Exercise for Anxiety

90 sedentary adults with a primary anxiety disorder and high anxiety sensitivity will be randomized to either 8 weeks of 1) low intensity exercise, or 2) flexible titration to high intensity exercise (HIE). Blinded, validated clinician-rated and patient-rated outcomes will be assessed over treatment and at 1- and 3-month follow-up. To better understand what mechanisms influence decisions to exercise in the real-world, we will use of heart rate (HR) as an objective mechanistic target for exercise intensity, examine changes in valuation of exercise through a neuroeconomics task, examine changes in interoceptive sensitivity with a heartbeat detection task, and integrate of ecological momentary assessment (EMA) to measure effects of immediate changes in mood with exercise on anxiety outcomes and adherence.