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THE CLINICAL CLARITY BLOG
Input or output?
FEBRUARY 28, 2017 by DR MATTHEW D. LONG
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THE CLINICAL CLARITY BLOG
Input or output?
FEBRUARY 28, 2017 by DR MATTHEW D. LONG
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THE CLINICAL CLARITY BLOG
FEBRUARY 28, 2017 by DR MATTHEW D. LONG
The ideas underpinning chiropractic care, and the mechanisms behind spinal manipulation, have evolved greatly over the years. Theories of manipulation have traditionally emphasised mechanical realignment of the vertebrae, usually to reduce irritation to the spinal nerves. Historically there has been an emphasis on reducing interference to motor output (including the autonomic system), often characterised as 'taking the foot off the hose'. But is this what really happens? Does an adjustment truly work by improving motor output? Or is something else going on?
Obviously an adjustment is not a singular thing that can be easily quantified. Furthermore, it seems to have differing effects in different individuals. In other words, some people respond better than others (you can read more about this in another Clinical Clarity Blog article here). It also appears that the neurological effects that accompany manipulation are not limited to simple segmental reflexes, but reverberate throughout the neuraxis, all the way to the cortex. So asking the question, "What does an adjustment do?", is a bit like asking "What does exercise do?" Well, this very much depends upon who is doing the exercising, the type of exercise, the intensity of the exercise and the dosage used.
Fortunately, we don't have to overthink this too much. If we simply start using the body in the way it was intended then it can largely work out for itself what it needs to derive from exercise. Indeed, the scientific literature has a renewed interest in the role of functional movements in exercise, and a move away from the notion that specifically targeting individual muscles leads to better outcomes. It has also documented the central role of the brain itself in an exercise-driven approach to spinal rehabilitation. The idea that a patient with spinal problems is simply lacking enough 'core strength' to hold themselves together is highly simplistic, and not supported by the evidence. Rather, the 'weakness' often lies in the control systems that regulate the core muscles (amongst others) and choreograph their every move. Precision control of any muscle group requires practice and experimentation, so as to provide enough data for the brain to develop the appropriate motor program. Furthermore, this training process is not limited to highly complex skills (such as playing a musical instrument). It also underpins every movement that we make, whether they appear trivial or not (such as arising from a chair).
So where does the brain get its data from?
The short answer is, 'from everyday life'. Unfortunately many (most?) of us are severely lacking in a well-balanced 'diet' of functional movements. Our lives are increasingly regimented into a shrinking repertoire of daily movements that have robbed our brain of the diversity it craves. Sitting dominates the workplace, and exercise becomes a semi-regular afterthought. Even then, many of us perform a stereotypical set of exercises that, once learned, no longer drive further motor learning. Thus, the brain becomes adept at a small range of movement patterns, but gets caught out when the individual does something novel (such as cleaning out their garage on the weekend).
Obviously an adjustment is not a singular thing that can be easily quantified. Furthermore, it seems to have differing effects in different individuals. In other words, some people respond better than others (you can read more about this in another Clinical Clarity Blog article here). It also appears that the neurological effects that accompany manipulation are not limited to simple segmental reflexes, but reverberate throughout the neuraxis, all the way to the cortex. So asking the question, "What does an adjustment do?", is a bit like asking "What does exercise do?" Well, this very much depends upon who is doing the exercising, the type of exercise, the intensity of the exercise and the dosage used.
Fortunately, we don't have to overthink this too much. If we simply start using the body in the way it was intended then it can largely work out for itself what it needs to derive from exercise. Indeed, the scientific literature has a renewed interest in the role of functional movements in exercise, and a move away from the notion that specifically targeting individual muscles leads to better outcomes. It has also documented the central role of the brain itself in an exercise-driven approach to spinal rehabilitation. The idea that a patient with spinal problems is simply lacking enough 'core strength' to hold themselves together is highly simplistic, and not supported by the evidence. Rather, the 'weakness' often lies in the control systems that regulate the core muscles (amongst others) and choreograph their every move. Precision control of any muscle group requires practice and experimentation, so as to provide enough data for the brain to develop the appropriate motor program. Furthermore, this training process is not limited to highly complex skills (such as playing a musical instrument). It also underpins every movement that we make, whether they appear trivial or not (such as arising from a chair).
So where does the brain get its data from?
The short answer is, 'from everyday life'. Unfortunately many (most?) of us are severely lacking in a well-balanced 'diet' of functional movements. Our lives are increasingly regimented into a shrinking repertoire of daily movements that have robbed our brain of the diversity it craves. Sitting dominates the workplace, and exercise becomes a semi-regular afterthought. Even then, many of us perform a stereotypical set of exercises that, once learned, no longer drive further motor learning. Thus, the brain becomes adept at a small range of movement patterns, but gets caught out when the individual does something novel (such as cleaning out their garage on the weekend).
"Our lives are increasingly regimented into a shrinking repertoire of daily movements that have robbed our brain of the diversity it craves."
We could encapsulate this idea by suggesting that a modern sedentary lifestyle does not provide enough proprioceptive 'nourishment' to sustain a healthy brain and nervous system. The effects of this may be a distortion of the body schema, a cortically-maintained map that is essential to postural control and efficient body movements. You could think of it as a 3-dimensional representation of all of our body parts and it has been defined by Gallagher (1) as, "a system of sensory-motor capacities that function without awareness or the necessity of perceptional monitoring."
Laessoe et al (2) stated that,
Laessoe et al (2) stated that,
"The body schema may be disturbed in some individuals due to immobilization, a traumatic incident in the central or peripheral neurological system or due to psychological factors."
The work of Lorimer Moseley has been hugely influential in promoting this understanding of somatosensory disturbance (3), even going so far as to suggest that patients with chronic back pain have a form of 'neglect' (4). So the question arises, if our patients do exhibit a disruption in the spatial representation of their body, what can we do about it?
Obviously the foundation of any management plan must involve movement and exercise. Our daily routines need to be rethought, and lengthy periods of sitting addressed. We should emphasise an exercise regime that is variable and functional, not one based simply upon the repetition of a limited set of movements. If we can give the brain enough variation in its inputs, then it can start to develop a vast range of practised outputs. As the saying goes, "Garbage in, garbage out."
But how else might we assist the brain? How else might provide a better quality of input?
This is where the signature chiropractic adjustment may well shine. An adjustment could be described as a highly-leveraged dose of proprioception. One that is composed of a novel blend of sensory inputs, delivered precisely to one of the main sense organs of the human balance system - the spine. While you may not think of the spine as a 'balance organ', it is precisely that. It functions as the central strut of the human body, and is imbued with an incredible sense of proprioceptive awareness. This sensitivity is largely dependent upon muscle spindles embedded in the deep spinal musculature, and they function to transduce mechanical stretch energy into action potentials. This information is encoded and delivered to our brain in a way that allows us to orientate ourselves (in conjunction with inputs from the vestibular and visual systems). However, our nervous system relies upon repeat inputs to drive learning and plasticity. As such, if we do not habitually explore all of the possible ranges of motion of our joint structures, we will see a decline in the efficiency and accuracy of the circuitry responsible for monitoring and controlling these movement planes. This neurological atrophy occurs at all levels of the input chain, from receptor all the way to the cortex. Furthermore, our range of possible outputs will also decrease as the nuanced movements are lost. Again, "Garbage in, garbage out."
According to Lelic et al (5),
Obviously the foundation of any management plan must involve movement and exercise. Our daily routines need to be rethought, and lengthy periods of sitting addressed. We should emphasise an exercise regime that is variable and functional, not one based simply upon the repetition of a limited set of movements. If we can give the brain enough variation in its inputs, then it can start to develop a vast range of practised outputs. As the saying goes, "Garbage in, garbage out."
But how else might we assist the brain? How else might provide a better quality of input?
This is where the signature chiropractic adjustment may well shine. An adjustment could be described as a highly-leveraged dose of proprioception. One that is composed of a novel blend of sensory inputs, delivered precisely to one of the main sense organs of the human balance system - the spine. While you may not think of the spine as a 'balance organ', it is precisely that. It functions as the central strut of the human body, and is imbued with an incredible sense of proprioceptive awareness. This sensitivity is largely dependent upon muscle spindles embedded in the deep spinal musculature, and they function to transduce mechanical stretch energy into action potentials. This information is encoded and delivered to our brain in a way that allows us to orientate ourselves (in conjunction with inputs from the vestibular and visual systems). However, our nervous system relies upon repeat inputs to drive learning and plasticity. As such, if we do not habitually explore all of the possible ranges of motion of our joint structures, we will see a decline in the efficiency and accuracy of the circuitry responsible for monitoring and controlling these movement planes. This neurological atrophy occurs at all levels of the input chain, from receptor all the way to the cortex. Furthermore, our range of possible outputs will also decrease as the nuanced movements are lost. Again, "Garbage in, garbage out."
According to Lelic et al (5),
"To accomplish the coordinated operations of multiple neural systems and structures, the prefrontal cortex must monitor the activities in other cortical and subcortical structures and control and integrate their operations by sending command signals in a so-called “top-down” manner. This is a complex operation, and the importance of this monitoring, integration, and coordination is highlighted in studies where damage to the prefrontal cortex has been shown to impair the ability to create new and adaptive action programs or choose the best among several equally probable alternatives, despite such individuals displaying normal IQs in most psychological tests, having normal long-term memory functions, and exhibiting normal perceptual, motor, and language skills. The change in prefrontal cortex as seen in this study therefore suggests that the altered input from dysfunctional joints that leads to altered processing of somatosensory inputs can influence processing of somatosensory information by the prefrontal cortex. Chiropractic care, by treating the joint dysfunction, appears to change processing by the prefrontal cortex. This suggests that chiropractic care may as well have benefits that exceed simply reducing pain or improving muscle function and may explain some claims regarding this made by chiropractors."
We should also be mindful that spinal manipulation will engage the nervous system in a myriad of ways - not just by provoking analgesia, or triggering muscle and balance responses. After all, our brain is always using as much input data as it can possibly get, so that it can tailor our physiology to the changing environment. This is the basis of homoeostasis.
Spinal inputs assist our nervous system in creating a perfectly matched autonomic output. However, we should always be mindful that this process is highly integrated and not something that we can specifically modulate. While we can argue that spinal manipulation may theoretically alter an individual's blood pressure, we cannot predict who will respond in this manner, or how long this response might last. The same goes for pain. Some patients respond disproportionately well to manipulation, whereas others seem indifferent.
To return to the concept of 'responders', it does appear that we all carry our own neurological tendencies and preferences for input. For some, acupuncture seems to trigger the best response. For others, manipulation is the ideal catalyst for neurological change. And implicit in all of this is the fundamental need for everyday diversity of movement. The one thing that each of these approaches have in common, is that they function as inputs to the nervous system.
Of course, manipulation is not the only vehicle for improving proprioception. Röijezon et al (6) put it this way,
Spinal inputs assist our nervous system in creating a perfectly matched autonomic output. However, we should always be mindful that this process is highly integrated and not something that we can specifically modulate. While we can argue that spinal manipulation may theoretically alter an individual's blood pressure, we cannot predict who will respond in this manner, or how long this response might last. The same goes for pain. Some patients respond disproportionately well to manipulation, whereas others seem indifferent.
To return to the concept of 'responders', it does appear that we all carry our own neurological tendencies and preferences for input. For some, acupuncture seems to trigger the best response. For others, manipulation is the ideal catalyst for neurological change. And implicit in all of this is the fundamental need for everyday diversity of movement. The one thing that each of these approaches have in common, is that they function as inputs to the nervous system.
Of course, manipulation is not the only vehicle for improving proprioception. Röijezon et al (6) put it this way,
"Augmentation of somatosensory information via passive techniques such as manual therapy, soft tissue techniques and taping or braces can be valuable as they stimulate the mechanoreceptors in joints, soft tissues and skin to send a barrage of sensory information to the CNS, and in the case of manual therapy it has been suggested to involve plastic changes in sensory integration within the CNS. Specifically, exercise is an important element in augmenting proprioception. The muscle spindles are considered the most potent proprioceptors and are always stimulated during active movements as a consequence of alpha-gamma activation. The GTOs are also potent and sensitive mechanoreceptor to forces generated by active movements. Thus any active exercise can be considered ‘proprioceptive training’. Consequently there is abundance of research looking at various exercise methods to improve proprioception."
I think it bears repeating that spinal manipulation should be not viewed as a method of removing interference to brain outputs. Rather, it is a way to enhance inputs to the nervous system, thereby allowing a greater expression of appropriate outputs. And while human beings are continuously soaking up all manner of sensory information from the environment (sight, sound, taste, touch, smell, temperature etc), it is proprioceptive data that speaks the loudest. Our survival relies upon fast and accurate proprioception, so that we can immediately respond to postural change and prevent a potentially injurious fall. This is why our proprioceptive pathways are so large and heavily myelinated. It is also why a manipulative force can be so useful in enhancing sensory reporting and, quite possibly, might prove to be an effective aid in recalibrating our working body schema.
Something to think about...
Dr Matthew D. Long
BSc (Syd), M.Chiro (Macq)
Dr Matthew D. Long
BSc (Syd), M.Chiro (Macq)
References:
1. Gallagher, S., 2005. How the Body Shapes the Mind. Oxford University Press, New York.
2. Laessoe, U., Barth, L., Skeie, S., & McGirr, K. (2016). Manipulation of the body schema – Unilateral manual stimulation of lower extremity influences weight distribution in standing position. Journal of Bodywork and Movement Therapies, 1–6. http://doi.org/10.1016/j.jbmt.2016.09.013
3. Moseley, G. L. (2011). Disrupted working body schema of the trunk in people with back pain. British Journal of Sports Medicine, 45(3), 168–173. http://doi.org/10.1136/bjsm.2009.061978
4. Moseley, G. L., Gallagher, L., & Gallace, A. (2012). Neglect-like tactile dysfunction in chronic back pain. Neurology, 79(4), 327–332. http://doi.org/10.1212/WNL.0b013e318260cba2
5. Lelic, D., Niazi, I. K., Holt, K., Jochumsen, M., Dremstrup, K., Yielder, P., et al. (2016). Manipulation of Dysfunctional Spinal Joints Affects Sensorimotor Integration in the Prefrontal Cortex: A Brain Source Localization Study. Neural Plasticity, 2016, 3704964. http://doi.org/10.1155/2016/3704964
6. Röijezon, U., Clark, N. C., & Treleaven, J. (2015). Proprioception in musculoskeletal rehabilitation. Part 1: Basic science and principles of assessment and clinical interventions. Man Ther, 20(3), 368–377. http://doi.org/10.1016/j.math.2015.01.008
1. Gallagher, S., 2005. How the Body Shapes the Mind. Oxford University Press, New York.
2. Laessoe, U., Barth, L., Skeie, S., & McGirr, K. (2016). Manipulation of the body schema – Unilateral manual stimulation of lower extremity influences weight distribution in standing position. Journal of Bodywork and Movement Therapies, 1–6. http://doi.org/10.1016/j.jbmt.2016.09.013
3. Moseley, G. L. (2011). Disrupted working body schema of the trunk in people with back pain. British Journal of Sports Medicine, 45(3), 168–173. http://doi.org/10.1136/bjsm.2009.061978
4. Moseley, G. L., Gallagher, L., & Gallace, A. (2012). Neglect-like tactile dysfunction in chronic back pain. Neurology, 79(4), 327–332. http://doi.org/10.1212/WNL.0b013e318260cba2
5. Lelic, D., Niazi, I. K., Holt, K., Jochumsen, M., Dremstrup, K., Yielder, P., et al. (2016). Manipulation of Dysfunctional Spinal Joints Affects Sensorimotor Integration in the Prefrontal Cortex: A Brain Source Localization Study. Neural Plasticity, 2016, 3704964. http://doi.org/10.1155/2016/3704964
6. Röijezon, U., Clark, N. C., & Treleaven, J. (2015). Proprioception in musculoskeletal rehabilitation. Part 1: Basic science and principles of assessment and clinical interventions. Man Ther, 20(3), 368–377. http://doi.org/10.1016/j.math.2015.01.008