Creatine

Phosphocreatine (creatine) is a substance that accumulates in muscles; it supplies phosphate to ATP and, thus, quickly restores ATP during anaerobic muscle contraction. It is synthesized inside the liver from arginine, glycine and methionine; dietary sources are milk, beefsteak and some types of fish.

[1], [2], [3], [4]

Pharmacodynamics

• Increases energy for physical exertion of high power.
• Increases muscle mass.

Theoretical basis

Creatine (Cr), or methylguanidine acetic acid, is an amine consisting of three amino acids (glycine, arginine and methionine). KrF and adenosine triphosphate (ATP) deliver most of the energy for a brief maximum physical load.

The average amount of creatine in skeletal muscle is 125 mmol-kg-1 of dry muscle mass and ranges from 90-160 mmol-kg-1 of dry muscle mass. Approximately 60% of muscle creatine is in the form of KrF. The share of creatine in KrF can be obtained from food creatine (mainly from meat products) or synthesized from the amino acids glycine and arginine. Muscle creatine is replenished at a rate of 2 g per day after its irreversible conversion to creatinine. The presence of CRF is of great importance during a short-term physical exertion of high power, because depletion of KrF inhibits the resynthesis of ATP at the desired rate. Theoretically, the action of KrF as an ergogenic agent consists in the ability of KpF to rephosphorylate adenosine diphosphate (ADP) for the resynthesis of ATP during anaerobic metabolism. Creatine supplements are used to increase the speed and power extracted from the ATF-KrF energy system.

[5], [6], [7], [8], [9], [10], [11], [12], [13], [14],

Research results

Greenhaff noted that the consumption of 20-25 grams of creatine monohydrate per day (four to five doses of 5 grams) for 5-7 days can give a 20% increase in the level of creatine in the muscles, of which about 20% is KrF. After this loading dose, a dose of 2-5 g per day should support an elevated level of creatine.

Numerous studies have been carried out to consider the effect of adding Kr on sports performance. Volek et al. Investigated the effect of Kr additives on muscle performance during repeated high-intensity exercises with the overcoming of resistance. Groups that received creatine and placebo performed bench presses from the machine and jumps in length, bending their legs. The events were conducted three times (T1, T2 and T3) with an interval of 6 days. Prior to the T1 test, no additives were obtained. In the interval between T1 and T2, both groups took a placebo. In the interval between T2 and T3, one group received 25 grams of creatine (5 doses of 5 grams) per day, and the other continued to receive a placebo. Creatine supplements significantly increased peak power during all five series of jumps and significantly improved the number of repetitions during the five series of bench presses from the machine. Researchers came to the conclusion that athletes performing physical exertion with overcoming resistance can benefit from taking creatine supplements, because they allow to make the training more intense.

Additional studies have confirmed the ergogenic effect of Cr for various exercises requiring high power. Creatine supplements were associated with an increase in strength in exercises with resistance in women in the sitting position and in soccer players, an increase in the maximum power in the sprint on the treadmill, an improvement in the performance of single and repeated short-term jerks, an increase in bicycle race time to exhaustion.

Engelhardt et al. Examined the effect of creatine supplementation on athletes specializing in triathlon. After taking 20 grams of creatine or a placebo for 5 days, the athletes were tested for endurance (30-minute cycle) at intervals of 15 s for cycling and 45 s for rest. The results showed that the additives significantly (by 18%) increased the power, but did not affect the endurance performance.

However, not all studies have revealed positive results. In some experiments, creatine supplements did not show even a minimal ergogenic effect on the strength and performance of jerks. Creatine was also ineffective in endurance exercise.

Creatine supplements, apparently, also increase lean mass. Is the increase in lean mass the result of enhanced protein synthesis or fluid retention? Most researchers indicate an increase in body weight from 0.7 to 1.6 kg after a short-term intake of supplements. Kreidor et al. Studied the total body weight in comparison with the total amount of water in the body from the players during the 28-day intake of the supplement and the control group of athletes. The group with creatinine increased the total body weight by an average of 2.42 kg and did not have a significant increase in the volume of water. Further studies are needed to determine the effect of creatine supplementation on protein synthesis and fluid retention.

The claimed effect of phosphocreatine (creatine) 

It is believed that creatine improves physical and athletic form and reduces fatigue. Some studies suggest that creatine is effective with increasing load, performed at a short maximum effort (for example, sprinting, weightlifting). Its therapeutic use in muscle deficiency of phosphorylase (type 2 glycogenosis) and atrophy of the choroid and retina has been proved; preliminary data also indicate possible side effects in Parkinson's disease and amyotrophic lateral sclerosis.

Dosing and administration

Many reports indicate that creatine supplements led to increased muscle cramps, stretching of muscles and tendons, muscle damage and delayed recovery after trauma. However, in studies evaluating trained athletes during strenuous workouts, there are no data on such side effects.

Fears that the creatine additives can give an additional burden to the kidneys and liver, were not confirmed when taking the studied doses of creatine by healthy people. The only documented side effect of taking creatine is an increase in body weight.

Data on the long-term harmless effects of creatine are absent. The Committee for the Protection of Competitions and Medical Aspects of Sports NCCA initiated research on long-term intake of supplements, as well as the predisposition of some people to negative side effects.

Currently, the recommended dose is 20-25 g per day for 5-7 days, then 5 g per day. If there is no need for further consumption of the additive, the period of washing out of creatine to reach its normal level in muscles lasts approximately 4 weeks.

[17], [18], [19], [20]

Side effects of the creatine

Creatine can cause weight gain, possibly due to increased muscle mass and apparent increases in serum creatinine levels. It is also reported about minor symptoms of the gastrointestinal tract, dehydration, electrolyte imbalance and muscle cramps.

[15], [16]