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Pain Expression and Activity Tolerance Affect Chronic Pain

It's long been suspected that psychological issues can have a significant impact on chronic pain and how people perceive chronic pain. In the early days of human development, it's thought that pain was a survival mechanism, an internal alarm of sorts. In order to not feel pain, humans would learn to adapt to their surroundings by not doing things that would cause pain or increase or intensify pain. This led to fewer injuries or less severe ones. However, this theory isn't one that has been proven and it does have its flaws. New research is suggesting that if we are ever to be able to effectively treat chronic pain, we need to better understand the psychological/physical connection.

The authors of this article examined how pain catastrophizing and pain-related fear were connected to how people would protect themselves from developing more pain. This self-protection could be in the form of avoidance or "guarding" the painful area to prevent any possibility of more pain. The researchers predicted that the fear of movement or re-injury would be associated with pain protective behaviors and a reduction in physical activity and tolerance.

The researchers recruited 72 patients, who were an average age of 45 years) who had chronic musculoskeletal (bone, joint and/or muscle) pain. To participate, the patients had to have back or neck pain for at least three months and be away from work at the time of the evaluation for the study. The researchers measured the patients' complaints of pain using the McGill Pain Questionnaire to measure how severe the pain was. This included a Pain Rating Index (MPQ-PRI). To see if patients were catastrophizing their pain, they used the Pain Catastrophizing Scale (PCS), which uses a scale of zero to four, with zero meaning never and four, all the time. Because many patients are fearful of pain or re-injury, the researchers chose to use the Tampa Scale for Kinesophobia (TSK) to measure this. The scale goes from one to four, with one being "strongly disagree" and four being "strongly agree."

After the questionnaire were completed, the study participants were asked to lift different containers filled with sand made up to various weights. The tolerance of lifting was measured, as was the duration of the lift and the technique. If the patient experienced any pain, this was noted. The lifts were also videotaped for later review.

The researchers coded the behaviors of the patients as they picked up the objects. They looked for pain behaviors that were classified as either communicative or protective. Communicative behaviors included facial expressions and verbal utterances (grunts, moans, etc). Protective behaviors were ones that were meant to physically protect the patient against pain, such as guarding the area with a hand or rubbing it.

In analyzing the data, the researchers found that there was an association between catastrophizing and protective pain behaviors at a rate slightly higher than the association between catastrophizing and communicative behaviors. The results of the questionnaires and scales showed that women complained more than men about pain intensity and they also had higher rates over all on the Pain Catastrophizing Scale. Women also appeared to show more communicative and protective pain behaviors.

When interpreting data and trying to understand what the findings mean, it must be considered if protective behaviors are also communicative - using nonverbal communication and that these protective behaviors, such as rubbing the painful area, may be more intentional than verbal behaviors, such as grunting or moaning. There also may be a cultural component; some cultures are more verbal about pain while others are more stoic and are determined to not show any indication of discomfort. So, since there may be a more conscious decision to the behaviors than thought, this is not cut and dry, making it more complicated for the researchers to understand what is going on.

Despite the issues that aren't yet understood, the researchers concluded that the pain catastrophizing was a related directly to both communicative and protective pain behaviors. Fear of pain, on the other hand, was related to physical tolerance and protective behaviors. Fear of pain did not affect pain severity though. It is felt that the study "provides additional evidence for the functional distinctiveness of pain expression and activity intolerance."

References: Pascal Thibault, et al. Psychological predictors of pain expression and activity intolerance in chronic pain patients. In . Sept 2008. Vol. 139. No 1.

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