Inclusion Criteria:  Unilateral mechanical shoulder pain of nonspecific origin (non-traumatic) lasting at least 3 months. Weakness in flexion, abduction and/or external rotation isometric strength testing. Presence of scapular dyskinesis according to Kibler, Scapular Assistance Test, and Scapular Reposition Test.  Exclusion Criteria:  Previous shoulder surgery. History of shoulder fracture or glenohumeral luxation. History of acromioclavicular joint injury. Presence of massive rotator cuff rears. Presence of frozen shoulder. Cervical hernias or radiculopathy. Fibromyalgia. Neuropathic pain. Cervical and/or vestibular problems with dizziness, unsteadiness, or vertigo. Medical contraindication for performing exercise (cardio-vascular or cardio-pulmonar diseases, systemic diseases, metabolic diseases in non-controlled acute state). Blindness. Actually being treated with physical therapy for shoulder pain.