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WHAT IS PAIN SCIENCE? Entire books have been written on the detailed neurophysiology of pain and what new research is revealing about pain perception. It is beyond the scope of this article to cover these points in detail, and the science is not entirely in agreement. However, let's look at some key pain science concepts that are relevant for massage therapists. Pain is essentially an alarm system that alerts us to physical emergencies or issues that need attention. It is the body's way of telling us to take action of some kind. Even chronic pain is the body warning us as to what it perceives as something we need to address. Current research tells us that pain is generated in the brain, not at the location of issue. So, pain science literature refers to pain as an output of the brain. The brain tells us whether there is pain, or not, and makes this determination through an interconnected and complex system that includes various parts of the central nervous system. The body then responds. Like any decent alarm system, the body's sensitivity can get altered (think of this as an alarm system that is out of calibration) and thus alert us to issues that don't require a high level of response. The process of pain recognition starts with the nociceptors, which are sensory receptors that exist throughout the body. Nociceptors are sensitive to, and send signals about, chemical, mechanical, and/or thermal stimuli to the brain. We call this process of information transfer nociception. The brain evaluates a wide number of factors in its determination of whether to register pain from nociception. In an instance in which an extremely strong (noxious) signal is registered, the signal may skip the brain first, going straight to the motor fibers leaving the spinal cord. This is why we pull our hands away so quickly from a hot stove, usually prior to feeling pain. There is an abundance of evidence in which people have extreme tissue damage, and subsequent nociception, with little or no pain. This is seen in sports with players continuing to play with an injury or on the battlefield when a person "soldiers on" through sometimes horrendous injuries without reporting pain. In contrast, someone can also register extraordinary pain with what seems to be little or no tissue damage, as in allodynia (pain felt from stimulus that should not be painful, like dragging a finger across the skin). Exaggerated pain, as in situations of allodynia, is likely due to an increase in the sensitivity of the central nervous system to the stimulus. This increased sensitivity is called central sensitization and may provide an explanation for numerous situations where pain seems to be much greater than it should be. There are multiple factors that cause pain to be either suppressed or enhanced. Two people exposed to the exact same stimuli may have very different pain experiences. This is not just about pain tolerance. It is a complex process that involves sensory processing, memory, biomechanical stresses, tissue chemistry, psychological and social factors, and other physiological issues that can influence the pain someone feels. Any client's pain experience can be a blend of these various factors, with some factor(s) playing more of a role than others. For example, generally, with acute injuries, tissue damage will play the largest role. Yet with chronic pain, a wide diversity of factors that may not be related to tissue damage can produce pain. In the late 1970s, psychiatrist George Engel proposed a holistic model based on the emerging views of systems theory. He noted that in some instances, an illness or injury is not simply a biological problem alone but includes psychological and/or social factors that influence the person's experience. This framework is known as the biopsychosocial or BPS model. A number of psychological or social factors, such as attitudes, beliefs, culture, and mood, can play a part in the level of pain a patient experiences. Stress and anxiety have also long been associated with increased levels of pain. We have also learned that fear of pain and movement avoidance (called kinesiophobia) can increase the disability period and lead to greater pain levels. These various psychosocial factors can be difficult to measure or identify, but they can play a role in certain pain complaints. 70 m a s s a g e & b o d y w o r k m a y / j u n e 2 0 1 8