This study addresses an important public health concern; impoverished cognitive function associated with treatment of breast cancer. Due to increased awareness of breast cancer combined with advances in medical care, there are over 2.8 million women living with a history of breast cancer in the U.S. alone. Chemotherapy and adjuvant therapy to remove cancerous tissue can result in deficits in attention, speed of processing, memory, and quality of life. Physical activity has been associated with a number of health benefits for breast cancer survivors including improvements in cognitive function. However, most of the literature is cross-sectional and it is unclear whether acute (single) bouts of physical activity affect cognition and, if they do, how long this effect lasts. This study will be the first, to the investigators' knowledge, to examine the effects of an acute bout of aerobic exercise on cognitive functioning in breast cancer survivors. Specifically, the investigators will determine the effects of a 30-minute moderate intensity aerobic exercise session (treadmill walking) on immediate and one hour follow up changes in measures of processing speed, memory, and executive function. Additionally, accelerometer cut-points for physical activity intensities in breast cancer survivors will be assessed. Finally, the investigators will examine the association of cardiorespiratory fitness and physical activity with changes in cognitive function. Findings from this study will allow researchers to determine whether any acute effects of exercise on cognition are retained over time and therefore have real meaning in the context of one's daily life.