Effectiveness of polarized polychromatic light therapy on myofascial trigger points in chronic non-specific low back pain: a single blinded randomized controlled trial

Abstract

Abstract Background Phototherapy has been used for the treatment of chronic low back pain. However, the effect of linear polarized polychromatic light (PL) has not been examined on myofascial trigger points in patients with chronic non-specific low back pain (NSLBP). Objectives To investigate the effectiveness of PL on pain intensity, pain sensitivity of active myofascial trigger points (MTrPs) in gluteus medius (GM) and quadratus lamborum (QL) muscles, back disability, and lumbar range of motion in chronic NSLBP. Methods Forty-two participants of both genders with chronic NSLBP were randomly allocated into two equal groups: group A (Linear polarized polychromatic light (PL): 21 participants received polarized light therapy in the range of red and near-infrared rays on myofascial trigger points of bilateral GM and QL muscles for 5 min/point followed by stretching and strengthening exercises for 4 weeks. Group B (Sham PL): 21 participants received the same program but with sham linear polarized polychromatic light therapy. Numeric pain rating scale, pressure algometer, and Roland-Morris Disability Questionnaire were used to measure pain intensity, pain sensitivity (as represented by pain pressure threshold (PPT) of MTrPs of the target muscles and back disability respectively. Further, lumbar flexion, extension, and bilateral rotation were examined with a tape measure, while bilateral side bending were examined with a universal goniometer. Results After the intervention program, significant improvements (p < 0.05) in pain intensity, PPT of MTrPs of left GM (Effect Size (ES): 1.23) and bilateral QL muscles (ES Rt QL: 0.9; Lt QL: 1.56) were found in group A in comparison with group B. Nevertheless, the two groups displayed similar improvements (p > 0.05) in lumbar range of motion and back disability. Conclusion Linear polarized polychromatic light therapy in the range of red and near-infrared rays improves pain intensity and pain sensitivity of myofascial trigger points in chronic NSLBP. Trial registration PACTR, PACTR202111577053926. Registered 22 June 2019-Prospectively registered.