Abstract: Objective To investigate the changes of surface electromyographic signal during lumbar flexion-extension after sling exercise therapy (SET) in patients with chronic nonspecific low back pain (CNLBP). Methods 30 patients with CNLBP received SET, 3 times a week for 4 weeks. The surface electromyographic signals of erector spinae and multifidus of both sides were collected, when they were in erect position, flexion motion, maximum voluntary flexion, and back to erect position, before and after intervention. The average electromyogram (AEMG) was analyzed, and the flexion-relaxion ratio (FRR) was compared. Results The FRRs of both erector spinae and multifidus were lower in the painful side than in the healthy side before intervention (P<0.05). There was no significant difference in the FRRs of both erector spinae and multifidus between 2 sides after intervention. Conclusion SET may improve the active motion function of the erector spinae and multifidus of the painful side and recovery of flexion-relaxation phenomenon.

Key words: chronic nonspecific low back pain, sling exercise therapy, surface electromyography, flexion-relaxation phenomenon, flexion- relaxion ratio