What Is Creatine?
Creatine is a nitrogenous amine found in animal products. Omnivores ingest about 1 gram daily but creatine can also be formed in the liver, kidney, and pancreas from glycine, arginine, and methionine.
Creatine comprises 0.3% to 0.5% of muscle weight. Most creatine in muscle is in the form of phosphocreatine and about 40% is in the form of free creatine.
Meat, fish and other animal products.
Main Functions Of Creatine
1. Creatine is an important source of energy for muscle contraction because it can undergo both rapid and reversible phosphorylation. Phosphorylation of creatine, catalyzed by creatine kinase, forms phosphocreatine. During dephosphorylation, a phosphate group is donated to adenosine triphosphate forming
2. This phosphorylation-dephosphorylation reaction provides phosphate for performing high-intensity, short-duration physical activity. Three days of creatine ingestion increased total body water and intracellular fluid volumes without affecting extracellular fluid volumes.
Clinical Trials On Creatine
Creatine research is characterized by many small laboratory studies and very few field studies. Evidence is mixed on the effect of creatine in short-term, high-intensity exercise, and negative trials predominate for other ergogenic effects. A review of creatine supplementation in exercise identified 31 trials of creatine monohydrate supplements on short-term (<30 seconds) high-intensity performance, thought to be dependent on endogenous levels of ATP and phosphocreatine. Twenty-two of these trials were randomized, double-blind and placebo-controlled, but all were very small. Most trials used doses of 20 to 25 g/day. Most of these trials indicated a positive ergogenic effect; however, only 9 of 22 randomized double-blind placebo-controlled trials showed a benefit.
Fourteen trials of creatine monophosphate in high-intensity, more prolonged, predominantly anaerobic exercise tests were identified. Nine were randomized, double-blind, placebo controlled trials. The largest trial enrolled only 32 participants, and only three trials enrolled more than 20 people. Most used doses of creatine >20 g/day. Five of fourteen trials showed a positive ergogenic effect; only two of nine randomized double-blind placebo controlled trials showed a benefit. Six of these studies (four in swimmers and two in runners) were field studies. None of the studies that examined creatine supplementation in swim performance found any benefit. In 12 female runners, creatine supplementation (20 g/day x 5 days) did not improve 700-m run time. A single-blind study of creatine supplementation in 10 trained middle distance runners reported a significant benefit.
Studies in aerobic exercise performance tests (>150 seconds) are even less impressive. Only two of eight studies of creatine monohydrate supplementation in aerotic exercise performance tests found a benefit of creatine. Of the five randomized, double-blind, placebo-controlled trials, only one found a benefit. Only one of five of the field trials found a benefit. One of the field reports found that creatine impaired performance in a forest terrain run.
Effects Of Creatine On Body Mass
Of 19 publications that recorded effects on body mass, increased body mass was noted in 13/21 groups. Short-term supplementation may increase both total body mass and lean body mass; however, most of the increased body mass may be due to water retention.
1. Caffeine appears to eliminate any ergogenic effect of creatine.
2. Concurrent use with potentially nephrotoxic drugs should be avoided.
Skeletal muscle creatine: normal intracellular concentration 90 to 150 mmol/kg
Common Dosage Forms Of Creatine
20 to 25 g (0.3 g/kg/day) x 5 days, then maintenance dose of 2 to 5 g/day is the most commonly tested regiment in clinical trials. However, 3 g/day x 28 days achieves similar intracellular creatine levels, and maintenance doses above 2 g/day appear to have no additional benefit
Q: Is it legal to use creatine supplementation in athletic competition?
A: Yes, it is an allowable substance.