An Investigation Into the Onset, Pattern, and Effects of Pain Relief on Lumbar Extensor Electromyography in People With Acute and Chronic Low Back Pain

ObjectiveThe aim of this study was to use an experimental pain relief model to determine the effect of pain relief on lumbar muscle function in people with low back pain.MethodsA test-retest design was used with all data collection being completed within a therapy setting. Twenty people with acute and 20 with chronic low back pain were recruited from general practitioner and therapist referrals. Participants completed spinal movements and lifting. Electromyography (EMG) was used to measure the pattern of muscle activity, onset of muscle activation, and peak activation of bilateral lumbar multifidus and iliocostalis. Movements were investigated before and after pain relief, through the self-administration of oral analgesia.ResultsElectromyography profiles and peak values were reliable across 3 trials, and EMG profiles correlated well with kinematic profiles. Specific EMG profiles were commonly associated with specific kinematic values, and on the whole, the EMG profiles were unaffected by pain relief. Muscle onset times and peak muscle amplitudes were not affected by pain relief in either acute or chronic low back pain.ConclusionThis study showed that the EMG activities from the lumbar region, including lumbar multifidus and iliocostalis, are reliable, and specific EMG profiles are identifiable. Pain relief as achieved in this study did not affect the pattern of EMG activity, onset of muscle activation, or peak activation values.