Human Studies

Up to 20% of people who undergo total knee replacement surgery have ongoing pain and discomfort. The aim of this study was to understand what role the concepts of embodiment (of both having a body and experiencing the world through one's body) and incorporation (integrating something into one's body) might have in understanding experiences of pain and discomfort after total knee replacement.

Low back pain (LBP) is a leading cause of disability. However, the processes contributing to disability are not well understood. Therefore, this study 1) empirically derived LBP subgroups and 2) validated these subgroups using walking performance, pain, and disability measures. Seventy adults with LBP underwent testing for a priori determined sensory (temporal summation; conditioned pain modulation), psychological (positive coping; negative coping), and motor (trunk extensor muscle activation during forward bending and walking) measures. A hierarchical cluster analysis determined subgroups that were then validated using walking (walking speed; Timed Up and Go (TUG); Timed Up and Go-Cognitive (TUG-Cog); obstacle negotiation) and clinical (Brief Pain Inventory; Oswestry Disability Index; low back pressure pain threshold) measures. Two subgroups were derived: 1) a "Maladaptive" subgroup (n=21) characterized by low positive coping, high negative coping, low pain modulation, and atypical trunk extensor activation; and 2) an "Adaptive" subgroup (n=49) characterized by high positive coping, low negative coping, high pain modulation, and typical trunk extensor activation. There were subgroup differences on 7 out of 12 validation measures. The Maladaptive subgroup had reduced walking performance (slower self-selected walking speed, TUG completion, and obstacle approach and crossing speed) and worse clinical presentation (higher pain intensity, pain interference, and disability) (moderate to large effect sizes; p's<0.05). Findings support the construct validity of this multidimensional subgrouping approach. Longitudinal studies are needed to determine if the Maladaptive subgroup is predictive of poor outcomes, such as pain chronicity or persistent disability.

Self-report is the gold standard for measuring pain. However, decisions about pain can vary substantially within and between individuals. We measured whether self-reported pain is accompanied by metacognition and variations in confidence, similar to perceptual decision-making in other modalities. Eighty healthy volunteers underwent acute thermal pain and provided pain ratings followed by confidence judgments on continuous visual analogue scales. We investigated whether eye fixations and reaction time during pain rating might serve as implicit markers of confidence. Confidence varied across trials and increased confidence was associated with faster pain rating reaction times. The association between confidence and fixations varied across individuals as a function of the reliability of individuals' association between temperature and pain. Taken together, this work indicates that individuals can provide metacognitive judgments of pain and extends research on confidence in perceptual decision-making to pain.

The purpose of this study was to compare disability in people with HIV and peripheral neuropathy with those without neuropathy and explore how neuropathy and other relevant factors are associated with disability.

Total knee replacement (TKR) normally provides improvements of physical function and reduces pain. However, approximately 20% of the patients report chronic postoperative knee pain. The aims of the present study were to assess the pain, physical function, and physiological characteristics 5 years after TKR surgery.

School-based educational programs have shown positive changes in health-related behaviors among adolescents. The aim of this study was to analyze the changes in pain-related knowledge among adolescents and in the use of positive responses to their peers' pain behaviors after watching a brief educational video.