Is resistance training with external loads superior to unloaded exercise in the management of chronic low back pain? A systematic review and meta-analysis

Introduction: Chronic non-specific low back pain is a leading cause of disability worldwide. While resistance training using external loads is common in rehabilitation, its added value over unloaded exercise remains uncertain, particularly across physical and psychological variables. Method: This systematic review and meta-analysis, registered on PROSPERO (CRD42022366975), included randomized controlled trials comparing externally loaded resistance training to unloaded exercise in adults with chronic non-specific low back pain. Primary outcomes were pain intensity and disability. Secondary outcomes included back muscle endurance, maximal strength, fear-avoidance beliefs, and pain catastrophizing. Random-effects meta-analyses were conducted, stratified by follow-up duration. Results: Thirteen randomized trials (778 participants) were included. At follow-up periods beyond seven weeks, externally loaded resistance training showed a small but statistically significant reduction in pain compared to unloaded exercise (mean difference = –0.52 on a 0-10 scale; 95% confidence interval [–0.92, –0.08]). No significant differences were found at short-term or post-washout follow-ups. Effects on disability were inconsistent and highly variable. Resistance training was associated with improvements in back muscle endurance and suggested a possible effect on long-term maximal strength, although wide prediction intervals prevent definitive conclusions. No meaningful differences were found for psychological variables, and pain catastrophizing was assessed in only one trial, limiting conclusions. Conclusion: Externally loaded resistance training is safe and feasible for chronic non-specific low back pain, but its effects on pain, disability and psychosocial outcomes are comparable to unloaded exercise. In line with the multifactorial nature of chronic pain, improvements appear driven more by exposure, adherence and therapeutic context than by load intensity alone. Exercise prescription should therefore remain individualized and embedded within a biopsychosocial framework.