The Study for the Reliability and Validity of Incremental Shuttle Walking Test for COPD Patients in Korea

Investigators will perform this study to validate shuttle walking tests in korean patients with chronic obstructive pulmonary disease. This study will be performed as multi-center prospective observational correlation study in ulsan university hospital and asan medical center. 18 patients will be enrolled in each hospital. When then visit, patients will perform questionnaire and laboratory study for baseline characteristics. After that, patients select memo, in which order for the exercise stress test with cycle, 6 minutes walking test and shuttle walking test will be written. Along that order, patients will perform each study at every two day in a week. Investigators will analyze correlation 6 minutes walking test and shuttle walking test with exercise stress test. To analyze reliability in shuttle walking test, patients will shuttle walking test in two times. Researchers will analyze correlation between them.