WHAT IS CNS FATIGUE really?

Expert Discussion Advanced Sports Sciences
81

I am back from vacation, and I see that there was a “hot” discussion going on without me :frowning: … Why no one called me :slight_smile:

Before I start, I would suggesting looking at the following links:

Homoeostasis Performance Model

Spinal and Supraspinal Factors in Human Muscle Fatigue

*** Looking at Acute Adaptation chapter in Enoka’s Neuromechanics of human movement is also GREAT starting point!

Regarding “CNS Fatigue”, as a result of mine and Lorien’s discussusion in Homoeostasis thread, I can say that we MUST differentiate between two different aspects (altought not neccesarily distinct) of “CNS Fatigue”:
1. Reduction of CNS output due protective mechanisms to protect the body
2. Reduction of CNS output due physiological impairments in neural cells (centrally) itselfs

*** There may be addition to process n2 ---- protection of the CNS itself — preventing impairment of neural cells before it happens

Both of these “processess” act together, but sometimes one dominates…

---- CNS fatigue in marathon (process n1)
Reduction of CNS output due protective mechanism to reduce running power and thus prevent homoeostasis in muscle cells — depletion of glycogen, depletion of liver sugar, dehydration, temperature maintenance, etc.
Thus, CNS fatigue also happens in marathon as a Central Governonr (Noakes et al) to prevent homoeostasis breakdown of the body. This can be called Extensive CNS Fatigue

---- CNS fatigue in sprinting (process n2)
Altought the degree of MU recruitment is limited by inhibition (protective mechanisms—process n1), there may be actuall impairments in neural cells due overwork due high frequency of firing… is this the resuls of lack of neurotransmiters, lack of energy for Na/K pump, ionic balance deeoriation etc. who knows — but the result is decrease in output. This can be called Intensive CNS fatigue.
The thing that confuses me the most is the interesting property of Intensive CNS fatigue, naimely its delay!!! Thus during sprinting session your performance (speed) doesn’t deteoriate (decrease), and you are rather in the state of potentiation. But after some time (couple of hours) if you try to run again you will suck. So you need to rest 48-72h to run optimally again. So, is there really impairments in neural cells during running (sprinting)??? I would say that after potentiation and high CNS stress (great recrutiment) Intensive CNS fatigue happens hours later to allow better refreshment of the body as a whole and thus prevents another CNS stress for some time…

What do you guys think about this?

82

Regarding Intensive CNS fatigue’s delay property:
Can this be due Autonomic NS or Adrenal Fatigue? Thus, during sprinting workout, hormonal environment is at its peak, and its maintained for some time (hormonsin blood etc), but after hours another later they are breaked down, and another try to enter this zone again will result in failure (lesser performance) due “drained” glands or cell receptors??? Thus, you need to recover your hormonal system…
It seems that everything affects everything here… CNS fatigue may actually be the results of another impairment not CNS impairment (if such thing exists)…
We should look at the things from “complex system approach” perspective… Screw the reductionism! :slight_smile:

83

im a little confused by the question but i will answer the best i can, tell me if im barking up the wrong tree. after i train i am not fatigued like i normally would be performing a typical training regeiment. i could and do train more than one time a day and depending on type of training can see improvement from one session to the next. now improvment can conissit of load, velocity, body position, time and so on. if your asking if i could max in the morning and then max in the evening then yes i could but only would if my training goals called for it. i train 6 days a week and never experience soreness or becoming tight (i beliebe this is becasue i spend alot of training time in the extreme joint position , ie the muscle is forced to contract while elongated). i hope this addressed your question let me kno if i was off point.

84

i do agree the CNS controls everything but its control can be broken up into traits, and this is where training becomes a psuedo science, which almost all training is. i believe charlie stated that coaches concieve and institute training methedology far before science proves it to be beneficial.
recently however i have seen evidence that processes occur in areas other than the brain for example reflexes are controled at the base of the spine. in training we want for trained movements to become reflexive, you dont want to think about what muscle u have to contract when running or jumping. so concepts like the alpha gamma loop, interneurons ans the such become important when considering performance. but you are absoulutly correct for saying the CNS controls all that is why it is so important that we train it and allow the perephrial to adapt to meet the structual requirements of the adapted neural system.

85

mostly i agree with your first point but you do get situations where perephrial minded training has an adverse effect on the central system. for example if you train in a bodybuilder type manner you instill incorrect movment patterns in the CNS. your muscles were not meant to work alone but all together.

there is indication that the sum is greater than is parts. all the traits are connected to a certain degree. and this connection makes it possible to monitor the state of the organism as a whole at any given point in time.

the question about how to organize training is a good one and i believe it the most overlooked part of training. most people will say o well you need this many days of recovery when that is never the case simply becasue people are different. in the attached file is a graphical representation of what i believe the best way to control induced training stress. the top pic depicts a scheme where a defeciet is induced in the organism, the longer this defeciet is maintained at the level (5-7%) the higher the subsequient supercompensation. this differs from regular training in which you induce fatigue and supercompensate one after the other.

86

interesting so the low/high frequency is related to rate coding. personally i am not concerned with low frequency rate coding as i am training for high power explosive sports. high rate coding and motor unit recruitment are what intrests me and then being able to perform at this level over and over anytime a multitude of times.

87

Underlying factors causing low frequency fatique are still critical to consider in activities requiring high rate coding as those fatique parameters are measured with electric stimulation.

e.g. direct malfunction in calsium cinetics and inhibition through group III and IV afferents may still lower voluntary capacity for explosive force production.

88

see my previous post, the study by Raastad:

"all performance measures showed the same pattern of recovery after the 100% protocol. there was a drop in performance of 12-22% post-exercise, Recovery was biphasic, with rapid recovery occuring during the first 11 hours, followed by a levelling off or a second drop in performance until the next morning, 22h after exercise, All variables returned to baseline levels after 33h after exercise. "

Do you have any additional references/anecdotical evidence that it takes 48-72 hours to be able to perform again?

And: is this time span of recovery very dependent on the total volume. How much volume (minimum) is needed to improve?

89

Duxx I am interested to know because you seem be torn apart by reductionism and generalism(system approach) at the same time:

Why do we need to recover faster?

Can we improve (only) by larger volume? Charie stated in Speed trap, that the real effects might lie in intensity.

Playing devil’s advocate: should we aim for higher intensity and thus lower volume during SPP if performance level is going up? THis might be important to combat injury risk as well.

90

I understand your point, you do not experience DOMS after your training.

My point was that IF you experience DOMS or CNS fatigue, that at that moment it is well likely that you are not able to perform at normal standard.

What you said earlier makes perfect sense in my opinion. DOMS and CNS fatigue may be for a large part independent of a simple phenomenon like muscle damage (after eccentrics). Multiple factors (besides structural damage, also emotion and the like) act on the same system.

The brain is specialized in solving a movement problem (getting the task done). It has a lot of possibilities to do that. However depending on context, some possibilities might be inhibited.

I am sorry to be a bit longwinded. I hope we can get this conversation going further

91

[QUOTE=james colbert]mostly i agree with your first point but you do get situations where perephrial minded training has an adverse effect on the central system. for example if you train in a bodybuilder type manner you instill incorrect movment patterns in the CNS. your muscles were not meant to work alone but all together. [end quote]

First of all, nice post!

I cannot agree more with the above post. You can certainly get into trouble by training that way: you want to drive your ne car in the same way as your old car, but it is different from your previous car

there is indication that the sum is greater than is parts. all the traits are connected to a certain degree. and this connection makes it possible to monitor the state of the organism as a whole at any given point in time. [end quote]

The question might be that you need some optimal task-specificicy (so looking at the abstract level of the task at hand, not looking at traits or motor abilities).
In order to peak you might need time off and time on.

[QUOTE]the longer this defeciet is maintained at the level (5-7%) the higher the subsequient supercompensation. this differs from regular training in which you induce fatigue and supercompensate one after the other.

Can you expand on this one? You state that the longer the defeciet, the higher the supercompensation.
Do you have anecdotical/other evidence for this idea. You state that you need to train in a fatigue state to get supercompensation.

My idea is somewhat different: I attack the problem like this: a person needs to learn a certain task in a certain context. It is like learning a monkey a circus act. There might be physiological adaptation rules, but there might be learning rules as well (the basis of adaptation theory is metabolic physiology (recovery of metabolic substrates), which might be far too simple). Learning rules might include things like sufficient variation in context to show a stable motor skill in all contexts (for example different tracks, different emotional states, distraction noises).
How much fatigue is then necessary to improve. You need fatigue if you need to perform a motor skill in the context of fatigue (for example the last 100m of a 400m). Do you constantly need to be in fatigue to improve performance? Or can we do something different: supercompensate between sessions?

I agree with you that some “traits” might show faster or slower supercompensation. However I am only interested in the main task (e.g. sprinting 100m)

92

This is called dose-response! The dose depend on the athlete level and its adaptability and recoverability!

Only Charlie’s opinions/experience…

As Charlie stated: the volume should go DOWN to allow intensification!
The common sense is to increase volume of HI training with elite athletes, but contrary you should do the opposite…

I didn’t say that… all I want to know is the “mechanism” of fatigue phenomena…
Adapt training to recovery ability of a particular athlete!
Sijmker,
you seem like a nice guy… Glad to see you on this forum! Keep posting bro! :slight_smile:
BTW: I would really love to see the literature foundation of you opinions… not to question you but to take some good read you might suggest! Thanks!

93

Question: is this does dose-respone a monotonically increasing curve, or is it an inverted U, meaning that there is a optimum. If there is an optimum: how much do you administer to athletes? Does that depend on “adaptability and recoverability” only? There are advocates of holding back a little all the time, with now and then a maximum dose (for example Pavel Tsatsouline with regard to weightlifting).

I do not know what literature I would recommend to you. I think the works of Nicholas Bernstein or better Theo Mulder (unfortunately his books are only in Dutch) (the German translation “Bewegungsphysiologie” from Bernstein for example, I do not know whether you can read the original Russian texts).
Bernstein looks at movement as problem solving by the brain. It’s an interaction with the environment. Movement always takes place in an environment (physiological, emotional, cognitive, physical [external]). To what extent is running 100m and marathon a circus act that should be learned (contextual motor learning)

Traditional training theory and the adaptation models look at recovery pattern of metabolic substrates / muscle development. Verchoshanski has allready stated that most "adaptation science"lack biological underpinning. I agree with him. Maybe motor learning should be a input for further development of training theory.

94

Does anybody have any thoughts on CNS Fatigue and how its effected by doing split sessions as opposed to single session.

I.E. Charlie would have his sprinters do weights after sprinting due to time/work constraints (8 hour jobs/school) and also to allow the CNS a full recovery for the next sprint/weight session 48 hours later. A benefit to this method may be muscle memory, you sprint fast so therefore you might lift better.

If one does not follow this prescription (sprint then weights) and instead an athlete would want to maximize his workouts in sprinting and weightlifting by doing the weightlifting 4 hours later how would this affect CNS fatigue.

So using method 1 (sprint then weights immediately after) a person would sprint at say between 4-6pm and then do weights from 6:30-7:30pm. Then sprint again 44 hours later starting again at 4pm.

Method 2 (sprint then weights 4 hours later), a person would sprint at say 1-3pm then do weights at 7-8pm. Then sprint again 41 hours later.

Well I guess I can see the using method 1 allows for 3 hours more recovery time but method 2 allows for more intense weightlifting sessions. But I guess one thing I’m forgetting here is that in method 2 the CNS has recovered a small amount in the time between the sprint session and weight session (4 hours). Therefore, an athlete could utilize the fact that testosterone levels go down after 60min of exercise and therefore method 2 allows better weight workouts. The Bulgarians use method 2 (and variations of it) and won many medals and dominated weightlifting and still do.

So a question I would like to pose is how much is the CNS Fatigued in both methods and which one do you see as being the better method for CNS recovery.

95

It is an inverted U — thus there is an optimum (moving optimum). Tim Noakes, in one of his principles of training, stated that one should seek to bring result with minimal load—thus searching for the minimal stimulus to provide optimal level of adaptation.
This curve “changes” over time, thus begginers tendneed to need very low loading to progress and their “top of the curve” is pretty long (thus you can bring optimal adaptation with wider zone of load). With elites and injured people, the situation is little more problematic, because “top of the curve” is narrow — thus if you use less load they (elites) will detrain, if you use slightly more they will overtrain. Same thing with injured people: if you use slighlty more load they will re-injure!

Nice to see another proponent of Bernstain!!! I am very familiar with his work! (My No1 course is motor control — I actually developed one model : an extension of Lambda Model). Bernstain stated that the goal of motor controler is to overcome the problem of redundancy: infinite solutions for particular problem. Take a look at Homoeostasis Performance Model!
Latash wrote one book (Dexterity and its development) in which he translated some of Bernstain’s work, altought there is Bernstain’s “Coordination and regulation of movement” book on english! Glad to have you here on this forum bro! Are you a student? Researcher?

96

hi Duxx, I agree with your post. This is als my guess. I think we can theoretesize a lot, but we should find the minimum necessary to get improvement I think (to stay away from injury and to get a long career with lots of successfull events building on each other).

I am a researcher, on a whole different topic (arm, shoulder and neck symptoms among computer users).

Besides, I coach national level middle distance athletes.

My education (human movement science) included motor control and neuroanatomy next to behavioural change theory.

I have had a look at your models, they have a real depth in theory. However, for me it is not yet clear how this model would change my coaching practice. Have to look it up. A theoretical approach is only usefull if it defines what to do in practice (my opinion)

regards
Stefan

97

[QUOTE=sijmker][QUOTE=james colbert]mostly i agree with your first point but you do get situations where perephrial minded training has an adverse effect on the central system. for example if you train in a bodybuilder type manner you instill incorrect movment patterns in the CNS. your muscles were not meant to work alone but all together. [end quote]

First of all, nice post!

I cannot agree more with the above post. You can certainly get into trouble by training that way: you want to drive your ne car in the same way as your old car, but it is different from your previous car

there is indication that the sum is greater than is parts. all the traits are connected to a certain degree. and this connection makes it possible to monitor the state of the organism as a whole at any given point in time. [end quote]

The question might be that you need some optimal task-specificicy (so looking at the abstract level of the task at hand, not looking at traits or motor abilities).
In order to peak you might need time off and time on.

Can you expand on this one? You state that the longer the defeciet, the higher the supercompensation.
Do you have anecdotical/other evidence for this idea. You state that you need to train in a fatigue state to get supercompensation.

My idea is somewhat different: I attack the problem like this: a person needs to learn a certain task in a certain context. It is like learning a monkey a circus act. There might be physiological adaptation rules, but there might be learning rules as well (the basis of adaptation theory is metabolic physiology (recovery of metabolic substrates), which might be far too simple). Learning rules might include things like sufficient variation in context to show a stable motor skill in all contexts (for example different tracks, different emotional states, distraction noises).
How much fatigue is then necessary to improve. You need fatigue if you need to perform a motor skill in the context of fatigue (for example the last 100m of a 400m). Do you constantly need to be in fatigue to improve performance? Or can we do something different: supercompensate between sessions?

I agree with you that some “traits” might show faster or slower supercompensation. However I am only interested in the main task (e.g. sprinting 100m)

sprinitn or anyother activity can be broken in to traits and then further into their sub-traits. so though you may be traiing for the 100m all have to be addressed for the best performance. my concern is largly with supercompensation of the CNS and this does not occur in my opinion on a substarte level. this occurs by a reorganization of motor patterns in a very non-physical sort of way. but basica adaptation theroy as a whole should not be looked upon as training metabolic facilities or CNS ones, it is the adaptation as a whole of the organism. this is very important to the deficiet of 5-7%. basically the longer you can hold this level of over training the greater the supercompensation. this was knowledge was gained through talking to its creator and user of 30 years and personal expereience. if you could hold the level for a year people would probably think you had been replaced by your twin who had been trianing for the past 6 years to be an elite athelte.

98

the problem with movement being problems solving by the brain is sometimes indiviuals are lazy and the brain isnt that good at solving the problem. you can look almost everywhere and see motor problems with the bulk of the population, even in elite athletes.

99

Supervenom–I’d be very interested in the responses to your question for recovery of CNS fatigue. Due to work, family, etc when I do split sessions many times they are quite a few hours apart, sometime as many as 8 but still in the same day (for instance, I may be able to sprint sometime over the lunch hour, and then start lifting power cleans and such at 8 or 9 p.m. once the kids go to bed). I don’t think I’ve seen or felt very many issues with it but would be curious what the rest of you think–am I still getting the most bang for my buck or have I entered the resting phase and shouldn’t do any lifting at night and wait the 48 or so hours until next time?

100

That might be true. However, I am interested whether training should focus more on training in different context, so that the motor pattern is more stable and generalizable across conditions. As Bernstein stated you cannot perform two movements in the identical matter (“repetition without repetition”), there are allways small differences. The state of an organism also tends to change from moment to moment (think about emotional state)

How can we get these differences at minimum?