My research examines social-cognitive factors that influence and are influenced by participation in physical activity. Current interests include self-perceptions such as self-efficacy, perceived control, self-regulation, and self-determination. I also investigate people’s perceptions about influential others who interact with them (proxy agents) in their pursuit of behavioural objectives. Understanding relationships between these perceptions and behaviour involves laboratory and field-based research. Challenges faced by people navigating life transitions such as moving away from home to attend college or university, rehabilitating from illness, and becoming a parent are of particular interest.