Effects of positive and negative peer modelling versus neutral social interaction before spinal manipulative therapy in adults with chronic non-specific low back pain: protocol for a three-arm randomized controlled trial.

INTRODUCTION: Chronic nonspecific low back pain (CNSLBP) is a leading cause of disability worldwide. Responses to spinal manipulative therapy (SMT) may be influenced by treatment expectations, which can be shaped through observational learning. OBJECTIVES: To compare current pain intensity 60 min after lumbar SMT among positive peer-modeling, neutral social-interaction, and negative peer-modeling conditions in individuals with CNSLBP. METHODS/DESIGN: This single-center, three-arm randomized controlled trial will allocate participants in a 1:1:1 ratio to positive peer modeling, neutral social interaction, or negative peer modeling before receiving the standardized lumbar high-velocity low-amplitude SMT. Assessments will occur at baseline (T0a), immediately after the simulated-patient interaction and before SMT (T0b), 60 min after SMT (T1), and 24 h after SMT (T2). The primary outcome and time point will be current pain intensity measured with the 11-point Numerical Pain Rating Scale (NPRS-11) at T1. Secondary outcomes will include pain at T2, stress, kinesiophobia, disability, pressure pain threshold, tissue temperature, lumbar range of motion, expectation fulfillment, and treatment satisfaction. Empathy and inflammatory biomarkers will be evaluated as exploratory outcomes. DISCUSSION: The trial will analyze whether the three simulated-patient conditions produce different short-term responses to identical SMT, without determining the effect of simulated-patient exposure compared with no exposure. CLINICAL TRIAL REGISTRATION: www.clinicaltrials.gov identifier is NCT07507604.