Creatine, a nitrogenous organic acid naturally found in vertebrate muscles, is one of the most widely studied and popular sports supplements. Its ability to enhance high-intensity exercise performance stems from its role in replenishing adenosine triphosphate (ATP), the primary energy currency of cells, through the creatine kinase/phosphocreatine (CK/PCr) system. This article explores creatine's mechanisms of action, synthesis, and potential benefits, including improved sprint performance, increased muscle mass, and enhanced recovery. It also addresses practical questions such as optimal supplementation strategies, applicability across sports, safety concerns, and effects on body composition.
Whether you're a gym regular, a weekend warrior, or a competitive athlete, you've probably heard of creatine. It's not just another trendy supplement gathering dust on store shelves—this powerhouse has earned its reputation as a go-to for boosting performance, and science is here to back it up. But what exactly is creatine, how does it work, and is it right for you? Let's dive in.
Creatine is one of the most popular sports supplements, possibly because it can improve high-intensity exercise performance when taken. When our exercise performance is enhanced, it can lead to greater training adaptations and improve our functional status. Creatine is a nitrogen-containing organic acid that stores high-energy phosphate bonds in vertebrate muscles and other tissues. It can promote the recycling of ATP, thereby quickly providing energy to muscle and nerve cells.
Michel Eugène Chevreul first discovered creatine in skeletal muscle in 1832. Later, it was named "creatine" based on the Greek word "κρέας" (kreas, meaning meat).
Function
Creatine can interconvert with phosphocreatine, so it can act on the arginine - and phosphoarginine - based systems in many invertebrates. Due to the existence of this energy transporter, the ratio of ATP to ADP is maintained at a high level. This not only ensures the high level of free energy in ATP but also minimizes the loss of adenosine (adenosine loss may lead to cell dysfunction). Such a high-energy phosphate buffer solution is also called phosphagen.
Synthesis
In the human body, creatine is mainly synthesized in the liver using arginine, glycine, and methionine. After synthesis, 95% of creatine is stored in skeletal muscles, and the remaining 5% exists in the brain, heart, and testes.
Phosphagens are widely present in all species and play an important role in maintaining energy availability. The main metabolic function of creatine is to combine with phosphoryl groups (Pi) through the enzymatic reaction of creatine kinase (CK) to form phosphocreatine (PCr). The pleiotropy of creatine is mainly related to the functions of CK and PCr (i.e., the CK/PCr system). Since the degradation of adenosine triphosphate (ATP) into adenosine diphosphate (ADP) and Pi provides free energy for metabolic activities, the free energy released by the hydrolysis of PCr into Cr + Pi can serve as a buffer for the resynthesis of ATP. This helps maintain the availability of ATP, especially during anaerobic sprinting. This is one of the reasons why supplementing with creatine can improve our performance in high-intensity exercises.
Potential Enhancing Effects of Creatine Supplementation
- Improve single and repeated sprint performance
- Increase the workload during maximum effort muscle contractions
- Increase muscle mass and strength adaptations during training
- Enhance glycogen synthesis
- Improve anaerobic threshold
- May enhance aerobic capacity through more shuttling of ATP in mitochondria
- Improve exercise capacity
- Enhance recovery ability
- Improve training tolerance
How to Supplement Creatine
Our daily diet contains approximately 1-2 grams of creatine. In this case, muscle creatine storage is about 60-80% of the maximum storage. Literature indicates that the most effective way to increase muscle creatine storage is to take 5 grams of creatine four times a day (or approximately 0.3 grams per kilogram of body weight) for 5-7 days. Once the creatine storage in muscles is completely saturated, it can be maintained by taking 3-5 grams per day. Some studies suggest that larger athletes may need to take 5-10 grams per day to maintain creatine storage. These two stages are usually referred to as the "loading phase" and the "maintenance phase".
But is the "loading phase" necessary?
A common misconception about creatine supplements is that one must go through the "loading phase" to increase muscle creatine storage before experiencing the powerful benefits of creatine supplements. However, studies have shown that a strategy of lower daily creatine supplementation (i.e., 3-5 grams per day) can increase intramuscular creatine storage, thereby improving muscle mass, exercise performance, and recovery to a greater extent. But without the "loading phase" (i.e., supplementation with a higher "loading" dose of creatine), the time it takes for intramuscular creatine to reach maximum storage will be delayed (research data indicates that the creatine accumulation in the muscles of subjects who took 3 grams per day for 28 consecutive days is similar to that of those who took 20 grams per day for 6 consecutive days).
The way to take creatine depends on individual goals. For example, if you want to maximize the benefits of creatine supplementation in a short period of time (<30 days), the creatine "loading" strategy may be more appropriate. However, if you plan to take creatine for a longer period (>30 days) or avoid the potential weight gain that sometimes occurs during the creatine "loading" period, the creatine "maintenance" strategy is a more reasonable choice.
Is Creatine Only Useful for Strength Training?
Although theoretically, creatine supplementation is mainly beneficial for participating in high-intensity intermittent resistance/strength activities, more and more evidence shows that creatine supplementation may also have beneficial effects on other activities. Data indicates that compared with supplementing carbohydrates alone, supplementing carbohydrates or carbohydrates and protein at the same time can promote more muscle glycogen storage.
Since glycogen supplementation is very important for promoting recovery and preventing overtraining during intensive training, creatine supplementation can help athletes who consume a lot of glycogen during training and/or competitions maintain optimal glycogen levels. In addition, supplementing with creatine during the recovery from exercise-induced muscle damage can reduce muscle damage and better maintain muscle performance.
Examples of Benefits of Creatine Supplementation for Different Sports
01 Increase PCr
- Track and field sprints: 60-200 m
- Swimming sprints: 50 m
02 Increase PCr resynthesis
- Basketball
- American football
- Ice hockey
- Volleyball
03 Reduce muscle acidosis
- Alpine skiing
- Water sports (e.g., rowing, kayaking)
- Swimming events: 100 m, 200 m
- Track and field events: 400 m, 800 m
- Combat sports
04 Oxidative metabolism
- Basketball
- Football
- Tennis
- Interval training for endurance athletes
05 Increase weight/muscle mass
- Bodybuilding
- Combat sports
- Weightlifting
- Rugby
- Track and field events (shot put, javelin, discus, etc.)
Is Taking Creatine Safe?
Creatine, as a popular sports nutrition supplement, is used by many athletes and fitness enthusiasts to improve exercise performance and increase muscle mass and strength. However, many people still have concerns about the safety of taking creatine. For example, some people think that creatine supplementation can cause kidney damage.
In some clinical trials on creatine supplementation, markers of kidney health, inflammation, and liver function were continuously monitored, and these indicators were not negatively affected by the corresponding creatine supplementation intervention. In addition, regarding the safety of creatine supplementation in adolescents, a review on the safety of creatine supplementation in adolescents pointed out the effectiveness of creatine supplementation in various adolescent athlete populations, and no evidence of adverse reactions was found. Moreover, short-term and long-term studies on healthy and sick populations (from infants to the elderly) have shown that when the daily intake of creatine is 0.3-0.8 grams per kilogram of body weight, creatine will not pose an adverse risk to health and may provide many benefits for exercise performance and health. Furthermore, more and more evidence supports that creatine can improve the health status of individuals as they age. For example, creatine helps reduce cholesterol and triglyceride levels, reduce liver fat accumulation, enhance blood sugar control, and increase strength and/or muscle mass.
In fact, there have been more than 20 years of research on creatine. In 2020, the U.S. Food and Drug Administration (FDA) classified creatine as generally recognized as safe. This classification indicates that the currently available scientific data on the safety of creatine is sufficient and has obtained expert consensus.
Will Creatine Increase Fat Mass?
Most sports enthusiasts are worried that taking creatine will cause an increase in fat. This worry may be because some people gain weight by supplementing with creatine. However, many research data show that creatine supplementation will not increase fat mass, and some studies have also found that creatine supplementation increases lean body mass. In a systematic review and meta-analysis involving 19 studies with a total of 609 participants, it was shown that compared with the placebo supplementation group, the participants who supplemented with creatine lost approximately 0.5 kilograms of fat mass, and the body fat percentage was significantly reduced. The research results indicate that creatine supplementation will not increase fat mass in various populations.