Comparison of the effects of therapeutic exercise with either an educational booklet or vitamin-D3 supplement in the management of chronic low back pain: study protocol for an assessor blinded multicenter randomized clinical trial.

Background: Chronic low back pain (CLBP) is a common musculoskeletal disorder that significantly impairs quality of life and is frequently associated with vitamin D deficiency. Therapeutic exercise is a cornerstone of management, yet the optimal adjunct intervention to restore serum vitamin D levels remains uncertain. No prior randomized trial has compared oral vitamin D supplementation with lifestyle education on sun exposure, nutrition, and physical activity, both combined with therapeutic exercise. We hypothesize that therapeutic exercise plus an education booklet (TEB) may be superior to therapeutic exercise plus oral vitamin D supplementation (TED) in reducing pain and disability while improving serum vitamin D levels. Methods: This assessor-blinded, two-arm, multicenter randomized controlled trial (RCT) will be conducted in hospitals and rehabilitation centers in Dhaka city, Bangladesh. Adult participants (18-65 years) with CLBP and confirmed vitamin D deficiency will be recruited and randomized to either TEB or TED groups. Both groups will receive standardized therapeutic exercise protocols. The intervention duration will be 6 months, with assessments at baseline, 2 months, and 6 months. Primary outcomes include pain intensity measured by the Brief Pain Inventory (BPI) and serum 25(OH)D3 levels. Secondary outcomes include disability assessed by the Roland-Morris Disability Questionnaire (RMDQ). Statistical analysis will follow the intention-to-treat principle, using repeated measures ANOVA to compare group differences over time. Discussion: This trial will provide evidence on whether a multidimensional lifestyle-based education approach combined with therapeutic exercise offers greater benefit than vitamin D supplementation with exercise in CLBP patients with vitamin D deficiency. The findings will inform clinical guidelines and support comprehensive management strategies for CLBP, particularly in resource-limited settings. Registration: Clinical Trials Registry India ( CTRI/2022/11/047074).