Testing Biological and Psychological Pathways of Emotion Regulation as a Primary Mechanism of Action in Yoga Interventions for Chronic Low Back Pain: Protocol for a Randomized Controlled Trial

Interventions that promote adaptive emotion regulation (ER) skills reduce pain in patients with chronic pain; however, whether the effects of yoga practice on chronic low back pain (CLBP) are due to improvements in ER remains to be examined. This study will test whether the effects of yoga on CLBP (improved pain severity and interference) are mediated by improved ER, the extent to which effects are related to specific aspects of ER, and the role of pain sensitization as a mediator or moderator of effects. In this study, pain sensitization will be assessed by quantitative sensory testing and gene expression profiles to examine whether pain sensitization moderates yoga's effects on pain or whether yoga and ER abilities reduce pain sensitization, leading to decreased pain severity and interference. For this 2-arm parallel group blinded randomized controlled trial, we will enroll 204 adults with CLBP who will be randomized to receive the yoga (n=102) or a control stretching and strengthening (n=102) intervention, which are delivered via web-based synchronous biweekly 75-minute sessions over 12 weeks. Participants are encouraged to practice postures or exercises for 25 minutes on other days using accessible prerecorded practice videos that are sent to participants digitally. Participants will be assessed at 5 time points: baseline, midintervention (6 weeks), postintervention (12 weeks), and 3- and 6-month follow-ups. Assessments of ER, pain severity and interference, pain sensitivity including somatosensory and gene expression profiles, and physical strength and flexibility will be conducted at each visit. The fidelity of the interventions is assessed using a manualized checklist to evaluate recorded group sessions to ensure consistent instructor delivery. The primary outcome will be the mean change in pain severity as measured by the Brief Pain Inventory-Short Form at 12 weeks. The primary mechanism of action is ER measured by change in the Difficulties in Emotion Regulation Scale total score. Secondary outcomes include pain sensitivity, physical strength and flexibility, pain interference, and quality of life. A mediation path analysis and series of moderated mediation path analyses will be conducted to test the study hypotheses. As of January 2024, we have enrolled 138 participants. We expect the study to be completed by May 2025. The study will provide important data for evaluating whether improvements in ER are responsible for reduced pain perception and p