Effectiveness of the Aktivplan Digital Intervention (ACTIVE-CaRe Pilot)

The goal of this clinical pilot / feasibility study is to determine the feasibility of conducting a large-scale clinical effectiveness trial of the aktivplan digital intervention in cardiac rehabilitation patients. The main questions this study aims to answer are: * Is it feasible to conduct a large-scale (fully powered) effectiveness trial of the aktivplan digital intervention? * What is the usability, user experience and user acceptance of the aktivplan digital intervention? Patients enrolled in a phase II cardiac rehabilitation programme will be randomly allocated to either the intervention group (aktivplan digital intervention) ot the usual care control group and followed-up for 10 weeks after discharge from cardiac rehabilitation. Patients in the intervention group will be given the aktivplan application (app) on their smartphone. A rehabilitation professional will plan a personalised heart-healthy physical activity plan together with the patient and enter it to the aktivplan app. The patient will be asked to follow their personal physical activity plan for 10 weeks, using the aktivplan app to document completed physical activity sessions. Patients in the control group will receive the usual standard of care without the aktivplan digital intervention. Researchers will analyse information such as the rate of recruitment, participant attrition, data completeness and technical stability of the app to determine the feasibility of conducting a large-scale clinical effectiveness trial.