By Trevor Stutzman, B.S. Dietetics
Following is a brief summary of the research supporting supplementation of creatine to improve strength and sport performance in athletes and quality of life in older adults. Included is also a background of what creatine is, what its function is in the body, and what dosing strategy to use when supplementing.
Creatine is not a protein or an amino acid, but is formed from two amino acids (glycine and arginine) and classified as a nitrogenous organic acid. Creatine is synthesized in our bodies to facilitate making energy available to our muscles. Although free creatine is found in our muscle tissue, its functional state is as phosphocreatine (PCr). The muscle cell gains energy by consuming adenisine triphosphate (ATP). The muscles use PCr as one way to replenish ATP availability, since the muscle cells have limited capacity to store ATP. The rational behind consuming creatine is that the muscle will be able to generate more PCr, increasing the capacity to replenish ATP stores, and therefore providing the muscles with more energy to do work, increasing anaerobic endurance. The ATP-PCr system is most active in activities lasting up to 10 seconds, thus supplementation will most improve performance during this time frame. However, research has also supported creatine increasing endurance for anaerobic activities lasting 10 seconds to 2 minutes,1 as well as increasing power outputs in phases of longer endurance events.2 In addition to increasing anaerobic endurance, creatine promotes strength by increasing muscle hypertrophy, buffering acidity in muscles, and stimulating the breakdown of sugars for energy. Consumed in its proper amount, creatine is a natural and safe supplement, which is supported by research to increase strength, increase lean body mass, and reduce injuries in athletes and disease in the aging population.
Creatine is a natural supplement as it is consumed in the average human diet. Meat and fish, specifically beef, pork, salmon, and herring, contain about half a gram of creatine per three-ounce serving. Common supplementation dosing regimens range from 2-5 grams, which is why creatine is taken as a supplement in powder form. It is important to note that just because a supplement is natural doesn’t make it safe. Creatine is a relatively new supplement to reach the market, and due to an early lack of research there have been many anecdotal and media driven claims that creatine isn’t safe. The most common claims are that creatine causes muscle cramps and dehydration, as well as causing liver and kidney damage. However, research has not found these claims to be true. Muscle cramping and dehydration are common among football players, especially during two-a-day practices in the hot summer months. A study performed on 38 Division I football athletes observed that creatine actually decreased the amount of muscle cramps, heat illness, and dehydration during the season.3 In addition, creatine supplementation decreased the number of total injuries in the athletes. A meta-analysis of 10 studies also confirmed that creatine does not affect the athletes ability to dissipate heat from the body or negatively affect fluid balance.4 As for organ function, a study on Division II football players observed that long-term creatine use has no detrimental effects on liver or kidney function.5 However, individuals with a liver or kidney disease should consult their physician before taking creatine. The only common side effect to creatine supplementation is an increase in body mass, which should be considered by athletes who need to make weight for competitions. However, the average weight gain is relatively low, reaching 2 kg on average.6,7
The most common creatine dosing strategy implies a high-dose loading period in order to quickly increase creatine content in the muscle, followed by a long-term lower dosage to maintain creatine content. The suggested amount during loading is 0.3 g/kg of creatine for 6 days (5-8g 4 times a day), followed by 0.03 g/kg thereafter (2-3g per day).8,9 Although higher doses appear to be safe, there is a lack of research on the effect higher doses might possess.
Advantages athletes gain when taking creatine include increased strength and sprint endurance, increase fat-free body mass, and reduction in injuries. Creatine works mainly to increase the functionality of training in athletes,10 and more productive training constitutes greater sport performance. For example, three separate studies were performed on collegiate football players, with the parameter of note being in the bench press for one repetition maximum effort (1RM).11-13 In each study one group of subjects consumed creatine and performed resistance training, while the other group only resistance trained over a period of multiple weeks. At the end of the trials, the subjects taking creatine improved twice as much as the subjects only resistance training. Creatine also improves sprint performance. In a study on 100 meter sprinters, after short term supplementation, average times of subjects taking creatine were reduced by a tenth of a second.14 Training times in shorter consecutive 60 meter bouts were also significantly improved. Creatine is well known to increase fat-free mass, however this gain is often associated to increased water retention in the muscle. During initial creatine supplementation (the loading phase), muscle cells do retain more water, however hydrated muscle cells promote protein synthesis and prevent protein degradation, increasing muscle hypertrophy over time.15 In a study assessing creatine supplementation after a period of 9 weeks, fat free mass and water retention in muscle compartments were measured, and an increase in mass was associated with greater dry matter in the muscle and not water retention.7 Creatine also reduces the prevalence of injury in athletes. A study on Division I football players observed a decrease in total injuries for athletes supplementing creatine.3 Creatine has been attributed with having neuroprotective properties, which could aid in concussion recovery and prevention.16 In one study, subjects with traumatic brain injuries (concussions or worse events) recovered from their injuries faster after supplementing with creatine.17
Creatine also has benefits for the aging population, including increased muscle mass and improved neuromuscular and cognitive function. As discussed above, creatine supplementation along side resistance exercise increased muscle mass and strength. Depending on the physical ability of older adults, sometimes resistance exercise is not an option. However, creatine supplementation independent of exercise has still been observed to improve muscle strength and endurance, increase bone strength, and delay atrophy of muscle in older adults.18 Creatine also displays protective effects for some neurodegenerative diseases, notably Huntington’s disease and Parkinson’s disease.19 In addition, there are studies that have observed increases in cognition after creatine supplementation in older adults.20-21
Creatine is one of the most research-supported supplements on the market today. Almost every type of athlete can benefit from the effects of creatine, as well as aging adults who are looking to improve their quality of life either physically or cognitively. Creatine most specifically applies to athletes who rely on strength and power in their sports performance, however creatine can also improve general muscularity, training efficiency, and intermittent bursts of power in endurance centered sports. Creatine also applies to every sport in that it reduces the prevalence of injury, dehydration and muscle cramps. To reinforce the effect creatine supplementation has on muscular strength, the most notable advantage, additional research studies are cited below.22-30
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