Do Different Arousal Levels Affect Pressure Pain Thresholds?

This study examines whether emotional arousal level alone, while maintaining positive emotional valence, can influence pressure pain thresholds (PPTs) in healthy adults. Pain perception is closely linked to emotional processes, and prior research indicates that emotional valence affects PPTs. However, the specific role of arousal level remains unclear. The study aims to isolate arousal by comparing high arousal positive emotion (humor) with low arousal positive emotion (pleasant video), and a no emotion control condition. A total of 120 healthy participants will be randomly assigned to one of three groups: (1) humor induction (high valence, moderate-high arousal), (2) pleasant emotion induction (high valence, low arousal), or (3) mind wandering control. All participants will first view a neutral baseline video to standardize mood. PPTs will be measured bilaterally at the m. trapezius and m. tibialis anterior using a Somedic algometer (1 cm² probe, 30 kPa/s application rate). Three consecutive PPT measurements per site will be averaged. After the emotional induction (2:30 minutes), PPTs will be reassessed at all four sites. Emotional responses will be validated using the Self Assessment Manikin (SAM) scale to measure valence and arousal. The humor video has been validated in earlier studies, whereas the pleasant low arousal video will be validated in a pre study. Inclusion criteria are age ≥18 and fluency in Swedish; exclusion criteria include pain during testing and known neurological disease. The primary objective is to determine whether high arousal with positive valence increases PPTs (hypoalgesia) and whether low arousal with positive valence decreases PPTs (sensitization). Statistical analyses include repeated measures t tests (Bonferroni corrected) and mixed model ANOVA. Nonparametric tests will be used if PPT distributions deviate from normality.