As the number of older adults in our society increases, a greater demand is put on our healthcare systems. This increasing demand on healthcare and especially on the front-line care-givers and professionals has led to a greater need for individual patients to actively engage in personal behaviour change to manage their conditions and improve their quality of life. The Human Computer Interaction Community has a growing body of research pertaining to the many and varied ways that Behavioural Change Techniques have been integrated into digital applications and intervention systems. However, it has been noted that the limitations as to how these interventions have been evaluated has led to the existing research having little impact. This study will explore the design strategies and theories that currently exist regarding implementing digital BCTs and will concentrate on why do these types of interventions work, if they work at all?