Effect of Extensible and Non-extensible Lumbosacral Orthoses on the Pain, Disability, back Muscle Endurance and the Flexion Relaxation Phenomenon in Patients with Chronic Non-specific Low Back Pain: A Randomized Clinical Trial

Abstract

Background: Relaxation of paraspinal muscles at the end of flexion range of motion known as flexion-relaxation phenomenon is not present in patients with chronic low back pain (CLBP). Persistent activation of erector spinae muscles throughout flexion in CLBP patients (i.e. lack of FRR) may be a muscular adaptation and or protective strategy indicating patients’ attempt to enhance trunk stiffness and subsequently provide spine stability. It is hypothesized that loss of deep intrinsic muscles control can lead to erector spine muscles hyperactivity. Lumbosacral orthoses (LSO) are expected to decrease erector spinae muscle activity through providing passive trunk stiffness and trunk stability, and thereby return the normal flexion-relaxation pattern.