Motivational-based intervention research for changing increasing physical activity behaviour in clinical rehabilitation settings has predominantly focused on intervention effectiveness for changing behavioural outcomes. However, the intervention development, delivery and content are not often reported, therefore, limiting the applied utility and replication of the intervention itself. As such, the current research will pilot and feasibly investigate the development of a motivational-based intervention. Doing so will provide a more nuanced understanding for motivating cardiac and pulmonary patients' uptake and adherence to physical rehabilitation activity. Such information would also be crucial for informing a future RCT trial.