ERBB2 and heart failure: - HER2 negative breast cancer - Patients with metastases - Heart failure (LVEF ≤ 50%) - Resting oxygen saturation (SaO2) ≤ 92% - Autoimmune disease (systemic lupus erythematosus, rheumatoid arthritis) - Symptomatic osteoarthritis, cardiovascular disease (angina or uncontrolled hypertension) or lung disease (chronic obstructive pulmonary disease) - Patients suffering from malnutrition (BMI < 18 kg.m−2) or weight loss of >10% during the previous 3 months - Patients with psychiatric or cognitive disorders deemed unsuitable for physical activity - Pregnant or breastfeeding patients