The purpose of this study is to determine the important change in the Short Physical Performance Battery (SPPB) when used in patients with lung disease. The SPPB is a simple physical test that measures balance and the functioning of the legs. It has been widely used in healthy elderly populations and predicts hospital admission and the onset of disability. The SPPB has not previously been used in patients with lung disease, and it is not clear what change in this test is considered meaningful and worthwhile by patients or doctors (the minimal clinically important difference: MID). Knowing what the MID for the SPPB will allow researchers and doctors to evaluate the effectiveness of current and new treatments, and to detect improvement or deterioration in the condition of patients.

Inclusion Criteria:

• All patients entering pulmonary rehabilitation

Exclusion Criteria:

• Any patient in whom mobility and lower limb function have been significantly affected by a neuromuscular cause, severe peripheral vascular disease or amputation.
• Any patient whom the chief investigator feels it is unsafe to exercise (e.g. unstable cardiac disease).

All chronic respiratory disease patients referred for pulmonary rehabilitation.