Introduction
Chronic obstructive pulmonary disease (COPD), a global
health problem, has increased in importance in recent years (Russell et al. 2011). An inflammatory chronic respiratory disease, COPD creates a vicious circle of progressive dyspnoea, reduction of exercise capacity and physical inactivity. Progression of the disease causes deterioration in quality of life and increases the risk of early death (Cooper & Dransfield 2008, Shavelle et al. 2009).