title: Chicken or egg: physical activity in COPD revisited.
authors.forename: M I
authors.initials: MI
authors.lastname: Polkey
authors.forename: K F
authors.initials: KF
authors.lastname: Rabe
mesh_terms: D018450:Disease Progression; D015444:Exercise; D005081:Exercise Therapy / Q000379:methods*; D017079:Exercise Tolerance / Q000502:physiology; D005541:Forced Expiratory Volume; D006801:Humans; D018482:Muscle, Skeletal / Q000378:metabolism; D018384:Oxidative Stress; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis* / Q000503:physiopathology*; D012307:Risk Factors; D012907:Smoking; D013997:Time Factors; D016896:Treatment Outcome