Back pain is one of the most common anatomical locations for persistent pain. It is also an anatomical area that falls outside the visual field. Therefore, as humans we rely on our proprioceptive mechanisms to give us a sense of position in space, and non visual mechanisms to communicate safety and threat signals to the brain.
BKS Iyengar, the famous Indian yoga teacher, made the following observations about the spine in relation to back bending.
"Backbends are not poses meant for exhibitionism. Backbends are meant to understand the back parts of our bodies. The front body can be seen with the eyes. The back body cannot be seen; it can only be felt. That’s why I say these are the most advanced postures, where the mind begins to look at the back, first on the peripheral level, then inwards, towards the core.
For a yogi, backbends are meant to invert the mind, to observe and to feel—first the back, then the consciousness and the very seer. Through the practice of backbends, by using the senses of perception to look back, and drawing the mind to the back portion of the body, one day meditation comes naturally."
Interestingly, there is evidence to suggest that persistent pain distorts visuospatial perception {1}
Disturbed perpetual awareness of the back is correlated with distress, fear avoidant beliefs, and catastrophizing cognitions about pain. Higher levels of disturbed self-perception are related to increased sensitivity to pressure at the low back [2].
Disrupted perceptual awareness of the back significantly and uniquely contributes to pain intensity.
Suprisingly, disturbed body perception appears to be more strongly associated with pain intensity than psychological distress, fear avoidance beliefs, or an objective measure of lumbar spine sensitivity [2].
Planning and coordination of movement requires an intact perception of the body and its position in space, and movement quality may be compromised if body perception is disrupted. Suboptimal movement patterns might abnormally load the back and contribute to nociceptive input and movement-related pain in those with chronic lower back pain {2].
It has also been hypothesized that danger signals may arise centrally as a result of incongruence between predicted and actual sensory feedback associated with movement by virtue of disrupted body maps {2}. This mechanism might also contribute to the pain experience in people with CLBP whose perception of the back is degraded.
Pain emerges when we conclude our body to be under threat and in need of protection so how the body is perceived should be seen as fundamental to the emergence of pain. In support of this idea are data that show that sensitivity to experimental pain is increased when perception of the body part is distorted by visual manipulation.
Loss of sensory precision and decreased ability to accurately localize sensory input could enhance sensitivity by increasing the salience and threat value of any sensory information, noxious or otherwise, received from the affected area.
Importantly, preliminary data suggest that strategies that likely improve self-perception such as mirror visual feedback and sensory discrimination training may decrease activity-related pain in people with chronic back pain {2}.
In Light on Yoga, Iyengar recommends using a mirror in the “Hints and Cautions” section of the book, prior to describing the asanas.
“When you are doing the asanas in front of a mirror, keep it perpendicular to the floor and let it come down to ground level, for otherwise the poses will look slanting due to the angle of the mirror. You will not be able to observe the movements (or placing of the head and shoulders in the topsy-turvy poses) unless the mirror reaches down to the floor.”
There is also experimental evidence for the role of Iyengar yoga in persistent back pain, demonstrating improvements in functional disability, pain intensity, and depression {3}. The exact mechanisms contributing to this improvement are likely multifactorial, with improvements in visuospatial awareness being simply one variable related to many others (beliefs, cognitions, psychological state etc).
REFERENCES:
Sumitani, M & Shibata, Masahiko & Iwakura, T & Matsuda, Y & Sakaue, G & Inoue, Takaya & Mashimo, T & Miyauchi, Satoru. (2007). Pathologic pain distorts visuospatial perception. Neurology. 68. 152-4. 10.1212/01.wnl.0000250335.56958.f0.
Wand, B. M., Catley, M. J., Rabey, M. I., O'Sullivan, P. B., O'Connell, N. E., & Smith, A. J. (2016). Disrupted self-perception in people with chronic low back pain. Further evaluation of the fremantle back awareness questionnaire. The Journal of Pain, 17(9), 1001–1012.
Williams, Kimberly & Abildso, Christiaan & Steinberg, Lois & Doyle, Edward & Epstein, Beverly & Smith, David & Hobbs, Gerry & Gross, Richard & Kelley, George & Cooper, Linda. (2009). Evaluation of the Effectiveness and Efficacy of Iyengar Yoga Therapy on Chronic Low Back Pain. Spine. 34. 2066-76. 10.1097/BRS.0b013e3181b315cc.