Effects of NPV-exercise training vs. control on health-related quality of life. A. Individual changes of SGRQ total scores in both groups before and after the 12-week course (Control, n = 10; NPV-exercise, n = 18). B. Comparisons of St. George’s Respiratory Questionnaire (SGRQ) total score (ΔSGRQ; changes from the base line after 12 weeks mean ± SD) between both groups (Control, n = 10; NPV-exercise, n = 18).