The purpose of the study was to examine the effectiveness of two modes of exercise on the lower body strength and aerobic capacity in adults with Down syndrome (DS). Six participants randomly completed one of two exercise interventions: 1) Voluntary Cycling (VC), where participants cycled at their self-selected pedaling rate and 2) Assisted Cycling Therapy (ACT), where the participants' voluntary pedaling rates were augmented by 35% with a motor. In each intervention, the participant completed three, 30-minute cycling sessions each week for a total of eight weeks. The Six-Minute Walk Test (6MWT) was used to evaluate the distance each participant was able to complete in six minutes before and after the intervention. There was a significant increase in the distance and velocity of the participants after the intervention with a greater mean improvement for participants in the ACT group than VC when analyzing total score and t-score. Future research will include a greater sample size and control group to reach significant results as well as try and reveal the mechanisms involved in these physical health improvements found after an acute bout of assisted cycling in adults with DS.