ArticleLiterature Review

Efficacy of Alternative Forms of Creatine Supplementation on Improving Performance and Body Composition in Healthy Subjects: A Systematic Review

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Fazio, C, Elder, CL, and Harris, MM. Efficacy of alternative forms of creatine supplementation on improving performance and body composition in healthy subjects: a systematic review. J Strength Cond Res 36(9): 2663-2670, 2022-Novel forms of creatine have appeared in the marketplace with substantial claims of improved efficacy compared to creatine monohydrate (CrM). The purpose of this study was to conduct a systematic review on alternative forms of creatine to determine (a) whether they are effective ergogenic aids and (b) whether they outperform CrM. A separate comparison was conducted to determine average cost of various forms of creatine. Cochrane Central Register of Controlled Trials (CENTRAL), PubMed, Medline, and Google Scholar were systematically reviewed according to PRISMA guidelines. The design of the review was set to answer the PICOS model (subjects, interventions, comparators, outcomes, and study design). Seventeen randomized placebo controlled clinical trials examining exercise performance outcomes and body composition were included in the analysis. Magnesium-creatine chelate and creatine citrate, malate, ethyl ester, nitrate, and pyruvate were the only forms researched in the literature. Of these studies, only 3 studies compared the alternative creatine form to CrM, making it difficult to compare efficacy to CrM. There were no consistent findings of performance enhancement among alternative forms of creatine when compared to placebo. A review of the marketplace shows that CrM is the lowest cost form of creatine. Due to the paucity of studies on alternative forms of creatine as well as high prices on the market of these alternative forms, CrM remains as the most extensively studied form of creatine that shows efficacy, safety, and lowest cost to consumer.

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... There are many forms of creatine on the market, including creatine nitrate, creatine citrate, creatine ethyl ester and buffered forms of creatine, which are not bioavailable sources of creatine and are less effective [10] or more expensive than CrM [11]. CrM is the most commonly used type of creatine (CrM combines creatine and a water molecule). ...
... Although this information suggests that Cr-HCl is a beneficial ergogenic aid, more information is needed. Considering the high costs of buying Cr-HCl compared to CrM [11], it should be observed that its effects are much higher than those of CrM or that it was only a marketing claim. Therefore, the present study attempted to answer the following question: what are the effects of RT alongside Cr-HCl or CrM supplementation on anabolic/catabolic hormones, strength and body composition in young beginners? ...
... Hence, the common recommendation to dissolve creatine in acidic juice, such as orange juice, was made [6]. Based on the Fazio et al. study, market research showed that CrM is the cheapest form of creatine [11]. Therefore, according to the current research results and the effects of Cr-HCl compared to CrM, it is not economical to use and has no more effects. ...
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The purpose of this study was to determine the effects of resistance training (RT) alongside creatine-hydrochloride (Cr-HCl) or creatine monohydrate (CrM) supplementation on anabolic/catabolic hormones, strength, and body composition. Forty participants with an age range of 18-25 years were randomly divided into four groups (n=10): RT+Cr-HCl (0.03 g.kg-1 of body mass), RT+CrM-loading phase (CrM-LP) (0.3 g.kg-1 of body mass for five days (loading) and 0.03 g.kg-1 body mass for 51 days (maintenance)), RT+CrM-without loading phase (CrM-WLP) (0.03 g.kg-1 body mass), and RT+placebo (PL). The participants consumed supplements and performed RT with an intensity of 70-85 % 1RM for eight weeks. Before and after the training and supplementation period, strength (1RM), body composition (percent body fat (PBF), skeletal muscle mass (SMM), muscular cross-sectional area (MCSA)) and serum levels of testosterone, growth hormone (GH), insulin-like growth factor-1 (IGF-1), cortisol, adrenocorticotropic hormone (ACTH), follistatin and myostatin were measured. The results showed that in the supplementation groups, strength, arm and thigh MCSA, and SMM significantly increased, and PBF significantly decreased (P≤0.05); this change was significant compared to the PL group (P≤0.05). In addition, the results showed a significant increase in GH, IGF-1 levels, the ratio of follistatin/myostatin, testosterone/cortisol (P≤0.05), and a significant decrease in cortisol and ACTH levels (P≤0.05) in the supplementation groups. Hormonal changes in GH, IGF-1, testosterone/cortisol, cortisol, and ACTH levels in the supplementation groups were significant compared to the PL group (P≤0.05). The results showed that CrM and Cr-HCl significantly enhanced the beneficial effects of RT on strength, hypertrophy, and hormonal responses, with Cr-HCl showing no benefit over CrM.
... Creatine supplementation is commonly reported to enhance short-duration, high-intensity activities and promote increased gains in strength, muscle mass, bone mineral density, and neuromuscular function [136]. During short-duration, high-intensity activities, energy for ATP resynthesis is supplied from the breakdown of PCr and anaerobic glycolysis [138]. In addition to increasing concentrations of circulating free creatine and maximising PCr stores within skeletal muscle cells [138], creatine supplementation can also enhance the efficiency of ATP utilisation, subsequently increasing anaerobic power production [138]. ...
... During short-duration, high-intensity activities, energy for ATP resynthesis is supplied from the breakdown of PCr and anaerobic glycolysis [138]. In addition to increasing concentrations of circulating free creatine and maximising PCr stores within skeletal muscle cells [138], creatine supplementation can also enhance the efficiency of ATP utilisation, subsequently increasing anaerobic power production [138]. ...
... During short-duration, high-intensity activities, energy for ATP resynthesis is supplied from the breakdown of PCr and anaerobic glycolysis [138]. In addition to increasing concentrations of circulating free creatine and maximising PCr stores within skeletal muscle cells [138], creatine supplementation can also enhance the efficiency of ATP utilisation, subsequently increasing anaerobic power production [138]. ...
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Global warming is attributed to an increased frequency of high ambient temperatures and humidity, elevating the prevalence of high-temperature-related illness and death. Evidence over recent decades highlights that tailored nutritional strategies are essential to improve performance and optimise health during acute and chronic exertional-heat exposure. Therefore, the purpose of this review is to discuss the efficacy of various nutritional strategies and ergogenic aids on responses during and following acute and chronic exertional-heat exposure. An outline is provided surrounding the application of various nutritional practices (e.g., carbohydrate loading, fluid replacement strategies) and ergogenic aids (e.g., caffeine, creatine, nitrate, tyrosine) to improve physiological, cognitive, and recovery responses to acute exertional-heat exposure. Additionally, this review will evaluate if the magnitude and time course of chronic heat adaptations can be modified with tailored supplementation practices. This review highlights that there is robust evidence for the use of certain ergogenic aids and nutritional strategies to improve performance and health outcomes during exertional-heat exposure. However, equivocal findings across studies appear dependent on factors such as exercise testing modality, duration, and intensity; outcome measures in relation to the ergogenic aid’s proposed mechanism of action; and sex-specific responses. Collectively, this review provides evidence-based recommendations and highlights areas for future research that have the potential to assist with prescribing specific nutritional strategies and ergogenic aids in populations frequently exercising in the heat. Future research is required to establish dose-, sex-, and exercise-modality-specific responses to various nutritional practices and ergogenic aid use for acute and chronic exertional-heat exposure.
... Creatine is synthesized endogenously by the transfer of the amidino group of L-arginine to the N α -amine group of L-glycine that is catalyzed by L-arginine-glycine amidinotransferase to yield ornithine and guanidinoacetate (GAA); GAA is then methylated by guanidinoacetate N-methyltransferase with S-adenosyl methionine to form creatine [5,23,35,37,52]. Although creatine is not a traditional proteinogenic amino acid [35], it is frequently referred to as an amino acid in the literature [1,5,13,26,36,66] because it is a non-proteinogenic amino acid similar to ornithine, citrulline, and homoserine [5,7,40,45]. In a general sense, an amino acid can be any organic compound that contains both an amino group and carboxylic group [40]. ...
... Similar to some types of CM, research on the efficacy and safety of these novel/alternative forms of creatine is also lacking as relatively few studies have been performed to study their safety and/or effectiveness [26,35]. To this point, a recent review by Fazio et al. compared the effects of magnesium-creatine chelate, creatine citrate, creatine malate, CEE, creatine nitrate, and creatine pyruvate and reported no consistent findings for performance enhancement among the alternative forms of creatine when compared to a placebo [13]. Additionally, Kreider and colleagues published 2 papers in the last 11 years on the bioavailability, efficacy, safety, and regulatory status of novel forms of creatine and pointed to the lack of scientific evidence to support the manufacturers' marketing claims [26,35]. ...
... Indeed, Kreider et al. discuss that the scientific basis and regulatory status of alternative forms of creatine is not clear and continues to be common in the sports supplement industry [35]. This is in spite of the 2011 review paper on novel forms of creatine co-authored by Kreider and colleagues [26], other publications that have discussed alternative forms of creatine over the last 15 þ years [1,9,13,36,58,65], and the fact that some forms of creatine are still available today as stand-alone products (e.g., creatine serum) that have been reported to be ineffective in research studies [3,20,38]. ...
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Creatine monohydrate (CM) is an established and effective dietary supplement, but it is not the only form of creatine. We analyzed forms of creatine for sale on Amazon.com" title="http://Amazon.com">Amazon.com and evaluated if the advertised claims are supported by the available scientific evidence. We also analyzed the cost per gram of the forms of creatine. A total of 175 creatine supplements were included and we reported the total creatine content per serving, form(s) of creatine in products, product claims, and prevalence of products third party certified. The identified products contained 16 forms of creatine other than CM. The prevalence of products containing functional ingredients with CM or forms of creatine was 29.7%, and the prevalence of products containing blends of different forms of creatine was 21.7%. Only 8% of products were third party certified. The products using only CM (n=91) had a mean price per gram of 0.12±0.08,whereasproductsusingonlyotherformsofcreatine(n=32)hadameanpricepergramof0.12 ± 0.08, whereas products using only other forms of creatine (n=32) had a mean price per gram of 0.26 ± 0.17. Approximately 88% of alternative creatine products in this study are classified as having limited to no evidence to support bioavailability, efficacy, and safety.
... The critical role of creatine in rapid energy production results in approximately 95% of the body's creatine being stored in skeletal muscle [4]. Within the muscle, approximately 40% of creatine is in the free form and the remaining 60% is in the phosphorylated form as PCr [5]. Significant levels of creatine have also been found in other cells of the body, such as neurons, cardiomyocytes, and hepatocytes [6,7]. ...
... Creatine monohydrate is a widely investigated and effective form of creatine used to increase the body's stores of creatine, primarily in muscle tissue. Overall, creatine monohydrate supplementation is popular in fitness, sports, and some clinical settings due to its effectiveness, affordability, and high bioavailability compared to other creatine forms [5]. The most popular supplementation protocol with creatine monohydrate involves loading with 0.3 g/kg/day for 5 to 7 days, followed by a maintenance dose of 0.03 g/kg/day, typically for 4 to 6 weeks. ...
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Creatine monohydrate supplementation is widely used by athletes in high-intensity, power-based sports due to its ability to enhance short-term performance by increasing intramuscular phosphocreatine (PCr) stores, which aid in ATP resynthesis during intense muscle contractions. However, emerging evidence suggests that creatine monohydrate offers benefits beyond athletic performance. This narrative review explores the literature supporting the advantages of creatine supplementation in women, vegans, and clinical populations. In women, who typically have lower baseline intramuscular creatine levels, supplementation may help alleviate fatigue-related symptoms associated with the menstrual cycle, particularly during the early follicular and luteal phases. For vegans and vegetarians, who often have reduced creatine stores due to the absence of creatine-rich animal products in their diet, supplementation can improve both physical and cognitive performance while supporting adherence to plant-based diets. Additionally, creatine supplementation holds potential for various clinical populations. It may mitigate muscle wasting in conditions such as sarcopenia and cachexia, support neuroprotection in neurodegenerative diseases such as Parkinson’s and Huntington’s, improve exercise capacity in cardiovascular diseases, and enhance energy metabolism in chronic fatigue syndrome. Creatine may also aid recovery from traumatic brain injury by promoting brain energy metabolism and reducing neuronal damage. In conclusion, creatine monohydrate supplementation can enhance physical performance, cognitive function, and overall health in women, vegans, and clinical populations by addressing creatine deficiencies, improving energy metabolism, and supporting recovery from physical and neurological challenges. Most available evidence supports the effectiveness of creatine monohydrate, which should be considered the preferred form of creatine supplementation over other variants. Additionally, proper creatine dosing is essential to maximize benefits and minimize potential adverse effects that may arise from chronic ingestion of excessively high doses.
... Due to the claims of the improved effectiveness of Cr-HCl, this supplement is often sold at a much higher cost. The cost-effectiveness of CrM is estimated at an average of $0.29 per five-gram serving, and the exaggerated cost of Cr-HCl is $1.1 per five-gram serving [48]. The results of the present study also show that Cr-HCl does not have a greater effect than CrM, and considering its high price, it does not seem to be justified to use this type of supplement. ...
... There is currently no evidence to support its use as a substitute for CrM, and more research is needed to determine if alternative forms of creatine are potentially more effective or just cost more to purchase. Overall, CrM remains the most effective and cost-effective form of creatine [48]. ...
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This study aimed to compare the effect of creatine hydrochloride (Cr-HCl) and creatine monohydrate (CrM) supplementation alongside resistance training (RT) on oxidative stress, muscle damage, performance, and body composition in soldiers. In this research, 36 male soldiers aged 18–28 years voluntarily participated in the study. Participants were randomly divided into three groups (n = 12): 1- RT + Cr-HCl, 2- RT + CrM, and 3- RT + placebo (PL). The participants performed RT with an intensity of 70–85% 1RM for eight weeks (three days a week). Also, during this period, they used Cr-HCl and CrM supplements. Before and after supplementation and training periods, body composition (percent body fat (PBF) and skeletal muscle mass (SMM)), performance (muscular strength, muscular endurance and power), blood sample (total antioxidant capacity (TAC), superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA), lactate dehydrogenase (LDH), Creatine kinase (CK)) were taken. The results showed that muscle strength, muscle endurance, power and SMM increased while PBF decreased in the RT + Cr-HCl and RT + CrM groups compared to the PL group (P ≤ 0.05). In addition, regarding antioxidant indices changes, the results showed decreased MDA and increased SOD in RT + Cr-HCl and RT + CrM groups compared to the RT + PL group (P ≤ 0.05). However, no significant group × time interactions were noted for levels of LDH and CK (P > 0.05). In general, the results showed that Cr-HCl and CrM, along with RT can positively affect oxidative stress, performance and body composition of soldiers, but it does not affect muscle damage indicators. According to the results, Cr-HCl does not cause more effects than CrM.
... Although various activities and considerations interact to achieve this end, many people turn to various exercise and nutritional strategies to augment performance (i.e., enhanced muscular strength, power, and force) [1,2]. One of the most commonly used and scientifically supported ergogenic aids is creatine monohydrate (commonly referred to as creatine) [1,[3][4][5]. Creatine is an amino acid found in relatively high concentrations in skeletal muscle. Since 1992, when the first reports emerged that exogenous creatine monohydrate supplementation increases intramuscular phosphocreatine (PCr) stores [6], and shortly afterwards, when these increases were inextricably linked to augmented exercise performance [7,8], the ability of creatine to function as an ergogenic aid has attracted great interest. ...
... Although several other forms of creatine have been proposed and marketed as alternatives, none have been shown to offer benefits above and beyond those seen with monohydrate. In this respect, a number of studies have been completed comparing various alternative forms of creatine, and the interested reader is directed to the following papers: [3][4][5]30,[159][160][161][162][163]. In this respect, one must also realize that several studies have sought to examine the impact of combining creatine with other ingredients, such as beta-alanine [164,165], beta-hydroxy-beta-methylbutyrate (HMB) [96,[166][167][168][169][170][171], glutamine [72], sodium bicarbonate [47], carbohydrates [22,44,99,172,173], and protein [22,59,99] to examine the potential for any synergistic outcomes. ...
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Creatine is one of the most studied and popular ergogenic aids for athletes and recreational weightlifters seeking to improve sport and exercise performance, augment exercise training adaptations, and mitigate recovery time. Studies consistently reveal that creatine supplementation exerts positive ergogenic effects on single and multiple bouts of short-duration, high-intensity exercise activities, in addition to potentiating exercise training adaptations. In this respect, supplementation consistently demonstrates the ability to enlarge the pool of intracellular creatine, leading to an amplification of the cell’s ability to resynthesize adenosine triphosphate. This intracellular expansion is associated with several performance outcomes, including increases in maximal strength (low-speed strength), maximal work output, power production (high-speed strength), sprint performance, and fat-free mass. Additionally, creatine supplementation may speed up recovery time between bouts of intense exercise by mitigating muscle damage and promoting the faster recovery of lost force-production potential. Conversely, contradictory findings exist in the literature regarding the potential ergogenic benefits of creatine during intermittent and continuous endurance-type exercise, as well as in those athletic tasks where an increase in body mass may hinder enhanced performance. The purpose of this review was to summarize the existing literature surrounding the efficacy of creatine supplementation on exercise and sports performance, along with recovery factors in healthy populations.
... However, CRM presents some limitations such as low solubility in water, transportability issues, and heterogeneous response among individuals (non-responders) 1 . To overcome these limitations, researchers are studying studied other novel formats of CRM 3 . Despite the emergence of various alternative forms of this product, none of them have yet surpassed the efficacy of CRM in enhancing muscle uptake and high-intensity exercise performance 4 . ...
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This study investigates the impact of Guanidinoacetic Acid (GAA) supplementation in basketball, a high-intensity sport requiring optimal nutrition and recovery strategies. Ergogenic aids like Creatine (CRM) are common, but GAA, a creatine precursor, may be more beneficial. Involving 31 semi-professional male and female players, the study compared GAA, CRM, and placebo groups. Results showed significant physical performance improvements in females using GAA, particularly in Counter Movement Jump (CMJ) and Handgrip (HG). Male GAA users showed CMJ improvements, while CRM enhanced cognitive functions in males. The study suggests GAA’s potential in enhancing physical performance, especially in women, and highlights the need for further research on GAA and CRM effects, considering gender differences.
... However, in humans using recommended doses of creatine (0.075-0.18 grams/kg/day for 2 months), there appears to be no adverse effects on creatine transporter protein content or mRNA expression 47 . Lastly, it is important to note that creatine monohydrate is nearly 100% absorbed and alternative forms of creatine, despite marketing claims, lack any evidence of superiority 48 . Creatine is not stable in a solution and rapidly degrades to creatinine; therefore, beverages containing creatine are not effective at raising plasma creatine levels 49 . ...
... This is important in the context of physically active people at all ages. Furthermore, important health benefits may be provided by habitual, low dietary creatine ingestion (e.g., 3 g/day) throughout the lifespan (Fazio et al., 2022;Kreider et al., 2017). This is a crucial health factor for physically active people. ...
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Few supplements have a scientifically proven ergogenic effects of improving exercise capacity and/or physical performance in sport. The athletes require specialised nutrition, including precisely good quality supplementation, i.e. scientifically tested. Nowadays, more and more athletes use nutritional supplementation to improve their sporting performance both at the elite and non-elite levels. In this review, ergogenic substances such as the β-alanine, caffeine, creatine monohydrate, creatine malate, sodium bicarbonate were analysed among athletes/active people from an exercise and health capacity perspective. The aim of this review is to analyse the efficacy, mechanisms of action, dosage, side effects of the selected ergogenic substances, among athletes involved in physical effort/specific sport disciplines. Furthermore, the article will show the benefits of using these supplements in terms of health as well as improvement of exercise capacity among athletes.
... The critical flaw of this investigation lies in the dosage of CM (C 4 H 11 N 3 O 3 ) and CLL (C 10 H 20 N 4 O 3 ) provided to the participants. Creatine, while not a traditional proteinogenic amino acid, is frequently referred to as an amino acid in the literature (Antonio et al., 2021;Bonilla et al., 2021;Fazio et al., 2022) because it can be considered a nonproteinogenic amino acid similar to ornithine, citrulline, and homoserine (Brosnan & Brosnan, 2007;Lu & Freeland, 2006;Ostojic, 2021). In a general sense, an amino acid can be any organic compound that contains both an amino group and a carboxyl group (Lu & Freeland, 2006). ...
... Ergogenic aids are commonly used to improve performance or augment exercise training adaptations (1,2). Creatine monohydrate (1,(3)(4)(5)(6) supplementation is well-established for its ability to increase intramuscular creatine concentration and its subsequent ergogenic potential as seen by commonly reported increases in fat-free mass accretion, augmented muscle morphology changes, and improvements in muscular strength, endurance, and power (3,7,8). Altering the timing of when nutrients are delivered has been established as a potential strategy to augment recovery from stressful exercise while also impacting adaptations to regular exercise training (9). ...
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Background Limited research is available on the potential impact of creatine monohydrate administration before or after workouts among athletes. This study aimed to investigate the effects of pre- vs. post-exercise creatine monohydrate supplementation on resistance training adaptations and body composition. Methods In a randomized, double-blind, placebo-controlled, parallel design, 34 healthy resistance-trained male and female athletes were randomly assigned and matched according to fat free mass to consume a placebo, or 5-g dose of creatine monohydrate within 1 h before training, or within 1 h after training for 8 weeks, while completing a weekly resistance training program. Participants co-ingested 25-gram doses of both whey protein isolate and maltodextrin along with each assigned supplement dose. Body composition, muscular strength, and endurance, along with isometric mid-thigh pull were assessed before and after the 8-week supplementation period. A 3 × 2 mixed factorial (group x time) ANOVA with repeated measures on time were used to evaluate differences. Results All groups experienced similar and statistically significant increases in fat free mass (+1.34 ± 3.48 kg, p = 0.04), upper (+2.21 ± 5.69 kg, p = 0.04) and lower body strength (+7.32 ± 10.01 kg, p < 0.001), and decreases in body mass (−1.09 ± 2.71 kg, p = 0.03), fat mass (−2.64 ± 4.16 kg, p = 0.001), and percent body fat (−2.85 ± 4.39 kg, p < 0.001). Conclusions The timing of creatine monohydrate did not exert any additional influence over the measured outcomes.
Article
Despite the overwhelming number of sports supplements on the market, only seven are currently recognized as effective. Biological functions are largely regulated through redox reactions, yet no comprehensive analysis of the redox properties of these supplements has been compiled. Here, we analyze the redox characteristics of these seven supplements: bicarbonates, beta- alanine, caffeine, creatine, nitrates, carbohydrates, and proteins. Our findings suggest that all sports supplements exhibit some degree of redox activity. However, the precise physiological implications of these redox properties remain unclear. Future research, employing unconventional perspectives and methodologies, will reveal new redox pixels of the exercise physiology and sports nutrition picture.
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Background Despite the robust evidence demonstrating positive effects from creatine supplementation (primarily when associated with resistance training) on measures of body composition, there is a lack of a comprehensive evaluation regarding the influence of creatine protocol parameters (including dose and form) on body mass and estimates of fat-free and fat mass. Methods Randomized controlled trials (RCTs) evaluating the effect of creatine supplementation on body composition were included. Electronic databases, including PubMed, Web of Science, and Scopus were searched up to July 2023. Heterogeneity tests were performed. Random effect models were assessed based on the heterogeneity tests, and pooled data were examined to determine the weighted mean difference (WMD) with a 95% confidence interval (CI). Results From 4831 initial records, a total of 143 studies met the inclusion criteria. Creatine supplementation increased body mass (WMD: 0.86 kg; 95% CI: 0.76 to 0.96, I² = 0%) and fat-free mass (WMD: 0.82 kg; 95% CI: 0.57 to 1.06, I² = 0%) while reducing body fat percentage (WMD: −0.28 %; 95% CI: −0.47 to −0.09; I² = 0%). Studies that incorporated a maintenance dose of creatine or performed resistance training in conjunction with supplementation had greater effects on body composition. Conclusion Creatine supplementation has a small effect on body mass and estimates of fat-free mass and body fat percentage. These findings were more robust when combined with resistance training.
Article
Context: Many clinicians, trainers, and athletes do not have a true understanding of the effects of commonly used performance-enhancing drugs (PEDs) on performance and health. Objective: To provide an evidence-based review of 7 commonly used pharmacological interventions for performance enhancement in athletes. Data sources: PubMed and Scopus databases were searched on April 8, 2022. Study selection: Systematic reviews (SRs) and meta-analyses (MAs) assessing the performance-enhancing effects of the following interventions were included: androgenic anabolic steroids (AAS), growth hormone (GH), selective androgen receptor modulators (SARMs), creatine, angiotensin-converting enzyme (ACE)-inhibitors, recombinant human erythropoietin (rHuEPO), and cannabis. Study design: Umbrella review of SRs and MAs. Level of evidence: Level 4. Data extraction: Primary outcomes collected were (1) body mass, (2) muscle strength, (3) performance, and (4) recovery. Adverse effects were also noted. Results: A total of 27 papers evaluating 5 pharmacological interventions met inclusion criteria. No studies evaluating SARMs or ACE-inhibitors were included. AAS lead to a 5% to 52% increase in strength and a 0.62 standard mean difference in lean body mass with subsequent lipid derangements. GH alters body composition, without providing a strength or performance benefit, but potential risks include soft tissue edema, fatigue, arthralgias, and carpel tunnel syndrome. Creatine use during resistance training can safely increase total and lean body mass, strength, and performance in high-intensity, short-duration, repetitive tasks. Limited evidence supports rHuEPO benefit on performance despite increases in both VO2max and maximal power output, and severe cardiovascular risks are documented. Cannabis provides no performance benefit and may even impair athletic performance. Conclusion: In young healthy persons and athletes, creatine can safely provide a performance-enhancing benefit when taken in controlled doses. AAS, GH, and rHuEPO are associated with severe adverse events and do not support a performance benefit, despite showing the ability to change bodily composition, strength, and/or physiologic measures. Cannabis may have an ergolytic, instead of ergogenic, effect.
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Key points The mechanisms for the age‐related increase in fatigability during dynamic exercise remain elusive. We tested whether age‐related impairments in muscle oxidative capacity would result in a greater accumulation of fatigue causing metabolites, inorganic phosphate (Pi), hydrogen (H⁺) and diprotonated phosphate (H2PO4⁻), in the muscle of old compared to young adults during a dynamic knee extension exercise. The age‐related increase in fatigability (reduction in mechanical power) of the knee extensors was closely associated with a greater accumulation of metabolites within the working muscle but could not be explained by age‐related differences in muscle oxidative capacity. These data suggest that the increased fatigability in old adults during dynamic exercise is primarily determined by age‐related impairments in skeletal muscle bioenergetics that result in a greater accumulation of metabolites. Abstract The present study aimed to determine whether the increased fatigability in old adults during dynamic exercise is associated with age‐related differences in skeletal muscle bioenergetics. Phosphorus nuclear magnetic resonance spectroscopy was used to quantify concentrations of high‐energy phosphates and pH in the knee extensors of seven young (22.7 ± 1.2 years; six women) and eight old adults (76.4 ± 6.0 years; seven women). Muscle oxidative capacity was measured from the phosphocreatine (PCr) recovery kinetics following a 24 s maximal voluntary isometric contraction. The fatiguing exercise consisted of 120 maximal velocity contractions (one contraction per 2 s) against a load equivalent to 20% of the maximal voluntary isometric contraction. The PCr recovery kinetics did not differ between young and old adults (0.023 ± 0.007 s−1 vs. 0.019 ± 0.004 s⁻¹, respectively). Fatigability (reductions in mechanical power) of the knee extensors was ∼1.8‐fold greater with age and was accompanied by a greater decrease in pH (young = 6.73 ± 0.09, old = 6.61 ± 0.04) and increases in concentrations of inorganic phosphate, [Pi], (young = 22.7 ± 4.8 mm, old = 32.3 ± 3.6 mm) and diprotonated phosphate, [H2PO4⁻], (young = 11.7 ± 3.6 mm, old = 18.6 ± 2.1 mm) at the end of the exercise in old compared to young adults. The age‐related increase in power loss during the fatiguing exercise was strongly associated with intracellular pH (r = –0.837), [Pi] (r = 0.917) and [H2PO4⁻] (r = 0.930) at the end of the exercise. These data suggest that the age‐related increase in fatigability during dynamic exercise has a bioenergetic basis and is explained by an increased accumulation of metabolites within the muscle.
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We report the case of a renal transplant recipient presenting with elevated serum creatinine levels whilst taking oral creatine ethyl ester (CEE), but not creatine monohydrate (CM). Standard investigations for allograft dysfunction, including Doppler ultrasound and renal biopsy, were normal. Serum creatinine normalized following cessation of the supplement. CM is poorly absorbed and does not affect creatinine. In contrast, CEE is converted and absorbed as creatinine, elevating serum levels. In such cases, creatinine is not a valid surrogate for glomerular filtration rate (GFR). Alternate methods of GFR measurement should be considered and a rigorous clinical and drug history taken.
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In a double-blind, crossover, randomized and placebo-controlled trial; 28 men and women ingested a placebo (PLA), 3 g of creatine nitrate (CNL), and 6 g of creatine nitrate (CNH) for 6 days. Participants repeated the experiment with the alternate supplements after a 7-day washout. Hemodynamic responses to a postural challenge, fasting blood samples, and bench press, leg press, and cycling time trial performance and recovery were assessed. Data were analyzed by univariate, multivariate, and repeated measures general linear models (GLM). No significant differences were found among treatments for hemodynamic responses, clinical blood markers or self-reported side effects. After 5 days of supplementation, one repetition maximum (1RM) bench press improved significantly for CNH (mean change, 95% CI; 6.1 [3.5, 8.7] kg) but not PLA (0.7 [−1.6, 3.0] kg or CNL (2.0 [−0.9, 4.9] kg, CNH, p = 0.01). CNH participants also tended to experience an attenuated loss in 1RM strength during the recovery performance tests following supplementation on day 5 (PLA: −9.3 [−13.5, −5.0], CNL: −9.3 [−13.5, −5.1], CNH: −3.9 [−6.6, −1.2] kg, p = 0.07). After 5 days, pre-supplementation 1RM leg press values increased significantly, only with CNH (24.7 [8.8, 40.6] kg, but not PLA (13.9 [−15.7, 43.5] or CNL (14.6 [−0.5, 29.7]). Further, post-supplementation 1RM leg press recovery did not decrease significantly for CNH (−13.3 [−31.9, 5.3], but did for PLA (−30.5 [−53.4, −7.7] and CNL (−29.0 [−49.5, −8.4]). CNL treatment promoted an increase in bench press repetitions at 70% of 1RM during recovery on day 5 (PLA: 0.4 [−0.8, 1.6], CNL: 0.9 [0.35, 1.5], CNH: 0.5 [−0.2, 0.3], p = 0.56), greater leg press endurance prior to supplementation on day 5 (PLA: −0.2 [−1.6, 1.2], CNL: 0.9 [0.2, 1.6], CNH: 0.2 [−0.5, 0.9], p = 0.25) and greater leg press endurance during recovery on day 5 (PLA: −0.03 [−1.2, 1.1], CNL: 1.1 [0.3, 1.9], CNH: 0.4 [−0.4, 1.2], p = 0.23). Cycling time trial performance (4 km) was not affected. Results indicate that creatine nitrate supplementation, up to a 6 g dose, for 6 days, appears to be safe and provide some ergogenic benefit.
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Creatine is one of the most popular nutritional ergogenic aids for athletes. Studies have consistently shown that creatine supplementation increases intramuscular creatine concentrations which may help explain the observed improvements in high intensity exercise performance leading to greater training adaptations. In addition to athletic and exercise improvement, research has shown that creatine supplementation may enhance post-exercise recovery, injury prevention, thermoregulation, rehabilitation, and concussion and/or spinal cord neuroprotection. Additionally, a number of clinical applications of creatine supplementation have been studied involving neurodegenerative diseases (e.g., muscular dystrophy, Parkinson’s, Huntington’s disease), diabetes, osteoarthritis, fibromyalgia, aging, brain and heart ischemia, adolescent depression, and pregnancy. These studies provide a large body of evidence that creatine can not only improve exercise performance, but can play a role in preventing and/or reducing the severity of injury, enhancing rehabilitation from injuries, and helping athletes tolerate heavy training loads. Additionally, researchers have identified a number of potentially beneficial clinical uses of creatine supplementation. These studies show that short and long-term supplementation (up to 30 g/day for 5 years) is safe and well-tolerated in healthy individuals and in a number of patient populations ranging from infants to the elderly. Moreover, significant health benefits may be provided by ensuring habitual low dietary creatine ingestion (e.g., 3 g/day) throughout the lifespan. The purpose of this review is to provide an update to the current literature regarding the role and safety of creatine supplementation in exercise, sport, and medicine and to update the position stand of International Society of Sports Nutrition (ISSN).
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Creatine monohydrate (CrM) and nitrate are popular supplements for improving exercise performance; yet have not been investigated in combination. We performed two studies to determine the safety and exercise performance-characteristics of creatine nitrate (CrN) supplementation. Study 1 participants (N = 13) ingested 1.5 g CrN (CrN-Low), 3 g CrN (CrN-High), 5 g CrM or a placebo in a randomized, crossover study (7d washout) to determine supplement safety (hepatorenal and muscle enzymes, heart rate, blood pressure and side effects) measured at time-0 (unsupplemented), 30-min, and then hourly for 5-h post-ingestion. Study 2 participants (N = 48) received the same CrN treatments vs. 3 g CrM in a randomized, double-blind, 28d trial inclusive of a 7-d interim testing period and loading sequence (4 servings/d). Day-7 and d-28 measured Tendo™ bench press performance, Wingate testing and a 6x6-s bicycle ergometer sprint. Data were analyzed using a GLM and results are reported as mean ± SD or mean change ± 95 % CI. In both studies we observed several significant, yet stochastic changes in blood markers that were not indicative of potential harm or consistent for any treatment group. Equally, all treatment groups reported a similar number of minimal side effects. In Study 2, there was a significant increase in plasma nitrates for both CrN groups by d-7, subsequently abating by d-28. Muscle creatine increased significantly by d-7 in the CrM and CrN-High groups, but then decreased by d-28 for CrN-High. By d-28, there were significant increases in bench press lifting volume (kg) for all groups (PLA, 126.6, 95 % CI 26.3, 226.8; CrM, 194.1, 95 % CI 89.0, 299.2; CrN-Low, 118.3, 95 % CI 26.1, 210.5; CrN-High, 267.2, 95 % CI 175.0, 359.4, kg). Only the CrN-High group was significantly greater than PLA (p < 0.05). Similar findings were observed for bench press peak power (PLA, 59.0, 95 % CI 4.5, 113.4; CrM, 68.6, 95 % CI 11.4, 125.8; CrN-Low, 40.9, 95 % CI −9.2, 91.0; CrN-High, 60.9, 95 % CI 10.8, 111.1, W) and average power. Creatine nitrate delivered at 3 g was well-tolerated, demonstrated similar performance benefits to 3 g CrM, in addition, within the confines of this study, there were no safety concerns.
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The daily requirement of a 70-kg male for creatine is about 2 g; up to half of this may be obtained from a typical omnivorous diet, with the remainder being synthesized in the body Creatine is a carninutrient, which means that it is only available to adults via animal foodstuffs, principally skeletal muscle, or via supplements. Infants receive creatine in mother's milk or in milk-based formulas. Vegans and infants fed on soy-based formulas receive no dietary creatine. Plasma and muscle creatine levels are usually somewhat lower in vegetarians than in omnivores. Human intake of creatine was probably much higher in Paleolithic times than today; some groups with extreme diets, such as Greenland and Alaskan Inuit, ingest much more than is currently typical. Creatine is synthesized from three amino acids: arginine, glycine and methionine (as S-adenosylmethionine). Humans can synthesize sufficient creatine for normal function unless they have an inborn error in a creatine-synthetic enzyme or a problem with the supply of substrate amino acids. Carnivorous animals, such as lions and wolves, ingest much larger amounts of creatine than humans would. The gastrointestinal tract and the liver are exposed to dietary creatine in higher concentrations before it is assimilated by other tissues. In this regard, our observations that creatine supplementation can prevent hepatic steatosis (Deminice et al. J Nutr 141:1799-1804, 2011) in a rodent model may be a function of the route of dietary assimilation. Creatine supplementation has also been reported to improve the intestinal barrier function of the rodent suffering from inflammatory bowel disease.
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Systematic reviews and meta-analyses have become increasingly important in health care. Clinicians read them to keep up to date with their field [1],[2], and they are often used as a starting point for developing clinical practice guidelines. Granting agencies may require a systematic review to ensure there is justification for further research [3], and some health care journals are moving in this direction [4]. As with all research, the value of a systematic review depends on what was done, what was found, and the clarity of reporting. As with other publications, the reporting quality of systematic reviews varies, limiting readers' ability to assess the strengths and weaknesses of those reviews. Several early studies evaluated the quality of review reports. In 1987, Mulrow examined 50 review articles published in four leading medical journals in 1985 and 1986 and found that none met all eight explicit scientific criteria, such as a quality assessment of included studies [5]. In 1987, Sacks and colleagues [6] evaluated the adequacy of reporting of 83 meta-analyses on 23 characteristics in six domains. Reporting was generally poor; between one and 14 characteristics were adequately reported (mean = 7.7; standard deviation = 2.7). A 1996 update of this study found little improvement [7]. In 1996, to address the suboptimal reporting of meta-analyses, an international group developed a guidance called the QUOROM Statement (QUality Of Reporting Of Meta-analyses), which focused on the reporting of meta-analyses of randomized controlled trials [8]. In this article, we summarize a revision of these guidelines, renamed PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses), which have been updated to address several conceptual and practical advances in the science of systematic reviews (Box 1). Box 1: Conceptual Issues in the Evolution from QUOROM to PRISMA Completing a Systematic Review Is an Iterative Process The conduct of a systematic review depends heavily on the scope and quality of included studies: thus systematic reviewers may need to modify their original review protocol during its conduct. Any systematic review reporting guideline should recommend that such changes can be reported and explained without suggesting that they are inappropriate. The PRISMA Statement (Items 5, 11, 16, and 23) acknowledges this iterative process. Aside from Cochrane reviews, all of which should have a protocol, only about 10% of systematic reviewers report working from a protocol [22]. Without a protocol that is publicly accessible, it is difficult to judge between appropriate and inappropriate modifications.
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Purpose: The aim of the study was to determine whether creatine malate (CML) supplementation results in similar ergogenic effect in sprinters and long-distance runners. The other goal was to compare changes in body composition, physical performance and hormone levels after six-week training in athletes, divided into subgroups supplemented with creatine malate or taking placebo. Results: Six-week supplementation combined with physical training induced different effects in athletes. Significantly higher increases in relative and absolute peak power and total work (p < 0.05) were found in sprinters compared to other groups. Except for growth hormone, post-exercise venous blood serum hormone levels exhibited no statistically significant differences in athletes. After CML loading period, a significant increase in growth hormone was found in the group of sprinters. Conclusions: A significant ergogenic effect was found in sprinters, which was reflected by the increase in anaerobic exercise indices and morphological indices and elevated growth hormone level, after graded exercise testing. The significant increase in the distance covered during graded test was only observed in supplemented long-distance runners, whereas no significant changes in maximal oxygen uptake, relative peak power and relative total work were noticed. This could be caused by later anaerobic threshold appearance in exercise test to exhaustion.
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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.
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BACKGROUND: The purpose of the study was to determine the effect of 6-weeks training and creatine malate supplementation demonstrated in anaerobic capacity and aerobic power and in special judo fitness test performance (Throws in Total and Index in SJFT). METHODS: Ten professional competitors aged 21.2+/-3.3 years and practicing judo for 11+/-4.5 years participated in a typical pre-competition training program. Their height and weight during the first measurement were 1.75+/-0.06 m and 76.09+/-14.85 kg, respectively. Subjects participated in the same training sessions. The contestants have been training for approximately 20 hours a week: 5 days for 2 two-hour-training sessions. They used their usual diets. They were randomly selected to a treatment group who were administered the creatine malate (n=5) whereas the controls were receiving a placebo (n=5). All subjects were tested for anaerobic capacity (the Wingate-test) and aerobic power (the progressive test), and in the SJFT test, pre and post a six-week training during preparation period. We have used double-blind placebo-controlled design. RESULTS: Multifaceted judo training before competition caused a significant (z=2.40, P<0.05) increase in body mass (76.09+/-14.85 kg, Me=70.73 kg vs. 78.52+/-14.53 kg, Me=75.30 kg, P<0.05, n=10). The significant difference (z=2.30, P<0.05) was observed in FM and FMI, but not in percent fat in body mass (PF%). FM and FMI contributed in increased body mass and BMI, repectively (z=2.40, P<0.05). There was observed an increment in anaerobic capacity indices, with particular focus on shortening in time to obtain peak power toPP (3.99+/-0.71, Me=4.20 sec vs. 3.68 +/-0.77, Me=3.78 sec, P<0.05). Diet supplementation with creatine malate did not cause an increase in body mass index higher than in the control group (P>0.05). However, the groups differed in the post-test moment in the fatigue index (FI) (T=48.7+/-5, Me=46.1 vs. C=41.1+/-3, Me=40.4%, Z=1.98, P<0.05), whereas no significant differences were observed between pre- and post-experiment levels of aerobic power (p>0.05). Percent at VO2max at the anaerobic threshold (%VO2max), in the first measurement showed no significant differences between two groups, while in the second measurement statistically significant differences were observed: in T group %VO2max was higher (85.43+/-6.35, Me=85.5% vs. 76.13+/-3.48, Me=75.3%, Z=2.09, P<0.05). In general, a significant differences were observed in pretests and post-test measurement results in SJFT expressed in Throws in Total (pre=26.9+/-2.7, Me=27.5 vs. post=27.9+/-2.4, Me=28.5 throws (z=2.67, P<0.01), but no such changes was found for the index of SJFT. These changes in SJFT were not found to be caused by the supplementation with creatine malate, neither to be reflected in Throws in Total nor in the index of SJFT (post-test measurements comparison, P>0.05). CONCLUSIONS: The multifaceted judo training is conducive to the development of both FM and FMI. Use of supplementation of the diets with creatine malate does not cause an increase in body mass greater than in the control group. Shorter time to obtain peak power (toPP) is conducive to faster execution of rapid planned actions in attack or defense. Pre and post-training aerobic power did not change so it was not supplementation-dependent. Creatine malate did not affect the results in SJFT. There are many determinants of the judo fight results e.g. technical, tactical, physiological and psychological factors, one of them could be supplementation but it cannot be treated as a separate improving factor. The significant improvement in Total Throws in SJFT with the unchanged Index in SJFT suggests better neuromuscular adaptations compared to those occurring in circulatory and respiratory systems. The results obtained during the SJFT test depend not only on energy resources but also on the exercises which improve the technique of performing typical grip-and-throw judo actions, despite the ensuing fatigue. Key words: judo, training effect, creatine malate supplementation, anaerobic capacity, aerobic power, special fitness.
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Previous research has indicated that creatine retention is influenced by intramuscular creatine concentration and extracellular concentrations of glucose and insulin. This study examined whether different nutritional strategies affect whole body creatine retention. Specifically, 16 males with no history of creatine supplementation participated in this study. Subjects donated 24-hr urine samples for 4 days. After an initial control day, subjects were matched according to body mass and assigned to ingest in a single blind manner either 5 g of dextrose (D), 5 g of creatine monohydrate (CM), 5 g of CM + 18 g dextrose (C+D), or an effervescent creatine (EC) supplement (5 g of creatine + 18 g dextrose + 320 mg of sodium [as sodium carbonate and bicarbonate] + 175 mg of potassium [as potassium bicarbonate]) four times/day for 3 days. Creatine retention was estimated by subtracting total urinary creatine excretion from total supplemental creatine intake over the 3 day period. Data were analyzed by ANOVA. Results revealed that creatine retention was increased following creatine supplementation in all groups (D=0±0; CM= 36.6±9; C+D=48.0±7; EC=37.8±8 g, p=0.001). However, creatine retention in the C+D group was significantly greater than the CM group while no differences were observed between the EC and CM groups. This resulted in a greater percentage of creatine retention in the CD group (D= 0±0; CM=61±15; C+D=80±11; EC=63±13 %, p=0.001). These preliminary findings suggest that in accordance with previous research, ingesting dextrose (18 g) with CM (5 g) augments whole body creatine retention while EC supplementation appears to be no more effective than ingesting CM alone.
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Creatine has become one of the most popular dietary supplements in the sports nutrition market. The form of creatine that has been most extensively studied and commonly used in dietary supplements is creatine monohydrate (CM). Studies have consistently indicated that CM supplementation increases muscle creatine and phosphocreatine concentrations by approximately 15-40%, enhances anaerobic exercise capacity, and increases training volume leading to greater gains in strength, power, and muscle mass. A number of potential therapeutic benefits have also been suggested in various clinical populations. Studies have indicated that CM is not degraded during normal digestion and that nearly 99% of orally ingested CM is either taken up by muscle or excreted in urine. Further, no medically significant side effects have been reported in literature. Nevertheless, supplement manufacturers have continually introduced newer forms of creatine into the marketplace. These newer forms have been purported to have better physical and chemical properties, bioavailability, efficacy, and/or safety profiles than CM. However, there is little to no evidence that any of the newer forms of creatine are more effective and/or safer than CM whether ingested alone and/or in combination with other nutrients. In addition, whereas the safety, efficacy, and regulatory status of CM is clearly defined in almost all global markets; the safety, efficacy, and regulatory status of other forms of creatine present in today's marketplace as a dietary or food supplement is less clear.
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Creatine is a nutritional supplement widely used in sport, physical fitness training and bodybuilding. It is claimed to enhance performance. We describe a case in which serum creatinine is elevated due to the use of creatine ethyl esther. One week after withdrawal, the plasma creatinine had normalised. There are two types of creatine products available: creatine ethyl esther (CEE) and creatine monohydrate (CM). Plasma creatinine is not elevated in all creatine-using subjects. CEE , but not CM, is converted into creatinine in the gastrointestinal tract. As a result the use of CEE may be associated with elevated plasma creatinine levels. Since plasma creatinine is a widely used marker for renal function, the use of CEE may lead to a false assumption of renal failure.
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High-intensity interval training has been shown to be a time-efficient way to induce physiological adaptations similar to those of traditional endurance training. Creatine supplementation may enhance high-intensity interval training, leading to even greater physiological adaptations. The purpose of this study was to determine the effects of high-intensity interval training (HIIT) and creatine supplementation on cardiorespiratory fitness and endurance performance (maximal oxygen consumption (VO2PEAK), time-to-exhaustion (VO2PEAKTTE), ventilatory threshold (VT), and total work done (TWD)) in college-aged men. Forty-three recreationally active men completed a graded exercise test to determine VO2PEAK, VO2PEAKTTE, and VT. In addition, participants completed a time to exhaustion (TTE) ride at 110% of the maximum workload reached during the graded exercise test to determine TWD (TTE (sec) x W = J). Following testing, participants were randomly assigned to one of three groups: creatine (creatine citrate) (Cr; n = 16), placebo (PL; n = 17), or control (n = 10) groups. The Cr and PL groups completed four weeks of HIIT prior to post-testing. Significant improvements in VO2PEAK and VO2PEAKTTE occurred in both training groups. Only the Cr group significantly improved VT (16% vs. 10% improvement in PL). No changes occurred in TWD in any group. In conclusion, HIIT is an effective and time-efficient way to improve maximal endurance performance. The addition of Cr improved VT, but did not increase TWD. Therefore, 10 g of Cr per day for five days per week for four weeks does not seem to further augment maximal oxygen consumption, greater than HIIT alone; however, Cr supplementation may improve submaximal exercise performance.
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Numerous creatine formulations have been developed primarily to maximize creatine absorption. Creatine ethyl ester is alleged to increase creatine bio-availability. This study examined how a seven-week supplementation regimen combined with resistance training affected body composition, muscle mass, muscle strength and power, serum and muscle creatine levels, and serum creatinine levels in 30 non-resistance-trained males. In a double-blind manner, participants were randomly assigned to a maltodextrose placebo (PLA), creatine monohydrate (CRT), or creatine ethyl ester (CEE) group. The supplements were orally ingested at a dose of 0.30 g/kg fat-free body mass (approximately 20 g/day) for five days followed by ingestion at 0.075 g/kg fat free mass (approximately 5 g/day) for 42 days. Results showed significantly higher serum creatine concentrations in PLA (p = 0.007) and CRT (p = 0.005) compared to CEE. Serum creatinine was greater in CEE compared to the PLA (p = 0.001) and CRT (p = 0.001) and increased at days 6, 27, and 48. Total muscle creatine content was significantly higher in CRT (p = 0.026) and CEE (p = 0.041) compared to PLA, with no differences between CRT and CEE. Significant changes over time were observed for body composition, body water, muscle strength and power variables, but no significant differences were observed between groups. In conclusion, when compared to creatine monohydrate, creatine ethyl ester was not as effective at increasing serum and muscle creatine levels or in improving body composition, muscle mass, strength, and power. Therefore, the improvements in these variables can most likely be attributed to the training protocol itself, rather than the supplementation regimen.
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Fatigue during the 400-m sprint was studied by measuring muscle ATP, creatine phosphate (CP), lactate (M-La), and blood lactate (B-La) in six male runners before and after four experimental sprints (100, 200, 300, and 400 m). During the first 100 m, muscle CP decreased from 15.8 +/- 1.7 to 8.3 +/- 0.3 mmol/kg while M-La increased to 3.6 +/- 0.4 mmol/kg. After 200 m the CP had decreased to 6.5 +/- 0.5 mmol/kg and M-La had increased to 8.3 +/- 1.1 mmol/kg. At the end of the 400 meters, ATP and CP concentrations had decreased by 27% and 89%, respectively, and M-La had increased to 17.3 +/- 0.9 mmol/kg. It was concluded that after 200 m the speed of running decreased, although CP was not depleted and lactate concentration was not at maximum level. Complete fatigue occurred when CP stores were depleted and B-La and M-La attained an individual maximum.
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Measuring muscle mass is an important component of the nutritional assessment examination and a suggested index of this body space is the 24-h urinary excretion of creatinine. The method originated from studies in a variety of animal species in whom early workers found a parallelism between total body creatine and urinary excretion of creatinine. Assuming that nearly all creatine was within muscle tissue, that muscle creatine content remained constant and that creatinine was excreted at a uniform rate, an obvious "corollary" was that urinary creatinine was proportional to muscle mass. The so-called "creatinine equivalence" (kg muscle mass/g urinary creatinine) ranged experimentally from 17 to 22. One of the limiting factors in firmly establishing this constant and its associated variability was (and is) the lack of another totally acceptable noninvasive technique of measuring muscle mass to which the creatinine method could (or would) be compared. An improved understanding of creatine metabolism and a variety of clinical studies in recent years has tended to support the general validity of this approach. However, specific conditions have also been established in which the method becomes either inaccurate or invalid. While creatinine excretion may serve as a useful approximation of muscle mass in carefully selected subjects, there remains a need for accurate and practical indices of muscle mass for use in the individuals in whom the method cannot be reliably applied.
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Since the discovery of creatine in 1832, it has fascinated scientists with its central role in skeletal muscle metabolism. In humans, over 95% of the total creatine (Crtot) content is located in skeletal muscle, of which approximately a third is in its free (Crf) form. The remainder is present in a phosphorylated (Crphos) form. Crf and Crphos levels in skeletal muscle are subject to individual variations and are influenced by factors such as muscle fibre type, age and disease, but not apparently by training or gender. Daily turnover of creatine to creatinine for a 70kg male has been estimated to be around 2g. Part of this turnover can be replaced through exogenous sources of creatine in foods, especially meat and fish. The remainder is derived via endogenous synthesis from the precursors arginine, glycine and methionine. A century ago, studies with creatine feeding concluded that some of the ingested creatine was retained in the body. Subsequent studies have shown that both Crf and Crphos levels in skeletal muscle can be increased, and performance of high intensity intermittent exercise enhanced, following a period of creatine supplementation. However, neither endurance exercise performance nor maximal oxygen uptake appears to be enhanced. No adverse effects have been identified with short term creatine feeding. Creatine supplementation has been used in the treatment of diseases where creatine synthesis is inhibited.
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Nine male subjects performed two bouts of 30-s maximal isokinetic cycling before and after ingestion of 20 g creatine (Cr) monohydrate/day for 5 days. Cr ingestion produced a 23.1 +/- 4.7 mmol/kg dry matter increase in the muscle total creatine (TCr) concentration. Total work production during bouts 1 and 2 increased by approximately 4%, and the cumulative increases in both peak and total work production over the two exercise bouts were positively correlated with the increase in muscle TCr. Cumulative loss of ATP was 30.7 +/- 12.2% less after Cr ingestion, despite the increase in work production. Resting phosphocreatine (PCr) increased in type I and II fibers. Changes in PCr before exercise bouts 1 and 2 in type II fibers were positively correlated with changes in PCr degradation during exercise in this fiber type and changes in total work production. The results suggest that improvements in performance were mediated via improved ATP resynthesis as a consequence of increased PCr availability in type II fibers.
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This study examined the effects of 14 days of creatine supplementation on the physical working capacity at fatigue threshold (PWCFT), maximal isometric grip strength (GRIP), sit-to-stand (STS), and body weight (BW) in elderly men and women. Using a double blind cross-over design, fifteen men (n = 7) and women (n = 8) (age +/- SD = 74.5 +/- 6.4 yrs) were randomly assigned to either the creatine (CR) (20g.d-1 during week 1 decreasing to 10g.d-1 at week 2) or Placebo (PL) group. After a 4 to 6 week washout period, the subjects were assigned the other treatment. Before (pre) and after (post) the supplementation period, participants performed a discontinuous, cycle ergometry test to determine the PWCFT. In addition, subjects performed STS, GRIP, BW test prior to and post treatment. Southeastern part of the United States. Significant increases in GRIP (6.7%) and PWCFT (15.6%) from pre- to post-supplementation were found for the CR (p < 0.05) treatment, but no change for the PL treatment was observed. However, no significant change (p superior 0.05) was noted for STS or BW for either treatment. These findings suggest that 14 days of CR supplementation may increase upper body grip strength and increase physical working capacity by delaying neuromuscular fatigue in the elderly men and women in this study. While more research is needed, CR supplementation may improve upper body grip strength and lower body muscle endurance which may be important for maintaining health and independent living in elderly men and women.
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Previous research has shown that plasma creatine levels are influenced by extracellular concentrations of insulin and glucose as well as by the intracellular creatine concentration. However, the form of creatine administered does not appear to have any effect although specific data on this is lacking. This study examined whether the administration of three different forms of creatine had different effects on plasma creatine concentrations and pharmacokinetics. Six healthy subjects (three female and three male subjects) participated in the study. Each subject was assigned to ingest a single dose of isomolar amounts of creatine (4.4 g) in the form of creatine monohydrate (CrM), tri-creatine citrate (CrC), or creatine pyruvate (CrPyr) using a balanced cross-over design. Plasma concentration curves, determined over eight hours after ingestion, were subject to pharmacokinetic analysis and primary derived data were analyzed by repeated measures ANOVA. Mean peak concentrations and area under the curve (AUC) were significantly higher with CrPyr (17 and 14%, respectively) in comparison to CrM and CrC. Mean peak concentration and AUC were not significantly different between CrM and CrC. Despite the higher peak concentration with CrPyr there was no difference between the estimated velocity constants of absorption (ka) or elimination (kel) between the three treatments. There was no effect of treatment with CrPyr on the plasma pyruvate concentration. The findings suggest that different forms of creatine result in slightly altered kinetics of plasma creatine absorption following ingestion of isomolar (with respect to creatine) doses of CrM, CrC and CrPyr although differences in ka could not be detected due to the small number of blood samples taken during the absorption phase. Characteristically this resulted in higher plasma concentrations of creatine with CrPyr. Differences in bioavailability are thought to be unlikely since absorption of CrM is already close to 100%. The small differences in kinetics are unlikely to have any effect on muscle creatine elevation during periods of creatine loading.
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The purpose of this study was to examine the effects of 5 days of Creatine (Cr) loading on the electromyographic fatigue threshold (EMGFT) in college-aged women. Fifteen healthy college-aged women (mean +/- SD = 22.3 +/- 1.7 yrs) volunteered to participate in this double-blind, placebo-controlled study and were randomly placed into either placebo (PL - 10 g of flavored dextrose powder; n = 8) or creatine (Cr - 5 g di-creatine citrate plus 10 g of flavored dextrose powder; n = 7; Creatine Edge, FSI Nutrition) loading groups. Each group ingested one packet 4 times per day (total of 20 g/day) for 5 days. Prior to and following supplementation, each subject performed a discontinuous incremental cycle ergometer test to determine their EMGFT value, using bipolar surface electrodes placed on the longitudinal axis of the right vastus lateralis. Subjects completed a total of four, 60 second work bouts (ranging from 100-350 W). The EMG amplitude was averaged over 10 second intervals and plotted over the 60 second work bout. The resulting slopes from each successive work bouts were used to calculate EMGFT. A two-way ANOVA (group [Cr vs. PL] x time [pre vs. post]) resulted in a significant (p = 0.031) interaction. Furthermore, a dependent samples t-test showed a 14.5% +/- 3.5% increase in EMGFT from pre- to post-supplementation with Cr (p = 0.009), but no change for the PL treatment (-2.2 +/- 5.8%; p = 0.732). In addition, a significant increase (1.0 +/- 0.34 kg; p = 0.049) in weight (kg) was observed in the Cr group but no change for PL (-0.2 kg +/- 0.2 kg). These findings suggest that 5 days of Cr loading in women may be an effective strategy for delaying the onset of neuromuscular fatigue during cycle ergometry.
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A double-blind, placebo-controlled, randomized study was performed to evaluate the effect of oral creatine pyruvate (Cr-Pyr) and creatine citrate (Cr-Cit) supplementation on exercise performance in healthy young athletes. Performance during intermittent handgrip exercise of maximal intensity was evaluated before (pretest) and after (posttest) 28 days of Cr-Pyr (5 g/d, n = 16), Cr-Cit (5 g/d, n = 16) or placebo (pla, 5 g/d, n = 17) intake. Subjects performed ten 15-sec exercise intervals, each followed by 45 sec rest periods. Cr-Pyr (p < 0.001) and Cr-Cit (p < 0.01) significantly increased mean power over all intervals. Cr-Cit increased force during the first and second interval (p < 0.01) compared to placebo. The effect of Cr-Cit on force decreased over time and the improvement was not significant at the sixth and ninth interval, whereas Cr-Pyr significantly increased force during all intervals (p < 0.001). Cr-Pyr (p < 0.001) and Cr-Cit (p < 0.01) resulted in an increase in contraction velocity, whereas only Cr-Pyr intake significantly (p < 0.01) increased relaxation velocity. Oxygen consumption measured during rest periods significantly increased with Cr-Pyr (p < 0.05), whereas Cr-Cit and placebo intake did not result in significant improvements. It is concluded that four weeks of Cr-Pyr and Cr-Cit intake significantly improves performance during intermittent handgrip exercise of maximal intensity and that Cr-Pyr might benefit endurance, due to enhanced activity of the aerobic metabolism.
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The purpose of this study was to examine the effects of 5 d of creatine (Cr) loading on the electromyographic fatigue threshold (EMG FT) in college-age men. Sixteen men (age 22.4 +/- 2.6 yr, height 177.4 +/- 6.8 cm, weight 79.5 +/- 10.6 kg; M +/- SD) participated in this double-blind study and were randomly placed into either placebo (Pl; 10 g of flavored fructose powder per packet; n = 8) or Cr (5 g dicreatine citrate plus 10 g of flavored fructose powder per packet; n = 8) loading groups. Each participant ingested 1 packet 4 times/d, totaling 20 g/d for 5 days (loading). Before and after loading, each participant performed a discontinuous cycle-ergometer test to determine his EMG FT, using bipolar surface electrodes placed on the vastus lateralis of the right thigh. Four 60-s work bouts (ranging from 200 to 400 W) were completed. Adequate rest was given between bouts to allow for the participants' heart rate (HR) to drop within 10 beats of their resting HR. The EMG amplitude was averaged over 5-s intervals for each 60-s work bout. Resulting slopes from each successive work bout were used to calculate EMG FT. A 2-way ANOVA, Group (Cr vs. Pl) x Time (pre vs. post), resulted in a nonsignificant (p > .05) interaction for supplement and time. In addition, a significant increase (p = .009) in weight was observed in the Cr group. These data suggest that there was a minimal influence of Cr loading on EMG FT for the participants in this study.
Article
The use of creatine as an ergogenic aid for athletic performance is growing in popularity, despite limited scientific support for its efficacy. The purpose of this study was to determine the effect of creatine (Cr) monohydrate (CrM) and creatine phosphate (CrP) supplementation on strength, body composition, and blood pressure over a 6-week period. Thirty-five males (age range = 19-29 years) with at least 2 years of strength training experience were tested on three separate occasions (pretest, 3 weeks, 6 weeks). Strength tests performed were the one-repetition maximum (1-RM) bench press, 1-RM leg press, and maximal repetitions on the seated preacher bar curl with a fixed amount of weight. Subjects were divided into three groups matched for strength: placebo (Pl), CrM, and CrP. All subjects were provided a standardized strength training regimen and ingested a loading dosage of 20 g per day for the first 3 days of the study, followed by a maintenance dose of 10 g per day for the remainder of the 6-week supplementation period. Significant differences were noted between the Pl group and the two Cr groups for changes in lean body mass, body weight, and 1-RM bench press. These results suggest that oral Cr supplementation will result in greater strength and fat-free mass development. In addition, CrP may be as effective as CrM in achieving these desired outcomes. (C) 1999 National Strength and Conditioning Association
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This study evaluated the effects of creatine (Cr) loading and sex differences on aerobic running performance. 27 men (mean±SD; age: 22.2±3.1 years, ht: 179.5±8.7 cm, wt: 78.0±9.8 kg) and 28 women (age: 21.2±2.1 years, ht: 166.0±5.8 cm, wt: 63.4±8.9 kg) were randomly assigned to either creatine (Cr, di-creatine citrate; n=27) or a placebo (PL; n=28) group, ingesting 1 packet 4 times daily (total of 20 g/day) for 5 days. Aerobic power (maximal oxygen consumption: VO2max) was assessed before and after supplementation using open circuit spirometry (Parvo-Medics) during graded exercise tests on a treadmill. 4 high-speed runs to exhaustion were conducted at 110, 105, 100, and 90% of peak velocity to determine critical velocity (CV). Distances achieved were plotted over times-to-exhaustion and linear regression was used to determine the slopes (critical velocity, CV) assessing aerobic performance. The results indicated that Cr loading did not positively or negatively influence VO2max, CV, time to exhaustion or body mass (p>0.05). These results suggest Cr supplementation may be used in aerobic running activities without detriments to performance.
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Creatine (Cr) loading consists of short-term, high-dosage Cr supplementation and has been shown to increase intramuscular total Cr content. Increases in body weight (BW) have been shown to result from Cr loading, with differences by gender, and increased BW may impact weight-bearing exercise. The critical velocity (CV) test is used to quantify the relationship between total running distance and time to exhaustion. The CV test provides the variable, anaerobic running capacity (ARC), which is an estimate of the anaerobic energy reserves in muscle. The purpose of this study was to examine the effects of gender and Cr loading on ARC. Fifty moderately trained men and women volunteered to participate in this randomized, double-blinded, placebo (PL)-controlled, repeated-measures study. After a familiarization session, a 3-day testing procedure was conducted. A maximal oxygen consumption test VO(2)max) on a treadmill was performed on day 1 to establish the maximum velocity (Vmax) at VO(2)max and to record BW. Days 2 and 3 involved treadmill running at varying percentages of Vmax. Participants were randomly assigned to either the Cr or PL group and received 20 packets of the Cr supplement (1 packet = 5 g Cr citrate, 18 g dextrose) or 20 packets of the PL (1 packet = 18 g dextrose). After consuming 4 packets daily for 5 consecutive days, the 3-day testing procedure was repeated. The male Cr loading group exhibited a 23% higher (p = 0.003) ARC compared to the PL group. Nonsignificant BW increases were found for the Cr groups. These findings suggest that Cr loading may be an effective strategy for improving ARC in men, but not in women, and revealed only nonsignificant increases in BW. Creatine loading may be used before competition by athletes to provide improvements in high-intensity, short-duration activities.
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1. The present study was undertaken to test whether creatine given as a supplement to normal subjects was absorbed, and if continued resulted in an increase in the total creatine pool in muscle. An additional effect of exercise upon uptake into muscle was also investigated. 2. Low doses (1 g of creatine monohydrate or less in water) produced only a modest rise in the plasma creatine concentration, whereas 5 g resulted in a mean peak after 1 h of 795 (sd 104) μmol/l in three subjects weighing 76–87 kg. Repeated dosing with 5 g every 2 h sustained the plasma concentration at around 1000 μmol/l. A single 5 g dose corresponds to the creatine content of 1.1 kg of fresh, uncooked steak. 3. Supplementation with 5 g of creatine monohydrate, four or six times a day for 2 or more days resulted in a significant increase in the total creatine content of the quadriceps femoris muscle measured in 17 subjects. This was greatest in subjects with a low initial total creatine content and the effect was to raise the content in these subjects closer to the upper limit of the normal range. In some the increase was as much as 50%. 4. Uptake into muscle was greatest during the first 2 days of supplementation accounting for 32% of the dose administered in three subjects receiving 6 × 5 g of creatine monohydrate/day. In these subjects renal excretion was 40, 61 and 68% of the creatine dose over the first 3 days. Approximately 20% or more of the creatine taken up was measured as phosphocreatine. No changes were apparent in the muscle ATP content. 5. No side effects of creatine supplementation were noted. 6. One hour of hard exercise per day using one leg augmented the increase in the total creatine content of the exercised leg, but had no effect in the collateral. In these subjects the mean total creatine content increased from 118.1 (sd 3.0) mmol/kg dry muscle before supplementation to 148.5 (sd 5.2) in the control leg, and to 162.2 (sd 12.5) in the exercised leg. Supplementation and exercise resulted in a total creatine content in one subject of 182.8 mmol/kg dry muscle, of which 112.0 mmol/kg dry muscle was in the form of phosphocreatine.
Article
1. A method is described enabling the determination of fat, water, electrolytes, protein, DNA, RNA and total creatine in a single sample of human muscle obtained by the percutaneous needle-biopsy technique. The amino acid content can also be analysed in the same muscle sample. 2. Fifty healthy subjects were studied: 29 between 19 and 40 years of age, 11 between 41 and 60 years of age, and 10 between 61 and 85 years of age. The two groups aged less than 60 years showed only marginal differences in muscle composition, whereas the highest age group showed increases in muscle fat content in relation to tissue weight and decreases in alkali-soluble protein content in relation to both tissue weight and tissue DNA content. Also, potassium, magnesium, total creatine and RNA contents were decreased in this age group when related to tissue DNA content. When alkali-soluble protein was used as a reference base, only magnesium content was decreased. 3. A comparison was also made between female (n = 23) and male (n = 18) subjects in the age groups below 60 years. Differences observed included a higher fat content in female muscle, and an increase in total creatine content in relation to tissue weight. The alkali-soluble protein content was lower per muscle cell in the females when calculated on the basis of DNA content. 4. The results show that in the assessment of muscle constituents, age and sex must be taken into account.
Article
Muscle ATP, creatine phosphate and lactate, and blood pH and lactate were measured in 7 male sprinters before and after running 40, 60, 80 and 100 m at maximal speed. The sprinters were divided into two groups, group 1 being sprinters who achieved a higher maximal speed (10.07±0.13 m ·s−1) than group 2 (9.75±0.10 m ·s−1), and who also maintained the speed for a longer time. The breakdown of high-energy phosphate stores was significantly greater for group 1 than for group 2 for all distances other than 100 m; the breakdown of creatine phosphate for group 1 was almost the same for 40 m as for 100 m. Muscle and blood lactate began to accumulate during the 40 m exercise. The accumulation of blood lactate was linear (0.55±0.02 mmol · s−1 ·1−1) for all distances, and there were no differences between the groups. With 100 m sprints the end-levels of blood and muscle lactate were not high enough and the change in blood pH was not great enough for one to accept that lactate accumulation is responsible for the decrease in running speed over this distance. We concluded that 1) in short-term maximal exercise, performance depends on the capacity for using high-energy phosphates at the beginning of the exercise, and 2) the decrease in running speed begins when the high-energy phosphate stores are depleted and most of the energy must then be produced by glycolysis.
Article
Biopsy samples were obtained from vastus lateralis of eight female subjects before and after a maximal 30-s sprint on a nonmotorized treadmill and were analyzed for glycogen, phosphagens, and glycolytic intermediates. Peak power output averaged 534.4 +/- 85.0 W and was decreased by 50 +/- 10% at the end of the sprint. Glycogen, phosphocreatine, and ATP were decreased by 25, 64, and 37%, respectively. The glycolytic intermediates above phosphofructokinase increased approximately 13-fold, whereas fructose 1,6-diphosphate and triose phosphates only increased 4- and 2-fold. Muscle pyruvate and lactate were increased 19 and 29 times. After 3 min recovery, blood pH was decreased by 0.24 units and plasma epinephrine and norepinephrine increased from 0.3 +/- 0.2 nmol/l and 2.7 +/- 0.8 nmol/l at rest to 1.3 +/- 0.8 nmol/l and 11.7 +/- 6.6 nmol/l. A significant correlation was found between the changes in plasma catecholamines and estimated ATP production from glycolysis (norepinephrine, glycolysis r = 0.78, P less than 0.05; epinephrine, glycolysis r = 0.75, P less than 0.05) and between postexercise capillary lactate and muscle lactate concentrations (r = 0.82, P less than 0.05). The study demonstrated that a significant reduction in ATP occurs during maximal dynamic exercise in humans. The marked metabolic changes caused by the treadmill sprint and its close simulation of free running makes it a valuable test for examining the factors that limit performance and the etiology of fatigue during brief maximal exercise.
Article
Biopsy samples were obtained from the vastus lateralis muscle of eight subjects after 0, 20, 60, and 120 s of recovery from intense electrically evoked isometric contraction. Later (10 days), the same procedures were performed using the other leg, but subjects ingested 20 g creatine (Cr)/day for the preceding 5 days. Muscle ATP, phosphocreatine (PCr), free Cr, and lactate concentrations were measured, and total Cr was calculated as the sum of PCr and free Cr concentrations. In five of the eight subjects, Cr ingestion substantially increased muscle total Cr concentration (mean 29 +/- 3 mmol/kg dry matter, 25 +/- 3%; range 19-35 mmol/kg dry matter, 15-32%) and PCr resynthesis during recovery (mean 19 +/- 4 mmol/kg dry matter, 35 +/- 6%; range 11-28 mmol/kg dry matter, 23-53%). In the remaining three subjects, Cr ingestion had little effect on muscle total Cr concentration, producing increases of 8-9 mmol/kg dry matter (5-7%), and did not increase PCr resynthesis. The data suggest that a dietary-induced increase in muscle total Cr concentration can increase PCr resynthesis during the 2nd min of recovery from intense contraction.
Article
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.
Article
This study evaluated magnesium-creatine (MgCre) supplementation on body water and quadriceps torque. Maltodextran (Placebo), Mg oxide plus Cre (MgO-Cre), and Mg-creatine chelate (MgC-Cre) at 800 mg Mg and 5 g Cre per day were used for 2 weeks in 35 subjects in a random assignment, blinded study. Pre-post measures were completed with bioimpedance to determine total body water (TBW), extracellular water (ECF), and intracellular water (ICF), and an isokinetic device at 180 degrees per second for knee extension peak torque (T), total work (W), and power (PWR). Body weights increased for both treatment groups, MgO-Cre Delta 0.75 kg (P <.05) and MgC-Cre Delta 0.4 kg (P =.07). Significant pre-post differences (P <.05) were noted only for MgC-Cre in ICW (26.29 v 28.01 L) and ECW (15.75 v 14.88 L). MgC-Cre had significant peak T (Nm) increase (124.5 v135.8, P <.05), while MgO-Cre (116.4 v 124.9, P =.06) and placebo (119.8 v 123.7, P =.343) did not. Both treatment groups had increased PWR (P <.05). MgC-Cre affects cellular fluid compartments. The peak torque changes were significant only in the MgC-Cre group, which had increases in ICW that may infer more muscular creatine due to its osmotic effect, and with increased cellular hydration, perhaps increased protein synthesis.
Article
To compare the change in muscle creatine, fiber morphology, body composition, hydration status, and exercise performance between vegetarians and nonvegetarians with 8 wk of creatine supplementation and resistance training. Eighteen VG and 24 NV subjects (19-55 yr) were randomly assigned (double blind) to four groups: VG + creatine (VGCr, N=10), VG + placebo (VGPl, N=8), NV + creatine (NVCr, N=12), and NV + placebo (NVPl, N=12). Before and at the end of the study, muscle biopsies were taken from the vastus lateralis m, body composition was assessed by DXA, and strength was assessed using 1-RM bench press and leg press. Subjects participated in the same 8-wk resistance-training program. Creatine dosage was based on lean tissue mass (0.25 g.kg(-1) LTM.d(-1) x 7 d; 0.0625 g.kg(-1) LTM.d(-1) x 49 d). Biopsy samples indicated that total creatine (TCr=free Cr + PCr) was significantly lower in VG compared with NV at baseline (VG=117 mmol.kg(-1); NV=130 mmol.kg(-1); P<0.05). For Cr subjects, there was a greater increase in PCr, TCr, bench-press strength, isokinetic work, Type II fiber area, and whole-body lean tissue compared with subjects on placebo (P<0.05). Vegetarians who took Cr had a greater increase in TCr, PCr, lean tissue, and total work performance than nonvegetarians who took Cr (P<0.05). The change in muscle TCr was significantly correlated with initial muscle TCr, and the change in lean tissue mass and exercise performance. These findings confirm an ergogenic effect of Cr during resistance training and suggest that subjects with initially low levels of intramuscular Cr (vegetarians) are more responsive to supplementation.
Article
The purpose of this study was to determine the effects of 2 and 5 days of Cr loading on anaerobic working capacity (AWC) using the critical power (CP) test in women. Ten physically active women randomly received 2 treatments separated by a 5 week washout period: (A) 18 g dextrose as placebo (PL) or (B) 5.0 g Cr + 18 g dextrose taken 4 times per day for 5 days. Following a familiarization trial, each subject completed the CP test at baseline and following 2 and 5 days of supplementation. The PL resulted in no significant changes in AWC following supplementation; however, Cr increased AWC by 22.1% after 5 days of loading (p < 0.05). There was a significant main effect for body weight (BW), however, there was no significant increase in BW due to Cr supplementation. These results suggest that Cr supplementation is effective for increasing AWC in women following 5 days of loading without an associated increase in BW.
Article
We tested the hypotheses that, compared with a placebo group or creatine (Cr) group, a Mg(2+)-Cr chelate group would demonstrate improvements in the 1 repetition maximum (1RM) on the bench press and be able to perform more work at 70% of the 1RM for the bench press. Thirty-one weight-trained men were randomly assigned in a double-blind manner to a placebo group (multidextran), a Cr group (2.5 g of Cr daily), or a Mg(2+)-Cr group (2.5 g of Cr daily). Baseline data were collected for the bench press 1RM and maximal work completed during a fatigue set at 70% of the 1RM. Following 10 days of Cr supplementation, follow-up tests were completed for the dependent variables. Groups were similar when the change in 1RM was evaluated either absolutely or relatively. Both the Cr and the Mg(2+)-Cr groups had significantly larger increases in work, both absolutely and relatively, when compared with the placebo group. Partial support for the hypothesis suggests that low doses of Cr are effective at increasing fiber Cr content, and consequently, performance. Further, the Cr and Mg(2+)-Cr groups were similar in both performance tests, suggesting that the proposed mechanism of entry is no better than the conventional method when 2.5 g of Cr is administered and performance is measured as work. This study raises the possibility that a low dose of Cr may be an effective means of enhancing performance after short-term ingestion.
Article
The purpose of this study was to describe the physiological profile of responders (>20 mmol.kg(-1) dry weight [dw] increase in total intramuscular creatine monohydrate [Cr] + phosphorylated creatine [PCr]) versus nonresponders (<10 mmol.kg(-1) dw increase) to a 5-day Cr load (0.3 g.kg(-1).d(-1)) in 11 healthy men (mean age = 22.7 years). Pre-post 5-day cellular measures included total resting Cr content (Cr + PCr), fiber type composition, and fiber type cross-sectional area (CSA) determined from muscle biopsies of the vastus lateralis. Body mass, daily dietary intake, 24-hour urine outputs, urinary Cr and creatinine (CrN), and strength performance measures (1 repetition maximum [1RM] bench and leg press) were also assessed before and after the 5-day loading period. Results indicated that there were 3 levels of response to the 5-day supplementation: responders (R), quasi responders (QR), and nonresponders (NR) with mean changes in resting Cr + PCr of 29.5 mmol.kg(-1) dw (n = 3), 14.9 mmol.kg(-1) dw (n = 5), and 5.1 mmol.kg(-1) dw (n = 3), respectively. The results support a person-by-treatment interaction to acute Cr supplementation with R possessing a biological profile of lowest initial levels of Cr + PCr, greatest percentage of type II fibers, and greatest preload muscle fiber CSA and fat-free mass. Responders also showed improvement in 1RM leg press scores following the 5-day loading period. NR had higher preload levels of Cr + PCr, less type II muscle fibers, small preload muscle CSA, and lower fat-free mass and displayed no improvements in 1RM strength scores. The results suggest that to be considered a responder to acute oral supplementation, a favorable preexisting biological profile may determine the final extent to which an individual responds to supplementation. Physiologic profiles of nonresponders appear to be different and may limit their ability to uptake Cr. This may help partially explain the reported equivocal performance findings in the Cr supplementation literature.
Article
A double-blind study was performed to evaluate the effects of oral creatine-pyruvate administration on exercise performance in well-trained cyclists. Endurance and intermittent sprint performance were evaluated before (pretest) and after (posttest) one week of creatine-pyruvate intake (Cr(pyr), 2 x 3.5 g x d-1, n = 7) or placebo (PL, n = 7). Subjects first performed a 1-hour time trial during which the workload could be adjusted at 5-min intervals. Immediately they did five 10-sec sprints interspersed by 2-min rest intervals. Tests were performed on an individual race bicycle that was mounted on an ergometer. Steady-state power production on average was about 235-245 W, which corresponded to blood lactate concentrations of 4-5 mmol x l -1 and heart rate in the range of 160-170 beats x min -1. Power outputs as well as blood lactate levels and heart rates were similar between Cr(pyr) and PL at all times. Total work performed during the 1-h trial was 872 +/- 44 KJ in PL versus 891 +/- 51 KJ in CR pyr. During the intermittent sprint test power peaked at about 800-1000 watt within 2-3 sec, decreasing by 15-20 % towards the end of each sprint. Peak and mean power outputs were similar between groups at all times. Peak lactate concentrations after the final sprint were approximately 11 mmol x l -1 in both groups during both the pretest and the posttest. It is concluded that one week of creatine-pyruvate supplementation at a rate of 7 g x d -1 does not beneficially impact on either endurance capacity or intermittent sprint performance in cyclists.
Article
The purpose of this study was to determine the effects of 2 and 6 days of creatine phosphate loading on anaerobic working capacity (AWC) and body weight (BW) in men and women. Sixty-one men (n = 31) and women (n = 30) randomly received 1 of 3 treatments (4 x 5 g.d(-1) x 6 days) using a double blind design: (a) 18 g dextrose as placebo (PL); (b) 5.0 g Cr + 20 g dextrose (Cr); or (c) 5.0 g Cr + 18 g dextrose + 4 g of sodium and potassium phosphates (CrP). AWC was determined at baseline and following 2 and 6 days of supplementation using the Critical Power Test. BW increased significantly over time, and the mean value for the men was significantly greater compared to that for women, but there were no interactions (p > 0.05). There were gender-specific responses for AWC expressed in both absolute values (kJ) and relative to BW (kJ. kg(-1)), with the women demonstrating no significant interactions. For the men, CrP loading significantly increased AWC following 2 days (23.8%) and 6 days (49.8%) of supplementation vs. PL (kJ and kJ.kg(-1)). Cr supplementation increased AWC 13-15% in both genders compared to PL (1.1%- 3.0% decline); although this result was not statistically significant, it may have some practical significance.
Effects of exercise training and creatine malate supplementation on ventilatory threshold and anaerobic working capacity in long-distance runners
  • Ap T Tyka
  • W Pilch
  • A Cebula
Tyka AP T, Pilch W, Cebula A, et al. Effects of exercise training and creatine malate supplementation on ventilatory threshold and anaerobic working capacity in long-distance runners. J Kines Exer Sci 71: 23-30, 2015.
Effects of exercise training and creatine malate supplementation on ventilatory threshold and anaerobic working capacity in long-distance runners
  • Tyka AP
The metabolism of creatine and creatinine: Seventh paper. The fate of creatine when administered to man
  • Myers