Physical activity can be measured in a number of ways, including direct observation, patient diaries and questionnaires, but one of the most successful are the performance based motion sensors such as pedometers and accelerometers. One such performance based motion sensor is the SenseWear accelerometer. The SenseWear has previously been used in patients with COPD, has been shown to be a reliable measure of physical activity performed in this population, other than those using rolators and it is objectively more accurate than questionnaires and diaries. The hypothesis of this study was that pulmonary rehabilitation leads to a sustained improvement in physical activity in patients with COPD. Physical activity was measured by the daily averaged activity recorded with a SenseWear armband at several time points in the year after a course of pulmonary rehabilitation.