The purpose of this study is to determine if addition of Transcutaneous Electrical Nerve Stimulation (TENS) to routine physical therapy improves movement-evoked pain in patients with fibromyalgia (FM).

The study will also determine if addition of TENS to routine physical therapy (PT) improves disease activity and symptoms, increases adherence to physical therapy, increases the likelihood of meeting patient specific functional goals, and reduces medication use.

This study is a pragmatic clinical trial in outpatient PT practices utilizing cluster randomization by healthcare system and facility size. Sites will be randomized to enroll all eligible and consented participants with FM to TENS with PT, or PT only (no TENS). We are identifying 25-35 clinics across 6 healthcare systems in both rural and urban settings. We will enroll 450 patients that self report a clinician diagnosis of FM. At each site, TENS (or no TENS) will be applied during each visit along with individualized PT treatment specified by the physical therapist. Participants randomized to TENS intervention sites will receive TENS units and electrodes at baseline to be applied to the cervical and lumbar regions. Participants will take the units home and bring the units back to their PT clinic visits with instructions for use at home while active and during their exercises. The physical therapist at each clinic will complete routine documentation of treatment. In addition to the primary and secondary outcomes, Electronic Health Record data variables will be collected as exploratory outcomes. Variables including adherence to treatment will be extracted from each site's Electronic Health Record. Patient-reported assessments will be obtained from the participant's at home the day of their second PT visit (Baseline) and at 30, 60 (primary outcome), 90, and 180 days following enrollment. The primary and secondary outcome assessments will be comparing TENS and no TENS groups in terms of changes from baseline to 60 days.

Participants will be identified after they are referred for PT for treatment of primary fibromyalgia (FM) or chronic pain (pain lasting more than three months). At their first (intake) physical therapy visit, they will be provided information about the study that can be accessed on paper or on-line. They will perform an electronic screening form on the first visit if interested in participating. Participants will provide e-consent after eligibility is confirmed at the initial PT visit. At the second PT visit after e-consent is signed, participants will be provided instructions on logging onto REDCap for data capture and accessing the case report forms. Participants enrolled at a TENS site will then be instructed in use of TENS and the TENS unit with electrodes will be provided. Those participants enrolled at a no TENS site will skip the instruction in use of TENS but will then receive instructions along with the TENS units at day 65. Participants will be instructed to capture all baseline assessments at home before their next PT visit before and following their first TENS treatment (or no TENS) at home (day 1). At 30, 60, 90, and 180 days following enrollment, participants will complete the same assessments at home including pain ratings at rest and with movement along with questionnaires. The primary and secondary outcome assessments will be comparing TENS and no TENS groups in terms of changes from baseline to 60 days.

Inclusion Criteria:

1. Age 18 until 99.
2. Clinician diagnosis of FM
3. Referred for land-based PT
4. Referred for treatment for FM or chronic pain (pain lasting more than 3 months)
5. Able to provide informed consent.
6. Fluent in reading English
7. Willing to use TENS

Exclusion Criteria:

1. Contraindications to TENS use including:

   1. Pacemaker, defibrillator, implanted neurostimulator or implanted device
   2. Epilepsy
   3. Currently pregnant or plan to become pregnant in the next 6 months
   4. Allergic reaction to patches with gel
   5. Current treatment for cancer

2. Currently enrolled in another pain control study

3. Use of TENS within the last 30 days

4. Clinically unstable medical or psychiatric issues

The current study is expected to generate patient-reported outcomes for individuals with fibromyalgia across a broad spectrum of domains, pain, fatigue, function, psychological factors, and quality of life. We will also collect some data from the electronic health record about number of physical therapy visits, Current Protocol Terminology (CPT) codes for treatments, and the patient-specific functional scale. In addition, we will have TENS usage data downloaded from the TENS devices that will show the number of minutes of TENS use and the number of 30 minute sessions completed. Data will be collected prior to the intervention (baseline data) and 30, 60, 90 and 180 days after enrollment.

Analysis datasets will be made available at the time of publication of the primary manuscript. Complete datasets and accompanying resources will be deposited to the designated NIH Helping to End Addiction Long-term initiative (HEAL) data repository after the completion of the primary aim manuscript.

In accordance with NIH Collaboratory policies, we will prepare the primary analysis datasets (at a minimum) for submission to the Collaboratory Coordinating Center. In accordance with International Committee of Medical Journal Editors (ICMJE) policies, we will prepare the primary analysis datasets for review and reproducibility by peer-reviewed journals. We will prepare the final datasets and accompanying resource documents for final deposit to the designated NIH HEAL data repository.

Publications will be made available to the public using open access publishing, so they become available immediately to the public. All publications will be accessible through PubMED, google scholar, and available to the public through open access.