The Role of Muscle Activity in Low Back Pain
Muscle firmness, spasm or "trigger points" are perceived as palpable by many clinicians and as specifically tender by many patients. No reliable electrodiagnostic methods, such as needle electromyography, yet exist to confirm the presence of palpable muscle firmness or subjectively tender muscles, a shortcoming the authors of this study sought to address.
Previous studies provide evidence that cortical-evoked potentials on magnetic stimulation of muscles are influenced by muscle contraction, vibration and spasm. This study investigated whether these potentials correlated with palpatory muscle spasm, patient symptoms and disability in 13 subjects with a history of low back pain (LBP). Patients completed an LBP visual analogue scale (VAS) and a Roland-Morris Activity Scale (RMAS). Cortical-evoked potentials were recorded using a magnetic stimulator placed over the lumbar paraspinal muscles with subjects in the prone position. A clinician, blinded to the results of the cortical-evoked potentials, VAS and RMAS scores, evaluated the patients for the presence of muscle spasm.
These parameters were repeated after two weeks of soft-tissue massage and manipulation consisting of ischemic compression applied to affected muscles in the back and lower extremity, followed by distraction of the lumbar spine. Results indicated that patients responded favorably to treatment, evidenced by significant decreases in VAS and RMAS scores following treatment. Cortical potentials showed a significant increase in amplitude, and there was significant correlation noted between changes in cortical potentials after treatment and changes noted in paraspinal muscle spasm and VAS and RMAS scores. Findings demonstrate "...the measurement of muscle activity may be more important in the assessment of low back pain than is commonly accepted."
Zhu Y, Haldeman S, Hsieh C-Y, et al. Do cerebral potentials to magnetic stimulation of paraspinal muscles reflect changes in palpable muscle spasm, low back pain, and activity scores? Journal of Manipulative and Physiological Therapeutics
, Sept. 2000:23(7), pp458-64.
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