aware me on the CNS.

[IDrinkBloodLOL]

I frequently hear talk about how doing this or that is very CNS taxing.

What part of the CNS? What organs? Is it in the spine or brain? What is being taxed in the CNS and how?

Reps for all good explanations.

[-Ironside-]

Central nervous system broham.
Think of working out like taking a test. An easy test you can blow through and do another one right away but when you take a hard test, your mind is ****ed afterwards and producing a coherent thought is a struggle.
Lifting stresses your CNS and even though you might have the physical strength to do more the neurons just aren't going to be firing.
That's the easiest way I can explain it.
A lot of people confuse fatigue with stress. Stressing your CNS is what we do, fatigue is on the road to over training.
There are multiple types of CNS fatigue, atp depletion, metabolic by product accumulation, glycogen depletition, hypo(low glucose), microtrauma and the over stated central fatigue.

[IDrinkBloodLOL]

I'm just finishing a graduate level course in neuroscience. Please give me the detailed version.

Obviously strength goes down during "cns fatigue," yet paralysis does not occur, so what is the source of weakness? Is there some inhibitory input somewhere, or something limiting motor unit recruitment? If so, how does that work?

[kaleida]

I think it's a flawed idea personally. They're talking about a reduction in performance. But people who throw this "taxed CNS" phrase around don't realize that the performance reduction goes away - or how quickly it goes away.

Example:
Bob deadlifts 1x/week and his performance is consistent from week to week. The he tries deadlifting on Monday, Wednesday, and Friday in the same week. Performance declines on Wednesday and declines even more on Friday, and he concludes "deadlifts tax my CNS, I should go back to doing them 1x/week so my CNS won't be taxed"

Example:
Jane deadlifts 1x/week and her performance is flat from week to week, she's having trouble getting past a plateau. Then she decides to try an experiment deadlifting on Monday, Wednesday, and Friday every week. Initially her deadlift performance is reduced, but she keeps going with the experiment. After 2 months her plateau is broken and she's deadlifting more weight with better speed and consistency than she did before.

[IDrinkBloodLOL]

I think it's a flawed idea personally. They're talking about a reduction in performance. But people who throw this "taxed CNS" phrase around don't realize that the performance reduction goes away - or how quickly it goes away.

Example:
Bob deadlifts 1x/week and his performance is consistent from week to week. The he tries deadlifting on Monday, Wednesday, and Friday in the same week. Performance declines on Wednesday and declines even more on Friday, and he concludes "deadlifts tax my CNS, I should go back to doing them 1x/week so my CNS won't be taxed"

Example:
Jane deadlifts 1x/week and her performance is flat from week to week, she's having trouble getting past a plateau. Then she decides to try an experiment deadlifting on Monday, Wednesday, and Friday every week. Initially her deadlift performance is reduced, but she keeps going with the experiment. After 2 months her plateau is broken and she's deadlifting more weight with better speed and consistency than she did before.

That's my fear and suspicion - that the whole idea is just some broscience people repeat because it sounds smart, but without anyone stopping to figure out what the hell it is or how the hell it works.

Frankly fitness has taught me that nobody without an M.s. or better should never be allowed to talk about science, and that much as the catholic clergy used to deny its followers the right to read the bible for themselves, science would do well to keep itself out of the grubby paws of the unwashed masses a bit better.

Still, I have high hopes that somebody on this forum can explain this business to me - if not the correct theory then the origin of the false theory.

[kaleida]

That's my fear and suspicion - that the whole idea is just some broscience people repeat because it sounds smart, but without anyone stopping to figure out what the hell it is or how the hell it works.

Frankly fitness has taught me that nobody without an M.s. or better should never be allowed to talk about science, and that much as the catholic clergy used to deny its followers the right to read the bible for themselves, science would do well to keep itself out of the grubby paws of the unwashed masses a bit better.

Still, I have high hopes that somebody on this forum can explain this business to me - if not the correct theory then the origin of the false theory.

That would be nice but I don't think they know... I think they're just passing along what they heard from someone else. :P

I usually see "don't do that, it'll tax your CNS!" thrown around as a reason to limit frequency for big compound lifts like squats and deadlifts. I wish I had enough time to set this myth straight for the whole Exercises section.

Limit frequency because you are meeting all your goals with low frequency - fine.
Limit frequency because you enjoy low frequency better - fine.
Limit frequency because it doesn't fit your schedule - fine.

Don't limit frequency because you think your body is unable to handle it. Many, many people (including me) do large compound lifts with high frequency and it's working great for us. Yeah my CNS was, briefly, "taxed" ... and now I have many new PRs and the work capacity of a god.

I want to tell the whole Exercises section: If you think you can't handle high frequency, you're right. You can't.

[davisj3537]

In for future reading.

I've heard it explained a dozen different ways and I still understand relatively little about it. Spoke with the gf who is a dr and she says it makes no sense.

[SlipshodDread]

I think it's a flawed idea personally. They're talking about a reduction in performance. But people who throw this "taxed CNS" phrase around don't realize that the performance reduction goes away - or how quickly it goes away.

Example:
Bob deadlifts 1x/week and his performance is consistent from week to week. The he tries deadlifting on Monday, Wednesday, and Friday in the same week. Performance declines on Wednesday and declines even more on Friday, and he concludes "deadlifts tax my CNS, I should go back to doing them 1x/week so my CNS won't be taxed"

Example:
Jane deadlifts 1x/week and her performance is flat from week to week, she's having trouble getting past a plateau. Then she decides to try an experiment deadlifting on Monday, Wednesday, and Friday every week. Initially her deadlift performance is reduced, but she keeps going with the experiment. After 2 months her plateau is broken and she's deadlifting more weight with better speed and consistency than she did before.

Whilst what you are saying is true to an extent, and of course one of the main functions of the CNS is to adapt to the situations placed before it, there is of course a limit, affected by a variety of factors including; diet (the brain requires calories after all), sleep, muscle fibre composition, age, hormone levels etc. Eventually your CNS will simply not be able to adapt to the stresses placed on it, which is TRUE overtraining, not to be confused with what most people on this forum seem to think it is (poor programming).

Of course testosterone boosts the recovery of the body, including the CNS, which is why you can train longer, harder and more often on steroids, but this only raises the point at which your CNS can adapt, it does not remove it entirely.

But barring a neurological disease, the CNS of even well trained people should be able to adapt to whatever their body can physically take, provided the energy is available to recover.



Back OT:

The CNS is comprised of the Brain and Spinal Chord, and essentially controls the entire body, since all other Nervous systems in the body connect to it at some point.

Since I'm sure you're aware of the functions of the Brain, I'll leave that out, and obviously the Spinal Chord carries nerve information to/from the Peripheral Nervous System. The key relation of the CNS to weightlifting is it's control over the motor units and firing motor neurons to generate muscular contractions.

The Peripheral Nervous System includes the Motor Nervous System, which is split further into the ****tic Nervous System and Autonomic Nervous System. For weightlifting the focus is the ****tic Nervous System, which can be fired consciously and controls skeletal muscle. Obviously the Neuron pathways have to be built over time, and the more often they are used the faster and stronger the contraction can become, although this is partly related to the quantities of different types of muscle fibre comprising an individual's muscles.

Obviously the more ingrained a neural pathway is in the brain, the faster the neurons will be able to deliver the impulse to the muscles to contract, allowing for a more explosive contraction.

Eloranta 2003
-"Prolonged training in a specific sport will cause the central nervous system to program muscle coordination according to the demands of that sport."
-"the learned skill-reflex of the CNS seems to interfere in the performance of another task"

[I]Bompa[I] 2005
-Hypothesised "excitation" and "inhibition"
i.e. In order to achieve the strongest and fastest contraction of the muscles, the neural pathways need to be equally fast and uninhibited (clear and well defined)
-Fast twitch fibres are affected very detrimentally by CNS fatigue, greatly reducing the ability of those fibres to fire quickly
-Repetitions are the key variable for weight training in order to produce intense explosive movements. "1-3 repetitions, using loads in excess of 90% of 1rm" in order to optimise the contribution of the CNS to the lift. A rest period of 6 minutes is also suggested to provide optimum rest.
-"these do not provide a large increase in muscle mass, so are not detrimental to power to weight ratios"


It is believed that the CNS consumes around 20-25% of our daily calorie intake, so 800-1000 in my case, or 500-625 based on GDA for adult males. So I am assuming this is related to the reason why on heavy days it tends to be a lot easier to fall asleep, as the CNS is more tired. Of course that is only anecdotal, and not in any way scientific.

As for how the CNS itself would actually tire, I might as well make a dartboard up of obtuse and inaccurate reasons then give you the first one I hit.


Slightly unrelated to the topic:

There's a type of neuron known as a fine motor neuron, which Humans have in far greater abundance than animals, especially compared to the other great apes (Chimps, Gorillas, Orangutans). These allow us to achieve delicate and incredibly intricate tasks with great ease, but seriously inhibit our power production in muscles. For example if you've ever watched a documentary on any apes, you will see that while they occasionally use tools, they seem to find them much harder to use despite having semi-opposable thumbs. However Apes are many times more powerful than us relative to size, despite studies not finding a great difference in the levels of muscle mass/muscle density of humans compared to equally sized Apes.

It has also been hypothesised that our muscles have evolved to be very energy efficient for their strength, in order to save more energy for the brain.

[400Lb Gorilla]

I like how you ask for this section to aware you on the CNS, then you proceed to educate us

good read

Edit: nevermind got two different no avis confused

[kaleida]

Of course testosterone boosts the recovery of the body, including the CNS, which is why you can train longer, harder and more often on steroids, but this only raises the point at which your CNS can adapt, it does not remove it entirely.

Wait...does "you" in this sentence, plus the fact that you were replying to me, mean you think I'm on steroids? Please say yes. That's actually a long-time goal of mine...to have recovery abilities so godlike that people think I'm on steroids

[400Lb Gorilla]

Frankly fitness has taught me that nobody without an M.s. or better should never be allowed to talk about science
Still, I have high hopes that somebody on this forum can explain this business to me - if not the correct theory then the origin of the false theory.

way to contradict yourself. "CNS fatigue" is the normal broscience around here. It probably had some form of factual basis and then the bros took off with it to use as an excuse to slack on their programming

[SlipshodDread]

Wait...does "you" in this sentence, plus the fact that you were replying to me, mean you think I'm on steroids? Please say yes. That's actually a long-time goal of mine...to have recovery abilities so godlike that people think I'm on steroids

Well as much as I would like to correct you, I'm not going to kill your dreams haha

[kanis999]

I've always wondered why it isn't PNS.

[-Ironside-]

It's not all bro science, some of it is SCIENCE!!!!
There's a lot written here and I'm not a fan of reading long threads but I skimmed.
Let's cut through all the tape and get straight to central fatigue, not depleted atp, micro tears or any of that BS.
REAL central fatigue is in up in the noggin in that there brain. When you train heavily and intensely the impulses from the motor cortex of the brain to the muscles begin to slow down even if your muscles are still going well. This IIRC is called a 'central governor' which tells the brain "slow the **** down before you hurt yourself". The more you push it, the more your brain/body realizes it can go further and further.
So over training is often just in your head, physically. Train your CNS to take the abuse and you'll be able to go further. Keep in mind CNS fatigue can take 1-3 days to recovery from or as long as a couple weeks if you really push it.

[IDrinkBloodLOL]

It's not all bro science, some of it is SCIENCE!!!!
There's a lot written here and I'm not a fan of reading long threads but I skimmed.
Let's cut through all the tape and get straight to central fatigue, not depleted atp, micro tears or any of that BS.
REAL central fatigue is in up in the noggin in that there brain. When you train heavily and intensely the impulses from the motor cortex of the brain to the muscles begin to slow down even if your muscles are still going well. This IIRC is called a 'central governor' which tells the brain "slow the **** down before you hurt yourself". The more you push it, the more your brain/body realizes it can go further and further.
So over training is often just in your head, physically. Train your CNS to take the abuse and you'll be able to go further. Keep in mind CNS fatigue can take 1-3 days to recovery from or as long as a couple weeks if you really push it.

First answer truly to the point.

There was a long post above I will get to in the morning, not to say that it is wrong but to explain more that the info presented didn't cover what I asked, though it was good as general supporting info for the discussion.

This however is perfect. So it's like inhibition in the prefrontal cortex or something, inhibition that is actually in the CNS?

That would both explain why the broscience is wrong and the truth that inspired it.

[SlipshodDread]

First answer truly to the point.

There was a long post above I will get to in the morning, not to say that it is wrong but to explain more that the info presented didn't cover what I asked, though it was good as general supporting info for the discussion.

This however is perfect. So it's like inhibition in the prefrontal cortex or something, inhibition that is actually in the CNS?

That would both explain why the broscience is wrong and the truth that inspired it.

Yeah I'm aware it did not cover exactly what you were asking, however I hadn't looked very far into the subject until earlier tonight (currently 12:15am).

As you said though, Ironside pretty much nailed it.

[davisj3537]

Just had a good 45 min discussion with the gf about this. We spent quite a while digging for credible sources on this topic and they seem to be only speculation and no quantitative research under decent conditions.

Just a ton of speculation about neural recruitment issues leading to efficiency reduction. I'm quite disappointed:/

[IDrinkBloodLOL]

Just had a good 45 min discussion with the gf about this. We spent quite a while digging for credible sources on this topic and they seem to be only speculation and no quantitative research under decent conditions.

Just a ton of speculation about neural recruitment issues leading to efficiency reduction. I'm quite disappointed:/

It's of interest because it's so foreign to me. I hear it's something low rep lifters have to consider, but I'm pretty much exclusively a high rep lifter so it's nothing I ever encountered. Have you run into it?

[davisj3537]

It's of interest because it's so foreign to me. I hear it's something low rep lifters have to consider, but I'm pretty much exclusively a high rep lifter so it's nothing I ever encountered. Have you run into it?

I'm with you. This is something I've never really understood. Especially from a PL perspective I'd love to know more about it.

Having written my own programming long enough I've run into this "CNS fatigue" phenomenon half a dozen times or more. There is something to it, but without some studies dedicated to PL lifting intensities and how that relates to nuerons, "CNS" and whatever else we won't have a real concrete answer I'm afraid.

It simply can't be a coincidence that nearly all programs have some sort of deload built into the programming. It just can't...

[chazzy1864]

In regards to the science behind it, I couldn't tell you, but i have personally run into actual overtraining. First time, came during a period where I was doing my lifting routine, adding in lots of extra cardio (to include HIIT sessions) and cutting. I completely exceeded my recovery ability by having far too few calories for the amount of work I was doing. I was adamant about my sleep and always got at least 8 full hours of sleep. No matter that, within 1-2 hours of being at work, people were asking me if I had a late night the previous night. I was always tired and worn out. Finally, with a PT test looming at the end of the week, I decided to cut out all of my exercise and grubbed out with my friends from Tuesday - Thursday. By Friday I felt so rejuvenated it was crazy. I was breezing through my PT test and then my subsequent workout later that day. Wearing myself down was a gradual process, so I didn't realize how bad it had gotten. I just knew that my workouts were tough to me. Once i was refreshed, it was a night and day difference.

Since then, I've been able to identify when I'd start to overreach and will back off. Sometimes when I'm stubborn, I've still worn myself into the ground and end up getting flus and what not. Generally, it happens during periods when I'm cutting and/or periods of work that require lots of work and my sleep starts getting messed up a lot.

[Silvercock]

Obviously strength goes down during "cns fatigue," yet paralysis does not occur, so what is the source of weakness? Is there some inhibitory input somewhere, or something limiting motor unit recruitment? If so, how does that work?

Thats like implying being tired is broscience, you're either full-on or paralyzed.

From what I've been told the neurotransmitters get depleted. It affects rate encoding so you can no longer fire the largest motor units as hard.

But I do believe CNS specifically is tossed around too loosely, it should be NS in general both central & peripheral if you wanna get technical but the points being made in regards to the issue are the same regardless so its not worth it to be anal about it.

[IDrinkBloodLOL]

Thats like implying being tired is broscience, you're either full-on or paralyzed.

From what I've been told the neurotransmitters get depleted. It affects rate encoding so you can no longer fire the largest motor units as hard.

I'm aware paresis exists. Woodrep for any source on the neurotransmitter thing though.

[cbrown386]

From what I've been told the neurotransmitters get depleted. It affects rate encoding so you can no longer fire the largest motor units as hard.

This is how I understand it as well.

Deadlifts, for example (often cited to cause CNS fatigue), require the firing of almost every motor neuron to properly complete the lift. For a 100% maximum effort deadlift, your CNS must fire absolutely everything to get that weight up. Try that weight again in five minutes, probably not going to happen. It's not that the muscles are so fatigued from the single rep, but the muscles can no longer all fire at 100% until the system recovers.

That said, from my experience, CNS fatigue only arises from maximum effort, maximum muscle recruitment lifts (Deadlifts, mainly). Deadlifting three times per week is not detrimental if you are not working at maximum effort. However, I think it would be rare to find someone who truly maxes their deadlift more than once per week without seeing adverse effects on other lifts.

[davisj3537]

The gf was saying something about charged ions facilitating the exchange of electricity to fire the neuron and therefor the muscle fiber. Much like a lightning strike...one side gets a positive charge and the other is negative and now the electrical connection can be made to fire the muscle fiber. She described it as each neuron is attached to a single muscle fiber and but there isn't only one neuron per fiber.

During the ion exchange the muscles fire. Now before the neuron can fire and activate the muscle fiber again it must recreate the positive/negative charging of the ions to facilitate another exchange of electricity. With enough use of these neurons, they can be slower to recharge and facilitate another electrical exchange.



(I may have bastardized this whole thing, but this is how I understood our conversation.)

[IDrinkBloodLOL]

This is how I understand it as well.

Deadlifts, for example (often cited to cause CNS fatigue), require the firing of almost every motor neuron to properly complete the lift. For a 100% maximum effort deadlift, your CNS must fire absolutely everything to get that weight up. Try that weight again in five minutes, probably not going to happen. It's not that the muscles are so fatigued from the single rep, but the muscles can no longer all fire at 100% until the system recovers.

That said, from my experience, CNS fatigue only arises from maximum effort, maximum muscle recruitment lifts (Deadlifts, mainly). Deadlifting three times per week is not detrimental if you are not working at maximum effort. However, I think it would be rare to find someone who truly maxes their deadlift more than once per week without seeing adverse effects on other lifts.

Look up the phos****en system. Thus is not nervous in origin at all.

Davisj: that is the basis of all neuromuscular junctions. She is effectively describing what they call habituation; nerves fire less in response to stimulus.

In the event this whole thing were from lack of transmission at the neuromuscular junction then there are drugs that would actually help that.

So far I remain convinced it's either as ironside said or top tier broscience, right up there with mind-muscle connection and calorie counting.

[SlipshodDread]

If there is a scientific basis for it, most likely mentions of specific nervous systems within the body have been seen by someone without a great degree of understanding, and have settled on using the CNS as a fall back in order to sound technical with the "bros". Since almost all of the websites generated on a search of "CNS fatigue" are weightlifting websites, it seems to have been propagated from very little.



From my experience of lifting heavy it seems to be the case that at a certain point you become unable to generate the necessary force, without any muscle fatigue. Although the lack of muscle fatigue may be due to the amount of time spent actually lifting being too short to generate any significant lactic acid build ups.

When doing benchpress the other day, I finished my warm up sets and started at 110kg (242lbs). I managed one easy rep, and whilst the second felt easy off the chest, about 3/4 of the way through I became unable to generate any more force and became "stuck". By stuck I mean that the weight was completely stationary, and my muscles were generating a force exactly equal to it. Dropped it down to 105kg for the next set and the first two were easy, but the third barely came off the chest at all, although this may be due to failing on the previous set. After that I dropped it down to 100kg to do triples for the last 6 sets, and oddly the easiest set was the 4th at 100kg (6th overall, excluding warm ups).

As for CNS "fatigue", I can say that I feel absolutely shattered after my heavy workouts when compared to my hypertrophy workouts. However this effect only lasts for that night.

I have been training heavy 5-7 days a week for the last 8 weeks, plus my temporary job doing manual labour (removals, so lifting awkward **** all day) on weekdays, combined with sub-optimal rest (about 6-7 hours compared to the preferred 8) and a diet with only a slight caloric surplus, yet despite those factors my lifts are ALL increasing week on week, and even when a lift did stall (shoulder press) that was only for a single week. So based on that I would say that using CNS "fatigue" as an excuse for overtraining would be poor, even IF a mechanism is found that actually explains the theory.

All that despite what I keep on hearing about deload weeks, although having said that, they can be useful to avoid over-stressing the tendons since those take a longer time to adapt than the muscle. As far as deloading to avoid over-stressing the CNS goes....

[PancakeTragedy]

In for brain gains.

[-Ironside-]

duuuude, IDrinkBloodLOL, you got me in your sig. I feel like we should hug

[Jasonk282]

The body can take a lot more abuse than your mind can. Mentally you'll want to stop long before your body does. We specifficly trained for this type of mentality during RECON training. 2-3 hours of sleep a day 2 meals if we were lucky. Nothing but physical and mental abuse to our bodies and minds.

Well their might be some truth behind it I think CNS taxing is used more of an accuse..much like overtraining.

As we say...improve, adapt, overcome.

[-Ironside-]

The body can take a lot more abuse than your mind can. Mentally you'll want to stop long before your body does. We specifficly trained for this type of mentality during RECON training. 2-3 hours of sleep a day 2 meals if we were lucky. Nothing but physical and mental abuse to our bodies and minds.

Well their might be some truth behind it I think CNS taxing is used more of an accuse..much like overtraining.

As we say...improve, adapt, overcome.

I agree and since we got the same type of background you know exactly what it's like to be on complete mental shut down while you're body is still going.
I remember being on day 5 of sleep dep and seeing dudes walking like zombies, weapons dragging behind them, eyes completely blank but still moving. I had a good conversation with a giant sea horse that day. Our bodies are resilient but the mind can only stretch so far before it shuts down.