A scientific look at the performance-enhancing effects of creatine
Creatine is probably by far the best and most studied product in the history of nutritional supplements. To look at all the research and studies conducted on creatine would be almost impossible due to the sheer number of scientific publications on this substance.
Although creatine itself is not an amino acid, creatine is produced in the body from the amino acids arginine, glycine and methionine. Creatine is found in skeletal muscle in the form of creatine phosphate - which is also known as phosphocreatine - and its primary role in the body is to provide an inorganic phosphate ion for the resynthesis of ATP during high-intensity activities that typically last for 10 seconds or less. Typical athletic activities that fit this description are moving heavy training weights or short sprints. However, as more research and studies are conducted, it appears that creatine may also have benefits for other types of athletic activities. In addition, creatine has even been shown to have benefits in the treatment of certain medical conditions.
The body normally produces about 1 gram of creatine per day and another gram is usually supplied by the diet. Studies have repeatedly shown that creatine stores in the muscles can be supersaturated by using different creatine dosing protocols. Conceptually, creatine loading is similar to the idea of carbohydrate loading, which is used to overfill muscle glycogen stores in order to increase athletic performance.
Even though there are now a whole range of different forms of creatine on the market, creatine monohydrate is still the primary creatine supplement used. At the same time, creatine monohydrate is also the form of creatine that has been used in well over 90% of the countless creatine studies conducted in recent decades.
Creatine supplementation can influence athletic performance through a number of different mechanisms. The most direct mechanism is an increase in muscle creatine phosphate stores, which are used to resynthesize ATP during high-intensity, short-duration exercise. Creatine may also help buffer changes in muscle pH and muscle acidification and conserve glycogen during short-duration exercise.
Creatine does not appear to affect aerobic metabolism. Thus, creatine supplementation can be expected to have positive effects on physical activities lasting between 10 seconds and 2 minutes, whereas little or no benefit can be expected for longer duration activities. Furthermore, creatine appears to improve recovery between short bursts of high-intensity activity such as sprinting or interval training.
The vast majority of creatine studies have examined the effects of creatine on short bursts of high intensity exercise such as weight training or sprinting. Although not all studies found a positive effect, an overwhelming majority of studies showed significant positive effects of creatine. A meta-study comparing 22 creatine studies concluded that subjects in the creatine group showed an average 8% increase in maximum strength and an average 14% increase in the number of repetitions that could be performed with a submaximal weight.
Another meta-study came to the conclusion that 70% of the creatine studies examined reported benefits of creatine during high-intensity training, while no adverse effects were observed in any study. The remaining 30% of the studies found no effect at all. The studies showed an average increase in strength and an average increase in the number of repetitions to muscle failure of 5 to 15%, an increase in sprint performance of 1 to 5% and an increase in work performed during repeated sprints of 5 to 15%.
In addition, scientific research suggests that creatine combined with exercise can increase muscle mass gains. Studies have routinely shown an increase in lean body mass with creatine supplementation, although this increase in lean body mass most likely represented a short-term increase in water retention. Used over a longer period of time, however, creatine could have potential positive effects on muscle mass gains.
These effects could simply be indirect. By allowing the exerciser to train with heavier weights or perform more repetitions with a given weight, creatine may provide a stronger stimulus for muscle growth and greater gains in muscle mass.
However, some studies also suggest more direct effects of creatine on muscle mass, including increased expression of genes involved in muscle growth and increased expression of myosin chains. Creatine may also affect cell metabolism by increasing cell volume, as the amount of water inside the cell affects a number of biological processes, including protein synthesis and degradation.
One study showed that 5 days of creatine loading reduced leucine oxidation - a marker for protein breakdown - but had no effect on protein synthesis. Interestingly, this effect was only observed in male subjects. Other studies have also observed gender-specific differences in responses to creatine. For example, women typically gain less body mass than men as a result of creatine supplementation. However, when it comes to the benefits of creatine on athletic performance, these are equally pronounced in men and women.
Not all studies show a beneficial effect of creatine on protein synthesis and protein breakdown. A number of studies conducted by the same scientists have not observed any effects of creatine on protein synthesis and protein breakdown either after resistance training or at rest. At this time, scientists are not in agreement as to whether or not creatine has direct effects on muscle growth, although the effects of creatine supplementation on strength and performance are essentially undisputed.
With one possible exception, creatine is probably one of the very few essential sports supplements for strength and power athletes interested in maximizing their performance.
Creatine is inexpensive, readily available and over a thousand scientific studies have demonstrated positive effects of this supplement for athletes. The only possible exception, which has already been alluded to, are athletes who wish to compete in a particular weight class and for whom weight gain caused by increased water retention could cause problems. However, even these athletes can use creatine during training as long as they stop taking it several weeks before an upcoming competition, giving the body enough time to eliminate the water stored by creatine supplementation.
While the benefits of creatine for strength and power athletes are well established, the role of creatine in endurance athletes is more controversial. Based on the mechanisms of action of creatine, there is really no reason to expect creatine supplements to have any noticeable endurance benefits or benefits during efforts lasting longer than three minutes. For the most part, scientific research has also confirmed that creatine has no real effect on endurance performance.
Some early research even suggested that creatine could impair the performance of swimmers and runners, most likely due to an increase in body weight. In sports where body weight is supported, such as cycling or rowing, an improvement in performance has occasionally been observed, although these results have been inconsistent.
Studies examining interrupted endurance performance during interval training have shown some benefits of creatine, which is to be expected given creatine's mechanisms of action. Considering the use of intensity and interval training in endurance athletes, creatine may play a role in improving overall exercise performance and adaptation to exercise in endurance athletes as well.
There is other research suggesting that creatine may be beneficial for endurance athletes, but this data is incomplete. One study conducted with rowers concluded that creatine supplementation had no effect on aerobic metabolism, but did promote an increase in lactate threshold with increasing training.
In another study, creatine improved anaerobic power release in triathletes by 18% with no effect on aerobic metabolism. Creatine supplementation for 5 days also reduced markers of muscle inflammation and muscle damage after a 30 kilometer run.
So can creatine improve endurance performance? The answer may be. Creatine could be beneficial during phases of interval training to improve the quality of training and could stimulate better adaptation to training, similar to strength and power athletes. Additionally, as many endurance events involve high-intensity efforts, such as a breakaway attempt in a cycling race, creatine could also provide some benefits here.
However, any improvements in anaerobic performance must be weighed against any weight gain that may occur, as the increase in body weight can easily negate the improvements in strength release. While the data on muscle damage is interesting, it is only preliminary and needs to be confirmed by further research.
If creatine could improve muscle recovery after extensive endurance training sessions by reducing muscle damage, then this would be a further benefit for endurance athletes. This is especially true for runners, who can suffer from extensive muscle damage due to the high impact nature of their sport. Creatine could also benefit endurance athletes by increasing glycogen storage.
Although scientific research has consistently shown an increase in performance with creatine supplementation, there appear to be some people who do not respond to creatine and there appears to be a biological profile associated with the lack of response to creatine.
People who respond to creatine tend to have the lowest baseline creatine levels, a higher percentage of type II muscle fibers, a larger muscle cross-sectional area, and a greater amount of lean body mass. People who do not respond to creatine, on the other hand, have higher creatine baseline levels, fewer type II muscle fibers, a smaller muscle cross-sectional area and less lean body mass.
One topic of debate among experts is whether caffeine has a potentially negative effect on creatine supplementation. Two studies using different performance tests showed that high doses of caffeine in the range of 5 mg of caffeine per kilogram of body weight negated the performance-enhancing effects of creatine.
Creatine appears to reduce muscle relaxation time after a muscle contraction, which is important for activities such as sprinting. High doses of caffeine, on the other hand, appear to negate this effect. The effects of low doses of caffeine are not yet known. In this context, it is interesting to note that in early creatine studies, creatine was administered dissolved in tea and an increase in performance was observed despite the low caffeine content of tea. In addition, it is not known whether caffeine can negate the benefits of creatine in activities other than sprinting, such as strength training.
Potential negative effects of creatine supplementation
There are a number of potential negative side effects of creatine that have either been investigated in studies or could theoretically occur. These will be looked at in more detail here. The first creatine products, which often resembled sand in consistency and were poorly soluble in liquid, frequently caused stomach problems, especially at higher doses. This is no longer an issue today, as modern creatine products generally dissolve well in liquid. The few studies that have been carried out on this subject suggest that creatine does not cause stomach problems.
However, some users still report stomach problems when taking creatine, particularly if they use high doses during a so-called loading phase. Typically, during such a loading phase, a daily amount of 20 to 25 grams of creatine is taken for a period of 5 days and the sheer amount of creatine can cause problems. The next section presents two alternative loading regimens that can be used if a traditional loading phase leads to stomach problems.
Another potential negative side effect of creatine is the impact of creatine on the liver and kidneys. Studies conducted with healthy individuals have not found any negative effects of creatine on liver and kidney function, but it cannot be ruled out that problems may occur in individuals with pre-existing liver or kidney disease. Creatine supplementation increases creatine excretion, which can lead to abnormal findings in a blood test. However, this is not a problem as it is a completely normal reaction of the body.
In the early years of creatine supplementation, there were many anecdotal reports of muscle cramps, although direct research does not support this type of side effect. Cramps are much more likely to stem from the high-intensity nature of exercise and/or electrolyte imbalances. Adequate hydration during a creatine loading phase is also a key factor. A study conducted with college football players even concluded that creatine reduces the occurrence of cramps and injuries.
A final potentially negative side effect of creatine is an increase in body weight, although this is likely to be largely due to water retention. This weight gain can range from 1 to 2.5 kilos during the first few weeks of creatine intake, although such weight gain is less in women than in men.
This is of particular interest to athletes who wish to compete in a particular weight class, as the increase in body weight caused by creatine may prevent them from competing in the desired weight class. Furthermore, in certain sports such as long distance running, where the body weight to be moved can affect performance as more mass to be moved means higher energy consumption, an increase in body weight could more than offset the performance benefits achieved by creatine.
The correct use of creatine
As mentioned above, creatine occurs naturally in foods such as meat, which contains around 4 to 5 grams of creatine per kilogram. A typical daily dose during a standard creatine loading phase is about 20 grams of creatine per day, which would be equivalent to eating 4 to 5 kilograms of meat per day.
In almost all creatine studies, creatine monohydrate was used as the creatine supplement, even though there are now many other forms of creatine on the market. Little or no scientific research has been done on these alternative forms of creatine, so there is no evidence that they are more effective or potent than creatine monohydrate.
Regardless of the form of creatine or loading regimen used, creatine levels in the muscles will eventually reach their maximum and any creatine taken in excess of this amount will be excreted unused in the urine. The only advantages that another form of creatine could have over creatine monohydrate would be a faster filling of the muscles' creatine stores or fewer stomach problems in people who are sensitive to high amounts of creatine.
The most common loading regimen consists of taking 20 grams of creatine monohydrate per day for 5 days and this regimen has been used in most scientific studies. However, there are also possible alternative loading regimens that may be preferred for different reasons. Taking 10 grams of creatine per day for 10 days as well as taking 3 to 5 grams of creatine per day for a month can be effective. At the end of each period, creatine stores will be maximally filled and the only difference between the regimens described is the time it takes to reach this maximum level.
It appears that insulin is required for the uptake of creatine and taking creatine with simple carbohydrates or carbohydrates and protein could increase absorption. Taking alpha-lipoic acid in a dosage of up to 1000 mg per day in combination with carbohydrates could also increase the absorption and storage of creatine. In addition, creatine uptake is increased after endurance training. Athletes who want to limit their carbohydrate intake can therefore take their creatine after training.
After the loading phase, a maintenance dose of about 5 grams of creatine per day is usually recommended to maintain the level of creatine stores in the muscles, but even without further creatine intake after the loading phase, creatine levels would remain elevated for at least 6 weeks after loading.
As mentioned above, creatine is naturally found in meat, particularly red meat. Vegetarians, as would be expected, have been found to have lower levels of creatine in their muscles and these individuals appear to derive greater benefits from creatine supplementation due to lower baseline creatine levels. Conversely, athletes who eat a lot of meat and already have relatively high creatine levels may benefit less from creatine supplementation.
Creatine monohydrate is a white, tasteless powder that dissolves quite well in liquid. It can be mixed with any liquid and, as already mentioned, the combination of creatine with carbohydrates and protein improves creatine absorption. The same applies to intake after endurance training. It is not yet known whether creatine intake after resistance training also improves creatine absorption.
Occasionally it is recommended to use creatine cyclically in order to prevent a possible negative effect of continuous creatine use on creatine transporters or normal creatine synthesis. In practice, such concerns are rather unfounded. Although creatine supplementation has been shown to downregulate creatine transporters in animals, a study has shown that this does not appear to be the case in humans. Even a theoretically possible downregulation of the body's own creatine synthesis through creatine supplementation should not be an issue, because as long as a maintenance dose of creatine continues to be taken, creatine phosphate levels in the muscles remain elevated above normal.
Final words
As mentioned above, creatine is probably by far the most studied sports supplement in the history of the supplement industry. Due to its well-documented effects, it is a must-have for strength and power athletes in particular. In addition, creatine may also have some benefits for endurance athletes.
Whether one uses a typical loading phase with 20 grams of creatine per day for 5 days or a longer-term approach with 10 grams of creatine per day for 10 days or 3 to 5 grams of creatine per day for 30 days is irrelevant, as at the end of each of these loading phases the muscles' creatine stores will be maximally filled. During the loading phase, the daily dose is divided into several doses of 3 to 5 grams each, one of which should be consumed with the protein-carbohydrate shake after training. After the loading phase, a maintenance dose of 3 to 5 grams of creatine per day is used, which should be taken on training days after training and on non-training days with any meal.