Database: Ovid MEDLINE(R) <1966 to January Week 3 2004>
Search Strategy: (Role of Creatine in Sports Performance)
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Creatine/ (4206)
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Creatine Kinase/ (17671)
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exp sports/ or exp exertion/ (111424)
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performance.tw. (201558)
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1 and 3 and 4 (128)
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2 and 3 and 4 (89)
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5 or 6 (213)
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*Creatine/ or *Creatine Kinase/ (8387)
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7 and 8 (128)
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limit 9 to (human and english language) (124)
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limit 10 to ovid full text available (19)
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limit 10 to yr=1996-2004 (108)
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limit 12 to review (17)
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limit 12 to local holdings (25)
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11 or 13 or 14 (57)
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(performance and creatine).ti. and 12 (61)
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16 not 15 (34)
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from 17 keep 3-5,8,11,16-19,22-27,29,31,33-34 (19)
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15 or 18 (76)
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limit 18 to yr=2000-2004 (9)
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15 or 20 (66)
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limit 21 to yr=1998-2004 (54)
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from 22 keep 1-54 (54)
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from 22 keep 1-54 (54)
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<1>
Unique Identifier
9715740
Authors
Maganaris CN. Maughan RJ.
Institution
University Medical School, University of Aberdeen, Foresterhill, UK.
Title
Creatine supplementation enhances maximum voluntary isometric force and
endurance capacity in resistance trained men.
Source
Acta Physiologica Scandinavica. 163(3):279-87, 1998 Jul.
Abstract
The present study examined the hypothesis that creatine (Cr) supplementation
can increase the performance of isometric exercise in subjects engaged in a
strength training program. Ten male subjects were tested in three experimental
trials 7 days apart (days 1, 8 and 15). In each trial the subjects' maximum
voluntary force of contraction (MVC) was measured in both legs and isometric
endurance capacity at 80, 60, 40 and 20% of MVC of their stronger leg (knee
extensor group) was measured with a 4-min rest between contractions.
Additionally, the subjects' isometric endurance capacity at 80% of MVC of their
weaker leg was measured in 10 repeated bouts interspersed with 2-min rest. A
double-blind cross-over design was adopted for administering Cr or placebo.
Subjects were randomized into either the Cr-placebo (Group A: days 2-6: 10 g
day-1 of Cr; days 9-13: 10 g day-1 of glucose polymers) or the placebo-Cr group
(Group B reverse supplementation order). The daily diet was analysed, and urine
samples from 24-h collections were subjected to Cr and creatinine analysis. In
each subject, approximately 18 g (35%) of Cr was eliminated in the urine during
the Cr supplementation period. MVC increased by about 10% (P < 0.01 in the
weaker leg, P < 0.05 in the stronger leg) and body mass increased by 1.7 +/- 0.4
kg (2.3%, P < 0.01) and 1.8 +/- 0.3 kg (2.1%, P < 0.01) in groups A and B,
respectively, after Cr supplementation, while energy intake and diet composition
remained constant throughout the study. The subjects' endurance capacity
increased (P < 0.05) in all the bouts after Cr supplementation. Muscle
hypertrophy in response to Cr supplementation and weight training may explain
the findings of the present study.
<2>
Unique Identifier
10208711
Authors
Apgar B.
Title
Do 'health products' really help athletic performance?.
Source
American Family Physician. 59(7):1990, 1992, 1999 Apr 1.
<3>
Unique Identifier
10919967
Authors
Casey A. Greenhaff PL.
Institution
Centre for Human Sciences, Defence Evaluation and Research Agency,
Farnborough, United Kingdom. acasey@dera.gov.uk
Title
Does dietary creatine supplementation play a role in skeletal muscle
metabolism and performance?. [Review] [59 refs]
Source
American Journal of Clinical Nutrition. 72(2 Suppl):607S-17S, 2000 Aug.
Abstract
Fatigue sustained during short-term, high-intensity exercise in humans is
associated with the inability of skeletal muscle to maintain a high rate of
anaerobic ATP production from phosphocreatine hydrolysis. Ingestion of creatine
monohydrate at a rate of 20 g/d for 5-6 d was shown to increase the total
creatine concentration of human skeletal muscle by approximately 25 mmol/kg dry
mass, some 30% of this in phosphorylated form as phosphocreatine. A positive
relation was then shown between muscle creatine uptake and improvements in
performance during repeated bouts of maximal exercise. However, there is no
evidence that increasing intake > 20-30 g/d for 5-6 d has any potentiating
effect on creatine uptake or performance. In individuals in whom the initial
total creatine concentration already approached 150 mmol/kg dry mass, neither
creatine uptake nor an effect on phosphocreatine resynthesis or performance was
found after supplementation. Loss of ATP during heavy anaerobic exercise was
found to decline after creatine ingestion, despite an increase in work
production. These results suggest that improvements in performance are due to
parallel improvements in ATP resynthesis during exercise as a consequence of
increased phosphocreatine availability. Creatine uptake is augmented by
combining creatine supplementation with exercise and with carbohydrate
ingestion. [References: 59]
<4>
Unique Identifier
12501003
Authors
Lemon PW.
Institution
Exercise Nutrition Research Laboratory, the University of Western Ontario,
London, ON.
Title
Dietary creatine supplementation and exercise performance: why inconsistent
results?. [Review] [61 refs]
Source
Canadian Journal of Applied Physiology. 27(6):663-81, 2002 Dec.
Abstract
Over the past few years there has been considerable interest in both the use
of creatine (Cr) supplementation by athletes and the documentation of its
effects by scientists. Some believe that this nitrogen-containing compound found
in meat and fish has a performance-enhancing capability as important for brief
intense exercise efforts as dietary carbohydrate is for activities where
glycogen supplies limit performance. The mechanisms thought to be responsible
for any ergogenic effect of acute (few d) Cr supplementation include: increased
stores of muscle phosphocreatine (PCr), faster regeneration of PCr during
exercise recovery, enhanced adenosine triphosphate (ATP) production from
glycolysis secondary to increased hydrogen ion buffering, and/or possible
shortened post contraction muscle relaxation time. With chronic (wk mo)
supplementation when combined with strength training, Cr may alter muscle
protein metabolism directly (via decreasing protein breakdown or increasing
synthesis) and/or indirectly as a result of a greater training load made
possible by its acute ergogenic effects on strength and power. Cr
supplementation is not banned by the International Olympic Committee and, with
the exception of a small increase in body mass (approximately 1 kg) over the
initial 36 d, does not appear to have any adverse side effects, at least with
short-term use. Few scientific data are available for more prolonged use (mo or
y) but considering the large numbers of athletes using Cr over the past 6+ y and
the absence of reported problems, it may be that the often discussed somewhat
nebulous long term adverse effects are presently being overestimated. Intakes of
285-300 mg Cr/kg body mass 1 over 36 d or 3050 mg/kg body mass 1 over
approximately 4 wk are sufficient to produce benefits (muscle mass and high
intensity power gains); however, not all study results are consistent. The focus
of this review is to outline some possible explanations for the inconsistent
observations reported in the literature. Clearly, if proven to be consistent the
benefits of Cr supplementation could extend far beyond the athletic arena to
include individuals who experience muscle weakness for a variety of other
reasons (e.g., age/disuse, muscle disease, exposure to microgravity, etc).
[References: 61]
<5>
Unique Identifier
10638338
Authors
Jacobs I.
Institution
Defence and Civil Institute of Environmental Medicine, Toronto, Ontario.
Title
Dietary creatine monohydrate supplementation. [Review] [56 refs]
Source
Canadian Journal of Applied Physiology. 24(6):503-14, 1999 Dec.
Abstract
This paper summarizes and interprets the research published about
physiological aspects of dietary supplementation with creatine monohydrate and
the effects on physical performance. A nitrogenous molecule that occurs
naturally in the flesh consumed by meat-eaters, creatine is also synthesized
endogenously and is stored primarily in skeletal muscle. The research literature
in which direct measurements of muscle creatine content have been reported
indicates that most, but not all, subjects respond to "creatine loading" by
increasing the total intramuscular concentration of creatine, including the
concentration of phosphocreatine. The factors that affect muscle creatine stores
are reviewed, as are the widely ranging results on physical performance. The
mechanism of action by which increased intramuscular creatine could enhance
performance is not yet clear. Original speculation was that increased
phosphocreatine levels prior to commencing exercise, in conjunction with higher
free creatine concentration, would prolong the time required until performancelimiting levels of phosphocreatine were reached during intense exercise. It was
also speculated that restoration of phosphocreatine levels between bouts of such
exercise would be more rapid. More recent studies question such speculation.
This review includes a discussion of what is known about the health risks and
side-effects associated with creatine loading. The paper concludes with
speculation about the unprecedented attention given to creatine supplementation
by recreational and competitive athletes and the media. [References: 56]
<6>
Unique Identifier
9884793
Authors
Juhn MS. Tarnopolsky M.
Institution
Department of Family Medicine, University of Washington School of Medicine,
Seattle, USA.
Title
Oral creatine supplementation and athletic performance: a critical review.[see
comment][erratum appears in Clin J Sport Med 1999 Apr;9(2):62]. [Review] [67
refs]
Comments
Comment in: Clin J Sport Med. 1999 Apr;9(2):119; PMID: 10442629
Source
Clinical Journal of Sport Medicine. 8(4):286-97, 1998 Oct.
Abstract
OBJECTIVE: To review and summarize the current data on oral creatine
supplementation regarding its potential efficacy in athletic performance,
mechanism of action, and metabolism. DATA SOURCES AND STUDY SELECTION: Medline
was searched using terms relating creatine supplementation to athletic
performance. Studies that evaluated the effects of oral creatine supplementation
on exercise performance in humans were selected for inclusion. Selected studies
on muscle metabolism and exercise physiology were included if they provided
useful information relative to creatine. Additional references were reviewed
from the bibliographies of selected studies. DATA EXTRACTION AND SYNTHESIS: To
summarize efficacy, extracted data were listed in table format, grouping studies
together by type of activity and efficacy on performance. Whenever possible, the
effect of creatine supplementation was quantified. Proposed explanations for
creatine's efficacy or lack thereof in a particular type of activity were
formulated. CONCLUSIONS: In laboratory settings, creatine supplementation is
ergogenic in repeated 6-30-second bouts of maxima stationary cycling sprints.
The data on a single sprint or first-bout sprint of any kind are inconsistent.
The data regarding creatine's ergogenic effects on mass-dependent activities,
such as running and swimming, are not convincing, perhaps because of the side
effect of weight gain from water retention. Studies on weight lifting suggest
that creatine improves strength possibly by increasing myofibrillar protein
synthesis however, more study is needed to prove this. No ergogenic effects on
submaximal or endurance exercise are evident Individual response to creatine
supplementation can vary greatly. [References: 67]
<7>
Unique Identifier
12546637
Authors
van Loon LJ. Oosterlaar AM.
Wagenmakers AJ.
Institution
Hartgens F.
Hesselink MK.
Snow RJ.
Nutrition and Toxicology Research Institute Maastricht (NUTRIM), Department of
Human Biology, Maastricht University, Maastricht, The Netherlands.
L.vanLoon@HB.Unimaas.nl
Title
Effects of creatine loading and prolonged creatine supplementation on body
composition, fuel selection, sprint and endurance performance in humans.
Source
Clinical Science. 104(2):153-62, 2003 Feb.
Abstract
Most research on creatine has focused on short-term creatine loading and its
effect on high-intensity performance capacity. Some studies have investigated
the effect of prolonged creatine use during strength training. However, studies
on the effects of prolonged creatine supplementation are lacking. In the present
study, we have assessed the effects of both creatine loading and prolonged
supplementation on muscle creatine content, body composition, muscle and wholebody oxidative capacity, substrate utilization during submaximal exercise, and
on repeated supramaximal sprint, as well as endurance-type time-trial
performance on a cycle ergometer. Twenty subjects ingested creatine or a placebo
during a 5-day loading period (20 g.day(-1)) after which supplementation was
continued for up to 6 weeks (2 g.day(-1)). Creatine loading increased muscle
free creatine, creatine phosphate (CrP) and total creatine content ( P <0.05).
The subsequent use of a 2 g.day(-1) maintenance dose, as suggested by an
American College of Sports Medicine Roundtable, resulted in a decline in both
the elevated CrP and total creatine content and maintenance of the free creatine
concentration. Both short- and long-term creatine supplementation improved
performance during repeated supramaximal sprints on a cycle ergometer. However,
whole-body and muscle oxidative capacity, substrate utilization and time-trial
performance were not affected. The increase in body mass following creatine
loading was maintained after 6 weeks of continued supplementation and accounted
for by a corresponding increase in fat-free mass. This study provides definite
evidence that prolonged creatine supplementation in humans does not increase
muscle or whole-body oxidative capacity and, as such, does not influence
substrate utilization or performance during endurance cycling exercise. In
addition, our findings suggest that prolonged creatine ingestion induces an
increase in fat-free mass.
<8>
Unique Identifier
10410847
Authors
Kraemer WJ. Volek JS.
Institution
Department of Physical Education, Biology, Physiology, and Health Science,
Ball State University, Muncie, Indianapolis, Indiana, USA. wkraemer@bsu.edu
Title
Creatine supplementation. Its role in human performance. [Review] [66 refs]
Source
Clinics in Sports Medicine. 18(3):651-66, ix, 1999 Jul.
Abstract
Creatine supplementation is the most popular nutritional supplement today.
Although many questions remain regarding the use and benefits of creatine
supplementation, a fast-growing body of literature is starting to define both
its acute and chronic effects on human and physiologic performance. The initial
data indicate that this energetic boost of the phosphagen energy system also
helps to enhance strength and power training. Few documented side effects have
been demonstrated in the medical and scientific literature, but further
investigation is still required as to long-term use (i.e., beyond several
months). [References: 66]
<9>
Unique Identifier
11085837
Authors
Tarnopolsky MA.
Institution
Dept of Neurology/Neurological Rehabilitation, McMaster University Medical
Center, Hamilton, Ontario, Canada. tarnopol@fhs.mcmaster.ca
Title
Potential benefits of creatine monohydrate supplementation in the elderly.
[Review] [65 refs]
Source
Current Opinion in Clinical Nutrition & Metabolic Care. 3(6):497-502, 2000
Nov.
Abstract
Creatine plays a role in cellular energy metabolism and potentially has a role
in protein metabolism. Creatine monohydrate supplementation has been shown to
result in an increase in skeletal muscle total and phosphocreatine
concentration, increase fat-free mass, and enhance high-intensity exercise
performance in young healthy men and women. Recent evidence has also
demonstrated a neuroprotective effect of creatine monohydrate supplementation in
animal models of Parkinson's disease, Alzheimer's disease, amyotrophic lateral
sclerosis, and after ischemia. A low total and phosphocreatine concentration has
been reported in human skeletal muscle from aged individuals and those with
neuromuscular disorders. A few studies of creatine monohydrate supplementation
in the elderly have not shown convincing evidence of a beneficial effect with
respect to muscle mass and/or function. Future studies will be required to
address the potential for creatine monohydrate supplementation to attenuate agerelated muscle atrophy and strength loss, as well as to protect against agedependent neurodegenerative disorders such as Parkinson's disease and
Alzheimer's disease. [References: 65]
<10>
Unique Identifier
12831718
Authors
Farquhar WB. Zambraski EJ.
Institution
HRCA Research and Training Institute, Harvard Division on Aging, 1200 Centre
Street, Boston, MA 02131, USA. farquhar@mail.hrca.harvard.edu
Title
Effects of creatine use on the athlete's kidney. [Review] [26 refs]
Source
Current Sports Medicine Reports. 1(2):103-6, 2002 Apr.
Abstract
With regard to athletes attempting to improve their performance, at the
present time creatine monohydrate is clearly the most widely used dietary
supplement or ergogenic aid. Loading doses as high as 20 g/d are typical among
athletes. The majority (> 90%) of the creatine ingested is removed from the
plasma by the kidney and excreted in the urine. Despite relatively few isolated
reports of renal dysfunction in persons taking creatine, the studies completed
to date suggest that in normal healthy individuals the kidneys are able to
excrete creatine, and its end product creatinine, in a manner that does not
adversely alter renal function. This situation would be predicted to be
different in persons with impaired glomerular filtration or inherent renal
disease. The question of whether long-term creatine supplementation (ie, months
to years) has any deleterious affects on renal structure or function can not be
answered at this time. The limited number of studies that have addressed the
issue of the chronic use of creatine have not seen remarkable changes in renal
function. However, physicians should be aware that the safety of long-term
creatine supplementation, in regard to the effects on the kidneys, cannot be
guaranteed. More information is needed on possible changes in blood pressure,
protein/albumin excretion, and glomerular filtration in athletes who are
habitual users of this compound. [References: 26]
<11>
Unique Identifier
10929216
Authors
Deutekom M. Beltman JG. de Ruiter CJ. de Koning JJ. de Haan A.
Institution
Institute for Fundamental and Clinical Human Movement Sciences, Vrije
University, Amsterdam, The Netherlands.
Title
No acute effects of short-term creatine supplementation on muscle properties
and sprint performance.
Source
European Journal of Applied Physiology. 82(3):223-9, 2000 Jun.
Abstract
In a double-blind, placebo, controlled study, we investigated the acute
effects of short-term oral creatine supplementation (20 g.day-1 for 6 days) on
muscle activation, fatigue and recovery of the m. quadriceps femoris during
electrical stimulation, and on maximal performance during sprint cycling. The
quadriceps muscles of 23 well-trained rowers were stimulated at different
frequencies (10, 20, 50, 100, 150 and 200 Hz). Furthermore, 40 repetitive,
electrically stimulated (duration 220 ms, stimulation frequency 150 Hz)
concentric contractions were imposed at a constant angular velocity of 180
degrees.s-1 over a range of 50 degrees (from 90 to 140 degrees knee angle), each
extension/flexion cycle lasting 1200 ms. To determine recovery, torque was
measured at 20, 50, 80, 120, 180 and 300 s after the last contraction. In
addition, two maximal 30-s sprints were performed on a cycle ergometer with 4
min rest in between. Following short-term creatine supplementation, body mass
[mean (SEM)] increased (P < 0.05) from 85.7 (2.7) kg to 87.3 (2.9) kg. Creatine
supplementation had no effect on maximal voluntary isometric torque and muscle
activation, or on fatigue and recovery of dynamic exercise. There was also no
significant effect on peak power, time to peak power and work to peak power, or
total work during both sprints on the cycle ergometer. It was concluded that
short-term oral creatine supplementation resulted in increased body mass, but
did not enhance muscle performance or maximal output during sprint cycling.
<12>
Unique Identifier
11482548
Authors
Wiroth JB. Bermon S. Andrei S. Dalloz E. Hebuterne X. Dolisi C.
Institution
Laboratoire de Physiologie, Faculte de Medecine, Nice, France. wiroth@unice.fr
Title
Effects of oral creatine supplementation on maximal pedalling performance in
older adults.
Source
European Journal of Applied Physiology. 84(6):533-9, 2001 Jun.
Abstract
This study was conducted to investigate the effects of giving short-term doses
of creatine by mouth to healthy older male subjects, taking into account their
training status. A group of 42 volunteers was divided into three: a sedentary
group composed of elderly sedentary men [n = 14, mean age 70.1 (SEM 1.2) years],
a trained group composed of elderly trained cyclists [n = 14, mean age 66.4 (SEM
1.4) years] and a young group composed of young sedentary men [n = 14, mean age
26.0 (SEM 1.2) years]. In each group, double-blind randomization was carried
out: one half was given creatine (3x5 g x day(-1)), and the other was given an
iso-nitrogenated placebo (3x10 g x day(-1)). Before and after the 5 days during
which the supplements were given, all subjects performed five all-out 10-s
sprints separated by 60-s intervals of passive recovery, seated on a cycle
ergometer. Power output, work done and heart rate data were recorded during each
sprint. The elderly and the young sedentary subgroups given creatine showed
significant (P < 0.05) improvements in maximal power (+3.7% and +2.0%,
respectively) and work done (+4.1% and +5.1%, respectively) in the subsequent
tests. In contrast, no significant change in pedalling performances was observed
in the trained elderly subjects. The creatine did not change the exercise and
recovery heart rate profiles, in any group. Our study suggested that creatine
given by mouth increases the anaerobic power and work capacity of sedentary
people of different ages during maximal pedalling tasks. However, the level of
physical activity seems to be a determinant of the ergogenic effect of creatine
in older subjects.
<13>
Unique Identifier
10958375
Authors
Shomrat A. Weinstein Y. Katz A.
Institution
Department of Physiology and Pharmacology, Tel-Aviv University, Ramat-Aviv,
Israel.
Title
Effect of creatine feeding on maximal exercise performance in vegetarians.
Source
European Journal of Applied Physiology. 82(4):321-5, 2000 Jul.
Abstract
The effect of creatine supplementation on exercise performance in vegetarians
was examined. Creatine was ingested for 1 week by a group of vegetarians (VC)
and meat-eaters (MC); a control group of meat-eaters was fed only glucose (MG).
Exercise performance during three, 20-s maximal cycling tests (modified Wingate
anaerobic test, WAnT) was determined before and after creatine supplementation.
Blood samples were also drawn before and after exercise prior to and after
supplementation. Basal plasma creatine (after an overnight fast) averaged (SE)
11 (2) microM in VC, and 24 (2) and 23 (7) microM in MG and MC, respectively (P
< 0.05 for VC vs meat-eaters). These findings were expected, since most of the
body's exogenous creatine source is meat. There was no significant difference in
any other parameter between groups prior to supplementation. Creatine feedings
significantly increased body mass (approximately 1 kg) and mean power output
during the WAnTs (approximately 5%) to a similar extent in the VC and MC groups
(P < 0.05-0.001). These parameters were not affected by supplementation in the
MG group. Peak power output was also significantly increased by supplementation
in MC (approximately 5%, P < 0.05), but not in VC. It is concluded that
vegetarians and meat-eaters respond to creatine feedings with similar increases
in mean power output during short-term, maximal exercise.
<14>
Unique Identifier
12945830
Authors
Branch JD.
Institution
Department of Exercise Science, Physical Education, and Recreation at Old
Dominion University, Norfolk, VA 23529-0196, USA.
Title
Effect of creatine supplementation on body composition and performance: a
meta-analysis.
Source
International Journal of Sport Nutrition & Exercise Metabolism. 13(2):198226, 2003 Jun.
Abstract
BACKGROUND: Creatine supplementation (CS) has been reported to increase body
mass and improve performance in high-intensity, short-duration exercise tasks.
Research on CS, most of which has come into existence since 1994, has been the
focus of several qualitative reviews, but only one meta-analysis, which was
conducted with a limited number of studies. PURPOSE: This study compared the
effects of CS on effect size (ES) for body composition (BC) variables (mass and
lean body mass), duration and intensity (< or = 30 s, [ATP-PCr = A]; 30-150 s
[glycolysis = G]; >150 s, [oxidative phosphorylation = O]) of the exercise task,
type of exercise task (single, repetitive, laboratory, field, upper-body, lowerbody), CS duration (loading, maintenance), and subject characteristics (gender,
training status). METHODS: A search of MEDLINE and SPORTDiscus using the phrase
"creatine supplementation" revealed 96 English-language, peer-reviewed papers
(100 studies), which included randomized group formation, a placebo control, and
human subjects who were blinded to treatments. ES was calculated for each body
composition and performance variable. RESULTS: Small, but significant (ES > 0, p
< or = .05) ES were reported for BC (n=163, mean +/- SE=0.17 +/- 0.03), ATP-PCr
(n=17, 0.24 +/- 0.02), G (n=135, 0.19 +/- 0.05), and O (n=69, 0.20 +/- 0.07). ES
was greater for change in BC following a loading-only CS regimen (0.26 +/- 0.03,
p=.0003) compared to a maintenance regimen (0.04 +/- 0.05), for repetitive-bout
(0.25 +/- 0.03,p=.028) compared to single-bout (0.18 +/- 0.02) exercise, and for
upper-body exercise (0.42 +/- 0.07, p<.0001) compared to lower (0.21 +/- 0.02)
and total body (0.13 +/- 0.04) exercise. ES for laboratory-based tasks (e.g.,
isometric/isotonic/isokinetic exercise, 0.25 +/- 0.02) were greater (p=.014)
than those observed for field-based tasks (e.g., running, swimming, 0.14 +/0.04). There were no differences in BC or performance ES between males and
females or between trained and untrained subjects. CONCLUSION: ES was greater
for changes in lean body mass following short-term CS, repetitive-bout
laboratory-based exercise tasks < or = 30 s (e.g., isometric, isokinetic, and
isotonic resistance exercise), and upper-body exercise. CS does not appear to be
effective in improving running and swimming performance. There is no evidence in
the literature of an effect of gender or training status on ES following CS.
<15>
Unique Identifier
12945828
Authors
Chwalbinska-Moneta J.
Institution
Department of Applied Physiology in the Medical Research Centre of Polish
Academy of Sciences, 02-106 Warsaw, Poland.
Title
Effect of creatine supplementation on aerobic performance and anaerobic
capacity in elite rowers in the course of endurance training.
Source
International Journal of Sport Nutrition & Exercise Metabolism. 13(2):173-83,
2003 Jun.
Abstract
The effect of oral creatine supplementation on aerobic and anaerobic
performance was investigated in 16 elite male rowers during 7-day endurance
training. Before and after the daily ingestion of 20 g creatine monohydrate for
5 days (Cr-Group, n=8) or placebo (Pl-Group, n=8), subjects performed two
exercise tests on a rowing ergometer: (a) incremental exercise consisting of 3min stage durations and increased by 50 W until volitional exhaustion; (b) an
all-out anaerobic exercise performed against a constant load of 7 W/kg. Heart
rate and blood lactate concentrations were determined during exercise and
recovery. Maximal power output did not significantly differ after the treatment
in either group. The mean individual lactate threshold rose significantly after
Cr treatment from 314.3 +/- 5.0 W to 335.6 +/- 7.1 W (p<.01), as compared with
305.0 +/- 6.9 W and 308.9 +/- 5.9 W (ns), before and after placebo ingestion,
respectively. During the anaerobic test, the athletes supplemented with creatine
were able to continue rowing longer (mean increase, 12.1 +/- 4.5 s; p<.01) than
Pl-Group (2.4 +/- 8.2 s; ns). No significant differences were found between
groups in blood LA after the all-out exercise. The results indicate that in
elite rowers, creatine supplementation improves endurance (expressed by the
individual lactate threshold) and anaerobic performance, independent of the
effect of intensive endurance training.
<16>
Unique Identifier
11099372
Authors
Tarnopolsky MA. MacLennan DP.
Institution
Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada L8N
3Z5.
Title
Creatine monohydrate supplementation enhances high-intensity exercise
performance in males and females.
Source
International Journal of Sport Nutrition & Exercise Metabolism. 10(4):452-63,
2000 Dec.
Abstract
Creatine monohydrate supplementation has been shown to enhance high-intensity
exercise performance in some but not all studies. Part of the controversy
surrounding the ergogenic effect(s) of creatine monohydrate supplementation may
relate to design issues that result in low statistical power. A further question
that remains unresolved in the creatine literature is whether or not males and
females respond in a similar manner to supplementation. We studied the effect of
creatine supplementation upon high intensity exercise performance in 24 subjects
(n = 12 males, n = 12 females). Creatine monohydrate (Cr; 5g, 4x/d 3 4d) and
placebo (Pl; glucose polymer 3 4d) were provided using a randomized, doubleblind crossover design (7 week washout). Outcome measures included: 2 3 30-s
anaerobic cycle test, with plasma lactate pre- and post-test; dorsi-flexor:
maximal voluntary contraction (MVC), 2-min fatigue test, and electrically
stimulated peak and tetanic torque; isokinetic knee extension torque and 1-min
ischemic handgrip strength. Significant main effects of Cr treatment included:
increased peak and relative peak anaerobic cycling power ( 3.7%; p <. 05),
dorsi-flexion MVC torque ( 6.6%; p <.05), and increased lactate ( 20.8%; p <.05)
with no gender specific responses. We concluded that short-term Cr
supplementation can increase indices of high-intensity exercise performance for
both males and females.
<17>
Unique Identifier
10727076
Authors
Francaux M. Demeure R. Goudemant JF. Poortmans JR.
Institution
Institut d'Education Physique et de Readaptation, Universite Catholique de
Louvain, Louvain-la-Neuve, Belgium. marc.francaux@edph.ucl.ac.be
Title
Effect of exogenous creatine supplementation on muscle PCr metabolism.
Source
International Journal of Sports Medicine. 21(2):139-45, 2000 Feb.
Abstract
31P NMR was used to assess the influence of two weeks creatine supplementation
(21g x d(-1)) on resting muscle PCr concentration, on the rate of PCr repletion
(R(depl)), and on the half-time of PCr repletion (t 1/2). Body mass (BM) and
volume of body water compartments were also estimated by impedance spectroscopy.
Fourteen healthy male subjects (20.8+/-1.9 y) participated in this double-blind
study. PCr was measured using a surface coil placed under the calf muscle, at
rest and during two exercise bout the duration of which was 1 min. They were
interspaced by a recovery of 10 min. The exercises comprised of 50 plantar
flexions-extensions against weights corresponding to 40% and 70% of maximal
voluntary contraction (MVC), respectively. Creatine supplementation increased
resting muscle PCr content by approximately 20% (P= 0.002). R(depl) was also
increased by approximately 15% (P< 0.001) and approximately 10% (P = 0.026)
during 40% and 70% MVC exercises, respectively. No change was observed in
R(repl) and t1/2. BM and body water compartments were not influenced. These
results indicate that during a standardized exercise more ATP is synthesized by
the CK reaction when the pre-exercise level in PCr is higher, giving some
support to the positive effects recorded on muscle performance.
<18>
Unique Identifier
9839847
Authors
Vandebuerie F. Vanden Eynde B. Vandenberghe K. Hespel P.
Institution
Faculty of Physical Education and Physiotherapy, Department of Kinesiology,
Katholieke Universiteit Leuven, Belgium.
Title
Effect of creatine loading on endurance capacity and sprint power in cyclists.
Source
International Journal of Sports Medicine. 19(7):490-5, 1998 Oct.
Abstract
The effect of creatine loading on endurance capacity and sprint performance
was investigated in elite cyclists according to a double-blind cross-over study
design. Subjects (n = 12) underwent on 3 occasions and separated by 5 week washout periods, a 2 h 30 min standardized endurance protocol on their own race
bicycle, which was mounted on an electromagnetically braked roller-system,
whereupon they cycled to exhaustion at their predetermined 4 mmol lactate
threshold. Immediately thereafter they performed 5 maximal 10 second sprints,
separated by 2 min recovery intervals, on a Monark bicycle ergometer at 6 kg
resistance on the flywheel. Before the exercise test, subjects were either
creatine loaded (C: 25 g creatine monohydrate/day, 5 days) or were creatine
loaded plus ingested creatine during the exercise test (CC: 5 g/h), or received
placebo (P). Compared with P, C but not CC increased (p<0.05) peak and mean
sprint power output by 8-9% for all 5 sprints. Endurance time to exhaustion was
not affected by either C or CC. It is concluded that creatine loading improves
intermittent sprint capacity at the end of endurance exercise to fatigue. This
ergogenic action is counteracted by high dose creatine intake during exercise.
<19>
Unique Identifier
11719888
Authors
Romer LM. Barrington JP. Jeukendrup AE.
Institution
Sports Medicine and Human Performance Unit, School of Sport and Exercise
Sciences, The University of Birmingham, Edgbaston, Birmingham, UK.
Title
Effects of oral creatine supplementation on high intensity, intermittent
exercise performance in competitive squash players.
Source
International Journal of Sports Medicine. 22(8):546-52, 2001 Nov.
Abstract
The purpose of this study was to determine the effects of oral creatine
supplementation on high intensity, intermittent exercise performance in
competitive squash players. Nine squash players (mean +/- SEM VO2max = 61.9 +/2.1 ml x kg(-1) x min(-1); body mass = 73 +/- 3 kg) performed an on-court
"ghosting" routine that involved 10 sets of 2 repetitions of simulated
positional play, each set interspersed with 30 s passive recovery. A double
blind, crossover design was utilised whereby experimental and control groups
supplemented 4 times daily for 5 d with 0.075 g x kg(-1) body mass of creatine
monohydrate and maltodextrine, respectively, and a 4 wk washout period separated
the crossover of treatments. The experimental group improved mean set sprint
time by 3.2 +/- 0.8% over and above the changes noted for the control group (P =
0.004 and 95% Cl = 1.4 to 5.1%). Sets 2 to 10 were completed in a significantly
shorter time following creatine supplementation compared to the placebo
condition (P < 0.05). In conclusion, these data support existing evidence that
creatine supplementation improves high intensity, intermittent exercise
performance. In addition, the present study provides new evidence that oral
creatine supplementation improves exercise performance in competitive squash
players.
<20>
Unique Identifier
12669262
Authors
Van Schuylenbergh R. Van Leemputte M. Hespel P.
Institution
Exercise Physiology and Biomechanics Laboratory, Department of Kinesiology,
Faculty of Physical Education and Physiotherapy, Katholieke Universiteit Leuven,
Tervuursevest 101, B-3001 Leuven, Belgium.
Title
Effects of oral creatine-pyruvate supplementation in cycling performance.
Source
International Journal of Sports Medicine. 24(2):144-50, 2003 Feb.
Abstract
A double-blind study was performed to evaluate the effects of oral creatinepyruvate administration on exercise performance in well-trained cyclists.
Endurance and intermittent sprint performance were evaluated before (pretest)
and after (posttest) one week of creatine-pyruvate intake (Cr(pyr), 2 x 3.5 g x
d-1, n = 7) or placebo (PL, n = 7). Subjects first performed a 1-hour time trial
during which the workload could be adjusted at 5-min intervals. Immediately they
did five 10-sec sprints interspersed by 2-min rest intervals. Tests were
performed on an individual race bicycle that was mounted on an ergometer.
Steady-state power production on average was about 235-245 W, which corresponded
to blood lactate concentrations of 4-5 mmol x l -1 and heart rate in the range
of 160-170 beats x min -1. Power outputs as well as blood lactate levels and
heart rates were similar between Cr(pyr) and PL at all times. Total work
performed during the 1-h trial was 872 +/- 44 KJ in PL versus 891 +/- 51 KJ in
CR pyr. During the intermittent sprint test power peaked at about 800-1000 watt
within 2-3 sec, decreasing by 15-20 % towards the end of each sprint. Peak and
mean power outputs were similar between groups at all times. Peak lactate
concentrations after the final sprint were approximately 11 mmol x l -1 in both
groups during both the pretest and the posttest. It is concluded that one week
of creatine-pyruvate supplementation at a rate of 7 g x d -1 does not
beneficially impact on either endurance capacity or intermittent sprint
performance in cyclists.
<21>
Unique Identifier
10683103
Authors
Rawson ES. Clarkson PM.
Institution
Department of Exercise Science, University of Massachusetts, Amherst 01003,
USA. erawson@excsci.umass.edu
Title
Acute creatine supplementation in older men.
Source
International Journal of Sports Medicine. 21(1):71-5, 2000 Jan.
Abstract
The hypothesis of this study was that short term creatine (Cr) ingestion in
older individuals would increase body mass and exercise performance, as has been
shown in younger subjects. Seventeen males 60-78 years old were randomly placed
into two groups, Cr and placebo (P), and supplemented in double-blind fashion
for 5 days. Subjects ingested either 5 g of Cr plus 1 g of sucrose 4x per day or
6 g of a sucrose placebo 4x per day. Isometric strength of the elbow flexors was
assessed using a modified preacher bench attached to a strain gauge. Isokinetic
exercise performance was assessed using an intermittent fatigue test of the knee
extensors. Subjects performed 3 sets of 30 repetitions with 60 sec rest between
sets. There was a small (0.5 kg) but statistically significant increase in body
mass (p < 0.05) in the Cr group after supplementation. There was a significant
overall interaction between groups in isokinetic performance from pre to post
supplementation (group x time x set, p < 0.05). However, analysis of the groups
separately revealed that the subjects in the Cr group demonstrated a small nonsignificant increase in isokinetic performance while subjects in the P group
demonstrated a small non-significant performance decrement. There was no
significant difference in isometric strength between groups from pre to post
supplementation. These data suggest that acute oral Cr supplementation does not
increase isometric strength and only produces small increases in isokinetic
performance and body mass in men over the age of 60.
<22>
Unique Identifier
10601174
Authors
McKenna MJ. Morton J. Selig SE. Snow RJ.
Institution
Department of Human Movement, Recreation, and Performance, Centre for
Rehabilitation, Exercise, and Sports Science, Victoria University of Technology,
Melbourne, Victoria 8001, Australia. michael.mckenna@vu.edu.au
Title
Creatine supplementation increases muscle total creatine but not maximal
intermittent exercise performance.
Source
Journal of Applied Physiology. 87(6):2244-52, 1999 Dec.
Abstract
This study investigated creatine supplementation (CrS) effects on muscle total
creatine (TCr), creatine phosphate (CrP), and intermittent sprinting performance
by using a design incorporating the time course of the initial increase and
subsequent washout period of muscle TCr. Two groups of seven volunteers ingested
either creatine [Cr; 6 x (5 g Cr-H(2)O + 5 g dextrose)/day)] or a placebo (6 x 5
g dextrose/day) over 5 days. Five 10-s maximal cycle ergometer sprints with rest
intervals of 180, 50, 20, and 20 s and a resting vastus lateralis biopsy were
conducted before and 0, 2, and 4 wk after placebo or CrS. Resting muscle TCr,
CrP, and Cr were unchanged after the placebo but were increased (P < 0.05) at 0
[by 22.9 +/- 4.2, 8.9 +/- 1.9, and 14.0 +/- 3.3 (SE) mmol/kg dry mass,
respectively] and 2 but not 4 wk after CrS. An apparent placebo main effect of
increased peak power and cumulative work was found after placebo and CrS, but no
treatment (CrS) main effect was found on either variable. Thus, despite the rise
and washout of muscle TCr and CrP, maximal intermittent sprinting performance
was unchanged by CrS.
<23>
Unique Identifier
9572815
Authors
Snow RJ. McKenna MJ. Selig SE. Kemp J. Stathis CG. Zhao S.
Institution
Department of Biomedical Sciences, Centre for Rehabilitation, Exercise, and
Sport Science, and Victoria University of Technology, Melbourne 8001, Australia.
Title
Effect of creatine supplementation on sprint exercise performance and muscle
metabolism.
Source
Journal of Applied Physiology. 84(5):1667-73, 1998 May.
Abstract
The aim of the present study was to examine the effect of creatine
supplementation (CrS) on sprint exercise performance and skeletal muscle
anaerobic metabolism during and after sprint exercise. Eight active, untrained
men performed a 20-s maximal sprint on an air-braked cycle ergometer after 5
days of CrS [30 g creatine (Cr) + 30 g dextrose per day] or placebo (30 g
dextrose per day). The trials were separated by 4 wk, and a double-blind
crossover design was used. Muscle and blood samples were obtained at rest,
immediately after exercise, and after 2 min of passive recovery. CrS increased
the muscle total Cr content (9.5 +/- 2.0%, P < 0.05, mean +/- SE); however, 20-s
sprint performance was not improved by CrS. Similarly, the magnitude of the
degradation or accumulation of muscle (e.g., adenine nucleotides,
phosphocreatine, inosine 5'-monophosphate, lactate, and glycogen) and plasma
metabolites (e.g. , lactate, hypoxanthine, and ammonia/ammonium) were also
unaffected by CrS during exercise or recovery. These data demonstrated that CrS
increased muscle total Cr content, but the increase did not induce an improved
sprint exercise performance or alterations in anaerobic muscle metabolism.
<24>
Unique Identifier
12485548
Authors
Dempsey RL. Mazzone MF. Meurer LN.
Institution
Dept of Family Community Medicine, Medical College of Wisconsin, 8701
Watertown Plank Road, Milwaukee, WI 53226, USA. rdempsey@mcw.edu
Title
Does oral creatine supplementation improve strength? A meta-analysis.
Source
Journal of Family Practice. 51(11):945-51, 2002 Nov.
Abstract
OBJECTIVES: Oral creatine is the most widely used nutritional supplement among
athletes. Our purpose was to investigate whether creatine supplementation
increases maximal strength and power in healthy adults. STUDY DESIGN: Metaanalysis of existing literature. DATA SOURCES: We searched MEDLINE (1966-2000)
and the Cochrane Controlled Trials Register (through June 2001) to locate
relevant articles. We reviewed conference proceedings and bibliographies of
identified studies. An expert in the field was contacted for sources of
unpublished data. Randomized or matched placebo controlled trials comparing
creatine supplementation with placebo in healthy adults were considered.
OUTCOMES MEASURED: Presupplementation and postsupplementation change in maximal
weight lifted, cycle ergometry sprint peak power, and isokinetic dynamometer
peak torque were measured. RESULTS: Sixteen studies were identified for
inclusion. The summary difference in maximum weight lifted was 6.85 kg (95%
confidence interval [CI], 5.24-8.47) greater after creatine than placebo for
bench press and 9.76 kg (95% CI, 3.37-16.15) greater for squats; there was no
difference for arm curls. In 7 of 10 studies evaluating maximal weight lifted,
subjects were young men (younger than 36 years) engaged in resistance training.
There was no difference in cycle ergometer or isokinetic dynamometer
performance. CONCLUSIONS: Oral creatine supplementation combined with resistance
training increases maximal weight lifted in young men. There is no evidence for
improved performance in older individuals or women or for other types of
strength and power exercises. Also, the safety of creatine remains unproven.
Therefore, until these issues are addressed, its use cannot be universally
recommended.
<25>
Unique Identifier
12094124
Authors
Oopik V. Paasuke M. Timpmann S. Medijainen L. Ereline J. Gapejeva J.
Institution
Institute of Exercise Biology, University of Tartu, Tartu, Estonia.
vahuro@ut.ee
Title
Effects of creatine supplementation during recovery from rapid body mass
reduction on metabolism and muscle performance capacity in well-trained
wrestlers.
Source
Journal of Sports Medicine & Physical Fitness. 42(3):330-9, 2002 Sep.
Abstract
BACKGROUND: The aim of the study was to test the hypothesis that creatine
supplementation with concomitant carbohydrate ingestion during recovery period
after rapid body mass reduction accelerates the restoration of body mass and
physical performance in well-trained wrestlers. METHODS: A double-blind,
placebo-controlled cross-over study was conducted on five young healthy male
wrestlers, who reduced their body mass by 4.5-5.3% in two series of
investigations separated by one month. During 17 hrs recovery period they
consumed controlled diet supplemented in random order with glucose (GL trial) or
with glucose plus creatine (GL+CR trial). The capacity of the subjects to
perform submaximal and maximal (W(max)) intensity work was measured using 5 min
intermittent intensity test exercise at the Cybex II device before (Test 1) and
after body mass loss (Test 2), also after the recovery (Test 3) on both trials.
RESULTS: There was no effect of treatment on the extent of body mass regain
during 17 hrs recovery. A significant increase (19.2%) in W(max) from Test 2 to
Test 3 was observed in GL+CR trial whereas no change was evident with GL
treatment. A strong correlation (r=0.92) was established between the whole body
creatine retention and the extent of change in W(max) from Test 2 to Test 3.
CONCLUSIONS: The results suggest that creatine supplementation with concomitant
glucose ingestion during 17 hrs recovery from rapid body mass loss does not
accelerate the restoration of body mass but still stimulates the regain of
physical performance in maximal intensity efforts in well-trained wrestlers.
<26>
Unique Identifier
11726268
Authors
Unnithan VB. Veehof SH.
Institution
Vella CA.
Kern M.
Exercise Science, Syracuse University, Syracuse, NY 13244, USA.
Title
Is there a physiologic basis for creatine use in children and adolescents?.
[Review] [30 refs]
Source
Journal of Strength & Conditioning Research. 15(4):524-8, 2001 Nov.
Abstract
The purported ergogenic benefits of creatine for the adult population have
been well documented. In able-bodied children and adolescents, there is a
paucity of data on creatine use and the purported ergogenic effects of creatine.
Only 1 study to date has investigated the ergogenic properties of creatine in
the adolescent population. The purpose of this review was to try to establish a
rationale for creatine use in the child and adolescent population. The limited
literature available in this area did not provide a strong enough rationale from
either a physiologic or performance perspective for creatine supplementation in
these populations. However, significantly more research is required before
definitive conclusions can be made. [References: 30]
<27>
Unique Identifier
9627907
Authors
Williams MH. Branch JD.
Institution
Department of Exercise Science, Physical Education, and Recreation, Old
Dominion University, Norfolk, Virginia 23529-0196, USA.
Title
Creatine supplementation and exercise performance: an update.[see comment].
[Review] [71 refs]
Comments
Comment in: J Am Coll Nutr. 1998 Jun;17(3):205-6; PMID: 9627905
Source
Journal of the American College of Nutrition. 17(3):216-34, 1998 Jun.
Abstract
Creatine, a natural nutrient found in animal foods, is alleged to be an
effective nutritional ergogenic aid to enhance sport or exercise performance.
Research suggests that oral creatine monohydrate supplementation may increase
total muscle creatine [TCr], including both free creatine [FCr] and
phosphocreatine [PCr]. Some, but not all, studies suggest that creatine
supplementation may enhance performance in high-intensity, short-term exercise
tasks that are dependent primarily on PCr (i.e., < 30 seconds), particularly
laboratory tests involving repeated exercise bouts with limited recovery time
between repetitions; additional corroborative research is needed regarding its
ergogenic potential in actual field exercise performance tasks dependent on PCr.
Creatine supplementation has not consistently been shown to enhance performance
in exercise tasks dependent on anaerobic glycolysis, but additional laboratory
and field research is merited. Additionally, creatine supplementation has not
been shown to enhance performance in exercise tasks dependent on aerobic
glycolysis, but additional research is warranted, particularly on the effect of
chronic supplementation as an aid to training for improvement in competitive
performance. Short-term creatine supplementation appears to increase body mass
in males, although the initial increase is most likely water. Chronic creatine
supplementation, in conjunction with physical training involving resistance
exercise, may increase lean body mass. However, confirmatory research data are
needed. Creatine supplementation up to 8 weeks has not been associated with
major health risks, but the safety of more prolonged creatine supplementation
has not been established. Creatine is currently legal and its use by athletes is
not construed as doping. [References: 71]
<28>
Unique Identifier
10609446
Authors
Graham AS. Hatton RC.
Institution
Genentech, Inc., South San Francisco, CA 94080, USA. graham.angie@gene.com
Title
Creatine: a review of efficacy and safety. [Review] [69 refs]
Source
Journal of the American Pharmaceutical Association. 39(6):803-10; quiz 875-7,
1999 Nov-Dec.
Abstract
OBJECTIVE: To provide an overview of the data on the efficacy and safety of
the nutritional supplement creatine. DATA SOURCES: Human studies in English in
MEDLINE, Current Contents, BIOSIS, Science Citation Index, and the popular media
(including a LEXIS-NEXIS search and information from the World Wide Web and lay
media) for 1966 to July 1999 using the search terms creatine, creatine
supplement#, creatine monophosphate, and creatine NOT kinase. DATA SYNTHESIS:
Creatine use is common among professional athletes. Its use has spread to
college athletes, recreational athletes, and even children. Most creatine
supplement regimens include a loading dose of 20 to 30 grams divided in 4 equal
doses for 5 to 7 days, followed by a 2 gram per day maintenance dose. The
increased creatine in the muscle may allow larger stores of phosphocreatine to
build, and provide extra energy in the form of adenosine triphosphate. Despite
the many clinical trials, high-quality research is lacking. Laboratory
investigations of endurance isotonic exercises, strength and endurance during
isotonic exercises, isokinetic torque, isometric force, and ergometer
performance have yielded roughly an equal number of published studies showing a
positive effect or lack of effect. Field studies (i.e., on subjects
participating in sports activities) are less impressive than laboratory studies.
Performance was more often improved for short-duration, high-intensity
activities. Reports have linked creatine to weight gain, cramping, dehydration,
diarrhea, and dizziness. Creatine may decrease renal function, but only two case
reports of this effect have been published. Creatine appears to be well
tolerated in short-term trials. CONCLUSION: While creatine may enhance the
performance of high-intensity, short-duration exercise, it is not useful in
endurance sports. Because commercially marketed creatine products do not meet
the same quality control standards of pharmaceuticals, there is always a concern
of impurities or doses higher or lower than those on the labeling. Consumers
should balance the quality of information supporting the use of creatine with
the known and theoretical risks of using the product, including possible renal
dysfunction. [References: 69]
<29>
Unique Identifier
12394880
Authors
Sandhu RS. Como JJ. Scalea TS. Betts JM.
Institution
R Adams Cowley Shock Trauma Center, University of Maryland Medical System,
Baltimore 21201, USA.
Title
Renal failure and exercise-induced rhabdomyolysis in patients taking
performance-enhancing compounds.
Source
Journal of Trauma-Injury Infection & Critical Care. 53(4):761-3; discussion
763-4, 2002 Oct.
<30>
Unique Identifier
11126833
Authors
Smith J. Dahm DL.
Institution
Department of Physical Medicine and Rehabilitation, Mayo Clinic, 200 First St
SW, Rochester, MN 55905, USA. smith.jay@mayo.edu
Title
Creatine use among a select population of high school athletes.
Source
Mayo Clinic Proceedings. 75(12):1257-63, 2000 Dec.
Abstract
OBJECTIVE: To determine the prevalence, frequency, and patterns of creatine
use among a local population of high school athletes. SUBJECTS AND METHODS: Male
and female high school athletes completed an anonymous questionnaire on creatine
use during the August 1999 preparticipation examinations at a single
institutional sports medicine center. RESULTS: A total of 328 students (182
males and 146 females) aged 14 to 18 years (mean +/- SD 15.2 +/- 1.3 years)
completed the survey (100% response rate), although not all athletes answered
each question. Twenty-seven athletes (8.2% of total group), 1 of whom was
female, reported creatine use. Of these 27 athletes, 14 (52%) were taking
creatine at the time of the survey. The frequency of creatine use among past and
current users was equally distributed among rarely (30%), weekly (35%), and
daily (35%). Creatine users were older than nonusers (mean 16.5 +/- 1.2 vs 15.0
+/- 1.3 years; P < .001). Of creatine users, 21 (78%) were male football
players. Nineteen of 24 respondents (79%) believed creatine improved their
performance. Overall, 78% of users either did not know how much creatine they
were taking (12/22 respondents) or were taking greater than the recommended
doses (5/22 respondents). Minor gastrointestinal side effects or muscle cramps
were reported by 5 (20%) of 25 respondents. Creatine users were more likely than
nonusers to know other creatine users (81% vs 22%; P < .001) and to use other
supplements (67% vs 9%; P < .001). Creatine users obtained creatine information
primarily from friends (74%) and purchased creatine predominantly from health
food stores (86%). CONCLUSIONS: High school male and female athletes as young as
14 years use creatine. Of high school athletes participating in our study, 8.2%
reported creatine use. Relatively minor side effects, diarrhea, cramps, and loss
of appetite, were reported. Creatine users seem to believe that creatine
improves their performance, but they may lack sufficient information to make
informed decisions regarding creatine use. Further larger scale study is
warranted.
<31>
Unique Identifier
10694109
Authors
Mihic S. MacDonald JR. McKenzie S. Tarnopolsky MA.
Institution
Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada.
Title
Acute creatine loading increases fat-free mass, but does not affect blood
pressure, plasma creatinine, or CK activity in men and women.
Source
Medicine & Science in Sports & Exercise. 32(2):291-6, 2000 Feb.
Abstract
Creatine monohydrate (CrM) administration may enhance high intensity exercise
performance and increase body mass, yet few studies have examined for potential
adverse effects, and no studies have directly considered potential gender
differences. PURPOSE: The purpose of this study was to examine the effect of
acute creatine supplementation upon total and lean mass and to determine
potential side effects in both men and women. METHODS: The effect of acute CrM
(20 g x d(-1) x 5 d) administration upon systolic, diastolic, and mean BP,
plasma creatinine, plasma CK activity, and body composition was examined in 15
men and 15 women in a randomized, double-blind experiment. Additionally,
ischemic isometric handgrip strength was measured before and after CrM or
placebo (PL). RESULTS: CrM did not affect blood pressure, plasma creatinine,
estimated creatinine clearance, plasma CK activity, or handgrip strength (P >
0.05). In contrast, CrM significantly increased fat-free mass (FFM) and total
body mass (P < 0.05) as compared with PL, with no changes in body fat. The
observed mass changes were greater for men versus women. CONCLUSIONS: These
findings suggest that acute CrM administration does not affect blood pressure,
renal function, or plasma CK activity, but increases FFM. The effect of CrM upon
FFM may be greater in men as compared with that in women.
<32>
Unique Identifier
10694120
Authors
Rico-Sanz J. Mendez Marco MT.
Institution
Department of Biochemistry and Molecular Biology, Faculty of Sciences,
University Autonoma of Barcelona, Spain. j.rico-sanz@proton.uab.es
Title
Creatine enhances oxygen uptake and performance during alternating intensity
exercise.
Source
Medicine & Science in Sports & Exercise. 32(2):379-85, 2000 Feb.
Abstract
PURPOSE: The main purpose of the present study was to measure the total oxygen
consumed, accumulation of blood metabolites, and performance during alternating
intensity exercise before and after a period of creatine (Cr) loading in welltrained humans. METHODS: Fourteen males were randomly assigned to two groups of
seven males and were tested before and after 5 d of placebo (PL) or Cr
monohydrate (CR) loading (20 g x d(-1)). Oxygen uptake was measured using a
breath-by-breath system during bicycle exercise alternating every 3 min between
bouts at 30%(-30%) and 90% (-90%) of the maximal power output to exhaustion.
Blood samples were also obtained at rest, before the end of each cycling load,
at exhaustion, and 5-min postexercise. RESULTS: The oxygen consumed during 1-90%
(5.08 +/- 0.39 L) and 2-90% (5.32 +/- 0.30 L) was larger after CR (5.67 +/- 0.34
and 5.78 +/- 0.35 L, P < 0.01 and P < 0.05, respectively). Blood ammonia
accumulation at the end of 1-90% (23.1 +/- 6.5 micromol x L(-1)) and 3-30% (64.7
+/- 15.2 micromol x L(-1)) was lower after CR (P < 0.05), whereas plasma uric
acid accumulation was lower at exhaustion (P < 0.05) and 5-min postexercise (P <
0.01). Time to exhaustion increased (P < 0.05) from 29.9 +/- 3.8 to 36.5 +/- 5.7
min after CR, whereas it remained the same after PL. CONCLUSIONS: The results
indicate that Cr feeding increases the capacity of human muscle to perform work
during alternating intensity contraction, possibly as a consequence of increased
aerobic phosphorylation and flux through the creatine kinase system.
<33>
Unique Identifier
10613426
Authors
Kamber M. Koster M. Kreis R. Walker G. Boesch C. Hoppeler H.
Institution
Institute of Sport Sciences, Swiss Sports School, Magglingen.
Title
Creatine supplementation--part I: performance, clinical chemistry, and muscle
volume.
Source
Medicine & Science in Sports & Exercise. 31(12):1763-9, 1999 Dec.
Abstract
PURPOSE: Our purpose was to study the effects and side effects of creatine
(Cr) supplementation on high-intensity, short-term muscle work, on biochemical
parameters related to Cr metabolism in blood and urine, and on muscle volume of
the lower limb muscles. METHODS: A cycling ergometer was used in a double-blind,
cross-over study on 10 well-trained male physical education students to measure
physical performance with 10 repetitive ergometer sprints (6-s duration, 30-s
rest) before and after supplementation (5 d, 20 g x d(-1), washout period 61 +/8 d, mean +/- SEM, minimum 28 d) with Cr or placebo. Before and after
supplementation, blood and urine were taken and the muscle volume of the lower
limb was determined by magnetic resonance imaging (MRI). RESULTS: A significant
(P << 0.05) increase in performance (+7%) at the end [4-6 s] of the later
sprints (4-7 and 8-10) was observed combined with a lower production of blood
lactate (-1 mmol x L(-1)) with Cr supplementation. The concentration of Cr was
increased significantly in urine (P < 0.001) and serum (P = 0.005), whereas
creatinine (Crn) was increased in serum (P < 0.001). Crn in urine and Crn
clearance did not change significantly with Cr intake. There were no significant
changes in the analyzed blood enzyme activities. A significant gain of body
weight (pre-Cr 76.5 +/- 1.7 kg to 77.9 +/- 1.7 kg post-Cr) with Cr
supplementation was measured, but no accompanying increase of muscle mass in a
limited volume of the lower limb was observed by MRI. CONCLUSION: Cr
supplementation is effective in improving short-term performance, and the
methods used show no detrimental side effects with this supplementation
protocol.
<34>
Unique Identifier
10694141
Authors
Mujika I. Padilla S. Ibanez J. Izquierdo M. Gorostiaga E.
Institution
Departamento de Investigacion y Desarrollo, Servicios Medicos, Athletic Club
de Bilbao, Basque Country, Spain. imujika@grn.es
Title
Creatine supplementation and sprint performance in soccer players.
Source
Medicine & Science in Sports & Exercise. 32(2):518-25, 2000 Feb.
Abstract
PURPOSE: This investigation examined the effects of creatine (Cr)
supplementation on intermittent high-intensity exercise activities specific to
competitive soccer. METHODS: On two occasions 7 d apart, 17 highly trained male
soccer players performed a counter-movement jump test (CMJT), a repeated sprint
test (RST) consisting of six maximal 15-m runs with a 30-s recovery, an
intermittent endurance test (IET) consisting of forty 15-s bouts of highintensity running interspersed by 10-s bouts of low-intensity running, and a
recovery CMJT consisting of three jumps. After the initial testing session,
players were evenly and randomly included in a CREATINE (5 g of Cr, four times
per day for 6 d) or a PLACEBO group (same dosage of maltodextrins) using a
double-blind research design. RESULTS: The CREATINE group's average 5-m and 15-m
times during the RST were consistently faster after the intervention (0.95 +/0.03 vs 0.97 +/- 0.02 s, P < 0.05 and 2.29 +/- 0.08 vs 2.32 +/- 0.07 s, P =
0.07, respectively). Neither group showed significant changes in the CMJT or the
IET. The CREATINE group's recovery CMJT performance relative to the resting CMJT
remained unchanged postsupplementation, whereas it tended to decrease in the
PLACEBO group. CONCLUSION: In conclusion, acute Cr supplementation favorably
affected repeated sprint performance and limited the decay in jumping ability
after the IET in highly trained soccer players. Intermittent endurance
performance was not affected by Cr.
<35>
Unique Identifier
10449017
Authors
Volek JS. Duncan ND. Mazzetti SA. Staron RS. Putukian M. Gomez AL.
Pearson DR. Fink WJ. Kraemer WJ.
Institution
Department of Kinesiology/Center for Sports Medicine, The Pennsylvania State
University, University Park 16802, USA.
Title
Performance and muscle fiber adaptations to creatine supplementation and heavy
resistance training.
Source
Medicine & Science in Sports & Exercise. 31(8):1147-56, 1999 Aug.
Abstract
PURPOSE: The purpose of this study was to examine the effect of creatine
supplementation in conjunction with resistance training on physiological
adaptations including muscle fiber hypertrophy and muscle creatine accumulation.
METHODS: Nineteen healthy resistance-trained men were matched and then randomly
assigned in a double-blind fashion to either a creatine (N = 10) or placebo (N =
9) group. Periodized heavy resistance training was performed for 12 wk. Creatine
or placebo capsules were consumed (25 g x d(-1)) for 1 wk followed by a
maintenance dose (5 g x d(-1)) for the remainder of the training. RESULTS: After
12 wk, significant (P < or = 0.05) increases in body mass and fat-free mass were
greater in creatine (6.3% and 6.3%, respectively) than placebo (3.6% and 3.1%,
respectively) subjects. After 12 wk, increases in bench press and squat were
greater in creatine (24% and 32%, respectively) than placebo (16% and 24%,
respectively) subjects. Compared with placebo subjects, creatine subjects
demonstrated significantly greater increases in Type I (35% vs 11%), IIA (36% vs
15%), and IIAB (35% vs 6%) muscle fiber cross-sectional areas. Muscle total
creatine concentrations were unchanged in placebo subjects. Muscle creatine was
significantly elevated after 1 wk in creatine subjects (22%), and values
remained significantly greater than placebo subjects after 12 wk. Average volume
lifted in the bench press during training was significantly greater in creatine
subjects during weeks 5-8. No negative side effects to the supplementation were
reported. CONCLUSION: Creatine supplementation enhanced fat-free mass, physical
performance, and muscle morphology in response to heavy resistance training,
presumably mediated via higher quality training sessions.
<36>
Unique Identifier
9475647
Authors
Kreider RB. Ferreira M. Wilson M. Grindstaff P. Plisk S. Reinardy J.
Cantler E. Almada AL.
Institution
Department of Human Movement Sciences & Education, The University of Memphis,
TN 38152, USA. kreider.richard@coe.memphis.edu
Title
Effects of creatine supplementation on body composition, strength, and sprint
performance.
Source
Medicine & Science in Sports & Exercise. 30(1):73-82, 1998 Jan.
Abstract
PURPOSE: To determine the effects of 28 d of creatine supplementation during
training on body composition, strength, sprint performance, and hematological
profiles. METHODS: In a double-blind and randomized manner, 25 NCAA division IA
football players were matched-paired and assigned to supplement their diet for
28 d during resistance/agility training (8 h x wk[-1]) with a Phosphagen HP
(Experimental and Applied Sciences, Golden, CO) placebo (P) containing 99 g x
d(-1) of glucose, 3 g x d(-1) of taurine, 1.1 g x d(-1) of disodium phosphate,
and 1.2 g x d(-1) of potassium phosphate (P) or Phosphagen HP containing the P
with 15.75 g x d(-1) of HPCE pure creatine monohydrate (HP). Before and after
supplementation, fasting blood samples were obtained; total body weight, total
body water, and body composition were determined; subjects performed a maximal
repetition test on the isotonic bench press, squat, and power clean; and
subjects performed a cycle ergometer sprint test (12 x 6-s sprints with 30-s
rest recovery). RESULTS: Hematological parameters remained within normal
clinical limits for active individuals with no side effects reported. Total body
weight significantly increased (P < 0.05) in the HP group (P 0.85 +/- 2.2; HP
2.42 +/- 1.4 kg) while no differences were observed in the percentage of total
body water. DEXA scanned body mass (P 0.77 +/- 1.8; HP 2.22 +/- 1.5 kg) and
fat/bone-free mass (P 1.33 +/- 1.1; HP 2.43 +/- 1.4 kg) were significantly
increased in the HP group. Gains in bench press lifting volume (P -5 +/- 134; HP
225 +/- 246 kg), the sum of bench press, squat, and power clean lifting volume
(P 1,105 +/- 429; HP 1,558 +/- 645 kg), and total work performed during the
first five 6-s sprints was significantly greater in the HP group. CONCLUSION:
The addition of creatine to the glucose/taurine/electrolyte supplement promoted
greater gains in fat/bone-free mass, isotonic lifting volume, and sprint
performance during intense resistance/agility training.
<37>
Unique Identifier
10731017
Authors
Terjung RL. Clarkson P. Eichner ER. Greenhaff PL. Hespel PJ. Israel RG.
Kraemer WJ. Meyer RA. Spriet LL. Tarnopolsky MA. Wagenmakers AJ. Williams
MH.
Institution
Biomedical Sciences, College of Veterinary Medicine, University of Missouri,
Columbia 65211, USA. TerjungR@missouri.edu
Title
American College of Sports Medicine roundtable. The physiological and health
effects of oral creatine supplementation.
Source
Medicine & Science in Sports & Exercise. 32(3):706-17, 2000 Mar.
Abstract
Creatine (Cr) supplementation has become a common practice among professional,
elite, collegiate, amateur, and recreational athletes with the expectation of
enhancing exercise performance. Research indicates that Cr supplementation can
increase muscle phosphocreatine (PCr) content, but not in all individuals. A
high dose of 20 g x d(-1) that is common to many research studies is not
necessary, as 3 g x d(-1) will achieve the same increase in PCr given time.
Coincident ingestion of carbohydrate with Cr may increase muscle uptake;
however, the procedure requires a large amount of carbohydrate. Exercise
performance involving short periods of extremely powerful activity can be
enhanced, especially during repeated bouts of activity. This is in keeping with
the theoretical importance of an elevated PCr content in skeletal muscle. Cr
supplementation does not increase maximal isometric strength, the rate of
maximal force production, nor aerobic exercise performance. Most of the evidence
has been obtained from healthy young adult male subjects with mixed athletic
ability and training status. Less research information is available related to
the alterations due to age and gender. Cr supplementation leads to weight gain
within the first few days, likely due to water retention related to Cr uptake in
the muscle. Cr supplementation is associated with an enhanced accrual of
strength in strength-training programs, a response not independent from the
initial weight gain, but may be related to a greater volume and intensity of
training that can be achieved. There is no definitive evidence that Cr
supplementation causes gastrointestinal, renal, and/or muscle cramping
complications. The potential acute effects of high-dose Cr supplementation on
body fluid balance has not been fully investigated, and ingestion of Cr before
or during exercise is not recommended. There is evidence that medical use of Cr
supplementation is warranted in certain patients (e.g.. neuromuscular disease);
future research may establish its potential usefulness in other medical
applications. Although Cr supplementation exhibits small but significant
physiological and performance changes, the increases in performance are realized
during very specific exercise conditions. This suggests that the apparent high
expectations for performance enhancement, evident by the extensive use of Cr
supplementation, are inordinate.
<38>
Unique Identifier
10795791
Authors
Gilliam JD. Hohzorn C. Martin D. Trimble MH.
Institution
Department of Physical Therapy, University of Florida, Gainesville 32610, USA.
gilliam@ufl.edu
Title
Effect of oral creatine supplementation on isokinetic torque production.
Source
Medicine & Science in Sports & Exercise. 32(5):993-6, 2000 May.
Abstract
PURPOSE: This study was conducted to examine the effect of oral creatine
supplementation on the decline in peak isokinetic torque of the quadriceps
muscle group during an endurance test. METHODS: Twenty-three active, but
untrained, male subjects performed isokinetic strength tests on a Cybex II
dynamometer at 180 degrees x s(-1). The protocol consisted of pre- and posttests with five sets of 30 maximum volitional contractions with a 1-min rest
period between sets. Subjects returned to perform the posttest after 5 d of
placebo (4 x 6 g glucose x d(-1), N = 12) or creatine (4 x 5 g creatine + 1 g
glucose x d(-1), N = 11) supplementation. Supplements and testing were
administered in a double blind fashion. Peak torque was measured during each
contraction and the 30 contractions were averaged for each set. RESULTS: A
three-way mixed ANOVA with one between factor (placebo vs creatine) and two
within factors (pre/post supplementation and sets 1-5) revealed no significant
interactions, P > 0.05. The placebo vs creatine main effect was also
nonsignificant, whereas the pre/post and set effects were significant (P <
0.05). Peak torque increased (approximately 3%) from pre- to post-testing, (P =
0.04), but the absolute magnitude of the differences is unlikely to be of any
practical significance. Peak torque decreased from sets 1 to 4, whereas sets 4
and 5 were not different. A priori contrasts comparing the creatine group's
performance pre vs post test for the fourth and fifth sets were nonsignificant
(P > 0.05). CONCLUSIONS: Based on within and between group comparisons, we were
unable to detect an ergogenic effect of oral creatine supplementation on the
decline in peak torque during isokinetic exercise at 180 degrees x s(-1).
<39>
Unique Identifier
11194113
Authors
Rockwell JA. Rankin JW. Toderico B.
Institution
Department of Human Nutrition, Foods, and Exercise, Virginia Tech, Blacksburg
24061-0430, USA.
Title
Creatine supplementation affects muscle creatine during energy restriction.
Source
Medicine & Science in Sports & Exercise. 33(1):61-8, 2001 Jan.
Abstract
INTRODUCTION: Anaerobic performance and body protein may decrease with energy
restriction practiced by some athletes for weight loss. METHODS: This
investigation examined the effects of creatine (Cr) supplementation during
energy restriction on muscle Cr, exercise performance (10 sprints of 6 s, with
30-s rest), nitrogen balance, and body composition in male resistance trainers.
Creatine supplemented (CrS, 20 g x d(-1) of Cr) and those given a placebo (P1)
consumed a formula diet of 75.3 kJ (18 kcal) x kg(-1) x d(-1) (54.7% C, 21.3% P,
24% F) for 4 d. A control group was unsupplemented and continued their normal
diet. There were no changes in body composition or performance of the control
group. RESULTS: CrS and P1 demonstrated similar decreases in body weight and
percent body fat. The percent change in fat-free mass was more for P1 (2.4+/0.3% reduction) than CrS (1.4+/-0.4%), but urinary nitrogen losses were similar.
Significant increases in muscle total Cr and CrP of 15-16% were demonstrated by
CrS over the energy restriction period, whereas P1 had no changes in muscle Cr.
Total work done during the sprints expressed per body weight tended to be 3.8%
higher in CrS and 0.5% less in P1 after the energy restriction (P = 0.058).
CONCLUSION: It was concluded that Cr supplementation increased muscle Cr during
short-term energy restriction but did not affect body fat or protein loss. The
change in muscle creatine was reflected in a tendency for higher total sprint
work for the Cr group.
<40>
Unique Identifier
11323554
Authors
Preen D. Dawson B. Goodman C. Lawrence S. Beilby J. Ching S.
Institution
Department of Human Movement and Exercise Science, The University of Western
Australia, Crawley, W.A., 6009, Australia. dpreen@mbox.com.au
Title
Effect of creatine loading on long-term sprint exercise performance and
metabolism.
Source
Medicine & Science in Sports & Exercise. 33(5):814-21, 2001 May.
Abstract
PURPOSE: This study examined whether creatine (Cr) supplementation could
enhance long-term repeated-sprint exercise performance of approximately 80 min
in duration. METHODS: Fourteen active, but not well-trained, male subjects
initially performed 10 sets of either 5 or 6 x 6 s maximal bike sprints, with
varying recoveries (24, 54, or 84 s between sprints) over a period of 80 min.
Work done (kJ) and peak power (W) were recorded for each sprint, and venous
blood was collected preexercise and on four occasions during the exercise
challenge. Muscle biopsies (vastus lateralis) were obtained preexercise as well
as 0 min and 3 min postexercise. Subjects were then administered either 20 g.d-1
Cr.H2O (N = 7) or placebo (N = 7) for 5 d. Urine samples were collected for each
24 h of the supplementation period. Subjects were then retested using the same
procedures as in test 1. RESULTS: Total work done increased significantly (P <
0.05) from 251.7 +/- 18.4 kJ presupplementation to 266.9 +/- 19.3 kJ (6%
increase) after Cr ingestion. No change was observed for the placebo group
(254.0 +/- 10.4 kJ to 252.3 +/- 9.3 kJ). Work done also improved significantly
(P < 0.05) during 6 x 6 s sets with 54-s and 84-s recoveries and approached
significance (P = 0.052) in 5 x 6 s sets with 24-s recovery in the Cr condition.
Peak power was significantly increased (P < 0.05) in all types of exercise sets
after Cr loading. No differences were observed for any performance variables in
the placebo group. Resting muscle Cr and PCr concentrations were significantly
elevated (P < 0.05) after 5 d of Cr supplementation (Cr: 48.9%; PCr: 12.5%).
Phosphocreatine levels were also significantly higher (P < 0.05) immediately and
3 min after the completion of exercise in the Cr condition. CONCLUSION: The
results of this study indicate that Cr ingestion (20 g.day-1 x 5 d) improved
exercise performance during 80 min of repeated-sprint exercise, possibly due to
an increased TCr store and improved PCr replenishment rate.
<41>
Unique Identifier
11445756
Authors
Volek JS. Mazzetti SA. Farquhar WB. Barnes BR. Gomez AL. Kraemer WJ.
Institution
The Human Performance Laboratory, Ball State University, Muncie, IN 47306,
USA. jvolek@bsu.edu
Title
Physiological responses to short-term exercise in the heat after creatine
loading.
Source
Medicine & Science in Sports & Exercise. 33(7):1101-8, 2001 Jul.
Abstract
PURPOSE: This investigation was designed to examine the influence of creatine
(Cr) supplementation on acute cardiovascular, renal, temperature, and fluidregulatory hormonal responses to exercise for 35 min in the heat. METHODS:
Twenty healthy men were matched and then randomly assigned to consume 0.3 g.kg(1) Cr monohydrate (N = 10) or placebo (N = 10) for 7 d in a double-blind
fashion. Before and after supplementation, both groups cycled for 30 min at 6070% VO2(peak) immediately followed by three 10-s sprints in an environmental
chamber at 37 degrees C and 80% relative humidity. RESULTS: Body mass was
significantly increased (0.75 kg) in Cr subjects. Heart rate, blood pressure,
and sweat rate responses to exercise were not significantly different between
groups. There were no differences in rectal temperature responses in either
group. Sodium, potassium, and creatinine excretion rates obtained from 24-h and
exercise urine collection periods were not significantly altered in either
group. Serum creatinine was elevated in the Cr group but within normal ranges.
There were significant exercise-induced increases in cortisol, aldosterone,
renin, angiotensin I and II, atrial peptide, and arginine vasopressin. The
aldosterone response was slightly greater in the Cr (263%) compared with placebo
(224%) group. Peak power was greater in the Cr group during all three 10-s
sprints after supplementation and unchanged in the placebo group. There were no
reports of adverse symptoms, including muscle cramping during supplementation or
exercise. CONCLUSION: Cr supplementation augments repeated sprint cycle
performance in the heat without altering thermoregulatory responses.
<42>
Unique Identifier
11740297
Authors
Tarnopolsky MA. Parise G. Yardley NJ. Ballantyne CS. Olatinji S. Phillips
SM.
Institution
Department of Medicine (Neurology and Neurological Rehabilitation), Rm. 4U4,
McMaster University Medical Center, 1200 Main Street W., Hamilton, Ontario,
Canada, L8N 3Z5. tarnopol@mcmaster.ca
Title
Creatine-dextrose and protein-dextrose induce similar strength gains during
training.
Source
Medicine & Science in Sports & Exercise. 33(12):2044-52, 2001 Dec.
Abstract
BACKGROUND: Creatine supplementation during resistance exercise training has
been reported to induce greater increases in fat-free mass (FFM), muscle fiber
area, and strength when compared with a placebo. We have recently shown that
timing of nutrient delivery in the postexercise period can have positive effects
on whole body protein turnover (B. D. Roy et al., Med Sci Sports Exerc.
32(8):1412-1418, 2000). PURPOSE: We tested the hypothesis that a postexercise
protein-carbohydrate supplement would result in similar increases in FFM, muscle
fiber area, and strength as compared with creatine monohydrate (CM), during a
supervised 2-month resistance exercise training program in untrained men.
METHODS: Young healthy male subjects were randomized to receive either CM and
glucose (N = 11; CM 10 g + glucose 75 g [CR-CHO] (CELL-Tech)) or protein and
glucose (N = 8; casein 10 g + glucose 75 g [PRO+CHO]), using double-blinded
allocation. Participants performed 8 wk of whole body split-routine straight set
weight training, 1 h.d(-1), 6 d.wk(-1). Measurements, pre- and post-training
were made of fat-free mass (FFM; DEXA), total body mass, muscle fiber area,
isokinetic knee extension strength (45 and 240 degrees.s(-1)), and 1 repetition
maximal (1RM) strength for 16 weight training exercises. RESULTS: Total body
mass increased more for CR-CHO (+4.3 kg, 5.4%) as compared with PRO-CHO (+1.9
kg, 2.4%) (P < 0.05 for interaction) and FFM increased after training (P < 0.01)
but was not significantly different between the groups (CR-CHO = +4.0 kg, 6.4%;
PRO-CHO = +2.6 kg, 4.1%) (P = 0.11 for interaction). Muscle fiber area increased
similarly after training for both groups (approximately 20%; P < 0.05). Training
resulted in an increase in 1RM for each of the 16 activities (range = 14.239.9%) (P < 0.001), isokinetic knee extension torque (P < 0.01), with no
treatment effects upon any of the variables. CONCLUSIONS: We concluded that
postexercise supplementation with PRO-CHO resulted in similar increases in
strength after a resistance exercise training program as compared with CR-CHO.
However, the greater gains in total mass for the CR-CHO group may have
implications for sport-specific performance.
<43>
Unique Identifier
11740307
Authors
Chrusch MJ. Chilibeck PD. Chad KE. Davison KS. Burke DG.
Institution
College of Kinesiology, University of Saskatchewan, 105 Gymnasium Place,
Saskatoon, Saskatchewan, S7N 5C2, Canada.
Title
Creatine supplementation combined with resistance training in older men.
Source
Medicine & Science in Sports & Exercise. 33(12):2111-7, 2001 Dec.
Abstract
PURPOSE: To study the effect of creatine (Cr) supplementation combined with
resistance training on muscular performance and body composition in older men.
METHODS: Thirty men were randomized to receive creatine supplementation (CRE, N
= 16, age = 70.4 +/- 1.6 yr) or placebo (PLA, N = 14, age = 71.1 +/- 1.8 yr),
using a double blind procedure. Cr supplementation consisted of 0.3-g Cr.kg(-1)
body weight for the first 5 d (loading phase) and 0.07-g Cr.kg(-1) body weight
thereafter. Both groups participated in resistance training (36 sessions, 3
times per week, 3 sets of 10 repetitions, 12 exercises). Muscular strength was
assessed by 1-repetition maximum (1-RM) for leg press (LP), knee extension (KE),
and bench press (BP). Muscular endurance was assessed by the maximum number of
repetitions over 3 sets (separated by 1-min rest intervals) at an intensity
corresponding to 70% baseline 1-RM for BP and 80% baseline 1-RM for the KE and
LP. Average power (AP) was assessed using a Biodex isokinetic knee
extension/flexion exercise (3 sets of 10 repetitions at 60 degrees.s(-1)
separated by 1-min rest). Lean tissue (LTM) and fat mass were assessed using
dual energy x-ray absorptiometry. RESULTS: Compared with PLA, the CRE group had
significantly greater increases in LTM (CRE, +3.3 kg; PLA, +1.3 kg), LP 1-RM
(CRE, +50.1 kg; PLA +31.3 kg), KE 1-RM (CRE, +14.9 kg; PLA, +10.7 kg), LP
endurance (CRE, +47 reps; PLA, +32 reps), KE endurance (CRE, +21 reps; PLA +14
reps), and AP (CRE, +26.7 W; PLA, +18 W). Changes in fat mass, fat percentage,
BP 1-RM, and BP endurance were similar between groups. CONCLUSION: Creatine
supplementation, when combined with resistance training, increases lean tissue
mass and improves leg strength, endurance, and average power in men of mean age
70 yr.
<44>
Unique Identifier
11828245
Authors
Izquierdo M. Ibanez J. Gonzalez-Badillo JJ. Gorostiaga EM.
Institution
Centro de Investigacion y Medicina del Deporte, Gobierno de Navarra, Navarra,
Spain. mizquierdo@jet.es
Title
Effects of creatine supplementation on muscle power, endurance, and sprint
performance.
Source
Medicine & Science in Sports & Exercise. 34(2):332-43, 2002 Feb.
Abstract
PURPOSE: To determine the effects of creatine (Cr) supplementation (20 g x d(1) during 5 d) on maximal strength, muscle power production during repetitive
high-power-output exercise bouts (MRPB), repeated running sprints, and endurance
in handball players. METHODS: Nineteen trained male handball players were
randomly assigned in a double-blind fashion to either creatine (N = 9) or
placebo (N = 10) group. Before and after supplementation, subjects performed
one-repetition maximum half-squat (1RM(HS) and bench press (1RM(BP)), 2 sets of
MRPB consisting of one set of 10 continuous repetitions (R10) followed by 1 set
until exhaustion (R(max)), with exactly 2-min rest periods between each set,
during bench-press and half-squat protocols with a resistance equal to 60 and
70% of the subjects' 1RM, respectively. In addition, a countermovement jumping
test (CMJ) interspersed before and after the MRPB half-squat exercise bouts and
a repeated sprint running test and a maximal multistage discontinuous
incremental running test (MDRT) were performed. RESULTS: Cr supplementation
significantly increased body mass (from 79.4 +/- 8 to 80 +/- 8 kg; P < 0.05),
number of repetitions performed to fatigue, and total average power output
values in the R(max) set of MRPB during bench press (21% and 17%, respectively)
and half-squat (33% and 20%, respectively), the 1RM(HS) (11%), as well as the
CMJ values after the MRPB half-squat (5%), and the average running times during
the first 5 m of the six repeated 15-m sprints (3%). No changes were observed in
the strength, running velocity, or body mass measures in the placebo group
during the experimental period. CONCLUSION: Short-term Cr supplementation leads
to significant improvements in lower-body maximal strength, maximal repetitive
upper- and lower-body high-power exercise bouts, and total repetitions performed
to fatigue in the R(max) set of MRPB, as well as enhanced repeated sprint
performance and attenuated decline in jumping ability after MRPB in highly
trained handball players. Cr supplementation did not result in any improvement
in upper-body maximal strength and in endurance running performance.
<45>
Unique Identifier
12131259
Authors
Kilduff LP. Vidakovic P.
Paul L. Pitsiladis YP.
Institution
Cooney G.
Twycross-Lewis R.
Amuna P.
Parker M.
Centre for Exercise Science and Medicine, Institute of Biomedical and Life
Sciences, University of Glasgow, Glasgow, UK.
Title
Effects of creatine on isometric bench-press performance in resistance-trained
humans.
Source
Medicine & Science in Sports & Exercise. 34(7):1176-83, 2002 Jul.
Abstract
PURPOSE: The purpose of this study was to investigate the effects of creatine
(Cr) supplementation on force generation during an isometric bench-press in
resistance-trained men. METHODS: 32 resistance-trained men were matched for peak
isometric force and assigned in double-blind fashion to either a Cr or placebo
group. Subjects performed an isometric bench-press test involving five maximal
isometric contractions before and after 5 d of Cr (20 g.d-1 Cr + 180 g.d-1
dextrose) or placebo (200 g.d-1 dextrose). Body composition was measured before
and after supplementation. Subjects completed 24-h urine collections throughout
the study period; these were subsequently analyzed to provide total Cr and
creatinine excretion. RESULTS: The amount of Cr retained over the
supplementation period was 45 +/- 18 g (mean +/- SD), with an estimated
intramuscular Cr storage of 43 (13-61) mmol x kg(-1) x dry weight muscle (median
[range]). Four subjects in the Cr group were classified as "nonresponders" (< or
=21 mmol x kg(-1) x dry weight muscle increase following Cr supplementation) and
the remaining 17 subjects were classed as "responders" (> or =32 mmol x kg(-1) x
dry weight muscle). For the Cr group, peak force and total force pre- or postsupplementation were not different from placebo. However, when the analysis was
confined to the responders, both the change in peak force [Repetition 2: 59(81)
N vs -26(85) N; Repetition 3: 45(59) N vs -26(64) N) and the change in total
force (Repetition 1: 1471(1274) N vs 209(1517) N; Repetition 2: 1575(1254) N vs
196(1413) N; Repetition 3: 1278(1245) N vs -3(1118) N; Repetition 4: 918(935) N
vs -83(1095) N] post-supplementation were significantly greater compared with
the placebo group (P < 0.01). For the Cr group, estimated Cr uptake was
inversely correlated with training status (r = -0.68, N = 21, P = 0.001). Cr
significantly increased body weight (84.1 +/- 8.6 kg pre- vs 85.3 +/- 8.3 kg
post-supplementation) and fat-free mass (71.8 +/- 6.0 kg pre- vs 72.6 +/- 6.0 kg
post-supplementation), with the magnitude of increase being significantly
greater in the responder group than in the placebo group. CONCLUSION: Five days
of Cr supplementation increased body weight and fat-free body mass in
resistance-trained men who were classified as responders. Peak force and total
force during a repeated maximal isometric bench-press test were also
significantly greater in the responders compared to the placebo group.
<46>
Unique Identifier
11725330
Authors
Bennett T. Bathalon G. Armstrong D 3rd. Martin B. Coll R. Beck R.
Barkdull T. O'Brien K. Deuster PA.
Institution
Department of Military and Emergency Medicine, Uniformed Services University
of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814-4799, USA.
Title
Effect of creatine on performance of militarily relevant tasks and soldier
health.
Source
Military Medicine. 166(11):996-1002, 2001 Nov.
Abstract
PURPOSE: Determine the short-term effects of creatine supplementation on
performance of military tasks, thermoregulation, and health risks. METHODS: Male
military personnel were randomly assigned to a creatine (CR; N = 8) or a placebo
(CON; N = 8) supplementation group. Testing was conducted at baseline, after a
6-day load phase (20 g/d), and after 4 weeks of taking 6 g/d. Measurements
included body composition, liver/kidney function tests, core body temperatures
during a 10-mile march and 5-mile run, and performance on physical tasks.
RESULTS: Serum and urine creatine increased significantly in the CR group. Body
mass and number of pull-ups performed increased significantly in the CR group
but not the CON group by week 4. No significant differences between the CR and
CON groups were found for other performance measures, body composition, core
body temperature, or other biochemical measures. CONCLUSION: Creatine
supplementation increased body mass and pull-up performance but did not cause
acute health problems. Creatine did not increase core temperature compared with
placebo under the environmental conditions of the study, and it is unlikely that
creatine will enhance the overall readiness or performance of soldiers.
<47>
Unique Identifier
12701815
Authors
Kreider RB.
Institution
Exercise and Sport Nutrition Laboratory, Center for Exercise, Nutrition and
Preventive Health Research, Department of Health, Human Performance and
Recreation, Baylor University, Waco, TX 76798-7313, USA.
Richard_Kreider@baylor.edu
Title
Effects of creatine supplementation on performance and training adaptations.
[Review] [66 refs]
Source
Molecular & Cellular Biochemistry. 244(1-2):89-94, 2003 Feb.
Abstract
Creatine has become a popular nutritional supplement among athletes. Recent
research has also suggested that there may be a number of potential therapeutic
uses of creatine. This paper reviews the available research that has examined
the potential ergogenic value of creatine supplementation on exercise
performance and training adaptations. Review of the literature indicates that
over 500 research studies have evaluated the effects of creatine supplementation
on muscle physiology and/or exercise capacity in healthy, trained, and various
diseased populations. Short-term creatine supplementation (e.g. 20 g/day for 5-7
days) has typically been reported to increase total creatine content by 10-30%
and phosphocreatine stores by 10-40%. Of the approximately 300 studies that have
evaluated the potential ergogenic value of creatine supplementation, about 70%
of these studies report statistically significant results while remaining
studies generally report non-significant gains in performance. No study reports
a statistically significant ergolytic effect. For example, short-term creatine
supplementation has been reported to improve maximal power/strength (5-15%),
work performed during sets of maximal effort muscle contractions (5-15%),
single-effort sprint performance (1-5%), and work performed during repetitive
sprint performance (5-15%). Moreover, creatine supplementation during training
has been reported to promote significantly greater gains in strength, fat free
mass, and performance primarily of high intensity exercise tasks. Although not
all studies report significant results, the preponderance of scientific evidence
indicates that creatine supplementation appears to be a generally effective
nutritional ergogenic aid for a variety of exercise tasks in a number of
athletic and clinical populations. [References: 66]
<48>
Unique Identifier
10763500
Authors
Felber S. Skladal D.
Wyss M.
Kremser C.
Koller A.
Sperl W.
Institution
Department of Radiology II and Magnetic Resonance, University of Innsbruck,
Children's Hospital, LKH Salzburg, Austria.
Title
Oral creatine supplementation in Duchenne muscular dystrophy: a clinical and
31P magnetic resonance spectroscopy study.
Source
Neurological Research. 22(2):145-50, 2000 Mar.
Abstract
The decrease in intracellular creatine concentration in Duchenne muscular
dystrophy may contribute to the deterioration of intracellular energy
homeostasis and may thus be one of the factors aggravating muscle weakness and
degeneration. Oral creatine supplementation should have potential in alleviating
the clinical symptoms. To test this hypothesis, creatine was orally administered
over a period of 155 days to a 9-year-old patient with Duchenne muscular
dystrophy. In accordance with previous investigations on normal subjects and
trained athletes, the patient experienced improved muscle performance during
creatine supplementation. Further evidence supporting this hypothesis derived
from plasma creatine kinase and lactate dehydrogenase activities and repeated
31P magnetic resonance spectroscopy of the gastrocnemius muscle. These
preliminary observations indicate a potential role for creatine supplementation
in the symptomatic therapy of patients with muscle disease.
<49>
Unique Identifier
11985944
Authors
Ziegenfuss TN. Rogers M. Lowery L. Mullins N. Mendel R. Antonio J. Lemon
P.
Institution
Human Nutrition Research Laboratory, Kent State University, Kent, Ohio 44242,
USA. tzphd@hotmail.com
Title
Effect of creatine loading on anaerobic performance and skeletal muscle volume
in NCAA Division I athletes.
Source
Nutrition. 18(5):397-402, 2002 May.
Abstract
OBJECTIVE: We measured the effect of 3 d of creatine (Cr) supplementation on
repeated sprint performance and thigh muscle volume in elite power athletes.
METHODS: Ten male (mean +/- standard deviation of body mass and percentage of
fat (81.1 +/- 10.5 kg and 9.8 +/- 3.5) and ten female (58.4 +/- 5.3 kg and 15.0
+/- 3.4) athletes were matched for sex and 10-s cycle sprint scores, paired by
rank, and randomly assigned to the Cr or placebo (P) group. Subjects completed
six maximal 10-s cycle sprints interspersed with 60 s of recovery before and
after 3 d of Cr (0.35 g/kg of fat-free mass) or P (maltodextrin) ingestion.
Before and after supplementation, 10 contiguous transaxial images of both thighs
were obtained with magnetic resonance imaging. RESULTS: Cr supplementation
resulted in statistically significant increases in body mass (0.9 +/- 0.1 kg, P
< 0.03), total work during the first sprint (P < 0.04), and peak power during
sprints 2 to 6 (P < 0.10). As expected, total work and peak power values for
males were greater than those for their female counterparts during the initial
sprint (P < 0.02); however, the reverse was true during the last three sprints
(P < 0.01). Imaging data showed a 6.6% increase in thigh volume in five of six
Cr subjects (P = 0.05). CONCLUSION: These data indicate that 3 d of Cr
supplementation can increase thigh muscle volume and may enhance cycle sprint
performance in elite power athletes; moreover, this effect is greater in females
as sprints are repeated.
<50>
Unique Identifier
10675277
Authors
Benzi G.
Institution
Department of Physiology and Pharmacology, Faculty of Science, University of
Pavia, Pavia, Italy.
Title
Is there a rationale for the use of creatine either as nutritional
supplementation or drug administration in humans participating in a sport?.
[Review] [79 refs]
Source
Pharmacological Research. 41(3):255-64, 2000 Mar.
Abstract
Even though no unambiguous proof for enhanced performance during highintensity exercise has yet been reported, the creatine administration is charged
to improve physical performance and has become a popular practice among subjects
participating in different sports. Appropriate creatine dosage may be also used
as a medicinal product since, in accordance with the Council Directive
65/65/CEE, any substance which may be administered with a view to restoring,
correcting or modifying physiological functions in human beings is considered a
medicinal product. Thus, quality, efficacy and safety must characterize the
substance. In biochemical terms, creatine administration enhances both creatine
and phosphocreatine concentrations, allowing for an increased total creatine
pool in skeletal muscle. In thermodynamics terms, creatine interferes with the
creatine-creatine kinase-phosphocreatine circuit, which is related to the
mitochondrial function as a highly organized system for the energy control of
the subcellular adenylate pool. In pharmacokinetics terms, creatine entry into
skeletal muscle is initially dependent on the extracellular concentration, but
the creatine transport is subsequently down-regulated. In pharmacodynamics
terms, the creatine enhances the possibility to maintain power output during
brief periods of high-intensity exercises. In spite of uncontrolled daily dosage
and long-term administration, no research on creatine safety in humans has been
set up by specific standard protocol of clinical pharmacology and toxicology, as
currently occurs in phase I for the products for human use. More or less
documented side effects induced by creatine are weight gain; influence on
insulin production; feedback inhibition of endogenous creatine synthesis; longterm damages on renal function. A major point that related to the quality of
creatine products is the amount of creatine ingested in relation to the amount
of contaminants present. During the production of creatine from sarcosine and
cyanamide, variable amounts of contaminants (dicyandiamide, dihydrotriazines,
creatinine, ions) are generated and, thus, their tolerable concentrations (ppm)
must be defined by specific toxicological researches. Creatine, as the
nutritional factors, can be used either at supplementary or therapeutic levels
as a function of the dose. Supplementary doses of nutritional factors usually
are of the order of the daily turnover, while therapeutic ones are three or more
times higher. In a subject with a body weight of 70 kg with a total creatine
pool of 120 g, the daily turnover is approximately 2 g. Thus, in healthy
subjects nourished with a fat-rich, carbohydrate-, protein-poor diet and
participating in a daily recreational sport, the oral creatine supplementation
should be on the order of the daily turnover, i.e. less than 2.5-3 g per day,
bringing the gastrointestinal absorption to account. In healthy athletes
submitted daily to high-intensity strength- or sprint-training, the maximal oral
creatine supplementation should be on the order of two times the daily turnover,
i.e. less than 5-6 g per day for less than 2 weeks, and the creatine
supplementation should be taken under appropriate medical supervision. The oral
administration of more than 6 g per day of creatine should be considered as a
therapeutic intervention because the dosage is more than three times higher than
the creatine daily turnover and more than six times higher than the creatine
daily allowance. In this case, creatine administration should be prescribed by
physicians only in the cases of suspected or proven deficiency, or in conditions
of severe stress and/or injury. 2000 Academic Press@p$hr Copyright 2000 Academic
Press. [References: 79]
<51>
Unique Identifier
11092026
Authors
Pecci MA. Lombardo JA.
Institution
Department of Family Medicine, Boston Medical Center, Massachusetts, USA.
Title
Performance-enhancing supplements. [Review] [56 refs]
Source
Physical Medicine & Rehabilitation Clinics of North America. 11(4):949-60,
2000 Nov.
Abstract
Supplements that are marketed as ergogenic aids have achieved widespread use
in the United States. In image-conscious society, these agents are not only
being consumed by athletes, but also by those looking for a quick fix to enhance
their appearance. Many assume that the performance claims made by the
manufacturers are based on actual data, and that these agents must be safe
because they are sold to the general public. Unfortunately, in most cases these
assumptions are false. Creatine has become very popular, particularly among
college and high school athletes. Studies within the last 5 years have shown
that creatine does seem to have certain ergogenic benefits in a laboratory
setting. It is not currently known whether these benefits actually can be
transferred to the playing field. Although creatine has not consistently been
shown to cause any major side effects, there is some question regarding
creatine's effect on the kidneys, particularly with long-term use. Also, the
safety of supplementation in children and adolescents has not been examined at
all; its use in this population should be discouraged until there are more data.
Androstenedione is an agent that has received a large amount of popular press in
the last year, and this has led to an surge in its usage. It is believed to
exert its ergogenic effects through conversion to testosterone. But what limited
data are available suggest that at the recommended dosage, it does not cause any
measurable change in testosterone levels, or provide any ergogenic benefit in
inexperienced weight lifters. Also, it has yet to be determined whether
androstenedione causes any of the side effects often attributed to use of the
illegal anabolic steroids. Its mechanism of action suggests it has the potential
to cause many of these negative effects. Studies are just beginning to appear in
the literature, and certainly more data need to be gathered before
androstenedione supplementation can be recommended for use as an ergogenic aid.
[References: 56]
<52>
Unique Identifier
10461712
Authors
Demant TW. Rhodes EC.
Institution
School of Human Kinetics, University of British Columbia, Vancouver, Canada.
Title
Effects of creatine supplementation on exercise performance. [Review] [60
refs]
Source
Sports Medicine. 28(1):49-60, 1999 Jul.
Abstract
While creatine has been known to man since 1835, when a French scientist
reported finding this constitutent of meat, its presence in athletics as a
performance enhancer is relatively new. Amid claims of increased power and
strength, decreased performance time and increased muscle mass, creatine is
being hailed as a true ergogenic aid. Creatinine is synthesised from the amino
acids glycine, arginine and methionine in the kidneys, liver and pancreas, and
is predominantly found in skeletal muscle, where it exists in 2 forms.
Approximately 40% is in the free creatine form (Crfree), while the remaining 60%
is in the phosphorylated form, creatine phosphate (CP). The daily turnover rate
of approximately 2 g per day is equally met via exogenous intake and endogenous
synthesis. Although creatine concentration (Cr) is greater in fast twitch muscle
fibres, slow twitch fibres have a greater resynthesis capability due to their
increased aerobic capacity. There appears to be no significant difference
between males and females in Cr, and training does not appear to effect Cr. The
4 roles in which creatine is involved during performance are temporal energy
buffering, spatial energy buffering, proton buffering and glycolysis regulation.
Creatine supplementation of 20 g per day for at least 3 days has resulted in
significant increases in total Cr for some individuals but not others,
suggesting that there are 'responders' and 'nonresponders'. These increases in
total concentration among responders is greatest in individuals who have the
lowest initial total Cr, such as vegetarians. Increased concentrations of both
Crfree and CP are believed to aid performance by providing more short term
energy, as well as increase the rate of resynthesis during rest intervals.
Creatine supplementation does not appear to aid endurance and incremental type
exercises, and may even be detrimental. Studies investigating the effects of
creatine supplementation on short term, high intensity exercises have reported
equivocal results, with approximately equal numbers reporting significant and
nonsignificant results. The only side effect associated with creatine
supplementation appears to be a small increase in body mass, which is due to
either water retention or increased protein synthesis. [References: 60]
<53>
Unique Identifier
12427051
Authors
Mesa JL. Ruiz JR. Gonzalez-Gross MM. Gutierrez Sainz A. Castillo Garzon
MJ.
Institution
Department of Physiology, School of Medicine, University of Granada, Granada,
Spain.
Title
Oral creatine supplementation and skeletal muscle metabolism in physical
exercise. [Review] [377 refs]
Source
Sports Medicine. 32(14):903-44, 2002.
Abstract
Creatine is the object of growing interest in the scientific literature. This
is because of the widespread use of creatine by athletes, on the one hand, and
to some promising results regarding its therapeutic potential in neuromuscular
disease on the other. In fact, since the late 1900s, many studies have examined
the effects of creatine supplementation on exercise performance. This article
reviews the literature on creatine supplementation as an ergogenic aid,
including some basic aspects relating to its metabolism, pharmacokinetics and
side effects. The use of creatine supplements to increase muscle creatine
content above approximately 20 mmol/kg dry muscle mass leads to improvements in
high-intensity, intermittent high-intensity and even endurance exercise (mainly
in nonweightbearing endurance activities). An effective supplementation scheme
is a dosage of 20 g/day for 4-6 days, and 5 g/day thereafter. Based on recent
pharmacokinetic data, new regimens of creatine supplementation could be used.
Although there are opinion statements suggesting that creatine supplementation
may be implicated in carcinogenesis, data to prove this effect are lacking, and
indeed, several studies showing anticarcinogenic effects of creatine and its
analogues have been published. There is a shortage of scientific evidence
concerning the adverse effects following creatine supplementation in healthy
individuals even with long-term dosage. Therefore, creatine may be considered as
a widespread, effective and safe ergogenic aid. [References: 377]
<54>
Unique Identifier
10999421
Authors
Poortmans JR. Francaux M.
Institution
Physiological Chemistry, Higher Institute of Physical Education and
Readaptation, Free University of Brussels, Bruxelles, Belgium.
jrpoortm@ulb.ac.be
Title
Adverse effects of creatine supplementation: fact or fiction?. [Review] [113
refs]
Source
Sports Medicine. 30(3):155-70, 2000 Sep.
Abstract
The consumption of oral creatine monohydrate has become increasingly common
among professional and amateur athletes. Despite numerous publications on the
ergogenic effects of this naturally occurring substance, there is little
information on the possible adverse effects of this supplement. The objectives
of this review are to identify the scientific facts and contrast them with
reports in the news media, which have repeatedly emphasised the health risks of
creatine supplementation and do not hesitate to draw broad conclusions from
individual case reports. Exogenous creatine supplements are often consumed by
athletes in amounts of up to 20 g/day for a few days, followed by 1 to 10 g/day
for weeks, months and even years. Usually, consumers do not report any adverse
effects, but body mass increases. There are few reports that creatine
supplementation has protective effects in heart, muscle and neurological
diseases. Gastrointestinal disturbances and muscle cramps have been reported
occasionally in healthy individuals, but the effects are anecdotal. Liver and
kidney dysfunction have also been suggested on the basis of small changes in
markers of organ function and of occasional case reports, but well controlled
studies on the adverse effects of exogenous creatine supplementation are almost
nonexistent. We have investigated liver changes during medium term (4 weeks)
creatine supplementation in young athletes. None showed any evidence of
dysfunction on the basis of serum enzymes and urea production. Short term (5
days), medium term (9 weeks) and long term (up to 5 years) oral creatine
supplementation has been studied in small cohorts of athletes whose kidney
function was monitored by clearance methods and urine protein excretion rate. We
did not find any adverse effects on renal function. The present review is not
intended to reach conclusions on the effect of creatine supplementation on sport
performance, but we believe that there is no evidence for deleterious effects in
healthy individuals. Nevertheless, idiosyncratic effects may occur when large
amounts of an exogenous substance containing an amino group are consumed, with
the consequent increased load on the liver and kidneys. Regular monitoring is
compulsory to avoid any abnormal reactions during oral creatine supplementation.
[References: 113]