The purpose of this study is to evaluate the relationship between psychosocial factors, muscle performance and treatment response in individuals undergoing an exercise-based physical therapy (EBPT) programme for chronic low back pain (CLBP).

A secondary analysis of a prospectively collected clinical registry involving participants with CLBP enrolled in an 8–10-week EBPT programme. Participants completed psychosocial questionnaires before starting EBPT for CLBP. Lumbar extensor muscle performance was assessed using an isokinetic dynamometer, which recorded absolute and age and sex adjusted torque. Differences in muscle performance (absolute and adjusted) were calculated and regressed against psychosocial factors and clinical outcomes.

Absolute and adjusted torque increased with treatment (33.33% and 82.84% respectively, p0.20).

Individuals with CLBP demonstrated improved muscle performance and clinical outcomes after EBPT, though these improvements were independent of each other. Better absolute lumbar extensor muscle performance correlated with higher pain self-efficacy, and greater treatment response corresponded with lower fear-avoidance. These data suggest that pain coping strategies and addressing fear avoidance through educational and exposure-based interventions may be a target for modifying muscle performance in CLBP.