This chapter introduces the research methods and study designs that may be used to assess the impact of exercise/physical activity interventions, including those seeking behaviour change. It outlines the designs that may be used to assess the acute short-term responses and effects of a single bout of exercise and those used to assess training effects and physical activity behavioural changes. It also provides an insight into the factors that need to be considered when designing such studies and how to ensure the attainment of valid, reliable and high quality data.