NSCA_3E_chap031

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Endocrine Responses to Resistance
Exercise



William J. Kraemer, PhD, CSCS, FACSM, FISSN, FNSCA

Jakob L. Vingren, PhD, CSCS

Barry A. Spiering, PhD, CSCS

chapter

3


Endocrine

Responses

to Resistance

Exercise


Chapter Objectives


Understand basic concepts of endocrinology.


Explain the physiological roles of anabolic
hormones.


Describe hormonal responses to resistance
exercise.


Develop training programs that demonstrate
an understanding of human endocrine
responses.

Key Point


It has been theorized that the endocrine
system can be manipulated naturally with
resistance training to enhance the devel
-
opment of various target tissues, thereby
improving performance.

Section Outline


Synthesis, Storage, and Secretion of
Hormones

Key Term


hormones:
Chemical messengers that are
synthesized, stored, and released into the
blood by endocrine glands and certain other
cells.

Glands of the Body


Figure 3.1 (next slide)


The principal endocrine glands of the body along
with other glands that secrete hormones

Figure 3.1

Section Outline


Muscle as the Target for Hormone
Interactions

Muscle Cell


Figure 3.2 (next slide)


The muscle cell is a multinucleated cell in which
each nucleus controls a region of the muscle protein
(called a
nuclear domain
).

Figure 3.2

Section Outline


Role of Receptors in Mediating Hormonal
Changes

Lock
-
and
-
Key Theory

for Hormonal Action


Figure 3.3 (next slide)


A schematic representation of the classic lock
-
and
-
key theory for hormonal action at the cell receptor
level

Figure 3.3

Androgen Receptor Diagram


Figure 3.4 (next slide)


Diagram of a typical androgen receptor on the DNA
element in the nucleus

Figure 3.4

Section Outline


Steroid Hormones Versus Polypeptide
Hormones


Steroid Hormone Interactions


Polypeptide Hormone Interactions

Steroid Hormones Versus

Polypeptide Hormones


There are two main categories of hormones:


Steroid


Polypeptide (or simply
peptide
)

Hormone Structure


Figure 3.5 (next two slides)


Structure of


(a)

a polypeptide hormone (growth hormone, 22 kDa)


(b)

a steroid hormone (testosterone)

Figure 3.5a

Figure 3.5b

Steroid Hormones Versus

Polypeptide Hormones


Steroid Hormone Interactions


A steroid hormone passively diffuses across the
sarcolemma of a muscle fiber.


It binds with its receptor to form a hormone
-
receptor
complex (H
-
RC).


H
-
RC arrives at the genetic material in the cell’s
nucleus and “opens” it in order to expose tran
-
scriptional units that code for the synthesis of
specific proteins.

(continued)

Steroid Hormones Versus

Polypeptide Hormones


Steroid Hormone Interactions
(continued)


RNA polymerase II binds to the promoter that is
associated with the specific upstream regulatory
elements for the H
-
RC.


RNA polymerase II transcribes the gene by coding
for the protein dictated by the steroid hormone.


Messenger RNA (mRNA) is processed and moves
into the sarcoplasm of the cell, where it is translated
into protein.

Steroid Migration


Figure 3.6 (next slide)


The slide shows typical steroid migration into a
target cell by either testosterone in skeletal muscle
or dihydrotestosterone in sex
-
linked tissues.


Only one hormone pathway (testosterone or
dihydrotestosterone) is targeted for one cell, but

the two are shown together in this diagram.

Figure 3.6

Steroid Hormones Versus

Polypeptide Hormones


Polypeptide Hormone Interactions


Cyclic adenosine monophosphate
-
dependent (cyclic
AMP
-
dependent) signaling pathway


Cytokine
-
activated JAK/STAT signaling pathway


Prototypical growth factor, mitogen
-
activated
signaling pathway

Polypeptide Hormone Interaction


Figure 3.7 (next slide)


The slide shows typical polypeptide hormone
(growth hormone in this example) interaction with

a receptor via the cytokine
-
activated JAK/STAT
signaling pathway.


Although the hormone binds to an external receptor,
a secondary messenger (STAT) is activated that can
enter the cell nucleus.


Tyr
-
P = tyrosinase related protein

Figure 3.7

Section Outline


Heavy Resistance Exercise and Hormonal
Increases

Key Point


The specific force produced in activated
fibers stimulates receptor and membrane
sensitivities to anabolic factors, including
hormones, which lead to muscle growth

and strength changes.

Section Outline


Mechanisms of Hormonal Interactions

Mechanisms of Hormonal Interactions


Interactions with receptors are greater when


exercise acutely increases the blood concentrations
of hormones.


Receptors are less sensitive when


the physiological function to be affected is already
close to a genetic maximum,


resting hormone levels are chronically elevated due
to disease or exogenous drug use, and


mistakes are made in exercise prescriptions.

Section Outline


Hormonal Changes in Peripheral Blood

Hormonal Changes

in Peripheral Blood


Mechanisms contributing to changes in peripheral
blood concentrations of hormones:


Fluid volume shifts


Tissue clearance rates


Hormonal degradation


Venous pooling of blood


Interactions with binding proteins in the blood


These mechanisms interact to produce certain
concentrations of hormones in the blood, which
influences the potential for interaction with
receptors.

Key Point


Hormone responses are tightly linked to the
characteristics of the resistance exercise
protocol.

Section Outline


Adaptations in the Endocrine System

Adaptations in the Endocrine System


Examples of the potential types of
adaptation with resistance exercise:


Amount of synthesis and storage of hormones


Transport of hormones via binding proteins


Time needed for the clearance of hormones
through liver and other tissues


Amount of hormonal degradation that takes place
over a given period of time


How much blood
-
to
-
tissue fluid shift occurs with
exercise stress


How many receptors are in the tissue

Section Outline


Primary Anabolic Hormones


Testosterone


Free Testosterone and Sex Hormone

Binding Globulin


Testosterone Responses in Women


Training Adaptations of Testosterone


Growth Hormone


Efficacy of Pharmacological Growth Hormone


Growth Hormone Responses to Stress


Growth Hormone Responses in Women


Training Adaptations of Growth Hormone

(continued)

Section Outline
(continued)


Primary Anabolic Hormones


Insulin
-
Like Growth Factors


Exercise Responses of Insulin
-
Like Growth Factors


Training Adaptations of Insulin
-
Like Growth Factors

Primary Anabolic Hormones


There are three primary hormones involved
in muscle tissue growth and remodeling:


Testosterone


Growth hormone (GH)


Insulin
-
like growth factors (IGFs)

Primary Anabolic Hormones


Testosterone


The primary androgen hormone that interacts with skeletal
muscle tissue


Effects on muscle tissue: GH responses that lead to protein
synthesis, increased strength and size of skeletal muscle,
increased force production potential and muscle mass


Diurnal variations


Men: Exercise later in the day is more effective for increasing
overall testosterone concentrations over an entire day.


Women: There are lower concentrations and little variation during
the day.

Biosynthesis of Testosterone

From Cholesterol


Figure 3.8 (next slide)


The series of chemical reactions in the biosynthesis
of testosterone from cholesterol

Figure 3.8

Key Point


Large muscle group exercises result in
acute increased serum total testosterone
concentrations in men.

Primary Anabolic Hormones


Testosterone


Free Testosterone and Sex Hormone

Binding
Globulin


A higher total (bound) testosterone level allows for the
potential of more free testosterone.


The free hormone hypothesis states that only the free
hormone interacts with target tissues.


Testosterone Responses in Women


Women have 15
-

to 20
-
fold lower concentrations of
testosterone than men do, and if acute increases occur
after a resistance training workout, they are small.


Training Adaptations of Testosterone

Serum Testosterone

Responses to Exercise


Figure 3.9 (next slide)


Male (green bars) and female (gold bars) serum
testosterone responses to two exercise programs:


(a)

a protocol entailing eight exercises using 5RM and

3
-
minute rest periods between sets and exercises


(b)

a program that called for eight exercises using 10RM
and 1
-
minute rest periods between sets and exercises

(the total work for the second protocol was higher)


* = significantly above preexercise levels


+ = significantly above the other group

Figure 3.9

Reprinted, by permission, from Kraemer et al., 1990.

Primary Anabolic Hormones


Growth Hormone


Secreted by the pituitary gland


Interacts directly with target tissues, which include
bone, immune cells, skeletal muscle, fat cells, and
liver tissue


Regulated by neuroendocrine feedback mechanisms
and mediated by secondary hormones


GH release patterns altered by age, gender, sleep,
nutrition, alcohol consumption, and exercise

Growth Hormone Cybernetics


and Interactions


Figure 3.10 (next slide)


Diagram of growth hormone cybernetics and
interactions

Figure 3.10

Primary Anabolic Hormones


Growth Hormone


Efficacy of Pharmacological Growth Hormone


Pharmacological use of GH has unknown and
unpredictable results.


Growth Hormone Responses to Stress


GH responds to exercise stressors, including resistance
exercise.


GH response depends on load, rest, and volume of
exercise.

Primary Anabolic Hormones


Growth Hormone


Growth Hormone Responses in Women


GH concentrations and responses to exercise vary with
menstrual phase.


Women have higher blood levels of GH than do men.


Training Adaptations of Growth Hormone


There is little change in single measurements of resting GH
concentrations in resistance
-
trained individuals.


Training
-
related changes in GH include a reduction in GH
response to an absolute exercise stress and alterations in
GH pulsatility characteristics.

Key Point


Growth hormone is important for the normal
development of a child and appears to play
a vital role in adapting to the stress of
resistance training. However, GH injections
result in a wide variety of secondary effects
not related to changes in muscle size or
strength and can, in fact, result in hyper
-
trophy with less force production than
occurs with exercise
-
induced hypertrophy.

Primary Anabolic Hormones


Insulin
-
Like Growth Factors


Exercise Responses of Insulin
-
Like Growth Factors


Insulin
-
like growth factor I (IGF
-
I) is most studied because
of its role in protein anabolism.


Exercise results in acute increases in blood levels of IGF
-
I.

Insulin
-
Like Growth

Factor I and Exercise


Figure 3.11 (next slide)


Responses of insulin
-
like growth factor I to a
multiple
-
set, heavy resistance exercise protocol on
three consecutive days with and without nutritional
supplementation of protein
-
carbohydrate (i.e., Mass
Fuel) before and during the 1
-
hour recovery period



p < .05 from corresponding placebo value

Figure 3.11

Adapted, by permission, from Kraemer et al., 1998.

Primary Anabolic Hormones


Insulin
-
Like Growth Factors


Training Adaptations of Insulin
-
Like Growth Factors


Changes in IGF
-
I appear to be based on the starting
concentrations before training.


If basal concentrations are low, IGF
-
I increases.


If basal concentrations are high, there is no change or it
decreases.

Section Outline


The Adrenal Hormones


Cortisol


Role of Cortisol


Resistance Exercise Responses of Cortisol


Catecholamines


Role of Catecholamines


Training Adaptations of Catecholamines

The Adrenal Hormones


Cortisol


Role of Cortisol


Catabolic effects


Converts amino acids to carbohydrates, increases the level

of enzymes that break down proteins, and inhibits protein
synthesis


Resistance Exercise Responses of Cortisol


Cortisol increases with resistance exercise.


Training may reduce the negative effects of this increase.


Vast differences are observed in the physiological role of
cortisol in acute versus chronic responses.

Key Point


Resistance exercise protocols that use high
volume, large muscle groups, and short rest
periods result in increased serum cortisol
values. Though chronic high levels of
cortisol may have adverse catabolic effects,
acute increases may contribute to the
remodeling of muscle tissue.

The Adrenal Hormones


Catecholamines


Role of Catecholamines


Increase force production via central mechanisms and
increased metabolic enzyme activity


Increase muscle contraction rate


Increase blood pressure


Increase energy availability


Increase blood flow


Augment secretion rates of other hormones, such as
testosterone


Training Adaptations of Catecholamines

Key Point


Training protocols must be varied to allow
the adrenal gland to engage in recovery
processes and to prevent the secondary
responses of cortisol, which can have
negative effects on the immune system and
protein structures.

Section Outline


Other Hormonal Considerations

Other Hormonal Considerations


Many other hormones create an optimal environment

in which the primary hormonal actions can take place.


Insulin, thyroid hormones, and beta
-
endorphins affect
growth, repair, and exercise stress mechanisms.


Improvements in insulin resistance with resistance
training may reflect only an acute effect from the most
recent exercise session.


Researchers have found slight, nonsignificant
decreases in serum concentrations of total and free
thyroxine after 20 weeks of resistance training.