Aims : to provide an update on the latest knowledge in the field about respiratory muscle dysfunction, evaluation and management; to discuss the potential respiratory muscle dysfunctions or adaptations in various pathological contexts; to present the respiratory muscle responses to exercise and their role in exercise limitations and symptoms; and to improve understanding of the effects of critical illness on respiratory muscle structure and function, the clinical consequences of respiratory muscle weakness and the potential therapeutic options for improving muscle function in chronic obstructive pulmonary disease (COPD).