Walking or High Intensity Exercise for Anxiety

Inclusion Criteria: * Anxiety Sensitivity Index score of ≥20 (i.e., high anxiety sensitivity) * Primary psychiatric diagnosis of generalized anxiety disorder (GAD), social anxiety disorder, or panic disorder * Currently sedentary (≤60 minutes of moderate intensity exercise per week for the past 3 months) * Able and willing to provide informed consent Exclusion Criteria: * Lifetime history of Bipolar I or II or any psychotic disorder * Meets criteria for bulimia or anorexia in the past 6 months * Meets criteria for substance use disorder in the past 3 months * High current suicide risk as indicated by a score of ≥4 on the C-SSRS * Risk for exercise according to Physical Activity Readiness Questionnaire with excluded medical conditions including heart conditions, lung disease, bone/joint problems, or seizures * Women who are currently pregnant or plan to become pregnant during the duration of the study * Participation in concurrent evidence-based therapy (e.g., cognitive behavioral therapy) targeting anxiety or depression (supportive therapy and couples therapy are allowed) * Participants on psychiatric medication must be on a stable dose for ≥8 weeks prior to participation * Current substance abuse or positive urine toxic screen (recreational use of marijuana is permitted based on clinical assessment on the MINI that it does not meet criteria for cannabis use disorder)