Messages for Improvement of walking amount based on a stage of change

Based on the transtheoretical model of how be-havior change occurs, this study proposes a support to in-crease the amount of walking through messages. In recent years, lifestyle-related diseases have been threatening people's life expectancy. Regular exercise can prevent lifestyle-related dis-eases. However, currently one in four adults does not get enough exercise. It is not easy to improve the habit of inactivity, and some kind of intervention is required to promote behavioral change. In the transsexual model, which is a model of behavior change, effective interventions differ depending on the stage of change, the transformation stage. In this study, the stage of change is estimated based on the data of the number of steps taken after the intervention with messages. We examine step count data with and without intervention, and with different types of intervention. Seasonal and exogenous components of the step count data were eliminated by the SARIMAX model. In a 6-week experiment with 14 university students and adults, we found that the intervention of e-mail messages could increase the subjects' motivation to exercise. However, it was not possible to identify the types of effective messages for each stage of change.