"Moving Together" (Juntas en Movimiento) is a hospital-based, comprehensive, and personalized exercise service designed for women diagnosed with breast cancer. This implementation study aims to evaluate the feasibility, safety, and impact of integrating a free, tailored exercise program into routine clinical care at Hospital Clínico San Carlos in Madrid, Spain.

The program offers multiple participation options-supervised in-person, supervised online, autonomous at home, or autonomous at a fitness center-allowing patients to choose based on their preferences, limitations, and treatment phase (pre-surgery, during chemotherapy/radiotherapy, or survivorship). All exercise options are adapted to individual needs and include aerobic and resistance training components.

The study uses a real-world implementation science approach, guided by the Consolidated Framework for Implementation Research (CFIR), to assess clinical, physical, and psychological outcomes such as quality of life, cardiorespiratory fitness, muscle strength, body composition, and adherence to physical activity. Data are collected through clinical records, physical assessments, validated questionnaires, and wearable technology.

This pioneering initiative in Spain seeks to establish exercise as a standard complementary therapy in oncology care, bridging the gap between scientific evidence and clinical practice, and promoting long-term health and well-being in breast cancer patients.

"Moving Together" (Juntas en Movimiento) is an implementation research project that evaluates the integration of a comprehensive, free, and personalized exercise service into the clinical care of women with breast cancer. The service is embedded within the Breast Unit of Hospital Clínico San Carlos (Madrid, Spain) and is developed in collaboration with King Juan Carlos University and GO fit Vallehermoso.

The program is designed to be inclusive and adaptable, offering four participation modalities:

• Supervised in-person sessions at a fitness center.
• Supervised online sessions via video conferencing.
• Autonomous home-based training with structured guidelines.
• Autonomous training at a gym with tailored routines.

Patients can join the program at any stage of their cancer journey-before surgery, during chemotherapy or radiotherapy, or in the survivorship phase. The exercise protocols are adapted to each phase and personalized based on clinical status, physical capacity, preferences, and daily symptoms. Supervised sessions include real-time heart rate monitoring and are delivered in small groups to foster social support.

The implementation follows the CFIR model, analyzing internal and external factors that influence adoption, sustainability, and scalability. The program is supported by interdisciplinary collaboration among oncologists, gynecologists, exercise scientists, and clinical staff. Healthcare professionals receive specific training to promote exercise as part of cancer care.

Assessments include:

• Clinical data (tumor type/stage, treatments, biomarkers).
• Physical evaluations (body composition, strength, flexibility, balance, cardiorespiratory fitness).
• Psychological and behavioral measures (quality of life, physical activity levels, perceived barriers/benefits, adherence).

Data are collected using REDCap and wearable devices (e.g., accelerometers, heart rate monitors). Behavioral change strategies, including the COM-B model and the PADEX checklist, are applied to enhance motivation, self-efficacy, and long-term adherence.

The program also fosters a supportive community through workshops, group sessions, and family-inclusive events. It aims to humanize care, empower patients, and create a sustainable model for integrating exercise into oncology services.

This initiative not only improves patient outcomes but also creates a real-world research platform to explore the effects of exercise across different cancer stages and patient profiles. Future randomized controlled trials will be embedded within the service to refine exercise prescriptions and optimize clinical impact.

Inclusion Criteria:

• Women aged 18 years or older.
• Diagnosed with any type and stage of breast cancer.
• Receiving care at Hospital Clínico San Carlos (Madrid, Spain).
• Willing and able to provide informed consent.
• Eligible to participate in physical activity based on clinical evaluation.

Exclusion Criteria:

• Medical contraindications to physical exercise.
• Severe uncontrolled conditions (whether related to cancer treatment or not).
• Diagnosis of recurrent breast cancer.
• Refusal or inability to sign the informed consent form.

Women aged 18 years or older diagnosed with any type and stage of breast cancer, receiving care at Hospital Clínico San Carlos (Madrid, Spain). Participants may be at any phase of treatment (pre-surgery, during chemotherapy or radiotherapy, or in the survivorship phase). The study includes a diverse population with varying clinical profiles, physical capacities, and personal circumstances. The exercise program is inclusive and personalized, allowing participation regardless of treatment type or modality, as long as there are no medical contraindications to physical activity.