Heart Rate Variability in People with Chronic Shoulder Pain Exposed to Passive Visualization of Shoulder Motion Images

Abstract

Persistent shoulder pain can impair the ability to perform daily activities. Some factors such as catastrophizing, self-efficacy and resilience contribute to the maintenance of the fear-avoidance model of pain. Fear related to pain can be accompanied by some emotions. The literature points out that pain and emotion are separate constructs, but they can be shared in neurophysiological processes. Furthermore, pain is an aversive stimulus that triggers physiological responses controlled by the autonomic nervous system (ANS) and emotions are understood by changes in the ANS in response to a salient stimulus. Heart rate variability (HRV) is used to assess modulation in the ANS. People who have a high HRV at rest produce emotional responses appropriate to the context. Some studies evaluated HRV in people with low back pain, neck pain and complex regional pain syndrome and found a decrease in HRV. HRV provides measures that reflect the perception of threat in the environment and may be a way to understand the mechanisms associated with the chronicity of pain in people with chronic shoulder pain. HRV has not been evaluated in people with chronic shoulder pain while passively viewing images that are considered threatening. Aims: (1) to compare HRV in people with chronic pain and asymptomatic controls; (2) to verify whether the level of self-efficacy, resilience, catastrophizing, self-regulation and HRV are predictors of shoulder pain intensity and disability in the 3-month period. Methods: This research is characterized as an observational study of the case-control type (objective 1) and observational of the prospective cohort type (objective 2). We hope to include a minimum total of 68 participants. Inclusion criteria for the shoulder pain group are: chronic shoulder pain, >18 years, pain of at least 3/10 on the Numerical Pain Scale (END) and who have not undergone physical therapy treatment in the last month. Inclusion criteria in the asymptomatic control group are: no clinical diagnosis related to the shoulder complex or upper limb, painful condition and >18 years. Exclusion criteria for both groups are: diagnosis of frozen shoulder, presence of diagnosed tumor, visual impairments that compromise the visualization of images, pregnancy, clinical diagnosis of hypertension and cardiovascular diseases, such as angina and chest pain, history of myocardial infarction, continuous use of medications (for example, antidepressants, anticonvulsants, beta-blockers, corticosteroids and venlafaxine, neurological diseases, smoking and practitioners of high-intensity physical activity (those who practice more than 150 minutes per week of vigorous aerobic activities according to The International Physical Activity Questionnaire - IPAQ). 24 images representing daily activities of the shoulder complex will be used (12 unpleasant and 12 neutral). HRV, pressure pain threshold and END will be evaluated before and after passive visualization of the images. Statistical Analysis: The sample calculation of the pilot sample will be carried out. Descriptive analysis of the data, mixed linear models to test the main and interaction effects between groups with the primary outcome of HRV will be performed. Univariate and Multiple Linear Regression to verify that the levels of self-efficacy, resilience, catastrophizing, self-regulation and HRV are predictors of the pain and disability index after 3 months.