This is a prospective, randomized, controlled mono-center study investigating the effects of a combined, supervised aerobic exercise and resistance training in female patients with newly diagnosed, therapy-naive triple-negative breast cancer (TNBC, stage I-III) between 18 and 50 years of age scheduled for anthracycline-based chemotherapy and immunotherapy with checkpoint inhibitors. All patients will receive smart watches for rhythm monitoring. Patients will be randomized (1:1) into a control group, receiving 24 weeks of standard exercise recommendations during neoadjuvant therapy, and an intervention group receiving 24 weeks of home-based, video-supervised exercise training consisting of endurance and resistance training. The primary endpoint is the change of peak oxygen consumption (VO2peak) between baseline and 24 weeks in the groups. Secondary endpoints include changes of physical function (short physical performance battery, SPPB), as well as cardiac biomarkers, quality of life, and changes of strength of the upper and lower body between baseline and 24 weeks. In addition, variables of cardiopulmonary exercise testing (CPET), resting and stress echocardiography, and burden of atrial fibrillation (AF) will be assessed. All changes in variables will be analyzed from baseline until 52 weeks as well. Both groups will receive standard exercise recommendations after 24 weeks and will be followed-up by clinical examination after 52 weeks. Echocardiographic variables (at rest and during exercise), quality of life, CPET, SPPB, strength testing, burden of AF, and cardiac biomarkers will be assessed. Changes between the end of the intervention period 24 weeks after diagnosis and the end of follow-up after 52 weeks will be analyzed. In addition, changes in variables between baseline and 52 weeks will be analyzed. As an exploratory endpoint the incidence of cancer therapy-related cardiac dysfunction (CTRCD) and immune-checkpoint inhibitor- associated myocarditis (ICI-myocarditis) will be assessed after 24 and 52 weeks.