This chapter introduces individual and environmental factors associated with physical activity. It presents strategies to identify and overcome individual and environmental barriers to physical activity. The chapter explains how physical activity outcome expectations should be communicated to clients. It presents various behavioural strategies to promote physical activity within exercise referral schemes. The UK Physical Activity Guidelines provide guidance from the chief medical officer on the amount of physical activity people should do on a daily or weekly basis. Epidemiological evidence has shown that being active is not easy and something most people do not do enough of. Research that has informed our understanding of factors that influence physical activity behaviour has been derived from both cross-sectional and longitudinal studies. Social support is correlated with physical activity in a range of individuals, particularly from family and peers with similar health concerns