Non-interventional Cross-over Study to Reduce Items of PROactive Tools Measuring Physical Activity in Chronic Obstructive Pulmonary Disease (COPD)

Inclusion Criteria: * Diagnosis of COPD (Global Initiative for Chronic Obstructive Lung Disease (GOLD) criteria: post bronchodilator forced expiratory volume in one second (FEV1)/forced vital capacity (FVC)\<70%) confirmed with spirometry in stable clinical conditions. For patients recruited during an exacerbation, the diagnosis of COPD should be confirmed in stable conditions. * Current or ex-smokers with a smoking history equivalent to at least 10 pack years. * Able to read and write and to use electronic devices and physical activity monitor. Exclusion Criteria: * Orthopaedic, neurological or other complaints that significantly impair normal biomechanical movement patterns, as judged by the investigator. * Respiratory diseases other than COPD (e.g. asthma). * Cognitive impairment, as judged by the investigator