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SPORTS MEDICINE
ERGOGENIC AID
CREATININE MONOPHOSPHATE
Creatine is used in muscle cells to store energy for sprinting and explosive exercise.
Athletes can increase the amount of creatine in muscle by taking creatine supplements.
Although some studies report no ergogenic effect, most indicate that creatine
supplementation (e.g. 20 g per day for 5 to 7 days) increases sprint performance by 1-5%
and work performed in repeated sprints by up to 15%. These ergogenic effects appear to be
related to the extent of uptake of creatine into muscle. Creatine supplementation for a
month or two during training has been reported to promote further gains in sprint
performance (5- 8%), as well as gains in strength (5-15%) and lean body mass (1-3%).
The only known side effect is increased body weight Each year athletes spend more than one
hundred million dollars on dietary supplements in the hope of improving their physical
appearance and athletic performance. Today's most popular ergogenic aid is creatine. Its
use is prevalent in high school, college, and professional athletic programs, and some
Olympic contenders have used it. More than one hundred companies sell a creatine product.
You can buy creatine in gyms, in local "health-food" stores, on the Internet,
and in General Nutrition Stores across the country. But creatine is not for everyone, and
those who decide to take it should know the risks.
Creatine was introduced as a potential ergogenic aid in 1993, and since then its use has
grown dramatically. The National Collegiate Athletic Association (NCAA) Study of Substance
Use and Abuse Habits of College Student-Athletes showed that 13.3% of those surveyed
reported using creatine.Creatine is an organic compound made by the liver, kidneys, and
pancreas from the amino acids glycine, methionine, and arginine. From these sites of
synthesis, creatine is transported
to the skeletal muscles. Creatine exists in two forms in muscle: as free creatine and as
creatine phosphate, which makes up two- thirds of the total creatine in the body.
In addition to being synthesized by the body, creatine also comes from the consumption of
meat and fish products. There is no Recommended Dietary Allowance (RDA) for creatine, but
1 to 2 grams per day is what researchers have estimated as the daily requirement.
Typically, about one gram per day is made by the body, and one gram per day is consumed in
the diet.
During quick bursts of activity, creatine plays a role in energy production. When muscles
contract, adenosine triphosphate (ATP) is used to fuel the movement. ATP provides energy
by releasing one of its phosphate molecules, and then it becomes another compound called
adenosine diphosphate (ADP). A muscle has only enough ATP stored to perform high-intensity
muscle contractions for about 10 seconds. For the energy system to continue, more ATP must
be produced.
Creatine phosphate gives its phosphate molecule up, to ADP to create more ATP. The ability
to regenerate ATP, then, depends on the supply of creatine phosphate in the muscles.
Creatine is claimed to increase energy, increase muscular strength, produce greater and
faster muscle gains, improve endurance, delay fatigue, and aid in burning fat. It is sold
in a variety of forms: pills, powders, capsules, liquids, fruitchew candy, and a
"just-add-water" single-serving form.
Some products combine creatine with other substances like citrate or dextrose, or with
various vitamins, minerals, and amino acids. The marketers claim that these additives
provide greater benefit to the athlete.
In the early 1990s researchers started to look at the impact of creatine supplementation
on exercise performance. Since then, research has suggested that creatine may have a
future as an ergogenic aid. In several studies, subjects taking creatine have demonstrated
significant improvement in short bouts of activities thatrequire both power and strength
such as sprinting, knee extensions, and benchpress exercises.
According to current theory, creatine supplementation increases the bioavailability of
creatine phosphate in the skeletal muscle cells. This increase is believed to enhance
muscle performance by allowing faster resynthesis of ATP to provide energy for brief,
high-intensity activities, and by buffering the intracellular hydrogen ions that are
associated with lactate production and muscle fatigue. So it's thought that creatine's
ergogenic effect may be to increase the force of muscular contraction and prolong
anaerobic exercise. Studies also show that creatine supplementation may lead to an
increase in body mass. The reported increase has ranged from 0.8 to 1.8 kg, with some
reports of a 3-kg gain. It is unclear whether the weight gain is due to increased muscle
mass or water retention. Though the amount of creatine phosphate in muscle may be
increased significantly with supplementation, there are factors that seem to affect the
absorption of creatine ingested as a supplement. One such factor is the presupplementation
level of the individual. Athletes with low to normal creatine levels, such as vegetarians,
show a greater increase in creatine stores after supplementation, and they are more likely
to benefit.Some research suggests that there may be an upper limit of creatine storage in
human muscle. If this is correct, supplementation will be beneficial only to those whose
creatine levels are below the maximum storage level.
Dietary factors may also influence the absorption of creatine. Some studies have suggested
that caffeine consumption may decrease the benefits of creatine supplementation. Other
studies show that creatine stores were increased significantly when creatine ingestion was
followed by carbohydrate consumption since the uptake of creatine by the muscles is
believed to be enhanced in the presence of insulin.
Research indicates that 20 to 25 grams of creatine per day increases the creatine content
in muscle by 20% to 30%. So proponents of supplementation say that the dosage required to
increase creatine stores to their maximum level is about 20 grams per day for 5 to 6 days
(dividing the dose into 4 doses of 5 grams). After this "loading phase" of
supplementation, 3 to 5 grams per day is supposed to be the maintenance dose.
Many athletes believe that "if a little is good, more must be better," and they
take more than the maintenance dose of creatine. But no one really knows what such large
doses will do in the body. Some health professionals worry that these doses may lead to
dehydration or that very high doses may not be excreted by the kidneys. In any case, since
there seems to be a saturation limit for creatine in the muscles, oversupplementation is
pointless. Research suggests that only athletes who participate in activities that are
intermittent or whose sport requires a large body mass may benefit from creatine
supplementation.
Such activities include powerlifting, bodybuilding, football, and track-and-field events
such as shot-put and javelin. Despite claims to the contrary, there is no evidence that
creatine supplementation can enhance endurance-exercise performance, such as long-distance
running or swimming. In fact, the weight gain associated with supplementation may actually
have an adverse effect on such endurance activities.
The International Olympic Committee does not include creatine on its list of banned
substances. Because creatine is a dietary component, it would be difficult to determine
who might be taking creatine supplements and who might be eating large amounts of meat.
Athletes taking creatine have reported muscle cramps, pulls, and tears, as well as stomach
distress. Far more worrisome is the uncertainty of how much is too much. Some health
professionals are concerned that consuming more than 30 grams per month could lead to fat
accumulation in the liver.
In addition, all of the studies that have been done to date have looked at creatine use
for a short period of time, generally about a month. No one knows the effects of
long-ten-n creatine supplementation. The NCAA is currently reviewing proposals for
research on the short- and long-term effects of creatine supplementation. The research to
date has been performed primarily on college-age, athletic males, and the results may not
apply to teenagers, women, older adults, or individuals with varying levels of fitness.
Creatine supplementation should especially be discouraged among teenage athletes since
supplementation has not been studied in this population, and its effect on growth and
development are completely unknown. The NCAA has urged that all athletes view with extreme
caution the prospect of taking creatine.
As with many other alleged ergogenic aids, creatine seems so promising to so many--but the
promise rests on a pile of unknowns, which in turn may hide dangers that no coach,
athlete, or parent should ever accept.