Chapter 4 Flashcards
Describe the overall role of the endocrine system in strength and conditioning.
In general, how does knowledge of the endocrine system inform training
programs?
The endocrine system is a component of a complex signaling system in the human body that
affects changes and supports exercise demands and recovery.
• The endocrine system uses chemical messengers known as hormones to signal
responses from tissues in the body
• Hormonal responses to exercise include anabolic, permissive, and catabolic
hormone signals.
• The programming variables in a strength and conditioning program will determine
the overall hormonal response to exercise and can be manipulated to achieve the
desired hormonal response and subsequent physical adaptations (i.e. hypertrophy)
Endocrine System
• Responsible for signaling in the body to cause changes and adaptations
• Uses hormones to signal to body tissues
• Hormonal responses to exercise contribute to the overall result of a training
program
• Manipulation of acute training variables (sets, reps, %1RM), determine hormonal
response to exercise
• Hormone responses include:
• Anabolic - tissue building
• Permissive - allowing processes to occur
• Catabolic - breaking down tissues/substances
What is general adaptation syndrome?
• Adrenal response to stimulus/stressor
• Begins with the alarm reaction
• When stress is due to training - results in training adaptations that increase
resistance to stressors
Describe the overall process of synthesis, storage, and secretion of hormones.
Which organs are responsible for hormone secretion?
Hormones are synthesized, stored, and released by endocrine glands, which are specialized
structures dedicated for this function.
Neurons and the neurotransmitters they emit may also play a role in hormone function - the
study of this process is known as neuroendocrinology.
Hormones are released into the blood and are delivered to specific receptors on the surface or
in the cytosol of the target tissue cells.
Different hormones can interact with one or many different systems in the body.
• Peptide hormones - receptors are located on cell surface
• Thyroid and steroid hormones - receptors located in the cytosol of the cell
Binding proteins prevent hormone degradation during transit and may also play a hormonal
role in of themselves.
Endocrine Glands
• Anterior pituitary gland
• Posterior pituitary gland
• Thyroid gland
• Parathyroid glands
• Pancreas
• Adrenal cortex
• Liver
• Adrenal medulla
• Ovaries
• Testes
• Heart
• Kidney
Describe how muscle acts as a target for hormone interactions. Describe the
process of muscle remodeling. Which of the primary hormones involved are
catabolic, permissive, or anabolic?
Hormones are a crucial part of the signaling process that results in metabolic and cellular
changes in the muscle in response to resistance exercise and training.
Muscle Remodeling
1. Disruption and damage of muscle fibers
2. Inflammatory response
• Involves immune cells such at T and B cells, influenced by endocrine system
3. Degradation of damaged proteins
4. Hormonal, growth factor, and cytokine interactions
5. Synthesis of new proteins and incorporation into existing or new sarcomeres
• Contractile proteins - actin, myosin
• Structural proteins - titin, desmin
Anabolic Hormones
• Promote tissue building
• Insulin, insulin-like growth factors (IGFs), testosterone, growth hormone
• Block negative effect of catabolic hormones that degrade cell proteins
Thyroid Hormones
• Permissive hormones that allow other hormone actions to occur
Catabolic Hormones
• Degrade cell proteins
• I.e. cortisol, progesterone
➢ Cortisol can also inactivate immune cells and block other signaling pathways
The interrelated nature of hormones, muscle fibers, and changes in muscle fiber capabilities
provides the basis for the influence of hormones in hypertrophy.
Hormones remain only one of the possible mechanisms for muscle adaptation to resistance
training.
What role do receptors play in mediating hormonal changes?
Hormone signals only relayed to the cells with the receptor for that specific hormone.
• Ensures that hormone affects only the target tissue
• Hormone typically trying to influence metabolism or DNA transcription in the nuclei
of muscle cells (muscle cells have multiple nuclei)
• Hormones act through a cascade of reactions that communicate to the DNA
• Every cell has receptors that receive messages from certain hormones
• Hormones can partially bind with other receptors but can fully bind with their
specific receptor
Lock and Key Theory
• States that specific hormones react with specific receptors
• Actual hormone reactions more complex
Cross-reactivity
• Some hormones partially interact with other receptors
• Example: allosteric binding where non-binding hormones can block a receptor’s
primary binding site
Allosteric Binding
• Non-hormone substances enhance or reduce response to primary hormone
• Some hormones may need to link together to produce optimal signals through the
receptor
➢ Example: growth hormone
In certain cases, hormone receptors will downregulate and become less responsive or even
non-responsive to the relevant hormone:
• Occurs when adaptation is no longer possible (i.e. maximum protein has been added
to muscle fiber)
• Occurs from ‘overstimulation’ - i.e. insulin resistance
Binding sensitivity can be increased or decreased, and the number of receptors can also be
altered - results in dramatic adaptations comparable to increased hormone release
List and describe the characteristics of the main categories of hormones and
their interactions with receptors. How do hormones respond to heavy
resistance training?
Steroid Hormones
• Hormones from adrenal cortex and gonads - i.e. cortisol, testosterone, estradiol,
• Fat-soluble
• Passively diffuse across the cell membrane
• Bind with the receptor in cell to form a hormone-receptor complex (H-RC)
• H-RC binds with other H-RCs and opens up nucleus to expose DNA
• Transcribes DNA that releases mRNA into sarcoplasm
• mRNA begins the process of producing the protein promoted by the steroid
Polypeptide Hormones
• Composed of amino acid chains
• Example - growth hormone, insulin
• Cannot cross cell membrane - rely on secondary messengers inside the cell
• Signaling cascade from secondary messenger affects metabolic processes, DNA
transcription, and mRNA translation initiation in the ribosome
• Regulated via negative feedback
Amine Hormones
• Synthesized from amino acids tyrosine or tryptophan
• Tyrosine - epinephrine, norepinephrine, dopamine
• Tryptophan - serotonin
• Bind to membrane receptors on cell surface
• Act through secondary messengers within cell
Heavy Resistance Training
• Long-term resistance training results in significant adaptive responses
• Increased anabolic hormone concentration
• Increased receptors
• Caused in part by increased recruitment of large motor units that stimulates
receptors and sensitivity to anabolic factors
• Leads to muscle growth and strength gains
Describe the mechanisms of hormonal interactions with muscle tissue. What
are the possible implications of hormonal changes in peripheral blood?
Mechanisms of Hormonal Interactions
• Increased hormone blood concentration
• Increases probability of interaction with receptors
• Increased/decreased receptor affinity to hormones
• Genetic predisposition determines the ultimate limit in muscle size growth
• Recovery mechanisms needed for anabolic processes to occur
• Exercise prescriptions will also determine the degree of catabolic effect or lack of
anabolic effect.
• Combination of mechanisms results in exercise-induced hypertrophy
Hormonal Changes in Peripheral Blood
• Increased hormone concentration in blood increases probably of receptor
interaction
• Decreased hormone blood concentration may indicate increased hormone uptake
by receptors
• Interpretation of hormone blood concentration very tricky
• Increased hormone concentration not a prerequisite for muscle growth
• Indicates increased activation of endocrine gland
Endocrine System Adaptations
• Changes in synthesis and storage of hormones
• Changes in the transport of hormones via binding proteins
• Change in the time needed for hormone clearance in liver and tissues
• Variation in the rate of hormone degradation
• Blood-to-tissue fluid shift with exercise stress
• Receptor affinity for hormone (uncommon training response)
• Number of receptors in tissue
• Change in content and size of secretory cells in gland
• Change in the magnitude of the signal sent to nucleus via the H-RC
• Change in the degree of interaction with the cell nucleus
Discuss the characteristics of testosterone. What changes occur in testosterone
in response to resistance training? How does testosterone response vary
between men and women?
Testosterone
• Primary androgen that interacts with skeletal muscle tissue
• Produced in testes (male)
• Testosterone binding to receptor key to stimulating anabolic function
• Increase in testosterone alone not an absolute marker for anabolic function
• Resistance exercise may increase the number of receptors
• Promotes growth hormone release
• GH has a synergistic effect with Testosterone
• Interacts with neuron receptors, increasing the amount of neurotransmitter
released and influencing structural protein changes
• Transported via binding protein in blood
• Binds to receptors inside cell and on cell surface
Testosterone Response in Men and Women
• Increases in free testosterone seen in men following intense aerobic endurance
exercise and resistance training
• Aerobic exercise does not increase hypertrophy
➢ Testosterone may be released to avoid excessive muscle tissue breakdown
• Resistance training increases serum concentration.
• Protocol for increasing free testosterone in men:
➢ Train large muscle groups - i.e. via squatting, deadlifts, power cleans
➢ Use heavy resistance - 85% 1RM or more
➢ Use moderate to high volume of exercise via multiple sets or exercises
➢ Shorter rest intervals - 30 seconds to 1 minute
➢ Two years or more of resistance training
• Testosterone levels in women not as elevated, if at all, following resistance training
• Increase in testosterone sensitivity of the androgen receptors in muscle occur in
women following resistance training
• Despite little change in testosterone concentration in blood, increased sensitivity to
testosterone in women may drive adaptations to resistance training
Discuss the characteristics of growth hormone. How does growth hormone
response vary between men and women?
Growth Hormone (GH)
• Important for both child development and adaptations to resistance training
• Produced in the anterior pituitary gland
• Multiple variants of growth hormone exist
• Relationship unclear between different forms
• Full effects of GH not fully understood
• “GH” refers to superfamily of different molecular forms of growth hormone
• Many different target tissues including bone, immune cells, skeletal muscle, fat cells,
and liver tissue
GH Family Responsible for:
• Decreased glucose utilization
• Decreased glycogen synthesis
• Increased amino acid transport across cell membrane
• Increased protein synthesis
• Increased utilization of fatty acids
• Increased lipolysis
• Increased availability of glucose and amino acids
• Increased collagen synthesis
• Stimulates cartilage growth
• Increase retention of nitrogen, sodium, potassium and phosphorus
• Increased renal plasma flow and filtration
• Promotes compensatory renal hypertrophy
• Enhances immune cell function
Overall GH Release Affected by:
• Age, sex, sleep, nutrition, alcohol, and exercise
• Resistance training protocol - shorter rest periods associated with higher serum GH
➢ Not clear how various forms of GH are individually affected by rest period
GH in Women
• Women higher in 22kDa GH than men
• Hormone concentrations vary throughout menstrual cycle
• When workouts compared, GH response similar between men and women
Discuss the characteristics of insulin-like growth factors. What changes occur in
IGF following training?
Insulin-like growth factors (IGFs) are small polypeptides that mediate many effects of growth
hormones.
Insulin-Like Growth Factors
• Polypeptide amino acid chains
• Produced in the liver
• Superfamily with multiple variations with different numbers of amino acids:
• IGF I - 70 aminos
• IGF II - 67 aminos
• Regulated by GH, testosterone, thyroid hormone, and others
• Bind with binding proteins in blood
• At least 6 different binding proteins regulate availability of IGF- I
• Mechanisms of IGF influenced by strength training factors
• Exercise stress
• Acute hormonal responses
• Need for bone, muscle, and nerve tissue remodelling at the cellular level
• Crucial component of protein anabolism
IGF Response to Training
• Acute increases of IGF after training depend on resting IGF levels
• Low levels pre-training are elevated post training
• Normal/high levels pre training are unchanged by training
• Increased total IGF-I and reduced IGF binding protein I seen in women post-exercise
• Full implications not fully understood
Discuss the adrenal hormones. What is the role of cortisol? What adaptations
and responses occur in cortisol following training? What implications does this
have on muscle growth?
Adrenal hormones are released from the adrenal gland when stimulated by
adrenocorticotropic hormone.
The most important adrenal hormones in strength and conditioning are cortisol and the
catecholamines.
Cortisol
• Exerts catabolic effects by stimulating conversion of amino acids to carbohydrates
• Increases level of proteolytic enzymes - the enzymes that break down proteins.
➢ Inhibits protein synthesis
➢ Suppresses glucose-dependent processes
• Produced in the adrenal cortex when stimulated by adrenocorticotropic hormone
• Anabolic effects of testosterone counter the catabolic effects of cortisol
• Relative binding of each hormone determines anabolic vs catabolic state
• Cortisol increases with resistance exercise
• Effect most dramatic when rest periods are short and work volume is high
• Cortisol’s catabolic effect in men may be reduced by adaptations during training
• Cortisol levels rise acutely from the same stimulus that increases GH
• Acute elevated cortisol levels may be part of remodeling process and are associated
with high volume, large muscle groups, and short rest periods during resistance
training
• Chronic elevated cortisol levels have negative effect on tissue growth and are
associated with overtraining
• Cortisol’s role in suppressing immune cells has direct effect on remodeling of muscle
tissue and may be associated with immunosuppression following intense exercise
What are the catecholamines? What role do catecholamines play in strength
and conditioning? What is the overall implication of adrenal hormones in
strength and conditioning?
Catecholamines
• Primarily epinephrine but also include norepinephrine and dopamine
• Secreted by adrenal medulla and act as powerful central motor stimulators and
peripheral vascular dilators
• Enhance enzyme systems and calcium release in muscle
Role of Catecholamines
• Increased force production via central mechanisms and metabolic enzyme activity
• Increased muscle contraction rate
• Increased blood pressure
• Increased energy availability
• Increased blood flow to muscles via vasodilation
• Augment secretion rates of testosterone and other hormones
Training Adaptations of Catecholamines
• Heavy resistance training increases the ability to secrete epinephrine during maximal
exercise
• Stimulation of catecholamines likely one of the first endocrine responses to
resistance exercise
Adrenal Hormones in Strength and Conditioning
• Training must be varied to allow the adrenal gland to engage in recovery and
prevent the secondary catabolic responses to cortisol
What principles should coaches follow to positively manipulate the endocrine
system with resistance training?
General Principles
• The more muscle fibers recruited for exercise, the greater the potential remodeling
process
• Only the fibers activated by resistance training are subject to adaptation including
hormonal adaptations
Increasing Serum Testosterone
• Focus on large muscle groups
• I.e. - Deadlift, squat, power clean
• Use heavy resistance
• 85% + 1RM
• Use a moderate to high volume of exercise with multiple sets and exercises
• Focus on short rest intervals
Increasing Growth Hormone
• Use workouts with higher lactate concentrations
• High intensity
• High total work
• Short rest periods
• Supplement with carbohydrate pre and post workout
Optimizing Adrenal Response
• High volume, large muscle groups, short rest periods
• Vary training protocols and variables over time
• Provide days of complete rest
• Cycle in low-volume workouts to allow adrenal glands to recover and prevent
chronic cortisol secretion
