The effects of 6 months of muscle training with an inspiratory pressure load equal to 30% of the maximal inspiratory pressure (PImax) was compared with sham training with a light inspiratory pressure load. In this double-blind randomly assigned study, 67 patients with chronic obstructive pulmonary disease were followed for 6 months. Both groups demonstrated improvements in performance of PImax, respiratory muscle endurance time for breathing against an inspiratory pressure load equal to 66% of PImax, 12-minute distance walk, and dyspnea. The treatment group did not demonstrate significant effects beyond those observed in the control group. Improvements in performance were related to improved coordination of the inspiratory muscles and desensitization to dyspnea.