The purpose of the present research was to examine the influence of communication goals and physical demands on the expression of communicative (e.g., facial grimaces) and protective (e.g., guarding) pain behaviors. Participants with musculoskeletal conditions (N=50) were asked to lift a series of weights under two communication goal conditions. In one condition, participants were asked to estimate the weight of the object they lifted. In a second condition, participants were asked to rate their pain while lifting the same objects. The display of communicative pain behaviors varied as a function of the communication goal manipulation; participants displayed more communicative pain behavior when asked to rate their pain while lifting objects than when they estimated the weight of the object. Protective pain behaviors varied with the physical demands of the task, but not as a function of the communication goals manipulation. Pain ratings and self-reported disability were significantly correlated with protective pain behaviors but not with communicative pain behaviors. The results of this study support the functional distinctiveness of different forms of pain behavior. Findings are discussed in terms of evolutionary and learning theory models of pain behavior. Clinical implications of the findings are addressed.

This study examined the role of pain catastrophizing, fear of movement and depression as determinants of repetition-induced summation of activity-related pain. The sample consisted of 90 (44 women and 46 men) work-disabled individuals with chronic low back pain. Participants were asked to lift a series of 18 canisters that varied according to weight (2.9kg, 3.4kg, 3.9kg) and distance from the body. The canisters were arranged in a 3x6 matrix and the weights were distributed such that each 'column' of three canisters was equated in terms of physical demands. Participants rated their pain after each lift, and in a separate trial, estimated the weight of each canister. Mean activity-related pain ratings were computed for each Column of the task. An index of repetition-induced summation of pain was derived as the change in pain ratings across the six 'columns' of the task. Pain catastrophizing, fear of movement and depression were significantly correlated with condition-related pain (e.g., MPQ) and activity-related pain ratings. Women rated their pain as more intense than men, and estimated weights to be greater than men. A repetition-induced summation of pain effect was observed where pain ratings increased as participants lifted successive canisters. Fear of movement, but not pain catastrophizing or depression, was associated with greater repetition-induced summation of pain. The findings point to possible neurophysiological mechanisms that could help explain why fear of pain is a robust predictor of pain-related disability. Mechanisms of repetition-induced summation of activity-related pain are discussed.

Recent research suggests that communicative and protective pain behaviors represent functionally distinct subsystems of behavior associated with pain. The present research examined whether components of pain experience such as pain severity, catastrophizing and fear of pain were differentially associated with communicative and protective pain behaviors. It was predicted that pain severity would be associated with decreased physical tolerance and heightened expression of pain behavior. It was also predicted that pain catastrophizing would be preferentially associated with communicative pain behaviors, and fear of pain would be preferentially associated with protective pain behaviors and decreased physical tolerance. To test these predictions, work-disabled patients with musculoskeletal pain conditions (N=72) were filmed as they participated in a simulated occupational lifting task. Multiple regressions revealed that pain severity was uniquely associated with decreased physical tolerance and increased expression of protective pain behaviors. Pain catastrophizing was uniquely associated with the expression of both communicative and protective pain behaviors. Fear of pain was associated with physical tolerance and protective pain behaviors but not when controlling for pain severity. This study provides additional evidence for the functional distinctiveness of different types of pain expression and provides preliminary evidence for the functional distinctiveness of pain expression and activity intolerance. Discussion addresses the processes by which psychological factors might influence the display of different types of pain behaviors. Discussion also addresses how different types of interventions might be required to specifically target the sensory and behavioral dimensions of the pain system.

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