This study will primarily identify longitudinal associations between cardiorespiratory fitness (CRF) and cognitive function pre- (baseline) to post-chemotherapy (\ 3 months). This will be a prospective study of 50 BCS. We hypothesize that breast cancer patients undergoing chemotherapy who have higher levels of CRF at baseline will have significantly improved measures of attention, executive function, and memory post-chemotherapy. In addition, the exploratory aims will examine the longitudinal associations between physical activity (PA) and cognitive function from pre- to post-chemotherapy and explore the associations between inflammatory and non-inflammatory biomarkers and CRF with cognitive function.