A total of 74 people diagnosed with non-specific chronic low back pain of more than 3 months of evolution and who are not currently undergoing any type of treatment will be recruited, with ages between 35 and 65 years. A random distribution will be made into two treatment groups (monopolar diathermy by radiofrequency versus placebo). Participants will receive treatment three per week for a period of three weeks, in the physiotherapy laboratories of the University of Almería, with a follow-up evaluation post-intervention (one months) and two months after the end of treatment. At their first visit, participants will be screened for study eligibility according to the study inclusion and exclusion criteria, and will be evaluated by a therapist blinded to the intervention. After this face-to-face evaluation, patients will be randomly assigned to one of the two groups and will receive treatment for low back pain according to their random assignment group by two therapists belonging to the research group and trained in the techniques used.

The technique of applying monopolar electrical diathermy by radiofrequency emission (MDR), using the Physicalm® device, allows electromagnetic waves to be applied transcutaneously in a capacitive and monopolar manner, making focused energy deposits in the areas compromised with the painful process. The intervention with this device consists of different independent programs adapted to the different modalities of clinical pain. Through adaptations of the digitally modulated electromagnetic signals in terms of their intensity, frequency, form and duration, analgesia and pain relief can be obtained in different conditions musculoskeletal.

Despite being a clinical electrotherapy technique currently widely used by physiotherapists, there are few clinical trials on the application of monopolar electrical diathermy by radiofrequency emission (MDR) in ailments of lumbar origin caused by myofascial trigger points. The difference with other systems that use high-frequency electrophysical agents such as short waves or microwaves lies mainly in the ability to penetrate the tissues, producing a thermal effect at a greater depth.

Due to all the structural and functional alterations that occur in chronic non-specific low back pain, this randomized clinical trial project was born, with the aim of providing an answer to the disabling symptoms suffered by patients with chronic non-specific low back pain, searching for tools of safe and effective treatment from the field of Physiotherapy, which report a benefit in the symptoms, functionality and quality of life of patients diagnosed with chronic non-specific low back pain caused by PGM.

A total of 74 people diagnosed with non-specific chronic low back pain of more than 3 months of evolution and who are not currently undergoing any type of treatment will be recruited, with ages between 35 and 65 years. A random distribution will be made into two treatment groups (monopolar diathermy by radiofrequency versus placebo).

The 37 subjects of the experimental group (EG) will receive an application of monopolar electrical diathermy by radiofrequency emission (MDR) by means of the Physicalm® device (developed by the electro-medicine company Biotronic Advance Develops SL), on the lumbar muscles by means of rotary movements and translation, adapting to the muscle fibers of the lower back, contacting and applying the treatment to the active myofascial trigger points of the following muscles: quadratus lumborum, multifidus and iliocostalis, following the PGM maps described by Travell and Simons. A pulsed emission of 840 KHz and 30v will be carried out dynamically for a treatment time of 20 minutes. 3 weekly sessions will be performed for 3 weeks, a total of 9 treatment sessions.

The 37 subjects in the control group (CG) will be administered a placebo treatment consisting of the same execution protocol as the EG, but with a non-emitting device whose software and hardware will be exactly the same as that used in the EG. The intervention will be simulated for 20 minutes.

A pulsed emission of 840 KHz and 30v will be carried out dynamically for a treatment time of 20 minutes. 3 weekly sessions will be performed for 3 weeks, a total of 9 treatment sessions.

The outcome assessor and study statistician will be blinded throughout the entire process.

A baseline assessment of the primary and secondary outcome measures will be performed before randomization of the participants to the different groups, an immediate post-treatment assessment (1 day after the last intervention) and an assessment two months after the end of the procedure intervention (follow-up).

Inclusion Criteria:

• LBP for/over three months
• Age between 30 and 65 years
• Score equal or superior of four points on the Roland Morris Disability
• Questionnaire Not currently receiving physical therapy.

Exclusion Criteria:

• Presence of lumbar stenosis;
• Any clinical signs of radiculopathy;
• Diagnosis of spondylolisthesis;
• Diagnosis of fibromyalgia;
• Treatment with corticosteroid or oral medication within the past two weeks;
• A history of spinal surgery;
• Contraindication for MDR;
• Disease of the central or peripheral nervous system; (9) Patients with cardiac complications and / or patients who have recently undergone radiotherapy.

Participants are not familiar with diathermy, and will lie prone while receiving treatment. They will also be cited on different days of the week to the experimental group.

The therapist assessing the outcome measures does not know which group the patients belong to, and will be supervised by the principal investigator so that they do not ask any questions about it.