Endocrine Response to Exercise

influences the endocrine response

exercise duration and intensity (time and % VO2 max)

Proteins are broken down into

amino acids

muscle can directly metabolize

branch chain amino acids and alanine from proteins

liver can convert alanine to

glucose

proteins to total energy production during exercise

only a small contribution (~2%)

protein consumption may increase

to 5-10% late in prolonged-duration exercise

enzymes that degrade proteins

proteases

proteases are activated in

long-term exercise

substrate use during exercise 2-4 hrs

plasma FFA use increases, blood glucose use increases, muscle triglycerides are depleted, muscle glycogen is depleted

as %VO2 max increases, substrate used...

carbs are heavily relied upon after like 60%, fats are more relied upon at 10-20%

As exercise goes on...

substrate use changes from a reliance on carbs to fats

glycogenolysis

breakdown of glycogen to glucose

glycogenolysis is related to

exercise intensity

high intensity exercise effect on glycogen

greater and more rapid glycogen depletion

plasma epinephrine is a powerful

simulator of glycogenolysis

high intensity exercise effect on plasma epinephrine

greater increases in plasma epinephrine

When epinephrine is equal to norepinephrine...

heart rate increases, glycogenolysis increases, lipolysis increases

when epinephrine is much greater than norepinephrine...

bronchodilation, vasodilation

when norepinephrine is greater than epinephrine...

increase in lipolysis, increase in phosphodiesterase, vasoconstriction

when epinephrine is greater or equal to norepinephrine...

opposes action of B1 receptor and B2 receptors, insulin secretion decreases.

where does Epi and Norepi come from

adrenal glands, also called catecholamines sometiems

strong relationship between epi and the breakdown of

glycogen to glucose during exercise as a function of intensity and duration

epi is not the only way our body communicates a need for

glucose during exercise

the epinephrine response is considered...

extracellular (i.e. due to the nature that it is being released outside the muscle fiber from adrenal glands)

another term to describe the process of controlling the breakdown of glycogen (glycogenolysis) in our body is the term...

"redundant"

when the text uses "redundant" it means,

our body has more than one way to essentially influence/control glycogenolysis

we categorize this redundancy as

extracellular or intracellular

during 100% vo2 max, epinephrine...

skyrockets

epinephrine during 82-89% vo2 max

rises to about 5 nmol

epinephrine during lower intensities.

lower, about 2 nmol

propanolol

a beta receptor blocker which prevents the release of epinephrine during exercise.

when propanolol was used on participants, what happens to the response during exercise

response to glycogen was similar with and without it

calmodulin

calcium binding messanger PRO that activates processes leading to the glycogenolysis. located in the muscle cell

how is calmodulin activated?

as a result of muscle contraction

glycogen breakdown to glucose in the muscle is under dual control of

epinephrine-cyclic AMP and Ca++ -Calmodulin

the calmodulin role during exercise

is enhanced due to the increase in Ca++ from the sarcoplasmic reticulum.

the breakdown of glycogen (glycogenolysis) and the delivery of fuel (glucose)...

parallels the activation of contraction

during exercise, the bodys options are to

mobilize glucose from glycogen stores in the body OR use other substrates (glyconeogenesis) to spare or save glucose for later

the body does not want to

disturb blood glucose

we think of the endocrine response as acting in two different manners

permissive or slow-acting OR fast acting

permissive or slow acting hormones

thyroxine, cortisol, and growth hormone

fast acting hormones

epinephrine, norepinephrine, insulin, glucagon

IMPORTANT TO KNOW. Plasma glucose is maintained through 4 processes which can be permissive or fast-acting:

1. Mobilization of glucose from liver glycogen stores

2. mobilization of plasma FFA from adipose tissue (spares blood glucose and is actually a training adaptation)

3. Gluconeogenesis from amino acids, lactic acid, and glycerol

4. Blocking the entry of glucose into cells (forcing use of FFA as a fuel)

The central nervous system

comes first, it needs to balance energy needed to sustain life first, it runs solely off glucose, it will stop exercise to maintain glucose homeostasis if necessary

thyroid hormones

Triiodothyronine (T3)

Thyroxine (T4)

Calcitonin

thyroid hormones are

permissive in manner which allows other hormones to exert their full effect

T3 (triiodothyronine) enhances the effect of

epinephrine (permissiveness) to mobilize FFA from adipose tissue

thyroid hormones during exercise

no real substantial change, there is an increase in free T3 because blood flow is higher

thyroid hormones establish

overall metabolic rate

thyroid hormones' permissive manner influences

the # of receptors on surface of cell AND the affinity of the receptor

affinity of a receptor is the receptor's

greater ability to bind

WITHOUT T3, epinephrine has

little effect on mobilization of FFA from adipose tissue (this is because of the receptor affinity and quantity)

affinity example

hemoglobin has a higher affinity in the lungs than the tissues, it accepts a lot of oxygen in the lungs and drops it off in the tissues

Cortisol

primary glucocorticoid from adrenal cortex, slow acting hormone

effects of cortisol

stimulate FFA mobilization from adipose tissue, enhance gluconeogenesis in the liver, decrease the rate of glucose utilization by cells

changes in cortisol may be related to

repair of exercise-induced tissue damage (i.e. stress response)

cortisol during exercise

decrease during low-intensity exercise, increase during high intensity (above 60% VO2 max)

cortisol's overall action in exercise is

preserving plasma glucose

When cortisol rises during exercise, its effect in recovery would be to

free more fatty acids and make more triglycerides for fuel in the future (store it)

cortisol's influence on triglycerides

triglycerides are located in belly fat mostly and when cortisol increases, cortisol increases during exercise to help store energy for long periods of time

growth hormone

slow acting, supports the action of cortisol

IGF

insulin growth factors

during high intensity exercise, plasma growth hormone

increases by up to 2000%

as exercise goes on at about 60% VO2 max, plasma (circulating) growth hormone

increases then plateau

main effects of growth hormone

decreases glucose uptake by tissue, increases FFA mobilization, enhances gluconeogenesis in the liver

Exercise effect of growth hormone

increases in plasma GH with increased intensity, greater response in trained runners

Plasma epinephrine and norepinephrine during exercise

considered fast-acting hormones

main effects of epi and norepi during exercise

maintain blood glucose

- muscle glycogen mobilization

- increase liver glucose mobilization

- increase FFA mobilization

- interfere with glucose uptake

plasma E and NE increase during exercise

also related to increased heart rate and blood pressure during exercise

there is a decrease in plasma E and NE

following training

note: a good portion of this increase in concentration during exercise is thought to be related to the influence that E and NE have on

cardiovascular adjustments to exercise (i.e. trained individuals tend to release less)

plasma epinephrine changes longitudinally during __________ and acutely during _____________

training and exercise

after weeks of training, epinephrine release

Decreased. You are training the sympathetic nervous system, which increases your ability to secrete these hormones