The goal of this clinical trial is to assess the effects and safety of transcutaneous electrical nerve stimulation (TENS) in adults with myofascial low back pain. Eligible participants will receive TENS treatment 5 times per week for 4 weeks. Pain intensity and functional outcomes will be assessed at baseline and weekly during the 4-week treatment period, and adverse events will be recorded.

This study is a prospective, open-label, single-arm, self-controlled clinical trial conducted at the Department of Orthopaedics, Xijing Hospital. A total of 40 adult participants with myofascial low back pain will be recruited according to predefined inclusion and exclusion criteria and enrolled after providing written informed consent.

All enrolled participants will receive transcutaneous electrical stimulation (TENS) therapy with a treatment schedule of 5 sessions per week for 4 consecutive weeks. The stimulation parameters and single-session duration will be set within a safe range and may be adjusted according to individual tolerance.

Outcome assessments will be performed at baseline (Day 0, before intervention) and at Weeks 1, 2, 3, and 4 after treatment initiation. Pain intensity will be evaluated using the Visual Analog Scale (VAS; 0-10). Secondary outcomes include the Oswestry Disability Index (ODI), Japanese Orthopaedic Association (JOA) score, and the Short Form-36 (SF-36) to assess functional status and quality of life.

Safety will be monitored throughout the study, with adverse events and complications recorded during the study period and follow-up.

Inclusion Criteria:

1. Adults aged 18-65 years
2. Diagnosis consistent with myofascial low back pain (localized low back pain with a palpable taut band; referred pain and/or sensory changes near a specific trigger point; an identifiable tender spot within the taut band; mild muscle weakness and/or some limitation of joint range of motion)
3. Mild pain intensity at baseline (VAS < 4 on a 0-10 scale)
4. Symptom duration > 1 month
5. Able to understand the study procedures and demonstrate good compliance/cooperation
6. Written informed consent provided

Exclusion Criteria:

1. Low back pain due to other causes, including but not limited to lumbar disc herniation, lumbar spinal stenosis, ankylosing spondylitis, spinal tumor, spinal tuberculosis, or spinal infection
2. Received physical therapy, interventional procedures, or medication treatment within 4 weeks prior to enrollment that may affect pain or function assessment
3. Systemic disease or organ dysfunction
4. Skin/soft tissue breakdown or infection at/near the planned treatment area
5. Use of sedative medications or opioid analgesics within 6 months prior to enrollment, or currently receiving other treatments that may affect study outcomes
6. Severe psychiatric disorder or inability to cooperate with study procedures
7. Pregnant or breastfeeding women

This is an open-label study with no masking. Participants, care providers, investigators, and outcome assessors are all aware of the intervention assignment, as all participants receive the same TENS intervention.