How to experimentally induce fear of movement-related pain and measure psychophysiological and behavioral reactions as a proxy - A scoping review.

Fear can significantly increase the experienced pain intensity in individuals with chronic musculoskeletal pain and limit their ability to engage in daily activities. Fear of movement-related pain (FMRP) is commonly assessed via self-report, but research suggests measuring psychophysiological or behavioral parameters as an alternative. The objective of this scoping review was to identify and evaluate existing paradigms to induce FMRP, as well as the psychophysiological, behavioral and neural measurements used for its assessment. Experimental studies, with adult participants (≥18 years, healthy and chronic pain) observing or performing movements, were included if they used a FMRP induction paradigm or measured psychophysiological and behavioral proxies of FMRP. A total of 1883 studies were screened; 34 eligible studies were included. Paradigms inducing FMRP involved anticipated pain paired with movement (via classical or operant conditioning) or elicited pre-existing FMRP through the observation of movements potentially associated with pain. The identified studies employed various psychophysiological and behavioral measures indicating FMRP, such as response latency/duration, decision-making behavior, eyeblink startle response, and autonomic nervous system responses (e.g., skin conductance, heart rate, respiratory rate), as well as neural correlates (fMRI). fMRI studies revealed activation in fear- and pain-processing brain areas that correlated with patient-reported measurements (e.g., amygdala, hippocampus, lateral orbitofrontal cortex). Among the psychophysiological and behavioral measures displaying significant differences between fear-evoking, and neutral conditions, heart rate, respiratory response, skin conductance, and eyeblink-startle response demonstrated the largest effect sizes. In conclusion, physiological reactions can be measured during imagined, observed, or performed movements as a proxy for FMRP. PERSPECTIVE: This review provides an overview of existing paradigms to induce or elicit already conditioned FMRP in participants with chronic pain and in healthy participants. Therefore, the results of this review can inform future research projects that aim to further analyze the learning mechanisms behind and the processing of FMRP at brain level. Furthermore, measuring psychophysiological or behavioral proxies of FMRP can be beneficial not only in research settings, but also in clinical settings, to complement patient-reported outcome measures or to measure the FMRP of people with communicating issues, that are not able to complete a self-reported questionnaire.