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Three Weeks of Creatine Monohydrate Supplementation Affects Dihydrotestosterone to Testosterone Ratio in College-Aged Rugby Players


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This study investigated resting concentrations of selected androgens after 3 weeks of creatine supplementation in male rugby players. It was hypothesized that the ratio of dihydrotestosterone (DHT, a biologically more active androgen) to testosterone (T) would change with creatine supplementation. Double-blind placebo-controlled crossover study with a 6-week washout period. Rugby Institute in South Africa. College-aged rugby players (n = 20) volunteered for the study, which took place during the competitive season. Subjects loaded with creatine (25 g/day creatine with 25 g/day glucose) or placebo (50 g/day glucose) for 7 days followed by 14 days of maintenance (5 g/day creatine with 25 g/day glucose or 30 g/day glucose placebo). Serum T and DHT were measured and ratio calculated at baseline and after 7 days and 21 days of creatine supplementation (or placebo). Body composition measurements were taken at each time point. After 7 days of creatine loading, or a further 14 days of creatine maintenance dose, serum T levels did not change. However, levels of DHT increased by 56% after 7 days of creatine loading and remained 40% above baseline after 14 days maintenance (P < 0.001). The ratio of DHT:T also increased by 36% after 7 days creatine supplementation and remained elevated by 22% after the maintenance dose (P < 0.01). Creatine supplementation may, in part, act through an increased rate of conversion of T to DHT. Further investigation is warranted as a result of the high frequency of individuals using creatine supplementation and the long-term safety of alterations in circulating androgen composition. STATEMENT OF CLINICAL RELEVANCE: Although creatine is a widely used ergogenic aid, the mechanisms of action are incompletely understood, particularly in relation to dihydrotestosterone, and therefore the long-term clinical safety cannot be guaranteed.
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Three Weeks of Creatine Monohydrate Supplementation
Affects Dihydrotestosterone to Testosterone Ratio in
College-Aged Rugby Players
Johann van der Merwe, MBChB, Naomi E. Brooks, PhD, and Kathryn H. Myburgh, PhD
Objective: This study investigated resting concentrations of selected
androgens after 3 weeks of creatine supplementation in male rugby
players. It was hypothesized that the ratio of dihydrotestosterone (DHT,
a biologically more active androgen) to testosterone (T) would change
with creatine supplementation.
Design: Double-blind placebo-controlled crossover study with a
6-week washout period.
Setting: Rugby Institute in South Africa.
Participants: College-aged rugby players (n = 20) volunteered for
the study, which took place during the competitive season.
Interventions: Subjects loaded with creatine (25 g/day creatine
with 25 g/day glucose) or placebo (50 g/day glucose) for 7 days
followed by 14 days of maintenance (5 g/day creatine with 25 g/day
glucose or 30 g/day glucose placebo).
Main Outcome Measures: Serum T and DHT were measured and
ratio calculated at baseline and after 7 days and 21 days of creatine
supplementation (or placebo). Body composition measurements were
taken at each time point.
Results: After 7 days of creatine loading, or a further 14 days of
creatine maintenance dose, serum T levels did not change. However,
levels of DHT increased by 56% after 7 days of creatine loading and
remained 40% above baseline after 14 days maintenance (P,0.001).
The ratio of DHT:T also increased by 36% after 7 days creatine
supplementation and remained elevated by 22% after the maintenance
dose (P,0.01).
Conclusions: Creatine supplementation may, in part, act through an
increased rate of conversion of T to DHT. Further investigation is
warranted as a result of the high frequency of individuals using
creatine supplementation and the long-term safety of alterations in
circulating androgen composition.
Statement of Clinical Relevance: Although creatine is a widely
used ergogenic aid, the mechanisms of action are incompletely
understood, particularly in relation to dihydrotestosterone, and
therefore the long-term clinical safety cannot be guaranteed.
Key Words: creatine supplementation, rugby player, athlete, clinical
safety, DHT:T ratio
(Clin J Sport Med 2009;19:399–404)
Creatine supplementation is a popular ergogenic aid. It
has been extensively researched in various athletic popula-
and diseased populations.
Loading doses of creatine
taken for 5 to 7 days improves some types of exercise
and, in some studies, also increased muscle
strength despite the short duration of supplementation.
Creatine supplementation alone or as part of a multicomponent
putative ergogenic aid may increase muscle mass, particularly
if taken for a longer time period and in conjunction with
increased volume of resistance training.
However, although
creatine is a popular ergogenic and androgenic aid used by
professional and recreational athletes, the mechanisms un-
derlying the enhancement of performance and muscle building
by creatine supplementation remain to be clearly elucidated. In
addition, very few studies have investigated the clinical safety
of creatine supplementation. Most studies investigating possi-
ble side effects have focused on renal function and hepatic
and, although they have not shown any serious side
effects of creatine supplementation, the studies have been of
short duration
and long-term safety is not guaranteed.
Two main approaches have been followed to investigate
mechanisms by which creatine may influence skeletal muscle.
One involves the investigation of skeletal muscle biopsies
and the other main approach involves investigating possible
effects of creatine supplementation on the humoral endocrine
response to exercise. Testosterone can stimulate muscle
growth by increasing protein synthesis and potentially reusing
amino acids from muscle protein breakdown.
growth hormone, and insulin growth factor-1 have been shown
to increase as an acute effect of resistance exercise,
an effect
that was enhanced by 7 days prior ingestion of a supplement
containing creatine (Muscle Fuel: Advocare, Carollton, Texas).
However, a similar study found no enhancement of the
growth hormone response to a 60-minute bout of resistance
training in subjects who had ingested creatine for 5 days, and
the testosterone response to exercise was not significant, with
Submitted for publication February 1, 2009; accepted July 22, 2009.
From the Department of Physiological Sciences, Stellenbosch University,
Stellenbosch, South Africa.
Reprints: Kathryn H. Myburgh, PhD, Department of Physiological Sciences,
Stellenbosch University, Private Bag XI, Matieland 7602, Stellenbosch,
South Africa (e-mail:
Copyright Ó2009 by Lippincott Williams & Wilkins
Clin J Sport Med Volume 19, Number 5, September 2009 |399
or without the creatine supplementation.
In extreme,
overreaching training involving resistance training, it has
even been shown that total testosterone levels decrease after 4
weeks despite creatine supplementation.
These studies sug-
gest that the possible role for testosterone as a mediator of the
observed effects of creatine on muscle mass is controversial.
Testosterone can be converted into a more bioactive
metabolite, dihydrotestosterone (DHT), by 5-alpha reductase.
The role of 5-alpha-reductase in testosterone conversion is
well known in the literature focusing on alopecia
and prostate
even in young males with male pattern baldness.
In addition, biochemical studies of androgen receptor affinity
indicates that DHT is 4 times more biologically potent than T.
Therefore, to further explore this as a potential
mechanism for the effect of creatine supplementation on
muscle, we chose to investigate the ratio of DHT:testosterone
in young male athletes participating in team sports requiring
substantial strength (rugby). Previous studies have mainly
focused on the effects of training combined with creatine
supplementation during the strength improvement phase in
American football players.
We chose to investigate the rugby
players during the competitive season to minimize the
potential compounding effect of changing training at the
same time as providing the supplement.
The study design was a double-blind, placebo-controlled
crossover study with a 6-week washout period. We measured
serum testosterone (T) and DHT and calculated the ratio after
21 days of creatine supplementation. We hypothesized that we
would observe a change in the ratio of DHT:T.
Twenty white males (aged 18–19 years) from a Rugby
Institute situated near Stellenbosch University in South Africa
took part in the study. The study was approved by the
Stellenbosch University Ethics Committee and informed
consent was provided by each subject. None of the subjects
had taken any supplements with their normal diet for 6 weeks
before the study. Subjects were randomized into 2 groups for
a double-blind, placebo-controlled crossover study design with
a 6-week washout period (Figure 1). The randomization was
done as follows: when subjects were handed informed consent
forms, they were assigned a number based on arrival. The even
numbers were assigned to one group and the odd numbers the
other group. There were 4 subjects who dropped out, 2 from
each group. Two subjects left town, 1 subject went overseas
and 1 subject broke a leg. The data from the dropout subjects
were not included in the analysis.
Subjects underwent a 7-day loading period with creatine
supplementation or placebo followed by a 14-day maintenance
dose (creatine or placebo). Creatine monohydrate was given
with glucose (25 g/day creatine and 25 g/day glucose) for
a loading dose and 5 g/day creatine and 25 g/day glucose for
a maintenance dose. The placebo group received glucose only
(50 g/day glucose) for a loading dose and 30 g/day glucose for
a maintenance dose. To maintain the double-blind status, the
FIGURE 1. Flow chart of double-blind
crossover study design of participa-
tion of subjects in the study is shown.
400 | q2009 Lippincott Williams & Wilkins
Merwe et al Clin J Sport Med Volume 19, Number 5, September 2009
supplement and placebo were given as capsules. Both groups
received the same number of capsules during the loading and
maintenance doses.
Training and Dietary Intake
Subjects were part of the Rugby Institute and underwent
standardized training, albeit for different player positions,
during the study. All subjects were residents at the Institute and
the same diet was given to all subjects. During part of the
washout period, all subjects had a short winter break and did
only maintenance training. Therefore, at the beginning of the
second phase of the study, subjects were in similar condition as
the start of the study and not fatigued from consecutive weeks
of match play.
Outcome Measures
Anthropometry measurements were taken on Day 0,
Day 7, and Day 21 in each leg of the study. Six skin fold
measurements were taken (triceps, subscapula, suprailiac,
abdominal, thigh, and midcalf). The average of 2 measure-
ments was calculated and the sum of 6 measurements was used
for calculation of body density and percent body fat.
Blood samples were taken at Day 0, Day 7, and Day 21
with athletes in the fully rested condition pretraining. Samples
were taken from the antecubital vein (SST; Vacutainer, BD,
South Africa), left to clot, and placed on ice. Serum was
separated by centrifuging at 3000 rpm at 4°C and samples
were stored at –70°C. All samples were taken at the same time
of day (4:00 PM to 5:00 PM). Serum was separated and frozen
within 1 hour of collection. Testosterone and DHT were
measured using DSL Testosterone and Dihydrotestosterone
radio immunoassay kits (DSL 4000 and DSL 9600; Diagnostic
Systems Laboratories, Inc, Webster, Texas). Analysis was
conducted according to the radioimmunoassay kit instructions.
Mean values for T levels were calculated and compared with
standards of known quantity representing 0 to 86.75 nmol/L
and compared against control values. Study values fall within
the expected range of 10.06 to 34.35 nmol/L for young adult
males. DHT analysis first included an extraction procedure
to remove T and therefore preventing crossreactivity and
rendering the kit 100% specific to DHT. Mean values of DHT
were calculated and compared with standards ranging from
0 to 8.6 nmol/L and controls ranging from 0.433 to 2.012
nmol/L. The laboratory upper limit for coefficient of variation
for both assays was less than 5% for individual subjects’
samples analyzed in triplicate.
Statistical Analysis
Subjects were assigned a number to maintain confiden-
tiality of results. Subjects were randomized into 2 groups at
baseline and baseline characteristics were compared using
Student unpaired ttest. Data collected over the 2 legs of the
study were pooled so that each subject served as their own
control and analyzed using repeated measures analysis of
variance. Differences at each time interval were analyzed post
hoc by Tukey test with significance set at P,0.01.
Baseline Characteristics and Anthropometry
Subjects were aged 18.7 60.53 years and their height
was 1.81 60.05 m. Body mass ranged from 74.4 to 107 kg.
There were no significant differences in any measurements at
baseline between the subjects randomized to placebo first
compared with those randomized to creatine first. As a result
of the crossover nature of the study design, each subject had 2
baseline time points. Baseline 1 was before any supplemen-
tation or placebo and baseline 2 after the 6-week washout
period. After washout, subjects had a similar baseline for
percent body fat and fat-free mass. Therefore, data are
presented as creatine or placebo with results pooled regardless
of which supplement was taken first. The pooled baseline data
is called Day 0.
Anthropometry measurements did not differ between the
two groups on Day 0 (Table 1), and neither creatine loading or
placebo affected body mass, percentage body fat, or fat-free
mass after 7 days or after 21 days.
Blood Measurements
Testosterone levels did not change significantly over
time in either group (P= 0.19; Table 2). With creatine, no
statistically significant increases in T concentrations were seen
after 7 days or after 21 days, but there was more variation in the
means over time (Table 2). Dihydrotestosterone did not change
with placebo; however, in the creatine group, there were sig-
nificant increases in DHT concentrations over time resulting in
a time 3group interaction (time 3group P,0.00001). After
7 days of loading, the increase in DHT was 56%, and after 14
more days on the maintenance dose, the elevation was still
40% above baseline.
After calculating the ratio of DHT to T, it was found that
there was a significantly higher ratio in the creatine group
(group 3time P,0.00001). This change in ratio amounted to
a 36% increase in conversion of T to DHT after 7 days of
TABLE 1. Body Composition Before Supplementation
(Day 0), After Loading (Day 7), and After Maintenance
Doses (Day 21) of Creatine with Carbohydrate or
Placebo with Carbohydrate
Day 0 Day 7 Day 21
Body mass, kg
Placebo 86.80 69.90 87.30 610.1 87.26 69.96
Creatine 87.04 610.66 87.80 610.88 87.80 610.82
Sum of 6 skin
folds, mm
Placebo 274 658 274 655 272 656
Creatine 272 654 269 649 269 643
Percent body fat
Placebo 13.53 63.95 13.54 63.94 13.47 63.97
Creatine 13.43 63.92 13.36 64.02 13.30 63.95
Fat-free mass, kg
Placebo 75.0 65.7 75.0 65.8 75.0 65.8
Creatine 75.0 66.7 75.8 66.8 75.8 66.5
Values are mean 6standard deviation; n = 20 subjects completing each of the arms
of the crossover design.
q2009 Lippincott Williams & Wilkins |401
Clin J Sport Med Volume 19, Number 5, September 2009 Creatine Supplementation and DHT:T Ratio in Male Rugby Players
creatine supplementation (post hoc test: P,0.001). The
conversion was still elevated by 22% at 21 days after 14 days
on maintenance (post hoc test: P,0.01).
Important features of this study were that all athletes
were in peak competitive condition at baseline and were
involved in the same training and competition structures.
Similar to Ziegenfuss et al,
the current study had a relatively
long washout period of 6 weeks as opposed to more commonly
used 4-week washout.
The main finding that is discussed
subsequently is that this is the first study to report an increase
in the DHT to T ratio in response to creatine loading, a
response that was also maintained during the maintenance
phase for at least another 2 weeks in young trained athletes. In
addition, this study used creatine monohydrate with carbohy-
drate as opposed to a multicomponent supplement so that all
findings can be attributed to creatine only.
Several other studies have investigated the possibility
that changes in androgens may underlie the positive effects of
creatine supplementation on muscle mass with creatine taken
alone or with other components. These studies investigated
mainly the growth hormone and insulin-like growth factor-1
axis or testosterone and sex hormone-binding globulin, or all,
but not DHT.
In 2 studies, increased growth hormone
and T responses were seen immediately after exercise in
supplemented subjects, who were supplemented with creatine
combined with branch-chain amino acids, taurine, caffeine,
and glucouronolactone.
In the first study, the supple-
mented subjects completed a loading dose phase. Although
subjects taking placebo also experienced a postexercise
increase in growth hormone, this increase was significantly
greater in the supplemented group than the control group.
the second study, the same research group found increases in
T and growth hormone after exercise in both groups when
supplementation was acute.
In these studies, the duration of
supplementation was 1 week
or 1 dose,
which raises the
question of whether or not a longer exposure would have
resulted in different results. Indeed, increased levels of T were
found in resting blood samples after 10 weeks of resistance
training with creatine supplementation compared with placebo
and with creatine and beta-alanine supplementation.
to Op’t Eijnde and Hespel, we did not find an effect of sup-
plementation with only creatine on resting testosterone levels
in trained subjects
despite the loading phase of 7 days and
a maintenance phase of another 14 days. Also, no changes in
plasma T were found after 6 weeks of supplementation with
beta-hydroxy beta-methylbutarate or the combination of crea-
tine and hydroxy beta-methylbutarate.
Therefore, our results
agree with these studies as well as Kraemer et al.
the latter study did find a greater T response to a resistance
exercise training bout after a multicomponent supplement
containing 3 g creatine.
On the other hand, Volek et al
even found declines in
resting T despite creatine supplementation in subjects who
were becoming overreached. The players in our study did not
become overreached despite the long duration of the study and
competitive season, because there was a 2-week midseason
break, which coincided with the first 2 weeks of washout. Both
of these studies used creatine monohydrate as a single putative
ergogenic substance. In our study, creatine was taken in con-
junction with carbohydrate to enhance muscle uptake of
creatine but was not taken in combination with any other
putative anabolic supplements such as those that may be
hypothesized to work synergistically.
With no effect on resting T levels, the effect of creatine
supplementation on DHT becomes an even more important
finding. This effect was a large increase in DHT rather than
a marginal (possibly physiologically insignificant) effect.
As mentioned earlier, 5-alpha-reductase converts tes-
tosterone to DHT. There is low
or no
5-alpha-reductase in
muscle or bone suggesting that any potential effect on muscle
is mediated by conversion at other sites. Comparing the
androgen receptor physiology of T and DHT, studies have
indicated that DHT has higher affinity as well as longer recep-
tor occupancy than T, rendering it a more potent androgen.
In the face of T deficiency, DHT alone or DHTand T have been
used to prevent muscle weakness and atrophy.
mechanistic studies do not clearly indicate its effect on muscle
tissue; DHT treatment in orchidectomized rats did not activate
the Akt anabolic signaling pathway involved in muscle
Nevertheless, in tissue culture addition of DHT
to the culture media, stimulate C2C12 cells (a satellite cell
line), proliferated
and promoted the commitment of a
pluripotent cell line to myogenic differentiation.
The second major finding of the current study was
a higher DHT:T ratio after 7 days of creatine loading, which
was maintained with another 2 weeks of maintenance dose.
Clinically, an increased ratio of DHT:T has been linked to
higher male pattern baldness.
Therefore, it is important to
also investigate the effects of this ratio on target tissues.
Litman et al
found racial/ethnical differences in the
ratio of DHT:T. They purported that prostate cancer, body
composition, and bone mass differences between the ethnic/
racial groups may be explained by differences in this ratio. In
this context, it is also pertinent to discuss the physiology of
TABLE 2. Testosterone, Dihydrotestosterone, and
Dihydrotestosterone to Testosterone Ratio Before, After
Loading, and After Maintenance Doses of Creatine with
Carbohydrate or Placebo with Carbohydrate
Day 0 Day 7 Day 21
(T; nmol/L)
Placebo 17.09 63.42 17.02 64.11 17.04 65.25
Creatine 14.44 62.95 16.08 62.86 16.69 64.61
(DHT; nmol/L)
Placebo 1.26 60.52 1.09 60.40 1.06 60.43
Creatine 0.98 60.37 1.53 60.50* 1.38 60.45*
DHT:T ratio
Placebo 0.074 60.027 0.066 60.022 0.064 60.023
Creatine 0.069 60.023 0.096 60.031* 0.086 60.032
Values are mean 6standard deviation; n = 20 subjects completing each of the arms
of the crossover design.
402 | q2009 Lippincott Williams & Wilkins
Merwe et al Clin J Sport Med Volume 19, Number 5, September 2009
DHT and DHT:T ratio without reference to possible ergogenic
mechanisms, but rather focusing on clinical safety. Previous
studies addressing safety issues indicated that creatine
supplementation does not seem to have short-term negative
effects on renal or hepatic function.
Nonetheless, more
comprehensive studies of long-term safety are still required.
The prostate is the best known tissue that is highly responsive
to androgens, including DHT.
DHT may be associated with
benign prostate hypertrophy,
but the association with
prostate cancer remains controversial.
Given this discussion, it would seem that DHT or the
DHT:T ratio may well be possible mechanisms for positive
effects of creatine on muscle mass. The increase in DHT and
DHT:T ratio after 7 days of creatine loading was not seen at
Day 21. There may be a dose–response to the amount of
creatine ingested and the maintenance dose may not be high
enough to maintain the increased ratio. However, in the current
study, we did not see changes in body mass or percent body
fat. Our study recruited rugby players during their competitive
season, after their initial preseason strength orientated training
was completed. On the one hand, this enabled us to determine
the effects of creatine supplementation on already trained
individuals without major additional training changes.
However, this may explain why body composition did not
change. One could speculate that a supplementation period of
longer than 21 days may have altered body composition even
in these subjects whose training did not change appreciably
during the course of the study.
In conclusion, creatine supplementation may act, at least
in part, through the increased rate of conversion of T to DHT.
Because of the potential clinical relevance of the endocrine
results of this study and the high frequency of individuals
using creatine supplementation without monitoring, further
investigation is warranted. Clearly, future studies on the
putative anabolic effects of creatine supplementation should be
more comprehensive in terms of potential humoral and
intramuscular effects.
We thank the rugby players for their cooperation
throughout the duration of the study. We also thank the staff
involved with the rugby players and the Institute for
accommodating the study. Thanks to Mrs. Gail Nell (Chemical
Pathology, Grootte Schuur Hospital), Anneke Le Roux
(Biokineticist, private practice), and Jacolene Kroff, PhD
(Sport Science, Stellenbosch University) for technical support.
1. Bemben MG, Lamont HS. Creatine supplementation and exercise
performance: recent findings. Sports Med. 2005;35:107–125.
2. Tarnopolsky MA. Clinical use of creatine in neuromuscular and
neurometabolic disorders. Subcell Biochem. 2007;46:183–204.
3. Greenhaff PL, Casey A, Short AH, et al. Influence of oral creatine
supplementation of muscle torque during repeated bouts of maximal
voluntary exercise in man. Clin Sci. 1993;84:565–571.
4. Balsom PD, Soderlund K, Sjodin B, et al. Skeletal muscle metabolism
during short duration high-intensity exercise: influence of creatine
supplementation. Acta Physiol Scand. 1995;154:303–310.
5. Vandenberghe K, Van Hecke P, Van Leemputte M, et al. Phosphocreatine
resynthesis is not affected by creatine loading. Med Sci Sports Exerc.
6. Maganaris CN, Maughan RJ. Creatine supplementation enhances
maximum voluntary isometric force and endurance capacity in resistance
trained men. Acta Physiol Scand. 1998;163:279–287.
7. Vandenberghe K, Goris M, Van Hecke P, et al. Long-term creatine intake
is beneficial to muscle performance during resistance training. J Appl
Physiol. 1997;83:2055–2063.
8. Volek JS, Duncan ND, Mazzetti SA, et al. Performance and muscle fiber
adaptations to creatine supplementation and heavy resistance training.
Med Sci Sports Exerc. 1999;31:1147–1156.
9. Cancela P, Ohanian C, Cuitino R, et al. Creatine supplementation does not
affect clinical health markers in football players. Br J Sports Med. 2008;
10. Persky AM, Rawson ES. Safety of creatine supplementation. Subcell
Biochem. 2007;46:275–289.
11. Shao A, Hathcock JN. Risk assessment for creatine monohydrate. Regul
Toxicol Pharmacol. 2006;45:242–251.
12. Ferrando AA, Tipton KD, Doyle D, et al. Testosterone injection stimulates
net protein synthesis but not tissue amino acid transport. Am J Physiol.
13. Kraemer WJ, Hatfield DL, Spiering BA, et al. Effects of a multi-nutrient
supplement on exercise performance and hormonal responses to
resistance exercise. Eur J Appl Physiol. 2007;101:637–646.
14. Op’t Eijnde B, Hespel P. Short-term creatine supplementation does not
alter the hormonal response to resistance training. Med Sci Sports Exerc.
15. Volek JS, Ratamess NA, Rubin MR, et al. The effects of creatine supple-
mentation on muscular performance and body composition responses to
short-term resistance training overreaching. Eur J Appl Physiol. 2004;91:
16. Bang HJ, Yang YJ, Lho DS, et al. Comparative studies on level of
androgens in hair and plasma with premature male-pattern baldness.
J Dermatol Sci. 2004;34:11–16.
17. Geller J, Sionit L. Castration-like effects on the human prostate of a
5 alpha-reductase inhibitor, finasteride. J Cell Biochem Suppl. 1992;16H:
18. Castro-Magana M, Angulo M, Fuentes B, et al. Effect of finasteride on
human testicular steroidogenesis. J Androl. 1996;17:516–521.
19. Zhou ZX, Lane MV, Kemppainen JA, et al. Specificity of ligand-
dependent androgen receptor stabilization: receptor domain interactions
influence ligand dissociation and receptor stability. Mol Endocrinol. 1995;
20. Bemben MG, Bemben DA, Loftiss DD, et al. Creatine supplementation
during resistance training in college football athletes. Med Sci Sports
Exerc. 2001;33:1667–1673.
21. Withers RT, Craig NP, Bourdon PC, et al. Relative body fat and
anthropometric prediction of body density of male athletes. Eur J Appl
Physiol Occup Physiol. 1987;56:191–200.
22. Ziegenfuss TN, Lowery LM, Lemon PWR. Acute fluid volume changes in
men during three days of creatine supplementation. J Exerc Physiol
Online. 1998;1(3).
23. Safdar A, Yardley NJ, Snow R, et al. Global and targeted gene expression
and protein content in skeletal muscle of young men following short-term
creatine monohydrate supplementation. Physiol Genomics. 2008;32:
24. Snow RJ, McKenna MJ, Selig SE, et al. Effect of creatine supplementation
on sprint exercise performance and muscle metabolism. J Appl Physiol.
25. Ahmun RP, Tong RJ, Grimshaw PN. The effects of acute creatine
supplementation on multiple sprint cycling and running performance in
rugby players. J Strength Cond Res. 2005;19:92–97.
26. Hoffman JR, Ratamess NA, Ross R, et al. Effect of a pre-exercise energy
supplement on the acute hormonal response to resistance exercise.
J Strength Cond Res. 2008;22:874–882.
27. Ratamess NA, Hoffman JR, Ross R, et al. Effects of an amino acid/
creatine energy supplement on the acute hormonal response to resistance
exercise. Int J Sport Nutr Exerc Metab. 2007;17:608–623.
28. Hoffman J, Ratamess N, Kang J, et al. Effect of creatine and
beta-alanine supplementation on performance and endocrine responses
in strength/power athletes. Int J Sport Nutr Exerc Metab. 2006;16:
29. Crowe MJ, O’Connor DM, Lukins JE. The effects of beta-hydroxy-beta-
methylbutyrate (HMB) and HMB/creatine supplementation on indices of
q2009 Lippincott Williams & Wilkins |403
Clin J Sport Med Volume 19, Number 5, September 2009 Creatine Supplementation and DHT:T Ratio in Male Rugby Players
health in highly trained athletes. Int J Sport Nutr Exerc Metab. 2003;13:
30. Bartsch W, Krieg M, Voigt KD. Quantification of endogenous
testosterone, 5 alpha-dihydrotestosterone and 5 alpha-androstane-3 alpha,
17 beta-diol in subcellular fractions of the prostate, bulbocavernosus/
levator ani muscle, skeletal muscle and heart muscle of the rat. J Steroid
Biochem. 1980;13:259–264.
31. Gormley GJ. Finasteride: a clinical review. Biomed Pharmacother. 1995;
32. Wright AS, Thomas LN, Douglas RC, et al. Relative potency of
testosterone and dihydrotestosterone in preventing atrophy and apoptosis
in the prostate of the castrated rat. J Clin Invest. 1996;98:2558–2563.
33. Howell S, Shalet S. Testosterone deficiency and replacement. Horm Res.
2001;56(Suppl 1):86–92.
34. Hourde C, Jagerschmidt C, Clement-Lacroix P, et al. Androgen
replacement therapy improves function in male rat muscles independently
of hypertrophy and activation of the Akt/mTOR pathway. Acta Physiol
(Oxf). 2009;195:471–482.
35. Diel P, Baadners D, Schlupmann K, et al. C2C12 myoblastoma cell
differentiation and proliferation is stimulated by androgens and associated
with a modulation of myostatin and Pax7 expression. J Mol Endocrinol.
36. Singh R, Artaza JN, Taylor WE, et al. Androgens stimulate myogenic
differentiation and inhibit adipogenesis in C3H 10T1/2 pluripotent cells
through an androgen receptor-mediated pathway. Endocrinology. 2003;
37. Litman HJ, Bhasin S, Link CL, et al. Serum androgen levels in black,
Hispanic, and white men. J Clin Endocrinol Metab. 2006;91:4326–4334.
38. Wilson JD. The role of 5 alpha-reduction in steroid hormone physiology.
Reprod Fertil Dev. 2001;13:673–678.
39. Roehrborn CG, McConnell JD. Benign prostatic hyperplasia: etiology,
pathophysiology, epidemiology, and natural history. In: Wein AJ,
Kavoussi LR, Novick AC, eds. Urology. Philadelphia, PA: WB Saunders;
40. Heracek J, Hampl R, Hill M, et al. Tissue and serum levels of principal
androgens in benign prostatic hyperplasia and prostate cancer. Steroids.
41. Eaton NE, Reeves GK, Appleby PN, et al. Endogenous sex hormones and
prostate cancer: a quantitative review of prospective studies. Br J Cancer.
404 | q2009 Lippincott Williams & Wilkins
Merwe et al Clin J Sport Med Volume 19, Number 5, September 2009
... The vast majority of speculation regarding the relationship between creatine supplementation and hair loss/ baldness stems from a single study by van der Merwe et al. [61] where college-aged male rugby players who supplemented with creatine (25 g/day for 7 days, followed by 5 g/day thereafter for an additional 14 days) experienced an increase in serum dihydrotestosterone (DHT) concentrations over time. Specifically, DHT increased by 56% after the seven-day loading period, and remained 40% above baseline values after the 14-day maintenance period. ...
... Given that changes in these hormones, particularly DHT, have been linked to some (but not all) occurrences of hair loss/baldness [62], the theory that creatine supplementation leads to hair loss / baldness gained some momentum and this potential link continues to be a common question / myth today. It is important to note that the results of van der Merwe et al. [61] have not been replicated, and that intense resistance exercise itself can cause increases in these androgenic hormones. ...
... In males, DHT can bind to androgen receptors in susceptible hair follicles and cause them to shrink, ultimately leading to hair loss [64]. However, in the van der Merwe et al. [61] study, no increase in total testosterone was found in the 16 males who completed the study. Free testosterone was not measured. ...
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Supplementing with creatine is very popular amongst athletes and exercising individuals for improving muscle mass, performance and recovery. Accumulating evidence also suggests that creatine supplementation produces a variety of beneficial effects in older and patient populations. Furthermore, evidence-based research shows that creatine supplementation is relatively well tolerated, especially at recommended dosages (i.e. 3-5 g/day or 0.1 g/kg of body mass/day). Although there are over 500 peer-refereed publications involving creatine supplementation, it is somewhat surprising that questions regarding the efficacy and safety of creatine still remain. These include, but are not limited to: 1. Does creatine lead to water retention? 2. Is creatine an anabolic steroid? 3. Does creatine cause kidney damage/renal dysfunction? 4. Does creatine cause hair loss / baldness? 5. Does creatine lead to dehydration and muscle cramping? 6. Is creatine harmful for children and adolescents? 7. Does creatine increase fat mass? 8. Is a creatine ‘loading-phase’ required? 9. Is creatine beneficial for older adults? 10. Is creatine only useful for resistance / power type activities? 11. Is creatine only effective for males? 12. Are other forms of creatine similar or superior to monohydrate and is creatine stable in solutions/beverages? To answer these questions, an internationally renowned team of research experts was formed to perform an evidence-based scientific evaluation of the literature regarding creatine supplementation.
... Poziom DHT wzrósł o 56% po siedmiodniowym okresie ładowania i pozostał podniesiony o 40% powyżej wartości wyjściowych po 14-dniowym okresie utrzymania. Nie wpłynęło to jednak na utratę włosów czy łysienie [33]. U mężczyzn DHT może wiązać się z receptorami androgenowymi w podatnych mieszkach włosowych i powodować ich obkurczanie, co ostatecznie prowadzi do utraty włosów [34]. ...
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Creatine is an amino acid derivative, which play a key role in the process of energy production in human body. Creatine is synthetized with participation of 3 amino acids arginine, glycine and methionine and is accumulated as a free creatine and phosphocreatine (PCr), mainly in skeletal muscles. PCr is a high-energy phosphate source of energy, used during resynthesize of adenosine triphosphate (ATP), which is highly important during some stressful situations (e.g. physical activity, mental activity, health disorders/diseases) as well as in during the ischemia and/or hypoxia. Creatine supplementation can play a important role in modulating growth factors and increasing the potential of myosatelite cells formation, causing muscle tissue growth. The main sources of creatine in the diet, aside from supplementation, are animal products. Creatine levels in vegans are significant lower, than in the omnivores. The longest available on the market and the best examined chemical form of creatine is creatine monohydrate, which characterized by high bioavailability, high safety level and the numerous researches confirming its properties. Despite the multitude of creatine forms available currently on the market, there is no evidence confirming greater potential in increasing muscle creatine concentration during their supplementation. Creatine can be used in many sport disciplines, especially those characterized by highintensity efforts, lasting up to 30 seconds The significant fluctuations of creatine levels are observed throughout life and during menstrual cycle in the females. It is associated with the frequency of various health disorders which severity and incidence rate seems to be possible to change by the creatine supplementation. The paper is a summary of the current knowledge and evidence regarding the role of creatine in human body, the possibility of its use as a dietary supplement, the supplementation protocols, doses and safety of use. It also gives answers to most frequently asked questions about creatine supplementation.
... We also showed that creatine consumption did not cause prostate enlargement (Figure 2). CMS has been anecdotally associated with prostate enlargement by increasing dihydrotestosterone levels [19,20]. Since only one study has suggested that CMS may increase dihydrotestosterone levels, and the lack of evidence for the association between this biochemical finding and prostatic hypertrophy, there is no basis to believe that CMS can cause this condition. ...
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Introduction: Several studies examined the effects of creatine monohydrate supplementation on renal function, but no previous study has investigated its effects on kidney stones in humans. Observation: A renal ultrasound in a healthy young athlete (without a known renal morphological anomaly, normal kidney function, normal phospholipid and uric acid data) revealed a kidney stone of 11 mm in the lower right calyx. Extracorporeal shock wave lithotripsy was applied in order to break the down stone. Twentyone days later, a follow-up renal ultrasound showed the absence of stones in the kidney. One week later, the athlete started creatine monohydrate supplementation for two months. Fourteen months after stopping creatine monohydrate supplementation, a third renal ultrasound confirmed the absence of stones in the kidney. Conclusion: Two months of creatine monohydrate supplementation in an athlete with a history of kidney stones could not be associated with kidney stone recurrence in the long run.
... Our results support previous research that reported a significant elevation in resting testosterone concentration [45,46] after Cr loading and no alteration following BA supplementation [21]. In contrast, some studies have shown that Cr loading did not change hormonal status [47,48]. Furthermore, the implications of a small rise in endogenous levels of testosterone on muscle adaptations are controversial and may only play a minor role [49]. ...
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The purpose was to investigate the effects of a 7-day creatine (Cr) loading protocol at the end of four weeks of β-alanine supplementation (BA) on physical performance, blood lactate, cognitive performance, and resting hormonal concentrations compared to BA alone. Twenty male military personnel (age: 21.5 ± 1.5 yrs; height: 1.78 ± 0.05 m; body mass: 78.5 ± 7.0 kg; BMI: 23.7 ± 1.64 kg/m2 ) were recruited and randomized into two groups: BA + Cr or BA + placebo (PL). Participants in each group (n = 10 per group) were supplemented with 6.4 g/day of BA for 28 days. After the third week, the BA + Cr group participants were also supplemented with Cr (0.3 g/kg/day), while the BA + PL group ingested an isocaloric placebo for 7 days. Before and after supplementation, each participant performed a battery of physical and cognitive tests and provided a venous blood sample to determine resting testosterone, cortisol, and IGF-1. Furthermore, immediately after the last physical test, blood lactate was assessed. There was a significant improvement in physical performance and mathematical processing in the BA + Cr group over time (p < 0.05), while there was no change in the BA + PL group. Vertical jump performance and testosterone were significantly higher in the BA + Cr group compared to BA + PL. These results indicate that Cr loading during the final week of BA supplementation (28 days) enhanced muscular power and appears to be superior for muscular strength and cognitive performance compared to BA supplementation alone.
... Creatine usage (loading and maintenance phase) was shown to improve dihydrotestosterone to testosterone ratio in college-aged rugby players (Merwe et al., 2009). This may promote muscle mass accrual but the supplements were not batch tested, leading to concerns about supplement contamination. ...
... En el caso del EIMD, algunos estudios han mostrado disminución de la CK [87] y LDH [87][88][89], mientras que otros no han encontrado efectos significativos en valores de CK [88,89]. Por otro lado, solo hay 3 estudios que analicen la el nivel hormonal de los deportistas [90][91][92]. Ninguno de estos estudios muestra diferencias en T y C, salvo el estudio de Vatani y cols. que encuentra un aumento significativo en T [92]. ...
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El monohidrato de creatina (CrM) y el β-hidroxi β-metilbutirato (HMB) son suplementos deportivos ampliamente estudiados. Sin embargo, no está claro cómo actúan cuando se utilizan conjuntamente en el ámbito deportivo. Hay que añadir que la incógnita es todavía mayor, cuando hablamos de un deporte de carácter predominantemente aeróbico como el remo. Los objetivos de esta tesis han sido: 1) determinar mediante una revisión sistemática la eficacia de mezclar CrM más HMB en comparación con sus efectos aislados sobre el rendimiento deportivo, la composición corporal, los marcadores de daño muscular inducidos por el ejercicio (EIMD) y las hormonas anabólico-catabólicas. 2) determinar la eficacia y el grado de potenciación de 10 semanas de suplementación con CrM más HMB en el rendimiento deportivo, que se midió mediante una prueba incremental en remeros tradicionales de élite masculinos. 3) determinar el efecto y el grado de potenciación de 10 semanas de suplementación con CrM más HMB en los EIMD y hormonas anabólicas/catabólicas. En base a los objetivos planteados, los principales resultados de la tesis indican que: 1) La combinación de CrM más 3 g/día de HMB durante 1–6 semanas podría producir efectos positivos en el rendimiento deportivo (fuerza y rendimiento anaeróbico) y durante 4 semanas en la composición corporal (aumento de grasa masa libre y disminución de la masa grasa). 2) La ingesta de CrM más HMB durante 10 semanas mostró un efecto sinérgico sobre la potencia aeróbica durante una prueba incremental. 3) La combinación de CrM más HMB presentó un efecto sinérgico sobre la testosterona y la ratio testosterona/cortisol y un efecto antagonista sobre el cortisol en comparación con la suma de la suplementación individual o aislada. Las conclusiones obtenidas en la presente tesis doctoral indican que la combinación de estos dos suplementos puede ser de gran ayuda para los profesionales que rodean al deportista para mejorar el rendimiento aeróbico y la recuperación.
Testosterone boosters are heavily marketed on social media and marketplaces to men with claims to significantly increase testosterone. Lax industry regulation has allowed sales of supplements to thrive in the absence of verification of their purported benefits. Our primary objective was to systematically review all data published in the last two decades on testosterone boosters and determine their efficacy. Our outcome of interest was total testosterone increase versus placebo in four different populations: male athletes, men with late-onset hypogonadism infertile men and healthy men. Following search and screening, 52 studies were included in our review, relating to 27 proposed testosterone boosters: 10 studies of cholecalciferol; 5 zinc/magnesium; 4 Tribulus terrestris and creatine; 3 Eurycoma longifolia and Withania somnifera; 2 betaine, D-aspartic acid, Lepidium meyenii and isoflavones; while the remainder were single reports. Our findings indicate that most fail to increase total testosterone. The exceptions were β-hydroxy β-methylbutyrate and betaine, which can be considered effective for male athletes. Eurycoma longifolia, a blend of Punica granatum fruit rind and Theobroma cacao seed extracts (Tesnor™) and purified Shilajit extract (PrimaVie™) can be considered possibly effective for men with late-onset hypogonadism; Eurycoma longifolia and Withania somnifera possibly effective for healthy men; and a non-hormonal aromatase inhibitor (Novadex XT™) possibly effective for male athletes.
Purpose: Testosterone replacement and associated pharmacologic agents are effective strategies to treat male hypogonadism; however, nutraceutical agents and lifestyle modification approaches have gained medical interest. The purpose of this scoping review is to highlight the evidence (or lack thereof) of nutraceuticals and lifestyle modification approaches in the management of testosterone levels and sperm parameters. Methods: A scoping review of nonpharmacologic interventions (supplements, herbal medicines, diets, sleep, and exercise) with the potential to improve male health was undertaken to elucidate changes in testosterone levels and sperm parameters in men with hypogonadism or infertility compared with healthy patients. Findings: A multitude of nutraceuticals and functional nutrients are purported to stimulate testosterone production; however, only a select few have had promising results, such as zinc, vitamin D (in case of hypovitaminosis D), l-arginine, mucuna, and ashwagandha, based on well-controlled randomized clinical trials of men with low testosterone levels and related problems. Except for l-arginine, these natural agents, as well as tribulus and ω3 fatty acids, can improve some degree of sperm parameters in infertile men. Before implementing these nutraceutical agents, adequate sleep, exercise, and weight loss in patients with obesity are imperative. The effects of nonpharmacologic interventions on testosterone levels are modest and hence do not directly translate into clinical benefits. Correspondingly, androgen receptor content, but not endogenous androgens, has been regarded as the principal factor in muscle hypertrophy. Implications: A limited number of supplements and herbal medicines can be considered as adjunctive approaches in the management of testosterone levels and sperm parameters, primarily in men with low testosterone levels and infertility, whereas most nonpharmacologic supplements appear to lack evidence. Although proper physical exercise, sleep, and diet are indisputable approaches because of the general benefits to health, the use of nutraceuticals, if considered, must be personalized by physicians and/or registered dietitians.
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Handball performance is a team-sport characterized by high intensity efforts interspersed with recovery periods. Due to high demands of handball performance, the use of ergogenic aids is a common strategy of handball players with the aim of enhancing handball performance, to allow more effective training, and to increase the rate of recovery. Although the use of ergogenic aids is generalized in the whole spectrum of competitive handball (e.g., from recreational to professional players), only a few ergogenic aids have been investigated to test their effectiveness to increase handball performance. In addition, no previous study has summarized the scientific literature on this topic to determine the ergogenic aids with good level of evidence regarding their effectiveness to increase handball physical performance. Thus, the aim of this narrative review was to describe the prevalence in the use of ergogenic aids in handball players and to analyse this information to identify which of these substances may increase physical performance in an intermittent sport such as competitive handball
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The literature on creatine supplementation supporting its efficacy has grown rapidly and has included studies in both healthy volunteers and patient populations. However, the first rule in the development of therapeutic agents is safety. Creatine is well-tolerated in most individuals in short-term studies. However, isolated reports suggest creatine may be associated with various side effects affecting several organ systems including skeletal muscle, the kidney and the gastrointestinal tract. The majority of clinical studies fail to find an increased incidence of side effects with creatine supplementation. To date, studies have not found clinically significant deviations from normal values in renal, hepatic, cardiac or muscle function. Few data are available on the long-term consequences of creatine supplementation.
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.
Epidemiological studies strongly support the contention that surgical castration prior to age forty prevents both benign prostatic hypertrophy (BHP) and prostate cancer. 5α-Reductase deficiency in humans, an experiment of nature, is an uncommon genetically transmitted disorder in which prostate size remains very small throughout adult life. A 5α-reductase inhibitor, finasteride, has recently been shown in double-blind, placebo-controlled trails in patients with BPH to statistically decrease prostate size and improve clinical symptoms in comparison to placebo controls. In the untreated BPH prostate, tissue levels of dihydrotestosterone (DHT) and testosterone (T) averaged 4.2 and 0.2 ng/g, respectively. Following one week of finasteride therapy, T levels rose to a mean of 1.32 ng/g while DHT levels decreased to 0.62 ng/g. These values contrast with values in prostate tissue form surgical castrates in which DHT and T values average 1.14 ng/g and 0.1 ng/g, respectively. If we use the relative binding affinity of T and DHT to the androgen receptor as a criterion of biological androgen potency, T would appear to be one-fourth as potent as DHT. Using this 1:4 ratio to convert prostatic T to a biologically equivalent amount of prostatic DHT, the total biologically active DHT equivalent in the prostate following one week of finasteride averages 0.95 ng/g compared to a mean of 1.14 ng/g in surgical castrates. If the acute effects of finasteride on tissue T and DHT persist during chronic therapy, prostatic hormone concentrations could be said to closely resemble those found following surgical castration; such changes might prevent the occurrence of prostate cancer, similar to the effects noted after surgical castration in younger males. © 1992 Wiley-Liss, Inc.
Testosterone (T), 5α-androstan-17β-ol-3-one (dihydrotestosterone, DHT) and 5α-androstane-3α,17β-diol (3α-diol) were measured by radioimmunoassay (RIA) in the tissue homogenates, cytosols and nuclear fractions of the prostate (PR), bulbocavernosus/levator ani muscle (BCLA), skeletal muscle (musculus quadriceps femoris, SM) and heart muscle (HM) of adult male rats. The main results were: (a) In all three of the PR preparations the main metabolite found was DHT. T could not be detected in the cytosol and 3α-diol was absent in the nuclei, (b) The muscles contained predominantly T. Besides the homogenates DHT was found only in the nuclear fractions. 3α-diol could only be detected in the homogenates and HM-cytosol but not in the nuclei, (c) Comparing the various organs, a clear ranking, PR > BCLA > SM > HM, was found for DHT in the homogenates and similarly but less pronounced in the nuclear fractions, whereas T was generally higher in the muscle homogenates, cytosols and nuclear fractions than in the PR.These data are discussed with respect to the present knowledge of specific androgen accumulation and metabolism in the different organs.
Many of the neuromuscular (e.g., muscular dystrophy) and neurometabolic (e.g., mitochondrial cytopathies) disorders share similar final common pathways of cellular dysfunction that may be favorably influenced by creatine monohydrate (CrM) supplementation. Studies using the mdx model of Duchenne muscular dystrophy have found evidence of enhanced mitochondrial function, reduced intra-cellular calcium and improved performance with CrM supplementation. Clinical trials in patients with Duchenne and Becker's muscular dystrophy have shown improved function, fat-free mass, and some evidence of improved bone health with CrM supplementation. In contrast, the improvements in function in myotonic dystrophy and inherited neuropathies (e.g., Charcot-Marie-Tooth) have not been significant. Some studies in patients with mitochondrial cytopathies have shown improved muscle endurance and body composition, yet other studies did not find significant improvements in patients with mitochondrial cytopathy. Lower-dose CrM supplementation in patients with McArdle's disease (myophosphorylase deficiency) improved exercise capacity, yet higher doses actually showed some indication of worsened function. Based upon known cellular pathologies, there are potential benefits from CrM supplementation in patients with steroid myopathy, inflammatory myopathy, myoadenylate deaminase deficiency, and fatty acid oxidation defects. Larger randomized control trials (RCT) using homogeneous patient groups and objective and clinically relevant outcome variables are needed to determine whether creatine supplementation will be of therapeutic benefit to patients with neuromuscular or neurometabolic disorders. Given the relatively low prevalence of some of the neuromuscular and neurometabolic disorders, it will be necessary to use surrogate markers of potential clinical efficacy including markers of oxidative stress, cellular energy charge, and gene expression patterns.
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.
We analysed the effect of physiological doses of androgens following orchidectomy on skeletal muscle and bone of male rats, as well as the relationships between muscle performance, hypertrophy and the Akt/mammalian target of rapamycin (mTOR) signalling pathway involved in the control of anabolic and catabolic muscle metabolism. We studied the soleus muscle and tibia from intact rats (SHAM), orchidectomized rats treated for 3 months with vehicle (ORX), nandrolone decanoate (NAN) or dihydrotestosterone (DHT). Orchidectomy had very little effect on the soleus muscle. However, maximal force production by soleus muscle (+69%) and fatigue resistance (+35%) in NAN rats were both increased when compared with ORX rats. In contrast, DHT treatment did not improve muscle function. The relative number of muscle fibres expressing slow myosin heavy chain and citrate synthase activity were not different in NAN and ORX rats. Moreover, NAN and DHT treatments did not modify muscle weights and cross-sectional area of muscle fibres. Furthermore, phosphorylation levels of downstream targets of the Akt/mTOR signalling pathway, Akt, ribosomal protein S6 and eukaryotic initiation factor 4E-binding protein 1 were similar in muscles of NAN, DHT and ORX rats. In addition, trabecular tibia from NAN and DHT rats displayed higher bone mineral density and bone volume when compared with ORX rats. Only in NAN rats was this associated with increased bone resistance to fracture. Physiological doses of androgens are beneficial to muscle performance in orchidectomized rats without relationship to muscle and fibre hypertrophy and activation of the Akt/mTOR signalling pathway. Taken together our data clearly indicate that the activity of androgens on muscle and bone could participate in the global improvement of musculoskeletal status in the context of androgen deprivation induced by ageing.
To study the effects of 8-week creatine monohydrate (CrM) supplementation on blood and urinary clinical health markers in football players. 14 football players were randomly assigned in a double-blinded fashion to Cre (n = 7) or Pla (n = 7) group. The Cre group ingested 15 g/day of CrM for 7 days and 3 g/day for the remaining 49 days, whereas the Pla group ingested maltodextrin following the same protocol. Football-specific training was performed during the study. Total body mass was determined and blood and urine samples were analysed for metabolic, hepatic, renal and muscular function markers, before and after supplementation. A gain of total body mass was observed after CrM intake, but not with placebo. Blood and urinary markers remained within normal reference values. There were no significant changes in renal and hepatic markers after CrM intake. However, total creatine kinase (CK) activity significantly increased, and uric acid level tended to decrease after CrM use. Likewise, serum glucose decreased in the Cre group following supplementation. No significant differences in urine parameters were found in either group after supplementation. 8 weeks of CrM supplementation had no negative effects on blood and urinary clinical health markers in football players. Properties of CrM may, however, be associated with an increase in CK activity, improving the efficiency for ATP resynthesis, a phenomenon indirectly confirmed by the decreasing tendency in uric acid concentration. Furthermore, CrM seems to slightly influence glucoregulation in trained subjects.