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The Time Course for Elevated Muscle Protein Synthesis Following Heavy Resistance Exercise

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Abstract

It has been shown that muscle protein synthetic rate (MPS) is elevated in humans by 50% at 4 hrs following a bout of heavy resistance training, and by 109% at 24 hrs following training. This study further examined the time course for elevated muscle protein synthesis by examining its rate at 36 hrs following a training session. Six healthy young men performed 12 sets of 6- to 12-RM elbow flexion exercises with one arm while the opposite arm served as a control. MPS was calculated from the in vivo rate of incorporation of L-[1,2-13C2] leucine into biceps brachii of both arms using the primed constant infusion technique over 11 hrs. At an average time of 36 hrs postexercise, MPS in the exercised arm had returned to within 14% of the control arm value, the difference being nonsignificant. It is concluded that following a bout of heavy resistance training, MPS increases rapidly, is more than double at 24 hrs, and thereafter declines rapidly so that at 36 hrs it has almost returned to baseline.
RAPID COMMUNICATION
The Time Course for Elevated Muscle Protein
Synthesis Following Heavy Resistance Exercise
J. Duncan MacDougall, Martin J. Gibala, Mark
A.
Tarnopolsky,
Jay
R.
MacDonald, Stephen
A.
Interisano, and Kevin
E.
Yarasheski
Catalogue Data
MacDougall, J.D., Gibala, M.J., Tarnopolsky, M.A., MacDonald, J.R., Interisano, S.A.,
and Yarasheski, K.E. (1995). The time course for elevated muscle protein synthesis
following heavy resistance exercise.
Can.
J.
Appl. Physiol.
20(4): 480-486.
O
1995
Canadian Society for Exercise Physiology.
Key
words:
L-[-I3C] leucine, muscle hypertrophy, training frequency, mass spectrometry
Mots-cle's:
leucine L-[-I3C], hypertrophie musculaire, frhquence d'entrainement, spec-
tromPtre de masse
It has been shown that muscle protein synthetic rate (MPS) is elevated in humans by 50%
at 4 hrs following a bout of heavy resistance training, and by 109% at 24 hrs following
training. This study further examined the time course for elevated muscle protein synthesis
by examining its rate at
36
hrs following a training session. Six healthy young men
performed 12 sets of
6-
to 12-RM elbow flexion exercises with one arm while the opposite
arm served as a control. MPS was calculated from the in vivo rate of incorporation of
L-[l ,2-13C2] leucine into biceps brachii of both arms using the primed constant infusion
technique over 11 hrs. At an average time of
36
hrs postexercise, MPS in the exercised arm
had returned to within 14% of the control arm value, the
diflerence being nonsigniJicant. It
is concluded that following a bout of heavy resistance training, MPS increases rapidly,
is more than double at 24 hrs, and thereafter declines rapidly so that at
36
hrs it has
almost returned to baseline.
On a dhja montrh que
le taux de synthbe de prothine musculaire (SPM) est hlevh duns
l'homme de 50% a 4 h apris une seance d'entrainement et de 109% a 24 h apt-t?s
l'entrainement. La prhsente htude continue l'examen du c-ours temporel de la synthese
MacDougall, Gibala, Tarnopolsky, MacDonald, and Interisano: Department of
Kinesiology,
McMaster University, Hamilton, Ontario L8S 4Kl; Yarasheski: Metabolism
Division, Washington University School of Medicine, St. Louis, MO 631 10, USA.
Can. J. Appl. Physiol. 1995.20:480-486.
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Protein Synthesis Following Exercise
48
1
klevke de protkine en examinant le faux
h
36 h aprts une skance d'entrainement. Six
jeunes hommes en bonne
santt! ont effectut! un total de 12 skries de 6- 12-RM d'exercices
de flexion du coude avec un
seul bras, l'autre agissant comme tkmoin. Nous avons calcuM
la SPM
a
partir de l'enrichissement du leucine L-[l ,2-'3C2] duns des biopsies du biceps
brachii
prilevkes des deux bras en employant la technique d'infusion constant amorck
pendant
11 h.
A
36 h en moyen aprts I'entrainement, la SPM du bras travaillk s'ktait
rendue jusqu'a moins de 14% de la valeur du bras tkmoin, la divergence e'tant non
significative. On conclut que la SPM accroit rapidement
aprts une skance d'entrainement
de
rbistance lourde, qu'elle atteint sa valeur
rl
24 h, et qu'elle dkcroit rapidement
subskquemment, regagnant a peu
prts sa valeur initiale
a
36 h.
Introduction
We have previously shown that the biceps brachii mixed muscle protein synthetic
rate (MPS) is elevated in experienced weight trainers by 50% approximately
4 hrs after training, and by 109% approximately 24 hrs after training (Chesley
et al., 1992;
MacDougall et al., 1992). The present study further investigated the
time course for elevated protein synthesis by examining its rate at approximately
36 hrs following a training session.
Methods
As in our previous study (Chesley et al., 1992), MPS was measured in biceps
brachii following an acute bout of heavy resistance exercise by the elbow flexors
of one arm so that the opposite arm served as a control. Since the duration that
protein synthesis might remain elevated in the exercised arm was unknown, our
original plan was to examine MPS 36 hrs following training and then at subsequent
12-hr intervals until MPS returned to that of the control arm.
SUBJECTS AND DESIGN
Six healthy young men (23
f
1.7 yrs) who regularly engaged in heavy resistance
(bodybuilding) training served as subjects. They did not differ from our previous
subjects as to age, height, body weight, or training experience. They were advised
of the risks associated with the study, in accordance with the university's human
ethics committee, and provided written informed consent.
Subjects refrained from resistance exercise training for 3 days. At approxi-
mately 7 p.m. on the evening of the 4th day, they performed a typical training
session for the elbow flexors of one randomly chosen arm. As in our previous
study, the session was supervised by a coinvestigator and consisted of 4 sets of
single arm biceps, concentration and preacher curls at 80% of maximum
(
I
-RM)
so that a total of 12 sets was completed in all. Each set was undertaken to
muscular "failure" and a rest period of 3 to 4 min was provided between sets.
The young men were instructed to consume their normal breakfast and lunch the
following day and to report back to the laboratory at 5 p.m. to consume a standard
meal. The energy content of the meal was 1,200 Kcal and consisted of 70%
carbohydrate, 16% protein, and 14% fat. Two hours later a 20-Ga catheter was
inserted into a hand vein for blood sampling and a second catheter was positioned
in a contralateral forearm vein for isotope tracer infusion. Subjects read or watched
Can. J. Appl. Physiol. 1995.20:480-486.
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482 MacDougall, Gibala, Tarnopolsky, et al.
movies until their normal bedtime and slept in the laboratory overnight. The rate
of tracer incorporation into biceps brachii was measured in both arms between
8 p.m. that night and 7 a.m. the following morning so that the midpoint would
be
36
hrs after their previous training session.
MEASUREMENT PROCEDURES
The in vivo rate of MPS was determined from the enrichment of L-[1,2-"C2]
leucine in biopsy samples using an 1 1-hr primed constant intravenous infusion. A
priming dose of
L-[l ,2-I3C2] leucine (>99% isotopic purity, Tracer Technologies,
Somerville, MA) was administered (7.58
pmol
.
kg-'), followed by a constant
infusion (7.58
pmol
.
kg-'
.
h-I) for 12.5 hrs using a Harvard syringe pump.
Arterialized blood samples (hot box at 65°C) were taken prior to infusion and
at 1.5, 10.5, 11.5, 12, and 12.5 hrs for determination of plasma
[1,2-I3C2]
-
a-ketoisocaproic acid (a-KIC). Needle biopsies were taken from biceps brachii
of both arms 90 min following the priming dose and 11 hrs later.
Enrichment of plasma
[l ,2-l3C2]
-
a-KIC (atom
%
excess) was determined
by electron impact ionization gas chromatography-mass spectrometry
(Hewlett-
Packard 5980A-MSD), as has been previously described (Tarnopolsky et al.,
1991). Enrichment of muscle
[I ,2-"C2] leucine (mole
%
excess) was determined
by capillary gas
chromatography/combustion
isotope-ratio mass spectroscopy as
described by Yarasheski et al. (1992). MPS was calculated for each sample
according to the method of Nair et al. (1988) using plasma
[1,2-'"2]
-
a-KIC
as the precursor pool enrichment, as we have previously detailed (MacDougall
et al., 1992). Data are expressed as
%
.
hr-I, where the incorporation time is the
time between biopsies for each subject. Differences in MPS between control and
exercised arms and possible changes in plasma [l,2-13C2]
-
a-KIC during the
infusion procedure were assessed by analysis of variance.
Results
Enrichment for plasma [l,2-'3C2]
-
a-KIC at each sampling time is shown in
Table 1. Each sample was analyzed in duplicate and the intra-assay coefficient
of variation was 0.82%. Although there was a tendency for enrichments to decline
slightly toward the end of the infusion period, this was not statistically significant.
Plasma enrichments were remarkably consistent between the 1.5- and 10.5-hr
Table
1
Plasma
[1,2-13C2]
-
a-KIC
Enrichment (atom
%
excess)
Sampling time
1.5 hrs 10.5 hrs
1
1.5 hrs 12.0 hrs 12.5 hrs
Note.
N
=
6.
Differences are not statistically significant.
Can. J. Appl. Physiol. 1995.20:480-486.
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Protein Synthesis Following Exercise 483
points, which represented the major portion of the time (9 1
%)
over which MPS
was measured.
MPS for both control and exercised arms are illustrated in Figure 1. Dupli-
cate analysis for enrichment of muscle protein
[
1
,2-"C2] leucine were performed
on each sample and the intra-assay coefficient of variation was 2.66%. Although
MPS was approximately 14% higher in the exercised arm than in the control
arm, this difference was not statistically significant.
MPS in the control arms (0.0408
f0.0103% hr-2) was similar to the mean
value of 0.0538
(f0.0148%
hr-I) which we found in the control arms in our
previous study (Chesley et al., 1992). The results of the present study have been
combined with our previous data to illustrate MPS at 4, 24, and 36 hrs following
exercise (Figure 2).
Discussion
Combined data from the subjects in the present study and from the two groups
in our previous study indicate that biceps brachii MPS is elevated by 50, 109,
and 14% at 4, 24, and 36 hrs, respectively, following a bout of heavy resistance
training (Figure 2). Although a single within-group design at the three time points
would have been preferable, we rejected it on ethical grounds because it would
have required a total of six biopsies from biceps of each
arm.
We are aware of
the limitations of a between-group design, and for this reason took care to match
our three groups according to age, body size, and training background; we had
them perform the identical exercises at the same volume and intensity.
CONTROL EXERCISED
ARM ARM
Figure
1.
Rate of muscle protein synthesis in biceps brachii for the control and exer-
cised arms 36 hrs after resistance training.
N
=
6, values are means
SE.
The differ-
ence between both arms was not statistically significant.
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484
MacDougall, Gibala, Tarnopolsky, et al.
HRS. POST EXERCISE
Figure
2.
Increase in muscle protein synthetic rate
4, 24,
and
36
hrs after a single re-
sistance training bout. Values indicate the difference between MPS in the exercised
and control arm. Data at
4
and
24
hrs are from a previous study (see text). "Significant
at
p
<
0.05.
The method for measuring MPS was modified somewhat from our previous
approach in that we infused doubly labeled
(L-[l ,2-'VC,]) leucine and maintained
the constant infusion over 12.5 hrs instead of singly labeled
(L-[I-'"]) leucine
over 6 hrs. Our finding in the present study, that MPS in the control
arm
was
similar to control arm values in the previous study, indicates that the two methods
yield similar results. Moreover, since it is the
diference
in MPS between the
exercised and nonexercised arms that indicates an elevated muscle protein synthe-
sis, possible methodological differences have been controlled for.
It should be recognized that the values reported for MPS at 4 and 24 hrs
represent the average values over the 4 hrs during which MPS was measured.
Similarly, the 36-hr value is the average value over 11 hrs
(i.e., between 30.5
and 41.5 hrs after exercise). The assumption in presenting these data at a single
time point is that MPS is linear over the assessment period. This may not of
course be the case. We interpret our finding-that at 36 hrs, MPS in the exercised
arm was not significantly higher than in the control arm (in 4 subjects it was
higher but in 2 subjects it was not)-as indicating that, at this point, MPS was
already returning to its preexercise rate. The relatively large standard error at
this point probably reflects interindividual differences in the rate at which addi-
tional protein synthesis is completed after training. In addition, since MPS at
this point in time was not significantly elevated, we decided that further investiga-
tion at, say, 48 hrs was unnecessary.
Since the elevated MPS following heavy resistance exercise occurs in the
absence of an elevation in
RNA
concentration (Chesley et al., 1992), its up-
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Background Increased protein intake is suggested as a strategy to slow or reverse the loss of muscle mass and strength observed in sarcopenia, but results from studies that directly tested this possibility have been inconsistent. Objectives We assessed the evidence on the effects of whole protein supplementation or higher-protein diets, without the use of amino acids or supplements known to stimulate hypertrophy, alone or in combination with resistance exercise (RE) interventions, on lean body mass (LBM) and strength in older adults. Design A systematic search was conducted using PubMed, Medline, Web of Science and Cochrane CENTRAL databases from January 1990 up to July 2021. Randomized controlled trials that assessed the effects of protein supplementation and/or higher-protein dietary interventions in older adults (mean age ≥ 50 years), on total LBM, appendicular lean mass (ALM), handgrip (HG) and knee extension strength (KE) were included. Results 28 studies were identified. In pooled analysis, compared with lower protein controls, protein supplementation did not have a significant positive effect on total LBM [weighted mean difference in change (WMD):0.34, 95% CI: –0.21,0.89, I2:90.01%], ALM [WMD:0.4, 95% CI: –0.01,0.81, I2:90.38%], HG [WMD:0.69, 95% CI: –0.69,2.06, I2:94.52%] or KE [WMD:1.88, 95% CI: –0.6,4.35, I2:95.35%]. However, in interventions that used also RE, statistically significant positive effects of protein were observed for ALM [WMD:0.54, 95% CI:0.03,1.05, I2:89.76%] and HG [WMD:1.71, 95% CI:0.12,3.30, I2:88.71%]. Meta-regression revealed no significant association between age, per-meal protein dose, duration, and baseline protein intake with change in any outcome. Sub-group analysis revealed the statistically significant effects on ALM only occurred in sarcopenic/frail populations (WMD:0.88, 95% CI:0.51,1.25, I2:79.0%). Most studies (n = 22) had some risk of bias. Conclusions In older adults performing RE, increased protein intake leads to greater ALM and HG, compared with lower protein controls. Without RE, protein has no additional benefit on changes in total LBM, ALM or HG.
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