Effect of Practice on a Novel Task—Walking on a Treadmill: Preadolescents With and Without Down Syndrome

The authors propose that preadolescents with Down syndrome (DS) initially adapt to contexts that challenge their stability by increasing stiffness and impulse but, with practice, they will continue to adapt, but in the opposite direction, by decreasing stiffness and impulse. The purpose of this study was to explore changes in stiffness and impulse values of participants with DS after sufficient, task-specific practice distributed over time in a motivating environment. Eight preadolescents with DS and 8 preadolescents with typical development (TD) participated. At pretest and posttest visits, participants walked over ground at their preferred speed and on a treadmill at 40%, 75%, and 110% of their over-ground speed. Practice included 4 sessions of treadmill walking at 75% of over-ground speed for 12 minutes, with approximately 800 strides per leg per session. The preadolescents with DS had reduced stiffness and impulse values following walking practice while still producing kinematic patterns uniquely different from those of their peers with TD. Preadolescents with DS can adjust their dynamic resources, both upward and downward. With practice, they can maintain stability while improving efficiency, producing stiffness and impulse values more like those of their peers with TD.