Protocol of a feasibility study of a virtual personalized (N-of-1) trial for increasing low-intensity physical activity in older adults via habit formation

•What uncertainties exist regarding feasibility of a virtually delivered N-of-1 trial?•This protocol was designed to test the feasibility, satisfaction, adherence, preliminary efficacy, and heterogeneity of effects of a virtually delivered personalized behavioral intervention to increase low-intensity physical activity in adults 45–75 years old. All components will be delivered without direct personal contact via an automatic platform. Activity will be continuously measured by a wearable technology.•Satisfactory acceptance, adherence, preliminary efficacy, and heterogeneity of effects of the virtual protocol will suggest whether a larger randomized controlled trial, personalized N-of-1 trial, or revised pilot program should be the logical next step.