BACKGROUND: Effectiveness of inversion traction has been revealed in patients with chronic low back pain (CLBP), however, it is still unknown as to which angles of inversion traction positively affect patients with CLBP.

OBJECTIVE: To investigate the angle-effects of inversion traction on pain sensation, lumbar flexibility, and trunk muscles (flexors and extensors) strength in patients with CLBP after an 8 week treatment program.

METHODS: Forty-seven women suffering nonspecific CLBP for 23.00�5.45 weeks were included prospectively and randomized into 3 groups: supine group (SG; n= 15), inversion− 30 group (I30G; n= 18), and inversion− 60 group (I60G; n= 14), respectively. Each group completed a 3-minute� 3-set inversion traction protocol at 0, inverted− 30, or inverted− 60, respectively for 4 days a week during 8 weeks. The outcome measures included rating of pain using the visual analogue scale (VAS), flexibility of lumbosacral joint, and the isokinetic strength of the trunk flexors and extensors at 60/s.

RESULTS: Pain was significantly improved after 8 weeks. The reductions observed in VAS scores were lower in the I60G compared with the changes in I30G and SG. Significant interaction effects were observed in trunk flexion and extension particularly in the I60G condition. There was also a significant increase in the extensor peak torque of the I60G.

CONCLUSIONS: Inversion traction at angle of− 60 reduced back pain or discomfort and improved lumbar flexibility and isokinetic trunk extensor strength in patients with CLBP following an 8 week program. Therefore, this treatment modality may be suitable for patient groups of similar CLBP phenomenology.