Spinal manipulation causes variable spine kinematic and trunk muscle electromyographic responses

Study design. Analytic cohort with a convenience sample in a research clinic. Objectives. To determine the influence of a spinal manipulation on trunk kinematics and associated trunk myoelectric activity. Summary of background. While the mechanism of spinal manipulation is unknown, it has been theorized to influence spinal range of motion and trunk muscle activity. Methods. Trunk kinematics were measured in low back pain patients (n=14) during simple range of motion tasks in three planes, while trunk muscle electromyogram signals were recorded bilaterally from paraspinal and abdominal musculature. Kinematics and electromyogram signals were assessed pre–post manipulation. Electromyogram activity was also assessed pre–post manipulation during quiet stance. Results. While no consistent kinematic or electromyographic changes occurred following manipulation across the population, individual changes were observed. The largest changes (>6°) in range of motion occurred in the sagittal plane of three patients experiencing the greatest amount of pain. During quiet stance 17 muscles across all subjects exhibited changes in muscle activity following manipulation. Sixteen of those changes were decreases in muscle amplitude. Conclusions. This study offers some preliminary data on the short-term effects of manipulation on lumbar range of motion and dynamic electromyogram. The findings suggest that the response to manipulation is variable and dependent on the individual, with no change in some to the largest changes seen in the more pained patients.