Creatine is a naturally occurring substance in the body that plays a role in energy production. It exists in both free and phosphorylated forms, with most of it found in skeletal muscle. Creatine can be synthesized in the body or obtained from dietary sources, primarily animal products. The concentration of creatine in muscle is around 120 mmol/kg, and it is continuously broken down into creatinine and excreted in urine.
Creatine supplementation has been shown to increase the levels of creatine and its phosphorylated form in muscle. Studies have demonstrated that short-term supplementation (5-7 days) of 20-25 g/day can attenuate the decrease in force or power production during short-duration, maximal bouts of exercise, particularly intermittent protocols. However, creatine supplementation has not been found to improve longer-duration, aerobic exercise.
The ergogenic effects of creatine supplementation are believed to be due to increased phosphocreatine resynthesis during recovery between exercise bouts, leading to higher phosphocreatine levels at the start of the next bout. This helps match ATP supply to ATP demand and improves performance during intense, intermittent protocols. The extent of creatine loading in muscle is crucial for experiencing these benefits.
Creatine supplementation has been associated with an increase in body mass of 1-3 kg, primarily due to increased total body water. Long-term effects of creatine supplementation and its interaction with resistance training are still being investigated, but preliminary data suggest potential enhancements in physiological adaptations.
No adverse side effects of creatine supplementation have been reported in healthy individuals. However, research on its effects during specific sports and competitions is limited, with most studies conducted in laboratory settings. Anecdotal information and concerns have often overshadowed controlled experimental data, contributing to the ongoing discussions and questions surrounding creatine supplementation.
In conclusion, creatine is a naturally occurring substance in the body that can be supplemented to enhance exercise performance, primarily in high-intensity, short-duration activities. Skeletal muscle is the main target tissue for creatine loading. The current understanding of creatine supplementation is based on laboratory research, and more studies are needed to address unanswered questions and provide further insights into its effects on human performance.