Creatine is a nitrogenous amide acid that is synthesised in the body from the amino acids arginine, glycine, and methionine (primarily in the kidneys and the pancreas), and it is also obtained from the diet (primarily from the red meat and the fish — approximately 1-2g of creatine is obtained daily from a typical omnivorous diet). The total body creatine pool is approximately 120g (with 95% in the skeletal muscle, 3% in the brain, and 2% in other tissues), and it exists in two forms — the free creatine (Cr) and the phosphocreatine (PCr). The phosphocreatine is the high-energy reserve that is used to regenerate the ATP from the ADP in the first few seconds of the high-intensity muscle contraction, before the oxidative phosphorylation and the glycolysis can ramp up to meet the energy demand. The phosphocreatine system is the fastest available energy source for the muscle contraction — it can regenerate the ATP at a rate that is approximately 100 times faster than the oxidative phosphorylation, and it is therefore the primary energy source for the high-intensity exercise that lasts for up to 10 seconds (such as the sprint, the weight lifting, and the jumping). Without adequate creatine and phosphocreatine, the high-intensity exercise capacity is severely impaired, and the muscle strength, the power, and the anaerobic exercise performance are reduced — this is the basis for the widespread use of creatine supplementation as an ergogenic aid in athletes and in people who engage in the high-intensity exercise.
The Phosphocreatine and the ATP Regeneration
The phosphocreatine (PCr) is the storage form of the creatine in the muscle — it is synthesised from the creatine and the ATP by the creatine kinase enzyme (which uses the energy of the ATP to attach the phosphate to the creatine). When the ATP is needed (for the muscle contraction, for the nerve impulse conduction, or for any other energy-requiring process in the cell), the ATP is used to donate its phosphate to the ADP, forming the ATP — this is the immediate energy source for all cellular processes. However, the cellular ATP store is limited (it can sustain the maximal muscle contraction for only 1-2 seconds), and it must be rapidly regenerated from the ADP to maintain the muscle contraction. The phosphocreatine provides this rapid regeneration — the creatine kinase enzyme transfers the phosphate from the PCr to the ADP, forming the ATP and the free creatine. This reaction is very fast (it can be completed in milliseconds) and it can regenerate the ATP at a rate that is sufficient to sustain the maximal muscle contraction for up to 10 seconds, bridging the gap between the initial energy demand and the slower oxidative phosphorylation and glycolysis.
The clinical importance of the creatine for the high-intensity exercise performance is underscored by the observation that the creatine supplementation (at 20g daily for 5-7 days, followed by a maintenance dose of 3-5g daily) increases the muscle creatine and phosphocreatine content by 15-40%, increases the exercise performance during the repeated bouts of the high-intensity exercise by 10-20%, and increases the strength and the power of the skeletal muscle by 5-10% in the majority of the athletes who supplement with creatine. These effects are among the most consistent and the most impressive of any ergogenic aid, and they make the creatine supplementation one of the most widely used and most effective nutritional strategies for the enhancement of the exercise performance.
Creatine and the Cognitive Function
Creatine is also present in the brain, where it serves as an energy buffer for the brain cells — the brain has a very high metabolic rate and is particularly dependent on the rapid energy supply for the maintenance of the ion gradients (the Na+/K+ ATPase consumes approximately 20% of the brain ATP) and for the neurotransmitter release. The phosphocreatine system in the brain provides the same rapid energy buffer that it provides in the muscle, and it is thought to be important for the cognitive function, particularly during the periods of the high cognitive demand or of the metabolic stress. The creatine supplementation has been studied for its effects on the cognitive function in healthy individuals, in the elderly, and in people with the neurological disorders — with mixed results, suggesting that the benefit of creatine is most pronounced in people who are under metabolic stress or who have a low baseline creatine status.
Practical Application
For general creatine supplementation, the evidence-based approach is to supplement with 3-5g of creatine monohydrate daily (which is the most studied and the most cost-effective form of creatine). The loading protocol (20g daily for 5-7 days) is not necessary to achieve the same long-term benefits and produces more gastrointestinal symptoms (nausea, cramping, diarrhoea) than the maintenance protocol. The creatine monohydrate is generally well-tolerated with no significant adverse effects at doses up to 10g daily, and the excess creatine is excreted in the urine (which gives the urine the characteristic bright yellow colour at high doses). For comprehensive energy and exercise support, creatine pairs well with the beta-alanine (which is the precursor of the carnosine and which buffers the acid that is produced during the high-intensity exercise), with the caffeine (which stimulates the CNS and enhances the exercise performance, though the combination may reduce the force production in some individuals), and with the carbohydrate (which enhances the muscle creatine uptake by stimulating the insulin release).
A quality supplement routine can make a real difference to your results.
Leave a Reply