This study evaluates the deep dry needling technique as a percutaneous technique included in the professional field of physiotherapy.

The project quantifies a significant limit on the number of local twitch responses necessary for the favorable treatment of myofascial pain and analyzes the injury degree and/or the repair of myofascial tissue, with "Elastography".

The myofascial shoulder pain caused by myofascial trigger points, is one of the main causes of medical consultation and functional disability in the general population and particularly in the amateur athlete.

Nowadays, many physiotherapists all over the world, study and practice the dry needling as a therapeutic tool for the treatment of myofascial trigger points. The most used modality is the technique described by Hong:

• This technique introduces an acupuncture needle in the skin until reaching the dysfunctional muscle fiber. To do so, it uses maneuvers "fast in" and "fast out" of needle, until the extinction of local twitch responses or the tolerance of the patient.
• The local twitch response is defined as a reflex and transitory contraction of a group of muscle fibers associated with a myofascial trigger points.
• The technique eliminates muscle contractile activity by mechanical interruption of their muscle fibers, mechanism which finishes with the sensitization of nearby nerves and with the start of the nociceptive modulation peripheral, segmental and central.

The dry needling technique, in its eagerness to obtain local twitch responses, pierces the muscle fibers both dysfunctional and normal, the fascial tissue that wraps the myofascial trigger points and also neuro-vascular structures. That is, the treatment of myofascial trigger points with dry needling, makes reference to a mechanical trauma done with a acupuncture needle.

The myofascial tissue injured can suffer repair or regeneration, which is mainly due to the extension of the lesion. The process of healing of a wound is strictly regulated by multiple growth factors and cytokines, which are released into the wound. The alterations that disturb the healing process, can lead to chronic wounds that do not heal or to an excessive fibrosis.

The pathobiological processes, in form of fibrosis, would present changes in stiffness and elasticity of the neo-tissue. The quantitative elastography, is shown as an effective tool to measure the amount of fibrosis, occasioned by repeated percussion of the acupuncture needle on the myofascial tissue.

Inclusion Criteria:

• Unilateral shoulder pain or referred pain pattern of the infraspinatus muscle.
• Pain Intensity with a minimum score of 2 on the Wong-Baker scale, using the homolateral "test hand-back".
• Process time more than 1 and less than 10 weeks.
• Age of 18 years old to 49 years old.
• Written Informed Form.

Exclusion Criteria:

• Conventional pharmacological treatment of NSAIDs and / or muscle relaxants, the 48 hours before or during the study.
• Coagulation pathology or anticoagulant therapy.
• Pretreatment with infiltration and / or steroid injections during the last year.
• Physiotherapy Pretreatment, in the cervical region or shoulder girdle during or in the last week taking part in the study.
• Dry needling pretreatment in the cervical region and / or shoulder girdle during or in the last month before taking part in the study.
• History of fracture or dislocation of the shoulder to study, in the last year.
• Dermatological disorders or erosions in the treatment area (infraspinatus fossa).
• Metals allergy such as chromium or nickel.
• Fibromyalgia diagnosis, myelopathy, cervical radiculopathy or neurologic disease.
• Fear of needles.
• Pregnant women.
• Suffering a traumatic accident of the upper extremity and / or cervical-thoracic spine during the study (it will pass to the zero week).
• Medical-legal litigious, by financial compensation.
• Drugs or alcohol abuse / consumption history.
• Cognitive inability to complete the health forms.