This study aims to evaluate the effectiveness of optimized High-Intensity Laser Therapy (HILT) compared with sham treatment in patients with trapezius myofascial pain syndrome. Outcomes include pain intensity, cervical range of motion, functional disability, and depressive symptoms measured at baseline, post-intervention, and 16-week follow-up.

Myofascial pain syndrome of the trapezius muscle is a common cause of chronic neck and shoulder pain associated with functional limitation and psychological distress. Although High-Intensity Laser Therapy is increasingly used in clinical practice, high-quality evidence regarding its long-term effects and optimal treatment parameters is limited.

This double-blind, randomized, placebo-controlled trial will enroll 104 adults with clinically diagnosed trapezius myofascial pain syndrome. Participants will be randomly assigned to receive either optimized High-Intensity Laser Therapy or sham laser treatment. Outcomes will be assessed at baseline, immediately after the intervention, and at 16-week follow-up. This study aims to provide evidence for a standardized, patient-centered HILT protocol suitable for routine clinical practice.

Inclusion Criteria:

• Adults aged 18 to 65 years
• Clinically diagnosed trapezius myofascial pain syndrome
• Duration of symptoms ≥ 4 weeks
• Pain intensity ≥ 4 on NPRS
• Able to provide informed consent

Exclusion Criteria:

• Red-flag medical conditions (e.g., malignancy, spinal cord compression)
• Neurological disorders affecting the neck or shoulder
• Cognitive impairment or inability to communicate
• Previous laser therapy to the neck/shoulder region within the last 6 months