Methods.36 patients with stable COPD will be evaluated before and after a 4 month training program. Each evaluation include a stepwise exercise test on an ergocycle up to the individual maximal capacity during which minute ventilation (VE), oxygen consumption (VO2), carbon dioxide production (VCO2), and arterial lactic acid concentration will be measured and the peripheral muscle strength will be determined with the one repetition maximum for eight different muscle groups. Percutaneous needle muscle biopsy from the M.vastus lateralis will be performed before and after the training period in order to determine the fiber-type proportions. Patients are assigned to one of the following three groups (1) endurance training consisted of 20 min exercise sessions on a calibrated ergocycle two times a week, with a target training intensity at 60% of individual maximum oxygen uptake, (2) systemic weightlifting training two times a week with eight different exercises, each session consist of 15 repetitions of each muscle group, (3) combination of endurance training and systemic weightlifting training.