This is an 8-week experimental, repeated-measures clinical trial randomizing 120 Service Members with symptoms of PTSD into one of four groups: 1) imaginal exercises of exposure therapy only, 2) aerobic exercise only, 3) imaginal exercises augmented with aerobic exercise, or 4) self-care.

One of the signature injuries of combat operations following 9/11 is posttraumatic stress disorder (PTSD). The most effective treatment for PTSD is exposure therapy where, under the supervision of a trained therapist, individuals are exposed to prolonged and repeated imagined images of the trauma until the images no longer cause severe anxiety. Various forms of exercise have been used to treat a broad range of depression and anxiety disorders and exercise has been used with some success to treat individuals with PTSD. Considering the population of otherwise healthy and physically active Service Members suffering from symptoms of PTSD, it seems possible that exercise might serve as an outlet for the emotional reactions experienced during therapy, decreasing emotional distress, and increasing the individual's tolerance to imaginal exposure serving as a powerful adjunct to exposure therapy. The purpose of this study to explore the role of exercise in the treatment of symptoms of posttraumatic stress disorder (PTSD), specifically determining if the efficacy of imaginal exercises, part of exposure therapy for PTSD, can be improved by augmenting the therapy with aerobic exercise. Towards this end, this 8-week experimental, repeated-measures clinical trial will randomize 120 Service Members with symptoms of PTSD into one of four groups: 1) imaginal exercises of exposure therapy only, 2) aerobic exercise only, 3) imaginal exercises augmented with aerobic exercise, or 4) self-care.

Inclusion Criteria:

• be an Active Duty, Reserve, or National Guard Army, Air Force, Navy, or Marine Veteran of Operation Iraqi Freedom (OIF) / Operation Enduring Freedom (OEF) eligible for military medical care
• be at least 18 years old
• be able to read and speak English
• answer "no" to the seven questions of the Physical Activity Readiness Questionnaire (PAR-Q), or have primary care provider approval to undertake an exercise program.
• score ≥25 on the PTSD CheckList - Stressor-Specific(PCL-S); participants scoring >50 on the PCL-S will be contacted weekly to ensure that their symptoms are under control and they do not require a higher level of care.
• report on the PTSD Symptom Scale - Interview (PSS-I) an exposure to a traumatic event (Criterion A), at least one re-experiencing symptom (Criterion B), and at least one avoidance symptom (Criterion C)
• participants taking psychotropic medications agree to work with their prescriber to remain on stable doses of any prescribed psychotropic medications for the duration of the intervention and through the 1-month follow-up assessment as much as possible and as medically indicated
• anticipate being in the area for at least three months to complete intervention and 13-week follow-up assessment

Exclusion Criteria:

• score <25 on the PTSD CheckList - Stressor Specific (PCL-S) (Those scoring <25 do not have enough symptom severity to adequately test the study hypotheses
• have undergone exposure therapy for PTSD within the last year
• be taking benzodiazepines every day on a prescribed schedule (Individuals prescribed and taking a benzodiazepine only as needed will not be excluded.)
• suicidal ideation with moderate to severe intent warranting intervention
• active psychosis or mania
• be on a medical profile that prohibits exercise