Reduced respiratory muscle strength in individuals with Down syndrome (DS) may affect speech respiratory variables such as maximum phonation duration (MPD), initiation volume, and expired mean airflow. Researchers randomly assigned adolescents with DS (N = 28) to either 12 weeks of swim training (DS-ST) or a control group (DS-NT). Repeated measures MANOVA demonstrated a significant increase in MPD for DS-ST participants from pretest to posttest, t(11) = –3.44, p = 0.006, that was not maintained at follow-up, t(11) = 6.680, p < .001. No significant change was observed for DS-NT participants across time, F(2, 11) = 4.20, p = 0.044. The lack of long-term change in DS-ST participants may be related to the relatively short training period.