Virtual McKenzie Exercises and Centralization of Pain: A Pilot Study

Overview

Low back pain (LBP) is frequently managed in physical therapy using the McKenzie method, in which a patient's directional preference-most commonly extension-is used to guide treatment. Extension-based interventions are associated with symptom improvement and centralization in many individuals with LBP. At the same time, research in pain neuroscience has shown that people with LBP may have altered cortical representations of the low back, which may contribute to pain and disability. For patients who experience high pain levels or significant fear of movement, active directional preference exercises may be difficult to perform. Motor imagery, the mental simulation of movement without physical execution, has been shown to activate brain regions involved in movement and may help modify altered cortical representations. Preliminary research has suggested that virtual or imagery-based McKenzie extension exercises may improve pain and movement-related outcomes. This exploratory study aims to evaluate the immediate effects of a brief motor imagery-based extension protocol in adults with LBP who demonstrate a directional preference for extension. The study will assess changes in pain intensity, disability, fear-avoidance, pain catastrophization, lumbar flexion, straight leg raise, pain distribution, and symptom centralization following a single motor imagery session.

Background and Rationale: Low back pain (LBP) is the most common musculoskeletal condition treated in outpatient physical therapy, accounting for approximately 25-40% of patient visits. Directional preference, a key element of the McKenzie method, is widely used in the management of LBP. This approach assesses how a patient's symptoms respond to repeated or sustained directional movements-most commonly flexion or extension-and integrates the direction that reduces or centralizes symptoms into the treatment plan. Previous research demonstrates that extension-based directional preference strategies are effective for a large proportion of patients with LBP and are associated with pain reduction, increased mobility, reduced fear of movement, and centralization of radiating symptoms. In parallel with traditional mechanical assessment and treatment methods, pain neuroscience research has highlighted the role of changes in cortical body maps, particularly in the primary somatosensory cortex (S1), in individuals with LBP. People with persistent LBP exhibit altered S1 representations, including changes in size and organization of cortical maps, which are associated with pain, disability, and functional limitations. These representations are dynamic, and movement-based therapies can help normalize them. However, patients with high pain levels, significant fear-avoidance, or sensitized nervous systems may find movement-based interventions difficult to perform. Motor imagery-mentally simulating movement without performing it physically-may provide an alternative method for modifying cortical representations while reducing threat and avoiding symptom aggravation. Motor imagery activates neural regions similar to those used during actual movement execution and may be beneficial for individuals reluctant to engage in active movement. Preliminary findings have suggested that virtual or imagery-based McKenzie extension movements may improve pain, fear-avoidance, catastrophization, and mobility in individuals with LBP. Because centralization of symptoms is a hallmark feature of directional preference-based care, this study aims to further explore whether a brief motor imagery-based extension protocol can influence pain intensity, body pain distribution, psychological constructs, physical measures, and centralization in patients with LBP who demonstrate an extension directional preference. Study Objectives: The primary objective of this study is to evaluate the immediate effects of a guided motor imagery extension protocol in patients with LBP who demonstrate a directional preference for extension. The study aims to determine whether the intervention results in changes in pain intensity, disability, fear-avoidance, pain catastrophization, lumbar flexion, straight leg raise, and pain distribution, as well as whether patients report centralization of symptoms. Study Design: This study is a single-group, pre-post exploratory design conducted across three outpatient physical therapy clinics. Institutional Review Board approval will be obtained prior to study initiation. Eligible patients presenting with LBP will be identified during their initial evaluation. Participants must be between 18 and 65 years of age, able to read and understand English, present with no red flags during review of systems, have no prior spinal surgery, and demonstrate a positive response to extension-based directional preference testing. Participation is voluntary and requires written informed consent. Intervention Procedures: Following consent, participants will complete a demographics questionnaire. A blinded therapist will administer baseline measures including disability, pain intensity, fear-avoidance beliefs, pain catastrophization, active trunk flexion, straight leg raise (SLR), and a pain body chart. Participants will then receive a brief educational explanation of cortical map changes associated with LBP. Next, participants will assume a prone "pre-press-up" position, placing their hands under their shoulders. Instead of performing an active press-up, they will close their eyes and receive verbal guidance through a series of ten motor imagery-based lumbar extension movements. The standardized script instructs participants to visualize completing a full press-up, experiencing spinal extension, holding briefly at end range, and returning to the starting position. Total intervention time is approximately five minutes. Immediately following the imagery protocol, a blinded therapist will repeat all outcome measures. After data collection, clinicians will resume their usual plan of care for each patient. Outcome Measures: Pre- and post-intervention measures include: Oswestry Disability Index (ODI) to assess functional disability Numeric Pain Rating Scale (NPRS) for low back and leg pain Fear Avoidance Beliefs Questionnaire (FABQ), including Physical Activity and Work subscales Pain Catastrophization Scale (PCS) Active lumbar flexion (fingertip-to-floor distance in centimeters) Straight Leg Raise measured with an inclinometer Body chart with grid overlay to quantify pain distribution and potential changes in cortical representation Data Management and Analysis: De-identified data will be compiled and analyzed using descriptive statistics for demographic variables. Pre- and post-intervention comparisons will be performed using paired-samples t-tests with significance set at p \< 0.05. Significant findings will be confirmed with Wilcoxon Signed Ranks nonparametric testing.