- Subjects will be excluded if the examining therapist cannot provoke either active or latent MTrPs of the subject's low back muscles and/or elicit symptoms with manual passive movement of the spine at the joints of the low back. Exclusion criteria will also consist of the presence of any red flags revealed in the patient history (i.e., tumor, metabolic diseases, RA, osteoporosis, prolonged history of steroid use, prior lumbar surgery, current pregnancy, etc.) or examination (i.e. signs consistent with significant nerve root compression). Subjects will be excluded if they demonstrate signs of Chronic Regional Pain Syndrome (CRPS), are currently seeking litigation, are unable to speak English, and/or have been diagnosed with a condition that can cause prolonged MTrPs such as fibromyalgia, hypothyroidism, or iron deficiency. In addition, no patients who have a transmittable blood disease will be included.