Study Design. A prospective analysis of the relative influence of pain-specific and performance-specific cognitive variables on lifting tasks using empirically derived measures.
Objectives. To determine the relative contributions of self efficacy expectancies of lifting performance, perceptions of pain control, and anxiety on actual lifting performance.
Summary of Background Information. Although patients' pain beliefs play an important role in the expression of low back pain, there is little research on the influence of performance-specific cognitions on spinal function. This study extended the scope of recent research, with findings indicating that patients with a stronger functional self efficacy expectancy-the belief that one can perform essential work tasks successfully-achieve higher levels of function than those with a low functional self efficacy expectancy. Moreover, as a performance-specific variable, functional self efficacy expectancy was hypothesized to be a better predictor of lifting than pain-specific cognitions, which presumably influence function in an indirect manner, if at all.
Methods. Before undergoing a standardized, graded lifting assessment, 100 work-disabled patients with chronic back pain rated their confidence to perform load-lifting tasks essential to their job (functional self efficacy expectancy), their ability to control and decrease pain, and psychological distress.
Results. Multiple regression analyses found that functional self efficacy expectancy accurately predicted lifting. It was found to be a better predictor of lifting tasks than either of the perceived pain control measures or psychological distress.
Conclusion. Data suggest that what patients believed they could achieve accurately determined their actual spinal function, independent of their sense of control over pain or their distress. Approaches to low back disorders emphasizing perceived pain control as a central cognitive determinant of disability were unsupported.
Chronic low back disorders are complex problems with distinct neurophysiologic, cognitive, and emotional components. The multifactorial nature of chronic low back pain means that it cannot be accurately understood as simply the product of noxious peripheral input. 34 Moreover, because low back pain is a perceptual, interpretive state, it is subject to particularly strong cognitive influences. Patients who develop chronic problems appraise and process pain-stimuli differently than do healthy controls. 10 These patients attend selectively to pain cues, mislabel bodily sensations, inaccurately predict the probability of painful events, and have distorted memories for pain episodes. Pain patients' cognitive processes not only deviate from the more logical cognitive functioning of their nonclinical counterparts, but significantly influence pain intensity and responses to medical, surgical, and nonpharmacologic treatments. 30,12
Because negatively skewed cognitions play such an important role in the expression of chronic low back syndromes, researchers have sought to specify the ideational content of pain cognitions among patients with chronic pain. This research has found that the thinking patterns of patients with chronic pain are dominated by a lack of perceived control over painful events. 10 Patient beliefs of pain control appear to influence the course of pain disorders in distinct ways. Physiologically, perceptions of pain control influence levels of catecholamines and endogenous opioids which, in turn, affect perceived pain and related distress. 4 Psychologically, a sense of uncontrollability over pain augments perception of pain intensity, demoralization, and negative emotional reaction to nociceptive stimulation. 10 Patients doubting their ability to control pain see themselves at the mercy of pain, view their environment as fraught with danger and uncertainty, and selectively focus on the most catastrophic outcomes of negative life events. Not surprisingly, weak convictions of pain self-control are associated with physical disability. 15
Consistent with cognitive formulations emphasizing the importance of perceived pain controllability are studies showing that patients who believe they can control their pain are better able to tolerate and control their pain than those who doubt their pain self-control. 5 Doubts about pain control are associated with increased pain, psychological distress, and avoidance of painful activities. 8,19,20
These data have lead researchers to reason that patient beliefs about pain control mediate the association between pain intensity and patient adjustment. 14 Thus, the perceived pain control literature implies a causal relationship between pain intensity and disability. Individuals with a strong belief in their ability to control pain are seen as better equipped to endure more painful physical activities and are thought to strive toward higher levels of physical function without giving up.5 The stronger a patient's belief in his or her ability to withstand pain, the higher the pain tolerance and the less dysfunction pain produces.5
Although intuitive, the notion that pain reliably produces or motivates disability has received more conventional acceptance than empirical support. There is a sizable body of evidence indicating that pain is not related to function in a linear fashion. 25 Patients with similar intensities of pain often function at very different levels. Some individuals with mild pain evidence significant disability, whereas some with high pain demonstrate little disability. The inconsistent correspondence between pain and disability means that pain cannot be considered a reliable motivator of disability. On scientific grounds, a causal association between pain and function requires a stronger correlation between pain and function than the medical literature has established to date. Moreover, if pain does not necessarily cause function, then it is difficult to envision how pain-specific cognitive processes-whose importance is largely based on their pain modulatory properties-have any more of a reliable influence on function than pain itself.
An alternative approach comes from the functional self efficacy (FSE) theory 18. This theory draws from social learning theory (SLT), which is currently the prevailing conceptual framework used in health behavior and health promotion research. In the SLT, cognitive processes (beliefs, attitudes), behavior, and environmental are seen as influencing one another to shape health behaviors. The correlation among these variables is largely determined by a person's self efficacy expectations (i.e., belief in one's competence or ability). The self-efficacy theory has been applied effectively to a variety of health problems, including smoking cessation, obesity, cardiovascular disease, alcoholism, and chronic pain. In self efficacy investigations of patients with chronic pain, the manner in which a patient's confidence regarding his or her ability to control or tolerate pain contributes to pain perception has been examined. In contrast, self efficacy expectations in the FSE theory involve patients' perceived judgments of their ability to execute performance tasks successfully. The FSE theory attaches greater importance to patients' perceptions of physical task performance than perceptions of pain controllability because: 1) functional disability appears to play a more significant role in the transition from acute to chronic pain than pain intensity 3; 2) physical performance, not pain per se, is the defining feature of clinical low back pain disorders 14,24; and 3) performance-specific efficacy beliefs in particular play influential roles in determining task performance across diverse areas, including academic achievement, occupational performance, physical exercise, and athletic accomplishment. 6 Because the FSE approach focuses on performance-specific (vs. pain-specific) motivational processes underlying spinal function, it appears better suited to account for the direct link between self efficacy expectancies and physical performance that is addressed only indirectly by the pain self efficacy approach. Functional self efficacy presumably regulates spinal function by influencing whether one attempts tasks, how much effort one invests in their completion, how long one will persist in the face of obstacles, and ultimately how successful one is in performing tasks. 18,24 Those with elevated FSE reach higher levels of physical performance, because they invest more effort and persistence in task demands. Unlike patients with back pain and a strong sense of FSE, those with a low FSE see little point in attempting spine-intensive tasks and doubt their performance capabilities. If they make an attempt, they give up easily in the face of discouraging results and setbacks.
Empirical support for the predictive superiority of FSE (a performance-specific cognition) over pain-specific cognitions comes from a recent study that compared FSE and pain expectancies as predictors of spinal function. 18 Results showed that FSE accurately predicted function when anticipatory pain and injury were held constant. In contrast, expectancies about pain and reinjury lost their predicative value when FSE was kept constant. The findings suggested that pain-specific cognitions were not independent causes of disability, but dependent effects of patients' judgments of their performance capabilities (FSE).
A similar pattern of results was obtained by Finnish researchers. Estalander et al 9 found that the judgments by patients with low back pain of their functional abilities predicted patient performance on an isokinetic trunk muscle test above and beyond the influence of the anthropometric measures of body weight and age. Unfortunately, the extent to which the association between performance judgments and function is a correlated coeffect of an alternative psychosocial variable such as anxiety was not evaluated. Given that anxiety frequently accompanies chronic pain disorders and is characterized at a cognitive level by negative self-evaluation of performance capabilities, it is possible that patients' judgments regarding their performance capabilities owed their predictive power to anxiety.
The purpose of this study was to explore the relative influence of FSE, perceived pain control, and anxiety on standardized measures of function. Two experimental hypotheses were tested. The first hypothesis, drawn from FSE theory, emphasizes patient expectations of performance capabilities. If, as the FSE theory suggests, disability stems more from patients' beliefs of their performance capabilities than from their convictions of pain control, FSE expectancies should be more accurate and powerful predictors of spinal function than patients' perceptions of ability to control or decrease pain or to decrease anxiety levels. The second hypothesis, drawn from current pain-control theories, predicted that perceived pain control would influence function more strongly. Accordingly, patients with stronger beliefs in their ability to control pain would endure the painful physical demands of spine-intensive tasks and, as a result, achieve higher levels of function. Conversely, individuals doubting their ability to control painful events would perform at lower levels, because they would have difficulty tolerating the pain associated with these activities. To test these hypotheses, patients with chronic low back pain rated their FSE and perceived control over pain before their performance of two behaviorally measured tasks of load lifting was tested.