Contributors to Adherence to Exercise Therapy in Non-Specific Chronic Low Back Pain: A Systematic Review of Qualitative and Quantitative Research.

: Chronic low back pain is the leading global cause of disability, with a growing prevalence and socioeconomic burden. Despite strong evidence supporting exercise therapy (ET) as a primary treatment, adherence rates remain low, compromising outcomes and increasing healthcare costs. Research on contributing factors to adherence to ET in non-specific chronic low back pain (nsCLBP) is limited. This systematic review aimed to reconceptualise contributors to adherence, using a conceptual framework to explore their interrelations and complexity by integrating quantitative and qualitative research. : PubMed, Web of Science and Scopus were searched, followed by a two-phase screening process. Risk of Bias (RoB), certainty assessment and level of evidence were assessed independently. : Eight qualitative and eleven quantitative studies were included, the latter divided into nine RCTs and two cohort studies. Overall, eight included studies showed low RoB, seven showed some concerns, and four presented high RoB. Synthesis identified internal, external, and intervention-related contributing factors. These factors were presented in a conceptual framework figure, highlighting that adherence should not be viewed as a binary concept but rather as a dynamic behaviour shaped by interrelated factors. Moderate-certainty evidence supports the impact of psychosocial factors, healthcare professional (HCP) characteristics, environmental and time-related factors, program design, progression, home-exercise program (HEP), modalities, and follow-up. Low-to-moderate-certainty evidence suggests beliefs, patient-related characteristics, and treatment setting also impact adherence. Low-certainty evidence indicates that feedback, symptoms and impairments, and confidence possibly impact adherence. : This systematic review highlights the complex, context-dependent interplay of factors impacting adherence to ET in individuals with nsCLBP. Overall, these findings underscore the need for personalised, context-sensitive interventions that address the broad spectrum of factors, while future research should focus on validated adherence assessment tools.