Peripheral muscle weakness is common in persons with chronic obstructive pulmonary disease (COPD) and associated with reduced exercise capacity and mortality. Structured exercise training as part of pulmonary rehabilitation programs is effective in improving exercise capacity and muscle strength, dyspnea, fatigue and health-related quality of life. Traditional pulmonary rehabilitation exercise training includes predominantly a combination of endurance and resistance training. Previous research in COPD has investigated eccentric muscle training as potential alternative training modality characterized by lower oxygen cost and ventilatory requirements compared to concentric exercise which could be particularly beneficial for patients who do not achieve sufficient training intensities due to ventilatory limitations. The objective of this non-inferiority trial is to compare two different exercise-training modalities which are part of the structured exercise training sessions in inpatient pulmonary rehabilitation programs in patients with COPD, and to assess whether eccentric interval downhill stair-walking program is not less effective than continuous or interval cycle ergometer training (currently standard in inpatient pulmonary rehabilitation programs).