Tukaj podajam nekaj izvleckov znanstvenih clankov na temo dodatkov k prehrani, predvsem kreatina. Vecina clankov je bila objavljenih v priznanih svetovnih medicinskih revijah in naceloma niso "usmerjene" s strani proizvajalcev...
Povsod so zraven napisani avtorji in revija, v kateri je bil clanek objavljen.
Kar se pa tiče da je kreatin na doping list v Avstraliji, nisem ravno siguren po virih, ki jih imam v Avstraliji, vendar sem se pozanil na njihovem olimpijskem komiteju!
To bi še rad povedal: edino kar me moti je ker ljudje z malo znanja s področja športne prehrane ali kakršnihkoli dodatkov, vse preveč posplošujejo in pripisujejo takšne pa drugačne učinke! Mislim da če stvar znaš uporabljat, je učinek najboljši, poleg tega pa posledic ni!
No, naj omenim samo še normalno prehrano. Če bi vedeli po kakšnih postopkih predelujejo in pridelujejo hrano, ki jo vi vzemate iz polic živilskih trgovin, bi se tudi zamislili!
Pa še to, nisem gospod, ker sem verjetno mlajši od vas! Upoštevam mnenje vsakogar.
Upam, da bo za koga zanimivo.
1: J Strength Cond Res. 2005 May;19(2):260-4.
Effect of low-dose, short-duration creatine supplementation on anaerobic
exercise performance.
Hoffman JR, Stout JR, Falvo MJ, Kang J, Ratamess NA.
Department of Health and Exercise Science, The College of New Jersey, Ewing, New
Jersey 08628, USA.
Hoffmanj@tcnj.edu
To examine the efficacy of a low-dose, short-duration creatine monohydrate
supplement, 40 physically active men were randomly assigned to either a placebo
or creatine supplementation group (6 g of creatine monohydrate per day). Testing
occurred before and at the end of 6 days of supplementation. During each testing
session, subjects performed three 15-second Wingate anaerobic power tests. No
significant (p > 0.05) group or time differences were observed in body mass,
peak power, mean power, or total work. In addition, no significant (p > 0.05)
differences were observed in peak power, mean power, or total work. However, the
change in the rate of fatigue of total work was significantly (p < 0.05) lower
in the creatine supplementation group than in the placebo group, indicating a
reduced fatigue rate in subjects supplementing with creatine compared with the
placebo. Although the results of this study demonstrated reduced fatigue rates
in patients during high-intensity sprint intervals, further research is
necessary in examining the efficacy of low-dose, short-term creatine
supplementation.
PMID: 15903359 [PubMed - in process]
2: Int J Sport Nutr Exerc Metab. 2004 Aug;14(4):481-92.
Comment in:
Int J Sport Nutr Exerc Metab. 2004 Aug;14(4):493.
Prevalent use of dietary supplements among people who exercise at a commercial
gym.
Morrison LJ, Gizis F, Shorter B.
Nutrition Department of the C.W. Post Campus of Long Island University,
Brookville, NY 11548, USA.
Supplement use was surveyed in a convenience sample of persons who exercised
regularly at a Long Island, NY gym. Participants, age at least 18 y, completed
anonymous questionnaires. A majority (84.7 %) took supplements. Many consumed
multivitamin/minerals (MVM; 45 %), protein shakes/bars (PRO; 42.3 %), vitamin C
(34.7 %), and vitamin E (VE; 23.4 %) at least 5 times per wk. Other dietary
supplements were used less frequently or by fewer participants. Ephedra was
consumed by 28 % at least once per wk. Choices and reasons for dietary
supplement use varied with age of the participant. More of the oldest consumed
MVM or VE, while those 45 y or younger chose PRO. Those younger than 30 consumed
creatine more frequently. The oldest participants took supplements to prevent
future illness, while others took supplements to build muscle. The reason for
committing to an exercise program influenced supplement use. Bodybuilders more
frequently consumed PRO, creatine, and ephedra compared to those exercising for
health reasons.
PMID: 15467105 [PubMed - indexed for MEDLINE]
3: J Nutr. 2004 Oct;134(10 Suppl):2888S-2894S; discussion 2895S.
Potential ergogenic effects of arginine and creatine supplementation.
Paddon-Jones D, Borsheim E, Wolfe RR.
Department of Surgery, The University of Texas Medical Branch and Metabolism
Unit, Shriners Hospitals for Children, Galveston, TX 77550, USA.
The rationale for the use of nutritional supplements to enhance exercise
capacity is based on the assumption that they will confer an ergogenic effect
above and beyond that afforded by regular food ingestion alone. The proposed or
advertised ergogenic effect of many supplements is based on a presumptive
metabolic pathway and may not necessarily translate to quantifiable changes in a
variable as broadly defined as exercise performance. L-arginine is a
conditionally essential amino acid that has received considerable attention due
to potential effects on growth hormone secretion and nitric oxide production. In
some clinical circumstances (e.g., burn injury, sepsis) in which the demand for
arginine cannot be fully met by de novo synthesis and normal dietary intake,
exogenous arginine has been shown to facilitate the maintenance of lean body
mass and functional capacity. However, the evidence that supplemental arginine
may also confer an ergogenic effect in normal healthy individuals is less
compelling. In contrast to arginine, numerous studies have reported that
supplementation with the arginine metabolite creatine facilitates an increase in
anaerobic work capacity and muscle mass when accompanied by resistance training
programs in both normal and patient populations. Whereas improvement in the rate
of phosphocreatine resynthesis is largely responsible for improvements in acute
work capacity, the direct effect of creatine supplementation on skeletal muscle
protein synthesis is less clear. The purpose of this review is to summarize the
role of arginine and its metabolite creatine in the context of a nutrition
supplement for use in conjunction with an exercise stimulus in both healthy and
patient populations.
Publication Types:
Review
Review, Tutorial
PMID: 15465806 [PubMed - indexed for MEDLINE]
4: South Med J. 2004 Sep;97(9):877-9.
Supplements and athletes.
Lombardo JA.
Sports Medicine Center, Ohio State University, 2050 Kenny Road, Columbus, OH
43221, USA.
Supplements have become a staple with athletes. Athletes take supplements to
enhance their performance through replenishment of real and perceived
deficiencies, anabolic action of stimulants, increased energy and alertness, and
for weight control. Physicians who deal with athletes should be aware of the
supplements being utilized by athletes, the athletes' desired effects and the
efficacy of the supplement, the adverse effects, and whether the supplement is
banned by leagues or organizations in which the athletes are competing. For
those athletes who are regularly drug tested for performance enhancers, it is
important to remember that one cannot be 100% sure that any supplement will not
result in a positive drug test, because there is no independent agency
certifying purity.
PMID: 15455977 [PubMed - indexed for MEDLINE]
5: J Nutr Biochem. 2004 Aug;15(8):473-8.
Effects of creatine supplementation on the performance and body composition of
competitive swimmers.
Mendes RR, Pires I, Oliveira A, Tirapegui J.
Department of Food and Experimental Nutrition, Faculty of Pharmaceutical
Sciences, University of Sao Paulo-Av, Lineu Prestes, Sao Paulo, SP, Brazil.
remendes@usp.br
The objective of this study was to determine the effect of creatine
supplementation on performance and body composition of swimmers. Eighteen
swimmers were evaluated in terms of post-performance lactate accumulation, body
composition, creatine and creatinine excretion, and serum creatinine
concentrations before and after creatine or placebo supplementation. No
significant differences were observed in the marks obtained in swimming tests
after supplementation, although lactate concentrations were higher in placebo
group during this period. In the creatine-supplemented group, urinary creatine,
creatinine, and body mass, lean mass and body water were significantly
increased, but no significant difference in muscle or bone mass was observed.
These results suggest that creatine supplementation cannot be considered to be
an ergogenic supplement ensuring improved performance and muscle mass gain in
swimmers.
PMID: 15302082 [PubMed - indexed for MEDLINE]
6: J Herb Pharmacother. 2004;4(1):1-7.
Effects of creatine supplementation on renal function.
Yoshizumi WM, Tsourounis C.
Cedars-Sinai Medical Center, Los Angeles, CA., USA.
Creatine is a popular supplement used by athletes in an effort to increase
muscle performance. The purpose of this review was to assess the literature
evaluating the effects of creatine supplementation on renal function. A PubMed
search was conducted to identify relevant articles using the keywords, creatine,
supplementation, supplements, renal dysfunction, ergogenic aid and renal
function. Twelve pertinent articles and case reports were identified. According
to the existing literature, creatine supplementation appears safe when used by
healthy adults at the recommended loading (20 gm/day for five days) and
maintenance doses (</=3 gm/day). In people with a history of renal disease or
those taking nephrotoxic medications, creatine may be associated with an
increased risk of renal dysfunction. One case report of acute renal failure was
reported in a 20-year-old man taking 20 gm/day of creatine for a period of four
weeks. There are few trials investigating the long-term use of creatine
supplementation in doses exceeding 10 gm/day. Furthermore, the safety of
creatine in children and adolescents has not been established. Since creatine
supplementation may increase creatinine levels, it may act as a false indicator
of renal dysfunction. Future studies should include renal function markers other
than serum creatinine and creatinine clearance.
Publication Types:
Review
Review, Tutorial
PMID: 15273072 [PubMed - indexed for MEDLINE]
7: J Adolesc Health. 2004 Jun;34(6):508-16.
A look at nutritional supplement use in adolescents.
Bell A, Dorsch KD, McCreary DR, Hovey R.
Faculty of Kinesiology and Health Studies, University of Regina, Regina,
Saskatchewan S4S 0A2, Canada.
PURPOSE: To examine the use of nutritional supplements by adolescents.
Supplements examined were those purported to influence performance and body
mass. METHODS: 333 adolescents (190 male, 139 female, 4 nonrespondents) between
the ages of 13 and 19 years, from a midwestern province in Canada, completed a
pencil-and-paper survey. Participants, who were enrolled in health and
wellness/physical education classes, were requested to provide information about
current and potential use of 10 readily available nutritional supplements, as
well as their knowledge of these products as potentially performance enhancing.
Differences in use, potential use, and knowledge, as a function of gender, age,
and level of physical activity were examined using Chi-square analyses and ANOVA
techniques. RESULTS: The most popular dietary aids were multivitamin/mineral
preparations (42.5%). More adolescent males than females reported that they
currently used both creatine and diuretics. Female respondents indicated that
they would consume herbal weight control products significantly more than males.
Older students and students reporting high levels of physical activity were
significantly more likely to be supplementing with creatine and protein. Males
were more likely than females to believe that creatine and androsterone were
performance-enhancing agents. Individuals highly involved in physical activity
tended to believe that multivitamins, creatine, L-carnitine, energizers, and
protein supplements could enhance their performance. CONCLUSIONS: This study
highlights the fact that many nutritional supplements fall within the spectrum
of adolescent use, and that this use may be driven by misguided beliefs in their
performance-enhancing abilities. Groups at particular risk, such as individuals
involved in physical activity to a high degree, are highlighted and the need for
gender-specific information is suggested.
PMID: 15145408 [PubMed - indexed for MEDLINE]
8: Int J Sport Nutr Exerc Metab. 2004 Feb;14(1):104-20.
Erratum in:
Int J Sport Nutr Exerc Metab. 2004 Oct;14(5):following 606.
Nutritional supplement use among college athletes and their sources of
information.
Froiland K, Koszewski W, Hingst J, Kopecky L.
Department of Nutritional Science and Dietetics, University of Nebraska-Lincoln,
Lincoln, NE 68583-0806, USA.
A survey was conducted to examine the source of information and usage of
nutritional supplements in 115 male and 88 female varsity athletes at a Division
I university. The survey asked each athlete to define supplement, and report
supplement use and type, source of information, and reasons for use. Supplement
use frequencies were determined, and comparisons were made between gender and
sport. Eighty-nine percent of the subjects had or were currently using
nutritional supplements. Many athletes did not consider sports drinks and
calorie replacement products as supplements. Females were more likely to take
calcium and multivitamins, and males had significant intake for ginseng, amino
acids, glutamine, hydroxy-methyl-buterate (HMB), weight gainers, whey protein,
and Juven. The most frequently used supplements overall were energy drinks
(73%), calorie replacement products of all types (61.4%), multivitamin (47.3%),
creatine (37.2%), and vitamin C (32.4%). There was also significant supplement
use noted per sport. Females were more likely to obtain information from family
members regarding supplementation, and males from a store nutritionist, fellow
athletes, friends, or a coach. Female athletes were more likely to take
supplements for their health or because of an inadequate diet, while men
reported taking supplements to improve speed and agility, strength and power, or
for weight/muscle gain.
PMID: 15129934 [PubMed - indexed for MEDLINE]
9: Int J Sport Nutr Exerc Metab. 2004 Feb;14(1):95-103.
Creatine supplementation in young soccer players.
Ostojic SM.
Exercise and Sport Nutrition Laboratory, O.C.A. Sports Medicine Institute,
Kikindska 13/11, Pancevo 26000, Yugoslavia.
The purpose of this study was to examine the effects of acute
creatine-monohydrate supplementation on soccer-specific performance in young
soccer players. Twenty young male soccer players (16.6 +/- 1.9 years)
participated in the study and were matched and allocated to 2 randomly assigned
trials: ingesting creatine-monohydrate supplement (3 x 10-g doses) or placebo
for 7 days. Before and after the supplementation protocol, each subject
underwent a series of soccer-specific skill tests: dribble test, sprint-power
test, endurance test, and vertical jump test. Specific dribble test times
improved significantly in the creatine group (13.0 +/- 1.5 vs. 10.2 +/- 1.8 s; p
< .05) after supplementation protocol. Sprint-power test times were
significantly improved after creatine-monohydrate supplementation (2.7 +/- 0.4
vs. 2.2 +/- 0.5 s; p < .05) as well as vertical jump height (49.2 +/- 5.9 vs.
55.1 +/- 6.3 cm; p < .05) in creatine trial. Furthermore, dribble and power test
times, along with vertical jump height, were superior in creatine versus placebo
trial (p < .05) at post-supplementation performance. There were no changes in
specific endurance test results within or between trials (p > .05). There were
no between-trial differences in the placebo trial (p > .05). The main finding of
the present study indicates that supplementation with creatine in young soccer
players improved soccer-specific skill performance compared with ingestion of
placebo.
Publication Types:
Clinical Trial
Randomized Controlled Trial
PMID: 15129933 [PubMed - indexed for MEDLINE]
10: Nutrition. 2004 May;20(5):420-7.
Effect of a 10-week strength training program and recovery drink on body
composition, muscular strength and endurance, and anaerobic power and capacity.
Chromiak JA, Smedley B, Carpenter W, Brown R, Koh YS, Lamberth JG, Joe LA,
Abadie BR, Altorfer G.
Department of Kinesiology, Mississippi State University, Mississippi State,
Mississippi 39762-6186, USA.
jchrom@colled.msstate.edu
OBJECTIVE: We investigated whether postexercise consumption of a supplement
containing whey protein, amino acids, creatine, and carbohydrate combined with a
strength training program promotes greater gains in fat-free mass (FFM), muscle
strength and endurance, and anaerobic performance compared with an isocaloric,
carbohydrate-only control drink combined with strength training. METHODS: The
study was double blind and randomized, and the experimental supplement was
compared with a carbohydrate-only control. Forty-one males (n = 20 in control
group, n = 21 in the supplement group; mean age, 22.2 y) participated in a 4
d/wk, 10-wk periodized strength training program. Subjects had to complete at
least 70% of the workouts. Before and after 10 wk of strength training, subjects
were tested for body composition by using hydrostatic weighing and skinfold
thicknesses, one repetition maximum strength and muscular endurance for the
bench press and 45-degree leg press, and anaerobic performance using a 30-s
Wingate test. Thirty-three subjects (80.5%) completed the training program (n =
15 in control group, n = 18 in the supplement); these 33 subjects also completed
all post-training test procedures. Data were analyzed with two-way analysis of
variance with repeated measures on time. P <== 0.05 was set as statistically
significant. All statistical analyses, including calculation of effect size and
power, were completed with SPSS 11.0. RESULTS: Across groups, FFM increased
during 10 wk of strength training. Although there was no statistically
significant time x group interaction for FFM, there was a trend toward a greater
increase in FFM for the supplement group (+3.4 kg) compared with the control
group (+1.5 kg; P = 0.077). The effect size (eta(2) = 0.100) was moderately
large. Percentage of body fat declined and fat mass was unchanged; there were no
differences between groups. One repetition maximum strength for the bench press
and 45-degree leg press increased, but there were no differences between groups.
Muscular endurance expressed as the number of repetitions completed with 85% of
the one repetition maximum was unchanged; external work, which was estimated as
repetitions completed x resistance used, increased for the 45-degree leg press
but not for the bench press over the 10-wk training period; there were no time x
group interactions for either measurement. Anaerobic power and capacity
improved, but there were no differences between groups for these variables or
for fatigue rate. CONCLUSIONS: Consumption of a recovery drink after strength
training workouts did not promote greater gains in FFM compared with consumption
of a carbohydrate-only drink; however, a trend toward a greater increase in FFM
in the supplement group suggests the need for longer-term studies. Performance
variables such as muscle strength and endurance and anaerobic performance were
not improved when compared with the carbohydrate-only group.
Publication Types:
Clinical Trial
Randomized Controlled Trial
PMID: 15105028 [PubMed - indexed for MEDLINE]
11: Toxicol Lett. 2004 Apr 15;150(1):123-30.
Comment in:
Toxicol Lett. 2004 Sep 25;152(3):273-4.
Toxicol Lett. 2004 Sep 25;152(3):275.
Creatine: are the benefits worth the risk?
Brudnak MA.
Vice President Technology MAK Wood, 1235 Dakota Drive, Units E-F, Grafton, WI
53024, USA.
mbrudnak@wi.rr.com
Creatine monohydrate is a popular sports supplement used to maintain levels of
high-energy phosphates during exercise. As a supplement, varying amounts are
consumed per person corresponding to parameters such as body mass and level of
training (i.e. maintenance versus loading doses). Numerous studies have reported
beneficial effects including increased muscle mass during training and neural
protection. However, negative reports have also been made of possible side
effects, such as muscle cramping during exercise, and potential impurities. The
present paper introduces the positive and negative aspects of creatine
supplementation and focuses on the toxicological data of creatine, its
metabolites and associated mutagenicity or carcinogenicity, genomeceutical
effect(s), and any potential 'contaminants.' Additionally, the novel
applications of creatine to the areas of neurology, cardiology, and diabetes are
presented and discussed along with the representative data for sports nutrition.
Publication Types:
Review
Review, Tutorial
PMID: 15068829 [PubMed - indexed for MEDLINE]
12: J Sports Sci. 2004 Jan;22(1):95-113.
Dietary supplements.
Maughan RJ, King DS, Lea T.
School of Sport and Exercise Sciences, Loughborough University, Loughborough
LE11 3TU, UK.
r.j.maughan@lboro.ac.uk
For the athlete training hard, nutritional supplements are often seen as
promoting adaptations to training, allowing more consistent and intensive
training by promoting recovery between training sessions, reducing interruptions
to training because of illness or injury, and enhancing competitive performance.
Surveys show that the prevalence of supplement use is widespread among sportsmen
and women, but the use of few of these products is supported by a sound research
base and some may even be harmful to the athlete. Special sports foods,
including energy bars and sports drinks, have a real role to play, and some
protein supplements and meal replacements may also be useful in some
circumstances. Where there is a demonstrated deficiency of an essential
nutrient, an increased intake from food or from supplementation may help, but
many athletes ignore the need for caution in supplement use and take supplements
in doses that are not necessary or may even be harmful. Some supplements do
offer the prospect of improved performance; these include creatine, caffeine,
bicarbonate and, perhaps, a very few others. There is no evidence that
prohormones such as androstenedione are effective in enhancing muscle mass or
strength, and these prohormones may result in negative health consequences, as
well as positive drug tests. Contamination of supplements that may cause an
athlete to fail a doping test is widespread.
Publication Types:
Review
PMID: 14971436 [PubMed - indexed for MEDLINE]
13: J Sports Med Phys Fitness. 2003 Dec;43(4):488-92.
Effects of high dose oral creatine supplementation on anaerobic capacity of
elite wrestlers.
Kocak S, Karli U.
Physical Education and Sport Department, Middle East Technical University,
Ankara, Turkey.
settar@metu.edu.tr
AIM: The purpose of this study was to investigate the effect of high dose oral
creatine supplementation on anaerobic capacity of elite wrestlers. METHODS:
Experimental design: comparative randomized design. Setting: Wingate anaerobic
tests of the participants were taken at the Human Performance Laboratory of the
Department of Physical Education and Sports in The Middle East Technical
University, Ankara, Turkey. Participant: 20 active international level wrestlers
participated (22 to 27 years old). Interventions: the daily dosage of creatine
or placebo was divided into 4 equal amounts (5 gx4 = 20 g). Every 5 g of
supplement was dissolved in 250 ml water and it was given to participants 1 hour
before breakfast, lunch, dinner, and workout session. Measures: subjects
underwent a 30-s Wingate Anaerobic tests until exhaustion in pre- and
post-tests. After the pretest measurements were completed, participants were
classified as creatine (Cr., n=10) and placebo (Pl., n=10) groups with regard to
their average anaerobic power scores obtained during the test. RESULTS: Results
of paired "t"-test revealed that there was no significant change in placebo
group between pre- and post-test in average and peak anaerobic power. However,
average and peak power mean scores obtained from post-test (8.123+/-0.448 W/kg
and 10.523 +/-1.004 W/kg) were significantly (p<0.01) higher than pretest
(7.233+/-0.483 W/kg and 8.992+/- 0.665 W/kg) for creatine group. Results of the
independent "t"-test also indicated that the mean gained scores of creatine
group in average and peak power were significantly higher than placebo group
(p<0.01). CONCLUSION: This study demonstrates that short-term high dose oral
creatine supplementation has an ergogenic effect on anaerobic capacity of elite
wrestlers.
Publication Types:
Clinical Trial
Randomized Controlled Trial
PMID: 14767410 [PubMed - indexed for MEDLINE]
14: Eur J Appl Physiol. 2004 May;91(5-6):628-37. Epub 2003 Dec 18.
The effects of creatine supplementation on muscular performance and body
composition responses to short-term resistance training overreaching.
Volek JS, Ratamess NA, Rubin MR, Gomez AL, French DN, McGuigan MM, Scheett TP,
Sharman MJ, Hakkinen K, Kraemer WJ.
Human Performance Laboratory, Department of Kinesiology, University of
Connecticut, Storrs, CT 06269, USA.
jeff.volek@uconn.edu
To determine the effects of creatine supplementation during short-term
resistance training overreaching on performance, body composition, and resting
hormone concentrations, 17 men were randomly assigned to supplement with 0.3
g/kg per day of creatine monohydrate (CrM: n=9) or placebo (P: n=8) while
performing resistance exercise (5 days/week for 4 weeks) followed by a 2-week
taper phase. Maximal squat and bench press and explosive power in the bench
press were reduced during the initial weeks of training in P but not CrM.
Explosive power in the bench press, body mass, and lean body mass (LBM) in the
legs were augmented to a greater extent in CrM ( P<or=0.05) by the end of the
6-week period. A tendency for greater 1-RM squat improvement ( P=0.09) was also
observed in CrM. Total testosterone (TT) and the free androgen index (TT/SHBG)
decreased in CrM and P, reaching a nadir at week 3, whereas sex hormone binding
globulin (SHBG) responded in an opposite direction. Cortisol significantly
increased after week 1 in CrM (+29%), and returned to baseline at week 2.
Insulin was significantly depressed at week 1 (-24%) and drifted back toward
baseline during weeks 2-4. Growth hormone and IGF-I levels were not affected.
Therefore, some measures of muscular performance and body composition are
enhanced to a greater extent following the rebound phase of short-term
resistance training overreaching with creatine supplementation and these changes
are not related to changes in circulating hormone concentrations obtained in the
resting, postabsorptive state. In addition, creatine supplementation appears to
be effective for maintaining muscular performance during the initial phase of
high-volume resistance training overreaching that otherwise results in small
performance decrements.
Publication Types:
Clinical Trial
Randomized Controlled Trial
PMID: 14685870 [PubMed - indexed for MEDLINE]
15: J Strength Cond Res. 2003 Nov;17(4):810-6.
Effects of effervescent creatine, ribose, and glutamine supplementation on
muscular strength, muscular endurance, and body composition.
Falk DJ, Heelan KA, Thyfault JP, Koch AJ.
Department of Exercise and Sport Sciences, College of Health and Human
Performance, University of Florida, Gainesville, Florida 32611, USA.
The purpose of this study was to examine the effects of a combination of
effervescent creatine, ribose, and glutamine on muscular strength (MS), muscular
endurance (ME) and body composition (BC) in resistance-trained men. Subjects
were 28 men (age: 22.3 +/- 1.7 years; weight: 85.8 +/- 12.1 kg; height: 1.8 +/-
0.1 m) who had 2 or more years of resistance-training experience. A double
blind, randomized trial was completed involving supplementation or placebo
control and a progressive resistance-training program for 8 weeks. Dependent
measures were assessed at baseline and after 8 weeks of resistance training.
Both groups significantly improved MS and ME while the supplement group
significantly increased body weight and fat-free mass. Control decreased body
fat and increased fat-free mass. This study demonstrated that the supplement
group did not enhance MS, ME, or BC significantly more than control after an
8-week resistance-training program.
Publication Types:
Clinical Trial
Randomized Controlled Trial
PMID: 14636104 [PubMed - indexed for MEDLINE]
16: J Strength Cond Res. 2003 Nov;17(4):822-31.
Effects of creatine supplementation and resistance training on muscle strength
and weightlifting performance.
Rawson ES, Volek JS.
Department of Exercise Science and Athletics, Bloomsburg University, Bloomsburg,
Pennsylvania 17815, USA.
erawson@bloomu.edu
Creatine monohydrate has become the supplement of choice for many athletes
striving to improve sports performance. Recent data indicate that athletes may
not be using creatine as a sports performance booster per se but instead use
creatine chronically as a training aid to augment intense resistance training
workouts. Although several studies have evaluated the combined effects of
creatine supplementation and resistance training on muscle strength and
weightlifting performance, these data have not been analyzed collectively. The
purpose of this review is to evaluate the effects of creatine supplementation on
muscle strength and weightlifting performance when ingested concomitant with
resistance training. The effects of gender, interindividual variability,
training status, and possible mechanisms of action are discussed. Of the 22
studies reviewed, the average increase in muscle strength (1, 3, or 10
repetition maximum [RM]) following creatine supplementation plus resistance
training was 8% greater than the average increase in muscle strength following
placebo ingestion during resistance training (20 vs. 12%). Similarly, the
average increase in weightlifting performance (maximal repetitions at a given
percent of maximal strength) following creatine supplementation plus resistance
training was 14% greater than the average increase in weightlifting performance
following placebo ingestion during resistance training (26 vs. 12%). The
increase in bench press 1RM ranged from 3 to 45%, and the improvement in
weightlifting performance in the bench press ranged from 16 to 43%. Thus there
is substantial evidence to indicate that creatine supplementation during
resistance training is more effective at increasing muscle strength and
weightlifting performance than resistance training alone, although the response
is highly variable.
Publication Types:
Review
Review, Tutorial
PMID: 14636102 [PubMed - indexed for MEDLINE]
17: Sports Med. 2003;33(12):921-39.
Popular sports supplements and ergogenic aids.
Juhn M.
Department of Family Medicine, University of Washington School of Medicine,
Seattle, Washington, USA.
This article reviews the evidence-based ergogenic potential and adverse effects
of 14 of the most common products in use by recreational and elite athletes
today. Both legal and prohibited products are discussed. This is an aggressively
marketed and controversial area of sports medicine worldwide. It is therefore
prudent for the clinician to be well versed in the more popular supplements and
drugs reputed to be ergogenic in order to distinguish fact from
fiction.Antioxidants, proteins and amino acids are essential components of diet,
but additional oral supplementation does not increase endurance or strength.
Caffeine is ergogenic in certain aerobic activities. Creatine is ergogenic in
repetitive anaerobic cycling sprints but not running or swimming. Ephedrine and
pseudoephedrine may be ergogenic but have detrimental cardiovascular effects.
Erythropoietin is ergogenic but increases the risk of thromboembolic events.
beta-Hydroxy-beta-methylbutyrate has ergogenic potential in untrained
individuals, but studies are needed on trained individuals. Human growth hormone
and insulin growth factor-I decrease body fat and may increase lean muscle mass
when given subcutaneously. Pyruvate is not ergogenic. The androgenic precursors
androstenedione and dehydroepiandrosterone have not been shown to increase any
parameters of strength and have potentially significant adverse effects.
Anabolic steroids increase protein synthesis and muscle mass but with many
adverse effects, some irreversible. Supplement claims on labels of product
content and efficacy can be inaccurate and misleading.
Publication Types:
Review
PMID: 12974658 [PubMed - indexed for MEDLINE]
18: Curr Sports Med Rep. 2002 Apr;1(2):103-6.
Effects of creatine use on the athlete's kidney.
Farquhar WB, Zambraski EJ.
HRCA Research and Training Institute, Harvard Division on Aging, 1200 Centre
Street, Boston, MA 02131, USA.
farquhar@mail.hrca.harvard.edu
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.
Publication Types:
Case Reports
Review
Review, Tutorial
PMID: 12831718 [PubMed - indexed for MEDLINE]
19: Clin Pharmacokinet. 2003;42(6):557-74.
Pharmacokinetics of the dietary supplement creatine.
Persky AM, Brazeau GA, Hochhaus G.
Department of Pharmaceutics, College of Pharmacy, University of Florida,
Gainesville, Florida, USA.
apersky@nc.rr.com
Creatine is a nonessential dietary component that, when supplemented in the
diet, has shown physiological benefits in athletes, in animal-based models of
disease and in patients with various muscle, neurological and neuromuscular
disease. The clinical relevance of creatine supplementation is based primarily
on its role in ATP generation, and cells may be able to better handle rapidly
changing energy demands with supplementation. Although the pharmacological
outcome measures of creatine have been investigated, the behaviour of creatine
in the blood and muscle is still not fully understood. Creatine is most probably
actively absorbed from the gastrointestinal tract in a similar way to amino
acids and peptides. The distribution of creatine throughout the body is largely
determined by the presence of creatine transporters. These transporters not only
serve to distribute creatine but serve as a clearance mechanism because of
creatine 'trapping' by skeletal muscle. Besides the pseudo-irreversible uptake
by skeletal muscle, creatine clearance also depends on renal elimination and
degradation to creatinine. Evidence suggests that creatine pharmacokinetics are
nonlinear with respect to dose size and frequency. Skeletal muscle, the largest
depot of creatine, has a finite capacity to store creatine. As such, when these
stores are saturated, both volume of distribution and clearance can decrease,
thus leading to complex pharmacokinetic situations. Additionally, other dietary
components such as caffeine and carbohydrate can potentially affect
pharmacokinetics by their influence on the creatine transporter. Disease and age
may also affect the pharmacokinetics, but more information is needed. Overall,
there are very limited pharmacokinetic data available for creatine, and further
studies are needed to define absorption characteristics, clearance kinetics and
the effect of multiple doses. Additionally, the relationship between plasma
creatine and muscle creatine needs to be elucidated to optimise administration
regimens.
Publication Types:
Review
Review, Tutorial
PMID: 12793840 [PubMed - indexed for MEDLINE]
20: Health Educ Res. 2003 Feb;18(1):98-107.
Consumption of nutritional supplements among adolescents: usage and perceived
benefits.
O'Dea JA.
School of Development and Learning, Faculty of Education, A35, Education
Building, University of Sydney, NSW 2006, Australia.
j.o'dea@edfac.usyd.edu.au
The aim of the study was to obtain rich qualitative data about the type of
nutritional supplements and drinks consumed by adolescents, and the reasons for
their consumption, with particular emphasis on the perceived benefits of
nutritional supplementation. Semi-structured focus group interviews (n = 16)
were conducted among 78 adolescents aged 11-18 years from a co-educational
government high school. Participants reported consuming sports drinks, vitamin
and mineral supplements, energy drinks, herbal supplements, guarana, creatine,
high protein milk supplements, and coenzyme Q10. Reasons for supplement use
included perceived short-term health benefits, prevention of illness, improved
immunity, parental supply of supplements, taste, energy boost, better sports
performance and to rectify a poor diet. Results suggest that some adolescents
consume nutritional supplements, sports drinks and energy drinks for their
perceived physiological benefits, and that they may not be aware of any
potential risks. Health educators should be aware that adolescents seek specific
health benefits from nutritional supplements and drinks, which may be better
achieved through appropriate consumption of a nutritious diet. Health education
programmes should incorporate the perceptions, aspirations and motivations of
young people into the planning of interventions and activities in order to make
them most relevant and effective.
PMID: 12608687 [PubMed - indexed for MEDLINE]
21: J Fam Pract. 2002 Nov;51(11):945-51.
Does oral creatine supplementation improve strength? A meta-analysis.
Dempsey RL, Mazzone MF, Meurer LN.
Dept of Family Community Medicine, Medical College of Wisconsin, 8701 Watertown
Plank Road, Milwaukee, WI 53226, USA.
rdempsey@mcw.edu
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:
Meta-analysis 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.
Publication Types:
Meta-Analysis
PMID: 12485548 [PubMed - indexed for MEDLINE]
22: J Sports Med Phys Fitness. 2002 Sep;42(3):320-9.
Pre-exercise oral creatine ingestion does not improve prolonged intermittent
sprint exercise in humans.
Preen D, Dawson B, Goodman C, Lawrence S, Beilby J, Ching S.
Department of Human Movement and Exercise Science, The University of Western
Australia, Crawley, WA, Australia.
dpreen@mbox.com.au
BACKGROUND: This investigation determined whether pre-exercise oral Cr ingestion
could enhance prolonged intermittent sprint exercise performance. METHODS:
EXPERIMENTAL DESIGN: a randomised, double-blind crossover design was employed.
SETTING: testing was performed at the Western Australian Institute of Sport and
participants were monitored and treated by both scientific and medical
personnel. PARTICIPANTS: eight active, but not well-trained males with a
background in multiple-sprint based sports acted as subjects for this
investigation. INTERVENTIONS: subjects ingested either 15 g Cr.H2O or placebo
120 min and 60 min prior to the start of an 80-min maximal sprint cycling task
(10 sets of multiple 6-sec sprints with varying active recoveries). Subjects
were retested 14 days later, being required to ingest the alternate supplement
and repeat the exercise test. MEASURES: performance variables (work done and
peak power) were obtained throughout the exercise challenge. Muscle biopsies
(vastus lateralis) were raised to a peak of 2348+/-223 micromol x l(-1) prior to
the commencement of exercise after Cr ingestion. There were no significant
changes in any cycling performance parameters following Cr ingestion, although
blood La- was significantly lower (p<0.05) than placebo at all time points
during were taken preexercise as well as immediately and 3 min post-exercise in
order to determine concentrations of ATP, PCr, Cr, La- and glycogen. Venous
blood was drawn prior to and on four occasions during the exercise test, and
analysed for Cr, NH3+, La- and pH. RESULTS: Serum Cr concentrations exercise,
and plasma NH3+ accumulation was also significantly reduced (p<0.05) in the Cr
condition, but only in the second half of the 80-min exercise test. Muscle ATP
and TCr levels as well as postexercise PCr replenishment were unaffected
following Cr administration. CONCLUSIONS: The data suggest that although the
pre-exercise ingestion of a large Cr dose was shown to have some impact on blood
borne metabolites, it does not improve maximal prolonged intermittent sprint
exercise performance, possibly due to an insufficient time allowed for uptake of
serum Cr by skeletal muscle to occur. Therefore, this form of loading does not
provide an alternative method of Cr supplementation to the traditional five-day
supplementation regimes established by previous research.
Publication Types:
Clinical Trial
Randomized Controlled Trial
PMID: 12094123 [PubMed - indexed for MEDLINE]
23: Proc Nutr Soc. 2002 Feb;61(1):87-96.
The athlete's diet: nutritional goals and dietary strategies.
Maughan R.
University Medical School, Aberdeen, UK.
r.maughan@abdn.ac.uk
When talented, motivated and highly trained athletes meet for competition the
margin between victory and defeat is usually small. When everything else is
equal, nutrition can make the difference between winning and losing. Although
the primary concern of many athletes is to supplement the diet with protein,
vitamins and minerals, and a range of more exotic compounds, key dietary issues
are often neglected. Athletes must establish their nutritional goals, and must
also be able to translate them into dietary strategies that will meet these
goals. Athletes are often concerned with dietary manipulations in the period
around competition, but the main role of nutrition may be to support consistent
intensive training which will lead to improved performance. Meeting energy
demand and maintaining body mass and body fat at appropriate levels are key
goals. An adequate intake of carbohydrate is crucial for maintaining muscle
glycogen stores during hard training, but the types of food and the timing of
intake are also important. Protein ingestion may stimulate muscle protein
synthesis in the post-exercise period, promoting the process of adaptation in
the muscles. Restoration of fluid and electrolyte balance after exercise is
essential. If energy intake is high and a varied diet is consumed,
supplementation of the diet with vitamins and minerals is not warranted, unless
a specific deficiency is identified. Specific strategies before competition may
be necessary, but this requirement depends on the demands of the sport.
Generally, it is important to ensure high pre-competition glycogen stores and to
maintain fluid balance. There is limited evidence to support the use of dietary
supplements, but some, including perhaps creatine and caffeine, may be
beneficial.
Publication Types:
Lectures
PMID: 12002799 [PubMed - indexed for MEDLINE]
24: Med Sci Sports Exerc. 2001 Dec;33(12):2044-52.
Creatine-dextrose and protein-dextrose induce similar strength gains during
training.
Tarnopolsky MA, Parise G, Yardley NJ, Ballantyne CS, Olatinji S, Phillips SM.
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
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 =
14.2-39.9%) (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.
Publication Types:
Clinical Trial
Randomized Controlled Trial
PMID: 11740297 [PubMed - indexed for MEDLINE]
25: J Strength Cond Res. 2001 Feb;15(1):59-62.
The effect of 7 days of creatine supplementation on 24-hour urinary creatine
excretion.
Burke DG, Smith-Palmer T, Holt LE, Head B, Chilibeck PD.
Department of Human Kinetics, St Francis Xavier University, Antigonish, Nova
Scotia, Canada.
Since the discovery that oral ingestion of creatine leads to an increase in
intramuscular creatine, its supplementation has become widespread. However, the
dosage necessary to maximize retention and create significant increases in
intramuscular creatine is poorly understood. In this study, 24-hour urinary
creatine and creatinine levels of 20 university men's football players and 20
university men's hockey players involved in a resistance-exercise program and
supplementing with creatine were collected and analyzed. In a double-blind,
randomized design, 10 football players and 10 hockey players were randomly
assigned to either the supplement or placebo group. Subjects provided a 24-hour
urine sample twice during the study: once prior to supplementation (baseline)
and the second 7 days after daily supplementation and resistance exercise.
Creatine dosage was 0.1 g x kg(-1) lean body mass. The quantity of creatine
ingested was compared with the amount excreted in the urine of those subjects
supplementing with creatine and with placebo. Creatinine levels were compared
between the first and second urine collection and between groups. Creatine and
creatinine concentrations were determined using high-performance liquid
chromatography. In 24-hours, 46% of the ingested creatine was excreted. There
was no change in creatine levels for placebo subjects. Creatinine levels
remained the same within groups at the first and second collection times (p <
0.05). Our findings indicate that when supplementing with dosages of 0.1 g x
kg(-1) lean body mass or between 6 and 8 g at a time, approximately half of the
ingested creatine gets excreted. Because there was no change in urinary
creatinine, it can be assumed that enhanced degradation of creatine did not
occur.
Publication Types:
Clinical Trial
Randomized Controlled Trial
PMID: 11708707 [PubMed - indexed for MEDLINE]
26: Pediatrics. 2001 Aug;108(2):421-5.
Creatine use among young athletes.
Metzl JD, Small E, Levine SR, Gershel JC.
Sports Medicine Service, Hospital for Special Surgery, Department of Pediatrics,
Cornell Medical College, New York, New York 10021, USA.
MetzlJ@HSS.EDU
OBJECTIVE: Creatine is a nutritional supplement that is purported to be a safe
ergogenic aid in adults. Although as many as 28% of collegiate athletes admit
taking creatine, there is little information about creatine use or potential
health risk in children and adolescents. Although the use of creatine is not
recommended in people less than 18 years of age, numerous anecdotal reports
indicate widespread use in young athletes. The purpose of this study was to
determine the frequency, risk factors, and demographics of creatine use among
middle and high school student athletes. METHODS: Before their annual sports
preparticipation physical examinations, middle and high school athletes aged 10
to 18 in Westchester County, a suburb north of New York City, were surveyed in a
confidential manner. Information was collected regarding school grade, gender,
specific sport participation, and creatine use. RESULTS: Overall, 62 of 1103
participants (5.6%) admitted taking creatine. Creatine use was reported in every
grade, from 6 to 12. Forty-four percent of grade 12 athletes surveyed reported
using creatine. Creatine use was significantly more common (P <.001) among boys
(53/604, 8.8%) than girls (9/492, 1.8%). Although creatine was taken by
participants in every sport, use was significantly more common among football
players, wrestlers, hockey players, gymnasts, and lacrosse players (P <.001 for
all). The most common reasons cited for taking creatine were enhanced
performance (74.2% of users) and improved appearance (61.3%), and the most
common reason cited for not taking creatine was safety (45.7% of nonusers).
CONCLUSIONS: Despite current recommendations against use in adolescents less
than 18 years old, creatine is being used by middle and high school athletes at
all grade levels. The prevalence in grades 11 and 12 approaches levels reported
among collegiate athletes. Until the safety of creatine can be established in
adolescents, the use of this product should be discouraged.
PMID: 11483809 [PubMed - indexed for MEDLINE]
27: Pharmacol Rev. 2001 Jun;53(2):161-76.
Clinical pharmacology of the dietary supplement creatine monohydrate.
Persky AM, Brazeau GA.
Department of Pharmaceutics, College of Pharmacy, University of Florida,
Gainesville, Florida 32610, USA.
apersky@ufl.edu
Creatine is a dietary supplement purported to improve exercise performance and
increase fat-free mass. Recent research on creatine has demonstrated positive
therapeutic results in various clinical applications. The purpose of this review
is to focus on the clinical pharmacology and therapeutic application of creatine
supplementation. Creatine is a naturally occurring compound obtained in humans
from endogenous production and consumption through the diet. When supplemented
with exogenous creatine, intramuscular and cerebral stores of creatine and its
phosphorylated form, phosphocreatine, become elevated. The increase of these
stores can offer therapeutic benefits by preventing ATP depletion, stimulating
protein synthesis or reducing protein degradation, and stabilizing biological
membranes. Evidence from the exercise literature has shown athletes benefit from
supplementation by increasing muscular force and power, reducing fatigue in
repeated bout activities, and increasing muscle mass. These benefits have been
applied to disease models of Huntington's, Parkinson's, Duchenne muscular
dystrophy, and applied clinically in patients with gyrate atrophy, various
neuromuscular disorders, McArdle's disease, and congestive heart failure. This
review covers the basics of creatine synthesis and transport, proposed
mechanisms of action, pharmacokinetics of exogenous creatine administration,
creatine use in disease models, side effects associated with use, and issues on
product quality.
Publication Types:
Review
Review, Tutorial
PMID: 11356982 [PubMed - indexed for MEDLINE]
28: Eur J Appl Physiol. 2001 Mar;84(3):238-43.
Effect of creatine supplementation on metabolism and performance in humans
during intermittent sprint cycling.
Finn JP, Ebert TR, Withers RT, Carey MF, Mackay M, Phillips JW, Febbraio MA.
School of Health, Education and Community Services, Northern Territory
University, Darwin, NT 0909, Australia.
paul.finn@ntu.edu.au
This double blind study investigated the effect of oral creatine supplementation
(CrS) on 4 x 20 s of maximal sprinting on an air-braked cycle ergometer. Each
sprint was separated by 20 s of recovery. A group of 16 triathletes [mean age
26.6 (SD 5.1) years. mean body mass 77.0 (SD 5.
kg, mean body fat 12.9 (SD
4.6)%, maximal oxygen uptake 4.86 (SD 0.7) l.min-1] performed an initial 4 x 20
s trial after a muscle biopsy sample had been taken at rest. The subjects were
then matched on their total intramuscular creatine content (TCr) before being
randomly assigned to groups to take by mouth either a creatine supplement (CRE)
or a placebo (CON) before a second 4 x 20 s trial. A muscle biopsy sample was
also taken immediately before this second trial. The CrS of 100 g comprised 4 x
5 g for 5 days. The initial mean TCr were 112.5 (SD 8.7) and 112.5 (SD 10.7)
mmol.kg-1 dry mass for CRE and CON, respectively. After creatine loading and
placebo ingestion respectively, CRE [128.7 (SD 11.
mmol.kg-1 dry mass] had a
greater (P = 0.01) TCr than CON [112.0 (SD 10.0) mmol.kg-1 dry mass]. While the
increase in free creatine for CRE was statistically significant (P = 0.034),
this was not so for the changes in phosphocreatine content [trial 1: 75.7 (SD
6.9), trial 2: 84.7 (SD 11.0) mmol.kg-1 dry mass, P = 0.091]. There were no
significant differences between CRE and CON for citrate synthase activity (P =
0.163). There was a tendency towards improved performance in terms of 1 s peak
power (in watts P = 0.07; in watts per kilogram P = 0.05), 5 s peak power (in
watts P = 0.08) and fatigue index (P = 0.08) after CrS for sprint 1 of the
second trial. However, there was no improvement for mean power (in watts P =
0.15; in watts per kilogram P = 0.1) in sprint 1 or for any performance values
in subsequent sprints. Our results suggest that, while CrS elevates the
intramuscular stores of free creatine, this does not have an ergogenic effect on
4 x 20 s all-out cycle sprints with intervening 20-s rest periods.
Publication Types:
Clinical Trial
Randomized Controlled Trial
PMID: 11320642 [PubMed - indexed for MEDLINE]
29: Sports Med. 2000 Sep;30(3):155-70.
Adverse effects of creatine supplementation: fact or fiction?
Poortmans JR, Francaux M.
Physiological Chemistry, Higher Institute of Physical Education and
Readaptation, Free University of Brussels, Bruxelles, Belgium.
jrpoortm@ulb.ac.be
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.
Publication Types:
Review
Review, Tutorial
PMID: 10999421 [PubMed - indexed for MEDLINE]
30: Br J Sports Med. 2000 Aug;34(4):284-8.
Dietary creatine supplementation does not affect some haematological indices, or
indices of muscle damage and hepatic and renal function.
Robinson TM, Sewell DA, Casey A, Steenge G, Greenhaff PL.
School of Biomedical Sciences, University of Nottingham Medical School, Queen's
Medical Centre, United Kingdom.
BACKGROUND: The use of creatine (Cr) as a nutritional supplement to aid athletic
performance has gained widespread popularity among athletes. However, concerns
have recently been expressed over potentially harmful effects of short and long
term Cr supplementation on health. METHODS: Forty eight young healthy subjects
were randomly allocated to three experimental protocols aimed at elucidating any
potential health risks associated with five days (20 g/day) to nine weeks (3
g/day) of Cr supplementation. Venous blood samples were collected before and
after periods of Cr supplementation and were analysed for some haematological
indices, and for indices of hepatic, muscular, and renal dysfunction. FINDINGS:
All measured indices were well within their respective normal range at all
times. Serum creatinine concentration tended to be increased the day after Cr
supplementation. However, values had returned to baseline six weeks after the
cessation of supplementation. These increases were probably attributable to
increased creatinine production rather than renal dysfunction. No indication of
impairment to the haematological indices measured, hepatic function, or muscle
damage was apparent after Cr supplementation. INTERPRETATION: These data provide
evidence that there are no obvious adverse effects of acute or more chronic Cr
supplementation on the haematological indices measured, nor on hepatic, muscle,
and renal function. Therefore there is no apparent health risk associated with
Cr supplementation to healthy people when it is ingested in quantities that have
been scientifically proven to increase muscle Cr stores.
Publication Types:
Clinical Trial
Randomized Controlled Trial
PMID: 10953902 [PubMed - indexed for MEDLINE]
31: J Am Pharm Assoc (Wash). 1999 Nov-Dec;39(6):803-10; quiz 875-7.
Creatine: a review of efficacy and safety.
Graham AS, Hatton RC.
Genentech, Inc., South San Francisco, CA 94080, USA.
graham.angie@gene.com
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 ergomet
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