 Investigators want to identify which patients with COPD get cardiovascular benefit from a PR programme and why others do not. Investigators propose to measure aPWV before and after PR. Investigators will then classify participants as responders or non-responders defined as the presence or absence of a significant improvement in aPWV. Investigators will be collecting demographic and clinical information including daily physical activity level and how effective the PR has been to enable the investigators to identify the characteristics of patients who do, and do not achieve cardiovascular risk reduction in response to PR in COPD. This will inform on better design of PR programmes for people living with COPD. 