Atsushi Hayata,1 Yoshiaki Minakata,2 Kazuto Matsunaga,3 Masanori Nakanishi,1 Nobuyuki Yamamoto1 1Third Department of Internal Medicine, Wakayama Medical University, School of Medicine, Wakayama, 2Department of Respiratory Medicine, National Hospital Organization Wakayama Hospital, Wakayama, 3Department of Respiratory Medicine and Infectious Disease, Graduate School of Medicine, Yamaguchi University, Yamaguchi, Japan Background: Physical activity (PA) is impaired from the early stages of COPD, is associated with a worsening of disease prognosis, and causes COPD patients to restrict their daily activities in order to avoid breathlessness. The development of a simple tool to estimate physical activity level (PAL) could be useful for the management of COPD. Objectives: We investigated the differences in PA according to the modified Medical Research Council (mMRC) grade in patients with COPD. Methods: A cross-sectional study was performed on stable outpatients with COPD. PA was measured for 2 weeks using a triaxial accelerometer, and dyspnea grade was evaluated in all patients using the mMRC scale. Results: Ninety-eight patients were recruited. Significant differences in PA duration were observed at all intensities according to the mMRC grade. Despite treatment with controller medications, 59.2% of COPD patients had low PAL, which was