The overall aim of this pilot feasibility study is to determine if 12-week moderate intensity exercise can safely alleviate posttraumatic symptoms in premenopausal women veterans.

Specific aims of the study are to;

1. Determine the feasibility, safety, and tolerability of 12-week moderate intensity exercise
2. Explore potential therapeutic benefits of 12-week moderate intensity exercise. Outcome data will include posttraumatic and depressive symptoms.
3. Explore potential therapeutic effects of a 12-week moderate intensity exercise on comorbid pain syndrome and quality of life.

Inclusion Criteria:

1. Women veterans ages 18 and older
2. Premenopausal women of childbearing potential with a negative pregnancy test
3. DSM IV-TR confirmed PTSD related to any traumatic event as measured by Clinician Administered PTSD Scale (CAPS) with a CAPS score of at least 45
4. Relatively low sedentary life style
5. Existing psychotropic medications are allowed if on a stable dose
6. Evidence-based psychotherapy (e.g. Cognitive Processing Therapy or Prolonged Exposure) is not allowed to start of the study. However supportive or educational groups that are not PTSD-focused are allowed.

Exclusion Criteria:

1. Other psychiatric diagnoses including bipolar disorder, schizophrenia, schizoaffective disorder, active substance dependence/abuse (use in the past 1 month), obsessive-compulsive disorder, and eating disorders.Comorbid major depressive disorder, dysthymia and generalized anxiety disorders are not excluded.
2. Serious psychopathology
3. Actively suicidal or homicidal
4. Psychiatric hospitalization within the past 30 days
5. Active medical conditions that preclude the use of aerobic exercise such as uncontrolled hypertension, active musculoskeletal degenerative conditions, and symptomatic cardiovascular or respiratory conditions.