The purpose of this study is to examine the efficacy of exercise + therapy to therapy alone to determine if they can improve the effects of prolonged exposure therapy (PE) in reducing symptoms of anxiety associated with Post-traumatic Stress Disorder (PTSD). In addition the two strategies (i.e., exercise + therapy and therapy alone condition) will be compared in terms of levels of brain-derived neurotrophic factor (BDNF). BDNF is a protein that helps to support the survival of existing neurons and stimulate the growth of new neurons and synapses. BDNF is important to learning and memory in general and therefore may be associated with the learning and memory as it relates to PE and corresponding symptoms PTSD improvement.

Inclusion Criteria:

• You have PTSD.
• You are between the ages of 18 and 65.
• You have written physician approval/medical clearance to participate in an exercise protocol.
• You are currently taking no psychotropic medications or are able and willing to discontinue these medications prior to the first PE session.

Exclusion Criteria:

• You are currently participating in a structured exercise program.
• You have severe depression.
• You have any history of bipolar disorder, psychotic disorder, or obsessive compulsive disorder.
• You have a diagnosis of eating disorder, or substance abuse or dependence (excluding nicotine) within the past six months.
• You have any history of a suicide attempt, or are at a significant risk or self-harm or harm to others.
• You have ever been diagnosed with organic brain syndrome, mental retardation, or other cognitive dysfunction.