CREATINE SUPPLEMENTATION
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Keywords:
Creatine
Creatine Monohydrate
Creatine kinase
Exercise physiology
Creatine, a natural nutrient found in animal foods, is alleged to be an effective nutritional ergogenic aid to enhance sport or exercise performance. It may be formed in kidney and liver from arginina and glicina. Creatine may be delivered to the muscle, where it may combine readily with phosphate to form creatine phosphate, a high-energy phosphagen in the ATP-CP system, and is stored. The ATP-CP energy system is important for rapid energy production, such as in speed and power events. Approximately 120 g of creatine is found in a 70 kg male, 95% in the skeletal muscle. Total creatine exists in muscle as both free creatine (40%) and phosphocreatine (60%). It is only recently that a concerted effort has been undertaken to investigate its potential ergogenic effect relative to sport or exercise performance. It does appear that oral creatine monohydrate may increase muscle total creatine, including both free and phosphocreatine. Many, but not all studies suggest that creatine supplementation may enhance performance in high intensity, short-term exercise task that are dependent primarily on the ATP-CP energy system, particularly on laboratory test involving repeated exercise bouts with limited recovery time between repetitions. Short-term creatine supplementation appears to increase body mass, although the initial increase is most likely water associated with the osmotic effect of increased intramuscular total creatine. Chronic creatine supplementation in conjunction with physical training involving resistance exercise may increase muscle mass. However, confirmatory research data are needed. Creatine supplementation up to 8 weeks, with high doses, has not been associated with major health risks; with low doses, it was demonstrated that in 5 years period supplementation, there are no adverse effects. The decision to use creatine as a mean to enhance sport performance is left to the description to the individual athlete.
Creatine
Creatine Monohydrate
Creatine kinase
Exercise physiology
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Creatine
Creatine Monohydrate
Exercise physiology
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The effect of oral creatine supplementation on high-intensity exercise performance has been extensively studied over the past ten years and its ergogenic potential in young healthy subjects is now well documented. Recently, research has shifted from performance evaluation towards elucidating the mechanisms underlying enhanced muscle functional capacity after creatine supplementation. In this review, we attempt to summarise recent advances in the understanding of potential mechanisms of action of creatine supplementation at the level of skeletal muscle cells. By increasing intracellular creatine content, oral creatine ingestion conceivably stimulates operation of the creatine kinase (CK)/phosphocreatine (PCr) system, which in turn facilitates muscle relaxation. Furthermore, evidence is accumulating to suggest that creatine supplementation can beneficially impact on muscle protein and glycogen synthesis. Thus, muscle hypertrophy and glycogen supercompensation a1'e candidate factors to explain the ergogenic potential of creatine ingestion. Additional issues discussed in this review are the fibre-type specificity of muscle creatine metabolism, the identification of responders versus non-responders to creatine intake, and the scientific background concerning potential side effects of creatine supplementation.
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Creatine
Creatine Monohydrate
Creatine kinase
Exercise physiology
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This paper summarizes and interprets the research published about physiological aspects of dietary supplementation with creatine monohydrate and the effects on physical performance. A nitrogenous molecule that occurs naturally in the flesh consumed by meat-eaters, creatine is also synthesized endogenously and is stored primarily in skeletal muscle. The research literature in which direct measurements of muscle creatine content have been reported indicates that most, but not all, subjects respond to "creatine loading" by increasing the total intramuscular concentration of creatine, including the concentration of phosphocreatine. The factors that affect muscle creatine stores are reviewed, as are the widely ranging results on physical performance. The mechanism of action by which increased intramuscular creatine could enhance performance is not yet clear. Original speculation was that increased phosphocreatine levels prior to commencing exercise, in conjunction with higher free creatine concentration, would prolong the time required until performance-limiting levels of phosphocreatine were reached during intense exercise. It was also speculated that restoration of phosphocreatine levels between bouts of such exercise would be more rapid. More recent studies question such speculation. This review includes a discussion of what is known about the health risks and side-effects associated with creatine loading. The paper concludes with speculation about the unprecedented attention given to creatine supplementation by recreational and competitive athletes and the media.
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Objective: To determine whether treatment with creatine can improve exercise intolerance in myophosphorylase deficiency (McArdle disease).Design: Double-blind, placebo-controlled crossover study with oral creatine monohydrate supplementation.Patients: Nine patients with biochemically and genetically proven McArdle disease were treated.Intervention: Five days of daily high-dose creatine intake (150 mg/kg body weight) were followed by daily lowdose creatine intake (60 mg/kg).Each treatment phase with creatine or placebo lasted 5 weeks. Main Outcome Measures:The effect of treatment was estimated at the end of each treatment phase by record-ing clinical scores, ergometer exercise test results, phosphorus 31 nuclear magnetic resonance spectroscopy, and surface electromyography.Results: Of 9 patients, 5 reported improvement of muscle complaints with creatine.Force-time integrals (P=.03) and depletion of phosphocreatine (P=.04) increased significantly during ischemic exercise with creatine.Phosphocreatine depletion also increased significantly during aerobic exercise (P =.006).The decrease of median frequency in surface electromyograms during contraction was significantly larger (P =.03) with creatine.Conclusion: This is the first controlled study indicating that creatine supplementation improves skeletal muscle function in McArdle disease.
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Creatine Monohydrate
Crossover study
Exercise physiology
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Creatine Monohydrate
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Creatine
Creatine Monohydrate
Creatine kinase
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Creatine
Creatine Monohydrate
Creatine kinase
Adenosine triphosphate
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