(Originally published on aaomptssig.wordpress.com)
The topic of movement and its relationship with pain is one that I find intriguing. I recently presented on this topic at my current clinic and thought it was a topic that deserved to be shared with a broader audience. This is not exhaustive by any means but does touch on a number of interesting topics. If you enjoy the topic please share and as always discussion is welcomed!
Isaac Asimov introduced the concept of being “Less Wrong” in his excellent reply to a critic’s attack on Asimov’s statements regarding what is currently understood. The progressive history of knowledge is summed up very nicely in the closing statement where Asimov says “Naturally, the theories we now have might be considered wrong in the simplistic sense… but in a much truer and subtler sense, they need only be considered incomplete.”1
This is precisely where we currently are in our understanding of pain. In the last decade neuroscience has absolutely exploded. In a historical sense the current understanding of pain can be safely deemed as less wrong than the model Descartes proposed in 1644, or Melzack and Wall’s gate control theory from 1965, and even the original neuromatrix model as proposed by Melzack in 1989. Models grow out of a need caused by new information. The neuromatrix was developed because it had been impossible for researchers to find specific spatially segregated cortical regions devoted to the perception of pain.2 However in its initial state it was significantly different from what the current pain matrix theory has become. It can be assumed that our current theory of pain isn’t necessarily correct and in the future it will be modified to reflect new knowledge. But it is significantly less wrong than it was.
In the last decade there has been significant and progressive refinements made to the pain matrix theory. A very serviceable definition of pain was given by Lorimer Mosley in defining pain as “…a conscious correlate of the implicit perception that tissue is in danger.”3 This definition is excellent and very succinct in its ability to get across most of the important information without feeding into many of the common myths. However there is room to improve and expand the concept. The recent surge in interest around the ideas of complexity and emergence has led to a further refinement in the idea of pain to where it is defined as an emergent property of the brain. In 1972 Philip Anderson published the article “More is Different” and forced the scientific community to grapple with the fact that the individual components did not always explain the resulting phenomena. In Anderson’s words “The ability to reduce everything to simple fundamental laws does not imply the ability to start from those laws and reconstruct the universe… At each level of complexity entirely new properties appear. Psychology is not applied biology, nor is biology applied chemistry. We can now see that the whole becomes not merely more, but very different from the sum of its parts.”4
In the discussion of emergence there exist two main criteria that must be considered: the same system can produce a range of emergent properties and the emergent properties are unable to be produced by any of the individual aspects of the system.5 Stated slightly differently “an emergent property is one that exists only at the level of the system, and not at the level of the parts that make up the system… if you can’t break [a system] down into its parts without destroying key features of its behavior, then you’re dealing with a complex system.”6 Because of this, defining pain as an emergent property of the brain is an incomplete and possibly faulty idea. This statement is an example of a mereological fallacy: defined by philosophy as “the misattribution of a property of the whole being to a single part of that being.”5 In order to avoid missing the fact that it is the person who experiences pain, Mosley and Thacker state that “a more accurate position is that pain is an emergent property of the person who is suffering it.”5
Without understanding what pain is, it is difficult to move forward and discuss interventions. There are a multitude of different approaches that can be taken when discussing the biology of pain and numerous important aspects to consider. The following four points that Mosley discussed in one of his papers are pivotal to a complete current understanding of pain.3
- Pain does not give us a measure on the current state of the tissue.Pain is modulated by a number of different factors including those from the somatic, psychological, and social domains.3
- This has been shown through numerous studies on both animal and human subjects. These data have shown that pain, nociceptor activity and the state of the tissue are not isomorphically related at all but are modulated by a variety of factors.3
- Nociception is neither sufficient or even necessary for the experience of pain even though it is the most common driver of the pain experience.7
- The influences on pain are varied and seem to be heavily dependent on the context that the noxious input is evaluated under. Some areas that have been shown to modulate pain include:
- Inflammatory mediators.
- Tissue temperature.
- Blood flow.
- Attention (results are mixed)
- Social context.
- As pain persists the relationship between the perception of pain and the state of the tissue becomes even more imprecise.3
- The number of changes that occur in response to activity of the system are large and the list of those identified is growing at a rapid rate. As nociception persists the neurons transmitting nociception and the pain networks in the brain become sensitized.3 Clinically these changes manifest as hyperalgesia and allodynia not only in relation to tactile stimuli but also movement. This is a key concept in understanding the role of movement in pain. Persistent pain can result in changes in the proprioceptive representation of the painful body part in the primary sensory cortex.3,7-10This can have implications for motor control since it is known that experimental disruption of these maps results in disrupted motor planning. There is a mounting body of evidence that these changes can become part of the overall issue.3,8,10,11
- Pain can be “conceptualized as a conscious correlate of the implicit perception that tissue is in danger.”3
- The neuromatrix theory fits our current knowledge of biology and neuroscience and is flexible enough to grow with the research. Two very important components to the theory. Pain is just one of various outputs from the CNS in response to perceived threat and it is this threat perception that drives the outputs – not the actual threat.3
In a clinical sense, exercise is an extremely powerful tool for the clinician, and along with patient education and manual therapy makes up the three major intervention components that have demonstrated significant value in the treatment of pain. Exercise has been shown to give improvements in many different areas such as improved mood and a reduction in perceived pain,12 hypoalgesic response in both males and females,13improvement in disability scores in LBP patients discharged to exercise vs a control group post therapy,14 etc. This is just a smattering of the research that shows positive outcomes when looking at exercises effect on pain. Because of this it may come as a surprise that a recent review of the literature concluded that “the findings do not support the notion that the treatment effects of exercise therapy in cLBP are directly attributable to changes in the musculoskeletal system.”15 The authors went on to discuss that these results suggest that the benefits of exercise may be more related to “more ‘central’ [rather] than local [factors], perhaps involving psychological, cognitive or neurophysiological (cortical organisation) adaptations.”15
As with any systematic review it is important to avoid the argumentum ad ignorantiambecause lack of evidence is not evidence of any absence but should merely result in a withholding of judgment on the subject. This reasoning was carried out to a somewhat humorous conclusion in a study published in the British Journal of Sports Medicine titled “Parachute use to prevent death and major trauma related to gravitational challenge: systematic review of randomised controlled trials.” It was concluded that “As with many interventions intended to prevent ill-health, the effectiveness of parachutes has not been subjected to rigorous evaluation by using randomised controlled trials. Advocates of evidence based medicine have criticised the adoption of interventions evaluated by using only observational data. We think that everyone might benefit if the most radical protagonists of evidence based medicine organised and participated in a double-blind, randomised, placebo controlled, crossover trial of the parachute.” It is hopefully obvious that in many cases drawing a firm conclusion based on minimal to no evidence should be avoided. That said, there is some growing body of data available on the topic that indicates changes in bio-motor abilities are likely not the only consideration and many treatments that are promoted, such as stabilizing exercise in low back pain (LBP), are only marginally better than placebo at best.15,16
This leaves the idea of motor changes as a result of pain an interesting subject area to consider. Numerous central changes occur as a result of pain that result in altered movement,8 a reduction in variability with movement,11 and altered body perception.10Patients with LBP have been shown to have proprioception deficits, perform poorly on judging movement, have poor tactile acuity, have more difficulty identifying letters traced on their backs, and have issues with disassociation of their backs.10 The interplay between body perception and the movement repertoire of an individual is so close that it even persists when amputees deal with phantom limb movements.10
The good news is that these changes can be reversed, they can occur rapidly and they can be utilized in the clinic. Simple things such as setting up a mirror to allow patients who experience pain with movement to view their motion has been demonstrated to reduce reported pain and speed its resolution.9,10,17 Even the simple act of crossing the arms has an analgesic effect.18 The body of knowledge on this subject is still in its infancy but is also quite promising. Things like graded motor imagery, graded exposure, novel movements, and the like are all showing some potential benefits. It has been demonstrated that cortical changes that occur can be reversed through the application of skilled motor training in those with recurrent pain.19 What this means from a pain management perspective is still speculative; however the authors concluded that these findings support the efficacy of the utilization of skilled motor training for patients with recurrent pain.19
In conclusion the idea of introducing novel movement into rehabilitation as discussed by Butler and Moseley is an excellent starting point.7 Pain resolution starts with patient education and understanding. The goal here is to get your patients to understand pain so that they do not fear it. Once they accept that hurt doesn’t equal harm, graded exposure and pacing strategies based on patient goals are introduced. With this accomplished movement is utilized to target the virtual body from the bottom up. There are many ways that movement can be varied to allow for variability and novelty. Explain Pain lists thirteen different approaches that can be used to change the perception of any movement.7 Working through these variations will assist in accessing and changing the virtual body as well as reducing the perception of threat associated with the movement strategies.
- Imagined movements.
- Alter gravitational influences.
- Vary the balance challenges.
- Vary visual input.
- Alter the environment.
- Perform the movement in various emotional states.
- Add distractions.
- Plan functional activities that include the painful movement.
- Add variety to the functional tasks.
- Perform movements with the surrounding tissues in a relaxed state.
- Play with the compensatory movement strategies developed.
- Ad lib and have fun.
1. Asimov I. The relativity of wrong. The Skeptical Inquirer. 1989;14:35–44.
2. Iannetti GD, Mouraux A. From the neuromatrix to the pain matrix (and back). Exp Brain Res. 2010;205(1):1–12. doi:10.1007/s00221-010-2340-1.
3. Moseley GL. Reconceptualising pain according to modern pain science. Phys. Ther. Rev.2007;12(3):169–178. doi:10.1179/108331907X223010.
4. Anderson PW. More is different. Science. 1972;177(4047):393–396. doi:10.1126/science.177.4047.393.
5. Thacker MA, Moseley GL. First-person neuroscience and the understanding of pain.Med. J. Aust. 2012;196(6):410–411.
6. Larter R. Pain and Emergence. Personal Communication. 2013.
7. Butler DS, Moseley GL. Explain Pain. Noigroup Publications; 2004.
8. Hodges PW, Tucker K. Moving differently in pain: A new theory to explain the adaptation to pain. Pain. 2011;152(S):S90–S98. doi:10.1016/j.pain.2010.10.020.
9. Wand BM, Tulloch VM, George PJ, et al. Seeing It Helps: Movement-related Back Pain is Reduced by Visualization of the Back During Movement. The Clinical Journal of Pain. 2012;28(7):602–608.
10. Wand BM, Parkitny L, O’Connell NE, et al. Cortical changes in chronic low back pain: Current state of the art and implications for clinical practice. Manual Therapy. 2011;16(1):15–20. doi:10.1016/j.math.2010.06.008.
11. Madeleine P, Mathiassen SE, Arendt-Nielsen L. Changes in the degree of motor variability associated with experimental and chronic neck–shoulder pain during a standardised repetitive arm movement. Exp Brain Res. 2007;185(4):689–698. doi:10.1007/s00221-007-1199-2.
12. Hoffman MD, Hoffman DR. Does aerobic exercise improve pain perception and mood? A review of the evidence related to healthy and chronic pain subjects. Curr Pain Headache Rep. 2007;11(2):93–97. doi:10.1007/s11916-007-0004-z.
13. Drury DG, Greenwood K, Stuempfle KJ, Koltyn KF. Changes in pain perception in women during and following an exhaustive incremental cycling exercise. Journal of Sports Science and Medicine. 2005;4(2005):215–222.
14. Henchoz Y, de Goumoëns P, Norberg M, Paillex R, So AKL. Role of physical exercise in low back pain rehabilitation: A randomized controlled trial of a three-month exercise program in patients who have completed multidisciplinary rehabilitation. Spine. 2010;35(12):1192–1199. doi:10.1097/BRS.0b013e3181bf1de9.
15. Steiger F, Wirth B, Bruin ED, Mannion AF. Is a positive clinical outcome after exercise therapy for chronic non-specific low back pain contingent upon a corresponding improvement in the targeted aspect(s) of performance? A systematic review. Eur Spine J. 2011;21(4):575–598. doi:10.1007/s00586-011-2045-6.
16. O’Sullivan P. It’s time for change with the management of non-specific chronic low back pain. British Journal of Sports Medicine. 2012;46(4):224–227. doi:10.1136/bjsm.2010.081638.
17. Boudreau SA, Farina D, Falla D. The role of motor learning and neuroplasticity in designing rehabilitation approaches for musculoskeletal pain disorders. Manual Therapy. 2010;15(5):410–414. doi:10.1016/j.math.2010.05.008.
18. Gallace A, Torta DME, Moseley GL, Iannetti GD. The analgesic effect of crossing the arms. Pain. 2011;152(6):1418–1423. doi:10.1016/j.pain.2011.02.029.
19. Tsao H, Galea MP, Hodges PW. Driving plasticity in the motor cortex in recurrent low back pain. European Journal of Pain. 2010;14(8):832–839. doi:10.1016/j.ejpain.2010.01.001