The ECCO-study evaluates the efficacy of simultaneous controlled exercise during neo/-adjuvant chemotherapy in breast cancer patients and its effects on neurocognition. In this study the investigators examine the benefits of the individualized high intensity training program on a cancer related cognitive impairment. Changes in patients' cognition are evaluated by neuropsychological testing. Possible structural changes are detected with MRI volumetry. Biomarkers connected to Cancer Related Cognitive Impairment (CRCI) and chemotherapy related inflammatory processes which impair cognition, respectively, will be assessed.