Endocrine Responses to Resistance Exercise

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Endocrine Responses to Resistance Exercise
chapter 3
Endocrine Responses to Resistance Exercise
William J. Kraemer, PhD, CSCS, FACSM, FISSN,
FNSCAJakob L. Vingren, PhD, CSCSBarry A.
Spiering, PhD, CSCS
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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.

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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.

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Section Outline

• Synthesis, Storage, and Secretion of Hormones

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Key Term

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

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Glands of the Body

• Figure 3.1 (next slide)
• The principal endocrine glands of the body along
  with other glands that secrete hormones

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Figure 3.1
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Section Outline

• Muscle as the Target for Hormone Interactions

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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).

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Figure 3.2
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Section Outline

• Role of Receptors in Mediating Hormonal Changes

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Lock-and-Key Theoryfor 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

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Figure 3.3
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Androgen Receptor Diagram

• Figure 3.4 (next slide)
• Diagram of a typical androgen receptor on the DNA
  element in the nucleus

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Figure 3.4
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Section Outline

• Steroid Hormones Versus Polypeptide Hormones
• Steroid Hormone Interactions
• Polypeptide Hormone Interactions

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Steroid Hormones VersusPolypeptide Hormones

• There are two main categories of hormones
• Steroid
• Polypeptide (or simply peptide)

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Hormone Structure

• Figure 3.5 (next two slides)
• Structure of
• (a) a polypeptide hormone (growth hormone, 22
  kDa)
• (b) a steroid hormone (testosterone)

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Figure 3.5a
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Figure 3.5b
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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
  cells nucleus and opens it in order to expose
  tran-scriptional units that code for the
  synthesis of specific proteins.
• (continued)

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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.

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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,
  butthe two are shown together in this diagram.

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Figure 3.6
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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

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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

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Figure 3.7
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Section Outline

• Heavy Resistance Exercise and Hormonal Increases

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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.

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Section Outline

• Mechanisms of Hormonal Interactions

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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.

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Section Outline

• Hormonal Changes in Peripheral Blood

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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.

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Key Point

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

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Section Outline

• Adaptations in the Endocrine System

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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

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Section Outline

• Primary Anabolic Hormones
• Testosterone
• Free Testosterone and Sex HormoneBinding
  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)

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Section Outline (continued)

• Primary Anabolic Hormones
• Insulin-Like Growth Factors
• Exercise Responses of Insulin-Like Growth Factors
  
• Training Adaptations of Insulin-Like Growth
  Factors

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Primary Anabolic Hormones

• There are three primary hormones involved in
  muscle tissue growth and remodeling
• Testosterone
• Growth hormone (GH)
• Insulin-like growth factors (IGFs)

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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.

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Biosynthesis of TestosteroneFrom Cholesterol

• Figure 3.8 (next slide)
• The series of chemical reactions in the
  biosynthesis of testosterone from cholesterol

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Figure 3.8
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Key Point

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

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Primary Anabolic Hormones

• Testosterone
• Free Testosterone and Sex HormoneBinding
  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

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Serum TestosteroneResponses 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

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Figure 3.9
Reprinted, by permission, from Kraemer et al.,
1990.
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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

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Growth Hormone Cybernetics and Interactions

• Figure 3.10 (next slide)
• Diagram of growth hormone cybernetics and
  interactions

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Figure 3.10
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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.

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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.

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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.

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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.

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Insulin-Like GrowthFactor 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-carbohydrat
  e (i.e., Mass Fuel) before and during the 1-hour
  recovery period
• p lt .05 from corresponding placebo value

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Figure 3.11
Adapted, by permission, from Kraemer et al., 1998.
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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.

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Section Outline

• The Adrenal Hormones
• Cortisol
• Role of Cortisol
• Resistance Exercise Responses of Cortisol
• Catecholamines
• Role of Catecholamines
• Training Adaptations of Catecholamines

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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.

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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.

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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

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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.

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Section Outline

• Other Hormonal Considerations

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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.