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Understanding the science of pain

This is an excerpt from Sports Massage for Injury Care.

An explosion of research on pain in recent years has led to new insights into, as well as great confusion about, the origins of pain, the connections between injury and pain, and the psychological and social contributions to the perception of pain. This broadened knowledge of the complexity of pain has also affected the way manual therapy practitioners approach their work with clients.

By contrast, as the understanding of the mechanisms of pain perception and pain generation has progressed, many researchers and practitioners have reframed the discussion of pain in relation to injury by emphasizing that pain is a complex experience, involving many parts of the brain, and that pain perception is influenced by psychosocial factors that include previous pain experiences, thoughts and feelings about previous pain experiences, emotional states, and even personal relationships. These elements of the pain experience have been recognized for years but have been downplayed in favor of a pathomechanical model of pain that described the stimulation of pain receptors in the tissue when an injury or insult occurred there. These receptors would then stimulate the pain region of the brain, and pain would be felt. It now appears that pain receptors do not exist, but nociceptive receptors do and are stimulated by a variety of noxious stimuli, including pressure, temperature, and inflammatory markers. These receptors send signals to the brain via the spinal cord, and the brain evaluates the signal and determines whether the input is pain or not, and then outputs either the sensation of pain or something else, such as an increase in pressure or a feeling of additional warmth. What this means in practical terms for practitioners is that pain intensity does not necessarily correlate with tissue damage. Minor injuries can feel extremely painful, and severe injuries may occur with very little pain. This response is modulated by the brain and is dependent on all the biopsychosocial factors influencing the brain's final output.

In chronic pain conditions, a neural pathway can become sensitized by repeated nociceptive stimulation so that even minor noxious input can trigger output from the brain that causes the patient to feel pain. On the other hand, this does not mean that pain intensity never correlates directly with the amount of tissue damage, and it's critical for practitioners and patients to stay mindful of this fact.

Growing evidence indicates that incorporating pain neuroscience education (PNE) with manual treatment is efficacious for reducing chronic pain. The intent of PNE is to help shift the client's focus away from “my tissues are painful, so they must be injured” to realizing that the brain's perception and interpretation of stimuli emanating from the tissues may not always accurately reflect the degree of tissue damage. Encouraging a client to shift their focus away from the idea that their pain is caused by specific tissue damage has been shown to reduce chronic pain and, more importantly, to reduce pain catastrophization (magnifying the pain and feeling helpless in the presence of pain).

As practitioners and patients read and hear more about the new pain science, they may make the incorrect assumption that the oversimplified phrase “pain is in the brain” means that pain is all in your head. It's incumbent on the professionals to reassure patients that they're not making it all up (as has been the unfortunate experience of many patients). As Whitney Lowe, massage educator and author, has written,

I think one of the biggest obstacles and challenges for those who are carrying the torch of the emerging pain science specialty is to understand how to introduce these ideas to those for whom this view is new. Too often I have seen and heard pain science enthusiasts speak to others with condescension and arrogance. As a teacher I clearly recognize how that produces an immediate degree of defensiveness in a student and that is a significant obstacle to learning. (Lowe 2017, p. 1)

Because knowledge about pain perception continues to emerge and evolve, the other clear message for practitioners and patients is that our prior knowledge and experience about pain and treating patients in pain is not suddenly obsolete or ineffective. “It isn't necessary to throw out all of the valuable learning and clinical experience we have already built upon. But maybe we look at these things through a different set of glasses” (Lowe 2017, p. 1). It is incumbent on sports massage practitioners to discuss with clients the current research about pain and how those research findings will affect the treatment strategies proposed in their particular case.