Simple breathing exercises could boost heart health in blood cancer patients

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

Inclusion Criteria: * Age ≥ 18 years. * Confirmed diagnosis of multiple myeloma, currently undergoing active treatment with daratumumab, and under clinical follow-up by the Hematology Department of HU12O. * Explicit medical indication for supervised physical activity issued by the responsible hematologist and documented in the medical record. * No scheduled hematopoietic stem cell transplantation within the 60 days following the planned start date of the intervention (verified through medical record review). * Functional status of ECOG 0-2 (Eastern Cooperative Oncology Group), assessed by a healthcare professional from the Hematology Department, ensuring the ability to perform at least basic and light instrumental activities of daily living, including independent ambulation. * Access to a smartphone with stable internet connection, required for monitoring and recording adherence to the intervention. * Ability to provide written informed consent, demonstrating understanding of the study's nature, purpose, and procedures. Exclusion Criteria: * Medical risk contraindicating exercise or breathing techniques: * Clinically significant cardiovascular disease, including:decompensated heart failure, acute myocardial infarction within the past 3 months, clinically uncontrolled arrhythmias, unstable angina, acute-phase deep vein thrombosis or pulmonary embolism, pacemakers or cardiac devices whose monitoring parameters contraindicate supervised exercise according to cardiology. * Severe decompensated respiratory disease, such as acute exacerbation of COPD, severe respiratory insufficiency, or persistently low resting oxygen saturation \< 90% (not correctable). * High musculoskeletal or bone risk: * Extensive lytic bone lesions, high risk of pathological fracture, or unstable vertebral fracture, documented by imaging or based on the assessment of the Hematology/Traumatology specialist. * Uncontrolled pain that prevents safe participation in an exercise program. * Hematologic or systemic conditions contraindicating exercise: * Severe anemia: hemoglobin \< 9 g/dL in women or \< 8 g/dL in men (latest laboratory test ≤ 14 days). * Active systemic infection contraindicating exercise, fever ≥ 38 °C, or neutropenia \< 0.5 × 10⁹/L. * Severe cytopenias that, in the opinion of the hematologist, preclude moderate exercise. * Functional or procedural limitations: * Inability to remain in the supine position for ≥ 5 minutes, required for part of the breathing intervention. * Confirmed pregnancy or reasonable suspicion of pregnancy. * Severe cognitive impairment, major psychiatric disorders, or neurological diseases that limit understanding of the procedures or safe participation. * Significant difficulty understanding the language (spoken or written) that prevents following essential instructions or completing validated questionnaires.