This study will follow physical activity following pulmonary rehabilitation longitudinally over 48 weeks. Investigators will use a state-of-the-art accelerometer, to analyze minutes walking per day as the primary outcome, rather than vector magnitude units (VMU) or estimated steps per day. Investigators will explore potential factors influencing this important outcome, including baseline activity levels, demographic variables, changes in exercise capacity, psychological variables, and self-efficacy scores. Finally, Investigators will evaluate the rate of change (trajectory) in physical activity over approximately six months after pulmonary rehabilitation. There are limited data suggesting it takes time for the translation of increased exercise capacity into increased physical activity to occur.