Neuromuscular response amplitude to mechanical stimulation using large-array surface electromyography in participants with and without chronic low back pain

Purpose: The present study aimed to compare the neuromuscular response under various mechanical stimulations of the lumbar spine in participants with and without chronic low back pain (cLBP). Methods: Four mechanical stimulations, characterized by forces ranging from 75 to 225 N, were delivered using a servo-controlled linear actuator motor to the L3 spinous process of 25 healthy participants and 26 participants with cLBP. Lumbar neuromuscular responses were recorded using 64-electrodes large surface electromyography arrays. Between-group differences in the dose–response relationship (neuromuscular response amplitude according to each force level) were assessed using mixed model ANOVAs. Results: No differences between groups were shown (all p values > .05). A significant linear relationship was observed between forces and neuromuscular response amplitudes (p < .001) indicating an increase in response amplitudes with increasing stimulation force. Responses were observed throughout the lumbar region with highest response amplitudes in the vicinity of the contacted vertebra. Conclusion: The neuromuscular response amplitude triggered by localized lumbar mechanical stimulations does not differ between participants with and without cLBP. Moreover, even though stimulations were delivered at specific spinal segment, a neuromuscular response, although rapidly decreasing, was observed in areas distant from the contact site.