As part of our continuing effort to service and educate our membership, each Thursday the U.S. Soccer Communications Center will send out an informative article from one of its departments. Once a week, we will post an article/paper/essay inbox that will hopefully enhance your enjoyment and knowledge of the game of soccer - on and off the field. On the second Thursday of each month, we will look into the world of the sports medicine.
Creatine Use in Soccer
By Dr. Donald T. Kirkendall
Clinical Professor, University of North Carolina
Many soccer players and coaches are asking questions about the use of creatine for improving performance. A full scientific summary of creatine use written by the USOC is available upon request from the USOC Sport Science and Technology department. What follows is a summary of information regarding the use of creatine.
What is creatine and why might it have an effect?
Creatine is naturally found in the body and is also in the diet (from meat and fish). Its main use is the transfer of energy in cells. The thought is that a greater intake of creatine will help in the rapid turnover of energy during exercise. The use of creatine is not banned by the USOC, IOC, NCAA or FIFA, but sport organizations, such as U.S. Soccer, are looking closely at this issue and do not endorse its use.
How does it work?
High intensity, intermittent exercise like soccer needs a rapid transfer of energy and creatine plays a critical role in energy transfer. Many studies have shown that high intensity work and recovery after and between bouts of high intensity work can be improved with creatine. Most of these studies use weight training or limited repeats of sprinting in a laboratory. Low intensity, long duration exercise requires a steady production of energy at a slow rate. Creatine does not improve aerobic (cycling or running) performance. Recovery from high intensity exercise is enhanced with creatine supplementation. If athletes recover faster, then perhaps they can begin the next exercise session sooner or they can train at a higher intensity. Either method increases the quality of training. This has not been studied systematically, yet the use of creatine as a training aid (as opposed to a performance aid on “game day”) has been practiced in many sports.
Creatine Supplementation for Soccer Players
Most research about creatine is laboratory-based and has little application to any playing field. Creatine has been shown to improve performance in high intensity exercise (e.g. weight lifting, sprinting), but those exercise sessions were very short (e.g. six 60m sprints) which is far below soccer training or competition. There is no data to suggest that creatine supplementation will improve performance for soccer players during play. Creatine may help lead to faster recovery that may allow the player to go through higher quality training, which could lead to improved fitness and game performance. However, remember that the current work on creatine is largely for very high intensity-short duration exercises like weight lifting and sprinting and not toward the lower intensity-longer duration exercises like soccer.
We need to know more.
1. Creatine does not work in everybody. Some people are called “non-responders”, and there is no way to determine who will or will not respond.
2. Some athletes complain of muscle and gastrointestinal cramping, but there is little scientific evidence in this area.
3. When you take a supplement, your own body’s production of that substance can be reduced, thus reducing the energy enhancing effects of creatine.
4. You must be concerned with the purity of any dietary supplements. Control of over-the-counter commercial supplements is not very rigid. Appeals by athletes who tested positive after taking a supplement that contained a substance banned by the NCAA, USOC, FIFA, IOC, etc. are summarily denied.
5. Finally, there is the concern about side effects. Rapid weight gain is the most common side effect. There are individual reports about the effect of high doses of creatine on the kidneys, but there are no long-term studies that might tell us about potential side effects of chronic use.
Ongoing, unpublished research says the use of creatine may lead to the development of chronic compartment syndromes in the legs.
Are soccer players using it?
There are reports of professional players in England and Argentina using creatine so they can train harder. There are probably many more. There is little talk of using creatine for games. A big problem is weight gain. Few women use it for this reason. The weight gain can be dramatic - 10 pounds in a week or two is not unusual.
Supplements that work:
One of the best aids is the systematic use of water. This can be a problem in soccer due to the continuous clock. Use play-stoppages and place fluids around the field to allow for water access. Two to three mouthfuls of water in the 15 minutes prior to and every 15-20 minutes during exercise is appropriate.
Still the major cause of fatigue in soccer is clearly the use of glycogen stored within muscle cells. Fatigue results when glycogen levels reach very low levels. Carbohydrate loading is one of the most practiced and effective dietary practices that can affect running volume and intensity. The diet and training of soccer players leads to less than optimal amounts of muscle glycogen. By the end of the game, adult male players have run/walked 10 kilometers (approx. 6.2 miles). More muscle glycogen allows the player to run further faster, especially late in the game. Carbohydrate ingestion should begin within the 1st hour after play. Use of a glucose polymer drink gives the body another source of fuel that can help the player run further at a higher intensity during the 2nd half of a game. Carbohydrates (moderate or high glycemic index) should make up 50-65% of the diet. Mature adults should try to consume 400-500 grams of carbohydrate over a 24-hour period during periods of moderate training and up to 600 grams per day during intense training or games.
Although it is not a substance that is banned by FIFA or the IOC, creatine is not endorsed by U.S. Soccer. As always, take precautions if using creatine, other supplements or over-the-counter drugs.
Questions can be directed to Hughie O'Malley, U.S. Soccer's Manager of Sports Medicine Administration. Hughie can be reached at firstname.lastname@example.org or at 312-528-1225.