A recent consensus study suggested that understanding the impact of exercise on the tumor microenvironment and therapy effectiveness is paramount and should be considered as a research priority. Therefore, the research team intends to address some of the scientific challenges proposed, which represent clear gaps in the current knowledge. The investigators propose a randomized controlled trial conducted during all neoadjuvant treatment duration that aims to evaluate and compare the effects of two different exercise protocols (aerobic and resistance training) against a relaxation control group on Ki-67% changes as the main outcome in breast cancer patients. Secondary outcomes will be body composition; resting metabolic rate; physical fitness; quality of life, fatigue, depression/anxiety; accelerometry data (physical activity levels, sedentary time); sleep quality; tumor biology (size, hypoxia, and immune profile); glycemic, lipid, and inflammatory profile. This project will help not only researchers with the design of future exercise intervention protocols but will also help exercise physiologists in the decision-making process when defining training programs. Moreover, the investigators expect that this research program will encourage more cancer patients to exercise. The team expects that patients with breast cancer engaging in structured exercise will show a more marked decrease in Ki-67, tumor size, and hypoxia and increase the tumor-infiltrating lymphocytes (TILs) compared to controls. The investigators anticipate a more noticeable decrease in the preoperative endocrine prognostic index (PEPI) score and in the Residual Breast Cancer (RCB) in both training groups (respectively with hormonal and chemotherapy). Also, frequent declines in physical fitness are expected to be mitigated in exercisers. It is hypothesize that aerobic training will ameliorate cardiorespiratory fitness and fat mass, while the effects of resistance training will be more relevant for muscle strength, muscle mass, and bone health. Both exercise groups will show greater improvements in quality of life, fatigue, depression, anxiety, and sleep quality. Regarding glycemic, lipid, and inflammatory profiles, the investigators expect to see more favorable changes in both training groups, with a more evident decrease in fasting glucose and insulin, HbA1c%, total and LDL-cholesterol, and triglycerides, and the increase in HDL-cholesterol. The increase in C-reactive protein (CRP), tumor necrosis factor -α (TNF-α), interleukin-6 (IL-6), IL-8, IL-1β, IL-1ra, and insulin-like growth factor-1 (IGF-1) and the decrease in brain-derived neutrotophic factor (BDNF), IL-12p70, IL-10, oncostatin M will be smaller in exercise groups.