RecruitingBehavioural interventionGuided Episodic Future Thinking to Increase Physical Activity Adherence and Promote Healthy Brain AgingThe goal of this behavioral clinical trial is to learn how to increase physical activity in mid-life adults. Specifically, can guided imagery that includes creating mental pictures increase excitement about working out. Participants will be asked to complete testing at the beginning of the study, following 6-weeks of an in-person exercise program, and 6-weeks after finishing the exercise program. Testing will include an exercise test, MRI, questionnaires, computer tasks, and a blood draw.