Cortical-multifidus paired associative stimulation for improving motor function in patients with chronic low back pain: study protocol for a randomised controlled trial.

INTRODUCTION: Chronic low back pain (CLBP) is characterised by multifaceted pathophysiology involving both central sensitisation and peripheral dysfunction. Conventional therapies often fail to address this complexity due to their unidimensional targets. Paired associative stimulation (PAS), a dual-target neuromodulatory approach that combines central and peripheral interventions, has demonstrated efficacy in enhancing motor recovery post-stroke by synchronously inducing corticospinal plasticity and peripheral neuromuscular adaptation. Building on this paradigm, we propose a novel combined primary motor cortex (M1) and multifidus muscle stimulation protocol. The intervention pairs transcranial magnetic stimulation over M1 with peripheral magnetic stimulation targeting the multifidus muscle, hypothesising that temporally coordinated central and peripheral stimulation will synergistically enhance the corticospinal drive to the lumbar spine and restore multifidus neuromuscular control, thereby alleviating pain and improving functional capacity in CLBP. METHODS AND ANALYSIS: This study will enrol 82 individuals diagnosed with CLBP between 18 and 65 years of age. Study participants will undergo randomisation into two parallel groups: the experimental arm receiving active PAS therapy (n=41) and the control arm receiving sham PAS treatment (n=41). The intervention protocol consists of 20 treatment sessions delivered across a 4-week timeframe, with participants attending five sessions weekly. Assessment time points are scheduled at study entry (baseline) and 4, 8 and 12 weeks following intervention initiation. The study's primary outcome is the Oswestry Disability Index (ODI). Secondary outcomes encompass the Visual Analog Scale (VAS), Short-form McGill Pain Questionnaire (SF-MPQ), Short Form 36 Health Survey (SF-36), Pain Catastrophizing Scale (PCS), and functional magnetic resonance imaging (fMRI). Data analysis will adhere to the intention-to-treat methodology. Between-group comparisons across temporal measurement points will employ mixed-effects modelling approaches. ETHICS AND DISSEMINATION: Ethical approval for the research protocol was obtained from the Ethics Committee of Guanghua Hospital Affiliated to Shanghai University of Traditional Chinese Medicine (approval number: 2025-K-45), with trial registration completed in the China Clinical Trial Registry on 27 April 2025. On study completion, findings will be prepared for submission to peer-reviewed academic publications. TRIAL REGISTRATION NUMBER: ChiCTR2500101574.