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Changes in human muscle protein synthesis after exercise


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The purpose of this study was to investigate the magnitude and time course for changes in muscle protein synthesis (MPS) after a single bout of resistance exercise. Two groups of six male subjects performed heavy resistance exercise with the elbow flexors of one arm while the opposite arm served as a control. MPS from exercised (ex) and control (con) biceps brachii was assessed 4 (group A) and 24 h (group B) postexercise by the increment in L-[1-13C]leucine incorporation into muscle biopsy samples. In addition, RNA capacity and RNA activity were determined to assess whether transcriptional and/or translational processes affected MPS. MPS was significantly elevated in biceps of the ex compared with the con arms of both groups (group A, ex 0.1007 +/- 0.0330 vs. con 0.067 +/- 0.0204%/h; group B ex 0.0944 +/- 0.0363 vs. con 0.0452 +/- 0.0126%/h). RNA capacity was unchanged in the ex biceps of both groups relative to the con biceps, whereas RNA activity was significantly elevated in the ex biceps of both groups (group A, ex 0.19 +/- 0.10 vs. con 0.12 +/- 0.05 micrograms protein.h-1.microgram-1 total RNA; group B, ex 0.18 +/- 0.06 vs. con 0.08 +/- 0.02 micrograms protein.h-1.microgram-1 total RNA). The results indicate that a single bout of heavy resistance exercise can increase biceps MPS for up to 24 h postexercise. In addition, these increases appear to be due to changes in posttranscriptional events.
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Changes in human muscle protein synthesis
after resistance exercise
Departments of Physical Education, Medicine, and Pediatrics, McMaster University, Hamilton,
Ontario L8S 4K1, Canada
A., J. D.
M. A.
S. A.
Changes in human musclepro-
tein synthesis after resistance exercise. J. Appl. Physiol. 73(4):
l383-1388,1992.-The purpose of this study was to investigate
the magnitude and time course for changes in muscle protein
synthesis (MPS) after a single bout of resistance exercise. Two
groups of six male subjects performed heavy resistance exercise
with the elbow flexors of one arm while the opposite arm served
as a control. MPS from exercised (ex) and control (con) biceps
brachii was assessed 4 (group A) and 24 h (group B) postexer-
cise by the increment in L-[ l-‘3C]leucine incorporation into
muscle biopsy samples. In addition, RNA capacity and RNA
activity were determined to assess whether transcriptional
and/or translational processes affected MPS. MPS was signifi-
cantly elevated in biceps of the ex compared with the con arms
of both groups (group A, ex 0.1007 t 0.0330 vs. con 0.067 t,
0.0204 %/h; group B ex 0.0944 t 0.0363 vs. con 0.0452 t 0.0126
%/h). RNA capacity was unchanged in the ex biceps of both
groups relative to the con biceps, whereas RNA activity was
significantly elevated in the ex biceps of both groups (group A,
ex 0.19 2 0.10 vs. con 0.12 t 0.05 pg protein
pg-’ total
RNA; group B, ex 0.18 -+ 0.06 vs. con 0.08 t 0.02 pg pro-
h-’ . pg-l total RNA). The results indicate that a single
bout of heavy resistance exercise can increase biceps MPS for
up to 24 h postexercise. In addition, these increases appear to
be due to changes in posttranscriptional events.
L- [ l- 13C] leucine incorporation; ribonucleic acid capacity; ribo-
nucleic acid activity
that a program of heavy resistance
training can lead to substantial gains in strength and
muscle hypertrophy
The observed increases
in muscle size are due to acute and chronic increases in
muscle protein turnover such that protein synthesis ex-
ceeds protein degradation (9,
Although both acute
and chronic increases in protein synthesis have been
demonstrated in muscles of animals undergoing hyper-
trophy in response to tenotomy or stretch (9,
perturbations do not really simulate resistance training
as performed by humans (23, 25). Thus there are few
data available regarding the time course and magnitude
of the acute changes in muscle protein synthesis (MPS)
after resistance exercise in humans.
On the basis of a review of animal studies involving
muscle stretch, various exercise protocols, or electrical
stimulation, Booth et al.
postulated that acute in-
creases in muscle protein synthesis occur
h postexer-
cise and may remain elevated above basal levels for an
undefined period thereafter. It also appears that the
magnitude of the increase in MPS is dependent on the
type, intensity, and duration of exercise (3,4). Increases
in total mixed and myofibrillar protein synthetic rates
ranging from
to 65% have been documented in rat
gastrocnemius and tibialis anterior
and 41 h after the
completion of a single bout of concentric or eccentric
resistance exercise
(30, 31).
In humans, MPS has been
shown to increase by
in vastus lateralis
h after a
single bout of low-intensity treadmill running (6). In ad-
dition, whole body protein synthesis (WBPS) was un-
changed for up to
h after an acute bout of circuit-type
resistance exercise performed at
of the one-repeti-
tion maximum
whereas WBPS increased in resis-
tance- #trained males
h after a simi .lar exercise protocol
when compared with age-matched sedentary controls
MPS has been shown to account for -2530% of
and thus increases in WBPS are likely to be
due in part to increases in MPS.
The -mechanisms that mediate acute changes in MPS
in response to resistance exercise are not yet known.
Wang-and Booth
(30, 31)
found increases in RNA activ-
ity after a single bout of concentric or eccentric resis-
tance exercise. RNA activity reflects changes in post-
transcriptional events and is used as an index of the effec-
tiveness of the ribosomal machinery in translating
existing mRNA species into protein molecules (27).
There is also indirect evidence suggesting that RNA ac-
tivity may change before RNA capacity (an index of
changes in transcriptional events) during conditions in-
volving acute changes in muscle activity (3).
The purpose of this study was to examine the magni-
tude and time course of changes in mixed muscle protein
synthetic rates in humans after a single bout of resis-
tance exercise. In addition, RNA capacity and RNA activ-
were measured to indicate overall changes in
transcriptional and/or translational control processes,
Twelve healthy males who regularly engaged
in resistance training served as subjects. They were ad-
vised of the risks associated with the study and provided
written informed consent. The study was approved by
the University Human Ethics Committee. Subjects were
assigned to either a
h postexercise group
(group A)
or a
h postexercise group
B). Subjects were re-
0161-7567192 $2.00 Copyright 0 1992 the American Physiological Society 1383
1. Subject descriptive data
Characteristic A
AiF, Yr 25.1k3.9
Height, m 1.76kO.09
Body weight, kg 79.3t5.1
Lean body weight, kg 67.Ok5.1
Body fat, % 15.4k5.1
Years of training 4.9k6.6
Daily energy intake, kcal 3,076+602
Values are means + SD; n = 6 in each group.
cruited so that the two groups could be equated on the
basis of resistance training experience and maximal el-
bow flexor strength. Group characteristics are provided
in Table 1.
Preexperimmtal mmsurements. Maximum elbow flexor
strength [single maximum repetition (lRM)] of the domi-
nant arm was determined for the biceps curl, preacher
curl, and concentration curl exercises. Body density was
determined by hydrostatic weighing, with residual lung
volume measured by helium dilution. Percent body fat
was then calculated according to the Brozek method (5).
Three-day food records (including 1 weekend day) were
obtained from each subject for the determination of
mean daily energy and protein intakes with use of a com-
puter program for nutrient analysis (Nutritionist III, Sil-
verton, OR).
Experimental protocol. The six subjects in group A per-
formed the resistance exercise protocol on the day of the
leucine infusion, whereas the six subjects in group B ex-
ercised the day before the leucine infusion. Measure-
ments were made after 3 days of rest during which no
resistance training was performed. The exercise protocol
consisted of four sets of
repetitions of the biceps
curl, preacher curl, and concentration curl with a resis-
tance equal to 80% of the 1 RM. All sets were performed
to muscular failure, and rest periods of 3 min were pro-
vided between sets and exercises. For 2 h before and dur-
ing the entire leucine infusion protocol, subjects received
50% of their individual mean energy intake as a defined
formula diet (Ensure, Ross Laboratories, Montreal,
Canada) to ensure a consistent rate of appearance of en-
dogenous energy and protein. Feedings were given in
equal aliquots every 30 min (17 aliquots total) during the
study protocol. Group A received a primed continuous
infusion of L-[ lJ3C]leucine beginning 0.68 t 0.20 h pos-
texercise, whereas group B was infused
20.41 t 0.24
postexercise. Subjects in group B were instructed to re-
frain from strenuous activity after the resistance exercise
A 22-gauge plastic catheter was inserted into a suitable
hand vein for blood sampling while a second catheter was
inserted into a vein of the contralateral proximal forearm
vein for isotope infusion. A priming dose of
L- [
mg/kg) was administered by a Harvard
syringe pump followed by a constant infusion of
L-[ l-
13C]leucine (1 mg l kg-’ l h-l) for -6 h (5.4-6.4 h). In all
cases the L-[1-13C]leucine was from the same batch
(MSD Isotopes, Pointe-Claire, Canada) and was con-
firmed to be 99% isotopic pure and sterile by the com-
pany. Batch dilutions (15 g/ml) of the isotope were made
under aseptic conditions, and on the day of the infusion
the isotope was further diluted with sterile saline and
microfiltered immediately before infusion. Arterialized
blood samples (hot box at 65 t 5°C) (1) for the determi-
nation of plasma cu-ketoisocaproic acid (cu-KIC) enrich-
ment were obtained from the hand before the start of the
infusion, 2 h after the priming dose (t = 2 h), approxi-
mately midway (t = 4 h), and at the end of the infusion
protocol (t = 6 h). Blood was collected into heparinized
tubes and centrifuged immediately. The plasma was
stored at -70°C until analysis.
Percutaneous needle biopsies from the distal lateral
portion of the biceps brachii were obtained under local
anesthesia 2 h after the leucine priming dose and once
more at the completion of the leucine infusion protocol.
The 2-h period between the priming dose and the first
biopsies was chosen to ensure that an isotopic plateau
had been reached. This has been demonstrated in a pre-
vious study from our laboratory under similar conditions
(22). Two biopsies were obtained at 2 h (one each from
the control arm and exercised arm) and two more after
the completion of the infusion. The muscle samples were
visibly dissected of fat and connective tissue, frozen in
liquid nitrogen, and transferred to a -7OOC freezer until
Analytic techniques. Tissue was weighed wet, freeze-
dried, ground to a fine powder in liquid nitrogen, and
transferred to tubes containing 3 ml of 0.2 N ice-cold
perchloric acid (PCA). After 20 min of centrifugation at
4”C, the remaining pellet was redissolved in 5 ml of 0.2 N
PCA and centrifuged once more. This step was repeated.
Tissue lipids were then extracted by a series of 5-ml sol-
vent washes followed by 5 min of centrifugation. The
order of the washes was as follows: 1) 1% potassium ace-
tate in ethanol, 2) ethanol-chloroform (3:1), 3) ethanol-
ether (3:l), and 4) ether. Protein was solubilized in 3 ml
of 0.3 M NaOH in a 37°C water bath for 60 min. A 50-~1
aliquot of the supernatant was removed and added to
4.95 ml of 0.3 N NaOH. The alkali-soluble protein was
transferred to clean tubes. Total muscle protein content
was determined by the method of Lowry et al. (11). RNA
was then extracted by dissolving the remaining pellet in 2
ml of 1 M PCA and centrifuging as before. The superna-
tant was transferred to clean tubes for the determination
of RNA. The pellet was rewashed and the supernatant
combined with the RNA supernatant: Samples were then
frozen for the subsequent determination of total RNA by
the method of Tsanev and Markov (26). DNA was ex-
tracted by the addition of 5 ml of 2 M PCA to each tube
followed by incubation for 1 h in a 70°C water bath. The
protein fraction was repelleted by centrifugation for 20
min and the supernatant kept for DNA determination by
the method of Schneider and Greco (17).
The procedure used to isolate and measure
13C]leucine content in muscle tissue was a modification
of the technique described by Smith et al. (20). The pro-
tein pellet obtained after protein/nucleic acid extraction
was hydrolyzed in 6 M HCl, and the resulting amino acid
mixture was applied to an ion-exchange column as previ-
ously described. The samples were then dried in a rotary
evaporator and derivitized with 50-75 ~1 of N-methyl-t-
;;I +fy
r n
CL +2 +4 +6
Time (hours)
FIG. 1. Enrichment of plasma cu-ketoisocaproic acid (wKIC) for
combined groups over period during which muscle protein synthesis
was estimated. Muscle biopsies were taken at 2 and 6-h point of infu-
sion protocol. Note isotopic steady state over this period. Units are
atom percent excess (APE), and values are means + SE (n = 12).
butyldimethylsilyltrifluoroacetamide and an equal vol-
ume of pyridine in an oven at 85OC for 60-90 min.
Preparative gas chromatography, for the isolation of
leucine, was done with a Pye Unicam 304 series chro-
matograph fitted with a postcolumn splitter
ratio) and a wide-bore glass column (6 mm ID
4.6 m) as
previously described (20). The leucine was collected from
the postcolumn splitter in a home-made demountable
glass U trap cooled in liquid nitrogen. The leucine col-
lected in the U trap was removed by the addition of 0.5 ml
of lithium citrate buffer (pH 2.2) to the trap followed by
heating at 90°C for 30 min. The liquid was then trans-
ferred to a 20-ml Vacutainer tube, and the U trap was
rinsed with a further 0.5 ml of buffer. The rubber stop-
pers from the Vacutainers were degassed overnight in a
sealed glass flask in an oven under vacuum at 90°C. The
samples were degassed at 140-150°C in a heating block
for 30 min and placed on ice. Approximately 25 mg of
ninhydrin were added to each tube on ice, and the Vacu-
tainer was evacuated on a vacuum line. The ninhydrin
reaction was carried out in a 90°C water bath for 30 min.
The tubes were then allowed to cool to room temperature
and were filled with nitrogen. The 13C0, enrichment of
the samples was determined by isotope-ratio mass spec-
trometry according to the method of Scrimgeour et al.
Plasma cu-KIC enrichment was determined by capil-
lary gas chromatography/mass spectrometry according
to the method described by Tarnopolsky et al. (22).
Muscle protein synthetic rate was calculated according
to the equation
FMPS = (LE, x lOO)l(K,, x t)
where FMPS is the fractional muscle protein synthetic
rate (%hh), t is the incorporation time (in h) betweer
biopsy samples taken from the same arm (15), LE, is the
increment in 13C abundance in muscle protein obtained
between t = 2 h and
= 6 h biopsy samples from each
arm, and &, is the mean plasma wKIC enrichment for
t=2,4,and6hbl d oo samples (corrected for background
enrichment from the t = 0 h sample).
Biopsy samples for two subjects in group A were found
to be of insufficient size for measurement of protein syn-
thetic rate and RNA activity, and thus data are presented
for only four subjects in group A and six subjects in group
B. Subject descriptive data, elbow flexor strength, train-
ing intensity and volume, and leucine infusion parame-
ters were analyzed with a one-way analysis of variance
(ANOVA). Muscle protein, total RNA, and DNA concen-
trations were analyzed with a two-way ANOVA with re-
peated measures. Protein synthetic rates and RNA activ-
ity were analyzed with a two-way ANOVA with repeated
measures for unequal sample sizes. A Tukey post hoc
analysis was used when significant differences between
means were obtained. P < 0.05 was selected as being in-
dicative of statistical significance. Values are expressed
as means t SD.
The two groups did not differ as to age, height, body
weight, lean body weight, energy intake, or training his-
tory (Table 1). The mean 1 RM for the three biceps exer-
cises was similar between groups as were the mean train-
ing intensity and volume (product of the weight lifted
and the total number of repetitions) for the experi-
mental day.
The mean plasma wKIC enrichments over the three
separate sampling points during infusion were 4.87 t
0.95 and 4.63 t 0.96 atom percent excess for groups A and
B, respectively. These values were consistent over time
with a coefficient of variation of <8.7%, thus demonstrat-
ing isotopic steady state (Fig. 1).
Total muscle protein expressed as a percentage of
muscle wet weight was similar between groups and be-
tween the exercised and control biceps. In addition, mus-
cle RNA and DNA concentrations were similar between
groups and between arms (Table 2). The values of enrich-
ment of 13C in muscle are presented in Table 3. Muscle
protein synthetic rates were significantly elevated in ex-
ercised compared with control biceps of both groups
(group A,
%/h; group B,
0.0944 t 0.0363 vs. 0.0452 t 0.0126
%/h; Fig. 2). The
observed differences in MPS were apparently due to a
significant increase in RNA activity in the exercised vs.
control biceps of both groups (group A,
0.19 t 0.10 vs.
t 0.05 pg protein l h-l l pgvl of RNA; group B,
0.18 t
vs. 0.08 t 0.02 pug protein l h-’ l p8-l of RNA; Fig. 3).
Muscle protein content and total RNA
(capacity) and DNA concentration
Protein Content,
5% wet wt RNA, DNA,
pg/mg protein pg/mg protein
Group A
Ex 14.8zk5.4 6.3k1.5 4.7kl.7
Con 15.0+5.6 5.421.5 4.6~11.6
Group B
17.3k5.8 5.4k1.6 4.5k1.3
Con 16.Ok6.6 5.3kO.9 4.9-tl.4
Values are means + SD; n = 4 for group A and 6 for group B.
exercised biceps; Con, control biceps.
3. L-[l-‘3C]leucine enrichment in biceps muscle
from control and exercised arms
Subj Control Exercised
2A 0.0060 0.0109
4A 0.0096 0.0104
5A 0.0104 0.0135
6A 0.0038 0.0153
1B 0.0060 0.0221
2B 0.0106 0.0196
3B 0.0106 0.0129
4B 0.0057 0.0188
5B 0.0072 0.0116
6B 0.0064 0.0115
Values are expressed as atom percent excess.
The purpose of this study was to determine the magni-
tude and time course for acute changes in MPS after an
isolated bout of heavy resistance exercise. Because of the
number of biopsies required, we considered it necessary
to examine two groups, each at a different time point
(rather than a single group at two time points). Our in-
terpretation of the time course data is thus based on the
assumption that postexercise changes in MPS would
have been similar for both groups. In an attempt to en-
sure this, groups were equated according to body size,
strength, and training history and performed identical
exercise protocols.
A second assumption is that plasma a-[13C]KIC label-
ing is a valid index of the precursor pool available for
MPS. Plasma cu-KIC labeling reflects the probable intra-
cellular fate of leucine and as such has been employed in
several studies for calculating rates of whole body and
MPS (2,6,7,15,16,21,22). Recent data have confirmed
that cu-KIC labeling closely approximates the labeling of
leucyl-tRNA in postabsorptive surgical patients
Measurement of labeled leucyl-tRNA was not attempted
in this study because of the large tissue requirements and
difficulty of isolation of this procedure.
Our finding that MPS was
50 (group A)
B) higher in the exercised biceps than in the con-
trol biceps indicates that the resistance exercise was a
potent stimulator of protein synthesis. Net muscle
$ 0.125.
t; 0.100-
7 0.075.
z 0.050-
a 0.025-
FIG. 2. Muscle protein synthetic rates in biceps of control and exer-
cised arms for groups A (4 h postexercise) and B (24 h postexercise).
Values are means t SD. * Significant difference (P < 0.05) between
FIG. 3. RNA activity in biceps muscle from control and exercised
arms for groups A and B. Values are means + SD. * Significant (P <
0.05) difference between arms.
growth (hypertrophy) can be considered as being the dif-
ference between the change in MPS and the change in
protein degradation. The extent to which protein degra-
dation also occurred as a result of the exercise is un-
known, but on the basis of data for animal muscle sub-
jected to stretch overload or tenotomy (9,
one can
assume it to have been significant. Moreover one can
calculate that if the increases in MPS that we found were
not also accompanied by a concomitant increase in pro-
tein degradation, in several weeks of training they would
result in increase in muscle size that greatly exceeds that
which is known to occur
The time course for increases in MPS in the biceps
brachii extended from
h postexercise. This is in
agreement with a model proposed by Booth et al.
suggesting that NIPS increases above basal levels
postexercise and remains elevated for an indefinite time
thereafter. In the present study the time required to
reach isotopic plateau and to allow labeled leucine to ac-
cumulate in the biceps precluded the assessment of IMPS
sooner than
h postexercise. It is possible that protein
synthetic rates were elevated before this time point, but
studies examining a shorter time course have not been
performed in humans. Tarnopolsky et al.
found no
change in WBPS rates in experienced bodybuilders
after the completion of a circuit-type resistance exercise
protocol. Because MPS accounts for 25-30s of WBPS
these results suggest that either MPS may have
been unaffected at this time or increases in MPS oc-
curred but were masked by larger decreases in protein
synthesis in other tissues. Our finding that MPS re-
mained elevated for up to
h postexercise is consistent
with findings of an elevated WBPS at this time point
after a single bout of circuit-type resistance exercise
MPS has been shown to be acutely elevated
h in rat gastrocnemius and tibialis anterior after a
single bout of concentric or eccentric resistance exercise,
respectively (30,
The duration of increases in MPS in humans after an
isolated bout of resistance exercise is not known. Vari-
ables that may affect this include the intensity and vol-
ume of the exercise, the muscle or muscle groups in-
volved, the type of muscle contractions performed, and
the state of training of the subject. There appears to be
an optimal training frequency of two or three per times
week for exercising a muscle group to ensure gains in
muscle mass (14,29). Less or more frequent training may
result in little or no muscle growth and suggests that the
time course for changes in MPS may be intimately asso-
ciated with training frequency and subsequent recovery
from exercise.
After the resistance exercise, there were wide interindi-
vidual differences for leucine enrichment in the control
and exercised arms (Table 3). The source of this varia-
tion is unknown, but it may be due to differences in
training history, differences in muscle fiber composition,
and/or the degree of muscle damage and satellite cell
activation. There is some evidence suggesting that the
basal rate of MPS is higher in type I than in type II
muscle fibers (8), although this has not been substan-
tiated by measurements of protein synthesis in humans
(15). Another possibility is that muscle damage of the
type associated with high-intensity eccentric muscle con-
tractions may have occurred in the exercised biceps.
Such damage may result in increased MPS through the
possible release of growth factor and subsequent satellite
cell activation (28).
To assess whether transcriptional and/or posttran-
scriptional events were responsible for the increases in
MPS, RNA capacity and activity were measured in both
exercised and control arms. RNA capacity expressed as
the total RNA content relative to noncollagenous protein
content (RNA concentration) can be considered an index
of changes in transcription (27). RNA activity expressed
as the amount of protein synthesized per unit time per
unit of RNA can be considered an index of how quickly
the ribosomal machinery can decode mRNA molecules
into protein (ribosomal efficiency) (27). RNA capacity
was unchanged in the exercised biceps of both groups,
but RNA activity was significantly elevated compared
with that in the unexercised biceps. These findings are
similar to those of previous studies that have examined
acute changes in RNA capacity and RNA activity after
stretch or weight-training protocols (10, 30, 31). It thus
appears that posttranscriptional events are important in
mediating acute changes in MPS in response to muscle
overload. The molecular signals, however, that stimulate
this enhanced rate of translation in response to resis-
tance exercise are presently unknown.
In summary, protein synthetic rates were elevated in
biceps muscle both at 4 and 24 h after a single unilateral
heavy resistance training session. An upregulation of
posttranscriptional events may be the mechanism that
initiates and maintains an acute increase in MPS after
resistance exercise.
The authors thank Stuart Phillips, John Moroz, and Joan Martin
for technical assistance.
This study was supported by the Natural Science and Engineering
Research Council of Canada. M. A. Tarnopolsky is funded by a Na-
tional Institute of Nutrition Post Doctoral Fellowship.
Present address of K. Smith: Dept. of Physiology, University of
Dundee, Dundee DDl 4HN, UK.
Address reprint requests to J. D. MacDougall.
Received 9 December 1991; accepted in final form 17 April 1992.
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... [5][6][7] Increasing plasma availability of EAAs by oral 8 or intravenous 9 supply, or by oral PRO intake 10 stimulates MPS. Resistance exercise in the fasted state can stimulate MPS alone 11 however, resistance exercise alongside hyperaminoacidaemia further stimulates MPS 12,13 and post resistance exercise PRO intake represents an important component of maximizing skeletal muscle adaptation to resistance exercise training. 14 The time course of this enhanced exercise-mediated sensitisation of PRO intake on MPS is poorly defined, but it is reported to be evident in trained participants 24 h after a single bout of resistance exercise 15 and up to 48 h 16 and 72 h 17 after resistance exercise in untrained subjects. ...
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Studies examining the effect of protein (PRO) feeding on post resistance exercise (RE) muscle protein synthesis (MPS) have primarily been performed in men, and little evidence is available regarding the quantity of PRO required to maximally stimulate MPS in trained women following repeated bouts of RE. We therefore quantified acute (4 h and 8 h) and extended (24 h) effects of two bouts of resistance exercise, alongside protein‐feeding, in women, and the PRO requirement to maximize MPS. Twenty‐four RE trained women (26.6 ± 0.7 years, mean ± SEM) performed two bouts of whole‐body RE (3 × 8 repetitions/maneuver at 75% 1‐repetition maximum) 4 h apart, with post‐exercise ingestion of 15 g, 30 g, or 60 g whey PRO (n = 8/group). Saliva, venous blood, and a vastus lateralis muscle biopsy were taken at 0 h, 4 h, 8 h, and 24 h post‐exercise. Plasma leucine and branched chain amino acids were quantified using gas chromatography mass spectrometry (GC–MS) after ingestion of D2O. Fifteen grams PRO did not alter plasma leucine concentration or myofibrillar synthetic rate (MyoFSR). Thirty and sixty grams PRO increased plasma leucine concentration above baseline (105.5 ± 5.3 μM; 120.2 ± 7.4 μM, respectively) at 4 h (151.5 ± 8.2 μM, p < 0.01; 224.8 ± 16.0 μM, p < 0.001, respectively) and 8 h (176.0 ± 7.3 μM, p < 0.001; 281.7 ± 21.6 μM, p < 0.001, respectively). Ingestion of 30 g PRO increased MyoFSR above baseline (0.068 ± 0.005%/h) from 0 to 4 h (0.140 ± 0.021%/h, p < 0.05), 0 to 8 h (0.121 ± 0.012%/h, p < 0.001), and 0 to 24 h (0.099 ± 0.011%/h, p < 0.01). Ingestion of 60 g PRO increased MyoFSR above baseline (0.063 ± 0.003%/h) from 0 to 4 h (0.109 ± 0.011%/h, p < 0.01), 0 to 8 h (0.093 ± 0.008%/h, p < 0.01), and 0 to 24 h (0.086 ± 0.006%/h, p < 0.01). Post‐exercise ingestion of 30 g or 60 g PRO, but not 15 g, acutely increased MyoFSR following two consecutive bouts of RE and extended the anabolic window over 24 h. There was no difference between the 30 g and 60 g responses.
... It is widely accepted that MPS increases in the post-exercise period (Chesley et al. 1992, Yarasheski et al. 1993, MacDougall et al. 1995 and continues (Dreyer et al. 2006) up to 48 h after exercise (Phillips et al. 1997 Other researchers have shown that the increased phosphorylation of mTOR and S6K1 in the post-exercise period can overcome the inhibitory effects of AMPK on eEF2 (Dreyer et al. 2006). In addition, Drummond et al. demonstrated that rapamycin administration before resistance exercise completely blocked eEF2 (Thr56) phosphorylation during post-exercise recovery, which indicated the influential role of mTORC1 in MSP (Drummond et al. 2009). ...
Skeletal muscle is a flexible and adaptable tissue that strongly responds to exercise training. The skeletal muscle responds to exercise by increasing muscle protein synthesis (MPS) when energy is available. One of protein synthesis’s major rate-limiting and critical regulatory steps is the translation elongation pathway. The process of translation elongation in skeletal muscle is highly regulated. It requires elongation factors that are intensely affected by various physiological stimuli such as exercise and the total available energy of cells. Studies have shown that exercise involves the elongation pathway by numerous signalling pathways. Since the elongation pathway, has been far less studied than the other translation steps, its comprehensive prospect and quantitative understanding remain in the dark. This study highlights the current understanding of the effect of exercise training on the translation elongation pathway focussing on the molecular factors affecting the pathway, including Ca²⁺, AMPK, PKA, mTORC1/P70S6K, MAPKs, and myostatin. We further discussed the mode and volume of exercise training intervention on the translation elongation pathway. • What is the topic of this review? This review summarises the impacts of exercise training on the translation elongation pathway in skeletal muscle focussing on eEF2 and eEF2K. • What advances does it highlight? This review highlights mechanisms and factors that profoundly influence the translation elongation pathway and argues that exercise might modulate the response. This review also combines the experimental observations focussing on the regulation of translation elongation during and after exercise. The findings widen our horizon to the notion of mechanisms involved in muscle protein synthesis (MPS) through translation elongation response to exercise training.
... It is known that the body wall muscles, after initial development in the embryo, increase drastically in size (~25-40-fold increase in area) by hypertrophic growth, as the development proceeds from the L1 to L3 stage [52]. The myofibrillar-contractile proteins form a major portion of the dry weight of muscles, and an increase in muscle size is due to an increase in the contractile protein content [53]. We found that the expression of transcripts coding for a few major sarcomeric structural Table S1), with different reverse primers, either RPShSp (no. 12 in Table S1) for the endogenous transcript, or Fab1 (no 49 in Table S1) proteins, particularly thin filament proteins, was significantly reduced in Mlp60A null homozygotes (Fig. 7). ...
Many myofibrillar proteins undergo isoform switching in a spatio-temporal manner during muscle development. The biological significance of the variants of several of these myofibrillar proteins remains elusive. One such myofibrillar protein, the Muscle LIM Protein (MLP), is a vital component of the Z-discs. In this paper, we show that one of the Drosophila MLP encoding genes, Mlp60A, gives rise to two isoforms: a short (279 bp, 10 kDa) and a long (1461 bp, 54 kDa) one. The short isoform is expressed throughout development, but the long isoform is adult-specific, being the dominant of the two isoforms in the indirect flight muscles (IFMs). A concomitant, muscle-specific knockdown of both isoforms leads to partial developmental lethality, with most of the surviving flies being flight defective. A global loss of both isoforms in a Mlp60A-null background also leads to developmental lethality, with muscle defects in the individuals that survive to the third instar larval stage. This lethality could be rescued partially by a muscle-specific overexpression of the short isoform. Genetic perturbation of only the long isoform, through a P-element insertion in the long isoform-specific coding sequence, leads to defective flight, in around 90% of the flies. This phenotype was completely rescued when the P-element insertion was precisely excised from the locus. Hence, our data show that the two Mlp60A isoforms are functionally specialized: the short isoform being essential for normal embryonic muscle development and the long isoform being necessary for normal adult flight muscle function.
Mechanisms underlying mechanical overload-induced skeletal muscle hypertrophy have been extensively researched since the landmark report by Morpurgo (1897) of "work-induced hypertrophy" in dogs that were treadmill-trained. Much of the pre-clinical rodent and human resistance training research to date supports that involved mechanisms include enhanced mammalian/mechanistic target of rapamycin complex 1 (mTORC1) signaling, an expansion in translational capacity through ribosome biogenesis, increased satellite cell abundance and myonuclear accretion, and post-exercise elevations in muscle protein synthesis rates. However, several lines of past and emerging evidence suggest additional mechanisms that feed into or are independent of these processes are also involved. This review will first provide a historical account as to how mechanistic research into skeletal muscle hypertrophy has progressed. A comprehensive list of mechanisms associated with skeletal muscle hypertrophy is then outlined and areas of disagreement involving these mechanisms are presented. Finally, future research directions involving many of the discussed mechanisms will be proposed.
Introduction: Protein ingestion during recovery from exercise has been reported to augment myofibrillar protein synthesis rates, without increasing muscle connective protein synthesis rates. It has been suggested that collagen protein may be effective in stimulating muscle connective protein synthesis. The present study assessed the capacity of both whey and collagen protein ingestion to stimulate post-exercise myofibrillar and muscle connective protein synthesis rates. Methods: In a randomized, double-blind, parallel design, 45 young male (n = 30) and female (n = 15) recreational athletes (age: 25 ± 4 y; BMI: 24.1 ± 2.0 kg/m2) were selected to receive primed continuous intravenous infusions with L-[ring-13C6]-phenylalanine and L-[3,5-2H2]-tyrosine. Following a single session of resistance type exercise, subjects were randomly allocated to one of three groups ingesting either 30 g whey protein (WHEY, n = 15), 30 g collagen protein (COLL, n = 15) or a non-caloric placebo (PLA, n = 15). Blood and muscle biopsy samples were collected over a subsequent 5-hour recovery period to assess both myofibrillar and muscle connective protein synthesis rates. Results: Protein ingestion increased circulating plasma amino acid concentrations (P < 0.05). The post-prandial rise in plasma leucine and essential amino acid concentrations was greater in WHEY compared with COLL, whereas plasma glycine and proline concentrations increased more in COLL compared with WHEY (P < 0.05). Myofibrillar protein synthesis rates averaged 0.041 ± 0.010, 0.036 ± 0.010 and 0.032 ± 0.007 %/h in WHEY, COLL and PLA, respectively, with only WHEY resulting in higher rates when compared with PLA (P < 0.05). Muscle connective protein synthesis rates averaged 0.072 ± 0.019, 0.068 ± 0.017, and 0.058 ± 0.018 %/h in WHEY, COLL and PLA, respectively, with no significant differences between groups (P = 0.09). Conclusions: Ingestion of whey protein during recovery from exercise increases myofibrillar protein synthesis rates. Neither collagen nor whey protein ingestion further increased muscle connective protein synthesis rates during the early stages of post-exercise recovery in both male and female recreational athletes.
Athletes should follow these rules in order to optimize their nutrition. Eat enough calories to offset energy expenditure (typically 50–80 kcal/kg/day). Consume the proper amount of carbohydrate (e.g., 5–8 g/kg/day during normal training and 8–10 g/kg/day during heavy training), protein (1.2–2.0 g/kg/day), and fat (0.5–1.5 g/kg/day). Ingest meals and snacks at appropriate time intervals prior to, during, and/or following exercise in order to provide energy as well as to promote recovery following exercise; include more liquid and quickly digestible type forms of nutrition within an hour of exercise; Ensure athletes are properly hydrated prior to exercise and competition. Incorporate rest and nutritional strategies to optimize recovery. Only consider using nutritional supplements that have been found to be an effective and safe means for improving performance capacity and/or enhancing recovery.KeywordsAthletic dietSports nutritionErgogenic aidsNutrient timing
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Çok faktörlü bir metabolik bozukluk olan Tip 2 diyabet, dünya çapında artan prevalansı ile küresel salgın halini almıştır. Yüksek kan şekeri, insülin eksikliği ve insülin direnci ile karakterize bir hastalıktır. Genetik ve çevresel faktörlerin etken olduğu Tip 2 diyabet, yaş, obezite, sedanter yaşam tarzı ve yüksek enerji alımı ile ilişkilendirilmektedir. Tip 2 diyabet hastalarında, insülin salınımı yetersiz, glukoz homeostazı bozulmuş durumdadır. Bu diyabet türü, serbest radikallerin artmasına, antioksidan azalmasına ve oksidatif stresin tetiklenmesine neden olmaktadır. Egzersiz, Tip 2 diyabette yaşanan süreçleri kontrol altına alabilen non-farmakolojik yöntem olarak kabul edilir. Farklı şiddetlerde yapılan aerobik egzersizlerin, Tip 2 diyabet göstergelerinde iyileşmelere neden olduğu bilinmektedir. Ayrıca, düzenli yapılan egzersizler, antioksidan kapasiteyi geliştirerek, reaktif oksijen türlerinin neden olduğu oksidatif hasarı azaltabilmektedir. Derleme türünde tasarlanmış bu çalışmada, farklı varyasyonlarda uygulanan interval antrenman yönteminin Tip 2 diyabet hastalığı üzerindeki etkileri incelenmiştir. Sonuç olarak, interval antrenmanların, zaman ekonomisi, fizyolojik fonksiyonların iyileşmesi ve gelişimi bakımından, uzun süreli devamlı egzersizlere nazaran daha etkili olduğu bilinmektedir. Bu çalışmada, belirtilen etkilerin Tip 2 diyabetli hastalar için de geçerli ve önemli olduğu belirlenmiştir. Özellikle yüksek şiddetli interval antrenmanların (HIIT), hastalara bedenen getireceği yük ve kontrendikasyonlar düşünülerek, gözlem altında, doğru bir şekilde planlandığında; etkili, alternatif bir egzersiz protokolü olduğu belirlenmiştir.
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Use of a bared sunerficial hand vein as an alternative site for the mea
  • N N Abumrad
  • D Rabin
  • M P Diamond
  • W W Lacy
ABUMRAD, N. N., D. RABIN, M. P. DIAMOND, AND W. W. LACY. Use of a bared sunerficial hand vein as an alternative site for the mea-