Inspiratory muscle training in patients with chronic obstructive pulmonary disease: structural adaptation and physiologic outcomes - Ramirez-Sarmiento, A; Orozco-Levi, M; Guell, R; Barreiro, E; Hernandez, N; Mota, S; Sangenis, M; Broquetas, J M; Casan, P; Gea, J (Am J Respir Crit Care Med, 2002)