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Author Topic: Suppersion of adrenaline production in response to elevated heart rate  (Read 6317 times)
Sasha Pachev
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« on: May 05, 2009, 04:49:06 pm »

I've been studying about the role of adrenaline in exercise lately.

My understanding of how it works. You tell your body to run, it says, hey HR is too low, stroke volume is too low, the glycogen needs to be broken down, so it starts releasing adrenaline to fix all of that. That is what I get from various online resources.

Now comes something I believe to be the case from personal experience but do not have any scientific source for - I'd like to find one if there is. As HR increases a regulatory hormone is released to communicate to the adrenal glands to cut the production of adrenaline. Either that, or it just takes a certain amount of adrenaline to keep HR at a certain level, and eventually the adrenal gland capacity is saturated. In either case, HR may be capped because the adrenal glands are not strong enough to push it past a certain level.

After a period of time (anywhere from 10 minutes to 100 minutes), the adrenal glands may become fatigued and their ability to maintain adequate HR is reduced. Thus the pace has to drop.

Reason I have for believing this way:

a) I have noticed that on bad days my HR stagnates in a tempo run and so does the pace. The correlation between the pace and the HR is very direct. Lack of sleep, and stress seem to correlate well with those bad days. I have experienced unexplained drops in HR along with the pace on those days mid-run. HR and pace can easily drop into marathon pace range while trying to run a 2.5 mile tempo.

b) I have finished plenty of races fresh but slowing down throughout the race in spite of attempts to go faster.

c) Frequent experience when trying to hang with someone at the end of a race that is passing me - the breathing does not feel very hard, but I cannot breathe any harder and start feeling like I am holding my breath. After a minute or two I have to back off because I do not want to suffocate. This is different from a more normal experience when you start breathing harder and feel like you are going to throw up if you hold on any longer.

d) Both Ryan Hall and Peter Gillmore have talked about the importance of being able to get excited around mile 16 in the marathon.

e) Adrenaline rush somehow evades me after a few miles at 5:30 pace. I just cannot imagine myself getting spooked in that condition.

If anybody has any insights, I would appreciate it.


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Dallen
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« Reply #1 on: May 05, 2009, 06:36:48 pm »

I don't really claim to know much about this, but it makes sense as Sasha stated it. The glands only store so much hormone. Once you run out you are out of luck. Your body can make more, but that takes a while. I suspect that this is improved by doing long hard runs where you practice running out of adrenaline, then hopefully your body learns to strore more. Kinda like glycogen.
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adam
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« Reply #2 on: May 05, 2009, 10:01:39 pm »

Epinephrine (adrenaline) is a stimulatory hormone that plays a large part in heart rate regulation in relation to exercise. Like you said Sasha, as you increase exercise, your body must respond to the exercise stimulus, and increasing heart rate and ventilatory rate and glycogen breakdown (depending on the intensity) is part of that. It is significant from the Nervous signal down to the muscle contraction itself.

Will some endocrine secretions are in limited supply (glands are very small), they can be (and are) extremely potent. If I remember correctly, I recall hearing that in order to gain a very small sample of pituitary secretions, hundreds of pigs' cadavers had to be opened in order to get a small drip from each of their pituitary glands.

Generally, as you increase your exercise rate, your body will increase its release of epinephrine as a coping mechanism. However, the body also works on a negative feedback system, which after a while of rising epinephrine concentration levels tells the body that it has enough to do the job. The body then relays this message back and says, "too much stimulation, concentration is too high, shut down sympathetic secretion". It will continue to do this until blood concentration levels decrease. To make this easier to understand, think of it as a big meal for lots of people. You to begin with, you have lots of empty plates. Then you begin to fill them up with food for everyone. Things go smoothly. However, after you fill up the available plates, you notice you are still making lots of food. You then have to cut back production until plates are available again. Once those plates are open again, then you can start filling them back up and you can start production again. Or it works the other way around. More and more people show up to come eat, and you cannot produce food fast enough to feed all of them. You then have to limit the number of people coming in until you get caught up. If their were no regulatory mechanisms withe epinephrine, you would not have a happy heart rate. It would beat so fast you would probably die. Or so slow you would die. In exercise, it has to be elevated and suppressed constantly to ensure proper function and balance. yes you want it higher, but your body will only allow you so much before it has to revert back to safety mode.

In some individuals, this negative feedback mechanism is hindered or affected in some way. This leads to hypersecretion. Eventually, either the gland tires out, or the body becomes less and less stimulated by the hormone secretion. Another possible problem is hyposecretion, in which the gland receives little to no signal to produce and secrete more, and then atrophies.

The endocrine system is not as easily "trainable" as other body systems mainly because it is so intricate. This is why so many athletes attempt to mimic the effects of endocrine hormones by taking things like GH, or testosterone. Only with this kind of sustained potency can they use the endocrine system to their advantage in training. Sure, you can try to get yourself pumped by getting angry before a run - like slapping yourself or something, or pretending to be chased by a dog (or actually being chased by a dog), or listening to upbeat, clear tempo'd music (which by the way has been used by music therapists and others to teach efficient motor control and movements, so it's not a false belief that listening to music can actually help you perform or run better) but eventually, your endocrine system will begin to say- "you actually don't need me as much anymore for this, so i'm not going to do anything much to help". Another reason why so many athletes turn to illegal means to try and get a bigger "hit" on their system.
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Sasha Pachev
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« Reply #3 on: May 06, 2009, 01:19:34 pm »

Adam, Dallen, thanks for the info.

One more question. If the adrenal glands completely quit, does your heart stop? Or is there some other way to keep the heart going?
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adam
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« Reply #4 on: May 06, 2009, 01:51:55 pm »

Sasha, you'll want to look up the terms sympathetic nervous system and parasympathetic nervous system, To better understand the role of epi and norepinephrine in the heart or muscle. This is more of what I was referring too.

As for the adrenal gland itself, it if quit, you may die, not necessarily from the heart stopping only, but from any other number of functions that the adrenal gland helps regulate. Check out addison's disease, which is caused by a adrenal dysfunction.

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