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Endogenous Anabolic Hormonal and Growth Factor Responses to Heavy Resistance Exercise in Males and Females


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To examine endogenous anabolic hormonal responses to two different types of heavy resistance exercise protocols (HREPs), eight male and eight female subjects performed two randomly assigned protocols (i.e. P-1 and P-2) on separate days. Each protocol consisted of eight identically ordered exercises carefully designed to control for load, rest period length, and total work (J) effects. P-1 utilized a 5 RM load, 3-min rest periods and had lower total work than P-2. P-2 utilized a 10 RM load, 1-min rest periods and had a higher total work than P-1. Whole blood lactate and serum glucose, human growth hormone (hGH), testosterone (T), and somatomedin-C [SM-C] (i.e. insulin-like growth factor 1, IGF-1) were determined pre-exercise, mid-exercise (i.e. after 4 of the 8 exercises), and at 0, 5, 15, 30, and 60 min post-exercise. Males demonstrated significant (p less than 0.05) increases above rest in serum T values, and all serum concentrations were greater than corresponding female values. Growth hormone increases in both males and females following the P-2 HREP were significantly greater at all time points than corresponding P-1 values. Females exhibited significantly higher pre-exercise hGH levels compared to males. The P-1 exercise protocol did not result in any hGH increases in females. SM-C demonstrated random significant increases above rest in both males and females in response to both HREPs.(ABSTRACT TRUNCATED AT 250 WORDS)
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Endogenous Anabolic Hormonal and Growth Factor Responses
to Heavy Resistance Exercise in Males and Females
W. I Kraemer2, S. E. Gordon2, S.f. Fleck4, L. J. Marchitelli1 , R. Mello1, f. E. Dziados1 , K. Friedl1 , E. Harman1,
C. Maresh3, A. C. Fry2
Physiology Division, U. S. Army Research Institute of Environmental Medicine, Natick, MA 01760-5007,
2Center for Sports Medicine, The Pennsylvania State University, University Park, PA 16802, 3Exercise Science Program and
the Department of Physiology and Neurobiology, The University of Connecticut, Storrs, CT 06259, 4Sport Science Program,
U. S. Olympic Committee, Colorado Springs, CO 80909 USA
W. J. Kraemer, S. E. Gordon, S. J. Fleck, L. J.
Marchiteii, R. Mello, J. E. Dziados, K. Friedl, E. Harman, C.
Maresh and A. C. Fry, Endogenous Anabolic Hormonal and
Growth Factor Responses to Heavy Resistance Exercise in
Males and Females. mt J Sports Med, Vol 12, No 2, pp 228—
235, 1991.
Accepted: June 20, 1990
To examine endogenous anabolic hormonal re-
sponses to two different types of heavy resistance exercise
protocols (HREPs), eight male and eight female subjects per-
formed two randomly assigned protocols (i. e. P-i and P-2)
on separate days. Each protocol consisted of eight identically
ordered exercises carefully designed to control for load, rest
period length, and total work (J) effects. P-l utilized a 5 RM
load, 3-mm rest periods and had lower total work than P-2. P-
2 utilized a 10 RM load, 1-mm rest periods and had a higher
total work than P-i. Whole blood lactate and serum glucose,
human growth hormone (hGH), testosterone (T), and soma-
tomedin-C (SM-C] (i. e. insulin-like growth factor 1, IGF-l)
were determined pre-exercise, mid-exercise (i. e. after 4 of the
8 exercises), and at 0, 5, 15, 30, and 60 mm post-exercise.
Males demonstrated significant (p <0.05) increases above
rest in serum T values, and all serum concentrations were
greater than corresponding female values. Growth hormone
increases in both males and females following the P-2 HREP
were significantly greater at all timepoints than correspond-
ing P-i values. Females exhibited significantly higher pre-ex-
ercise hGH levels compared to males. The P-i exercise proto-
col did not result in any hGH increases in females. SM-C de-
monstrated random significant increases above rest in both
males and females in response to both HREPs. These data
suggest that the hormonal response patterns to HREPs are
variable and in females differ from those in males due to sig-
nificantly higher pre-exercise and exercise-induced serum T
levels in males and higher pre-exercise serum hGH concen-
trations in females.
Key words
Growth hormone, insulin-like growth factor 1,
testosterone, anaerobic exercise, somatomedins, resistance
exercise, blood lactate
Heavy resistance exercise is a potent exercise
stimulus for muscle tissue hypertrophy and strength develop-
ment (22, 27). The differences observed between males and
females have classically been attributed to the higher concen-
trations of testosterone in males (13). Still, females generally
demonstrate similar relative training responses in muscular
strength (2). Furthermore, the relative changes in cross-
sectional area, reflecting cellular hypertrophy, are com-
parable (7, 27, 28). The responses in serum testosterone to re-
sistance exercise in females have been examined, but the re-
sponses of other trophic hormones such as growth hormone
and somatomedin C (insulin-like growth factor 1) have not
been previously reported (11, 18, 31, 32). The purpose of this
investigation was to examine the acute response patterns of
several musculotrophic factors (i. e. serum testosterone,
growth hormone and somatomedin-C) to heavy resistance ex-
ercise, compared between males and females. These responses
were further explored by comparison of two distinctly differ-
ent heavy resistance exercise protocols, one with longer rest
and heavier weight (P-I), which is typically used to increase
strength, muscle hypertrophy, and one with more repetitions
and shorter rest periods (P-2), which is typically used to im-
prove muscular strength, hypertrophy, and high intensity
muscular endurance (19).
Int.J.SportsMed. 12(1991)228—235
GeorgThieme Verlag StuttgartNewYork
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Endogenous Anabolic Hormonal and Growth Factor Responses to Heavy Resistance mt. J. Sports Med. 12(1991) 229
Eight male and eight female subjects gave writ-
ten informed consent to participate in this investigation. The
physical characteristics of the subjects were (51 1 SD): age
(yrs), males, 24.7 4.5, females, 23.1 3.3; height (cm),
males, 178.5±8.2, females 161.6±8.1; body mass (kg),
males, 82.1 12.1, females, 60.4±4.46; body fat (%), males,
16.1 4.5, females, 28.5±6.1. All subjects had recreational
experience with resistance training but none were competitive
lifters. All subjects were healthy and none were using medica-
tions. Each subject denied any history of anabolic steroid use.
All females were determined to be eumenorrheic according to
methods previously described (8) and as defined by regular
28—32 day menstrual cycles over the previous year. None of
the females had used oral contraceptives or an intrauterine
device within the past year (8). A minimum of two weeks were
utilized for experimental protocol familiarization, descriptive
testing, and load verifications (5 RM and 10 RM) for each ex-
perimental exercise protocol. Determination of each subject's
percent body fat using hydrostatic weighing (computer inter-
faced with a load cell) and standard body composition
methodology as previously described (12, 33) was also accom-
plished during this time.
During the preliminary testing period, one rep-
etition maximum (1 RM) testing was performed for each lift
with a warm-up of 5—10 repetitions at 40—60% of the perceived
maximum. After a 1-mm rest and stretching, 3—5 repetitions
were performed with 60—80% of the perceived maximum.
Three to four subsequent attempts were then made to deter-
mine the 1 RM with 3—5 minutes rest between lifts. The test-re-
test reliability for each of the lifts was between 0.91 and 0.95. A
complete range of motion and proper technique were required
for each successful 1 RM trial. No injuries were observed in
any of the testing. No I RM determinations were made for the
sit-up exercise as only the 5 RM and 10 RM loads were deter-
mined for use in the experimental protocol.
The two distinctly different heavy resistance
exercise protocols (HREPs) were performed in random order.
Each experimental test was performed at the same time of day
on separate days with a minimum of 72 hours rest between ex-
perimental sessions. The experimental design of each protocol
is shown in Table 1. The P-I exercise protocol was a five repeti-
tion maximum (5 RM) based workout which incorporated
longer rest intervals (i. e. three minutes) and heavier weight (5
RM) lifted. The P-2 exercise protocol was a 10 RM based
workout with one minute rest between sets. As heavy re-
sistance exercise protocols, both routines produce increases in
muscular strength and hypertrophy. The P- 1 protocol is one
typically utilized for "strength" training, while the P-2 proto-
col is typically used by serious resistance trainees for the
development of strength, hypertrophy, and high intensity
muscular endurance (19). The same order of exercise was used
in both HREPs. P-2 workouts for both male and females con-
sisted of significantly (p <0.05) greater total work (J): males
P-l, 49,980 10,473.9, P-2, 60,427.3 13,428.8; females P-
1, 24,501.1 2,827.0, P-2, 31,580.3± 3,278. Understand-
ably, total work for the females in both P- 1 and P-2 was signifi-
cantly less than that of the male subjects. Still, the relative loads
(% 1 RM) utilized were not significantly different between
males and females in any of the lifts performed. Depending
Table 1 Experimental heavy resistance exercise protocols
Exercise order Repetition maxim
number of sets
urn (RM) and
1. Bench press 5 RM x 5 sets 10 RM x 3 sets
2. Double leg extensions 5 RM x 5 sets 10 RM x 3 sets
3. Military press 5 RM x 3 sets 10 RM x 3 sets
4. Bent leg incline
sit-ups 5 RM x 3 sets 10 RM x 3 sets
5. Seated rows 5 AM x 3 sets 10 RM x 3 sets
6. Latpull down 5 RM x 4sets 10 RM x 3 sets
7. Arm curls 5 RM x 3 sets 10 RM x 3 sets
8. Leg press 5 AM x 5 sets 10 RM x 3 sets
P-1 used 5 AM load and 3-mm rest periods, P-2 used 10 RM load and
1-mm rest periods;
* Exercises 4 and 7 were performed using free weights, all other exer-
cises were performed using a Universal weight machine.
uponthe exercise, the 5 RM represented a range of 80—95% of
the 1 RM, and the 10 RM represented a range of 70—85% of the
All exercises were structured proportionally
for each subject with grip widths and positions marked and
kept constant for each exercise. Each workout was designed to
provide the same relative exercise stress for comparative pur-
poses. Lifting work was calculated as weight X vertical dis-
tance moved per repetition X number of repetitions. The com-
puter program took into consideration the vertical distance
moved of both the iron plates and the centers of gravity of the
lifter's body segments. These distances were obtained from
measurements on the subjects and equipment when they were
in the starting and ending exercise positions. Anthropometric
tables were used to locate body segment centers of gravity and
to estimate the body segment weights from total body weight
All subjects refrained from ingestion of alco-
hol or caffeine for 24 hrs prior to testing. Dietry analysis
(Nutri-Calc, PCD System, Inc., Penn Yan, NY) for the 3 days
prior to each experimental session was obtained from a food
diary and demonstrated normal RDA caloric, nutrient, vi-
tamin, and mineral intakes. Values were: (mean I SD)
62.1 4.6% carbohydrate, 12.3 protein, and
25.6 5.3% fat. While it was not the purpose of the study to
match diets on each test day, similar caloric, vitamin, mineral,
and nutrient intakes were observed prior to each test. Urine
nitrogen determinations verified that all subjects were within
the normal range for positive nitrogen balance prior to each
test session. Experimental testing of the female subjects was
timed to the early follicular phase (2—4 days after the onset of
menses) (8).
Subjects reported for the experimental session
and venous blood samples were obtained in a semi-recumbant
position, which was used for all samples. Testing was started in
the morning (8—10 a. m.) and each subject was tested at the
same time of day to reduce the effects of any diurnal variations
on the hormonal concentrations. The venous blood samples
were obtained from an indwelling 20 gauge teflon (3.75 cm)
cannula placed in a superficial arm vein on the radial aspect of
the arm. The teflon cannula was kept patent with a continuous
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* = p <0.05 from corresponding pre-exercise value;
a = p < 0.05from corresponding P-i workout;
b = p <0.05 from corresponding female value.
flow of isotonic saline (30 mlhr 5.Priorto obtaining a rest-
ing blood sample, a 20-mm equilibration period was utilized.
Subjects knew they would not immediately start to exercise
after the resting blood sample was obtained. The exercise pro-
tocol started 10 mm after the resting blood sample had been
obtained. This procedure was shown during pilot testing to
eliminate any significant anticipatory increases in hormonal
responses previously thought to affect the examination of ex-
ercise responses (6). Water intake was allowed ad libitum
throughout the exercise protocols and recovery. Blood
samples were obtained pre-exercise, mid-exercise (i. e. after 4
exercises) and at 0 (immediately post), 5, 15, 30, and 60 mm
following each exercise protocol. All blood samples were
processed, centrifuged for 15 minutes at 3000 x g, serum
harvested, and stored at — 120 °C until analyzed.
Fresh blood samples were immediately ana-
lyzed in duplicate for whole blood lactate by an enzymatic-
amperometric method (Lactate Analyzer-640, Wolverine
Med Inc. Inc., Grand Rapids, MI). Serum samples were as-
sayed for glucose concentrations by an automated glucose oxi-
dase reaction (23-Glucose Analyzer, Yellow Springs, Inc.,
Yellow Springs, OH). Blood was analyzed in triplicate for
hemoglobin using the cyanmethemoglobin method (Sigma
Chemical Co., St. Louis, MO) and for hematocrit by micro-
capillary technique. Relative percent changes in plasma
volume were calculated according to equations by Dill and
Costill (9).
Serum testosterone (T), human growth hor-
mone (hGH), and somatomedin-C (SM-C) (i. e. insulin-like
growth factor, IGF-l) concentrations were determined in du-
plicate blinded analyses by radioimmunoassay (RIA). Male
and female RIAs for T were performed in different assays to
allow for appropriate sensitivity adjustments of the standard
curves. Determinations of different serum immunoreactivity
values were accomplished with the use of a Beckman 5500
gamma counter and on-line data reduction system. Serum
samples were analyzed in duplicate for T using an 125j solid
phase radioimmunoassay (Diagnostic Products Corp., Los
Angeles, CA), which was sensitive to a detection limit of 0.38
nmoll Intra- and inter-assay variances were calculated to
be less than 3.6% and 4.7%, respectively, with a 3.3% crossre-
activity with dihydrotestosterone. Serum samples were ana-
lyzed in duplicate for human growth hormone utilizing an 125j
liquid phase RIA with a double antibody technique (Cam-
bridge Medical Diagnostics, Bellerica, MA). The assay was
sensitive to a detection limit of 0.24 igF Intra- and inter-
assay variances were calculated to be less than 4.2% and 4.8%
respectively. Serum samples were analyzed in duplicate for
SM-C (IGF-l) using an 251 double antibody disequilibrium
RIA with a preliminary ODS-silica extraction procedure (mc-
Star Corp., Stiliwater, MN). Total serum SM-C (JGF-1) was
determined in this assay. The assay was sensitive to a detection
limit of <2.0 nmolF 1and had <0.01 % crossreactivity with
IGF-2. Intra- and inter-assay variances were less than 4.5%
and 4.9%, respectively.
Statistical analyses of the data were accom-
plished utilizing a multivariate two-way analysis of variance
with repeated measures. Tukey post-hoc tests were calculated
to determine pairwise differences. Significance in this inves-
tigation was chosen at p <0.05.
230 mt.J. Sports Med. 12(1991) W. .1. Kruemer et al.
Table 2 The mean (± 1 SD) responses of serum glucose and whole blood lactate to the heavy resistance exercise protocols
Males Pre Mid 05 15 30 60
Whole Blood
(mmol P1: 1.33(0.40) 3.12*
(0.98) 439*(3.13) 2.63*
(0.90) 2.15*
(0.71) 1.63(0.44) 1.27(0.19)
P-2: 1.15(0.26) 7•87a
8.61 a
(2.84) 852ab
(2.69) 646a
(2.75) 372a
(1.24) 244a
(mnioi )
(mmol P.1: 1.40(0.43) 337*(0.78) 3j4*(1.21) 2.41*
(0.81) 2.31*
(1.12) 1.71(0.98) 1.48(0.73)
P-2: 1.36(0.50) 757a
(1.03) 787a(1.57) 620a
(1.79) 506a(0.99) 348a
(0.88) 2.15(0.85)
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Endogenous Anabolic Hormonal and Growth Factor Responses to Heavy Resistance mt. J. Sports Med. 12 (1991) 231
Fig. 1 Mean (+ SE) serum testosterone
concentrations for males and females to P-i
and P-2 HREPs are presented. * = p <0.05
from corresponding pre-exercise values
and + = p <0.05 from corresponding
female values
The effects of the two resistance exercise proto-
cols on whole blood lactate and serum glucose values for
males and females are shown in Table 2. No changes or differ-
ences were observed in serum glucose concentrations. Whole
blood lactate concentrations were significantly elevated by
both protocols in both males and females, and concentrations
were increased more in the P-2 exercise protocols than in the
P-i workout for both males and females. There was only a tran-
siently higher concentration in the male P-2 exercise protocol
compared to the females (at 5-mm recovery period interval).
Serum testosterone responses are shown in
Fig. 1. Concentrations were increased in males by both exer-
cise protocols and for up to 15 mm into the recovery periods.
Mid-exercise values in males were significantly greater in P-2
than in P-l. All male values were significantly higher than
corresponding female values at every timepoint measured.
Additionally, the 60-mm values for P-I were significantly
greater than corresponding P-2 serum T concentrations for
Growth hormone responses are shown in Fig.
2. Markedly different response patterns were observed be-
tween the two HREPs for both males and females, with a sig-
nificantly greater increase in hGH concentrations in P-2; mid-
exercise values in the males were significantly greater than in
P-i. In P-i, significant increases in serum levels above pre-ex-
ercise values were observed for the males at mid-exercise and
at 30 mm following the exercise protocol. No significant hGH
increases above pre-exercise values were observed in P-i for
female subjects. Furthermore, in both P-i and P-2 HREPs,
females exhibited significantly higher pre-exercise serum
hGH values than males. In P-2, females demonstrated signifi-
cant increases in serum hGH at mid-exercise and at 0, 5, and 15
mm following exercise, and males increased hGH at all time
points. For both males and females, P-2 values, other than pre-
Serum testosterone (nmolI—1) Serum testosterone (nmol I_I)
a 0,0 or a P o a 0, p .j a Oi
S S S Sb S aS 000 Sb 5 0 ebbSe cob cob
I _____________________________________________________________________________________________
-I :. •:.
ItI *
I +
I +
I +
JH +
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232 Int.J.SportsMed. 12 (1991) W. J. Kraemeretal.
Fig. 2 Mean (+ SE) serum human growth
hormone concentrations for males and
females to P-i and P-2 HREPs are pre-
sented. * = p <005 from corresponding
pre-exercise values and + = p <0.05 from
corresponding female values
exercise, were all significantly greater than corresponding P-i
serum hGH concentrations.
Fig. 3 shows the responses of serum soma-
tomedic-C (insulin-like growth factor 1) to P-i and P-2 re-
sistance exercise protocols. In P-i, males demonstrated sig-
nificant increases in serum values immediately following exer-
cise, and females significantly increased serum SM-C 60 mm
following exercise. For the females, P-I values at 60 mm post-
exercise were significantly greater than corresponding P-2
values. In P-2, SM-C significantly increased above resting
levels at mid-exercise, 0 and 5 mm for the males and at mid-
exercise and immediately following exercise for the females.
For the females, P-2 values at mid-exercise were significantly
greater than corresponding P-I values.
Changes in plasma volume shifts during re-
covery were negligible. The greates % change in plasma
volume were observed pre- to immediately post-exercise and
were as follows ( 1 SD):
males P-i —4.1 8.4%, P-2 —4.1 8.8%; females,
P-i = —0.5 7.7%, P-2 —6.0 7.2%.
The most remarkable finding of this investiga-
tion was the difference in hGH stimulation by the two re-
sistance exercise protocols for both men and women. The
more anaerobic P-2 HREP produced a clear and sustained
elevation of hGH, while the P-i exercise protocol had virtually
no effect on hGH concentrations in the female subjects. Fur-
thermore, a substantially lower hGH response in the P-i com-
pared to the P-2 protocol was observed in the males. While the
relative contributions of various physiological mechanisms to
the observed response patterns remain unclear, changes in
hGH have been shown to be influenced by hypoxia, acid base
shifts, and breath holding (10, 26, 29). Differential response
patterns of hGH using heavy and light leg press exercise proto-
cols have been shown previously for men in a study by Van
Helder et al. (30). The data from this investigation demon-
Serum human growth hormone (pg F Serum human growth hormone (tg F
'C -
= U,
= H
____ * II It
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Serum somatomedin-C (nrnolI—1) Serum somatomedin-C (nmol .1_i)
0 0 0
b C
C o V.
Endogenous Anabolic Hormonal and Growth Factor Responses to Heavy Resistance mt. J. Sports Med. 12 (1991) 233
Fig. 3 Mean (+ SE) serum somatomedin-
C (IGF-1) concentrations for males and
females to P-i and P-2 HREPs are pre-
sented. * = p <0.05 from corresponding
pro-exercise and + = p <0.05 from corre-
sponding female values
strate that hGH responses in men are sensitive to both HREPs,
but the high volume, 10 RM load, using short rest periods ap-
pears to augment the magnitude of the hGH response in both
males and females. The adaptational importance of an aug-
mented response of serum hGH to such a high volume, 10 RM
load, and short rest protocol HREP, (i. e. P-2) for exercise pre-
scription of resistance training for women during various
phases of the menstrual cycle remains to be investigated. At
present, the combined effects of a higher volume, shorter rest,
and moderate intensity resistance workout produce a dra-
matic stimulus to serum hGH responses. Studies are needed to
partition out the individual effects of single variables.
The baseline differences in serum hGH con-
centrations between males and females are almost certainly re-
lated to the estrogen sensitization of somatotrophs which gives
a well-established increased responsiveness to a wide variety
of stimuli in women (26). It is unclear why female responses to
the HREPs were not greater than those observed for the males.
It is possible that despite the same relative exercise stress, the
lower absolute total work for each of the HREPs might ac-
count for the lack of a greater exercise responsitivity. The rela-
tive stress (% 1 RM) for each HREP was comparable for men
and women. Still, the contribution of absolute total work, irre-
spective of other exercise variables (e. g. load, rest periods,
etc.), remains to be examined.
The absence of a consistent response pattern of
serum SM-C (IGF-1) may be due to a variety of mechanisms
involved with determining peripherial blood levels. A direct
response of SM-C to the increased hGH stimulation observed
in this study might not have been expected over the 1-hr re-
covery time period observed, since hGH stimulated mRNA
synthesis (which results in an increased SM-C production)
does not peak until 3 to 9 hrs later (1, 3, 14, 23). Due to the com-
plex interactions of SM-C secretion with transporter protein
attachment and release, receptor equilibrium, and receptor
binding actions, the serum response patterns may reflect a
more integrated response of such physiological mechanisms.
Alternatively, the significant increases which were observed
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234 ml. J. Sports Med. 12(199]) W. J. Kruerner ci a!.
could represent a non-hGH mediated release or transient in-
creases in serum transporter protein release due to receptor
binding turnover. Further study is needed to clarify such
In contrast to the hGH hormonal response, T
was acutely stimulated by both HREPs in males. Previous
studies in male subjects have demonstrated that serum T re-
sponses are a function of the amount of muscle mass utilized in
the exercise protocol and the total work performed (11, 15, 18,
25, 31). Conversely, in this study, serum T concentrations in
females remained unaffected by either HREP. This suggests
that the serum increases observed in males is mediated
through the pituitary-testicular axis, either by increased secre-
tion rates or by alterations in testicular blood flow, instead of
through systematic fluid shifts or reduced hepatic clearance
rates (4,24).
Although levels of androstenedione are 10-
fold higher than Tin females and responsive to resistance exer-
cise, T and dihydrotestosterone are still the more potent
musculotrophic androgens (1, 13, 16, 17, 20, 31), with impor-
tant target receptors and effects in the upper body muscula-
ture. The lower levels of these androgens normally en-
countered in females and the absence of any stimulation by
these two different HREPs suggest reasons why females typi-
cally do not achieve levels of upper body muscularity and
strength achieved by males (2). While one study has demon-
strated that small increases in serum T may be possible in
females (6), our study supports previous investigations which
have not found any acute effects on serum T concentrations
(11, 18, 31, 32). Thus in females, it appears that other endo-
genous anabolic hormonal mechanisms may play a more
prominent role in physiological adaptations to heavy re-
sistance training.
In summary, heavy resistance exercise stimu-
lates acute endogenous anabolic responses. These responses
may differ depending upon the type of exercise protocol util-
ized. Growth hormone appears to be the most sensitive to
change in program design. Female hormonal responses in this
study appear to differ due to higher resting levels of growth
hormone during the early foilicular stage of menstrual cycle
and a general lack of testosterone responsiveness to either
heavy resistance exercise protocol. The adaptational effects of
such differential hormonal responses to heavy resistance exer-
cise on cellular adaptations in muscle, connective tissue, and
bone remain to be demonstrated.
The authors would like to thank Joann Ruble and
Carol Glunt for their help in the preparation of this manuscript. Also,
special thanks go to Dini McCurry, Charles Cruthirds, Peter Frykman,
and Alan Vela for their help in data collection and laboratory analyses.
The authors would also like to thank Dr. Paul Rock for his additional
help as a medical monitor. Finally, the authors would like to thank a
dedicated group of test subjects who gave a great deal of their time and
effort to make this study possible.
Human Research
Human subjects participated in these studies after
giving their free and informed voluntary consent. Investigators ad-
hered to AR 70—25 and USAMRDC Regulation 70—25 on Use of Vol-
unteers in Research.
The views, opinions, and/or findings contained in
this report are those of the author(s) and should not be construed as an
official Department of the Army position, policy, or decision, unless
so designated by other official documentation.
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William J. Kraemer, Ph.D.
Center for Sports Medicine
Greenberg Sports Complex
The Pennsylvania State University
University Park, PA 16802
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... Testosterone serum level, for example, is 10-to 40-fold higher in men at rest (Kraemer et al., 1991;Vingren et al., 2010) and because of its androgenic-anabolic potential (Brodsky et al., 1996;Bhasin et al., 1997;Snyder et al., 2000) thought to mediate muscle mass through the ability to increase (Urban et al., 1995) the synthesis and/ or decreasing (Zhao et al., 2008) the breakdown of myofibrillar protein. Estrogen is thought to regulate the muscle mass of women as this hormone exerts the capacity to downregulate myofibrillar protein breakdown (Pollanen et al., 2007). ...
... While serum testosterone levels following heavy RE are acutely elevated in men (Fleck and Kraemer, 2014) they do not change in women after RE (Kraemer et al., 1991;Kraemer et al., 1993;Staron et al., 1994;Hakkinen and Pakarinen, 1995). For GH, the response to RE seems to be similar between gender, as RE induced a post-exercise increase of GH in women and men (Kraemer et al., 1991;Hakkinen and Pakarinen, 1995). ...
... While serum testosterone levels following heavy RE are acutely elevated in men (Fleck and Kraemer, 2014) they do not change in women after RE (Kraemer et al., 1991;Kraemer et al., 1993;Staron et al., 1994;Hakkinen and Pakarinen, 1995). For GH, the response to RE seems to be similar between gender, as RE induced a post-exercise increase of GH in women and men (Kraemer et al., 1991;Hakkinen and Pakarinen, 1995). While research on the acute response of IGF-1 to RE is equivocal (Kraemer et al., 1991;Kraemer et al., 1993;Consitt et al., 2001;Kraemer and Ratamess, 2005), the combination of GH and IGF-1 seems to play a testosterone-compensatory effect in women as women show a markedly increase in fiber CSA as a result of regimented RE (Staron et al., 1994) despite low levels of testosterone. ...
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Muscle mass and force are key for movement, life quality, and health. It is well established that resistance exercise is a potent anabolic stimulus increasing muscle mass and force. The response of a physiological system to resistance exercise is composed of non-modifiable (i.e., age, gender, genetics) and modifiable factors (i.e., exercise, nutrition, training status, etc.). Both factors are integrated by systemic responses (i.e., molecular signaling, genetic responses, protein metabolism, etc.), consequently resulting in functional and physiological adaptations. Herein, we discuss the influence of non-modifiable factors on resistance exercise: age, gender, and genetics. A solid understanding of the role of non-modifiable factors might help to adjust training regimes towards optimal muscle mass maintenance and health.
... The acute RE program variables include exercise choice, order, volume, intensity (or load), and the inter-set rest intervals [10,11,12]. These variables influence the endocrine responses to resistance exercise [13,14,15]. Also, it is well known that manipulation of the acute program variables influences the degree and specificity of skeletal muscle adaptation and performance [16,17]. ...
... Additionally, the MW session utilized three different exercises rather than just one, resulting in the overall greater external work. Although the timing of the blood collection after the RE stimulus in the present study might have contributed to the differences from Shaner's results, the POST exercise blood draw was collected 5 minutes after the completion of the exercise bout, which has been shown to best reflect the acute RE T responses [1,13,14]. Also, when compared to the present data, Shaner et al. [23] reported greater T concentrations in general. However, it should be noted that all values were within normal physiological ranges and that relative increases in T for both studies were very similar. ...
... Previously, Shaner et al. [23] reported greater increases in GH following a series of squats than following leg press and concluded that the greater GH response was likely due to a difference in total work performed. Although numerous studies have reported greater GH responses with increased work or RE volume performed [13,14,27,28], no significant difference was observed in the present study between the FW and MW protocols despite a significant difference in external work. The lack of significant differences between the protocols may be explained by the magnitude of the GH responses. ...
... A comparison of the GH responses of men and women revealed that men tended to exhibit greater increments of GH immediately after a resistance exercise bout. The magnitude of these increases as well as the disparity between the responses of men and women were greater in a study including resistance trained inexperienced participants compared to those who already had some experience with resistance training [64,69]. Across the included studies, the intervention groups investigating female subjects reported a median change of GH concentrations of -1%, while the intervention groups investigating male subjects reported a median increase of 304%. ...
... Although sex, rest intervals and the number of repetitions appeared to influence the immediate GH response there was no clear evidence that indicated an influence of these parameters on the recovery of GH levels post-exercise. While five studies [39,41,64,97,123] reported that GH increased further in at least one of the investigated intervention groups during the early recovery period (10-30 minutes), the majority of the studies that employed multiple follow-up measures described a decline of the GH levels 10-30 minutes into recovery. A study investigating 13 male participants before, 15 minutes and 30 minutes after leg press exercise reported that the GH concentrations further increased in the higher volume groups with a peak at 15 minutes, while they gradually decreased in the lower volume groups [123]. ...
... A study investigating 13 male participants before, 15 minutes and 30 minutes after leg press exercise reported that the GH concentrations further increased in the higher volume groups with a peak at 15 minutes, while they gradually decreased in the lower volume groups [123]. All studies that employed follow-up measures 60 minutes post-exercise described that peripheral GH decreased towards -or in most cases even below -the resting value [40,45,62,64,65,75,82,95]. ...
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Background: The nervous system integrates the immune system in the systemic effort to maintain or restore the organism's homeostasis. Acute bouts of exercise may alter the activity of specific pathways associated with neuroendocrine regulation of the immune system. Objective: To examine the acute effects of heavy resistance exercise on biomarkers of neuroendocrine-immune regulation in healthy adults. Methods: A systematic literature search was conducted using PubMed, Cochrane Controlled Trials Register, Web of Science and SportDiscus with no date restrictions up to March 2021. Clinical trials in English or German were included if they measured the blood plasma or serum concentrations of specific biomarkers of neuroendocrine-immune regulation (adrenaline, noradrenaline, acetylcholine, vasoactive intestinal peptide (VIP), cortisol, growth hormone, calcitonin gene-related peptide (CGRP), substance p, serotonin, brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF) or glia-derived neurotrophic factor (GDNF)) in a resting state prior to and no later than 60 minutes after an acute bout of heavy resistance exercise in healthy adults. Results: 7801 records were identified through literature search, of which 36 studies, with a total of 58 intervention groups, met the inclusion criteria. Evidence was found that an acute bout of heavy resistance exercise increased the levels of adrenaline (median: 185%), noradrenaline (median: 113%) and GH (median: 265%) immediately after the exercise. Mixed results were found for cortisol (median: 0%), suggesting that its response might be more sensitive to the configuration of the exercise scheme. The limited evidence regarding the effects on BDNF and ACTH allows no firm conclusions to be drawn about their response to heavy resistance exercise. The vast majority of the included studies reported a return of the biomarker concentrations to their baseline value within one hour after the termination of the exercise bout. No studies were identified that investigated the response of acetylcholine, VIP, CGRP, substance p, serotonin, NGF or GDNF to heavy resistance exercise. Conclusions: A bout of heavy resistance exercise alters the circulating concentrations of selected biomarkers of neuroendocrine-immune regulation. Both subject characteristics, such as sex as well as exercise parameters, such as rest intervals appear to have the potential to influence these effects.
... Even in relatively safe LT intensity exercise, lactate accumulation and heart rate (HR) increases when exercising for a long time without rest have been reported [18]. Additionally, the amount and timing of rest periods between exercise have been found to significantly affect metabolic [19], hormonal [20], and other responses [21] in resistance training, while few studies have addressed the effects of rest in aerobic exercise. ...
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This study aimed to compare the degree of exhaustion and trophic effects between continuous exercise (CE) and intermittent exercise (IE) at lactate threshold (LT) intensity. Seven healthy men (age: 43–69 years) performed the following three experimental tests in a randomized crossover order: (1) control; (2) CE, performed as a 20-min of cycling at LT intensity; and (3) IE, performed as 20 sets of a one-min bout of cycling at LT intensity with a 30-s rest between every two sets. Heart rate (HR), blood lactate concentration (LA), rating of perceived exertion (RPE), catecholamines, cortisol, growth hormone, insulin-like growth factor (IGF)-1, and brain-derived neurotrophic factor (BDNF) were measured. The sampling timing in each test was as follows: 10 min before the onset of exercise, at the 25%, 50%, and 100% time points of exercise, and at 10 min after exercise. IE was found to be accompanied by a lower degree of exhaustion than CE in measures of HR, LA, RPE, catecholamines, and cortisol. In terms of trophic effects, both of IGF-1 and BDNF increased in CE, while a marginal increase of BDNF was observed in IE. The results indicated that IE induces lower stress than CE, but may not be effective for inducing trophic effects.
... Achieving greater metabolic stress during resistance exercise has been shown to improve muscular strength and hypertrophy in men [74]. Further, altered lactate responses may drive important anabolic signaling pathways through increasing serum hormone levels of testosterone [75,76], cortisol [77], and growth hormone [78]. Resultantly, relatively high training volumes including AEL have shown greater postexercise testosterone elevations [73], while others have found AEL to result in similar concentrations of post-exercise total and bioavailable testosterone, cortisol, and growth hormone compared to traditional loading [61,68,73,79]. ...
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Accentuated eccentric loading (AEL) employs heavier load magnitudes in eccentric actions than concentric actions of complete stretch-shortening cycles. In doing so, unique neuromuscular and molecular responses are expected to result in acute post-activation performance enhancements, as evidenced by increased movement velocity or power. Improvements are dependent upon load selection, which varies across exercises, such as jumps and bench press throws (eccentric: 20-40 kg or 20-30% of body mass; concentric: body mass only), and squats and bench press (eccentric: 77.3-120% One-Repetition Maximum (1-RM); concentric: 30-90% 1-RM). The efficacy of AEL is dependent upon the concentric load used, which in turn is influenced by the magnitude of the eccentric load. Greater strength relative to body mass may enable the maintenance of technique and pacing during AEL, necessary for resultant performance enhancements, particularly when using eccentric loads exceeding the individual’s concentric 1-RM. Before prescribing AEL practitioners should consider: training experience, strength relative to body mass, the particular exercise, AEL application method, and the magnitude of both eccentric and concentric loads. Thus, the aims of this brief review are to describe: 1) neuromuscular and molecular constructs of AEL; 2) acute effects of AEL; 3) chronic effects of AEL; 4) loading considerations; 5) practical applications.
Conference Paper
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The aim of the research was to determine the effects of exercise programs on lower limbs’ explosive strength in junior tennis players. For collecting of appropriate scientific researches from 2010 till 2021 the following keywords were used: tennis, eplosive strength, training and exercise program, motor ability- in three electronic databases (Google Scholar, KobSon, SCI index). Based on the keywords, the existing scientific researches have gone through three levels of selection in order to enter the final analysis. These analyzed researches are presented through five groups of parameters: authors of the research, sample description (sex, age and number), experimental treatment (description, frequency), measuring instruments and results. Only 10 researches have met the criteria, and the analysis shown that the exercise programs lasted from 6 to 8 weeks, with weekly training frequency between two and three times of 30 minutes, that is, as an addition to the training. Exercise programs that have been used for the development of lower limbs’ explosive strength in tennis players were of plyometric type, with and without equipment. The tests, by which the assessment of the lower limb’ explosive strength was determined, were: CMJ, CMJ (bilateral/unilateral), SJ, DJ and OLH. The results of the applied exercise programs have shown, in all of the analyzed researches, statistically significant progress (p<0.05). A lower-limb explosive strength represents a very significant segment within the basic motor skills of tennis players in the junior category due to the latent period of development period, but also to the pretensions of the increasing dynamism of the tennis game. In accordance with this, the research can help trainers to use the information for planning the development of the explosive strength of their tennis players, and for athletes to advance and manifest the maximum potential of this part of this basic motor space.
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Objectives Multiple physiopathological conditions through stimulate atrogene led to trigger skeletal muscle atrophy, which the regulation of this signaling pathway is still not fully understood. In this study, researchers evaluated the assumptions that saffron extract and resistance training may inhibit muscle atrophy and Atrogene expression, increase testosterone concentration as well as weight in rats with dexamethasone (dex)-induced muscle atrophy. Study design We evaluated the effects of saffron extract and resistance training on atrophic markers in rats with dex-induced muscle atrophy using seven experimental groups. Methods 42 male SD (Sprague-Dawley) rats were randomly distributed into seven subgroups: (1) dex-control (cn), (2) dex-resistance training (tn), (3) dex-saffron feeding 20 mg/kg/day (sa 20 mg), (4) dex-saffron feeding 40 mg/kg/day (sa 40 mg), (5) dex-saffron feeding 20 mg/kg/day + resistance training (sa 20 mg + tn), (6) dex-saffron feeding 40 mg/kg/day + resistance training (sa 40 mg + tn), and (7) healthy control i.e. non-injected dex (cn-i). order to induce muscle atrophy, groups 1 to 6 were intraperitoneally injected with dexamethasone (750 μg/kg). The resistance training protocol and 20 and 40 mg/kg/day saffron treatments were carried out for 2 months. Results Total weight, soleus, and EDL muscles weight in dex + 20 and 40 mg Saffron, resistance training, resistance training + 20, and 40 mg Saffron groups were significantly increased compared to pre-experimental levels or the health control group (P < 0.05). The serum testosterone level was significantly increased in resistance training + 20 and 40 mg Saffron groups compared to the health control group (P < 0.05). The level of Atrogin-1, Murf-1, and Mir-29b gene expressions in soleus and EDL muscles was significantly elevated in resistance training + 20 and 40 mg Saffron groups compared to the health control group (P < 0.05). Conclusion These findings set saffron alongside resistance exercise as a new target in therapeutic approaches toward clinical conditions causing muscle mass loss.
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Purpose: To compare the effects of scapulothoracic stabilization exercises (SSE) in addition to complex decongestive physiotherapy (CDP) on scapular function, posture, and balance compared to CDP alone in women with lymphedema after mastectomy. Methods: The patients were randomly divided into two groups as CDP (n:12) and CDP+SSE (n:13). While only CDP (3-week treatment phase and 5-week maintenance phase) was applied in the CDP group, CDP (3-week treatment phase and 5-week maintenance phase) and SSE (8 weeks) were applied in the CDP+SSE group. Scapulothoracic muscle strength, scapular endurance, scapular dyskinesia, thoracic kyphosis, general posture, and balance were evaluated before the treatment phase (TP), after the TP, and after the 5th week of the maintenance phase (MP). Results: Improvements in the lower trapezius muscle strength were found in both groups after the TP (p<0.05). In addition, middle trapezius muscle strength and general posture improved more in the CDP+SSE group than in the CDP group after the TP (p<0.05). In the MP, scapulothoracic muscle strength, scapular endurance and general posture improved more in CDP+SSE group compared to the CDP group (p<0.05). Conclusion: In upper extremity lymphedema patients, incorporating additional SSE in CDP may contribute to the improvement of posture and scapular functions.
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To determine if a sex difference exists in the androgen response to heavy-resistance exercise, serum testosterone (T) and androstenedione (A) concentrations were measured in 20 men and 20 women before and during a 2-h period following 30 min of weight lifting. Hormone concentrations from venous blood samples were determined by radioimmunoassay. Prior to weight lifting, T for men (3.510.24 ngml–1) was approximately 10 times that for women (0.360.04 ngml–1), whereas A for women (1.260.07 ngml–1) was 43% higher than for men (0.880.07 ngml–1). Immediately following weight lifting, T was increased significantly (p<0.01) in men (0.76 ngml–1, 21.6%), but nonsignificantly in women (0.06 ngml–1, 16.7%). Resting T levels were restored within 30 min. Serum A levels decreased significantly (p<0.01) below pre-exercise levels at 2 h post-exercise for both men and women. It was concluded that men have a greater absolute T response to weight lifting than women, whereas the absolute A response to weight lifting is similar in men and women.
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Summary Muscle differentiation and growth are accomplished by two fundamental sets of cellular processes, protein accretion and cell proliferation. This review is restricted to a discussion of the role of cell proliferation in the growth of muscle during prenatal and postnatal life. More specifically, the discussion is divided into three topic areas, which include the role of muscle precursor cell proliferation in prenatal and postnatal development and a review of factors that may be regulating the proliferation of myogenic cells. The proliferation of embry- onic myogenic cells and their differentia- tion into multinucleated fibers, as well as the proliferation of myogenic ceils in postnatal muscle (satellite cells) are major factors deter- mining the ultimate mass of muscle that can be produced by an animal.
This article presents a factual and revealing analysis of the values of resistance training for female athletes. Discussions on training principles, equipment, and exercise prescription, including special considerations for women, provide a comprehensive approach to this topic.
The growth-promoting actions of a number of hormones on muscle have been studied by a number of investigators during the past two decades, and some reasonably solid conclusions can now be reached. The somatomedins and insulin are major stimulators of anabolic processes in skeletal muscle; the last remaining uncertainty (absence of evidence that the somatomedins could replace growth hormone in stimulating weight gain in hypophysectomized animals) has recently been removed. The situation with growth hormone is less clear. Evidence from studies on isolated diaphragm muscles is consistent in indicating responsiveness to growth hormone, but most of it was obtained using supraphysiological levels of the hormone, and (in contrast to somatomedin and insulin) it has not been possible to demonstrate direct effects of this hormone on isolated muscle cells. There are some similar problems in the case of insulin—it is not clear to what extent the anabolic actions of insulin can be attributed to its cross-reaction with the somatomedin receptor and/or its effects on energy metabolism, but there is recent convincing evidence that this hormone has direct anabolic effects on muscle cells in culture. The effects of androgens are much more apparent in the whole animal than in isolated muscles or cell culture systems, and they have been more difficult to characterize. The thyroid hormones are clearly required for normal growth and development in the intact animal, but there is not much information on their actions on isolated muscle or cultured cells. Surprisingly, Cortisol exhibits some growth-promoting effects, but these may be attributable to maintenance of the cells in a “healthy” state rather than to a direct stimulation of anabolic processes. In no case is there any detailed biochemical information on the mechanisms by which any of these growth-promoting actions occur, although it is reasonable to infer that the presence of a cytoplasmic receptor for testosterone in muscle indicates a typical steroid-induced activation of RNA synthesis and a resultant increase in protein synthesis. Thus, although a good deal of progress has been made in cataloging the hormones most likely to have direct effects on the growth of muscle, much remains to be done in determining just how those hormones act.
The somatomedins, or insulin-like growth factors (IGFs), constitute a family of peptide hormones which are growth hormone dependent, possess insulin-like activity and have mitogenic activity in a wide variety of cell lines1. Two human somatomedins have been purified and sequenced: IGF-I has a molecular weight of 7649, and consists of 70 amino acids, while IGF-II has a molecular weight of 7471, with 67 amino acids2,3. A rat equivalent of IGF-II, termed multiplication stimulating activity (MSA), has also been purified and sequenced; it differs from human IGF-II in four of the 67 amino acid positions4. The sequences of cDNAs encoding for human prepro-IGF-I and -II have been elucidated, and the respective 130 and 180 amino acid precursors predicted5,6. IGF-II has been mapped to the short arm of chromosome 11, tightly linked to both the insulin gene and the c-Ha-rasl proto-oncogene7. IGF-I maps to chromosome 12, which is evolutionarily related to chromosome 11, and carries the gene for the c-Ki-ras2 proto-oncogene8.
This report describes a total underwater weighing system for the determination of body density to estimate body composition. It was designed specifically to be suitable for transport to field sites to quickly weigh large groups of subjects accurately and reproducibly. The tank itself is made of 1/4 inch welded aluminum, weighs 141 pounds and is 4x3x4 feet in dimension. The subject to be weighed is suspended in the water on an aluminum chair and exhales to a residual lung volume through a snorkel device. Weights are registered with an electronic load cell, converted to a digital signal and fed into a desk top computer and software program which assists in the selection of stable readings and the computation of density, body fat and fat free mass. Heating and filtration of the water are accomplished with attached commercial Jacuzzi components. The system has been tested both in the laboratory and at four field locations and found to be both rugged and dependable. Repeated trials over days have shown a very high degree of reproducibility. Keywords: Body composition, Densitometry, Hydrostatic weighing, Body fat.
The effects of a 24-weeks' progressive training of neuromuscular performance capacity on maximal strength and on hormone balance were investigated periodically in 21 male subjects during the course of the training and during a subsequent detraining period of 12 weeks. Great increases in maximal strength were noted during the first 20 weeks, followed by a plateau phase during the last 4 weeks of training. Testosterone/cortisol ratio increased during training. During the last 4 weeks of training changes in maximal strength correlated with the changes in testosterone/cortisol (P<0.01) and testosterone/SHBG (P<0.05) ratios. During detraining, correlative decreases were found between maximal strength and testosterone/cortisol ratio (P<0.05) as well as between the maximal strength and testosterone/SHBG ratio (P<0.05). No statistically significant changes were observed in the levels of serum estradiol, lutropin (LH), follitropin (FSH), prolactin, and somatotropin. The results suggest the importance of the balance between androgenic-anabolic activity and catabolizing effects of glucocorticoids during the course of vigorous strength training.