Modulation of the Flexion-Relaxation Response by Spinal Manipulative Therapy: A Control Group Study

Abstract

This study evaluated the effects of spinal manipulation on spatiotemporal flexion-relaxation phenomenon parameters in individuals with chronic low back pain. Twenty-seven adults with chronic low back pain participated in this study and first performed a block of 5 complete trunk flexion-extensions. The experimental group (n = 13) was then submitted to lumbar spine manipulation, whereas the control group (n = 14) was placed in a side-lying control position for 10 seconds. All study participants performed thereafter a second block of 5 trunk flexion-extensions. Trunk and pelvis angles and surface EMG of erector spinae at L2 and L5 were recorded during the flexion-extension tasks. Flexion angles corresponding to the onset and cessation of myoelectric silence, normalized EMG, and the extension-relaxation ratio were compared across experimental conditions. A significant reduction of EMG activity at full trunk flexion at the L2 erector spinae level was observed in the experimental group compared to the control group. No significant effect was seen at L5 in both groups. The experimental group presented a significantly increased postmanipulation FRR at L2, whereas the control group ratio did not vary after the "side-lying control position." No significant difference was seen at L5 in both groups. Flexion-relaxation phenomenon onset and cessation angle did not differ across groups or conditions. This study shows that lumbar spine manipulation can, at least for a brief period, modulate stabilizing neuromuscular responses of the lumbar spine in a group of patients with low back pain.