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Exercises - What's the Use?
October 20, 2012 by Dr Matthew D. Long
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Exercises - What's the Use?
October 20, 2012 by Dr Matthew D. Long
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Exercises - What's the Use?
October 20, 2012 by Dr Matthew D. Long
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One of the most frequent criticisms of chiropractic care seems to be that it is largely passive and that exercises don't feature strongly in overall management. While this is clearly a simplification it does perhaps illustrate the fact that differences of opinion about the role of exercise still exist. So the question remains, do exercises help in the management of spinal pain and what form should they take?
Traditional management of spinal pain has evolved over recent decades. The initial paradigm emphasising rest gave way to methods of strengthening spinal muscles, particularly the so-called 'core' groups. This was subsequently refined to a tailored approach, in which specific exercises were individually hand-crafted for the deficits that a particular patient might exhibit. But has all of this refinement led to better outcomes?
Perhaps not.
There is now a growing undercurrent of dissatisfaction in the literature with tailored exercise programs and a re-evaluation of our thinking about what exercise actually does for back pain patients (23). Do exercises really target the functional deficits that we detect in our patients? Or are they doing something else entirely? Where is the evidence that stabilisation exercises, motor control exercises, core strength training or Pilates have any greater benefit for lower back pain patients than a generalised re-activation and simple exercise such as walking (1, 2, 3, 4)? Indeed, a recent paper by Shnayderman et al (5) found that a six week aerobic walking program was just as effective as a trunk muscle strengthening program over the same duration for chronic back pain patients. Although it is popular, Pilates has shown no advantage over other forms of exercise (6, 7, 8). Indeed, Critchley and colleagues (9) found that while Pilates exercises did increase activity of the transversus abdominis muscle, it only did so during Pilates training and the effect was not transferrable to other situations.
Perhaps even more damning evidence comes from Steiger and colleagues' paper in the European Spine Journal (10) entitled, "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." This study makes the case that while exercise does seem to help recovery from chronic lower back pain, it is not due to a simultaneous improvement in functional deficits that the exercises were purported to address. Many patients improve, yet continue to harbour the same muscular abnormalities that they exhibited at the outset. Conversely, some patients showed a marked improvement in muscular recruitment, control and strength, yet gained nothing in the way of pain relief.
Similarly, Mannion et al (11) looked at spine stabilisation exercises and their effect upon abdominal muscle function. They found that;
"Neither baseline lateral abdominal muscle function nor its improvement after a programme of stabilisation exercises was a statistical predictor of a good clinical outcome. It is hence difficult to attribute the therapeutic result to any specific effects of the exercises on these trunk muscles. The association between changes in catastrophising and outcome serves to encourage further investigation on larger groups of patients to clarify whether stabilisation exercises have some sort of ‘‘central’’ effect, unrelated to abdominal muscle function per se."
So exercise may well help, but not for the reasons that we had supposed. Could it be that exercise does not help by addressing a functional deficit in the muscles or joints of the spine - but actually serves to retrain the brain? Steiger suggested that;
"Recently, alternative theories have been proposed that aim to explain the lack of specificity of exercise therapy in cLBP. One suggests that the treatment effects of many cLBP therapies may be attributable to changes within the brain of cLBP patients rather than specific changes in the musculo-skeletal system. Evidence supporting the involvement of cortical reorganisation in cLBP comes from the finding of central nervous system changes proportional to the severity and duration of the cLBP and alterations (grey matter density loss) in the brain of cLBP patients. It is conceivable that other changes elicited by exercise therapy, e.g. improvements in self-efficacy, coping strategies and fear-avoidance, modification of motor control patterns as a consequence of a re-weighting of sensory input, changes in cortical organisation or simply a positive therapist–patient interaction/relationship may be responsible for the improvements in self-reported pain and disability." (10)
This notion sits well with our current understanding of the neurological dimensions of chronic back pain. Far from being a mechanical, tissue-based disorder, chronic spinal pain is associated with significant changes in central function - ultimately producing a distorted body schema (12, 13, 14, 15). Proprioception is altered and limbic responses are heightened. Indeed, the limbic dimensions of chronic back pain may ultimately play a large role in our understanding of the disorder, and its recovery. Perhaps one of the roles of exercise is to 'convince' the limbic system that fear-avoidance of movement and vigilance to pain are no longer necessary. By encouraging the patient to participate in supervised, or at least endorsed, activities the associated perception of threat might reduce. As Mannion and colleagues write,
"Studies have emerged showing that the effects of physical treatment, with no specific cognitive-behavioural component, may be mediated by a decrease in pain catastrophising. Possibly, this is the result of ‘'enforced' exposure to activities that challenge the notion of movement representing an impending threat, allowing the patient to enjoy the positive experience of completing the given exercises without undue harm."
Is this why walking and other seemingly benign activities might be just as effective as traditional exercise approaches to back pain? Does walking serve as an officially sanctioned excuse to engage painful tissues and provide data to the brain. Such data might be useful for retaining the limbic system and also postural/proprioceptive awareness.
Morone and colleagues (16) took this a step further and utilised 'perceptive rehabilitation' to target the distorted body schema. They asked patients to lie on an undulating surface and then guided them through perceptive exercises that focus on tactile discrimination. This retraining was effective in reducing pain. Other approaches that seek to improve trunk proprioception and balance, rather than muscle function, also seem helpful (17). Finally, we should also note that basic science research has shown that physical exercise affects cell proliferation in the intervertebral discs (18), not to mention bone density.
So, does this mean that exercises are a waste of time when treating spinal pain?
Not at all. But we must be mindful of their role and what we are trying to achieve. Furthermore, the evidence regarding exercise efficacy for neck pain is somewhat different. Strength training does seem helpful for chronic cervical pain (19, 20, 21), but again, perhaps due to global alterations in pain perception, rather than a specific training response. This notion was further supported by Anderson et al (22), who found that patients with chronic trapezius pain benefitted from resistance training by exhibiting a reduction in neck pain and also in the sensitivity of a reference muscle in the leg (tibialis anterior) - far removed from the site of symptoms - suggesting a central adaptation.
Whatever the case, the age-old advice to 'Take up thy bed and walk' has never been more relevant.
Something to think about...
Dr Matthew D. Long
BSc (Syd) M.Chiro (Macq)
Traditional management of spinal pain has evolved over recent decades. The initial paradigm emphasising rest gave way to methods of strengthening spinal muscles, particularly the so-called 'core' groups. This was subsequently refined to a tailored approach, in which specific exercises were individually hand-crafted for the deficits that a particular patient might exhibit. But has all of this refinement led to better outcomes?
Perhaps not.
There is now a growing undercurrent of dissatisfaction in the literature with tailored exercise programs and a re-evaluation of our thinking about what exercise actually does for back pain patients (23). Do exercises really target the functional deficits that we detect in our patients? Or are they doing something else entirely? Where is the evidence that stabilisation exercises, motor control exercises, core strength training or Pilates have any greater benefit for lower back pain patients than a generalised re-activation and simple exercise such as walking (1, 2, 3, 4)? Indeed, a recent paper by Shnayderman et al (5) found that a six week aerobic walking program was just as effective as a trunk muscle strengthening program over the same duration for chronic back pain patients. Although it is popular, Pilates has shown no advantage over other forms of exercise (6, 7, 8). Indeed, Critchley and colleagues (9) found that while Pilates exercises did increase activity of the transversus abdominis muscle, it only did so during Pilates training and the effect was not transferrable to other situations.
Perhaps even more damning evidence comes from Steiger and colleagues' paper in the European Spine Journal (10) entitled, "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." This study makes the case that while exercise does seem to help recovery from chronic lower back pain, it is not due to a simultaneous improvement in functional deficits that the exercises were purported to address. Many patients improve, yet continue to harbour the same muscular abnormalities that they exhibited at the outset. Conversely, some patients showed a marked improvement in muscular recruitment, control and strength, yet gained nothing in the way of pain relief.
Similarly, Mannion et al (11) looked at spine stabilisation exercises and their effect upon abdominal muscle function. They found that;
"Neither baseline lateral abdominal muscle function nor its improvement after a programme of stabilisation exercises was a statistical predictor of a good clinical outcome. It is hence difficult to attribute the therapeutic result to any specific effects of the exercises on these trunk muscles. The association between changes in catastrophising and outcome serves to encourage further investigation on larger groups of patients to clarify whether stabilisation exercises have some sort of ‘‘central’’ effect, unrelated to abdominal muscle function per se."
So exercise may well help, but not for the reasons that we had supposed. Could it be that exercise does not help by addressing a functional deficit in the muscles or joints of the spine - but actually serves to retrain the brain? Steiger suggested that;
"Recently, alternative theories have been proposed that aim to explain the lack of specificity of exercise therapy in cLBP. One suggests that the treatment effects of many cLBP therapies may be attributable to changes within the brain of cLBP patients rather than specific changes in the musculo-skeletal system. Evidence supporting the involvement of cortical reorganisation in cLBP comes from the finding of central nervous system changes proportional to the severity and duration of the cLBP and alterations (grey matter density loss) in the brain of cLBP patients. It is conceivable that other changes elicited by exercise therapy, e.g. improvements in self-efficacy, coping strategies and fear-avoidance, modification of motor control patterns as a consequence of a re-weighting of sensory input, changes in cortical organisation or simply a positive therapist–patient interaction/relationship may be responsible for the improvements in self-reported pain and disability." (10)
This notion sits well with our current understanding of the neurological dimensions of chronic back pain. Far from being a mechanical, tissue-based disorder, chronic spinal pain is associated with significant changes in central function - ultimately producing a distorted body schema (12, 13, 14, 15). Proprioception is altered and limbic responses are heightened. Indeed, the limbic dimensions of chronic back pain may ultimately play a large role in our understanding of the disorder, and its recovery. Perhaps one of the roles of exercise is to 'convince' the limbic system that fear-avoidance of movement and vigilance to pain are no longer necessary. By encouraging the patient to participate in supervised, or at least endorsed, activities the associated perception of threat might reduce. As Mannion and colleagues write,
"Studies have emerged showing that the effects of physical treatment, with no specific cognitive-behavioural component, may be mediated by a decrease in pain catastrophising. Possibly, this is the result of ‘'enforced' exposure to activities that challenge the notion of movement representing an impending threat, allowing the patient to enjoy the positive experience of completing the given exercises without undue harm."
Is this why walking and other seemingly benign activities might be just as effective as traditional exercise approaches to back pain? Does walking serve as an officially sanctioned excuse to engage painful tissues and provide data to the brain. Such data might be useful for retaining the limbic system and also postural/proprioceptive awareness.
Morone and colleagues (16) took this a step further and utilised 'perceptive rehabilitation' to target the distorted body schema. They asked patients to lie on an undulating surface and then guided them through perceptive exercises that focus on tactile discrimination. This retraining was effective in reducing pain. Other approaches that seek to improve trunk proprioception and balance, rather than muscle function, also seem helpful (17). Finally, we should also note that basic science research has shown that physical exercise affects cell proliferation in the intervertebral discs (18), not to mention bone density.
So, does this mean that exercises are a waste of time when treating spinal pain?
Not at all. But we must be mindful of their role and what we are trying to achieve. Furthermore, the evidence regarding exercise efficacy for neck pain is somewhat different. Strength training does seem helpful for chronic cervical pain (19, 20, 21), but again, perhaps due to global alterations in pain perception, rather than a specific training response. This notion was further supported by Anderson et al (22), who found that patients with chronic trapezius pain benefitted from resistance training by exhibiting a reduction in neck pain and also in the sensitivity of a reference muscle in the leg (tibialis anterior) - far removed from the site of symptoms - suggesting a central adaptation.
Whatever the case, the age-old advice to 'Take up thy bed and walk' has never been more relevant.
Something to think about...
Dr Matthew D. Long
BSc (Syd) M.Chiro (Macq)
References:
1. Macedo, L. G., Maher, C. G., Latimer, J., & McAuley, J. H. (2009). Motor control exercise for persistent, nonspecific low back pain: a systematic review. Physical therapy, 89(1), 9–25. doi:10.2522/ptj.20080103
2. Vasseljen, O., Unsgaard-Tøndel, M., Westad, C., & Mork, P. J. (2012). Effect of Core Stability Exercises on Feed-Forward Activation of Deep Abdominal Muscles in Chronic Low Back Pain. Spine, 37(13), 1101–1108. doi:10.1097/BRS.0b013e318241377c
3. Ferreira, P. H., Ferreira, M. L., Maher, C. G., Herbert, R. D., & Refshauge, K. (2006). Specific stabilisation exercise for spinal and pelvic pain: a systematic review. The Australian journal of physiotherapy, 52(2), 79–88.
4. Rackwitz, B., de Bie, R., Limm, H., Garnier, von, K., Ewert, T., & Stucki, G. (2006). Segmental stabilizing exercises and low back pain. What is the evidence? A systematic review of randomized controlled trials. Clinical rehabilitation, 20(7), 553–567.
5. Shnayderman, I., & Katz-Leurer, M. (2012). An aerobic walking programme versus muscle strengthening programme for chronic low back pain: a randomized controlled trial. Clinical rehabilitation. doi:10.1177/0269215512453353
6. Lim, E. C. W., Poh, R. L. C., Low, A. Y., & Wong, W. P. (2011). Effects of Pilates-based exercises on pain and disability in individuals with persistent nonspecific low back pain: a systematic review with meta-analysis. The Journal of Orthopaedic and Sports Physical Therapy, 41(2), 70–80. doi:10.2519/jospt.2011.3393
7. Pereira, L. M., Obara, K., Dias, J. M., Menacho, M. O., Guariglia, D. A., Schiavoni, D., Pereira, H. M., et al. (2012). Comparing the Pilates method with no exercise or lumbar stabilization for pain and functionality in patients with chronic low back pain: systematic review and meta-analysis. Clinical rehabilitation, 26(1), 10–20. doi:10.1177/0269215511411113
8. Wajswelner, H., Metcalf, B., & Bennell, K. (2012). Clinical Pilates versus general exercise for chronic low back pain: randomized trial. MEDICINE AND SCIENCE IN SPORTS AND EXERCISE, 44(7), 1197–1205. doi:10.1249/MSS.0b013e318248f665
9. Critchley, D. J., Pierson, Z., & Battersby, G. (2011). Effect of Pilates mat exercises and conventional exercise programmes on transversus abdominis and obliquus internus abdominis activity: Pilot randomised trial. Manual Therapy, 16(2), 183–189. doi:10.1016/j.math.2010.10.007
10. Steiger, F., Wirth, B., de Bruin, E. D., & Mannion, A. F. (2012). 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. European spine journal, 21(4), 575–598. doi:10.1007/s00586-011-2045-6
11. Mannion, A. F., Caporaso, F., Pulkovski, N., & Sprott, H. (2012). Spine stabilisation exercises in the treatment of chronic low back pain: a good clinical outcome is not associated with improved abdominal muscle function. European spine journal, 21(7), 1301–1310. doi:10.1007/s00586-012-2155-9
12. Bray, H., & 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. doi:10.1136/bjsm.2009.061978
13. Moseley, G. L. (2008). I can't find it! Distorted body image and tactile dysfunction in patients with chronic back pain. Pain, 140(1), 239–243. doi:10.1016/j.pain.2008.08.001
14. Moseley, G. L., Gallagher, L., & Gallace, A. (2012). Neglect-like tactile dysfunction in chronic back pain. Neurology, 79(4), 327–332. doi:10.1212/WNL.0b013e318260cba2
15. Luomajoki, H., & Moseley, G. L. (2011). Tactile acuity and lumbopelvic motor control in patients with back pain and healthy controls. British journal of sports medicine, 45(5), 437–440. doi:10.1136/bjsm.2009.060731
16. Morone, G., Iosa, M., Paolucci, T., Fusco, A., Alcuri, R., Spadini, E., Saraceni, V. M., et al. (2012). Efficacy of perceptive rehabilitation in the treatment of chronic nonspecific low back pain through a new tool: a randomized clinical study. Clinical rehabilitation, 26(4), 339–350. doi:10.1177/0269215511414443
17. Gatti, R., Faccendini, S., Tettamanti, A., Barbero, M., Balestri, A., & Calori, G. (2011). Efficacy of trunk balance exercises for individuals with chronic low back pain: a randomized clinical trial. The Journal of Orthopaedic and Sports Physical Therapy, 41(8), 542–552. doi:10.2519/jospt.2011.3413
18. Sasaki, N., Henriksson, H. B., Runesson, E., Larsson, K., Sekiguchi, M., Kikuchi, S.-I., Konno, S.-I., et al. (2012). Physical Exercise Affects Cell Proliferation in Lumbar Intervertebral Disc Regions in Rats. Spine, 37(17), 1440–1447. doi:10.1097/BRS.0b013e31824ff87d
19. Andersen, L. L., Saervoll, C. A., Mortensen, O. S., Poulsen, O. M., Hannerz, H., & Zebis, M. K. (2011). Effectiveness of small daily amounts of progressive resistance training for frequent neck/shoulder pain: Randomised controlled trial. Pain, 152(2), 440–446. doi:10.1016/j.pain.2010.11.016
20. Salo, P. K., Hakkinen, A. H., Kautiainen, H., & Ylinen, J. J. (2010). Effect of neck strength training on health-related quality of life in females with chronic neck pain: a randomized controlled 1-year follow-up study. Health and quality of life outcomes, 8(1), 48. doi:10.1186/1477-7525-8-48
21. Falla, D., O'Leary, S., Farina, D., & Jull, G. (2012). The change in deep cervical flexor activity after training is associated with the degree of pain reduction in patients with chronic neck pain. The Clinical journal of pain, 28(7), 628–634. doi:10.1097/AJP.0b013e31823e9378
22. Andersen, L. L., Andersen, C. H., Sundstrup, E., Jakobsen, M. D., Mortensen, O. S., & Zebis, M. K. (2012). Central adaptation of pain perception in response to rehabilitation of musculoskeletal pain: randomized controlled trial. Pain physician, 15(5), 385–394.
23. Lederman, E. (2010). The myth of core stability. Journal of bodywork and movement therapies, 14(1), 84–98. doi:10.1016/j.jbmt.2009.08.001
1. Macedo, L. G., Maher, C. G., Latimer, J., & McAuley, J. H. (2009). Motor control exercise for persistent, nonspecific low back pain: a systematic review. Physical therapy, 89(1), 9–25. doi:10.2522/ptj.20080103
2. Vasseljen, O., Unsgaard-Tøndel, M., Westad, C., & Mork, P. J. (2012). Effect of Core Stability Exercises on Feed-Forward Activation of Deep Abdominal Muscles in Chronic Low Back Pain. Spine, 37(13), 1101–1108. doi:10.1097/BRS.0b013e318241377c
3. Ferreira, P. H., Ferreira, M. L., Maher, C. G., Herbert, R. D., & Refshauge, K. (2006). Specific stabilisation exercise for spinal and pelvic pain: a systematic review. The Australian journal of physiotherapy, 52(2), 79–88.
4. Rackwitz, B., de Bie, R., Limm, H., Garnier, von, K., Ewert, T., & Stucki, G. (2006). Segmental stabilizing exercises and low back pain. What is the evidence? A systematic review of randomized controlled trials. Clinical rehabilitation, 20(7), 553–567.
5. Shnayderman, I., & Katz-Leurer, M. (2012). An aerobic walking programme versus muscle strengthening programme for chronic low back pain: a randomized controlled trial. Clinical rehabilitation. doi:10.1177/0269215512453353
6. Lim, E. C. W., Poh, R. L. C., Low, A. Y., & Wong, W. P. (2011). Effects of Pilates-based exercises on pain and disability in individuals with persistent nonspecific low back pain: a systematic review with meta-analysis. The Journal of Orthopaedic and Sports Physical Therapy, 41(2), 70–80. doi:10.2519/jospt.2011.3393
7. Pereira, L. M., Obara, K., Dias, J. M., Menacho, M. O., Guariglia, D. A., Schiavoni, D., Pereira, H. M., et al. (2012). Comparing the Pilates method with no exercise or lumbar stabilization for pain and functionality in patients with chronic low back pain: systematic review and meta-analysis. Clinical rehabilitation, 26(1), 10–20. doi:10.1177/0269215511411113
8. Wajswelner, H., Metcalf, B., & Bennell, K. (2012). Clinical Pilates versus general exercise for chronic low back pain: randomized trial. MEDICINE AND SCIENCE IN SPORTS AND EXERCISE, 44(7), 1197–1205. doi:10.1249/MSS.0b013e318248f665
9. Critchley, D. J., Pierson, Z., & Battersby, G. (2011). Effect of Pilates mat exercises and conventional exercise programmes on transversus abdominis and obliquus internus abdominis activity: Pilot randomised trial. Manual Therapy, 16(2), 183–189. doi:10.1016/j.math.2010.10.007
10. Steiger, F., Wirth, B., de Bruin, E. D., & Mannion, A. F. (2012). 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. European spine journal, 21(4), 575–598. doi:10.1007/s00586-011-2045-6
11. Mannion, A. F., Caporaso, F., Pulkovski, N., & Sprott, H. (2012). Spine stabilisation exercises in the treatment of chronic low back pain: a good clinical outcome is not associated with improved abdominal muscle function. European spine journal, 21(7), 1301–1310. doi:10.1007/s00586-012-2155-9
12. Bray, H., & 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. doi:10.1136/bjsm.2009.061978
13. Moseley, G. L. (2008). I can't find it! Distorted body image and tactile dysfunction in patients with chronic back pain. Pain, 140(1), 239–243. doi:10.1016/j.pain.2008.08.001
14. Moseley, G. L., Gallagher, L., & Gallace, A. (2012). Neglect-like tactile dysfunction in chronic back pain. Neurology, 79(4), 327–332. doi:10.1212/WNL.0b013e318260cba2
15. Luomajoki, H., & Moseley, G. L. (2011). Tactile acuity and lumbopelvic motor control in patients with back pain and healthy controls. British journal of sports medicine, 45(5), 437–440. doi:10.1136/bjsm.2009.060731
16. Morone, G., Iosa, M., Paolucci, T., Fusco, A., Alcuri, R., Spadini, E., Saraceni, V. M., et al. (2012). Efficacy of perceptive rehabilitation in the treatment of chronic nonspecific low back pain through a new tool: a randomized clinical study. Clinical rehabilitation, 26(4), 339–350. doi:10.1177/0269215511414443
17. Gatti, R., Faccendini, S., Tettamanti, A., Barbero, M., Balestri, A., & Calori, G. (2011). Efficacy of trunk balance exercises for individuals with chronic low back pain: a randomized clinical trial. The Journal of Orthopaedic and Sports Physical Therapy, 41(8), 542–552. doi:10.2519/jospt.2011.3413
18. Sasaki, N., Henriksson, H. B., Runesson, E., Larsson, K., Sekiguchi, M., Kikuchi, S.-I., Konno, S.-I., et al. (2012). Physical Exercise Affects Cell Proliferation in Lumbar Intervertebral Disc Regions in Rats. Spine, 37(17), 1440–1447. doi:10.1097/BRS.0b013e31824ff87d
19. Andersen, L. L., Saervoll, C. A., Mortensen, O. S., Poulsen, O. M., Hannerz, H., & Zebis, M. K. (2011). Effectiveness of small daily amounts of progressive resistance training for frequent neck/shoulder pain: Randomised controlled trial. Pain, 152(2), 440–446. doi:10.1016/j.pain.2010.11.016
20. Salo, P. K., Hakkinen, A. H., Kautiainen, H., & Ylinen, J. J. (2010). Effect of neck strength training on health-related quality of life in females with chronic neck pain: a randomized controlled 1-year follow-up study. Health and quality of life outcomes, 8(1), 48. doi:10.1186/1477-7525-8-48
21. Falla, D., O'Leary, S., Farina, D., & Jull, G. (2012). The change in deep cervical flexor activity after training is associated with the degree of pain reduction in patients with chronic neck pain. The Clinical journal of pain, 28(7), 628–634. doi:10.1097/AJP.0b013e31823e9378
22. Andersen, L. L., Andersen, C. H., Sundstrup, E., Jakobsen, M. D., Mortensen, O. S., & Zebis, M. K. (2012). Central adaptation of pain perception in response to rehabilitation of musculoskeletal pain: randomized controlled trial. Pain physician, 15(5), 385–394.
23. Lederman, E. (2010). The myth of core stability. Journal of bodywork and movement therapies, 14(1), 84–98. doi:10.1016/j.jbmt.2009.08.001