Inclusion Criteria:  Patients with coronary artery disease undergoing in-patient cardiovascular rehabilitation; over 55 years of age. Patients underwent a 6-minute walk test with assessment of the intensity of the exercise  Exclusion Criteria:  no understanding of the German language Patients would not be able to perform a 6-minute walk test, e. g. surgery on the large joints of the lower extremities, unstable heart disease or predominant neurological symptoms.