Creatine is a nutrient involved in energy production in the body. Creatine supplementation is based on the idea that additional creatine intake will make more creatine available in the body cells for energy procution, and therefore increase the ability of the body to do work.
Creatine supplementation has been shown to increase intramuscular Total-, Free-, and Phosphocreatine levels. Phosophocreatine is a major source of muscle energy for short-term, high-intensity exercise that lasts approximately 2-30 seconds. Creatine supplementation has not been consistently shown to increase performance in exercises requiring the use of the anaerobic glycolysis and aerobic glycolysis energy systems. More research in this area is needed and is currently being conducted. Some studies have found that creatine supplementation has increased performance in exercise that is short-term, and high intensity. This type of exercise utilizes the ATP-PC energy system and has a duration of ណ seconds.
Creatine supplementation has been shown to increase overall body mass. Probably due to water retention. When used chronically, with resistance exercise increases in lean body mass have been seen. More research is needed in this area also.
Use of creatine for up to 8-weeks has not been associated with major health risks. Because it is a legal supplement it is currently used by many athletes.
Long term supplementation and potential helath risks has not been determined. Research is currently being conducted in this area.
A very good review of exercise performance and creating use can be found in an article by Mel Williams, and J. David Branch.
Williams, M., and J.D. Branch. (1998). Creatine supplementation and exercise performance: an update. Journal of the American College of Nutrition, Vol. 17 No. 3, 216-234.