Patients will be randomized to receive either the assisted exercise (n=60) or voluntary exercise (n=60) group. Subjects in the voluntary group will exercise on a stationary recumbent exercise cycle and pedal at their preferred rate. Subjects in the assisted exercise group will cycle on the same stationary exercise bike; however, a motor will provide assistance to the patient in order to maintain a pedaling rate 35% greater than their voluntary rate. Subjects in the exercise groups will complete 45 minute to 1-hour sessions, three times per week for eight weeks. The control group will be asked to complete all exercise, body composition and fMRI testing similar to the exercise groups.