The aim of this observational study is to translate the principle of individualised exercise prescription into the evaluation of daily absolute and relative intensity physical activity. The main questions this study aims to answer are: * Phase 1: What does physical activity (intensity) mean to people with COPD? * Phase 2: Are there differences between time spent in absolute and relative physical activity for people with COPD? Phase 1 Participants will take part in semi-structured interview (30-45 minutes) about living with COPD and perceptions of physical activity and how they perceive intensity. This will also include photovoice and photo-elicitation. Demographic information will be recorded and participants will also complete several respiratory symptom questionnaires. Phase 2: Participants will take part in physical activity testing before and after pulmonary rehabilitation while wearing physical activity monitors. Demographic information will be recorded and participants will also complete several respiratory symptom and physical activity questionnaires. Participants will also wear the physical activity monitors for 8 days after the pre-testing sessions and after their final pulmonary rehabilitation class. Sub-study: Participants will be asked to take images of barriers during physical activity, facilitators during physical activity, feelings during physical activity and types of physical activity they take part in for 8 days after their final pulmonary rehabilitation class. Participants will then take part in a semi-structured interview about the images their have taken while doing physical activity.