The mechanical stimulation of the muscle produces a local twitch response or rapid depolarization of muscle fibers.  After this process, the muscle activity dramatically reduces resulting in relaxation and decrease pain and dysfunction.  This decrease in pain is related to the removal of muscular compression on joint, nerve, and vascular tissue.  Sometimes the insertion of the needle also reproduces “referred pain” symptoms.  This is a positive sign confirming the trigger point as the source of the pain.  It is further theorized that dry needling stimulates the release of endogenous opiods, and initiates the healing process.  Dry needling is highly effective for chronic muscle and repetitive sport injuries.