The study is a randomized trial with crossover of consecutively recruited patients with symptomatic COPD. Each patient will participate in seven visits over a 3-4 week period. At the first visit patients will provide informed consent and then be familiarized with equipment and testing protocols. At visits 2 and 3 patients will inhale 2 puffs of albuterol HFA MDI, and then perform symptom limited incremental exercise on the treadmill or cycle ergometer (randomized order); after a one hour rest, the patient will perform constant work exercise at 80-85% of peak VO2 on the same exercise mode.