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Endocrine Response to Exercise Training

KIN 265 - Berry College - Dept. of Kinesiology
by

David Elmer

on 7 September 2016

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Transcript of Endocrine Response to Exercise Training

Endocrine Response to Exercise Training
acute
chronic
vs.
short term
long term
response
adaptation
resistance training is the only natural stimulus that increases lean tissue mass
ability to do so depends on the training program employed
different workout types result in different hormonal responses
tissue adaptations are regulated by the circulating hormones
what you see on the outside:
what happens on the inside:
hormone
- chemical messenger
endocrine glands
- secrete hormones...
stimulated by:
chemical signal received by receptor
electrical signal from nerves
in the blood...
to target tissue cells
paracrine signalling
message delivered to adjacent cell without traveling in the blood
autocrine signalling
message sent within a cell
hormone never leaves the cell that produced it
endocrine signalling
binding proteins
protect and store hormones, extend hormone life in circulation
but
hormones are not active unless separated from their binding protein
hormones and their actions are incredibly complex
affect multiple tissues
muscle, liver, bone, kidney, etc.
play multiple physiological roles
energy management, reproduction, growth, development, etc.
interact with each other in complex ways
anabolic
catabolic
vs.
build-up
synthesis
break down
degradation
muscle
remodeling
damage or disruption
inflammatory response
hormonal interactions
net protein synthesis
involves immune cells under hormonal control
increased protein synthesis
decreased protein degradation
anabolic hormones
catabolic hormones
testosterone
GH
IGFs
cortisol
catecholamines
role of receptors
heavy resistance and hormonal increases
hormonal changes in peripheral blood
hormones will only affect a tissue that has a receptor for that hormone
target tissue vs. every other tissue
locations:
blood -
binding proteins
cell membrane -
polypeptide receptors
DNA -
steroid receptors
lock-and-key theory
(oversimplification)
may enhance or inhibit hormone action
bind same receptor, but do different things
variables:
hormone concentration
receptor number
receptor sensitivity
hormone concentration depends on amount of hormone and amount of blood (water)
fluid volume shifts:
shift of fluid from inside to outside cells can carry hormones also
increased hormones without increase in gland secretion
tissue clearance rates:
how long it takes a hormone to circulate through a tissue
it might not go to the intended place first, so it may have to travel through other organs on the way
slows it down, might degrade or inactivate it
hormonal degradation:
breakdown/deactivation of the hormone
venous pooling of the blood:
slows down the return circulation of blood
may result in slower transport of hormones
binding protein interaction:
may make it easier to transport protein
protein needs to be freed before it can be active
during exercise, electrical, chemical, and hormonal signals are sent from the brain and muscles to other endocrine glands
acute response to the exercise stress
chronic adaptation to the stress
resistance training:
activates muscle fibers that aren't active in every day activities
alters muscle membranes - alters hormone receptor sensitivity
amount of force produced affects increase in receptor sensitivity to anabolic hormones and receptor synthesis
only takes 1 or 2 sessions to increase number of receptors
stress from resistance training:
actin and myosin
protein degradation
too much stress:
protein degradation
receptor sensitivity
receptor number
only in muscle fibers used during exercise
what exercises are you doing?
epinephrine/norepinephrine
&
"fight or flight" response
aka adrenaline
increased force production
increased neural and enzymatic activity
increased muscle contraction rate
increased blood pressure
increased energy availability
increased blood flow
alter secretion of other hormones
heavy resistance training increases your ability to secrete epinephrine during maximal activity
can promote GH release, increasing protein synthesis
can enhance neural transmission
transported by a transport protein from...
testes - men
ovaries - women
increase DNA transcription, increasing protein synthesis
variables that testosterone
large muscle group exercises
heavy resistance
mod-high volume (reps x sets)
short rest intervals
amount of resistance training experience
effect of age in males:
pre-puberty:
little testosterone to begin with
smaller increase with exercise - may be due to non-responsiveness of testes
young men:
greater total testosterone at rest and after workout
more bound testosterone (better transport) and more free testosterone (more action)
old men:
less testosterone at rest and in response to exercise
increases after exercise
effect of sex:
males:
more testosterone
greater response to exercise
females:
15-20 fold less testosterone
small increase after exercise (if any)
males
females
growth hormone
important in childhood development
vital in the adaptation to resistance training
maintains blood glucose
increases breakdown & use of fats
increases protein synthesis
increases collagen synthesis
stimulates cartilage growth
increases kidney function & size
enhances immune function
enhances recovery from stress (resistance exercise)
big increases in release during sleep
so, should I take GH to get big and strong?
probably not...
unintended side effects, especially if everything is normal starting out
muscles might grow, but they don't work as well
GH response to stress
increased release when H ions and lactate concentrations are elevated
+
it seems that an "intensity threshold" must be reached in order to increase GH
variables affecting GH release:
volume of exercise (reps x sets)
amount of rest between sets
resistance
- more is better
- less is better
- more is better (if other variables are constant)
training adaptations of GH
little (if any) change in the resting concentration of GH with training
many other factors may be altered
receptor sensitivity
diurnal variation
feedback mechanisms
etc.
smaller increase in GH release in response to a particular stress
insulin-like growth factors
increased in response to GH, testosterone, and thyroid hormone
travel in the blood bound to a binding protein - may store IGFs for an extended period of time
manufactured and stored in liver, muscle, and fat cells
IGF response to exercise
results in prolific increases in protein anabolism
IGF release probably due to disruption of cells
autocrine and paracrine mechanisms are important for IGF influence on muscle
initial levels of IGFs may determine whether or not they increase in response to exercise
lower initially - increased with exercise
higher initially - no increase with exercise
potentially elevated 8-30 hours after exercise ends
influenced by nutritional status
training adaptations of IGFs
little to no change in IGF concentrations in response to resistance training
adaptations are probably elsewhere:
receptors
release and transport
interaction with other hormones
autocrine function in the muscles
etc.
primary hormone signal for carbohydrate metabolism
activity is related to glycogen availability
less glycogen = more cortisol activity
converts amino acids to carbohydrates
gets the amino acids by breaking down proteins - proteolytic activity
greater breakdown of fast-twitch fibers (more amino acids available)
greater total control of slow-twitch fiber breakdown
results in atrophy of muscle fibers
resistance training & cortisol
increased cortisol in response to resistance training
especially when volume is high and rest periods are short
responds to big anaerobic metabolism stimulus
conditions that increase GH the most also increase cortisol the most
muscle remodeling process
increases in response to inflammation
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