Hormones and Resistance Exercise
Hormones
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Definition:
Hormones are
chemical messengers that originate from one organ and travel via the blood
stream to a target organ in order to elicit a response.
Role of Hormones
with Resistance Training
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Resistance training brings about adaptive responses
that result in:
Enhanced size of skeletal muscle
Greater strength of skeletal muscle
Increased power of skeletal muscle
Mechanism
of Responses
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Hormones secreted during and after
exercise
These hormones will bind to receptors
on active tissues to elicit a response
If tissue has reached its capacity
for growth, the hormone response will be less
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Recovery mechanisms are related to
size of cells (i.e. the larger, the longer the recovery)
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Mistakes in exercise Rx
can result in a greater catabolic effect rather than anabolic effect
Renders hormone effect as minimal in
cases
Physiological Presence of Hormones
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What accounts for the amount and
effect of hormones in the blood
Fluid volume shifts
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During exercise, fluid shifts into
tissues causing [ ↑ ]
Tissue clearance rates
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How fast hormones move through tissue, hence keeping
them out of blood
Hormone degradation
Venous pooling
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Can increase time of hormones in blood if peripheral
skeletal muscles are contracting at >
45% of effort
Physiological Presence of Hormones
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What accounts for the amount and effect of hormones in
the blood
Interactions with binding proteins
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May aid in transport of proteins
Receptor interactions
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Ability to bind to receptor influenced by:
# of receptors available for binding
Magnitude of connectiveness and ability to promote
further signaling
The
Primary Hormones
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Testosterone
Effects
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Promotes growth hormone release from anterior
pituitary
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Interacts with receptors on neurons to:
↑ # of neurotransmitters
Cause structural changes
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Interacts directly with muscle to promote protein
synthesis
The
Primary Hormones
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Testosterone
Origin
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In men testes
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In women ovaries and adrenal
Target
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Cell nucleus of muscle where stimulation of DNA
results in protein synthesis
The
Primary Hormones
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Testosterone
Response to Exercise
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↑ in men and women following high-intensity
exercise and resistance training
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Dont typically see ↑ in testosterone
causing change in hypertrophy with aerobic training
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In boys and men < 18 years of age, an ↑ in testosterone can occur with:
a. Large muscle group
exercise (e.g. deadlift, power clean, squats, etc.)
b. Heavy resistance
of 85-95% of 1 RM
The
Primary Hormones
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Testosterone
Response to Acute Exercise
c. Moderate to high
volume exercise with multiple sets, multiple exercises or both
d. Short rest intervals
(30 sec to 1 min)
e. 2 or more years of
resistance training experience
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In men, testosterone resting values
tend to be highest in the morning and drop throughout day
Afternoon and late day resistance
exercise prompts greater testosterone response and greater induced changes
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In women, testosterone resting values
do not change very much throughout day
Women have 15 to 20-fold less
testosterone than men
Effect of Resistance Training on Testosterone
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Long-term resistance training, along with experience
tend to enhance resting and exercise-induced levels of testosterone
Summary
on Testosterone
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In order to elicit an increase in testosterone during
acute exercise:
Use multiple sets
Use 5-10 RM workloads
Use adequate muscle mass during exercise
The
Primary Hormones
2. Growth Hormone (also called somatotropin)
Effects
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Enhances cellular amino acid uptake and protein
synthesis in skeletal muscle
Results in hypertrophy of both slow-twitch (Type I)
and fast-twitch (Type II) fiber types
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Decreases glucose utilization
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Decreases glycogen synthesis
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Increases amino acid transport across cell membranes
The
Primary Hormones
2. Growth Hormone
Effects
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Increases protein synthesis
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Increases utilization of fatty acids
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Increases lipolysis
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Increases availability of glucose and amino acids
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Increases collagen synthesis
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Stimulates cartilage growth
The
Primary Hormones
2. Growth Hormone
Effects
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Increases retention of nitrogen, sodium, potassium,
and phosphorus
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Increases renal plasma flow and filtration
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Promotes compensatory renal hypertrophy
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Enhances immune cell function
Growth Hormone vs Resistance Training
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Role of GH in muscle hypertrophy
GH injections can stimulate muscle growth
Resistance training can stimulate muscle growth
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GH injections are not as effective as resistance
training in improving force production
Growth
Hormone
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Responses to Stressors:
↑ in response to breathholding and
hyperventilation
↑ in response to hypoxia (lack of oxygen)
↑ in response to acidic conditions in blood (i.e.
higher [H+] and lactic acid)
Sensitive to volume (sets,
reps) of exercise
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Less rest between sets, the higher the GH response
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Greater volume workloads, the higher the GH response
Growth
Hormone
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Response in Women
Women generally have higher GH levels in blood than
men
GH highest during early follicular phase
Sensitive to volume of resistance training
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Short rest periods (~1 min) and moderate (10RM) loads
result in higher GH levels vs long rest periods and heavy loads (5RM)
Higher GH levels in women compared to men following
aerobic exercise; not clear why?
Growth
Hormone
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Training adaptations:
GH levels do not appear to change significantly over
the course of a resistance training time period (i.e. 9 months)
GH response to acute exercise session of weight
lifting does not appear to change as much with training
Insulin-Like Growth Factors (IGFs)
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Some effects of growth hormone are
mediated through IGFs
IGFs, also called somatomedins, are
small molecules secreted from liver
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Travel via attachment to binding
proteins in the blood
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If receptor site on tissue (e.g.
muscle) is not available, IGF can ride on binding protein until opening occurs
(e.g. driving around parking lot until closer parking space opens)
Participate in tissue remodeling,
i.e. muscle, nerve, bone growth
Insulin-Like Growth Factors (IGFs)
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Response to Exercise
An increase in IGFs may be the result of tissue
disruption, i.e. muscle and fat (since some IGFs are produced here)
Generally,
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If [IGF] is low, IGF levels will increase with
resistance exercise
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If [IGF] is high, IGF levels will not change
Insulin-Like Growth Factors (IGFs)
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Response to Training
No significant change apparent with long-term
resistance training
Adrenal
Hormones
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Secreted by adrenal gland which has 2 divisions:
Cortex
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Stimulated by adrenocorticotropic hormone (ACTH) from
the anterior pituitary
Medulla
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Stimulated by the nervous system and thus gives faster
response
Adrenal
Hormones
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Cortisol
Secreted from cortex
Viewed as a catabolic hormone in skeletal muscle
(primarily on Type II fibers)
Primary signaler of CHO metabolism as related to
glycogen stores in muscle
Adrenal
Hormones
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Cortisol (continued)
Specific functions
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Converts amino acids to CHOs
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↑ level of
enzymes that break down proteins
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Inhibit protein synthesis
Significant participation after injury → atrophy
Catabolic effects are balanced by anabolic effects of
testosterone and insulin
Adrenal
Hormones
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Response of Cortisol to Resistance Exercise
↑ , particularly with short rest periods (~1 min) and when total volume is
high; just like GH
Important to have cortisol for hypertrophy response in muscle
Adrenal
Hormones
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Other aspects about cortisol and exercise:
Possible marker of tissue
breakdown; may be helpful in determining if overtraining is occurring
Suppresses cells of immune
system which may slow recovery from injury and skeletal muscle remodeling
Adrenal
Hormones
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Catecholamines
Secreted from medulla
Include epinephrine, norepinehprine, and dopamine
Adrenal
Hormones
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Catecholamines (cont.)
Functions:
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↑ force production via central
mechanism and ↑ metabolic enzyme activity
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↑ muscle contraction rate
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↑ blood pressure
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↑ energy availability
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↑ blood flow
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↑ secretion rate of other
hormones, i.e. testosterone
Adrenal
Hormones
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Catecholamine response to Exercise:
↑ epinephrine and norepinephrine with increase in exercise intensity
After resistance training,
elevated levels of catecholamines are maintained for up to 5 minutes into
recovery
Adrenal
Hormones
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Catecholamine response to Training:
Higher levels of epinephrine secreted in response to
acute exercise
Resting levels of catecholamines are lower
Other hormones related to Resistance Training
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Insulin
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Thyroid hormone
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Beta-endorphins