Brief Exposure and Exercise for PTSD.

Inclusion Criteria: * Provide informed consent and are willing to participate in therapy sessions twice weekly, which include moderate-intensity aerobic exercise. * Participants must be adults aged 18-64 meeting the criteria for PTSD within the past month, who are not currently receiving treatment from other psychotherapy or are on unstable psychiatric medication (i.e., less than four weeks of psychiatric medication). * Participants should be able to engage in 25 minutes of moderate-intensity aerobic exercise (i.e., 70-75% of max heart rate). * Participants must be able to speak and read English fluently to participate in the current study. Exclusion Criteria: * Participants who endorse health condition(s) that would prevent moderate exercise. * Participants who endorse (i.e., "yes") any items on the Physical Activity Readiness Questionnaire (PARQ) that is not controlled or managed. * Participants with any injuries to the lower extremities that may hinder riding an exercise bicycle. * Psychiatric exclusion criteria include recent (within the past three months) severe use disorder(s), high risk for suicide (i.e., plan, intent, or recent attempt), mania, or psychotic symptoms unrelated to PTSD symptoms. * Participants currently seeking or undergoing any other trauma-focused psychotherapy treatment.