Patients’ study eligibility was determined through medical history and physical examination. Afterward, patients completed a symptom-limited, baseline cardiopulmonary exercise test (CPET) on a treadmill; the 6MWT; and HRQoL questionnaires to determine their cardiorespiratory function, functional capacity, and patient-reported HRQoL, respectively. The CPET was a modified Naughton protocol that increased the speed or grade of the treadmill every 2 min (e-Table 1). The first three stages were increased gradually so that the metabolic equivalent (MET) requirements would be small.38 This allowed patients with severe exercise intolerance to complete at least two to three stages prior to the introduction of a grade component. The rest of the protocol increased speed or grade to approximate one MET increment per stage. This protocol is similar to previous studies38,39; however, walking at 2 miles per h was extended (stage 6) by increasing grade rather than speed. A standardized 6MWT was conducted around a circular “course” measuring 80 m, rather than a hallway, as described in the American Thoracic Society Guidelines.40 Investigators administering the CPET, 6MWT, and questionnaires were blind to randomization at baseline. Patients using supplemental oxygen (O2) at the baseline visit performed the CPET breathing a hyperoxic gas mixture (fraction of inspired O2 of 40%). During the subsequent 6MWT, the O2 flow rate was set at 6 L/min. Follow-up visits for these patients were performed using the same concentration of supplemental O2. Patients were then randomized to either an aerobic exercise training (AET) plus education intervention (education/exercise combined [EXE]) group or an education-only (EDU) control group. Identical educational lectures were given to both groups over 10 weeks. The education sessions consisted of weekly 1-hour lectures on anatomy and physiology, lung disease processes, medication use, oxygen therapy, sleep disorders, preventing infection, airway clearance, interpreting pulmonary function tests, energy conservation, panic control, relaxation techniques, breathing retraining, community resources, advance directives, social well being, nutrition, and benefits of exercise. Only patients in the EXE group participated in 24-30 additional sessions of medically supervised treadmill walking for 30-45 min per session over the same 10-week period. A target exercise intensity of 70% to 80% of each patient’s heart rate (HR) reserve obtained from the baseline CPET was used to guide each exercise session. Target HR range was calculated as: 0.7 and 0.8 × (peak HR − resting HR) + (resting HR), in accordance with the method of Karvonen.41 Treadmill speed and/or grade were continuously adjusted to keep each patient within or as close as possible to their target HR range. Perceived dyspnea, and exertion, O2 saturation, and HR were continuously monitored throughout the sessions. The CPET, 6MWT, and HRQoL questionnaires were repeated following the 10-week intervention period in both groups.