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What Happens in CNS Fatigue?


I'm still searching/googling but I'm looking for a basic explaination of what happens to the nervous system that it needs to recover from. Is it just neurotransmitter depletion or is there damage to repair?


This is a real good question that, to the best of my knowledge, is still a mystery.

I'll admit that it's ironic that, even though we lack objective criteria to measure CNS fatigue, Biotest still sells a product to help counter-act it (Power Drive).

Still, we know it exists because it happens. As for how and why... good luck.


i see the nervous system as a self charging battery

more output, less rest, will equal a shortage.

shortage of energy = below par performance

thats my 2 cents, if that makes ANY sense to you


great explanation.


Your nerves have an in and out system.
On the inside is potassium (K+) and the outside is sodium (Na+).
For a charge to be generated, the potassium and sodium momentarily switch places. This causes a charge to be generated.
Then, there are synapses. Synapses are like junctions or pits where no charge can get across. Unless a special "spray" (neuro transmitter) is discharged which acts as a bridge that allows a charge to go through.
However, this bridge only lasts for a short while. So each time a charge goes through, a new bridge needs to be built.

Theses neuro transmitters are released by a complex set of actions.
These neuro transmitters are released when a special compound attaches to a binding site (which acts as a button, which in turn releases the neuro transmitters).
Each type of nerve behaves differently (you have nerves for pain, for cold, for hot, for pressure, for muscle contractions, etc) and each one has a specific binding site.
When you take painkillers, you can still move and feel pressure but you do not feel pain.
It is for that reason. Painkillers inhibit (block out the button) the binding site. The pain receptors can't get a charge to go through. Your brain cannot know what is going on because it's not receiving any signals. Therefore, you feel no pain.

Concerning neuro transmitters. They include: Seratonin, dopamine, and acetylcholine. Some others as well, probably.
Without these, charges cannot pass through your body. Remember that neuro transmitters act as bridges.

There is something called an action potential. Nerves will fire only if a certain stimulus is present...or greater. Meaning that for your nerves to discharge, there must be a certain treshold. If the temperature in the air goes from 70F to 70.003 F, your body will not detect it. The stimulus is not important/strong enough to elicit a reaction. That is the treshold.
For certain motor units (or all of them) to be recruited, a certain effort must be exerted.

For training, the heavier stuff you lift (singles), then the more nerves you recruit.
The more nerves you recruit, the more sodium and potassium exchange places, the more neuro transmitters are discharged and used up, the more atp is used and this and that.
This is why CNS fatigue is more easily acquired when you lift very heavy (singles, triples) as opposed to light (20 reps and above).
Your body acquires certain fats, carbs, proteins (amino acids), minerals and vitamins and then constructs these neurotransmitters. This takes time and resources. When you don't rest, or eat enough, then your body is not able to refill and over time it leads to over training.
So to say that the CNS is like a battery is not quite correct. It's more like a can of hair spray that is very slowly refilled and only at certain times (only when you sleep).

The main elements to look into for CNS fatigue is Seratonin, dopamine, and acetylcholine.
If you can find pills that contain these chemicals/compounds, that would obviously help. You want to increase these chemicals/compounds. However, good sleep (brain releases seratonin during sleep) and healthy diet are key. That's the best way to do it.

It would seem that serotonin actually causes an increase in CNS fatigue.


yea but with nervous system... is it possible to expand you battery life so to speak by doing something.. or are you stuck with the same "battery life" your whole life.


Your nervous system adapts over periods of months is my understanding, which is why advanced athletes can handle greater training loads. The best thing you can do to improve your "battery" is to sleep and eat plenty and very gradually increase training volume and/or frequency.


A lot of what was said here is absolutely false, starting with the fact the serotonin isn't spelled correctly. Saying that neurotransmitters are depleted would imply that said person has a clinically recognizable disease. A generalization such as the one above is impossible. For example, if someone was to have low serotonin and/or dopamine then that would imply that he/she has depression. If only dopamine is depleted in certain areas of the brain then that leads to Parkinson's disease, a general increase, however, leads to psychosis.

Acetylcholine definitely has a role in direct control of muscle because it is what is released in the peripheral nervous system to active muscle fibers. Even so, lowering concentrations even slightly would lead to noticeable decreases in strength, starting with really saggy eyelids... so until that happens I'm pretty sure a persons lifts wouldn't be affected!

All that being said though, its still hard to say what or how CNS fatigue is caused. But you could probably compare is to a long day at work: you just don't feel 'good' at the end of it... more simply said it's know as exhaustion. There are certain things people know yet dont know how to explain. Everyone knows you need sleep, rest and a good healthy source of food, but try explaining why you really need sleep to lift better, its not that easy, it comes down to fact that you just feel tired and weak if you dont. Its only important to know that the body needs it.


Doesn't over training (burn out) lead to several changes in mood up to and including depression?
It's not false.

And yeah, my bad on the spelling.
And i also had it backwards.
You want low serotonin levels.


"Hypotheses have been developed for several neurotransmitters including serotonin (5-HT; 5-hydroxytryptamine), dopamine, and acetylcholine."


That's the beauty of the human body. I can't cite any resources to claim my statement, but I believe with the right training, you can steadily increase the amount of ELECTRICITY output through out your entire body. (With SPECIFIC training)Your CNS will be able to harness a stronger charge, thus rendering more explosiveness, responsiveness, and power.

It's the difference between the average meathead punch, and a straight right from
Nate Marquardt.


Legendaryblaze, You are right about point out that extensive exercise can affect behavior, but to extent of which 99% percent of people train it would definitively not be noticeable. The fact still remains that a lot of claims are still working hypotheses, so it should be taken lightly. What Rival6 just stated above probably describes it the best.

You have to adapt and condition your body for maximum effort... and yet not overdo it to the point of fatigue. But again, thats something everyone should know... hell, if you start jogging everyday you should soon notice that you will be able to jog a little longer and a little faster after some time... to put it into simple terms. The role of each neurotransmitter is very debatable, as I mentioned, it really has to do depend on certain pathways.

You can point any one of them and say it has some role, but we just don't know. So far over 100 neurotransmitter have been identified so its going to be a while before and concrete theories can laid down regarding CNS fatigue.

On an associated note, even nitric oxide has neurotransmitter properties, yet supplements doesn't significantly alter mood or behavior. Not everything ingested has the ability to be absorbed, let alone enter the brain, but I don't think I will go into that right now. If someone is interested, though, check out the blood brain barrier on google.


Was trying to make sense of the thing.

However, would the jogging thing have to do with CNS or muscle?
I THINK the more you enter into endurance, the less important CNS becomes (low threshold, repetitive movement) as opposed to maximal strength.
I assume that's why it's easier to burn out (in terms of CNS) lifting heavy weights with high volume a opposed to running with high volume.


What about bypassing blood brain barrier with site injections...whaaaaat?


I also think that it would be easier to burn out lifting heavy weights than jogging. I was just using it as a generalization of endurance, not specifaically jogging itself.

Nyral, you might have misread. I said ingested, not injected. As for injection, they only bypass first pass metabolism in the liver. Only small lipophilic molecules have a free pass in and out of the brain e.g.: oxygen, carbon dioxide, and some of the more fun stuff, such as alcohol.