animal quanto vegetal, sendo os primeiros mais proeminentes em quantidade e variedade. Resultados e Discussão: Na comparação entre os resultados encontrados no que tange ao treinamento de força e os indivíduos que utilizam suplementos proteicos de origem animal e vegetal, os estudos analisados não apontaram diferença significativa entre ambos suplementos, o que indica que os dois tipos de suplementos proteicos se mostram eficazes no esperado em treinamento de força. Conclusão: não há diferença significativa nos resultados do treinamento de força considerando ambos suplementos, sendo necessário maior aprofundamento em pesquisas neste campo.
A creatina é um composto orgânico que pode ser sintetizado no corpo de forma endógena, ou pode ser obtido através da alimentação, sendo utilizada como suplemento ergogênico para a melhoria do desempenho físico e tem conquistado destaque no âmbito da musculação. O presente estudo teve o objetivo de analisar por meio de revisão de literatura o efeito do uso da creatina no desempenho de praticantes de musculação. Para o desenvolvimento do trabalho, foi realizado uma revisão de literatura integrativa, no qual tanto a análise quanto a síntese dos dados extraídos dos artigos foram realizadas de forma descritiva, possibilitando observar, contar, descrever e classificar os dados, com o intuito de reunir o conhecimento produzido sobre o tema explorado na revisão. Foram utilizados como base de busca: Google Acadêmico, PubMed e Scielo, no período de 2016 a 2024; utilizando os termos: creatina, força, hipertrofia e suplementação. Através dos artigos encontrados, após a análise dos estudos encontrados, conclui-se que a creatina é capaz de promover a maximização da força e o aumento da massa muscular, principalmente em associação ao treinamento resistido e a uma dieta balanceada.
Introdução: A creatina vem sendo cada vez mais utilizada para otimização da condição física no treinamento de força, aumento da massa muscular e associação da sua suplementação como complemento da dieta e para fins estéticos. Este estudo conterá dados baseados em pesquisa bibliográfica com o intuito de analisar as informações disponíveis sobre o tema. Trata-se de uma revisão que incluirá dados a partir da análise de informações de sites acadêmicos como Scielo e Pubmed e para integrar o conteúdo, livros e artigos da área de nutrição esportiva, serão utilizados como critérios de inclusão. Todos nortearão o desenvolvimento teórico da pesquisa apresentada de forma a abranger os temas abordados de forma descritiva. Objetivo específico: Analisar as características químicas presente na creatina, investigar os efeitos da suplementação de creatina sobre a composição corporal de praticantes de musculação, e verificar uma estratégia de dieta e suplementação aliada a prática de musculação. Objetivo geral: Apresentar a ação da creatina e seus benefícios, como suplemento durante a atividade física aliado a uma dieta equilibrada e a ação no organismo e seus benefícios como suplemento durante a atividade física, destacando os resultados obtidos com mais frequência. Conclusão: Através do desenvolvimento desta pesquisa, é possível identificar os efeitos positivos da suplementação de creatina por meio da literatura, respeitando a individualidade de cada pessoa e fazendo o uso consciente desse recurso ergogênico.
Introdução: O treinamento resistido, também conhecido como treinamento de força, tornou-se uma das formas mais populares de exercício para melhorar a aptidão física e para condicionamento de atletas. A suplementação com creatina vem sendo a principal opção entre os atletas com características de força máxima, explosiva e velocidade. Objetivo Geral: Compreender efeitos da creatina em treinamentos de força e condicionamento físico por meio dos objetivos específicos da pesquisa que são: caracterizar a creatina e suas fontes naturais; enfatizar sobre a importância do nutricionista na prescrição de suplementos na prática de treinamento de força; apontar os efeitos da suplementação com creatina no treinamento de força e na melhoria do condicionamento físico. De fato, quando associado à suplementação de creatina, o treinamento de força ou resistido tem mostrado maior benefício para o aumento de massa corporal, força máxima, aumento da capacidade de elevação de peso, aumento da massa livre de gordura e aumento das proteínas miofibrilares. Metodologia: Trata-se de uma revisão bibliográfica com abordagem descritiva. Resultado e Discussão: Para análise dos dados foi utilizada abordagem qualitativa onde a aplicação desse método considera que há uma relação dinâmica entre o mundo real e o objeto de pesquisa, que não pode ser traduzido em números. Os dados selecionados foram apresentados em forma de texto descritivo, reunindo todos os autores selecionados acerca da temática de pesquisa. Conclusão: Através do desenvolvimento desse estudo, foi possível demonstrar através da literatura, os potenciais efeitos positivos da suplementação da creatina manifesta como um futuro e propício campo de estudo.
To investigate the effect of acute changes of extracellular osmolality on whole body protein and glucose metabolism, we studied 10 male subjects during three conditions: hyperosmolality was induced by fluid restriction and intravenous infusion of hypertonic NaCl [2-5%; (wt/vol)] during 17 h; hypoosmolality was produced by intravenous administration of desmopressin, liberal water drinking, and infusion of hypotonic saline (0.4%); and the isoosmolality study consisted of ad libitum oral water intake by the subjects. Leucine flux ([1-13C]leucine infusion technique), a parameter of whole body protein breakdown, decreased during the hypoosmolality study ( P < 0.02 vs. isoosmolality). The leucine oxidation rate decreased during the hypoosmolality study ( P < 0.005 vs. isoosmolality). Metabolic clearance rate of glucose during hyperinsulinemic-euglycemic clamping increased less during the hypoosmolality study than during the isoosmolality study ( P < 0.04). Plasma insulin decreased, and plasma nonesterified fatty acids, glycerol, and ketone body concentrations and lipid oxidation increased during the hypoosmolality study. It is concluded that acute alterations of plasma osmolality influence whole body protein, glucose, and lipid metabolism; hypoosmolality results in protein sparing associated with increased lipolysis and lipid oxidation and impaired insulin sensitivity.
[Purpose] The aim of the present narrative review was to consider the evidence on the timing, optimal dose and intake duration of the main dietary supplements in sports nutrition, i.e. β-alanine, nitrate, caffeine, creatine, sodium bicarbonate, carbohydrate and protein. [Methods] This review article focuses on timing, optimal dose and intake duration of main dietary supptlements in sports nutrition. [Results] This paper reviewed the evidence to determine the optimal time, efficacy doses and intake duration for sports supplements verified by scientific evidence that report a performance enhancing effect in both situation of laboratory and training settings[Conclusion] Consumption of the supplements are usually suggested into 5 specific times, such as pre-exercise (nitrate, caffeine, sodium bicarbonate, carbohydrate and protein),
during exercise (carbohydrate), post-exercise (creatine, carbohydrate, protein), meal time (β-alanine, creatine, sodium bicarbonate, nitrate, carbohydrate and protein), and before sleep (protein). In addition, the recommended dosing protocol for the supplements nitrate and β-alanine are fixed amounts irrespective of body weight, while dosing protocol for sodium bicarbonate, caffeine and creatine supplements are related to corrected body weight (mg/kg bw). Also, intake duration is suggested for creatine and β-alanine, being effective in chronic daily time < 2 weeks while caffeine, sodium bicarbonate are effective in acute daily time (1-3 hours). Plus, ingestion of nitrate supplement is required in both chronic daily time < 28 days and acute daily time (2-2.5 h) prior exercise.
[Key words] Sports nutrition, Dietary supplements, Timing, Dose, Intake duration
Introduction: creatine supplementation is an ergogenic aid that has been used to improve
sports performance and muscular strength in high-intensity exercise. However, its effect on
improving muscle strength is still a matter of much debate among researchers. Objective: to
verify through clinical trials, the effects of creatine supplementation on muscle strength
of practitioners of weight training. Methodology: this study was a systematic
review, reported according to Prisma recommendations. The choice of key terms
happened through the Desc and Mesh. Then filters were held in major databases: Scielo;
Pubmed and Google Scholar search site, for having several items that are not indexed in
the above bases. The terms were included in the search sites, separated by Boolean
operators "And" and "Or". Results: we have selected the following eligibility criteria 10
clinical trials, and of these, nine showed significant improvements in levels of muscle
strength after intervention with creatine supplementation of practitioners of weight
training. Conclusion: creatine supplementation showed significant improvements in muscle
strength of practitioners of weight training.
Chronic supplementation with creatine monohydrate has been shown to promote increases in total intramuscular creatine, phosphocreatine, skeletal muscle mass, lean body mass and muscle fiber size. Furthermore, there is robust evidence that muscular strength and power will also increase after supplementing with creatine. However, it is not known if the timing of creatine supplementation will affect the adaptive response to exercise. Thus, the purpose of this investigation was to determine the difference between pre versus post exercise supplementation of creatine on measures of body composition and strength.
Nineteen healthy recreational male bodybuilders (mean +/- SD; age: 23.1 +/- 2.9; height: 166.0 +/- 23.2 cm; weight: 80.18 +/- 10.43 kg) participated in this study. Subjects were randomly assigned to one of the following groups: PRE-SUPP or POST-SUPP workout supplementation of creatine (5 grams). The PRE-SUPP group consumed 5 grams of creatine immediately before exercise. On the other hand, the POST-SUPP group consumed 5 grams immediately after exercise. Subjects trained on average five days per week for four weeks. Subjects consumed the supplement on the two non-training days at their convenience. Subjects performed a periodized, split-routine, bodybuilding workout five days per week (Chest-shoulders-triceps; Back-biceps, Legs, etc.). Body composition (Bod Pod(R)) and 1-RM bench press (BP) were determined. Diet logs were collected and analyzed (one random day per week; four total days analyzed).
2x2 ANOVA results - There was a significant time effect for fat-free mass (FFM) (F = 19.9; p = 0.001) and BP (F = 18.9; p < 0.001), however, fat mass (FM) and body weight did not reach significance. While there were trends, no significant interactions were found. However, using magnitude-based inference, supplementation with creatine post workout is possibly more beneficial in comparison to pre workout supplementation with regards to FFM, FM and 1-RM BP. The mean change in the PRE-SUPP and POST-SUPP groups for body weight (BW kg), FFM (kg), FM (kg) and 1-RM bench press (kg) were as follows, respectively: Mean +/- SD; BW: 0.4 +/- 2.2 vs 0.8 +/- 0.9; FFM: 0.9 +/- 1.8 vs 2.0 +/- 1.2; FM: -0.1 +/- 2.0 vs -1.2 +/- 1.6; Bench Press 1-RM: 6.6 +/- 8.2 vs 7.6 +/- 6.1.Qualitative inference represents the likelihood that the true value will have the observed magnitude. Furthermore, there were no differences in caloric or macronutrient intake between the groups.
Creatine supplementation plus resistance exercise increases fat-free mass and strength. Based on the magnitude inferences it appears that consuming creatine immediately post-workout is superior to pre-workout vis a vis body composition and strength.
RESUMO O objetivo do estudo foi comparar os efeitos da suplementação de creatina e treinamento de força periodizado sobre a composição corporal e força máxima dinâmica durante 8 semanas. Foram selecionados 27 voluntários, divididos em três grupos: placebo, suplementado com saturação e sem saturação. O treinamento se constituiu de três sessões semanais. Foram mensurados: massa corporal (kg), massa magra (kg), massa gorda (kg), percentual de gordura (%) e força máxima dinâmica no supino reto, agachamento, puxador frontal, mesa flexora, rosca direta, flexão plantar, desenvolvimento e tríceps pulley. Houve aumentos percentuais na massa corporal e massa magra, porém sem diferença entre os grupos. Foram observados aumentos significativos na força máxima no puxador frontal, rosca bíceps e tríceps pulley, sem diferenças entre os grupos. Os resultados sugerem que os dois modos de suplementação associados ao treinamento de força promovem adaptações positivas na composição corporal e força máxima dinâmica.. Palavras-chave: creatina. Treinamento de força. Composição corporal.
Creatine monohydrate (CrM) has been consistently reported to increase muscle creatine content and improve high-intensity exercise capacity. However, a number of different forms of creatine have been purported to be more efficacious than CrM. The purpose of this study was to determine if a buffered creatine monohydrate (KA) that has been purported to promote greater creatine retention and training adaptations with fewer side effects at lower doses is more efficacious than CrM supplementation in resistance-trained individuals.
In a double-blind manner, 36 resistance-trained participants (20.2 ± 2 years, 181 ± 7 cm, 82.1 ± 12 kg, and 14.7 ± 5% body fat) were randomly assigned to supplement their diet with CrM (Creapure® AlzChem AG, Trostberg, Germany) at normal loading (4 x 5 g/d for 7-days) and maintenance (5 g/d for 21-days) doses; KA (Kre-Alkalyn®, All American Pharmaceutical, Billings, MT, USA) at manufacturer's recommended doses (KA-L, 1.5 g/d for 28-days); or, KA with equivalent loading (4 x 5 g/d for 7-days) and maintenance (5 g/d) doses of CrM (KA-H). Participants were asked to maintain their current training programs and record all workouts. Muscle biopsies from the vastus lateralis, fasting blood samples, body weight, DEXA determined body composition, and Wingate Anaerobic Capacity (WAC) tests were performed at 0, 7, and 28-days while 1RM strength tests were performed at 0 and 28-days. Data were analyzed by a repeated measures multivariate analysis of variance (MANOVA) and are presented as mean ± SD changes from baseline after 7 and 28-days, respectively.
Muscle free creatine content obtained in a subgroup of 25 participants increased in all groups over time (1.4 ± 20.7 and 11.9 ± 24.0 mmol/kg DW, p = 0.03) after 7 and 28-days, respectively, with no significant differences among groups (KA-L -7.9 ± 22.3, 4.7 ± 27.0; KA-H 1.0 ± 12.8, 9.1 ± 23.2; CrM 11.3 ± 23.9, 22.3 ± 21.0 mmol/kg DW, p = 0.46). However, while no overall group differences were observed (p = 0.14), pairwise comparison between the KA-L and CrM groups revealed that changes in muscle creatine content tended to be greater in the CrM group (KA-L -1.1 ± 4.3, CrM 11.2 ± 4.3 mmol/kg DW, p = 0.053 [mean ± SEM]). Although some significant time effects were observed, no significant group x time interactions (p > 0.05) were observed in changes in body mass, fat free mass, fat mass, percent body fat, or total body water; bench press and leg press 1RM strength; WAC mean power, peak power, or total work; serum blood lipids, markers of catabolism and bone status, and serum electrolyte status; or, whole blood makers of lymphocytes and red cells. Serum creatinine levels increased in all groups (p < 0.001) with higher doses of creatine promoting greater increases in serum creatinine (p = 0.03) but the increases observed (0.1 - 0.2 mg/dl) were well within normal values for active individuals (i.e., <1.28 ± 0.2 mg/dl). Serum LDL was decreased to a greater degree following ingesting loading doses in the CrM group but returned to baseline during the maintenance phase. No side effects were reported.
Neither manufacturers recommended doses of KA (1.5 g/d) or KA with equivalent loading (20 g/d for 7-days) and maintenance doses (5 g/d for 21-days) of CrM promoted greater changes in muscle creatine content, body composition, strength, or anaerobic capacity than CrM (20 g/d for 7-days, 5 g/d for 21-days). There was no evidence that supplementing the diet with a buffered form of creatine resulted in fewer side effects than CrM. These findings do not support claims that consuming a buffered form of creatine is a more efficacious and/or safer form of creatine to consume than creatine monohydrate.
Sports nutrition is a constantly evolving field with hundreds of research papers published annually. For this reason, keeping up to date with the literature is often difficult. This paper is a five year update of the sports nutrition review article published as the lead paper to launch the JISSN in 2004 and presents a well-referenced overview of the current state of the science related to how to optimize training and athletic performance through nutrition. More specifically, this paper provides an overview of: 1.) The definitional category of ergogenic aids and dietary supplements; 2.) How dietary supplements are legally regulated; 3.) How to evaluate the scientific merit of nutritional supplements; 4.) General nutritional strategies to optimize performance and enhance recovery; and, 5.) An overview of our current understanding of the ergogenic value of nutrition and dietary supplementation in regards to weight gain, weight loss, and performance enhancement. Our hope is that ISSN members and individuals interested in sports nutrition find this review useful in their daily practice and consultation with their clients.
A creatina vem sendo muito pesquisada devido ao seu potencial efeito no rendimento físico de atletas envolvidos em exercícios de alta intensidade e curta duração, intermitentes e com curtos períodos de recuperação. A creatina fosforilada é uma reserva de energia nas células musculares. Durante um exercício intenso, a sua quebra libera energia é usada para regenerar o trifosfato de adenosina. Aproximadamente 95% do pool de creatina encontra-se na musculatura esquelética e sua regeneração após o exercício é um processo dependente de oxigênio. Estudos mostram que a suplementação com este composto pode aumentar o pool orgânico em 10 a 20%, e este percentual é maior em atletas vegetarianos (até 60%). Ainda existe controvérsia com relação aos benefícios e riscos da suplementação com esta substância. Este estudo revisa alguns dos aspectos relacionados com o metabolismo da creatina e seu uso como substância ergogênica na prática desportiva.
A cDNA has been cloned from rabbit brain that is a new member of the emerging family of Na(+)-dependent plasma membrane transporters for several neurotransmitters and structurally related compounds. Functional expression of this cDNA in COS-7 cells identifies its product as a Na(+)- and Cl(-)-dependent creatine transporter with a Km of approximately 35 microM. Its creatine transporter activity is efficiently antagonized by 3-guanidinopropionate, a well characterized alternative substrate of creatine transport in several tissues, and by 4-guanidinobutyrate. More distant structural analogues of creatine are much less efficient or inactive as antagonists, indicating a high substrate specificity of the transporter. Northern blot hybridization detects the expression of its mRNA in most tissues tested, most prominently in kidney, heart, and muscle, but not in liver and intestine. A full-length cDNA clone was also isolated from a muscle cDNA library and found to contain the same coding sequence. Substrate affinity and specificity of the cloned transporter are very similar to the endogenous creatine transporter of the COS-7 cells and to the creatine transport activities of several cell types described in the literature. Moreover, its mRNA is most abundant in the tissues known to possess high creatine uptake capacity.
Interest in creatine (Cr) as a nutritional supplement and ergogenic aid for athletes has surged over recent years. After cellular uptake, Cr is phosphorylated to phosphocreatine (PCr) by the creatine kinase (CK) reaction using ATP. At subcellular sites with high energy requirements, e.g. at the myofibrillar apparatus during muscle contraction, CK catalyzes the transphosphorylation of PCr to ADP to regenerate ATP, thus preventing a depletion of ATP levels. PCr is thus available as an immediate energy source, serving not only as an energy buffer but also as an energy transport vehicle. Ingestion of creatine increases intramuscular Cr, as well as PCr concentrations, and leads to exercise enhancement, especially in sprint performance. Additional benefits of Cr supplementation have also been noticed for high-intensity long-endurance tasks, e.g. shortening of recovery periods after physical exercise.
The present article summarizes recent findings on the influence of Cr supplementation on energy metabolism, and introduces the Cr transporter protein (CreaT), responsible for uptake of Cr into cells, as one of the key-players for the multi-faceted regulation of cellular Cr homeostasis. Furthermore, it is suggested that patients with disturbances in Cr metabolism or with different neuro-muscular diseases may benefit from Cr supplementation as an adjuvant therapy to relieve or delay the onset of symptoms. Although it is still unclear how Cr biosynthesis and transport are regulated in health and disease, so far there are no reports of harmful side effects of Cr loading in humans. However, in this study, we report that chronic Cr supplementation in rats down-regulates in vivo the expression of the CreaT. In addition, we describe the presence of CreaT isoforms most likely generated by alternative splicing.
While creatine has been known to man since 1835, when a French scientist reported finding this constitutent of meat, its presence in athletics as a performance enhancer is relatively new. Amid claims of increased power and strength, decreased performance time and increased muscle mass, creatine is being hailed as a true ergogenic aid. Creatinine is synthesised from the amino acids glycine, arginine and methionine in the kidneys, liver and pancreas, and is predominantly found in skeletal muscle, where it exists in 2 forms. Approximately 40% is in the free creatine form (Crfree), while the remaining 60% is in the phosphorylated form, creatine phosphate (CP). The daily turnover rate of approximately 2 g per day is equally met via exogenous intake and endogenous synthesis. Although creatine concentration (Cr) is greater in fast twitch muscle fibres, slow twitch fibres have a greater resynthesis capability due to their increased aerobic capacity. There appears to be no significant difference between males and females in Cr, and training does not appear to effect Cr. The 4 roles in which creatine is involved during performance are temporal energy buffering, spatial energy buffering, proton buffering and glycolysis regulation. Creatine supplementation of 20 g per day for at least 3 days has resulted in significant increases in total Cr for some individuals but not others, suggesting that there are 'responders' and 'nonresponders'. These increases in total concentration among responders is greatest in individuals who have the lowest initial total Cr, such as vegetarians. Increased concentrations of both Crfree and CP are believed to aid performance by providing more short term energy, as well as increase the rate of resynthesis during rest intervals. Creatine supplementation does not appear to aid endurance and incremental type exercises, and may even be detrimental. Studies investigating the effects of creatine supplementation on short term, high intensity exercises have reported equivocal results, with approximately equal numbers reporting significant and nonsignificant results. The only side effect associated with creatine supplementation appears to be a small increase in body mass, which is due to either water retention or increased protein synthesis.
The present study investigated the influence of creatine and protein supplementation on satellite cell frequency and number of myonuclei in human skeletal muscle during 16 weeks of heavy-resistance training. In a double-blinded design 32 healthy, male subjects (19-26 years) were assigned to strength training (STR) while receiving a timed intake of creatine (STR-CRE) (n=9), protein (STR-PRO) (n=8) or placebo (STR-CON) (n=8), or serving as a non-training control group (CON) (n=7). Supplementation was given daily (STR-CRE: 6-24 g creatine monohydrate, STR-PRO: 20 g protein, STR-CON: placebo). Furthermore, timed protein/placebo intake were administered at all training sessions. Muscle biopsies were obtained at week 0, 4, 8 (week 8 not CON) and 16 of resistance training (3 days per week). Satellite cells were identified by immunohistochemistry. Muscle mean fibre (MFA) area was determined after histochemical analysis. All training regimes were found to increase the proportion of satellite cells, but significantly greater enhancements were observed with creatine supplementation at week 4 (compared to STR-CON) and at week 8 (compared to STR-PRO and STR-CON) (P<0.01-0.05). At week 16, satellite cell number was no longer elevated in STR-CRE, while it remained elevated in STR-PRO and STR-CON. Furthermore, creatine supplementation resulted in an increased number of myonuclei per fibre and increases of 14-17% in MFA at week 4, 8 and 16 (P<0.01). In contrast, STR-PRO showed increase in MFA only in the later (16 week, +8%) and STR-CON only in the early (week 4, +14%) phases of training, respectively (P<0.05). In STR-CRE a positive relationship was found between the percentage increases in MFA and myonuclei from baseline to week 16, respectively (r=0.67, P<0.05). No changes were observed in the control group (CON). In conclusion, the present study demonstrates for the first time that creatine supplementation in combination with strength training amplifies the training-induced increase in satellite cell number and myonuclei concentration in human skeletal muscle fibres, thereby allowing an enhanced muscle fibre growth in response to strength training.
Creatine has become a popular nutritional supplement among athletes. Recent research has also suggested that there may be a number of potential therapeutic uses of creatine. This paper reviews the available research that has examined the potential ergogenic value of creatine supplementation on exercise performance and training adaptations. Review of the literature indicates that over 500 research studies have evaluated the effects of creatine supplementation on muscle physiology and/or exercise capacity in healthy, trained, and various diseased populations. Short-term creatine supplementation (e.g. 20 g/day for 5–7 days) has typically been reported to increase total creatine content by 10–30% and phosphocreatine stores by 10–40%. Of the approximately 300 studies that have evaluated the potential ergogenic value of creatine supplementation, about 70% of these studies report statistically significant results while remaining studies generally report non-significant gains in performance. No study reports a statistically significant ergolytic effect. For example, short-term creatine supplementation has been reported to improve maximal power/strength (5–15%), work performed during sets of maximal effort muscle contractions (5–15%), single-effort sprint performance (1–5%), and work performed during repetitive sprint performance (5–15%). Moreover, creatine supplementation during training has been reported to promote significantly greater gains in strength, fat free mass, and performance primarily of high intensity exercise tasks. Although not all studies report significant results, the preponderance of scientific evidence indicates that creatine supplementation appears to be a generally effective nutritional ergogenic aid for a variety of exercise tasks in a number of athletic and clinical populations.
Total cellular creatine content is an important bioenergetic parameter in skeletal muscle. To understand its regulation we investigated creatine transport and accumulation in the G8 cultured skeletal myoblast line. Like other cell types, these contain a creatine transporter, whose activity, measured using a radiolabelling technique, was saturable (Km = 110 +/- 25 microM) and largely dependent on extracellular [Na+]. To study sustained influences on steady state creatine concentration we measured total cellular creatine content using a fluorimetric method in 48 h incubations. We found that the total cellular creatine content was relatively independent of extracellular creatine concentration, consistent with high affinity sodium-dependent uptake balanced by slow passive efflux. Accordingly, in creatine-free incubations net creatine efflux was slow (5 +/- 1% of basal creatine content per day over 6 days), while creatine content in 48 h incubations was reduced by 28 +/- 13% of control by the Na+, K(+)-ATPase inhibitor ouabain. Creatine accumulation after 48 h was stimulated by treatment with the mixed alpha- and beta-adrenergic agonist noradrenaline, the beta-adrenergic agonist isoproterenol, the beta 2-agonist clenbuterol and the cAMP analogue N6,2'-O-dibutyryladenosine 3',5'-cyclic monophosphate, but was unaffected by the alpha 1 adrenergic agonist methoxamine. The noradrenaline enhancement of creatine accumulation at 48 h was inhibited by the mixed alpha- and beta-antagonist labetalol and by the beta-antagonist propranolol, but was unaffected by the alpha 2 antagonist phentolamine; greater inhibition was caused by the beta 2 antagonist butoxamine than the beta 1 antagonist atenolol. Creatine accumulation at 48 h was increased to 230 +/- 6% of control by insulin and by 140 +/- 13% by IGF-I (both at 3 nM). Creatine accumulation at 48 h was also increased to 280 +/- 40% of control by 3,3',5-triiodothyronine (at 70 microM) and to 220 +/- 35% of control by amylin (60 nM). As 3,3', 5-triiodothyronine, amylin and isoproterenol all stimulate the Na+, K(+)-ATPase, we suggest that they stimulate Na(+)-creatine cotransport indirectly by increasing the transmembrane [Na+] concentration gradient and membrane potential.
The effect of dietary creatine and supplementation on skeletal muscle creatine accumulation and subsequent degradation and on urinary creatinine excretion was investigated in 31 male subjects who ingested creatine in different quantities over varying time periods. Muscle total creatine concentration increased by approximately 20% after 6 days of creatine supplementation at a rate of 20 g/day. This elevated concentration was maintained when supplementation was continued at a rate of 2 g/day for a further 30 days. In the absence of 2 g/day supplementation, total creatine concentration gradually declined, such that 30 days after the cessation of supplementation the concentration was no different from the presupplementation value. During this period, urinary creatinine excretion was correspondingly increased. A similar, but more gradual, 20% increase in muscle total creatine concentration was observed over a period of 28 days when supplementation was undertaken at a rate of 3 g/day. In conclusion, a rapid way to "creatine load" human skeletal muscle is to ingest 20 g of creatine for 6 days. This elevated tissue concentration can then be maintained by ingestion of 2 g/day thereafter. The ingestion of 3 g creatine/day is in the long term likely to be as effective at raising tissue levels as this higher dose.
This study aimed to compare the effects of oral creatine (Cr) supplementation with creatine supplementation in combination with caffeine (Cr+C) on muscle phosphocreatine (PCr) level and performance in healthy male volunteers (n = 9). Before and after 6 days of placebo, Cr (0.5 g x kg-1 x day-1), or Cr (0.5 g x kg-1 x day-1) + C (5 mg x kg-1 x day-1) supplementation, 31P-nuclear magnetic resonance spectroscopy of the gastrocnemius muscle and a maximal intermittent exercise fatigue test of the knee extensors on an isokinetic dynamometer were performed. The exercise consisted of three consecutive maximal isometric contractions and three interval series of 90, 80, and 50 maximal voluntary contractions performed with a rest interval of 2 min between the series. Muscle ATP concentration remained constant over the three experimental conditions. Cr and Cr+C increased (P < 0.05) muscle PCr concentration by 4-6%. Dynamic torque production, however, was increased by 10-23% (P < 0.05) by Cr but was not changed by Cr+C. Torque improvement during Cr was most prominent immediately after the 2-min rest between the exercise bouts. The data show that Cr supplementation elevates muscle PCr concentration and markedly improves performance during intense intermittent exercise. This ergogenic effect, however, is completely eliminated by caffeine intake.
This study investigated the effect of carbohydrate (CHO) ingestion on skeletal muscle creatine (Cr) accumulation during Cr supplementation in humans. Muscle biopsy, urine, and plasma samples were obtained from 24 males before and after ingesting 5 g Cr in solution (group A) or 5 g Cr followed, 30 min later, by 93 g simple CHO in solution (group B) four times each day for 5 days. Supplementation resulted in an increase in muscle phosphocreatine (PCr), Cr, and total creatine (TCr; sum of PCr and Cr) concentration in groups A and B, but the increase in TCr in group B was 60% greater than in group A (P < 0.01). There was also a corresponding decrease in urinary Cr excretion in group B (P < 0.001). Creatine supplementation had no effect on serum insulin concentration, but Cr and CHO ingestion dramatically elevated insulin concentration (P < 0.001). These findings demonstrate that CHO ingestion substantially augments muscle Cr accumulation during Cr feeding in humans, which appears to be insulin mediated.
Creatine is an amino acid that plays a vital role as creatine phosphate (phosphocreatine) in regenerating adenosine triphosphate in skeletal muscle to energize muscle contraction. Oral administration increases muscle stores. During the past decade, with notable popularity this past year, creatine has assumed prominence as an ergogenic aid for professional and elite athletes. Safety issues of long-term use, however, have not been addressed satisfactorily.
The purpose of this study was to examine the effect of creatine supplementation in conjunction with resistance training on physiological adaptations including muscle fiber hypertrophy and muscle creatine accumulation.
Nineteen healthy resistance-trained men were matched and then randomly assigned in a double-blind fashion to either a creatine (N = 10) or placebo (N = 9) group. Periodized heavy resistance training was performed for 12 wk. Creatine or placebo capsules were consumed (25 g x d(-1)) for 1 wk followed by a maintenance dose (5 g x d(-1)) for the remainder of the training.
After 12 wk, significant (P < or = 0.05) increases in body mass and fat-free mass were greater in creatine (6.3% and 6.3%, respectively) than placebo (3.6% and 3.1%, respectively) subjects. After 12 wk, increases in bench press and squat were greater in creatine (24% and 32%, respectively) than placebo (16% and 24%, respectively) subjects. Compared with placebo subjects, creatine subjects demonstrated significantly greater increases in Type I (35% vs 11%), IIA (36% vs 15%), and IIAB (35% vs 6%) muscle fiber cross-sectional areas. Muscle total creatine concentrations were unchanged in placebo subjects. Muscle creatine was significantly elevated after 1 wk in creatine subjects (22%), and values remained significantly greater than placebo subjects after 12 wk. Average volume lifted in the bench press during training was significantly greater in creatine subjects during weeks 5-8. No negative side effects to the supplementation were reported.
Creatine supplementation enhanced fat-free mass, physical performance, and muscle morphology in response to heavy resistance training, presumably mediated via higher quality training sessions.
The hypothesis of this study was that short term creatine (Cr) ingestion in older individuals would increase body mass and exercise performance, as has been shown in younger subjects. Seventeen males 60-78 years old were randomly placed into two groups, Cr and placebo (P), and supplemented in double-blind fashion for 5 days. Subjects ingested either 5 g of Cr plus 1 g of sucrose 4x per day or 6 g of a sucrose placebo 4x per day. Isometric strength of the elbow flexors was assessed using a modified preacher bench attached to a strain gauge. Isokinetic exercise performance was assessed using an intermittent fatigue test of the knee extensors. Subjects performed 3 sets of 30 repetitions with 60 sec rest between sets. There was a small (0.5 kg) but statistically significant increase in body mass (p < 0.05) in the Cr group after supplementation. There was a significant overall interaction between groups in isokinetic performance from pre to post supplementation (group x time x set, p < 0.05). However, analysis of the groups separately revealed that the subjects in the Cr group demonstrated a small non-significant increase in isokinetic performance while subjects in the P group demonstrated a small non-significant performance decrement. There was no significant difference in isometric strength between groups from pre to post supplementation. These data suggest that acute oral Cr supplementation does not increase isometric strength and only produces small increases in isokinetic performance and body mass in men over the age of 60.
The goal of this review is to present a comprehensive survey of the many intriguing facets of creatine (Cr) and creatinine metabolism, encompassing the pathways and regulation of Cr biosynthesis and degradation, species and tissue distribution of the enzymes and metabolites involved, and of the inherent implications for physiology and human pathology. Very recently, a series of new discoveries have been made that are bound to have distinguished implications for bioenergetics, physiology, human pathology, and clinical diagnosis and that suggest that deregulation of the creatine kinase (CK) system is associated with a variety of diseases. Disturbances of the CK system have been observed in muscle, brain, cardiac, and renal diseases as well as in cancer. On the other hand, Cr and Cr analogs such as cyclocreatine were found to have antitumor, antiviral, and antidiabetic effects and to protect tissues from hypoxic, ischemic, neurodegenerative, or muscle damage. Oral Cr ingestion is used in sports as an ergogenic aid, and some data suggest that Cr and creatinine may be precursors of food mutagens and uremic toxins. These findings are discussed in depth, the interrelationships are outlined, and all is put into a broader context to provide a more detailed understanding of the biological functions of Cr and of the CK system.
Creatine monohydrate has become the supplement of choice for many athletes striving to improve sports performance. Recent data indicate that athletes may not be using creatine as a sports performance booster per se but instead use creatine chronically as a training aid to augment intense resistance training workouts. Although several studies have evaluated the combined effects of creatine supplementation and resistance training on muscle strength and weightlifting performance, these data have not been analyzed collectively. The purpose of this review is to evaluate the effects of creatine supplementation on muscle strength and weightlifting performance when ingested concomitant with resistance training. The effects of gender, interindividual variability, training status, and possible mechanisms of action are discussed. Of the 22 studies reviewed, the average increase in muscle strength (1, 3, or 10 repetition maximum [RM]) following creatine supplementation plus resistance training was 8% greater than the average increase in muscle strength following placebo ingestion during resistance training (20 vs. 12%). Similarly, the average increase in weightlifting performance (maximal repetitions at a given percent of maximal strength) following creatine supplementation plus resistance training was 14% greater than the average increase in weightlifting performance following placebo ingestion during resistance training (26 vs. 12%). The increase in bench press 1RM ranged from 3 to 45%, and the improvement in weightlifting performance in the bench press ranged from 16 to 43%. Thus there is substantial evidence to indicate that creatine supplementation during resistance training is more effective at increasing muscle strength and weightlifting performance than resistance training alone, although the response is highly variable.
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