Methods: This study was a randomized controlled clinical trial. After baseline testing is completed, 103 subjects with moderate-severe COPD were randomized into one of three groups: E+VF, E+Heliox and E training only. Follow-up testing was completed at 8 weeks. testing, activity monitoring, and dyspnea measurements. After baseline testing was completed, randomized subjects trained in the Physical Performance Laboratory three times weekly. Exercise prescriptions were standardized and based on data from the exercise stress test.