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The importance of motor learning in the development of the concept of stabilityby Martin Krause, Dec 2006 B.Appl.Sc (Physio), M.Appl.Sc (Manip.Physio), Grad.Dip.Hlth.Sc(Ex&Sp), Grad.Cert.Hlth.Sc.Edu, Cert IV Workplace Assessment & Training.
During my last undergraduate semester at University in 1986 I had an assignment titled "Why don't our shoulders subluxate". At the time the scope of thought was that the supraspinatus was entirely responsible for that stability. Whilst surfing on Cronulla beach I reflected on my problem since I was required to write a 5000 word essay as well as present a 40 minute paper on the topic! It certainly became clear to me that the previous simplistic dogma wasn't going to be enough to solve the problem. Luckily, we had some inspirational lecturers at the time in the form of Janet Carr and Roberta Shephard. They steerd me in the direction of the Russian mathematician Nikolai Bernstein and his seminal work of the 1930's on the motor control problem over the degrees of freedom around the shoulder. Since that time the Australian Schools of Physiotherapy have considered stability across body parts and addressed the issues of motor control and pain from several different perspectives. These have included 1. The absolute stability of isometric contractions Generally speaking, this type of stability training is only useful for regions with little movement. An example is the activation of the transverse abdominis and internal oblique muscles in sitting.
Interestingly, the use of muscle energy techniques employs isometric contractions and mobilisation of pelvic and spinal segments for the optimisation of muscle control and symmetry across the pelvis. 2. The dynamic stability of rotating systems which use mathematical geometric reference points
These geometric reference points were emphasized by Saha (1983) in calculations of pure rotation control. However, it was Turvey et al (1978) who proposed that it was the synergistic recruitment of the scapula and glenohumeral muscles which required a controlling mechanism. Turvey et al (1982) who emphasized the recognition of contextual settings as the most important aspect of motor control. 3. the dynamic stability of oscillating systems Turvey et al (1982) suggested that the problem of motor control could be solved by considering the system moving in periodicies which were constrained around a fixed point by the resistance encountered with movement. This hypothesis moved away from peripheral proprioception feeding information back to the brain. Instead we were examining the problem in the context of 'feedforward' systems where proprioceptive feedback' was only required if our objectives weren't met.
Although the original hypothesis pertained to the region of the shoulder, analysis of muscle activity in the abdominal region during arm movements in the mid 1990's by Richardson et al led to some interesting feedforward conclusions involving the transverse abdominus and multifidus muscles. 4. The uncontrolled manifold hypothesis for periodicies Yet how does learning of feedforward mechanisms occur. It was suggested that releasing and reorganizing degrees of freedom are processes that accompany practice (Schmidt & Lee 1999). Recently an “uncontrolled manifold hypothesis” was proposed which assumes that when a controller of a multi-element system wants to stabilize a particular value of a performance variable, it selects a particular subspace where the desired variable is held constant. Simultaneously, other elements can show a high degree of variability so long as they do not affect the essential variable (Latash et al 2002). Similarly, closed loop theory suggests that a learner acquires a reference of correctness (Schmidt & Lee 1999).
5. The stability of inverse dynamics With the introduction of force and momentum into the motor control stabilisation argument, the natural thing to consider is the effect of Newtons 3rd Law of Action - Reaction. When applied to accelerating body parts which have mass and hence momentum, then the balancing and counterbalancing forces can be calculated and their perturbations can be used to optimise movement. The great thing with this development is that it allows us to consider the parallel and series elastic components as springs providing recoil energy, whilst muscles provide eccentric-concentric energy capturing efficiency by opitmising the trajectories of moving body parts. Combining these concepts of elastic potential and kinetic energy with inverse dynamics gives some resolution to the problem of control of the 'inverted pendulum' which is walking. Similar to rockets or sedgeway systems the propulsive force acts up from the ground resulting in a potentially unstable mechanism. Body pertubations such as swing and pendular movements of the arms help counter these potentially destabilizing forces. Aditionally sinusoidal oscillations in the soft tissue acting at a microscopic molecular level up to the level of cytoskeletal and musculoskeletal architecture probably impact on stability through the dynamic alterations and adjustments afforded by the principles of tensegrity; whereby actin like moelcules are able to change the cellular architecture to adapt to forces developed by vibration and fluid shear.
Plyometric exercise regimes employ concepts of inverse dynamics for the optimisation of movement efficiency. More recently, these type of exercises have also been emphasized for recovery from tendonosis as it benefits both the parallel and series elastic components, as well as blood flow and more importantly the capture of transverse force energy for longitudinal muscle displacement. During the early 1980's Bergmark described muscles based on their biomechanical characteristics dividing them into two fundamental elements - local stabilisers and global mobilisers. A decade later in the early 1990's, a fundamental development in the concept of stability was from Punjabi where he described elements of control which included the passive elements (ligaments, capsule, etc), the active elements (muscle) and the 'active controller' as an integrated system of satbility. A pain element was later added by Lund et al (1991) whereby they described the inhibition of the agonists and facilitation of the antagonists in a peripheral area of pain.However, in the trunk a different interplay of muscles was construed, whereby Hodges et al (1995) and Hides et al (1994) later suggested that this peripheral motor pattern may be represented by inhibition of the multifidus and transverse abdominis muscle in the trunk. Furthermore, Wim Dankaerts and Peter O'Sullivan (2005) further suggested that facilitation of the gobal mobilisers into stabilisers resulted in motion and/or movement impairment with excessive compression of the spinal vertebrae and their comprising elements leading to reduced postural pertubations and reduced degrees of freedom.
6. Vestibular and verbalisation for stability In the 1970's, Hon.Dr Med Suzanne Klein Vogelbach took a vestibular approach to agonist - antagonist recruitment and hence 'timing' of synergy. In cats, lack of vestubular input has been shown to reduce extensor muscle tone (Magnus 1926 in Belavy et al 2007, J Appl Physiol, 103, 48-54).
Klein Vogelbach also placed a large importance on complex language constructs when assessing and administering exercise for movement dysfunction. Apart from an existential philosophical construct of reality, the manipulation of language seems to underlie concepts of verbalisation for accessing the subconscious in the development of expertise, and is also used in neurolinguistic programming as well as congitive functional therapy. 7. Mental stability such as sporting performance in orienteering With the evolution of each new concept the emphasis is still placed on higher centre motor control. However, since the brain can only process one piece of information at any one instance, and can only hold 6 pieces on information in short term memory how can this control movement? Indeed for control to occur it must be processed subconsciously, thereby freeing the conscious brain for decision making when the automated processes sense inconsistencies. The most powerful access to our subconscious brain is through our ability to verbilise and visualisel our expectations. Hence, in orienteering, the athlete can read the map to analyse the upcoming terraine thereby preparing their motor system for what will be encountered. Such preparation lends itself to pacing strategies and goal oriented feedback whereby anticipated feedback act like red and green traffic lights. Self affirmation requires little conscious effort e.g. is this the correct track and there is the rock followed by a spur and a clearing with a small gully to my right. If these features don't fit the terraine being scanned by the visual cortext then the greater mental effort of conscious correction and decision making needs to be employed.
link to motor learning in orienteering Acquisition of motor control requires context specific variability. Variability is particularly important in orienteering as each course is unique and different. Without variability, injury and/or sub-optimal performance is likely to occur. 8 Neuro-linguistic feedback stability From Switzerland, the Hon Dr Med Prof Klein Vogelbach (Functional Learning Theory {FBL = Funktionelle Bewegungs Lernen}) used powerful linguistic analysis of visual and tactile inputs to force physiotherapists to communicate their thinking with their clients. Hereby, a 2 way discussion ensued which could be argued lead to a stabilizing relationship between the therapist and their client and with the client and their own condition. This narrative reasoning has been propagated by Mark Jones in Adelaide. More-over the semantics of language and the power of words have been used to ascertain peoples fears and beliefs as they pertain to movement. In fact, Peter O'Sullivan has encouraged therapists not to use the term 'instability' as it may elicit fear-avoidance movement behaviour in people.
Peter O'Sullivan LBP movement classification disorder
9. Stability through occulomotor reflexes This form of stability has gained a lot attention through the work on Whiplash injuries by Michelle Stirling and Gwen Jull at the University of Queensland. They advocate the use of powerful visual reflexes to optimise both static stability as well as tracking stability. Additionally, they use pointer devices beamed from peoples heads onto a target on a wall to test and train peoples correctional ability after the eyes are shut, or when the body is turned whilst trying to keep the head stable. This is in line with their revolutionary regime of training deep neck flexors, improving scapula control, reducing muscle spasms and over-activity to improve functional stability.
10. Metabolic and Immune stability
Although muscle mass is considered fundamental for the production of force and hence power, I submitted a paper for publication in 2003 (not accepted) which outlined the importance of muscle mass to hormonal and metabolic function. The concept of total body stability and allostasis was presented in Rome in October 2005.
Since the central nervous system and resting muscle tone are particularly important aspects of motor control, then emotional stability is of paramount importance for optimal performance. Extreme examples of mal-adpative behaviour to emotionally labile states are situations which lead to 'fear - avoidance' of activity. Optimisation of the emotional state can lead to the feeling of control over the environment rather than the reverse, "master of their own destiny". Such scenarios also result in large amounts of energy being available which if constrained through 'pacing' can result in athletic success but if unchecked can cause euphoria which ultimately leads to a "crash and burn" phenomenon.
It could be argued that the term 'instability' could lead to 'fear avoidance' behaviour with inappropriate sympathetic nervous system activity. Hence, the concept of allostasis and neuro-immune behavioural mechanisms need to be considered here.
Rumination can be ascertained on questioning the client about the intial precipitating incident. Additionally peoples attitude towards them, in the working/sporting, home and social environment may have an impact on the persons 'emotional stability' as well as their ability to cope actively. Clearly, the gaining of sporting expertise (such as pitching in baseball) can only be obtained through repitition of movement (practice), whilst avoiding injury. Furthermore, when injuries do take place appropriate recovery from injury should occur. Generally, people consider recovery to be synonymous with being painfree. However, over the years we have learned that motor dysfunction can continue in the absence of pain, thus leaving a person vulnerable to further injury.
Clinically, the Maitland edition of Peripheral Manipulation from the early 1990's emphasized the concepts of stage, severity,irritability and stability. Unfortunately, these concepts were thought only to apply to joints, which at the time was considered a 'passive structure' (e.g. passive accessory and passive physiological). Yet the concept of 'stability' suggested a clinical past history of questioning the frequency of recurrences. 'Irritability' was emphasized and considered the ease of exacerbation of pain and the time required for it to subside, yet it was meaningless if considered outside the concept of stability. The 'stage' of the problem explained whether a condition was getting better/worse or staying the same, but was only meaningful if the 'severity' of the condition was considered. By examining 'severity' the authors were actually considering today what we would describe as 'avoidance behaviour'. Hence, it was important to know what the person was and wasn't doing. They may appear stable and non - irritable but what had been eliminated out of their activities of daily living? Addressing 'easing factors' can give an indication of whether the person copes 'actively' or 'passively'. Such cognitive evaluation by the client's higher centres is now considered an integral part of the examination and treatment process when determining the motor control issues affecting their musculoskeletal system.
Even despite the knowledge that pain could cause reflexogenic inhibition and excitation of muscle activity, pain was clearly a missing ingredient in many models of motor learning. By 1993, at the Parisian IASP world congress, French researchers had mapped descending noradrenergic modulating pain pathways in rats (Proudfit, H.K. (1992). The behavioural pharmacology of the noradrenergic descending system. In : Besson, J.M. & Guilbaud, G. (Eds.)(1992). Towards the use of Noradrenergic Agonists for the Treatment of Pain (1st ed.). Amsterdam : Elsevier Science Publishers B.V.), whilst the first MRI and PET imaging started to become available and affordable to general patient populations (IASP world congress, Vancouver 1996).
Although the concepts of motor learning, skill acquisition and stability have seemed like a parallel phenomenon to the traditional approach to physiotherapy, this shouldn't be taken for granted. The Swiss physiotherapist and founder of Functional Movement Learning, Honorary Doctor Medicine Klein Vogelbach, used concepts out of neurology, in the 1970's, such as training with Swiss balls and brought them across to musculoskeletal physiotherapy. Other watersheds included, the McConnell technique of 'patella taping' which was actually developed at Sydney University in the mid 1980's and had a strong stabilising motor control emphasis drawing on the works of the Americans Gentile and Sahrmann. By the mid 1990's Hodges, Richardson, Jull et al at the University of Queensland placed emphasis on the stability from the transverse abdominal and multifidus muscles in treating low back pain. Interestingly, Klein Vogelbach had already incorporated small spinal rotational movement training into her Functional Movement Learning (FBL) regime at least a decade previously. By the late 1990's, Lorrimer Mosely was using techniques out of rehabilitation in Neurology, such as reverse mirrors, to take a revolutionary perspective on motor control and neuropathic pain. Similarly, Peter O'Sullivan from Western Australia drew on work in Neurology and Psychology (CBT) to determine and validate a new classification for the treatment of chronic low back pain which has been termed Cognitivel Movement Therapy.
Inconsistent findings on the effects of pain on motor control has made it important to conceptualize a theoretical framework of adaptation in the sensorimotor system in the person with pain. A simplistic approach would be to say that the person will use the redundancy in the system to protect the perceived vulnerability to further injury. Such redundancy takes the form of employing synergistic muscles to perform the task and/or adapting the task to reduce loading. In the acute phase of an injury, such simple strategies may be useful, however adapatation can be very rapid and permanant. If the adaptation is suboptimal for the intended goal, then secondary injuries may occur. These may take the form of disuse atrophy, reduced sensorimotor (proprioceptive and feedforward) input from the 'unloaded' part, whilst overloading the compensatory muscles and the body parts which they influence. Therefore, both the primary and secondary consequences of the movement dysfunction must be evaluated and treated. Henry Tsao at the University of Queensland has quite clearly shown alterations in cortical processing regions (motor maps) in the brain in people with chronic low back pain. Adaptation strategies vary between people with both increases and decreases in muscle activity occuring in various parts of the body. Thus it becomes imperative that the person is examined in a systematic way in order to specifically taylor treatment management strategies.
Levin et al (2008)
mapped the gene expression of pain which in the case of muscle tissue
proteins and neural tissue probably has an influence on motor control.
In the 2 decades since surfing in Cronulla, the approach to musculoskeletal disorders and the concept and scientific verification of stability has undergone significant and fundamental changes due to the dedicated work of physiotherapist researchers validating clinicians insights and practice. Unlike 1986, by 2009 a 5000 word paper and a 40 minute presentation on the topic of 'Why our shoulders don't subluxate' would be pretty easy to fill.
Clinically, the examination process must ascertain the affect of pain and injury on attention and stress and its affects on the interpretation of task demands and hence motor planning. The effects of cortical inhibition, delayed central transmission, reflexogenic motoneuron inhibition on motor planning can lead to an altered internal model of body dynamics. Clinically this may manifest as reduced range of motion, altered reflexes and muscle strength, as well as changed movement goals to protect the body part. The clients perception of their problem is a vital part of a 'top down' approach to assessment and treatment. A 'bottom up' approach views the adaptive mechanisms in terms of altered proprioceptive input resulting in inaccurate motor planning. For this reason combination therapy, using passive modalities such as joint mobilizations, taping, dry needling, soft tissue massage, etc must be accompanied by meaningful and well integrated exercise prescription which takes into account the values and beliefs of the client. Moreover, in some cases a real and/or virtual exercise regimes may mean that passive modalities are either unwarranted or contraindicated. Cognitive Behavioural Therapy may be required to address the aspects of 'attention' and 'stress'. Regardless, of the approach taken, the goal should be to educate the client on their condition and how treatment interventions can meet their expectations. "It is the thoughts which preceed the action which count considered thoughts, considered action decisive thoughts, decisive action constructed thoughts, constructed action"
also see : chronic low back pain (central) neurophysiology of pain (peripheral) |
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