Patients with COPD often have limitations to physical performance. There are several tests for evaluating physical performance, unfortunately many of them can be time consuming and require specialized equipment an substantial space. Short physical performance battery is a simple test that requires little resources and can be performed both at institutions and in the homes of patients. SPPB has high predictive abilities in identifying older adults at greater risk for mortality, nursing home admission, hospitalization, and incidence of disability. The investigators would like to evaluate possible changes in the SPPB score after a 4-week rehabilitation program. The investigators would also like to look at possible relationships between the SPPB and other physical performance measures, dyspnea, anxiety, depression, fatigue, and health related quality of life.