Patients: Patients studied will be those with an acute exacerbation of COPD deemed sufficiently unwell by the duty medical registrar to warrant hospital admission. Exclusion criteria will include significant co−morbidity that could limit exercise training, and attendance at a pulmonary rehabilitation programme in the preceding year. In−patient treatment will include standard therapy (nebulised bronchodilators, oxygen, non−invasive ventilation (if required), antibiotics and a 1−2 week course of oral prednisolone 30−40mg daily). On hospital discharge, patients will be allocated either to the early pulmonary rehabilitation (EPR) group (within 7 days of hospital discharge) or usual care (UC) i.e. routine outpatient and primary−care follow−up.