Creatine Supplementation Literature Review for Muscle Growth and Sports Performance

Sports supplementation has become a very popular aid for athletes. Over the years, new supplements have come and gone with only a small percentage standing the test of time. Debates and controversy have arisen over the safety and effectiveness of a variety of ergogenic aids. This has led to the banning of certain performance enhancing substances. However, there are still those few that have proven to be legal, safe, and effective to the point that many high performance athletes have chosen to implement them into their nutrition program and training routine. 

Creatine has been one of the most popular and widely used supplements for over a decade. Although its effectiveness and safety have both been questioned over the years, there is a great deal of conclusive research and evidence that gives fair reason for athletes to supplement with this product. Creatine monohydrate is also considered by many to be the most popular and effective legal bodybuilding supplements on the market. 

There are specifically three major forms of creatine: monohydrate, micronized, and ethyl-ester. Creatine monohydrate is creatine in its raw and most basic form. Creatine ethyl ester is creatine monohydrate with an ester attached, which is rumored to have the highest absorption rate. Micronized creatine has smaller particles of creatine with 20 times more total surface area for greater uptake into the bloodstream and a greater absorption rate. Once creatine is synthesized in the body, it is then transported through the bloodstream to the muscles where it plays a pivotal role in energy metabolism. One of the central theories behind creatine usage is based on the scientific theories of ADP being converted to ATP. ATP is the primary energy source for the body's working muscles during intense exercise. Therefore, during periods of high intensity anaerobic work, lack of ATP seems to be the limiting factor in terms of being able to continue high intensity exercise in an efficient manner. When the body is incapable of producing ATP, large amounts of ADP can be used for fuel to create ATP if an extra phosphate is added to the ADP. Thus, creatine is the method for adding this extra phosphate, which ultimately leads to an increased supply of ATP, which is beneficial for high level performance (1). 

There are many claims surrounding creatine as being an advanced muscle building product. These claims are based on the theories of increased ATP re-synthesis from ADP as previously mentioned (1). Supplement companies also claim that higher levels of ATP lead to greater amounts of work being achieved during resistance training in high intensity anaerobic work. This leads to increased surface area of the muscle due to an increased rate of protein synthesis that is achieved through higher musculoskeletal workloads.

One of the most common claims surrounding creatine is its cell volumizing effect. This is also known as increased water retention, especially among skeptics. However, proponents of this supplement are convinced that this cell volumizing effect is a necessary component for any increase in muscle hypertrophy. Supposedly, when the muscle is volumized, it is forced to expand via added surface area in order to accommodate the extra fluids in the muscle.
For the purposes of this literature review, the research cited and reviewed will be focused on creatine monohydrate due to the fact that most of the present research has been isolated to this form of creatine. However, this does not negate the fact that micronized and ethyl ester creatines are just as effective, if not more so than creatine monohydrate. 

There have been countless studies relating to creatine and its impact on physical performance. Most studies have examined the impact on strength, muscular hypertrophy, power and speed, or endurance training. In a double blind study performed by Kreider et al (2) in which 16 physical education students performed 10 bouts of 6 seconds each on a stationary cycle with 30-second rest periods between individual bouts, the findings were significant. The results showed that individuals who took 20 g of creatine for 6 days were far more capable of maintaining cycle speed. Similar results were seen in many other studies of repeated high-intensity exercise as noted by the author.

In a double-blind study by Kreider et al (3) performed on 52 collegiate football players over a period of 28 days, the results were also positive. It was found that those who supplemented with creatine and creatine plus beta-hydroxy beta-methylbutyrate (HMB) had greater increases in lean muscle and bone mass compared to the placebo group.

In another study performed on 33 collegiate football players undergoing a 10-wk resistance training program, results showed that creatine had a greater increase in strength, muscle mass, and certain beneficial hormonal changes compared to the placebo group. Specifically, those who supplemented creatine with beta-alanine had the greatest increase in muscle mass. Also, the creatine only group and the creatine plus beta-alanine group had far greater increases in strength, muscle mass, IGF, and body fat composition than the placebo group. Therefore, this study shows that although creatine has a very positive effect on physiological markers of human performance, it appears its effectiveness is maximized when combined with other forms of supplementation such as beta-alanine. Also of further note is that recent claims by supplement companies have been marketing beta-alanine and creatine combinations as the greatest method of supplementing with creatine. 

In a study performed by Izquierdo et al (4), a group of 19 trained athletes underwent a study to determine the effects of creatine supplementation (20 grams a day for 5 days) on maximal strength, muscle power production during repetitive high-power-output exercise bouts, repeated running sprints, and other markers of exercise performance. The results showed that creatine supplementation significantly increased body mass, number of repetitions performed to fatigue, and total average power output values. Creatine supplementation also had a positive impact on the average running times during the first 5 meters of the six repeated 15-m sprints. 

In conclusion, this study showed that short-term creatine supplementation leads to significant improvements in lower body maximal strength, maximal repetitive upper and lower body high power exercise bouts, and muscular endurance. Further results also indicated enhanced repeated sprint performance and reduced fatigue in the vertical jump test following bouts of high intensity exercise. However, contrary to most scientific findings such as those found in a study performed by Zoeller et al (5), this study did not show any improvements in aerobic endurance or aerobic capacity with creatine supplementation which may be due to the short term duration of this study. On the other hand, Zoeller et al.'s (5) study showed an increase in aerobic endurance with four weeks of creatine supplementation.

Although these findings seem one sided and highly optimistic, there are numerous other studies which support the previous conclusions. In a study performed by Kilduff et al (6), five days of creatine supplementation increased body weight and fat-free body mass in resistance trained men who were classified as responders. Maximal strength and total force output during a repeated maximal isometric bench press test were also significantly greater in the creatine group compared to the placebo group. Yet, another study by Preen et al (7) indicated that creatine ingestion of 20 grams a day for only five days improved exercise performance during 80 min of repeated sprint exercise. The author goes on to note that this may be due an increased total creatine store and an improved replenishment rate of phosphocreatine, which is a common theory behind creatine supplementation.

Peeters et al. (8) noticed that creatine supplementation appears to increase strength and lean body mass when combined with a resistance training program. Increases in strength may be attributed to an increase in intramuscular phosphocreatine stores that are used to replenish ATP during high-intensity exercise. Furthermore, the gains observed with regard to lean body mass may be due to an increase in muscle protein synthesis and cell volumizing that occurs within the muscle cells (9). Thus, strength training athletes who desire gains in strength and lean body mass may benefit from creatine supplementation (e.g., football players, bodybuilders, and power lifters). Furthermore Peeters et al. found that creatine supplementation was also beneficial for endurance athletes.

Terjung et al. (10) noticed that short-term creatine supplementation (5-7 days of 20 grams a day) can lead to an improvement in performance. Most, but not all of the studies indicate that creatine supplementation significantly enhances the ability to produce higher muscular force and/or power. Terjung et al. (10) also noted that the greatest improvements in performance seem to be found during a series of repetitive high power output exercise bouts. These increased by 5-20% over that measured for the placebo group. These experimental protocols typically employed exceptionally high-power output efforts (e.g., maximal cycling and/or power jumping that can be maintained for only a short period, usually seconds) separated by fairly brief periods of rest (e.g., 20-60 s). As discussed above, these are the exercise conditions where the transitional energy contribution from PCr is likely most significant.

Rawson et al. (11) noted that even though there is considerable variability in the increase in muscle strength and weightlifting performance in subjects ingesting creatine during resistance training, subjects ingesting creatine experience an average of 8% greater increase in muscle strength than the placebo group (20% vs. 12%) and a 14% greater increase in weightlifting performance (26% vs. 12%). Additionally, untrained subjects experienced a larger increase in muscle strength following creatine supplementation plus resistance training than trained subjects (31% vs. 14%). 

Furthermore, Flanagan et al. (12) found that creatine supplementation will not increase the maximal contraction velocity or the peak power production of muscle in the non-fatigued state. Therefore, weightlifters should be aware that supplementation will not suddenly, directly increase their maximum in the snatch or clean and jerk. However, Flanagan et al. noted that creatine supplementation will delay fatigue, facilitate recovery, and increase power output in the later stages of training. This will allow the weightlifter to perform a greater workload in each training session, which over time will assist in increasing performance in maximum effort lifts. Creatine supplementation is of particular benefit during high-intensity, fatigue-inducing, and high-volume training phases. Therefore, from Flanagan et al.'s findings, it appears that creatine supplementation has been demonstrated to enhance performance when the PCr energy pathway is heavily taxed. Thus, supplementation will benefit weightlifters most when they are in periods of training where considerable muscular fatigue is induced.

From the above studies and others of similar context, it appears there are several effective ways of supplementing with creatine. The most common, seems to be a loading period of 20 grams a day for five days followed by a maintenance phase of 3-5 grams a day for 4-6 weeks or longer. Although there are many other dosage recommendations for creatine, more research is needed in order to finalize such theory and speculation. This is especially true with the insurgence of micronized and ethyl ester creatine as the claims of higher absorption rates and smaller dosages has been advocated. It also appears that creatine taken in conjunction with either beta-alanine (a fatigue and lactic acid buffering agent) or HMB (an anabolic compound), maximizes the effectiveness of the product in order to produce maximal gains in human performance.

SUMMARY AND RECOMMENDATION

After thoroughly examining the effects of creatine and the literature surrounding it, there appears to be conclusive evidence that creatine supplementation has a significant positive effect on human performance. These improvements from creatine supplementation are seen through increased lean muscle mass, increased strength and power, improvements in speed and single effort sprint performances, as well as anaerobic endurance. It also appears that, creatine when combined with either beta-alanine or HMB has the greatest positive impact on markers of physiological performance. Although creatine is considered a safe form of supplementation, there may be a concern for people with pre-existing kidney issues, as well as though who are taking ephedra or caffeine products (13). However, there has been very little scientific evidence to back up these warning claims. There also appear to be no signs of toxicity from supplementation with creatine when moderate to slightly higher doses are used.

There are two scientifically proven ways to supplement with creatine. The first is through a loading phase, in which 20 grams is taken for 5-7 days, followed by a maintenance phase of 3-5 grams a day for periods of 2-3 months at a time. The second form of supplementation is a simple protocol. That is to supplement with 3-10 grams of creatine per day for a period of 2-3 months with no loading phase. It is generally recommended to take at least 1-2 weeks off from creatine supplementation in order to maintain a proper response mechanism in the body. 

There are also current rumors among many bodybuilding professional that cycling creatine, such as 20 grams daily for a period of three days immediately followed by three days of non supplementation may be the most effective form of creatine supplementation. This process is continued for 8-10 weeks. This ensures that the cells in the body do not down-regulate and grow immune to creatine's presence in the body. However, greater research is needed to justify this cycling protocol. Creatine should also be taken with 20-90 grams of simple sugars along with large volumes of water for more rapid absorption into the muscle tissues. Lastly, consuming a small dose of creatine immediately before and after the workout may be the most appropriate times for supplementation. On off days, morning and mid-day are recommended. 

According to consumerlab.com (13) and other valid sources, some of the best creatine products on the market include: Muscletech Cell-Tech, BSN Cell Mass, EAS Phosphagen, Everlast Nutrition Premium Creatine, Phosphate Complex, GNC Pro Performance Creatine, and ISS Complete Creatine. Liquid forms of creatine should generally be avoided due to the breakdown that may occur when in this state for excess time. Creatine cocktails (creatine products combined with other cell volumizing compounds) have also received a great amount of hype and publicity due to numerous claims of extreme effectiveness. However, there has been very little research on these products. Some of the more well noted creatine cocktails are NxLabs Anavol, BSN NO-Xplode, Controlled Labs Green Magnitude, and Muscletech NanoVapor.

References

1. Clark F, Joseph. Creatine and Phosphocreatine: A Review of Their Use in Exercise and Sport. Journal of Athletic Training. 1997. Jan-Mar; 32(1): 45-51.

2. Kreider, Richard B.; Ferreira, Maria; Wilson, Michael; Grindstaff, Pamela; Plisk, Steven; Reinardy, Jeff; Cantler, Edward; Almada, A. L. Effects of creatine supplementation on body composition, strength, and sprint performance. Medicine & Science in Sports & Exercise. 30(1):73-82, January 1998.

3. Kreider RB. Dietary supplements and the promotion of muscle growth with resistance exercise. Sports Med. 1999; 27:97-110.

4. Izquierdo M, Ibanez J, Gonzalez-Badillo JJ, Gorostiaga EM. Effects of creatine supplementation on muscle power, endurance, and sprint performance. Med Sci Sports Exerc. 2002 Feb; 34: 332-43.

5. Zoeller RF, Stout JR, O'kroy JA, Torok DJ, Mielke M. Effects of 28 days of beta-alanine and creatine monohydrate supplementation on aerobic power, ventilatory and lactate thresholds, and time to exhaustion. Amino Acids. 2006 Sep 5.

6. Kilduff LP, Vidakovic P, Cooney G, Twycross-Lewis R, Amuna P, Parker M, Paul L, Pitsiladis YP. Effects of creatine on isometric bench-press performance in resistance-trained humans. Med Sci Sports Exercise. 2002 Jul; 34:1176-83.

7. Preen D, Dawson B, Goodman C, Lawrence S, Beilby J, Ching S. Effect of creatine loading on long-term sprint exercise performance and metabolism. Med Sci Sports Exercise. 2001 May; 33: 814-21.

8. Peeters M, Brian, Lantz D, Christopher, And Mayhew L, Jerry. Effect of Oral Creatine Monohydrate and Creatine Phosphate Supplementation on Maximal Strength Indices, Body Composition, and Blood Pressure. The Journal of Strength and Conditioning Research: 1999. Vol. 13, No. 1, pp. 3-9.

9. YeanSub L, Jon. The Effects of Creatine Supplementation on Body Composition, Muscular Strength and Power. United States Sports Academy, The Sports Journal, 2000.

10. Terjung Ronald, Clarkson, Priscilla, Eichner E, Randy, Greenhaff L, Paul, Hespel J, Peter. The physiological and health effects of oral creatine supplementation. Journal of the Amercian College of Sports Medicine. Vol. 32, No. 3, pp. 706-717, 2000.

11. Rawson S, Eric, Volek S, Jeff. Effects of Creatine Supplementation and Resistance Training on Muscle Strength and Weightlifting Performance. The Journal of Strength and Conditioning Research: 2003. Vol. 17, No. 4, pp. 822-831.

12. Flanagan P, Eamonn. Creatine Supplementation: Implications for the Competitive Weightlifter. Strength and Conditioning Journal: 2007. Vol. 29, No. 2, pp. 60-66.

13. www.consumerlab.com. Creatine.