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Critically evaluate the use of Creatine in strength and conditioning
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Ergogenic drugs are substances that are used to enhance athletic
performance. These drugs include illicit substances as well as compounds
that are marketed as nutritional supplements. Professional and elite athletes
have used many such drugs widely for several decades. However, in recent
years, research indicates that younger athletes are increasingly experimenting
with these drugs to improve both appearance and athletic abilities. Ergogenic
drugs that are commonly used by youths today include anabolic-androgenic
steroids, steroid precursors (androstenedione and dehydroepiandrosterone),
growth hormone, creatine, and ephedra alkaloids. Reviewing the literature to
date, it is clear that children are exposed to these substances at younger ages
than in years past, with use starting as early as middle school. Anabolic
steroids and creatine do offer potential gains in body mass and strength but
risk adverse effects to multiple organ systems. Steroid precursors, growth
hormone, and ephedra alkaloids have not been proven to enhance any
athletic measures, whereas they do impart many risks to their users. To
combat this drug abuse, there have been recent changes in the legal status of
several substances, changes in the rules of youth athletics including drug
testing of high school students, and educational initiatives designed for the
young athlete. This article summarizes the current literature regarding these
ergogenic substances and details their use, effects, risks, and legal standing.
Creatine is an amino acid, like the building blocks that make up proteins.
Creatine in the form of phosphocreatine (creatine phosphate) is an important
store of energy in muscle cells. During intense exercise lasting around half a
minute, phosphocreatine is broken down to creatine and phosphate, and the
energy released is used to regenerate the primary source of energy,
adenosine triphosphate (ATP). Output power drops as phosphocreatine
becomes depleted, because ATP cannot be regenerated fast enough to meet
the demand of the exercise. It follows that a bigger store of phosphocreatine
in muscle should reduce fatigue during sprinting. Extra creatine in the muscle
may also increase the rate of regeneration of phosphocreatine following
sprints, which should mean less fatigue with repeated bursts of activity in
training or in many sport competitions (Kreider., 1998). Creatine is formed
from glycine, arginine, and methionine and is naturally produced by the liver,
kidneys, and pancreas. After production, creatine is transported to muscle,
heart, and brain, with 95% of bodily stores remaining in muscle.
The body synthesizing creatine from amino acids provides about half of the
daily needs of creatine. The remaining daily need of creatine is obtained from
the diet. Meat or fish are the best natural sources. For example, there is about
1g of creatine in 250g of raw meat. Dietary supplementation with synthetic
creatine is the primary way athletes "load" the muscle with creatine. Daily
doses of 20g of creatine for 5-7 days usually increase the total creatine
content in muscle by 10-25%. About one-third of the extra creatine in muscle
is in the form of phosphocreatine (Harris., 1992; Balsom et al., 1995).
The daily requirement of creatine is 2g, with this amount provided half from
endogenous production and half from normal diet (Balsom et al., 1994).
Muscle creatine stores are in a balanced equilibrium with creatine and
phosphocreatine interconverted via creatine kinase. Phosphocreatine
provides energy to the muscle via its dephosphorylation, which donates a
phosphate to adenosine diphosphate producing adenosine triphosphate (Fig
1). Aerobic recovery time then allows for the restoration of phosphocreatine.
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Phosphocreatine availability is considered the limiting factor in short, highintensity activities, as it provides muscle with the major energy source over
the first 10 seconds of anaerobic activity after free adenosine triphosphate is
consumed in the first 1 second of action (Fig 2) (Clark., 1997).
Figure 1. Interconversion of phosphocreatine and creatine producing
adenosine triphosphate
Figure 2. Time-dependent, dominant energy source for muscle activity
Investigations into the tissue level effects of oral creatine seem to show
several changes. Supplementation can cause an ∼20% increase in muscle
phosphocreatine stores, quicken the replenishment of phosphocreatine during
recovery, and buffer lactic acid as hydrogen ions are consumed during the
dephosphorylation of phosphocreatine, which potentially delays fatigue onset
(Fig 2) (Harris et al., 1992).
Dosing
Creatine is first recommended to be taken in a loading phase, with athletes
consuming 5g, 4 times per day for the first 4 to 6 days. The standard dosing
then is 2 g/day for the next 3 months. Creatine taken in excess of this amount
seems to be excreted via the kidneys (Clark., 1998). A month of abstinence is
standard practice after each use cycle. The Physician's Desk Reference notes
that athletes should consume 6 to 8 glasses of water per day while taking
creatine to prevent dehydration. Absorption of oral creatine does vary with
diet. Carbohydrate-rich fluids tend to increase creatine absorption, whereas
caffeine impairs its uptake (Green et al., 1997).
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Effects
Creatine supplementation does appear to have athletic benefits. However,
nearly 30% of athletes do not see benefits with creatine use, thereby falling
into a category of “nonresponders” who are theorized to have already
maximal phosphocreatine stores (McDevitt., 2003). Most common,
performance effects are seen in increasing strength and outcomes in shortduration, anaerobic events. Studies do not show improved endurance
performance as expected given that prolonged muscle activity depends on
aerobic glycolysis (Engelhardt et al., 1998). In a well-controlled setting, Volek
et al performed a double-blinded study that examined 12 weeks of creatine
use including standard loading and maintenance phases in recreational
weightlifters. In those athletes who were taking creatine, significant increases
in fat-free body mass; bench press maximal lift; peak power production in sets
of repeated jump squats; and biopsied type I, IIA, and IIAB muscle fibers were
demonstrated.
Researchers first investigated the ergogenic effects of short-term creatine
loading. In a typical study, a creatine dose of 5 g is given four times a day for
five to seven days to ensure that muscle creatine increases. A control group is
given a placebo (glucose or some other relatively inert substance) in a
double-blind manner (neither the athletes nor the researchers doing the
testing know who gets what until after the tests are performed). Most studies
have shown that speed or power output in sprints--all-out bursts of activity
lasting a few seconds to several minutes, is enhanced, typically by 5-8%.
Repetitive sprint performance is also enhanced when the rests between
sprints don't allow full recovery. In this case, total work output can be
increased by 5-15%. There is also evidence that work performed during sets
of multiple repetition strength tests may be enhanced by creatine
supplementation, typically by 5-15%. In addition, one-repetition maximum
strength and vertical-jump performance may also be increased with creatine
supplementation, typically by 5-10%. The improvement in exercise
performance has been correlated with the degree in which creatine is stored
in the muscle following creatine supplementation, particularly in Type II
muscle fibers (Casey et al., 1996).
Researchers have now turned their attention to longer-term creatine
supplementation. In these studies, a week of creatine loading of up to 25 g
per day is followed by up to three months of maintenance with reduced or
similar dosages (2-25 g per day). Training continues as usual in a group given
creatine and in a control group given a placebo. Greater gains are now seen
in performance of single-effort sprints, repeated sprints, and strength (5-15%)
(Kreider., 1998).
In analysis of these studies, creatine supplementation appears to be less
effective in the following situations: when less than 20 g per day was used for
5 days or less; when low doses (2-3 g per day) were used without an initial
high-dose loading period; in crossover studies with insufficient time (less than
5 weeks) to allow washout of the creatine; in studies with relatively small
numbers of subjects; and when repeated sprints were performed with very
short or very long recovery periods between sprints. It is also possible that
subject variability in response to creatine supplementation may account for
the lack of ergogenic benefit reported in these studies. In addition, there have
been reports that caffeine may negate the benefit of creatine supplementation
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(Vandenberghe et al., 1996). Consequently, although most studies indicate
that creatine supplementation may improve performance, creatine
supplementation may not provide ergogenic value for everyone.
Adverse Effects
The use of creatine in training for sport remains controversial. Unlike anabolic
steroids which have very well known and very far reaching short and long
term side effects, creatine remains legal as part of an athlete's training for
competition, and its side effects are generally thought to be much less
serious. Certain high profile celebrities have encouraged many to take
creatine, which is generally thought to increase muscle bulk, stamina and
performance by up to 10 per cent. It is reported to allow muscle tissue to
recover from training and repair itself more quickly.
Anecdotal reports from some athletic trainers and coaches suggest that
creatine supplementation may promote a greater incidence of muscle strains
or pulls. Theoretically, the gains in strength and body mass may place
additional stress on bone, joints and ligaments. Yet no study has documented
an increased rate of injury following creatine supplementation, even though
many of these studies evaluated highly trained athletes during heavy training
periods. Athletes apparently adapt to the increase in strength, which is
modest and gradual (Kreider., 1998).
There have been some anecdotal claims that athletes training hard in hot or
humid conditions experience severe muscle cramps when taking creatine,
and the cramps have been attributed to overheating and./or changes in the
amount of water or salts in muscle. But no study has reported that creatine
supplementation causes any cramping, dehydration, or changes in salt
concentrations, even though some studies have evaluated highly trained
athletes undergoing intense training in hot/humid environments. In my
experience with athletes training in the heat (e.g., during 2-a-day football
practice in autumn), cramping is related to muscular fatigue and dehydration
while exercising in the heat. It is not related to creatine supplementation.
Nevertheless, athletes taking creatine while training in hot and humid
environments should be aware of this possible side effect and take additional
precautions to prevent dehydration (Kreider., 1998).
It is the building material for muscle tissue that because it is rapidly broken
down in the body, feeds the muscles more efficiently when taken in synthetic
form. But there is a downside, and there are certainly side effects, which
some people experience, muscle cramps are among the commonest.
Muscle that grows more quickly may run out of energy supply making cramps
more likely. Since this affects skeletal muscle rather than the muscle in the
digestive system, these cramps are particularly likely in the legs and arms.
Athletes who take creatine commonly experience early weight gain of 1.6 to
2.4 kg, which can be detrimental in purely speed-based events. It is also
common for athletes to report minor gastrointestinal discomfort and muscle
cramps, although these generally do not curb use (Cogeni et al., 2002).
There have been 2 case reports of renal function compromise. One was an
athlete who had previously diagnosed focal segmental glomerulosclerosis
and experienced a transient 50% loss of glomerular filtration rate, and 1
previously healthy athlete reported transient interstitial nephritis (Pritchard et
al., 1998). However, at least 1 study of self-reported use over several years
did not show adverse renal effects (Poortmans et al., 1999). Three highly
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publicized deaths have occurred in college wrestlers who were known to take
creatine, although official autopsy results indicated that dehydration and
weight loss were at fault, not creatine Additional questions remain, as there
are no data to judge the effects of supplementation on the other tissues that
store creatine (heart and brain), the effects of chronic use, or the effects of
creatine use in minors.
Determining whether creatine supplementation has any short or long-term
side effects is an area receiving additional research attention. If there are
side effects from long-term creatine supplementation, an important issue will
be the liability of coaches, trainers, universities, and athletic governing
bodies who provide creatine to their athletes. Anyone advising athletes to
take creatine should make it clear that side effects from long-term use cannot
be completely ruled out, and that the athletes do not have to take the
supplements. It would be wise to have a formal policy for dosages to reduce
the chances of athletes taking excessive amounts (Kreider., 1998).
Incidence
Questioning younger populations, 1 study found 8.2% of 14- to 18-year-olds
using the supplement, with 75% of those users either unaware of how much
creatine they consumed or taking more than the recommended amounts
(Smith et al., 2000). Meanwhile in 2001, looking at 10- to 18-year-olds, Metzl
et al reported that 5.6% of that age group used creatine, with every grade
from 6 to 12 involved. It was also noted that 12th-graders used creatine
much like their collegiate counterparts, with that grade reporting 44% use.
Current estimates of collegiate creatine use vary from 25% to 78% of
athletes (Sallis et al., 1999).
Ethics
Creatine supplementation is not banned, but is a nutritional practice that
enhances performance nevertheless unethical? Anyone pondering this
question should consider that creatine supplementation is a practice similar
to carbohydrate loading, which is well accepted. Some are also concerned
that creatine supplementation could cause a carryover effect, whereby
athletes who have learned to take creatine are more likely to use dangerous
or banned substances. Proper education among athletes, coaches, and
trainers regarding acceptable and unacceptable nutritional practices is
probably the best way to reduce any carryover (Kreider., 1998).
Conclusion
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. More research
is needed on individual differences in the response to creatine, periodic or
cyclical use of creatine, side effects, and long-term effects on endurance
(Kreider., 1998).
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