In 2009, a study conducted by Kim Lalanne, Danik Lafond, and Martin Descarreaux, the effects of spinal manipulation on the flexion-relaxation phenomenon (FRR) in individuals suffering from chronic low back pain were examined. The objective of the study was to evaluate how spinal manipulation influences the spatiotemporal parameters of the FRR.

Twenty-seven adults with chronic low back pain participated in the study. They were divided into two groups: an experimental group (n = 13) and a control group (n = 14). All participants initially performed a series of trunk flexion-extension movements. Subsequently, the experimental group received lumbar spine manipulation, while the control group remained in a side-lying position for 10 seconds. Following these interventions, both groups performed another series of trunk flexion-extension movements.

Throughout the tasks, the researchers recorded trunk and pelvis angles, as well as surface electromyography (EMG) of the erector spinae muscles at the L2 and L5 levels. They compared various parameters of the FRR between the experimental and control groups, including EMG activity, normalized EMG, and the extension-relaxation ratio.

The results revealed a significant reduction in EMG activity at full trunk flexion specifically at the L2 erector spinae level in the experimental group compared to the control group. Additionally, the experimental group exhibited a significantly increased FRR at the L2 level following spinal manipulation, whereas no significant change was observed in the control group after the side-lying position intervention. However, there were no significant differences in FRR parameters at the L5 level between the two groups.

Interestingly, the onset and cessation angles of the flexion-relaxation phenomenon did not differ significantly between the experimental and control groups or across the different experimental conditions.

In conclusion, this study suggests that lumbar spine manipulation has the potential to transiently modulate the neuromuscular responses involved in stabilizing the lumbar spine among individuals with chronic low back pain. These findings contribute to our understanding of the effects of spinal manipulative therapy on musculoskeletal function in this patient population.

Reference: Lalanne, K., Lafond, D., & Descarreaux, M. (2009). Modulation of the flexion-relaxation response by spinal manipulative therapy: a control group study. Journal of manipulative and physiological therapeutics, 32(3), 203-209.