A randomized, parallel, double-blind, controlled, multicenter clinical trial with two intervention arms. Two groups of participants will be included, both receiving a therapeutic exercise intervention and an educational session on the importance of proper breathing over a 6-week period. One of the groups will additionally perform a home-based controlled breathing exercise protocol. Pre- and post-intervention assessments (6 weeks) will be conducted, along with a follow-up evaluation 4 weeks after completion of the intervention.

The goal is to determine the effectiveness of adding a controlled breathing exercise program to a therapeutic exercise intervention on somatic symptoms in individuals with multiple myeloma

Randomized, parallel, double-blind, controlled clinical trial in which two groups of participants will be included and randomly assigned to one of the two intervention arms:

Therapeutic exercise + initial educational session on proper breathing.

Therapeutic exercise + initial educational session on proper breathing + home-based controlled breathing exercise protocol.

The therapeutic exercise and controlled breathing program will last 6 weeks. During this period, participants will:

Perform three weekly sessions of mobility and muscle-strengthening exercises (two on-site and one home-based) for 6 weeks. The on-site sessions will last between 30 and 40 minutes and will take place at the Rehabilitation Department of Hospital 12 de Octubre in Madrid (a total of 12 on-site sessions-two per week). The home-based exercise program will consist of completing, once per week during the 6-week intervention, a structured session that replicates the logic and technique of the on-site program.

Walk a minimum of 7,000 steps/day or 50 minutes/day, three days per week.

Perform a controlled breathing protocol twice per day at home during the 6-week study period, following the recommendations of the principal investigator. The goal is to integrate slow, gentle, diaphragmatic, nasal breathing into daily life.

The variables to be assessed will include: somatic symptom questionnaire, quality of life, sleep quality, fatigue, anxiety and depression symptoms.

These variables will be evaluated at baseline, at the end of the 6-week intervention period, and again 4 weeks after completing the intervention.

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.

Only the principal investigator will have access to the randomization sequence, thereby maintaining blinding for the rest of the team involved in data collection.

Both groups will receive the same therapeutic exercise program and an educational session with a standardized educational leaflet on the importance of physical activity and proper breathing in daily life, with the aim of minimizing differences in the perceived intervention.

The study will include evaluator blinding, as all assessments will be carried out by an independent investigator who is not involved in the randomization process and is unaware of participants' group allocation. Additionally, statistical analyses will be conducted by a specialized statistician, also blinded to group assignment, thereby ensuring impartiality in the analysis and interpretation of the results.