Optimization of a Behavioral Intervention to Increase Physical Activity in Older Adults Living With HIV

This study is testing different ways to encourage older adults (50 and over) living with HIV to become more physically active, including using a Fitbit activity tracker and personalized coaching. The goal is to find the most effective and acceptable combination of strategies. **You may be eligible if...** - You are 50 years or older and HIV-positive - You have been on antiretroviral therapy (HIV medications) continuously for more than 3 months - You are currently doing very little physical activity (less than 90 minutes of moderate exercise per week) - You are medically cleared for moderate exercise (or can get clearance from your doctor) - You can use a smartphone/Fitbit app and communicate in English - You are able to walk without an assistive device **You may NOT be eligible if...** - You have a medical condition that prevents physical activity or study participation - You have hazardous levels of alcohol or drug use - Your cognitive score is 16 or below on the MoCA screening test Talk to your doctor to see if this trial is right for you.