The purpose of the study was to examine the effectiveness of two modes of exercise on depression in adolescents with Down syndrome (DS). Twelve participants randomly completed one of two exercise interventions. The interventions were: 1) Voluntary Cycling (VC), in which participants cycled at their self-selected pedaling rate 2) Assisted Cycling (AC), in which the participants' voluntary pedaling rates were augmented with a motor to ensure the maintenance of 80 rpms. In each intervention, the participant completed three cycling sessions each week for a total of eight weeks. Depression scores did decrease or improved after both AC and VC, but not significantly. There was a greater mean improvement for participants in the AC 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 mental health improvements found after an acute bout of assisted cycling in adolescents with DS.