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Quantifying the lumbar flexion-relaxation phenomenon: theory, normative data, and clinical applications
Randy Neblett1, Tom G Mayer, Robert J Gatchel
1PRIDE Research Foundation, Dallas, TX, USA.
Spine
|July 3, 2003
Summary
The flexion-relaxation (FR) phenomenon, measured by surface electromyography (sEMG) and range of motion (ROM), can be reliably assessed in patients with chronic low back pain. This assessment aids in individualizing rehabilitation and identifying treatment failures.
Area of Science:
- Biomechanics
- Neurophysiology
- Rehabilitation Medicine
Background:
- The flexion-relaxation (FR) phenomenon, known since 1951, involves lumbar extensor muscle relaxation during trunk flexion.
- Its assessment in chronic low back pain (CLBP) patients is intermittent, lacking normative data for clinical application.
- Previous research has limited exploration of the relationship between inclinometric lumbar motion and sEMG signals.
Purpose of the Study:
- To establish a normative database for FR unloaded measurements in asymptomatic individuals.
- To assess the clinical utility of combined sEMG and ROM measurements for evaluating the FR phenomenon in CLBP patients.
- To determine if FR assessment can guide rehabilitation planning, progress monitoring, and early identification of treatment failures.
Main Methods:
- Part 1: Prospective study of 12 asymptomatic subjects to establish reliability of sEMG and ROM measurements for FR and maximum flexion, creating normative data.
- Part 2: Prospective repeated-measures cohort study of 54 CLBP patients assessed for FR using sEMG and ROM before and after rehabilitation (n=34).
- Correlation of pain disability scores with sEMG and ROM; assessment of sEMG sensitivity and specificity for abnormal motion.
Main Results:
- High reliability (r ≥ 0.92) in measuring ROM and sEMG at FR in asymptomatic subjects.
- Asymptomatic subjects exhibited FR within a narrow sEMG range (1-2.3 microV); most flexion occurred at the hip.
- Post-treatment, 94% of CLBP patients achieved FR, showing significant improvements in ROM and pain disability scores.
Conclusions:
- The FR phenomenon reliably indicates maximal lumbar flexion ROM and extensor muscle relaxation.
- FR assessment offers a promising method for personalizing rehabilitation, reducing healthcare utilization, and identifying treatment failures.
- This study is the first to systematically demonstrate that an absent FR phenomenon in CLBP patients can be successfully corrected with treatment.