vs.
response
adaptation
Endocrine Response to Exercise Training
vs.
degradation
synthesis
endocrine signaling
hormone
endocrine glands
what you see on the outside:
what happens on the inside:
- chemical signal received by receptor
- electrical signal from nerves
binding proteins
- tissue adaptations are regulated by the circulating hormones
- resistance training is the only natural stimulus that increases lean tissue mass
- protect and store hormones, extend hormone life in circulation
but
- hormones are not active unless separated from their binding protein
- different workout types result in different hormonal responses
- ability to do so depends on the training program employed
paracrine signalling
autocrine signalling
- hormone delivers message to the cell that produced it
- message delivered to adjacent cell without traveling in the blood
hormones and their actions are incredibly complex
- muscle, liver, bone, kidney, etc.
- play multiple physiological roles
- energy management, reproduction, growth, development, etc.
- interact with each other in complex ways
role of receptors
hormonal changes in peripheral blood
heavy resistance and hormonal increases
locations:
- during exercise, electrical, chemical, and hormonal signals are sent from the brain and muscles to other endocrine glands
blood - binding proteins
cell membrane - polypeptide receptors
DNA - steroid receptors
- hormone concentration depends on amount of hormone and amount of blood (water)
fluid volume shifts:
- hormones will only affect a tissue that has a receptor for that hormone
chronic adaptation to the stress
acute response to the exercise stress
- shift of fluid from inside to outside cells can carry hormones also
- target tissue vs. every other tissue
- increased hormones without increase in gland secretion
variables:
resistance training:
tissue clearance rates:
- how long it takes a hormone to circulate through a tissue
- hormone concentration
- receptor number
- receptor sensitivity
- activates muscle fibers that aren't active in every day activities
stress from resistance training:
- 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
- alters muscle membranes - alters hormone receptor sensitivity
lock-and-key theory
hormonal degradation:
only in muscle fibers used during exercise
- breakdown/deactivation of the hormone
- what exercises are you doing?
venous pooling of the blood:
the amount of force produced affects receptor synthesis and receptor sensitivity to anabolic hormones
- slows down the return circulation of blood
bind same receptor, but do different things
- may result in slower transport of hormones
- only takes 1 or 2 sessions to increase number of receptors
binding protein interaction:
may enhance or inhibit hormone action
- may make it easier to transport protein
- protein needs to be freed before it can be active
hormonal interactions
net protein synthesis
inflammatory response
damage or disruption
catecholamines
- involves immune cells under hormonal control
epinephrine/norepinephrine
aka adrenaline
increased protein synthesis
decreased protein degradation
"fight or flight" response
- increased force production
anabolic hormones
catabolic hormones
- increased neural and enzymatic activity
- increased muscle contraction rate
- increased energy availability
- alter secretion of other hormones
heavy resistance training increases your ability to secrete epinephrine during maximal activity
cortisol
- primary hormone signal for carbohydrate metabolism
testosterone
GH
IGFs
- transported by a transport protein from...
insulin-like growth factors
- activity is related to glycogen availability
- important in childhood development
- testes - men
- ovaries - women
- results in prolific increases in protein anabolism
- less glycogen = more cortisol activity
- vital in the adaptation to resistance training
- increased in response to GH, testosterone, and thyroid hormone
- increase DNA transcription, increasing protein synthesis
- converts amino acids to carbohydrates
variables that testosterone
- travel in the blood bound to a binding protein - may store IGFs for an extended period of time
- gets the amino acids by breaking down proteins - proteolytic activity
- maintains blood glucose
- increases breakdown & use of fats
- increases protein synthesis
- increases collagen synthesis
- stimulates cartilage growth
- increases kidney function & size
- enhances immune function
- large muscle group exercises
- heavy resistance
- mod-high volume (reps x sets)
- short rest intervals
- amount of resistance training experience
- can promote GH release, increasing protein synthesis
- manufactured and stored in liver, muscle, and fat cells
- can enhance neural transmission
- greater breakdown of fast-twitch fibers (more amino acids available)
- greater total control of slow-twitch fiber breakdown
- influenced by nutritional status
effect of age in males:
enhances recovery from stress (resistance exercise)
- results in atrophy of muscle fibers
pre-puberty:
old men:
young men:
- big increases in release during sleep
- less testosterone at rest and in response to exercise
training adaptations of IGFs
IGF response to exercise
- little testosterone to begin with
- smaller increase with exercise - may be due to non-responsiveness of testes
so, should I take GH to get big and strong?
- greater total testosterone at rest and after workout
- more bound testosterone (better transport) and more free testosterone (more action)
resistance training & cortisol
- potentially elevated 8-30 hours after exercise ends
- little to no change in IGF concentrations in response to resistance training
- IGF release probably due to disruption of cells
- increased cortisol in response to resistance training
- especially when volume is high and rest periods are short
- autocrine and paracrine mechanisms are important for IGF influence on muscle
- unintended side effects, especially if everything is normal starting out
- muscles might grow, but they don't work as well
- adaptations are probably elsewhere:
- receptors
- release and transport
- interaction with other hormones
- autocrine function in the muscles
- etc.
- responds to big anaerobic metabolism stimulus
effect of sex:
- initial levels of IGFs may determine whether or not they increase in response to exercise
- conditions that increase GH the most also increase cortisol the most
lower initially - increased with exercise
higher initially - no increase with exercise
males:
females:
muscle remodeling process
training adaptations of GH
GH response to stress
- more testosterone
- greater response to exercise
- 15-20 fold less testosterone
- small increase after exercise (if any)
- increased release when H ions and lactate concentrations are elevated
- little (if any) change in the resting concentration of GH with training
- many other factors may be altered
- it seems that an "intensity threshold" must be reached in order to increase GH
- increases in response to inflammation
variables affecting GH release:
- receptor sensitivity
- diurnal variation
- feedback mechanisms
- etc.
- more is better
- volume of exercise (reps x sets)
- amount of rest between sets
- resistance
- less is better
- more is better (if other variables are constant)
- smaller increase in GH release in response to a particular stress