Myoelectric paraspinal response to spinal loads: potential for monitoring low back pain

LBP evaluation has been hampered by the subjectivity of available clinical procedures and the paucity of factual information about spinal dysfunction. Objective indices of spinal pathomechanics would assist the clinician to prescribe and evaluate appropriate treatment. This project assesses paraspinal myoelectric symmetry as a potential objective measure of low back performance. A preliminary group (N = 39) of symptomatic subjects was prospectively tested to choose parameters for the blinded experiment to follow. The experimental group of volunteers (N = 37) were electromyographically monitored while the subjects performed selected postural tasks which did not produce pain. Results were compared to orthopedic tests and history. Four arbitrary myoelectric classifications were defined for subject grouping and comparison: subjects with symmetrical paraspinal task performance, occasional (less than 4 tasks) asymmetry, low amplitude response for quasi-static loads, and large amplitude asymmetry (greater than 4 tasks). Eighty percent of subjects with significant asymmetry of muscle action had recent LBP history. Isolated task testing is inconclusive as a clinical parameter. However, observation of performance of a series of tasks may be useful in clinical diagnosis and monitoring of function in low back pain.