The effect of a multimodal exercise program on paraspinal muscle morphology and clinical outcomes in chronic low back pain

Background Multimodal exercise programs do not specifically target lumbar paraspinal musculature, but incorporate aspects of different exercises to have an overall benefit. Objective To investigate the effect of a multimodal exercise program on paraspinal muscle volume and composition, and patient outcomes in individuals with chronic low back pain (CLBP). Methods Thirty-four participants with CLBP either completed a 14-week high-intensity training program (n = 8) including cardiorespiratory and resistance exercises 3 sessions per week or were waitlisted (n = 26). Participants underwent magnetic resonance imaging at baseline and post-intervention to assess paraspinal muscle volume (cm3) and fatty infiltration (% FI) at L3-L4, L4-L5, and L5-S1. Pain, disability, quality of life, pain-related fear (catastrophizing and Kinesiophobia), and anxiety were assessed via validated self-reported questionnaires. Results Mixed-design ANOVA revealed no significant time × group interactions for paraspinal muscle volume and %FI. An exploratory analysis revealed a significant increase in multifidus %FI in the control group at L3-L4, L4-L5, and L5-S1, with a concomitant increase in multifidus volume at L3-L4 and L5-S1. The exercise group had a significant increase in multifidus %FI and volume at L5-S1. Significant time × group interactions for pain, disability, catastrophizing and kinesiophobia, and a main effect of group in physical and mental health were found. Significant correlations were found between changes in patient-reported and functional outcomes with paraspinal muscle morphology. Conclusion Multimodal exercise programs may help prevent LBP-related paraspinal muscle atrophy and %FI, and lead to concomitant improvements in pain, disability and pain-related fear in individuals with CLBP.