Reduced lumbar proprioception may be related to impaired multifidus quality in people with low back pain

Abstract

Background Low back pain (LBP) is the leading cause of disability worldwide. Altered proprioceptive integration during stance may contribute to LBP, but its relation to structural and qualitative properties of the lumbar multifidus remains unclear. This study investigated (1) differences in proprioceptive weighting during standing, and multifidus size and quality, between individuals with and without LBP, and (2) associations between proprioceptive use and multifidus structure.

Methods Thirty-six LBP participants and thirty-two controls underwent postural testing with muscle vibration applied to ankle and lumbar muscles while standing on stable and unstable support. Center of pressure responses were measured with a force plate (Kistler). Multifidus volume (L2–L5), cross-sectional area, and echo-intensity (L5) were obtained using three-dimensional freehand ultrasound (SonixTouch Q+; Optitrack V120:Trio). Non-parametric tests assessed group differences; Spearman correlations were computed with Bonferroni correction (p < 0.013).

Results Compared with controls, individuals with LBP demonstrated greater ankle reliance (p = 0.019), reduced lumbar proprioceptive contribution on unstable surfaces (p = 0.040), and higher multifidus echo-intensity (p < 0.002), while multifidus size did not differ. After correction, only center of pressure displacement during lumbar vibration on stable ground showed a modest negative correlation with multifidus echo-intensity (r = –0.38, p = 0.015).

Conclusion People with LBP display altered proprioceptive strategies, marked by insufficient up-weighting of lumbar input under challenging balance conditions. This may be partly linked to reduced multifidus muscle quality, rather than muscle size. However, the observed association was small and limited to stable stance. Further studies should clarify whether increased echo-intensity reflects fatty or connective tissue infiltration and its potential role in sensorimotor control impairments in LBP.