Clinical utility of flexion-extension ratio measured by surface electromyography for patients with nonspecific chronic low-back pain.

Background: Patients with chronic nonspecific low-back pain (CNSLBP) lack the flexion-relaxation phenomenon in full-trunk bending. This can be quantified by surface electromyography (SEMG) measurement of lumbar erector muscle. The study objective is to explore the clinical utility of the SEMG flexion-extension ratio (FER) in distinguishing patients with CNSLBP from painfree persons.