Non-specific low back pain (NSLBP) is one of the leading causes of disability worldwide. Emerging evidence suggests that altered diaphragmatic function may be associated with lumbar pain, impaired trunk stabilisation and functional disability. Manual diaphragmatic techniques have been proposed as an intervention to modulate diaphragmatic tension, mobility and neuromyofascial relationships; however, their effectiveness has not yet been synthesised using rigorous systematic review methods.

This protocol follows Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols guidance and has been prospectively registered in PROSPERO. Randomised controlled trials evaluating manual techniques specifically applied to the diaphragm in adults with NSLBP will be eligible. The primary outcomes will include pain intensity and functional disability; secondary outcomes will include lumbar mobility, respiratory function, quality of life and adverse events. Searches will be performed in PubMed/MEDLINE, Cochrane CENTRAL, PEDro, CINAHL, Scopus, Embase and clinical trial registries without language or date restrictions. Two reviewers will independently perform study selection, data extraction and risk-of-bias (RoB) assessment using the Cochrane RoB 2 tool. Where appropriate, a random-effects meta-analysis will be conducted; the certainty of evidence will be evaluated using the Grading of Recommendations, Assessment, Development and Evaluation approach. Substantial clinical and methodological heterogeneity is anticipated across trials, which may limit the feasibility of quantitative data pooling.

As this study uses data from previously published trials, ethical approval is not required. Findings will be disseminated through peer-reviewed publication, conference presentations and a plain-language summary for clinical stakeholders.

CRD420251172616.