To improve the health and quality of life of breast cancer (BC) patients, researchers are focusing on prehabilitation strategies like physical exercise, preparing patients both mentally and physically for clinical and surgical procedures, potentially reducing complications. Physical exercise is also recognized as pivotal in optimizing chemotherapy. It can improve blood flow and oxygen supply in the microenvironment of the tumor (MT), potentially enhancing chemotherapy effectiveness. Although previous research has shown the benefits of preoperative exercise combined with chemotherapy in various cancer types, including BC, further investigation is needed into the exact effects of prehabilitation exercise (PE) on MT physiology. This study aims to provide valuable insights into the potential benefits of PE for BC patients and its impact on the tumor microenvironment. The hypothesis is that PE in BC patients will improve their quality of life, reduce fatigue, increase muscle mass, decrease fat mass, and enhance physical fitness. Additionally, beneficial acute hemodynamic changes, particularly increased blood flow following PE sessions, and hemodynamic adaptations involving higher levels of oxygenated hemoglobin, increased blood flow, greater oxygen saturation, and a higher metabolic rate of oxygen, are expected. The study will include 76 participants aged 18-65 years, meeting specific criteria such as a diagnosis of hormone receptor-positive BC, no medical contraindications for exercise, no metastatic cancer, and no structured exercise in the last six months. These participants will be randomly assigned to a PE group or a control group. The study will consist of three phases: Phase 1 involves pre-intervention assessments, Phase 2 includes a 4-week PE intervention with three weekly sessions, and Phase 3 encompasses post-intervention and post-surgery assessments. The 4-week PE intervention in Phase 2 will include strength and aerobic training. Quality of life and fatigue assessments will use questionnaires, and measurements will be made for fat mass, lean mass, bone density, and cardiorespiratory fitness. Strength measurements will be taken, and shoulder mobility will be evaluated. Hemodynamics of the MT will be assessed using a hybrid device combining Near-Infrared Spectroscopy and Diffuse Correlation Spectroscopy with ultrasound.