ACE and chronic obstructive pulmonary disease: To strengthen the design of the trial we used a stratified medicine approach, selecting patients with quadriceps weakness using the cutoff that has been found to be associated with increased mortality in COPD.5 Quadriceps endurance, measured by repetitive magnetic stimulation, was used as the primary outcome due to the association of reduced ACE levels with greater endurance in healthy subjects13 and the advantages of a nonvolitional test in the context of a population with severe airflow limitation.22