Objectives: To evaluate regional lung ventilation distribution in patients suffering from chronic heart failure (CHF) after completing inspiratory muscle training (IMT) and correlate it with functional capacity and quality of life among these individuals. Methods and Results: Nineteen CHF patients were randomly assigned to two groups: Control and IMT. Before and after muscle training, subjects were submitted to assessment protocol for respiratory muscles, digital spirometry, optoelectronic plethysmography (OEP), the six-minute walk test (6MWT) and a quality of life questionnaire (MLHFQ). There was no difference in lung function following the 12-week training period in either group. However, the IMT group showed an increase in actual and predicted MIP, higher MLFHQ score and greater distance walked in the 6MWT, as well as a reduction in the Borg scale after the 6 MWT in relation to the control. For the OEP, IMT group members exhibited higher values for total chest wall volume (Vcw), abdominal rib cage volume (Vrc,a) and abdominal volume (Vab) when compared to the control. Conclusions: For patients with CHF, IMT proved efficient in improving muscle strength, functional capacity and quality of life. The present study also analyzed the distribution behavior of lung volumes for the thoracoabdominal system in this population, showing that larger abdominal rib cage and abdomen volumes may result in more effective diaphragmatic contraction.

Inclusion Criteria:

• sedentary adults diagnosed with functional class II and II CHF in accordance with the New York Heart Association (NYHA);
• in stage B or C according to American College of Sports Medicine guidelines;
• with left ventricle ejection fraction lower than 45% (evaluated by echocardiogram in a period ≤ 1 year);
• cardiomegaly confirmed by increased left ventricle end-diastolic (LVDD) and end-systolic diameter (LVESD) associated with a cardiac index (CI) >0.5 according to chest X-rays;
• inspiratory muscle weakness (MIP <70% of predicted values);
• clinical stability with no change in medication for at least three months and sedentary (no regular physical activity performed in the previous six months or not accumulating 30 minutes or more of moderate physical activity - 3 to 6 METs - on most week days).

Exclusion Criteria:

• patients exhibiting unstable angina, myocardial infarction or prior heart surgery up to three months before beginning the investigation;
• orthopedic, infectious or chronic metabolic diseases;
• treatment with steroids, hormones or chemotherapy;
• ratio between forced expiratory volume in one second and forced vital capacity (FEV1/FVC) < 70% of predicted, characterizing an obstructive respiratory disorder;
• respiratory diseases, smokers and ex-smokers with a history of cigarettes/day for more than 10 years.