Background: Low back pain (LPB) is a common health problem. While physiotherapy can relieve pain and the muscle stiffness of patients with LBP was shown to be different from healthy people, few studies have investigated the effect of physiotherapy on back muscle stiffness in patients with LBP.

Objective: To investigate the effect of a 5-day conventional physiotherapy treatment on muscle stiffness of patients with LBP using a newly developed wireless hand-held ultrasound probe.

Methods: A total of ten patients with LBP participated in this study. They received customized conventional physiotherapy containing electrical therapy, traditional Chinese medicine, manipulation and wax therapy. The pain level was evaluated by the visual analogue scale, and the muscle stiffness was measured by a wireless hand-held tissue ultrasound palpation system. The muscle stiffness of left and right sides at L1 and L4 levels and pain level were evaluated in two conditions, including baseline and 5-day post treatments.

Results and discussion: After receiving the treatment, the muscle stiffness of all tested low back regions increased significantly (p=0.040). The muscle stiffness at L4 level was significantly higher than that of L1 level (p=0.021). No significant difference of muscle stiffness between left and right sides was found. The correlation between the muscle stiffness and VAS score appeared to decrease after receiving the treatment (R2 changed from 0.3598 to 0.0533).

Conclusion: A five-day conventional physiotherapy treatment could relieve the pain level and increase the muscle stiffness of patients with LBP as evaluated by a wireless hand-held ultrasound probe. The stiffness of back muscle at L4 level was significantly higher than that of L1 level in patients with LBP. The treatment may change the correlation between the muscle stiffness and VAS score at low back region.