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An overview of the use of supplements in modern sports

Creatine Supplementation and Exercise: A Review of the Literature

This article has been cited by other articles in PMC. The following nine points related to the use of creatine as a nutritional supplement constitute the Position Statement of the Society. They have been approved by the Research Committee of the Society.

Creatine monohydrate is the most effective ergogenic nutritional supplement currently available to athletes in terms of increasing high-intensity exercise capacity and lean body mass during training. There is no scientific evidence that the short- or long-term use of creatine monohydrate has any detrimental effects on otherwise healthy individuals.

If proper precautions and supervision are provided, supplementation in young athletes is acceptable and may provide a nutritional alternative to potentially dangerous anabolic drugs. At present, creatine monohydrate is the most extensively studied and clinically effective form of creatine for use in nutritional supplements in terms of muscle uptake and ability to increase high-intensity exercise capacity.

The addition of carbohydrate or carbohydrate and protein to a creatine supplement appears to increase muscular retention of creatine, although the effect on performance measures may not be greater than using creatine monohydrate alone. Ingesting smaller amounts of creatine monohydrate e.

Creatine products are readily available as a dietary supplement and are regulated by the U. Specifically, in 1994, U. Creatine monohydrate has been reported to have a number of potentially beneficial uses in several clinical populations, and further research is warranted in these areas. The following literature review has been prepared by the authors in support of the aforementioned position statement.

Creatine Supplementation and Exercise: A Review of the Literature Introduction The use of creatine as a sport supplement has been surrounded by both controversy and fallacy since it gained widespread popularity in the early 1990's. Anecdotal and media reports have often claimed that creatine usage is a dangerous and unnecessary practice; often linking creatine use to anabolic steroid abuse [ 1 ]. Many athletes and experts in the field have reported that creatine supplementation is not only beneficial for athletic performance and various medical conditions but is also clinically safe [ 2 - 5 ].

Although creatine has recently been accepted as a safe and useful ergogenic aid, several myths have been purported about creatine supplementation which include: All weight gained during supplementation is due to water retention. Creatine supplementation causes renal distress. Long-term effects of creatine supplementation are completely unknown.

Newer creatine formulations are more beneficial than creatine monohydrate CM and cause fewer side effects. While these myths have been refuted through scientific investigation, the general public is still primarily exposed to the mass media which may or may not have accurate information. Due to this confounding information, combined with the fact that creatine has become one of the most popular nutritional supplements on the market, it is important to examine the primary literature on supplemental creatine ingestion in humans.

The purpose of this review is to determine the present state of knowledge concerning creatine supplementation, so that reasonable guidelines may be established and unfounded fears diminished in regard to its an overview of the use of supplements in modern sports.

Background Creatine has become one of the most extensively studied and scientifically validated nutritional ergogenic aids for athletes. Additionally, creatine has been evaluated as a potential therapeutic agent in a variety of medical conditions such as Alzheimer's and Parkinson's diseases.

Biochemically speaking, the energy supplied to rephosphorylate adenosine diphosphate ADP to adenosine triphosphate ATP during and following intense exercise is largely dependent on the amount of phosphocreatine PCr stored in the muscle [ 67 ]. As PCr stores become depleted during intense exercise, energy availability diminishes due to the inability to resynthesize ATP at the rate required to sustained high-intensity exercise [ 67 ].

Consequently, the ability to maintain maximal-effort exercise declines.

  1. Three days later, a French sports newspaper, L'Equipe, reported that supplemental creatine is dangerous for the kidneys in any condition [ 70 ]. Long-term creatine intake is beneficial to muscle performance during resistance training.
  2. Reliable studies are yet to be published for creatine ethyl ester and creatine with cinnulin extract.
  3. Creatine supplementation improves sprint performance in male sprinters. Combined creatine and sodium bicarbonate supplementation enhances interval swimming.
  4. Long-term creatine supplementation does not significantly affect clinical markers of health in athletes.

The availability of PCr in the muscle may significantly influence the amount of energy generated during brief periods of high-intensity exercise. Furthermore, it has been hypothesized that increasing muscle creatine content, via creatine supplementation, may increase the availability of PCr allowing for an accelerated rate of resynthesis of ATP during and following high-intensity, short-duration exercise [ 6 - 12 ].

Theoretically, creatine supplementation during training may lead to greater training adaptations due to an enhanced quality and volume of work performed. In terms of potential medical applications, creatine is intimately involved in a number of metabolic pathways. For this reason, medical researchers have been investigating the potential therapeutic role of creatine supplementation in a variety of patient populations. Creatine is chemically known as a non-protein nitrogen; a compound which contains nitrogen but is not a protein per se [ 13 ].

It is synthesized in the liver and pancreas from the amino acids arginine, glycine, and methionine [ 91314 ]. Additionally, small amounts of creatine are also found in the brain and testes [ 815 ]. About two thirds of the creatine found in skeletal muscle is stored as phosphocreatine PCr while the remaining amount of creatine is stored as free creatine [ 8 ]. However, the average human has the capacity to store up to 160 grams of creatine under certain conditions [ 79 ].

The creatinine is then excreted in urine [ 1316 ]. Creatine stores can be replenished by obtaining creatine in the diet or through endogenous synthesis of creatine from glycine, arginine, and methionine [ 1718 ]. Dietary sources of creatine include meats and fish.

Large amounts of fish and meat must be consumed in order to obtain gram quantities of creatine. Supplementation Protocols and Effects on Muscle Creatine Stores Various supplementation protocols have been suggested to be efficacious in increasing muscle stores of creatine. The amount of increase in muscle storage depends on the levels of creatine in the muscle prior to supplementation.

The magnitude of the increase in skeletal muscle creatine content is important because studies have reported performance changes to be correlated to this increase [ 2021 ]. The supplementation protocol most often described in the literature is referred to as the "loading" protocol.

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This protocol is characterized by ingesting approximately 0. Furthermore, supplementing with 0. Other suggested supplementation protocols utilized include those with no loading phase as well as "cycling" strategies.

These protocols seems to be equally effective in increasing muscular stores of creatine, but the increase is more gradual and thus the ergogenic effect does not occur as quickly. Cycling protocols involve the consumption of "loading" doses for 3—5 days every 3 to 4 weeks [ 1822 ]. These cycling protocols appear to be effective in increasing and maintaining muscle creatine content before a drop to baseline values, which occurs at about 4—6 weeks [ 2829 ].

Creatine Formulations and Combinations Many forms of creatine exist in the marketplace, and these choices can be very confusing for the consumer. Most of these forms of creatine have been reported to be no better than traditional CM in terms of increasing strength or performance [ 30 - 38 ].

Reliable studies are yet to be published for creatine ethyl ester and creatine with cinnulin extract. These investigations indicate that the combination may have greater effects on strength, lean mass, and body fat percentage; in addition to delaying neuromuscular fatigue [ 3132 ].

Three alternative creatine formulations have shown promise, but at present do not have sufficient evidence to warrant recommendation in lieu of CM. For example, creatine phosphate has been reported to be as effective as CM at improving LBM and strength, [ 36 ] yet this has only been reported in one study.

In addition, creatine phosphate is currently more difficult and expensive to produce than CM. Combining CM with sodium phosphate, which has been reported to enhance high-intensity endurance exercise, may be a more affordable alternative to creatine phosphate. In addition, this combination failed to improve thermal and cardiovascular responses to a greater extent than CM alone [ 42 ]. The addition of certain macronutrients appears to significantly augment muscle retention of creatine.

Likewise, Steenge et al.

  • Effects of oral creatine and resistance training on myogenic regulatory factor expression;
  • Long-term effects of creatine supplementation are completely unknown;
  • Interestingly, Kreider et al.

Additional investigations by Greenwood and colleagues [ 3043 ] have reported increased creatine retention from the addition of dextrose or low levels of D-pinitol a plant extract with insulin-like properties. While the addition of these nutrients has proved to increase muscle retention, several recent investigations have reported these combinations to be no more effective at improving muscle strength and endurance or athletic performance [ 44 - 46 ].

Other recent studies, however, have indicated a potential benefit on anaerobic power, muscle hypertrophy, and 1 RM muscle strength when combining protein with creatine [ 4748 ]. It appears that combining CM with carbohydrate or carbohydrate and protein produces optimal results.

Studies suggest that increasing skeletal muscle creatine uptake may enhance the benefits of training. Effects of Supplementation on Exercise Performance and Training Adaptations CM appears to be the most effective nutritional supplement currently available in terms of improving an overview of the use of supplements in modern sports body mass and anaerobic capacity.

To date, several hundred peer-reviewed research studies have been conducted to evaluate the efficacy of CM supplementation in improving exercise performance. No studies have reported an ergolytic effect on performance although some have suggested that weight gain associated with CM supplementation could be detrimental in sports such as running or swimming. Nearly all studies indicate that "proper" CM supplementation increases body mass by about 1 to 2 kg in the first week of loading [ 19 ].

The vast expanse of literature confirming the effectiveness of CM supplementation is far beyond the scope of this review. Briefly, short-term adaptations reported from CM supplementation include increased cycling power, total work performed on the bench press and jump squat, as well as improved sport performance in sprinting, swimming, and soccer [ 3850 - 57 ].

Long-term adaptations when combining CM supplementation with training include increased muscle creatine and PCr content, lean body mass, strength, sprint performance, power, rate of force development, and muscle diameter [ 3954 - 60 ]. The gains in muscle mass appear to be a result of an improved ability to perform high-intensity exercise via increased PCr availability and enhanced ATP synthesis, thereby enabling an athlete to train harder and promote greater muscular hypertrophy via increased myosin heavy chain expression possibly due to an increase in myogenic regulatory factors myogenin and MRF-4 [ 262765 ].

The tremendous numbers of investigations conducted with positive results from CM supplementation lead us to conclude that it is the most effective nutritional supplement available today for increasing high-intensity exercise capacity and building lean mass. Medical Safety of Creatine Supplementation While the only clinically significant side effect reported in the research literature is that of weight gain [ 41822 ], many anecdotal claims of side effects including dehydration, cramping, kidney and liver an overview of the use of supplements in modern sports, musculoskeletal injury, gastrointestinal distress, and anterior leg compartment syndrome still exist in the media and popular literature.

While athletes who are taking CM may experience these symptoms, the scientific literature suggests that these athletes have no greater, and a possibly lower, risk of these symptoms than those not supplementing with CM [ 246667 ].

Poortmans and Francaux reported that the claims of deleterious effects of creatine supplements on renal function began in 1998 [ 68 ]. These claims followed a report that creatine supplementation was detrimental to renal glomerular filtration rate GFR in a 25-year-old man who had previously presented with kidney disease glomerulosclerosis and corticosteroid-responsive nephritic syndrome [ 69 ].

Three days later, a French sports newspaper, L'Equipe, reported that supplemental creatine is dangerous for the kidneys in any condition [ 70 ]. Several European newspapers then picked up the "news" and reported the same. Since that time, other individual case studies have been published posing that CM supplementation caused deleterious effects on renal function [ 7172 ].

In fact, Poortmans et al. Interestingly, Kreider et al. The authors noted that if serum creatinine was examined as the sole measure of renal function, it would appear that nearly all of the athletes regardless of CM usage were experiencing renal distress. Although case studies have reported problems, these large-scale, controlled studies have shown no evidence indicating that CM supplementation in healthy individuals is a detriment to kidney functioning.

Another anecdotal complaint about supplemental creatine is that the long-term effects are not known. Widespread use of CM began in the 1990's. Over the last few years a number of researchers have begun to release results of long-term safety trials.

International Society of Sports Nutrition position stand: creatine supplementation and exercise

So far, no long-term side effects have been observed in athletes up to 5 yearsinfants with creatine synthesis deficiency up to 3 yearsor in clinical patient populations up to 5 years [ 45187576 ].

One cohort of patients taking 1. In addition, research has demonstrated a number of potentially helpful clinical uses of CM in heart patients, infants and patients with creatine synthesis deficiency, patients suffering orthopedic injury, and patients with various neuromuscular diseases. Potential medical uses of supplemental creatine have been investigated since the mid 1970s.

Although more research is needed to determine the extent of the clinical utility, some promising results have been reported in a number of studies suggesting that creatine supplements may have therapeutic benefit in certain patient populations.

In conjunction with short- and long-term studies in healthy populations, this evidence suggests that creatine supplementation appears to be safe when taken within recommended usage guidelines.