Percutaneous Peripheral Nerve Stimulation (pPNS) is a physical therapy technique, whose main objective is to treat neuro-musculo-skeletal signs and symptoms by applying a current to a peripheric nerve with a blunt dry needle. Despite its clinical use being already stablished, its use in pathologic subjects is still unknown and, thus, so is its optimal parameterization. The present study proposes to perform two different protocols of peripheral nerve stimulation on neck and low back pain subjects to answer those questions and compared it towards a control group receiving a standard intervention.

Intervention will be performed on the Spinal Nerve (for neck pain subjects) and Inferior Gluteal Nerve and Tibial Nerve (for low back pain subjects), using ultrasonography to guide the needle insertion, without risk of affecting any adjacent structure. The theoretical basis of the technique is to produce analgesia by making controlled changes in the somatosensory system using synaptic plasticity, to ultimate affect the perception of pain through reduction of nociception afference. The protocols will be the following:

• Intervention Group 1: Sensory Threshold, high frequency in trains (ST-bHF). 5 trains of 5 seconds, separated by 55 seconds from each other, at a frequency of 100 hertz (Hz), making 5 minutes of total treatment. The intensity will be set at patient's sensory threshold, ensuring a non-painful perception.
• Intervention Group 2: Theta-Burst Stimulation (TBS). 40 trains separated 10 seconds apart, where each train contains 5 trains separated by 200ms, at a frequency of 5 hertz, resulting in 6 minutes and 45 seconds of total intervention. The intensity will be set at patient's motor threshold, ensuring a non-painful stimulation.
• Intervention Group 3: Transcutaneous electrical nerve stimulation (TENS), at a frequency of 80 hertz and a pulse width of 250 microseconds, for 15 minutes. The intensity will be set at the detection threshold of each patient, generating a sensitive but not painful sensory but not painful.

The study will be a randomised quadruple-blind clinical trial. Two pPNS protocols (ST-bHF, TBS) and a third TENS protocol (TENS) will be compared. To study the effects of these protocols on pain, strength, functionality and electromyographic activity, three measurements will be performed: pre-intervention (Numerical Pain Scale (NRS), NRS for induced pain, Maximal strength + EMG), during the intervention (EMG) and immediately post-intervention (NRS, NRS for induced pain, Maximal strength + EMG). In addition, one week later, subjects will be asked for a pain NRS to assess the mid-term treatment effect.

Inclusion Criteria:

• Adults (+18 years)
• Patients with non-specific/mechanical/articular neck pain.
• Patients with non-specific/mechanical/articular low back pain and/or low back pain accompanied by radicular symptomatology or sciatica.

Exclusion Criteria:

• Pregnancy.
• Severe illnesses: diabetes, cancer, neurological diseases, depression, etc...
• Balanophora (needle phobia).
• Professional athlete.
• Other concomitant physiotherapy treatment for this pathology.
• Patients with neck or low back pain associated with severe bone damage such as fractures or vertebral fissures.

The order of the interventions will be randomized by a third person not involved in the treatment, assessment or statistical analysis. Once the care provider has inserted the needle in each subject, another third person will choose the protocol assigned on the stimulator, previously programmed and codified. Another investigator will take measurements of the variables of interest. Thus, nobody (participant, care provider, investigator and the outcome assessor) will know what intervention is applied.