This chapter begins with a basic overview of inoculation theory before turning to proposed applications and theoretical development opportunities in the contexts of physical activity, sport, and exercise. It identifies a diverse set of inoculation message approaches that have the potential to be successful. The chapter suggests that inoculation messages can confront issues directly, indirectly, or by re-framing the issue. It demonstrates how inoculation messages can target others or the self. The chapter deals with a guided inoculation message example, reflecting the inoculation message features we highlighted previously. The example message is designed to keep those who have started an exercise program committed to the exercise program. The purpose of the forewarning is to overtly make clear to the message receiver that the attitude or behavior in place is indeed vulnerable and will likely face challenges.