This study aims to compare effects of inspiratory muscle training added by aerobic training to aerobic training alone in heart failure patients with inspiratory muscle weakness. To do so, strength and endurance of inspiratory muscles, functional capacity, quality of life, heart rate variability and sleep apnea evaluations will be conducted in patients with heart failure.

A sample comprising at least 30 individuals is necessary. These subjects will be randomized in two groups, one consisting of inspiratory muscle training plus aerobic training, whereas the other will consist of the aerobic training alone.

This prospective, randomized, controlled trial will include patients with the diagnosis of chronic heart failure attributable to left ventricular systolic dysfunction who will be recruited from the Heart Failure Clinic.

Entry criteria for the study are a previous history of symptomatic heart failure caused by left ventricular systolic dysfunction, inspiratory muscle weakness (PImax < 70% of the predicted), and clinical stability, including no change in medications for the past three months.

Exclusion criteria will be unstable angina, myocardial infarction, or cardiac surgery within the previous three months, chronic metabolic, orthopedic, or infectious diseases, treatments with steroids, hormones, or cancer chemotherapy, history of exercise-induced asthma, chronic obstructive pulmonary disease and smokers will be not recruited.

The protocol was approved by the Committee for Ethics in Research of Hospital de Clinics de Porto Alegre and Ijuí University and all subjects are required to sign an informed consent form.

Variables will be measured by strength and endurance (progressive and constant load), 6-min walk test, cardiopulmonary exercise testing, quality of life questionnaire, evaluation of the heart rate variability and sleep apnea.

The inspiratory muscle training plus aerobic training will consist of cycle exercise (3 sessions/week) and inspiratory exercise by using Threshold equipment for 30 min, 7 times per week, whereas aerobic training group will perform only cycle exercise. Both treatments will last 12 weeks.

Inclusion Criteria:

• previous history of symptomatic heart failure caused by left ventricular systolic dysfunction
• inspiratory muscle weakness (PImax < 70% of the predicted)
• clinical stability, including no change in medications for the past three months

Exclusion Criteria:

• unstable angina
• myocardial infarction, or cardiac surgery within the previous three months
• chronic metabolic, orthopedic, or infectious diseases
• treatments with steroids, hormones, or cancer chemotherapy
• history of exercise-induced asthma, chronic obstructive pulmonary disease
• smokers