Additional Study Information: This study focuses on the effects of aerobic conditioning on cardiovascular function and inflammatory response. Eligible participants will complete an exercise stress test, laboratory visit, and cognitive testing session at three specific time points over the course of the study. Once the initial set of appointments is complete, participants are randomly assigned to one of two conditions for the next 12-weeks. Participants could be in an aerobic fitness condition or a control condition. Regardless of condition, participants will also be provided with a pedometer to use daily for the duration of the study. For female participants, ovulation will be tracked throughout the study.