Physical medicine and rehabilitation (PM&R) or physiatry is a particular field of medicine. A doctor who has completed training in this field is referred to as a physiatrist. In order to be a physiatrist one must complete 4 years of medical school and 4 years of post graduate medical training. Most U.S. Physical Medicine and Rehabilitation (PM&R) residencies are 3 years long after internship, although some include internship and are thus 4 years long. Three formal sub-specializations are recognized by the field: pain medicine (in conjunction with anesthesiology, neurology and psychiatry), pediatric rehabilitation, and spinal cord injury (SCI) rehabilitation. Many in the field also subspecialize in areas of musculoskeletal medicine, electrodiagnostics, traumatic brain injury (TBI), cardiopulmonary rehabilitation and neuromuscular disorders.