The role of sustained physical inactivity in the progression of exercise intolerance and muscle depletion in COPD

Background: COPD is characterized by exercise intolerance, muscle depletion, and physical inactivity. The aim of this study was to analyze the role of sustained physical inactivity for changes in exercise capacity and skeletal muscle mass in the course of COPD. Methods: In this cohort study, we measured physical activity level (PAL; total daily energy expenditure / resting metabolic rate) via multisensory armband, FEV 1 , 6-minute walk distance (6MWD), and fat-free mass (FFM; bioelectrical impedance) at baseline and after 3 years in 170 patients with COPD (GOLD stage I–IV) and 30 with chronic bronchitis. Patients were longitudinally classified into ”sustained physical inactivity” (i.e. PAL T0+T1 T0orT1 >1.40). Results: During follow-up, we found a significant decrease in PAL, FEV 1 , 6MWD, and FFM (p 1 , sustained physical inactivity was related to a greater decline in 6MWD and FFM compared to that in patients with some level of activity (difference, 21 m/yr and 0.81 kg/yr). Sustained physical inactivity was not related to an accelerated decline in FEV 1 . Conclusions: Sustained physical inactivity over time promotes a progression of exercise intolerance and muscle depletion in patients with COPD.