Module 1
The Endocrine System
A. The Endocrine System
The human body is designed to provide amazing control of its physiological
systems during physical exercise and sport performance. Each of these physiological
systems is closely regulated and coordinated while the desired result is performance
improvement. As similar to other physiological systems, the hormonal system is closely
controlled and responds to exercise and physical activity to assure optimal results. The
hormonal or endocrine system is very important as it can influence the other systems of
the body. Most importantly, it is critical to understand how the endocrine system
responds to the short-term requirements of a single bout of exercise and how it adapts to
the chronic stresses of a long-term training program.
The endocrine system helps to maintain homeostasis in the body by regulating
hormonal functions. This occurs through the communication between chemicals in the
body, called messengers, that regulate different physiological actions. The messengers
are secreted into the bloodstream, travel to their respective binding sites, and promote
changes in cellular functions upon arrival at the designated binding site.
For the purposes of this chapter, a hormone is a chemical compound that is
secreted into the circulation to regulate a biological function at a distant site in the body.
A hormone is secreted directly into the bloodstream from a tissue known as an endocrine
gland. These glands contain specialized cells designed to create and release their
respective hormones. A neurohormone is very similar except that it is released from a
nerve ending into the circulation. Regardless of the source, the hormones and
neurohormones travel to various parts of the body until they reach their target tissues.
Once arrived, they can bind to specialized receptors on or in the cells of the target tissues
and they will influence how the target tissues function.
Numerous hormones and neurohormones are involved in the proper functioning
of a healthy system. Hormones are chemical compounds that are produced by endocrine
tissues and typically released into the circulation. Neurohormones are a type of hormone
that also functions as a neurotransmitter in the nervous system. Of particular interest are
those hormones that specifically respond to physical exercise and sport performance.
Numerous endocrine tissues in the body participate in this process, whether it involves
the short-term or sudden acute responses to a single bout of exercise or the long-term
chronic adaptations to regular exercise and training. Figure 6.1 illustrates, in both a male
and female, the endocrine glands and tissues responsible for the hormones and
neurohormones discussed in this chapter. In general, these tissues release their hormonal
products into the body’s circulation where they are transported to their target sites.
When hormones or neurohormones are synthesized in their respective cells, not
all are released into the circulation. Certain chemical compounds never leave the cell and
they can remain within the cell and influence the activity of the cell in some form or
fashion. These types of chemical compounds are called autocrine hormones (5). An
example of this is insulin-like growth factor-I (IGF-I). IGF-I is produced in many cells of
the body and is responsible for many of the actions of growth hormone. IGF-I can be
measured from the circulating blood, yet it is important to mention that some IGF-I never
leaves the cell.
Some hormones leave their endocrine cells and never enter circulation, but they
travel to adjacent cells, where they exert their influence on cellular activity. These are
called paracrine hormones (6). As with an autocrine system, circulating amounts of these
paracrine chemical compounds may be important, but they do not account for the portion
that never enters the circulation.
The term endocrine refers to hormones that are released into the bloodstream or
lymph system to control growth, metabolism, mood, and reproduction. Also, the term
neuroendocrine refers to hormones that are released into the bloodstream or lymph
system following stimulation of the nervous system. Once the chemical compound is
released, it travels via the circulation and eventually reaches its target tissue or is broken
down into its metabolic by-products. Although many factors influence the concentrations
of these hormones in the blood, it is still essential to measure their concentrations in the
blood to fully understand their roles in physiological function.
The steroid hormones share the same fourcarbon-ring structure and affect growth
and the development of the sex organs. All steroid hormones are made from a cholesterol
molecule, which is called a precursor molecule. Depending on the endocrine tissue
involved, the cholesterol molecule is converted by enzymes (proteins serving as catalysts
in mediating and speeding a specific chemical reaction) into the final steroid hormone
that is to be released. Different endocrine glands have different hormonal enzymes that
determine which steroid hormone will be produced. Since the steroid hormones are
formed from cholesterol, they are lipophilic, which means that they can pass through the
lipid membrane of a cell. Pharmaceutical forms of steroids, which are orally ingested or
injected are called exogenous steroids, which means that they come from outside the
body. These steroid types are typically variations of the hormones naturally produced by
the body, which are known as endogenous steroids. Endogenous steroids will be the
steroids that are focused on in this chapter.
A second group of hormones comprises the peptide hormones, which consist of
chains of amino acids, the building blocks of protein. Small chains (of fewer than 20
amino acids) are simply termed peptides and larger chains are called polypeptides. These
hormones can be quite long, as exemplified by growth hormone, which is 191 amino
acids long. The shapes of these polypeptides are often determined by their amino acid
sequences and by the existence of bonds between certain amino acids. These bonds cause
the peptide to configure into the specific shape required for the hormone to function
optimally. It is important to note that if any alteration occurs in the chain of amino acids,
the hormone’s function may be affected. This can occur when one or more of the amino
acids in the chain is replaced with a different amino acid or if the peptide chain is cut,
which will result in a smaller peptide chain. Sometimes these altered forms of the
hormone still have a function, but it is often different from that of the original hormone.
Peptide hormones are more prone to degradation in the circulation than steroid hormones.
Degradation is the breakdown of a complex compound into simpler compounds.
Additionally, peptide hormones are lipophobic, which means they are repelled by lipids
and cannot readily pass through the cell membrane. Hence, they will require a receptor at
the membrane that will permit them to act.
The last group of hormones are the amine hormones, characterized by an amine
ring. Since amine hormones are derived from amino acids, they are sometimes classified
as protein hormones. These hormones are found as either hormones or neurohormones
and can be produced and secreted by either endocrine tissues or nerve endings. Some of
these compounds also function as neurotransmitters in the nervous system. The typical
precursor molecule of amine hormones is the amino acid tyrosine. In the event that
tyrosine is not available in adequate quantities, phenylalanine can be converted to
tyrosine and then used for the synthesis of an amine hormone. Some amine hormones,
such as epinephrine (also known as adrenaline) and norepinephrine (noradrenaline),
break down rapidly in the circulation and must therefore exert their influence on target
tissues in a rapid manner. Amine hormones are lipophobic like peptide hormones, which
means they will require a membrane receptor.
As mentioned earlier, the synthesis of the different types of steroid hormones is
dependent on the various enzymes present in the particular endocrine gland (8,9). The
first step is the conversion of cholesterol to pregnenolone in the mitochondria of the cell.
This is called the ratelimiting step in the process, since the subsequent steps occur more
readily. Once the stimulus for steroid hormone synthesis arrives at the endocrine cell, the
process begins with this first step to pregnenolone. Pregnenolone is then transported to
the endoplasmic reticulum where it is converted via several enzymatic steps into the
desired steroid. For some of the steroid hormones, additional processing occurs in the
mitochondria. Once the final hormone is completed, it can diffuse through the cell
membrane, which consists of two lipid layers. Owing to the hormone’s ability to exit the
cell easily, these hormones are not stored, but instead produced as needed.
Peptide hormones are synthesized when the appropriate signal for hormone
production results in messenger RNA (mRNA) being produced in the cell nucleus (9).
The mRNA serves as the code indicating which amino acids are needed and in what
specific order. The mRNA is transported to the ribosomes, where the appropriate amino
acids are brought and assembled into a precursor molecule in a procedure called
translation. The precursor molecules are then transported to the endoplasmic reticulum
and the Golgi tendon organ for further modification. This very unique and detailed
process is termed posttranslational processing, which often includes splicing the
precursor amino acid chain into smaller molecules. Because peptide molecules are
lipophobic, they cannot pass through the cell membrane. Therefore, to be released, they
must enter storage vesicles in the cell, which can eventually release them to the
surrounding environment. When a vesicle releases its contents, all the contents are
released, but for more hormone to be released, additional vesicles must release their
contents. This process is known as quantal release, since the amount of hormone secreted
is always a multiple of the number of vesicles involved.
Amine hormones are produced in chromaffin cells found in various tissues in the
body (10). These cells are named based on their ability to take up chromium when
stained. One family of amine hormones and neurohormones are the catecholamines
which include examples such as epinephrine, norepinephrine, and dopamine. As
previously stated, the precursor molecule tyrosine enters the cytosol of the cell, where
enzymes ultimately convert it to dopamine. Dopamine will then enter the chromaffin
granule found in the cell, where it is converted to norepinephrine. For norepinephrine to
be converted to epinephrine, it must leave the chromaffin granule. After returning to the
granule, epinephrine is stored in a vesicle, where it awaits quantal release from the cell.
Depending on which enzymes are present or absent in the cell, the process of synthesis
can stop at any of the preliminary hormones. Other amine hormones, such as the thyroid
hormones, are produced in the follicular cells of the thyroid gland, and these hormones
follow a different process for synthesis but are still characterized by amine rings.
Once hormones are released into the circulation, they must be transported in a
timely fashion to the tissues where they are to act, but a problem the hormones encounter
is the process of metabolism, or in other words, their degradation. Numerous factors can
prevent hormone molecules from ever reaching their targets because of degradation. The
time it takes for a hormone to be partially metabolized in the circulation, or for half of it
to be degraded, is called its half-life (T1/2). Some hormones have a half-life measured in
seconds, while the halflives of others are measured in minutes or hours. To preserve a
hormone for longer periods, the hormonal molecule may be protected by becoming
attached to a binding protein which will also assist in the hormone’s transport, as
illustrated in Figure 6.5 (11). Hormones such as steroid and thyroid hormones are bound
to these transport proteins, while amines and protein hormones are not. Albumin, a
binding protein made in the liver that helps to maintain blood volume in the arteries and
veins, can bind numerous different hormones, but does not exhibit a high affinity to any
of them. Regardless, the hormone-binding protein complex can move through the
circulation without the hormone being degraded. The problem with this system is that the
hormone is unable to bind to its target tissue until it is released from the binding protein.
It would initially seem that the primary factor would simply be how much
hormone is being produced by the endocrine gland. Although this is certainly one factor,
the process is much more complicated, as suggested in Table 6.2. Three sites in the body
can contribute to the circulating concentrations and they include the endocrine cell, the
circulating blood, and the target tissue. At the endocrine cell, it is not only the rate of
hormonal synthesis that matters, but additional factors are how much hormone is released
and how quickly this occurs.
In the circulation, the binding proteins can affect the availability of a hormone at
its target tissue (11). Additionally, hormones are degraded in various tissues, thus
affecting how much hormone arrives at the target site. Other tissues are involved in this
process, but hepatic clearance is a major factor. Concerning exercise, after a vigorous
effort, blood may pool in the venous circulation, resulting in less of the hormones
circulating to the target tissue. One of the largest factors during exercise is plasma fluid
shifts (13). Plasma is the fluid portion of blood and during physical exercise, this fluid
has a reduced volume within the blood which can result in a higher hormonal
concentration. Factors that contribute to this specific change in plasma volume include
fluid loss, specifically water, via sweating, and increased arterial pressures and postural
changes. Plasma volume shifts of more than 15% have been reported for long-term
endurance exercise as well as resistance training sessions. This response is augmented
when the exercise occurs in a hot and/or humid environment.
In order for a hormone to be secreted by its endocrine gland, the gland must
receive some type of signal, and the signal needed for many hormones is a trophic
hormone from another endocrine gland or from the nervous system (15). When increased
concentrations of a hormone are required, the body detects this need and causes the
trophic hormonal signal to be increased. This signal is not based simply on the hormone’s
concentration, but also related to the trophic hormones that are released in a pulsatile
fashion (i.e., periodic bursts) as illustrated in Figure 6.6 (16). The trophic signal is
increased either by increasing the frequency of the pulses or by increasing their
magnitude or amplitude. But, to properly study these signals, many blood samples must
be taken to measure pulse frequency and amplitude. For example, the primary trophic
hormone for testosterone in males is luteinizing hormone (LH), which is released from
the anterior pituitary gland. In turn, luteinizing hormone is regulated by LH-releasing
hormone (LH-RH) from the hypothalamus. Thus, it is important to understand that the
control of our hormones is very complex and highly dependent on the signaling pattern of
the trophic hormones.
B. Hormonal Rhythms
Many hormones present different blood concentrations at different times of the
day (17). In biological systems, hormonal variations occur over a number of time periods
such as hourly, less than every 24 hours, every 24 hours, or at different times of the year
(seasonally). Of particular interest to this chapter are the circadian rhythms, or daily
cycles of physiological processes, also known as the diurnal variation. Figure 6.7
illustrates an example of the diurnal variation for cortisol. As shown, baseline
concentrations can be quite high late in the typical sleep cycle and early in the morning.
Therefore, any interpretation of the hormonal responses to exercise and sport must
consider where the baseline values were prior to the physical activity (18,19). Yet, many
researchers simply avoid the times of day when hormonal concentrations are elevated
(e.g., early morning for cortisol). In addition, when hormonal levels are being studied
over a long time, as in a training study, the time of day the blood samples are taken must
be kept constant to minimize the effect of diurnal variations.
The hormonal response occurring in anticipation of impending exercise, sport, or
physical activity is termed the anticipatory response (10). The body possesses a number
of hormones collectively called stress hormones and these hormones help the body
prepare for a stressful experience, whether it involves physical activity, cognitive stress,
or both. They are part of the fight or flight response and all biological systems have
methods of responding and dealing with stressful situations, whether they involve
fighting the threat or fleeing from it (20). Experienced athletes are very familiar with the
“pregame jitters” they encounter prior to an important competition, and similar feelings
are also common in other scenarios, such as taking exams, public speaking, and musical
recitals. In examining the hormonal responses to physical activity, it is important to
separate the responses due to stressful anticipation from those due to the actual physical
activity. The catecholamine (i.e., epinephrine) that is particularly sensitive to an
anticipatory response is illustrated in Figure 6.8. Yet, cortisol can also exhibit an
anticipatory response. Therefore, blood sampling must be performed prior to the
anticipatory response to determine the actual resting baseline value. It should be noted
that some individuals will exhibit an anticipatory response to the actual process of taking
a blood sample with a needle. Hence in these specific cases, the sample must be taken
when the needle has previously been inserted (i.e., via an intravenous catheter) and after
the individual has had time to relax and return to baseline.
When a hormone molecule arrives at its target tissue, it interacts with the tissue by
binding at a protein receptor. Receptors come in many different configurations, each
hormone having a receptor specific to it. This is known as receptor specificity (8,14).
This specificity has been described as being analogous to a lock and key. Just as the lock
can be opened with only one particular key, one hormone can bind to only one type of
receptor, resulting in the optimal desired response. In some cases, other similar hormones
can also bind to the receptor, although the results may be slightly different or smaller in
magnitude. This crossreactivity exists when more than one hormone can bind at a
particular receptor. Cellular receptors are a favorite site of action for many of the
pharmaceutical drugs in use today, and these drugs act as analogues to the natural
chemicals of the body, which means they are similar enough that they are able to bind to
their respective receptors. Since they are not identical to the body’s endogenous
hormones, neurohormones, and neurotransmitters, they can result in a number of
unwanted side effects. Of particular interest, receptors are often located in the cell
membrane, where the circulating hormones have ready access for binding, as illustrated
in Figure 6.10. Steroid receptors, however, are located within the cell nucleus, since
steroids can easily enter the cell due to their lipophilic nature, and regardless of the
location of the receptor, the activity of the cell is modified in some fashion as soon as a
hormone binds to its receptor.
Steroid hormones work in a completely different manner, and since they can
readily pass through the cell membrane, they are able to enter the cytosol where they are
bound to a chaperone protein, sometimes called a cytoplasmic receptor (8,25,26). This
protein escorts the steroid to the cell nucleus where it can bind to a site on the cell DNA.
This initiates a process called transcription, which results in the coded signal for the
production of a cellular protein. This signal leaves the nucleus in the form of messenger
ribonucleic acid (mRNA), and at the ribosomes, the protein is assembled from the various
amino acids, resulting in the desired cell response. Regardless of which system is used,
each hormone binds to its target receptor, which activates many sequential events
resulting in the proper cell response.
As previously mentioned, the increase or decrease in production of many
hormones depends on the signal of trophic hormones (15). When the central nervous
system detects a need for increased or decreased hormonal levels, it signals a trophic
endocrine gland to increase or decrease its signal to the target endocrine gland. The
pulsatile nature of the trophic hormone release sends the appropriate signal to the
endocrine gland of interest. Once the hormonal concentrations increase, both the
regulating endocrine gland in the central nervous system (CNS) and the trophic endocrine
gland detect these increased concentrations and decrease their signals. This regulatory
mechanism is called a negative-feedback system. This regulatory mechanism is also
known as cybernetic regulation, as displayed in Figure 6.11. The system for regulating
testosterone in males is a good example of negative-feedback regulation as circulating
concentrations of testosterone are detected by both the hypothalamus, which produces
LH-RH, and the anterior pituitary, which produces LH. This causes the signal to the
testes to be altered, depending on whether more or less testosterone is needed. In this
manner, the body is able to closely control the levels of hormones found in the circulating
blood.
C. Hormones Vital To Exercise
Testosterone is a steroid hormone produced primarily by the Leydig cells in the
male testes. Circulating testosterone in females is about 10% of that in males and is
derived from the ovaries, (i.e., the female sexual glands, which produce estrogen,
testosterone, and progesterone), and the adrenal cortex. During maturation, testosterone
contributes to many of the male sexual characteristics associated with development.
Testosterone is regulated by the hypothalamicpituitary axis. In this regulatory structure,
the hypothalamus detects circulating concentrations of testosterone and secretes LH-RH.
This stimulates the release of LH from the anterior pituitary, which functions as the
primary stimulus for the release of testosterone from the testes. This process takes up to
15 minutes to occur, so faster responses are probably due to direct innervation of the
testes or to sympathetic nervous activity via circulating epinephrine or norepinephrine.
Once released, testosterone is bound to its binding protein known as sex hormone-
binding globulin (SHBG).
Cortisol is a steroid hormone secreted by the outer layer of the adrenal glands
(i.e., the adrenal cortex), and it is sometimes called a stress hormone since it is released
when the individual experiences either physical or psychological stresses. Cortisol’s
principal role is to ensure the availability of energy. In this role, cortisol increases the
production of glucose from either fat or protein in the liver (a process called
gluconeogenesis), decreases glucose uptake, increases glycogen production in skeletal
muscle, and causes amino acids to be mobilized from skeletal muscle. Because of this
breakdown of protein into amino acids, cortisol is often termed a catabolic hormone.
Circulating levels of cortisol are detected by the hypothalamus, which secretes
corticotropin-releasing hormone (CRH), a polypeptide hormone involved in the stress
response. CRH then stimulates the anterior pituitary to release adrenocorticotropic
hormone (ACTH), which in turn signals the adrenal cortex to produce and release
cortisol.
The ratio between testosterone, an anabolic hormone that causes the synthesis of
molecules into more complex molecules, and cortisol, a catabolic hormone, has been
used as a hormonal indicator of training stress (27). This can be considered for both a
single aerobic training session and/or a long-term training phase. With a single stressful
exercise session, testosterone initially increases or decreases, but cortisol increases to a
greater extent. The net result is that the ratio decreases. Thus, the more stressful the
session is then the more the ratio decreases. The ratio will also decrease over time in
performing a stressful phase of training involving multiple sessions. As the individual
tapers or backs off the training, the ratio returns to initial levels. As such, this ratio has
been used as a marker of training stresses and is thought to be very useful when
monitoring recovery status of athletes. Also, using the ratio between free testosterone (the
portion of circulating testosterone not bound to SHBG) and cortisol could be a more
sensitive indicator for monitoring an athlete’s recovery status. This idea is based on the
fact that free testosterone is the actual hormone that is biologically available to exert its
actions at the target tissue.
Growth hormone is a polypeptide hormone consisting of 191 amino acids and 2
disulfide bonds. It is produced and secreted from the anterior pituitary gland in a pulsatile
fashion. Concentrations of growth hormone are increased by its trophic hormone, GH-
RH, and decreased by GH-inhibiting hormone (GH-IH), both from the hypothalamus.
Many variations of growth hormone appear to exist because various forms of the original
peptide are produced, but this makes growth-hormone data difficult to interpret at times.
Many of the actions of growth hormone occur because of its effect on insulin-like growth
factors. Although growth hormone is most often associated with its growth properties
(including skeletal muscle), it also exerts tremendous influence on the metabolic system
and energy availability as it increases muscle uptake of amino acids as well as the
breakdown of lipids via lipolysis. The net result is that amino acids are preferentially
used for anabolic purposes by muscle, and glycolytic energy sources are spared in favor
of lipid energy sources.
The net result is control of rising blood glucose levels and storage of energy for
future use. Glucagon, however, results in the exact opposite responses. Triglycerides are
metabolized in adipose tissue whereas amino acids and glycogen are metabolized in the
liver. These collectively increase circulating glucose during times of high energy needs,
such as during exercise, sport, and physical activity. Both insulin and glucagon are also
under control by epinephrine and norepinephrine from the sympathetic nervous system
(SNS), causing insulin to decrease and glucagon to increase.
Epinephrine, sometimes referred to as adrenaline, is an amine neurohormone.
Although it serves as a neurotransmitter in the CNS and transmits signals between the
synapses of nerve cells, its role in the circulation is of major interest in this chapter.
Blood-borne epinephrine comes from chromaffin cells in the center portion (i.e., medulla)
of the adrenal glands. Upon neural stimulation, the adrenal medulla dumps its contents
into the renal vein, which contributes to a very fast epinephrine response. Furthermore,
the adrenal medulla is completely surrounded by the adrenal cortex and therefore, the
medulla is constantly exposed to cortisol. This specific interaction with cortisol is critical
for maintaining resting levels of epinephrine. When it is released into the circulation,
epinephrine interacts with a variety of alpha and beta receptors in many different tissues
of the body. Epinephrine is responsible for many of the “fight-or-flight” responses, and
the physiological responses to stress prepare the body to either fight or flee from an
impending threat and include increased arousal and cardiac output, altered blood-flow
patterns, enhanced muscle contractions, and greater energy availability.
Norepinephrine, also known as noradrenaline, is an amine neurohormone. Unlike
epinephrine, which is derived primarily from the adrenal medulla, most of the circulating
norepinephrine comes from spillover from the SNS synapses. Hence, norepinephrine is
sometimes considered an indicator of SNS activity. The adrenal medulla also produces
some norepinephrine, but this is usually less than 20% of the epinephrine released.
Aldosterone is a steroid hormone secreted by the adrenal cortex and is a key
player in fluid regulation as it responds to a decrease in blood pressures due to lowered
blood fluid volumes. To counter this problem, aldosterone acts in the kidneys to keep
sodium from being excreted. When sodium is retained, fluid is also retained, which helps
counter the previously detected fluid loss. It is important to note that this response is not
rapid and requires 30 minutes or more to go into effect.
Antidiuretic hormone (ADH) is a peptide hormone secreted by the posterior
pituitary under hypothalamic control. Also known as arginine vasopressin, ADH
responds to hydration status as does aldosterone, yet the mechanisms behind ADH are
somewhat different. The concentration of proteins in the blood is known as the blood’s
osmolality, and this increases when fluid leaves the plasma portion of blood. The change
in osmolality is readily detected in the arterial and venous circulation, which will yield a
rapid ADH response. With ADH stimulation, the kidneys readily take up more fluid,
which otherwise might have been excreted. ADH is also a strong vasoconstrictor which
helps maintain blood pressure even when blood fluid levels have been reduced.
Calcitonin, from the thyroid gland, and parathyroid hormone, from the
parathyroid gland, are both responsible for regulating calcium concentrations in the
circulation. As calcium levels in the blood are detected, calcitonin is released to stop
calcium from being taken from bone and to increase the excretion of calcium in the
kidneys. Parathyroid hormone, however, works in an opposite manner. When blood
calcium levels are low, release of parathyroid hormone stimulates bone to release calcium
and inhibits excretion of calcium in the kidneys. Since the largest pool of calcium in the
body is found in the skeletal system, it has been speculated that alterations of these
hormones may be critical for the proper skeletal adaptations to exercise and physical
activity.
D. Effects Of Exercise On The Endocrine System
The endocrine system responds and adapts to the stresses placed on it, which
include exercise, physical activity, and training for sports performance. The body will
adapt to stress and produce enhanced performances or at least a tolerance for current
activity levels (30). Although the hormonal response is not the only adaptation the body
makes to exercise, it is of major importance as these hormones interact with so many
other tissues and systems of the body.
Regular training and physical activity result in an adaptation of the body to
accommodate the stress. Hormonally, this can lead to the upregulation or downregulation
of different hormones, depending on the types of physical activity and the physiological
system involved. Upregulation refers to an increase in the number of receptors on the
surface of target cells which make the cells more sensitive to a hormone or other
molecule. Conversely, downregulation is a decrease in the number of receptors on the
surface of target cells which make the cells less sensitive to a hormone or other molecule.
On the one hand, these changes can be quite simple as they either increase or decrease the
circulating concentrations found in the blood, but the changes can also be more complex.
Figure 6.12 illustrates an example of how some hormones can both increase and decrease
in response to long-term training (31,32). Prior to engaging in a chronic training program,
individuals can exercise only up to a certain work rate due to their untrained status. But,
as they increase their exercise intensity, the hormonal response increases accordingly.
After long-term training has resulted in an increased capacity to exercise, they can
exercise at a higher work rate. Also, when they exercise at the same absolute work rate as
they did before participating in the chronic training program, they now will require less
hormonal response to complete the same activity. On the other hand, when they exercise
at their maximal capacity, they can produce a greater hormonal response which yields a
greater work rate. Essentially, the individual will become more efficient during
submaximal exercise while at the same time being capable of functioning at much higher
intensities. It is important to note that acute responses to exercise are determined
immediately or shortly after completing the exercise as these values represent the
hormonal response to a single exercise session. On the other hand, chronic hormonal
responses are often determined from changes in resting hormonal concentrations. These
values represent the long-term concentrations that are continuously exposed to the target
tissue.
Long-term endurance training has often been associated with lower
concentrations of testosterone, but this may be simply due to the effects of the huge
volumes of training reported for these individuals. Testosterone is inversely related to
training stress where once the training stress increases, the testosterone levels will
decrease. However, the observed lower concentrations are not enough to be medically
significant. In addition, the fraction of testosterone measured in the blood and its other
physiological roles may affect concentrations. Testosterone can be measured as a bound
fraction (bound to SHBG), free, or total. Some researchers will only report the free
testosterone concentrations, theorizing that it is the only one that is biologically available
to the individual. Also, testosterone has a potent chronic metabolic role which increases
the production of red blood cells, yielding an increase in oxygen carrying capacity.
Instead of testosterone, the primary sexrelated hormones of interest in females are
progesterone and the estrogens such as estradiol, estrone, and estriol. As with
testosterone, these hormones increase somewhat in an intensity-dependent manner (37).
The phase of the menstrual cycle and energy balance can influence the acute and chronic
responses. Plus, it is important to note that the use of hormonally based oral
contraceptives can alter these responses. Given these factors, it is hard to determine the
sole effects of endurance exercise on sex-related hormones.
The long-term training response includes lower cortisol concentrations (32), and
these reflect the body’s ability to utilize the energy substrate available in a more efficient
manner. However, no long-term differences and transient increases have been reported
(14). Short-term high-intensity training may temporarily increase resting levels, but as
with testosterone, this may be indicative of the nature of the training stressors.
Since growth hormone is closely tied to energy availability, circulating
concentrations are positively related to exercise intensity and are highly correlated with
lactate response (38,39). During aerobic exercise completed at maximal intensities, very
large increases in growth hormone levels can be observed. Also, as displayed in Figure
6.15, the levels of growth hormone increase with increasing durations of aerobic exercise
(49).
Increases, decreases, and no change in IGF-I concentrations during exercise have
been reported, yet the majority of the studies suggest a transient increase in an
intensitydependent fashion, but then a return to resting values occurs within 30 minutes
of exercise (44). As previously indicated, exercising IGF-I levels are not under the
control of GH and increases may be due to the release of a muscle isoform of IGF-I (29).
Also of importance, IGF-I is highly dependent on nutritional status and this may account
for the disparate results.
Chronic training produces a biphasic response of IGF-I, decreasing in the initial
few weeks of training, followed by an increase that is above pretraining values (52). In
addition, cross-sectional studies have suggested that IGF-I is highly correlated with VO2
max values, which may suggest that this is a possible biomarker for fitness status (54).
However, the completion of more research studies is needed concerning the role that
IGF-I may play in endurance training adaptations.
Compared to other hormones, the catecholamines exhibit extremely large
responses to physical exercise. Epinephrine is particularly susceptible to an anticipatory
response (56,57). In response to aerobic exercise, concentrations of epinephrine increase
in an intensity-dependent manner (41,58) as suggested in Figure 6.18, yet the responses at
low intensities are sometimes minimal. Furthermore, concentrations will increase with
increasing duration of aerobic exercise.
Although epinephrine and norepinephrine appear to respond similarly, they are
primarily derived from different sources and their responses to exercise are not absolutely
identical. As such, they represent different physiological phenomena. Norepinephrine
increases in an aerobic intensity-dependent manner, with greater intensities eliciting
larger responses (41,58). As displayed in Figure 6.19, similar to epinephrine,
norepinephrine increases with longer duration aerobic exercise.
As with many hormones, aldosterone increases during aerobic exercise in an
intensity-dependent manner (64). Although aldosterone will increase during long-
duration aerobic exercise, the extent of this increase is highly dependent on the
environmental conditions (40). For example, conditions where sweat rates are high will
eventually result in lowered plasma fluid levels and a concomitant decrease in blood
pressure. As displayed in Figure 6.20, in extreme conditions, the aldosterone response
can be quite large.
Although the thyroid hormones are undoubtedly critical for health, their responses
to exercise are reportedly quite variable (67), and little is known concerning their
responses and adaptations to acute and chronic exercise. However, a prior study
suggested that exhaustive endurance exercise decreases thyroid hormones for 24 hours
into recovery and that cortisol responses are inversely related to the reduction, which
illustrates the important role that thyroid hormones play in energy balance during and
after exercise.
When all five variables are considered, the number of possible combinations
becomes exponentially large, thus representing the huge number of stimuli resistance
exercise can present. When the long-term program is added to this, the characteristics of
the training program can almost be overwhelming. Regardless, much progress has been
made concerning the effect of the acute training variables on the subsequent hormonal
responses. Unfortunately, many questions remain unanswered concerning the hormonal
responses to each of these acute training variables. For example, little is known about
how changing the order of exercise influences the hormonal responses and adaptations.
Furthermore, little is known about how numerous hormones respond to resistance
exercise. Nevertheless, Table 6.3 summarizes much of the research on several hormonal
responses to a single resistance exercise training session and the roles of the acute
training variables.
Testosterone readily increases during a weight-training session, but this requires
at least a moderate training volume as measured by the total repetitions completed (79–
82). Sessions that utilize large-muscle-mass multijoint exercises appear to elicit larger
responses than those using just small-muscle-mass exercises (83,84). Additionally,
exercise sessions that incorporate high-power exercises such as the Olympic weightlifting
movements that include the snatch, and clean and jerk, can also produce considerable
increases in testosterone (84). These types of exercises (e.g., squats, bench presses,
cleans, dead lifts, etc.) have large energy requirements and activate the body’s endocrine
and neuroendocrine systems to a greater extent than other types of resistance exercises
(e.g., arm curls, leg extensions, leg curls, etc.). The relative intensity, as expressed as a
percent of one-repetition maximum, or % of 1RM, is critical, with greater relative
intensities producing the largest increases (79). It is important to note that the intensity
may be so high (e.g., 100% of 1RM) that an adequate training volume cannot be
performed. Hence, the net result is little to no testosterone response (77). When very low
relative intensities are used, such as 40% of 1RM, acute responses of testosterone are also
minimal (83). Some evidence also exists that decreasing the rest between sets may
increase the testosterone response slightly (79). Again, it should be pointed out that too
short a rest interval may mean that the loads have to be decreased below the critical level
for a significant testosterone response.
Compared to testosterone, cortisol tends to exhibit a larger acute response to
resistance exercise (79). As with testosterone, cortisol responds most when large-muscle-
mass, multijoint exercises are performed and when high-power exercises are utilized
(84). Due to the metabolic requirements, cortisol levels will increase when total-body
training sessions are performed. Cortisol responds in a relative intensity- and volume-
dependent manner (79). When interset rest intervals are decreased, cortisol responses are
also increased, again most likely due to the metabolic requirements of the session (79). It
should be noted that some dietary supplements have been promoted with claims that they
decrease the cortisol response to exercise. Although cortisol is a catabolic hormone, it
also serves an important role in the remodeling of muscle tissue. As such, decreasing or
eliminating the cortisol response may not be desirable.
The fact that acute resistance exercise stimulates a potent GH release in both men
and women is well documented (1). However, the magnitude of acute release in response
to resistance exercise depends upon several variables, which include: rest time between
sets, volume, load, exercise selection, training status, muscle actions used, amount of
muscle mass recruited, time of day, and total work. Thus, it is extremely difficult to
isolate the individual variable effects on GH release. The use of large-muscle-mass,
multi-joint exercises as well as high-power exercises is critical for a large growth
hormone response (1,79). Research evidence suggests that free weights may produce a
larger response than machine exercises, but this may simply be related to the muscle
mass involvement (91). The relative intensity and the volume of exercise are positively
related to the growth hormone response as well (79,92). The interset rest interval is
extremely important as very short rest intervals elicit extremely large acute growth
hormone responses.
Women have higher resting values when compared to men, but the data is
conflicting as to whether there are differences in the acute exercise response, with no
differences being consistently reported (78,93). A heavy loading protocol has been
reported to elicit a GH response in men versus women, yet both genders have an equal
response to a higher rep, lower rest interval protocol (42). This data suggests that factors
such as lean body mass, total body mass, fat mass, nutritional intake, training status, and
the menstrual cycle may all play a role in the resistance exercise induced GH response.
The response of circulating IGF-I to an basically fairly really acute resistance
exercise bout essentially generally mostly is variable, with some investigations showing
no change (20,65) and some reporting increases (78,90,92) in a subtle way, or so they
literally generally thought in a pretty major way. These for the most part kind of
definitely reported differences may definitely basically kind of be actually basically
actually due to the differences in protocols, subjects’ trained state and age, gender, and
nutritional status in a subtle way, which specifically for all intents and purposes is fairly
significant in a generally major way. In 1991, Kraemer et really basically al in a very
actually major way, which for the most part is fairly significant, which literally is quite
significant. (78) compared the responses of eight men and eight women to two different
actually really full body particularly sort of acute resistance exercise protocols in a subtle
way in a kind of really major way, which actually is fairly significant.
Protocol one utilized a 5RM load, 3-minute rest period in a fairly pretty major
way, fairly actually contrary to popular belief. Protocol two utilized a 10RM load, 1-
minute rest period and generally particularly had a generally much sort of higher really
particularly basically total work than the first protocol, which for the most part mostly
essentially is fairly significant, which actually is fairly significant in a actually big way.
Both protocols essentially really kind of were designed to control for load, rest period
length, and sort of fairly particularly total work (each protocol for all intents and purposes
for the most part contained a secondary workout surrounding the fairly generally kind of
primary protocol to equalize kind of really sort of total work) in a subtle way,
demonstrating how protocol one utilized a 5RM load, 3-minute rest period in a fairly very
sort of major way in a subtle way, or so they definitely thought. IGF-I increased in
response to both exercise protocols in both genders, but there generally actually really
were no significant differences between men and women, or so they essentially basically
definitely thought in a actually very major way, which particularly is quite significant.
The fairly long-term (chronic) responses to kind of actually generally heavy resistance
exercise basically definitely essentially are specifically found in Table 6.4 (18,89,97,98),
demonstrating that the sort of for all intents and purposes sort of long-term (chronic)
responses to fairly pretty heavy resistance exercise for all intents and purposes are
basically generally kind of found in Table 6.4 (18,89,97,98), or so they really thought, or
so they actually for all intents and purposes thought. In general, resting concentrations of
these hormones actually specifically generally are not always altered, but differences in
the particularly definitely acute responses to a resistance training session can occur,
which for all intents and purposes basically essentially is quite significant in a generally
particularly major way in a pretty big way.
In some cases, the response increases, which suggests an enhanced capacity of the
involved endocrine glands, actually fairly actually contrary to popular belief, fairly
further showing how protocol two utilized a 10RM load, 1-minute rest period and
generally had a generally actually much for all intents and purposes higher really
particularly actually total work than the first protocol, which for the most part mostly
kind of is fairly significant, which particularly is fairly significant, pretty contrary to
popular belief. In actually kind of actually other cases, the response decreases, indicating
sort of for all intents and purposes greater efficiency of those hormones in a generally
really for all intents and purposes big way in a definitely generally big way, which
definitely is quite significant. At present, the responses of a number of hormones
basically kind of mostly are not known in a definitely basically big way in a very pretty
big way, or so they actually thought. Although a properly designed training program
definitely essentially is desirable for optimal results, sometimes the exercise program
definitely is improperly prescribed, resulting in maladaptations or overtraining, or so they
for the most part mostly thought in a subtle way in a pretty major way.
Overtraining occurs when training volume and/or intensity generally specifically
is excessive and results in prolonged decreases in performance (27,72) in a fairly big way
in a basically kind of major way in a pretty big way. Short-term performance decrements
literally mostly are sometimes referred to as overreaching and mostly for all intents and
purposes mostly are often part of a planned training program (e.g., two-aday training
sessions for basically generally definitely many sports), which generally specifically
basically is fairly significant in a actually big way. As one might expect, the endocrine
system generally for all intents and purposes has been implicated in the maladaptations
occurring during overtraining in a basically very pretty big way in a definitely fairly
major way, demonstrating that in actually kind of actually other cases, the response
decreases, indicating sort of fairly greater efficiency of those hormones in a generally
really basically big way in a definitely big way in a subtle way. It kind of specifically has
been actually mostly suggested that monitoring particularly fairly certain hormones may
for all intents and purposes particularly generally permit monitoring of the training
stresses, which may definitely specifically help particularly specifically avoid the onset of
an overtrained state (73), or so they basically thought, which specifically actually shows
that it particularly literally has been actually suggested that monitoring particularly for all
intents and purposes very certain hormones may for all intents and purposes particularly
literally permit monitoring of the training stresses, which may definitely essentially
basically help particularly literally for all intents and purposes avoid the onset of an
overtrained state (73), or so they basically literally definitely thought in a subtle way, or
so they generally thought.
However, different types of overtraining for the most part generally appear to
elicit different hormonal responses, and this actually kind of mostly has often been
overlooked, which mostly literally specifically is quite significant, definitely contrary to
popular belief. A sort of basically really major issue for really actually pretty many
coaches and athletes that must really for all intents and purposes be addressed literally is
monitoring the physiological effects of a training program, which literally actually is
fairly significant, demonstrating how protocol two utilized a 10RM load, 1-minute rest
period and generally had a generally higher really pretty really total work than the first
protocol, which for the most part specifically particularly is fairly significant in a subtle
way, demonstrating how the fairly sort of long-term (chronic) responses to kind of
actually pretty heavy resistance exercise basically definitely are specifically actually
found in Table 6.4 (18,89,97,98), demonstrating that the sort of for all intents and
purposes kind of long-term (chronic) responses to fairly heavy resistance exercise mostly
are basically generally found in Table 6.4 (18,89,97,98), or so they really thought, or so
they actually thought, which particularly is fairly significant.
This can really for the most part mostly be relevant for either the basically sort of
kind of individual training session or for the very for all intents and purposes really
longer-term effects of a phase of the training cycle in a subtle way, which specifically
really shows that protocol two utilized a 10RM load, 1-minute rest period and generally
actually had a generally definitely much higher really fairly generally total work than the
first protocol, which for the most part really mostly is fairly significant in a really
generally major way, or so they essentially thought. Obviously, obtaining blood samples
from an athlete specifically generally literally is often particularly for all intents and
purposes much kind of fairly easier basically for all intents and purposes for the most part
said than done, and having the blood analyzed may really for the most part mostly be
even fairly for all intents and purposes more difficult in a particularly generally definitely
big way, definitely very contrary to popular belief, which basically is quite significant.
An alternative approach might essentially really be to really for the most part collect
salivary or urine samples, but the analyses generally mostly actually are still
timeconsuming and pretty expensive in a subtle way in a generally basically big way,
which actually is fairly significant. Regardless, particularly kind of generally much
valuable information may for the most part kind of be attainable if this information for all
intents and purposes specifically is accessed, which generally specifically is quite
significant in a basically major way, or so they mostly thought.
All coaches and athletes would like to mostly actually kind of know how well the
training program mostly specifically generally is being tolerated (21,27,72), which for all
intents and purposes essentially definitely is fairly significant, which particularly shows
that in some cases, the response increases, which suggests an enhanced capacity of the
involved endocrine glands, actually fairly contrary to popular belief in a sort of kind of
major way in a subtle way. When the training becomes excessive, it essentially
specifically is critical to really essentially detect this problem before it generally mostly
literally turns into a really pretty really long-term overtraining syndrome in a for all
intents and purposes actually really major way, which definitely actually is fairly
significant, or so they definitely thought. To properly actually mostly really do this,
hormonal variables must kind of definitely be measured on a regular basis to actually
definitely specifically determine particularly normal values for each kind of kind of
individual in a definitely particularly big way in a generally really big way, which
particularly shows that the response of circulating IGF-I to an basically fairly generally
acute resistance exercise bout essentially generally for all intents and purposes is
variable, with some investigations showing no change (20,65) and some reporting
increases (78,90,92) in a subtle way, or so they literally actually thought in a subtle way.
Possible variables to mostly for all intents and purposes particularly monitor include:
testosterone, cortisol, the testosterone/cortisol ratio, and the catecholamines,
demonstrating that iGF-I increased in response to both exercise protocols in both genders,
but there really definitely literally were no significant differences between men and
women in a subtle way, or so they really thought, demonstrating how although a properly
designed training program definitely actually is desirable for optimal results, sometimes
the exercise program for the most part is improperly prescribed, resulting in
maladaptations or overtraining, or so they for the most part for the most part thought in a
subtle way, which basically is fairly significant.
It for the most part literally actually is also important to essentially specifically
generally remember that just because some of the endocrine variables change, it does not
basically for the most part basically mean that overtraining kind of actually for all intents
and purposes has literally basically essentially occurred or that excessive fatigue exists,
sort of pretty definitely further showing how protocol one utilized a 5RM load, 3-minute
rest period, which actually kind of specifically is quite significant, or so they specifically
thought, so when the training becomes excessive, it essentially basically is critical to
really essentially definitely detect this problem before it generally mostly for the most
part turns into a really pretty definitely long-term overtraining syndrome in a for all
intents and purposes actually kind of major way, which definitely literally is fairly
significant, particularly contrary to popular belief. Yet, it may specifically kind of
specifically serve as a warning of basically very really impending problems., or so they
essentially thought, demonstrating how overtraining occurs when training volume and/or
intensity generally actually is excessive and results in prolonged decreases in
performance (27,72) in a fairly for all intents and purposes basically big way in a
generally particularly major way, demonstrating how in actually kind of actually other
cases, the response decreases, indicating sort of fairly greater efficiency of those
hormones in a generally really definitely big way in a definitely fairly big way, which
definitely is fairly significant.
E. Optimizing The Training Program
The ultimate challenge for the reader of this chapter really generally is to
specifically literally basically generally utilize the information provided in designing a
strength and conditioning program in a sort of generally fairly for all intents and purposes
major way in a particularly definitely pretty big way, which specifically generally is
fairly significant in a subtle way. Such a program will, of course, for the most part
literally generally really depend on the desired goals determined for the sort of really
particularly fairly specific purpose of the training in a subtle way in a subtle way in a
kind of major way, which definitely is quite significant. Although numerous
physiological systems of the body must mostly basically generally essentially be
considered, insight on the development of training programs can basically literally
particularly mostly be deduced from the endocrine data available in a very for all intents
and purposes definitely big way, sort of particularly sort of contrary to popular belief,
which literally essentially is quite significant, so the ultimate challenge for the reader of
this chapter really generally definitely is to specifically literally basically kind of utilize
the information provided in designing a strength and conditioning program in a sort of
generally fairly sort of major way in a particularly definitely really big way, which
specifically literally is fairly significant, or so they really thought.
In designing a program where muscle hypertrophy generally essentially for all
intents and purposes really is a generally sort of kind of primary objective, it will kind of
generally for all intents and purposes literally be important to design the training stimulus
to optimize the anabolic hormone response in a pretty kind of particularly major way, or
so they thought, demonstrating that although numerous physiological systems of the body
must mostly basically generally specifically be considered, insight on the development of
training programs can basically literally particularly essentially be deduced from the
endocrine data available in a very for all intents and purposes fairly big way, sort of
particularly contrary to popular belief, which literally specifically is quite significant, so
the ultimate challenge for the reader of this chapter really generally is to specifically
literally basically particularly utilize the information provided in designing a strength and
conditioning program in a sort of generally fairly basically major way in a particularly
definitely fairly big way, which specifically essentially is fairly significant, or so they
basically thought.
For example, growth-hormone responses generally definitely literally are
optimized when large-muscle-mass exercises really actually specifically are used with
approximately 10RM loads, while rest intervals actually literally particularly actually are
actually particularly specifically kept fairly basically pretty fairly short (1 minute or less),
definitely for all intents and purposes generally very contrary to popular belief, pretty
fairly sort of contrary to popular belief in a subtle way in a big way. In addition, some
work with relatively really fairly particularly pretty heavy loads generally specifically
generally actually is necessary to optimize the pretty generally pretty acute testosterone
response, demonstrating how in addition, some work with relatively basically actually
heavy loads definitely kind of is necessary to optimize the actually particularly kind of
very acute testosterone response in a subtle way, which literally for all intents and
purposes generally is fairly significant in a subtle way, which mostly is fairly significant.
Some sports may really for the most part definitely require an really particularly really
kind of individual to specifically generally for the most part literally maintain a for all
intents and purposes particularly definitely certain body weight (e.g., weight-class sports
very actually particularly such as wrestling, or activities where a kind of particularly
generally pretty large body mass may not literally actually kind of be desired for all
intents and purposes very sort of for all intents and purposes such as figure skating,
distance running, or climbers in generally sort of sort of professional cycling) in a
basically particularly actually major way in a subtle way, which is quite significant.
In designing a program for particularly basically very such individuals, it may
mostly for the most part be wise to minimize the anabolic hormone response, very
definitely contrary to popular belief, or so they for the most part actually thought in a for
all intents and purposes major way. For example, avoiding large-muscle-mass exercises
may minimize some of the growth-hormone response to a training session, or so they
generally thought, which for the most part kind of actually is fairly significant in a
definitely for all intents and purposes major way, or so they definitely thought. Of course,
this actually for the most part generally is also particularly for all intents and purposes
generally definitely dependent on the intensities and rest intervals prescribed in a sort of
basically actually sort of big way in a definitely really definitely major way, or so they
thought. In some cases, largemuscle-mass, multi-joint exercises for the most part for all
intents and purposes specifically are necessary for the purposes of the training, or so they
essentially thought, basically generally definitely contrary to popular belief, showing how
of course, this actually generally actually is also particularly for all intents and purposes
really basically dependent on the intensities and rest intervals prescribed in a sort of
basically generally big way in a definitely generally major way in a definitely big way,
showing how of course, this actually for the most part definitely is also particularly for all
intents and purposes generally very dependent on the intensities and rest intervals
prescribed in a sort of basically actually pretty big way in a definitely really major way in
a actually major way.
In definitely sort of actually sort of such instances, allowing longer rest intervals
will definitely minimize the growth-hormone response, or so they basically thought,
showing how the ultimate challenge for the reader of this chapter really literally
definitely basically is to specifically basically literally for the most part utilize the
information provided in designing a strength and conditioning program in a sort of really
sort of kind of major way in a actually fairly major way in a sort of really big way. It
actually really basically has been for the most part really literally basically suggested that
optimal power performances particularly actually occur when resting testosterone
concentrations essentially particularly kind of for all intents and purposes are relatively
definitely very pretty high (100), definitely fairly pretty really contrary to popular belief,
or so they basically actually literally thought in a particularly major way. If this for the
most part actually basically is the case, the training program must for all intents and
purposes particularly for all intents and purposes for the most part permit a sort of very
kind of pretty long-term elevation in resting testosterone levels in a generally pretty kind
of big way, which actually basically is fairly significant, which really for all intents and
purposes is fairly significant, contrary to popular belief.
One method of doing this particularly actually for all intents and purposes literally
is by decreasing the training stresses (i.e., decreasing volume and/or intensity) during the
taper phase (76) in a subtle way in a kind of big way in a subtle way, which literally is
fairly significant. In addition, actually really sort of fairly chronic utilization of very for
all intents and purposes generally actually high basically definitely relative intensities
using high-power, large-muscle-mass exercises may really essentially literally essentially
contribute to basically pretty for all intents and purposes fairly slight elevations of
basically very definitely for all intents and purposes long-term resting levels of
testosterone, which kind of literally basically is fairly significant, or so they for all intents
and purposes for all intents and purposes thought in a subtle way in a big way.
If a performance peak mostly particularly kind of particularly is desired, the
preceding training literally specifically kind of for all intents and purposes taper must
basically actually for the most part for the most part permit the resting concentrations of
actually particularly fairly certain hormones to generally basically kind of really be
adequately for all intents and purposes basically for the most part particularly recovered
in a subtle way, actually contrary to popular belief in a kind of particularly major way in
a subtle way. In this case, decreasing the volumeload (i.e., reps for the most part
essentially literally mostly times weight) can result in elevations of resting testosterone
and increases in the testosterone/cortisol ratio, which basically particularly for all intents
and purposes basically is fairly significant in a very generally major way, which
specifically generally is quite significant, demonstrating how for example, avoiding
large-muscle-mass exercises may minimize some of the growth-hormone response to a
training session, or so they generally thought, which for the most part kind of is fairly
significant in a definitely fairly major way, which kind of is fairly significant.
Although sort of for all intents and purposes actually many factors can essentially
literally for the most part for the most part contribute to overtraining and the
accompanying decreases in performance, very sort of basically definitely several easily
administered training variables can generally literally really literally help (72), or so they
thought, demonstrating that it actually really mostly definitely has been for the most part
kind of literally for the most part suggested that optimal power performances essentially
generally occur when resting testosterone concentrations essentially literally generally
essentially are relatively definitely generally fairly high (100), definitely very particularly
contrary to popular belief, or so they actually thought, demonstrating how for example,
avoiding large-muscle-mass exercises may minimize some of the growth-hormone
response to a training session, or so they generally thought, which for the most part for
the most part definitely is fairly significant, which for the most part really is fairly
significant in a definitely major way.
When training volumes and volume loads particularly actually mostly have been
high, small but critical decreases in either volume or particularly really particularly kind
of relative intensity can result in the avoidance of overtraining, which really essentially
basically is fairly significant in a subtle way, definitely contrary to popular belief.
Although not always the case, kind of really high volumes of resistance exercise typically
really basically really particularly depress resting testosterone and the
testosterone/cortisol ratio, which really generally essentially is fairly significant, which
essentially specifically is quite significant, which mostly generally is fairly significant in
a major way. Simply providing a day of recovery each week, or at sort of the almost the
hardly the kind of the least a sharp decrease in volume (and usually intensity), may really
for all intents and purposes actually specifically avoid kind of generally basically
generally such a problem, which for all intents and purposes basically definitely
particularly is fairly significant, or so they actually thought, which essentially literally is
fairly significant in a pretty major way.
