RESUMEN
BACKGROUND: Low back pain is a very common symptom frequently characterized as a biopsychosocial problem. This study aims to investigate the effectiveness of education to keep the abdomen relaxed versus contracted during Pilates exercises in patients with primary chronic low back pain. METHODS: Two-group randomised controlled trial with allocation of parallel groups and intention-to-treat-analysis. This study will be conducted in Lavras, MG, Brazil. A total of 152 participants will be randomised into two groups that will be treated with Pilates exercises for 12 weeks (twice a week for 60 minutes). Recruitment began in May 2022. The control group will receive guidance on the specific activation of the center of strength (the powerhouse), while the experimental group will receive guidance to perform the exercises in a relaxed and smooth way. Primary outcomes will be pain intensity (Numeric Pain Rating Scale) and disability (Rolland-Morris Questionnaire) 12 weeks post randomisation. Secondary outcomes will be global improvement (Perception of Global Effect Scale) and specific functionality (Patient-specific Functional Scale). The outcomes will be analyzed using repeated-measure linear mixed models. The assessors were not considered blinded because the participants were not blinded, and outcomes were self-reported. DISCUSSION: The findings of this study will help in clinical decision-making concerning the need to demand abdominal contraction during the exercises, understanding if it's a fundamental component for the effectiveness of the Pilates method for this population. TRIAL REGISTRATION: This trial was prospectively registered in the Clinical Trials (NCT05336500) in April 2022.