Effects of creatine supplementation on exercise performance

While creatine has been known to man since 1835, when a French scientist re ported finding this constituent of meat, its presence in athletics as a per formance enhancer is relatively new. Amid claims of increased power and str ength, decreased performance time and increased muscle mass, creatine is be ing hailed as a true ergogenic aid. Creatinine is synthesised from the amin o acids glycine, arginine and methionine in the kidneys, liver and pancreas , and is predominantly found in skeletal muscle, where it exists in 2 forms . Approximately 40% is in the free creatine form (Cr-free), while the remai ning 60% is in the phosphorylated form, creatine phosphate (CP). The daily turnover rate of approximately 2g per day is equally met via exogenous inta ke and endogenous synthesis. Although creatine concentration (Cr) is greate r in fast twitch muscle fibres, slow twitch fibres have a greater resynthes is capability due to their increased aerobic capacity. There appears to be no significant difference between males and females in Cr, and training doe s not appear to effect Cr. The 4 roles in which creatine is involved during performance are temporal energy buffering, spatial energy buffering, proto n buffering and glycolysis regulation. Creatine supplementation of 20g per day for at least 3 days has resulted in significant increases in total Cr f or some individuals hut not others, suggesting that there are 'responders' and 'nonresponders'. These increases in total concentration among responder s is greatest in individuals who have the lowest initial total Cr, such as vegetarians, increased concentrations of both Cr-free and CP an believed to aid performance by providing more short term energy. as well as increase t he rate of resynthesis during rest intervals. Creatine supplementation does not appear to aid endurance and incremental type exercises, and may even b e detrimental. Studies investigating the effects of creatine supplementatio n on short term, high intensity exercises have reported equivocal results, with approximately equal numbers reporting significant and nonsignificant r esults. The only side effect associated with creatine supplementation appea rs to be a small increase in body mass, which is due to either water retent ion or increased protein synthesis.