Homoeostasis Performance Model

Homoeostasis Performance Model is a synthesis between Noakes’s Central Governor Model and Schmidt’s Conceptual Model of Human Performance. Some of the Bernstein’s conclusions about motor controler, who controls human movement, were:

  • Control system is hierarchycally organized on couple of levels
  • There is a feed-back that connects lower parts with higher parts of control system, which is used to adjust motor comands
  • Time lag between neural connections finaly leads to a need of combining signals from feed-back with feed-forward preprogrammed, anticipatory signals
  • Number of degrees of freedom of the motor system is always bigger than needed. System is redundant and the control can be viewed as the process of solving redundancy problems (finding the optimal control strategy – learning)

So basically, skill is a result of the process of searching the optimal solution for a particular motor task/problem. Abilities are the undelying (hiden, latent) factors that affect performance and skill. But abilities are also measured via performance, so there is no such thing as a crisp boundary between skills and abilities. When you want to measure strength, you can give someone to do 1RM squat. But doing squats takes skill to accomplish, especially with begginers. So, I would say that stregth is a skill, rather than a some hidden, latent factor – ability. Same thing for a endurance, speed, flexibility, agility and other.

I am not saying here that there is no such thing as abilities, but I am saying that it is hard (or maybe impossible) to put the line be between skills and abilities, because they are interelated, and cannot exist by themself alone.

It is quite helpfull to look at the things that, specific skill uses specific abilities to solve specific problems. If there is no needful development of underlying specific ability, then the skill cannot be learned nor performed. It is imposible to teach someone to squat 200kg with proper skill (technique) if his level of strength (ability) is poor. Same thing with sprinting form. It cannot be learned nor reached if the underlying strengths and flexibilities (and endurance to maintain it) are not well developed. Pushing the athlete to do something he cannot do because of the lack of underlying abilities is only frustrating and can lead to injuryes.

Skill is NOT such thing as stereotype or fixed patter (of muscular activation), but rather a dynamic, complex, continual motor problem solving. To teach some skill, you should not give answers but rather questions.

Ability structure makes things more complex, because there is no consensus about their number nor interrelation. This is also one more proof that the line between skills and abilities is hardly made. There is one general ability which correlates with every other. Is is coordination. Coordination is specific ability to control movement, but there is also a number of types of coordination. This makes things more complex. We can look at the coordination as the connection between skill and abilities.

Skill / Coordination / Abilities Relation


Abilities Complex Structure

There is a trend in Serbia to develop coordination with youth, which can help later with learning and performing sport specific skills. The question is can coordination be developed, by the way, there is different types of coordination. I am thinking that giving kids a various exercises does not improve coordination (or it is) but rather enrich their motor space, so there is a skill transfer later in their sport development to more specific sport skills. This is not the issue here, so we are going to leave this debate for some other time.

So what the hell is new here? What new does Homoeostasis Performance Model bring to the world? This was just an introduction, so lets start…

The main thing that Homoeostasis Performance Model brings is the integral approach to study human movement. It is time to stop reductionist approach dividing motor control for creating movement and physiological metabolic/energy systems that maintain life. The human acts as a whole and thats the way it should be viewed and explored.

The main principle/concept of Homoeostasis Performance Model is that movement is allways done within the limits of homoeostasis (in healthy humans). I will first explain my point of view for „movement“, then for „homoeostasis“ and finaly for their interaction.

Movement is an interplay between stability and mobility. To allow movement to happen, at the specific instant of time, some joints must be stable and stiff, while others must be mobile. Movement is an act of the whole body (not just muscles according to this model), even when you move your little finger, your whole body moves. Take an example. Stay upright with your arms by your side. Quickly rise your arms. Which are the muscles that activated first? Deltoideus? Not exactly, your leg and core muscles, because they must maintain your whole body balance and prevent you not to fall, and also, they have to maintain the stability of the individual joints (spine). This is an example of anticipatory postural adjustments. Because system is redundant, which means that there is unlimited number of solutions, motor controler must find the best/optimal way to produced desired movement and to solve desired motor task. This is a process of searching. This is the motor learning, finding the optimal control strategy to solve some motor problem. The result of this searching (motor learning) is the motor skill.

Muscles produces forces (torque) and, in the same time, stiffness (short range active stiffness) which allows them, with the pair of their antagonists, to stabilize joints and to move joints.

Movement is bigger then the sum of its components, so trying to isolate one movement (and muscle) is misleading and errorneous. As Zatsiorsky stated, we are not trying to imporove our muscles but rather our movements. One my friend, when someone asked him, while doing cleans, for what muscle is that exercise, he answered: „Do you know that muscle that works when you jump to catch a ball under the baskett? It is for that muscle!“.

Homoeostasis is an inner (only inner?) physiological enviroment that should be stable and maintained under narrow boundaries to maintain life. Take the body temperature for an example. Body temperature is about 37C, but when it crosses 44C or fall below 33C, you die! End of story. So to maintain life, your body must control its internal enviroment (its state). There is a lot of variables that should be controled: body temperature, blood sugar, hydration, nutritional status of the blood, biochemistry status of blood, pressure and a lot of others. Dont forget that between them is a strong correlation and interaction, so your control mechanism have a very complex job to do to keep you alive.

To maintain homoeostasis, control mechanism have couple of systems to help him (executables). That includes circulatory system, respiratory system, digestive system, termoregulatory system, urinal system. Control mechanism comunicate between them via hormonal system and neural system. It is hard to find localization of the homoeostasis control system, because same as motor controler (are they the same?) have hierarchical structure and it is widespread over the body. Sometimes it is said that hypotalamus is the main controler, but I think it is maybe just one (highest) part, because a lot of organs have their control systems in themselves.

To maintain life, control mechanism have to find the optimal relation between different variables which defines homoeostasis, but again, it have to find optimal way controling-keeping them in the narrow ranges. I dont know is the human body one state system (representative point), but something tells me maybe it can have couple of stable states and switch form one to another as a result of training or some sickness.

If we take some paralels with cybernetics and automatics, homoeostasis control mechanism need to have defined goal of control (relation between variables – representative point) which there is maybe more of them, algorithm or optimal control to maintain it within narrow ranges (the process of searching) and gain which helps him to do it quickly and effectively. We can look at the gain as a functioning of physiological systems (heart, lungs, blood etc). Making them more efficient, creates greater gain in the systems and thus allows homoeostasis control mechanism better control and maintaining of homoeostasis.

Are these two systems really separated or not? Homoeostasis Performance Model states that they are not! According to this model, movement is allways done within the limits of homoeostasis and the homoeostasis is never lost (in healthy humans). If there is a threat to homoeostasis, movement is stoped or altered. Take an example of exercise in altitude. Do you expect to find more or less lactate in the blood? You expect to find more, but contrary you found less, because motor/homoeostasis controler shuts down-decrease the muslce activation to maintain homoeostasis. The feed-back to the motor/homoeostasis controler from the muscles and other organs via III and IV afferent fibers, informs it about what is happening „down-there“ – is there a threat to exit from homoeostasis? This is a new concept added to classicaly Bernstein motor controler. Controler gets feed-back information form chemoreceptors at the periphery and acts by increasing the functioning of heart, lunges and other physiological systems or by decreasing/altering muscle activation for the goal of maintaining homoeostasis. Controles only permits movement within the ranges of homoeostasis.

Homoeostasis Performance Model brings another point of view at the fatigue. Fatigue is not a physiological impairment, but rather protective mechanism that acts as body trys to leave boundaryes of homoeostasis (which starst at the onset of exercise). Sense of effort (RPE, rate of percieved exertion) is a concious perception of subconcious (underlying) integrative effort of control mechanisms to maintaing homoeostasis.

To improve you performance you must improve your motor skills and ability to maintain homoestasis. That includes improving you control strategy (learning) for both motor controler and homoeostasis controler which is done by practicing. Motor controler develop skill, and homoeostasis controler develop optimal control of heart, lunges, urinal tract etc. Both of these two result in pacing strategy, as an example, in running. Also, you must develop the gain in the system, as a result of training adaptation. Gain in motor controler represents motor abilities, and in homoeostasis controler represent functioning level of heart, lunges etc. And finaly you must improve you mental ability of „pushing“ or stimulating homoeostasis controler while it de-stimulates you with sense of effort (or RPE).

It is obvious that I differentiate between learning and adaptation. Learning represent searching for the optimal control, and adaptation represent increasing the system gain. They are different but interconnected. Both have to be improved for the performance to improve.

According to Homoeostasis Performance Model, endurance is a ability to maintain homoeostasis. It is maybe most fundamental ability (?) more than strength, because also when you push 1RM bench press, it takes time, and for that time homoeostasis must be maintained. This includes joint stability, tendom integrity etc.

There is alway reserve for life-threating situations. Movement is allways done within the boundaryes of homoeostasis. Dont forget that homoeostasis controler is still learning and that internal/external enviroment is always changing, so sometimes it cannot compensate for the changes, and injuries happen! There is also a posible threats with psycho-stimulans usage, because it affects you „pushing it“ too much.

Note that for the purpose of better explanation I splitted this controler to motor and homoeostasis but really they are the same.


Some questions?

If this controler limits maximum force to maintain tendon and joint integity and prevent muscle injuries, why then there is a difference between concentric and eccentric force in vivo conditions as in vitro, and why there is bilateral deficit? Why those forces are not the same?


12.december 2005.

To allow best performance, as said, you must improve your skils and ability to maintain homooestasis (and mental abilities). Homoeostasis could be more expanded into conserving joint integrity, tendon integrity, avoid muscle strains and sprains etc. So, to develop maximum performance you must develop skill and underlying abilities with specific high-intensity
training, but aslo you must maintain your ability to maintaing homooestasis by doing lowintensity general work to improve capilarization, heart and luns function, tendon and joints.
From the point of Homoeostasis Performance Model, Francis HI/LI approach is highly approved and correct!

13.december 2005.

It is important to note that while organisms exhibit equilibrium, their physiological state is not necessarily static. Many organisms exhibit endogenous fluctuations in the form of circadian (period 20 to 28 hours), ultradian (period <20 hours) and infradian (period > 28 hours) rhythms. Thus even in homeostasis, body temperature, blood pressure, heart rate and most metabolic indicators are not always at a constant level, but vary predictably over time (from Wikipedia, homoeostasis term). This waves-oscilations in biorhythm affects performance. As I stated before (thread X) training should adapt to these waves (providing unloading when needed) and on the other hand athlete should adapt his waves to training (pre-planed unloadings) to allow peaking for the given moment –competition!

15.december 2005.


Firts of all, it is quite hard to distinguish between conscious and subconscious part. Maybe there is no line at all, but I must say that I am proponent of Descartes dualism, so I strongly believe in „something“ that is not material (soul, spirit or call it whatever you want)! I dont belive that my behaviour and my existance is just biochemical process in brain cells or some complex algorhyth(s) as stated by strong AI proponents. In every motor control book, there is explanation of motor control from periphery to CNS, but I didnt find no one asking who or what triggers first neuron to fire? I dont belive it is somekind of random processes, I strongly believe in free will…. But we will leave this issue for some other time!

Conscious part is there to feel (perception) and to act or to set goals! When you move your hand, you dont voluntary activate your muscles, but you just set goals to a motor controler what to do and it creates movement based on his ability to control it optimaly (skill). Perception from outter world is filtrated trough your current emotions, attitudes etc, you never got it in pure shape (only if you are enlightemented 🙂 ) RPE (rate of percieved exertion) is also a perception of how hard is homoeostasis controler working to maintain your state in the boundaries of life. RPE is aso affected from your expectations, emotions, prior experience etc. Based on you mental strength (will power) you can push homoeostasis controler to work harder, while it tryes to „break“ your will with RPE feeling-perception!

What is the purpose of RPE (teleology) if the fatigue is just some physiological impairment? So, according to this model, fatigue is a protective control mechnism, which shut-down or alter your performance to keep the homoeostasis between boundaries. This do not exclude the posibility of peripheral fatigue, just it states that homoeostasis in never lost in exercising, and that movement is altered before it is too late. Some drugs (stimulans) can change this and can lead to homoeostasis lost and finaly to death!

When you try to execute some movement, you give a feed-forward information to homoeostasis controler so it can act much faster and not to wait deteoriation of the homoeostasis. To maintain homoeostasis, its controler activates heart, lungs, metabolic pathways, vascular system, detoxification system and finaly it alters movement execution via his connectons with motor controler.

Everytime something changes in the system (human body), in most case gain of the system or in other words function of cardiovascular, respiratory systems, muscle etc. , motor controler and homoeostasis controler must find a better way to control its behaviour. It is a process of finding the best/optimal control strategy based on some criteriums. Criteriums can be various: speed of motion, energy efficasy etc. So every time you improve your abilities you must improve your skill. Take an example. If you improve your arm strength without practicing free shots in the same time, you motor controler will use same control strategy but your muscle are producing more force so you will miss the shots. You must give a time for motor controler (and homoeostasis controler) to adapt, to find the best control strategy, so the best solution is to practice free shots while improving strength! For this same reason, interval training is better than continuous, because it forces homoeostais controler to find stabile state more that once as is the case with continuous running. When doing continuous runs, controler find the stabile state and keeps it while with interval training he must learn to find it more quicker and more than once and to learn to use muscle more efficiently (neuromuscular coordination). This is why a allways say that endurance is a skill!

17. december 2005. (Reply to Supertraining)

Let me preformulate my question Jamie. In vitro conditions (without nerve and blood supply), muscles produce greater force during eccentric than concentric contractions measured with isokinetics apparatus in physiological liquid and with artifical electrical stimulation. Mechansm for this larger forces (during eccentric contractions) are author-dependent: Jaric states that it is because viscosity in muscles (which resists movement speed, and in eccentric contraction is in same direction as aktin-miosin force,thus we get larger force), and Enoka (correct me if I am wrong) states it is because changes in actin-myosin cycle!

If there is a governor that limits maximum isometric force (strength deficit) in vivo (with nerve and blood supply – normal muscle) to protect tendons, joints and muscles itself, then why does he (governor) allows greater forces in eccentric contraction? Why doesnt he (governor) reduce muscle activation, so does muscle produce same maximum force in isometric conditions and in eccentric condition? And if the larger isometric force than allowed by governor, harms tendons, joints and muscles, why doesnt larger eccentric force create damage?

Or put another word:

  • Maximum maximorum isometric strength (via artifical stimulation) = 100N
  • Maximum isometric force MVC = 70N
  • MVC force during eccentric contraction (at some predef speed) = 90N (or more)

Is the maximum isometric MVC force is limited because of protection, then why MVC force during eccentric contraction IS NOT limited, and why doesn’t it produce any damage?

25. January 2006. (Altitude Training Vs. Below Sea Training)

When you perform, there is a tendency to perturb body homoeostasis. This perturbation strongly depend on your skill/abilities, or to say your muscle power, economy, elasticity etc.
Your body wants to maintain homoeostasis, so it react by activating (in greater degree) the mechanisms for their maintenance (heart, lungs, termo regulation, etc.). As stated before, movement is interplay between stability/mobility, and if we draw a parallel, performance is the interplay of perturbation/manintenance of homoeostasis (can you see the similarity with Yin/Yang concept and dualism?).

According to Homoeostasis Performance Model, to improve performance, one should improve:

  • Sport Specific Skills and Underlying Abilities (including morphotype)
  • Ability(es) to mainatin homoeostasis
  • Mental abilities

Your body never exit from homoeostasis limits, and if you tend to do it, your Central Governor reduces muscle output and increase RPE. So, improving skills/abilities tend to increase homoestasis deteoriation during performance (except improving economy, elasticity etc). There is an interesting concept in Lore of Running book from Tim Noakes (which I started reading before couple of days), that when you want to improve muscles abilities (in long distance running) you should engage in oxygen enriched enviroment, rather than altitude training!!!! On, my opinion this oxygen enriched enviroment allows you easyer maintenace of homooestasis, and thus greater stimulus for the muscles (you can achivere greater performance values). On the contrary, if you want to traing your homoeostasis maintenance abilitie(s), you should get into oxygen depleted (altitude) enviroment. But this kind of training will not optimally develop muscle factors. Thus, the solution is that distance runners should engage into below seas training (oxygen enriched enviroment) to stimulate muscle factors, and in altitude training to stumulate homoeostasis maintenance abilities…

25. January 2006. (Integrating Homoeostasis Performance Model with Conjugate Sequence System)

As stated in the Model update from 12. december 2005, if we expand concept of homoeostasis to joint integrity, bone health and structural integrity of the body, we will soon see, that to achieve peak performance one should not only train Sport Specific Abilities and Skills, but also, an ability to maintain homoeostasis, or body integrity. This means, that during sport specific training, one should allow some time for training of joint integrity and overall integrity, thus minimizing muscle imbalances etc. According to conjugate sequence system, one should train abilities in sequntial manner, but in the same time maintain non-specific abilities (and alredy developed specific ones), or in other word, one should maintain/improve their GPP (general physical preparedness) levels to allow improvement in SPP (special physical preparedness). For example, to achieve better performance in shot-put, one should train mostly for developing greater power in arm/legs, but in same time, one should also include minimal time training for non-dominant hand, back mucles etc. This is because development of greater power in arms tend to create greater stress at the arm joints, and if you don’t have also developed back muslces (rotator cuff, lats, traps etc) your joints tend to be pulled/clenched during performance, because you have not developed ability to maintain their integrity (homoeostasis).

15. June 2006.

The Human Performance Model (HPM) basically states that any kind of performance is limited by balance/harmony between two processes: homoeostasis break-down process (HBP)
and homoeostasis maintenance process (HMP). If HBP is more powerfull than HMP then the performance will eventually stop because of developed fatigue. So, fatigue is not
physiological impairment, but it is rather a control mechanism that prevents ruining of bodyhomoeostasis which can lead to injury and death. The body is smart… it is not just a machine listening to our motor commands…

In running, muscle action that creates GRF and actually propels you forward (and up) tend to perturb homoeostasis (joint stress, metabolites, stretch-shortening fatigue, tendon strains, usage of energy fuels – liver and muscle glycogen etc), and if your functional organs are unable to maintain homoeostasis there will be fatigue build-up and eventually decrease in running speed or stopping. Thus, running performance is limited by (a) ability of muscle system to produce power for running and (b) homoeostass maintenance ability (which depends on various factors).

If we expand concept of homoeostasis to joint integrity, we will soon see that HPM is applicable to resistance training. If your muscles are not in balance your main lifts will suffer.
Altought your body have ability to lift 150kg on bench press it will not allow you this performance if your shoulder stability is poor due weak rotator cuff muscles (for example). Trying to lift more will eventually lead to injury if you succeed to by-pass control mechanism. Thus, the strength is limited by (a) potential strength ability and (b) homoeostasis control (muscle balance, structural integrity, joint stability/mobility etc.)

Another comparation is the following. You have Ferrari that have very powerfull engine and can go 400km/h. But, his brakes are poor. The question is how much will you push the gass pedal? How much will you allow yourself to go fast? 400? I don’t think so… maybe 100km/h max. Thus, your security is more important than the powerfull engine. To go faster you must first fix your brakes. Considering this for some athlete, he should (a)improve engine power and/or (b)improve braking system.

Another example is puch in boxing. You would love to speed up the puch and thus improve your ability to knock-out opponent and pass his defense. So, you start improving explosive strength of prime movers (triceps, deltoideus, pecs etc), but after some time you start to stagnate… You try to develop even more explosive strength in prime movers but with no succes. The solution is to improve antagonist muscles that actually decelerate the moving limb. Your body will allow only the speeds of movement that will not cause injury to joints.

Event if you have potential to move limb faster, you will be not allowed to do so until you „fix the brakes“.

17. June 2006.

Basically, the body* has two main goals/tasks

  • Create the actions directed by the Owner** which basicaly tend to perturb body homoeostasis
  • Provide the frame for life of the Owner by trying to maintain its own homoeostasis within boundaries of life

Thus, the body is allways deciding between these two processes. The body is smart. It will allow actions but only within the boundaries of maintenance of homoeostasis. Training improves both processess. It improves actions (homoeostasis perturbation) by improving abilities and skills. It also improves the ability of the body to maintain homoeostasis by improving the functional systems and their control and also skills (more skillfull athletes are more efficient and thus create less perturbation in homoeostasis). Training should provide BALANCE between these two processess, becasue if emphasising only one there will not be any improvements and it can actually lead to decrease in performance. Both processes should be improved to improve performace. Note that those two processes are not split-able, they are integrated into a whole! Also, the body must provide a feedback from Material World to the Owner. This is called perception and is also affected by current states, emotions etc and is also affected by training. Everything is affected by everything.

If you (Owner) force the body to provide actions, it will give you feedback about the work done to maintain homoeostasis – RPE (rate of percieved effort; which is a „combination“ of action effort and homoeostasis maintenance effort). This is one of the mechanisms of the body to tell you where are you heading (perception, and as such it is affected by your expectations, prior experience, emotions etc). If your Will Power is very strong and keep pushing it, the body will ultimately use the second protective mechanism – fatigue. The body will try to alter the activity by „fatiguing“ itself (reducing CNS output and impairing physiological processes at the periphery), so you must push it harder (which will induce greater RPE) which ultimatelly lead to greater fatigue until fatigue is greater than your Will Power and this is when fatigue starts to become visible by altering/reducing performance. Note that fatigue starts at the onset of exercise/action as a control mechanism.

This was my short teleological (purpose) aspect of fatigue and RPE. I hope I didn’t confuse anyone, but I doubt 🙂

* Under the term body I consider the body-mind complex
** Under the term Owner I consider the Consciousness, Soul or whatewer you like to call it. I am strong proponent of Descartes Dualism and I strongly believe in Free Will.
Also, I don’t belive that Consciousness is located in the brain, it is something that is not material and cannot be explained by phisical laws and algorhythms. The brain/mind is just a „transducer“ or a machine. I did’t wanted to go into philosophical discussion but it seems that we cannot do anything without considering it.

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