Breathing muscle training may boost heart failure recovery

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: 1. Documented clinical diagnosis of chronic Heart Failure with Reduced Ejection Fraction (HFrEF) according to the European Society of Cardiology (ESC) guidelines. 2. Left Ventricular Ejection Fraction (LVEF) less than or equal to 40% documented by echocardiography within the last 12 months. 3. Clinically stable condition for at least 3 months prior to enrollment, with no hospitalizations or major changes in optimized medical therapy. 4. New York Heart Association (NYHA) functional class I to IV. 5. Evidence of inspiratory muscle weakness, defined as a baseline Maximal Inspiratory Pressure (MIP) \< 70% of the predicted value for age and sex. 6. Age greater than or equal to 18 years. 7. Patient must be capable of understanding the protocol instructions and must provide signed written informed consent. Exclusion Criteria: 1. Presence of primary severe pulmonary or respiratory diseases (e.g., Chronic Obstructive Pulmonary Disease \[COPD\] GOLD stage III or IV, active asthma, severe pulmonary hypertension, or restrictive lung disease). 2. Recent myocardial infarction, unstable angina, or coronary artery bypass graft (CABG) surgery within the last 6 months. 3. Severe uncorrected valvular heart disease or complex, uncontrolled ventricular arrhythmias. 4. Orthopedic, neurological, or musculoskeletal limitations that prevent the safe execution of an incremental cardiopulmonary exercise test on a cycle ergometer or the performance of the isometric handgrip protocol. 5. Cognitive impairment or psychological conditions that limit the ability to follow instructions, maintain correct diaphragmatic breathing technique, or properly seal the training device mouthpiece. 6. Current participation in another structured physical rehabilitation or formal sports training program that could confound the systemic results of the intervention. 7. Any acute infectious, inflammatory, or medical condition that, in the investigator's opinion, poses a safety risk during high-intensity training.