title: Authors' reply.
authors: Department of Pulmonary and Critical Care Medicine, Hallym University Kangdong Sacred Heart Hospital, and Clinical Research Center for Chronic Obstructive Airway Diseases, Seoul, Republic of Korea.
authors: Changhwan
authors: C
authors: Kim
authors: Yong Bum
authors: YB
authors: Park
mesh_terms: D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology*; D006801:Humans; D008297:Male; D005082:Physical Exertion / Q000502:physiology*; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D016138:Walking / Q000502:physiology*