Inclusion Criteria:  Age ≥18 years. Participant in an exercise-based cardiac rehabilitation program in either hospital or municipality setting. Access to a personal mobile phone and Danish telephone number. Able to walk 3 meters without assistance.  Exclusion Criteria:  Insufficient Danish language proficiency to read and understand text messages and questionnaires. Patients cognitively or mentally unable to participate. Terminal patients and patients with a life expectancy of less than 3 months.