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Acta Physiol
Scand
1995,
153,
207-209
The effect
of
creatine monohydrate ingestion on
anaerobic power indices, muscular strength and
body
composition
C.
P.
EARNEST,’
P.
G.
SNELL,’
R.
RODRIGUEZ,
A.
L.
ALMADA
and
T.
L.
MITCHELL3
‘Texas Woman’s University, Department
of
Kinesiology,
Denton,
‘The
University
of
Texas Southwestern Medical Center and 3The Cooper Clinic, Dallas, Texas,
USA
Creatine monohydrate (Cr.H20) has been shown to
increase intramuscular phosphocreatine (Harris et
a/.
1992) as well as increasing the power output of various
high intensity work tasks (Balsom et
al.
1993,
Greenhaff
et
al.
1993). To the author’s knowledge,
Cr.H20 supplementation in strength trained athletes
has not yet been reported in the literature. Therefore,
this study investigated the influence of Cr.H20
supplementation on muscular power and strength
indices in
10
experienced weight-trained male subjects.
Three series of high intensity, anaerobic type,
muscular workbouts were used. Series one included
three consecutive 30-s Wingate bike tests, interspersed
with 5 min of rest. Peak anaerobic power was denoted
as the greatest power achieved in a given 5-s work
interval. Anaerobic work was defined as the total
amount of work performed in a 30-s period. Series
two utilized
a
one repetition maximum (1 RM) free
weight bench press as a test of muscular strength.
Series three employed complete lifting repetitions at
70% of the bench press
1
RM until fatigue. Lifting
cadence was paced through the use of a metronome set
at a 1-s timing interval (1
s
eccentric, 1
s
concentric)
and fatigue was defined as (1) the inability to complete
one lifting repetition or (2) the inability to maintain
the lifting cadence. Total lifting volume was calculated
as 70% of pre-test 1 RM multiplied by the number of
complete lifting repetitions. Body composition was
measured via hydrostatic weighing techniques; a 3-
day recall was used to assess dietary differences
between groups.
All
procedures were approved by the
Human Subjects Review Board of Texas Woman’s
University, Denton, Texas.
Received 19 September 1994, accepted 13 October
Key
words
:
anaerobic power, body composition,
Correspondence
:
Conrad
P.
Earnest, 7855 Willow
1994.
creatine, muscular strength.
Hill Court
-
Ste. 233, Dallas, TX 75230, USA.
Subjects received, in
a
double blind fashion, either
a glucose placebo or Cr.H20 supplement (Phosphagen,
Experimental and Applied Sciences Inc., Pacific
Grove, CA, USA) as has previously been shown to be
successful (Harris et
al.
1992, Greenhaff
et
al.
1993).
After 14 days of supplementation, each subject was re-
tested
on
the Wingate bike tests. Re-testing for the
weight lifting and anthropometric parameters took
place after 28 days of supplementation. An
ANOVA
for
repeated measures was utilized
to
assess differences
within the Wingate test groups. If statistical signifi-
cance was found,
a
Newman-Keuls post-hoc analysis
was applied.
A
paired dependent t-test was used to
determine differences associated with bench press
1
RM,
total lifting volume and anthropometric
measures. An independent t-test was used to de-
termine differences in nutritional/energy intake.
Statistical significance was set at
P
6
0.05. All values
are listed as pre- vs. post-test and mean
(&
SD).
Eight subjects completed the experimental protocol.
Age was 29.5
f
3.6 and 31.8
f
2.2 years, training
experience was 10.8f3.2 and 11.1 f2.4 years and
percentage of body fat was 10.1
f
3.7 and 9.4f4.6 for
the Cr.H20 and placebo groups, respectively. Within
the Cr.H20 group
(n
=
4), total anaerobic work for
the Wingate tests was significantly higher during all
post-test trials (P
<
0.05). These increases were 13%
for Wingate test 1,
18%
for Wingate test 2 and 18%
for Wingate test 3.
No
changes were noted in the
placebo group
(n
=
4, Table
1).
Greater total an-
aerobic work resulted from the Cr.H20 subject’s
ability to achieve and maintain higher levels of
anaerobic power consistently over each
5-s
time
interval, with statistical significance being apparent
for several 5-s power intervals during the three trials
(data not shown).
Bench press 1 RM increased 6% in the Cr.H20
group (P
<
0.05). When corrected for body weight no
differences were noted because of a significant increase
in body weight within the Cr.H20 group. Total lifting
207
208
C.
P.
Earnest
et
al.
Table
1.
Anaerobic indices values for Cr.H20 and placebo groups. Values are mean and SD
("P
<
0.05,
t
P
<
0.01, and
1
P
<
0.001)
~ ~~ ~~ ~~~~ ~~~ ~
Creatine Placebo
Anaerobic indices Pre Post Pre Post
30-s Wingate bike tests
1 (kJ)
2
(kJ)
3 (kJ)
Bench press 1 RM
Absolute (kg)
Relative (kg kg-')
Lifting repetitions (70% 1
RM)
Total lifting volume
Absolute (kg)
Relative (kg kg-')
22.65 (3.0)
20.40 (2.0)
18.54 (1.0)
126.4
(20.5)
1.5
(0.1)
11.5 (0.8)
1017.7 (93.5)
11.7 (0.7)
25.98 (4.0)*
24.49 (3.0)*
22.73
(2.0)*
134.6 (18.9)*
1.5 (0.1)
15.5
(I.5)t
1459.0 (122.3)f
16.5 (0.9)f
23.48 (1.0)
21.15 (2.0)
119.1 (13.0)
1.4
(0.1)
11.7 (1.8)
975.1 (120.9)
11.8 (1.2)
22.08 (2.0) 23.51 (1.0)
22.32 (2.0)
21.4 (2.0)
116.2 (15.0)
1.4 (0.1)
11.7
(0.8)
951.7 (132.0)
11.5 (1.5)
volume was significantly higher within the Cr.H20
group, whether expressed in absolute terms (26%,
P
<
0.01) or relative terms (29%,
P
<
0.001). In-
creases in total lifting volume were associated with the
ability
of
the Cr.H20 group to perform 26% more
lifting repetitions
(P
<
0.01, Table 1). Body com-
position data indicated a significant increase in body
weight (86.5+ 13.7 vs. 88.2+ 14.1 kg,
P
<
0.05),
as
well as
a
non-significant increase
in
calculated fat free
mass (77.6
f
10.8 vs. 79.2
f
11.6 kg,
P
=
0.054) for
the Cr.H20 group.
No
changes in body weight
(82.6f 2.2 vs. 82.5 1.8 kg) or fat free mass (74.9
f
6.6
vs. 74.4 6.2 kg) were noted for the placebo group. In
addition, no significant differences were noted for
percentage of body fat in either group. These
observations were noted in spite of a significantly
lower daily energy intake (10031 1458 vs.
14650+ 1234 kJ;
P
<
0.01), carbohydrate intake
(5918f860 vs. 7315+617
kJ;
P
<
0.05),
and fat
intake (1204+175 vs. 4354+368 kJ;
P
<
0.05) for
the Cr.H+l vs. placebo groups, respectively.
The observed higher work outputs in the Cr.H20
group were consistent with increases in intramuscular
phosphocreatine stores as noted previously (Harris
et
al.
1992), increased ATP cycling through an attenuated
reduction in ATP with repeated work tasks (Greenhaff
et
al.
1994 b), and an increased rate of phosphocreatine
resynthesis during recovery periods (Greenhaff
et
al.
1994a). What is not clear is the associated gain in body
weight observed in our study as well as those of others
(Balsom
et
al.
1993, Greenhaff
et
al.
1994a). We are
the first group to show that: (1) Cr.H20 supplemen-
tation improves strength training parameters and (2)
that the associated weight gain may be related to an
increase in fat free mass as determined through
hydrostatic weighing techniques.
In
addition, because
weight lifting tasks are typically performed
at
sub-
maximal 1 RM levels during training, the ability
of
the Cr.H20 group to perform a greater total lifting
volume, both in absolute and relative terms, demon-
strates the efficacy of Cr.H20 as an ergogenic aid.
In
turn, the ability
to
perform greater muscular work,
per given work task, provides
a
greater muscular
overload that may promote an increased adaptive
response
in
muscular structure and function.
This
adaptation may account for the observed increase
in
bench press 1 RM, body weight and fat free mass.
Whether or not Cr.H20
per
se,
is directly responsible
for this increase in body weight has yet to be
determined.
We thank Christopher B. Scott
of
the Dallas Heart
Group for his help in the preparation of this
manuscript. This study was supported by
a
grant
from Experimental and Applied Sciences, Inc. Pacific
Grove, CA, USA.
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