Objectives: We sought to investigate emotional reactivity by measuring HRV and pressure pain sensitivity during a passive visualization task in participants with chronic low back pain (CLBP).
Methods: This case-control study was composed of 47 participants with CLBP and 47 asymptomatic participants. Both groups were submitted to a passive visualization task using 27 pictures from PHODA (Photograph Series of Daily Activities). HRV frequency domains were measured before, during, and after the task. Pressure pain threshold (PPT) and pain intensity were also measured before and after the task.
Results: The adjusted mean difference was statistically significant for HRV frequency domains during the visualization task, including low frequency (-5.92; 95%CI=-9.60 to -2.23), high frequency (-0.71; 95%CI=-1.02 to -0.39), and low frequency/high frequency ratio (8.82; 95%CI=5.19 to 12.45). PPT decreased after the task in the low back pain group in all body sites, and pain intensity increased (-0.8; 95% CI=-1.16 to -0.39).
Discussion: Aversive environmental stimuli, such as visual cues, may generate defensive physiological reactions. Heart rate variability (HRV) can provide an available measure that reflects the perceptions of threat and safety in the environment. Participants with chronic low back pain presented changes in sympathovagal balance during passive visualization of pictures of daily activities, higher pain sensitivity, and high pain intensity when they are exposed to a passive visualization task using pictures of daily living that may arouse fears of harm.
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