Pain is huge business in the United States, costing American adults between $560 to $630 billion per year — or about $2,000 per adult per year in spending — on treatment, according to a 2011 report by the Institute of Medicine. Most pain treatments use the biomechanical model, which infers that pain stems from tissue damage or a structural abnormality, such as poor posture or faulty movement patterns. While some of the causes may be true, such as cancer or a broken leg, emerging scientific evidence show that pain perception could most likely be an interaction among environmental, social, psychological, and biological factors rather than structural changes or damage alone. In fact, the nervous system’s perception of pain is so powerful that it can be changed with movement adaptation.
According to Canadian science writer and registered massage therapist Paul Ingraham, the current common medical model on pain is adopted from René Descartes — a 17th-century French philosopher — who described pain as a “straightforward signalling system.” When soft tissues are wounded or infected, nerves send a message to the brain about the problem in which the “intensity of the message is directly proportionate to the severity of the injury.” Thus, the brain perceives the message as there is some tissue or structural damage, which causes people to believe the pain is real. This is the model that most physicians and physical therapists address pain.
“Based on this model,” Ingraham wrote, “almost everyone still assumes that any message sent to the brain by a certain kind of nerve will always cause pain.” Ingraham also noted that based on pain research and neuroscience in the past several decades, the Descartian model of pain is oversimplified. The nervous system does not detect pain; rather, it detects a type of stimulus in the tissues, and the brain interprets the information sent from the stimulus. Ultimately, the brain decides how to respond to it and what to make of it. Therefore, biomechanical abnormalities is not always the causality of pain as long as the brain does not perceive them as a threat.
Sometimes pain perception can be changed and pain tolerance can be increased with graded exposure, which is the gradual and progressive adaptation of how the body and the nervous system adapt to environmental and physical stress. This process is based on the SAID principle, which stands for “specific adaptation to imposed demands,” which states that the body will improve and adapt at moving in a specific way and withstanding specific forms of stress.
Todd Hargrove, who is a certified Feldenkrais Practitioner and Rolfer in Seattle, Washington, recently wrote on his website that the body and the nervous system can become less sensitive to a particular form of stress when they are progressively exposed to it. This means that new movement patterns that may cause stress should be progressed with “the right dosage and timing in a way that makes them less painful.” The process can happen by causing a change in the structure of the body or changing the way the nervous system’s threat perception to the body.
“If pain is the result of some form of tissue damage to a muscle, tendon, ligament or joint capsule, exercise might improve this in several ways,” Hargrove said in an online interview. “Improved muscle strength could alter the mechanics in a way that removes mechanical stress from the damaged tissue and allows it to heal. Exercise can also strengthen ligaments and tendons and make them more resistant to stress. Or, stress to the damaged tissue will encourage healing processes that may accelerate healing. For example, eccentric exercise is a common way to treat tendinopathies, and the logic is that eccentric exercise causes micro-damage to the tendon which stimulates healing processes.”
Graded exposure should provide enough stimulation to adapt, but never enough “to cause injury or prevent healing,” Hargrove noted. For example, if a runner experiences minor pain in a knee after running a mile, and the pain happens only during the mile run, then the distance and running intensity should be reduced. With enough recovery between running sessions, the runner gradually increases the distance back to a mile — or more — as long as the pain does not get worse. During the graded exposure process, the stress of running should trigger enough stimulus for the tissues to adapt and heal while building up pain tolerance. However, it is possible that the tissues do not adapt much to the stress, yet the nervous system perceives the movement as less threatened, which reduces the perception of pain.
While graded exposure may seem very promising in reducing pain, current medical literature reviews showed minor benefits compared to standard intervention. In a review published in the June 2010 issue of Physical Therapy, researchers examined 15 trials with more than 1,650 subjects who have chronic low back pain for over six weeks. Based on the available evidence, they concluded that short-term and intermediate-term graded exposure “is slightly more effective than a minimal intervention,” but they are not more effective than other forms of exercise for chronic low back pain. They also commented the trials were low quality because of the different variables and inconsistencies, such as “differences in the implementation of the interventions” and “the heterogeneity of the studies.”
“A program for graded exposure can offer the nervous system new information about a movement that might cause a change in perception,” wrote Hargrove. If there is a way to perform a painful movement pattern at an intensity that is low enough so that it does not hurt, then the feedback tells the nervous system that it is safe to move. With enough exposure to the same stress, the nervous system could perceive zero threat from the movement. This process is very similar to how some psychologists treat anxiety and phobias.
Although using graded exposure can change pain perception with adaptation, there are also other ways to decrease pain sensitivity. “Seek comfort. Be a hedonist,” wrote Ingraham. Creating a safe and pleasurable environment with positive inputs to the nervous system can decrease pain. As long as the brain “thinks” it is safe, then pain is more likely to decrease.
By Nick Ng