IntroductionVery few studies have examined patterns of physical activity (PA) during a pulmonary rehabilitation (PR) program in people with COPD. AimsTo compare the patterns of PA in: 1) the week before commencing PR (pre-PR) with a week during PR (PR week); 2) PR days and non-PR days during a PR week; 3) pre-PR and the week following PR completion (post PR). MethodsThis was a multicenter, prospective cohort study. Participants attended twice weekly supervised PR for 8-12 weeks. Daily step count (primary outcome), time in light activities, time in moderate to vigorous PA (MVPA), total sedentary time and sit-to-stand (STS) transitions were measured using a thigh worn accelerometer for seven days, at each assessment time point: pre-PR, PR week and post PR. Results29 participants, mean age (SD) 69years(7), FEV1 53%pred(16). The PR week compared to pre-PR, showed higher daily: step count (mean difference (95%CI)), 941steps(388–1494); and MVPA, 11mins(6–15), with no difference in: time in light activities, -1min(-6–5); total sedentary time, 7mins(-21–36); or STS transitions, 0(-5–6). PR days compared to non-PR days showed higher: step count, 2810steps(1706–3913); time in light activities 11mins(1–20); time in MVPA, 27mins(17–35) and STS transitions, 8(4–12), with no difference in total sedentary time: -33mins(-80–15). There were no differences in any PA measures post-PR compared to pre-PR (p<0.05). ConclusionDaily step count and time spent in MVPA increased significantly during the PR week, solely due to increased PA on days participants attended PR.