Developmental shifts in the ability of infants with Down syndrome to produce treadmill steps

Abstract

Background and purpose: In this study, we used a dynamic systems strategy to examine longitudinally the ability of infants with Down syndrome to produce alternating steps when supported on a motorized treadmill.

Subjects: Seven infants participated, ranging in age from 8 to 11 months at entry into the study and 13 to 29 months at their final session.

Methods: Data were collected in the infants' homes on a monthly basis. Testing continued until each subject produced consistent alternating step patterns during three consecutive test sessions.

Results: All infants responded by producing alternating steps, on average, 13.3 months before they walked independently, but they initiated this response at a wide range of chronological ages and significantly later than reported previously for nondisabled infants. Similar developmental variables (control parameters) marked the shift into responsiveness to the treadmill context for all infants with Down syndrome, but these variables differed from those identified for nondisabled infants.

Conclusion and discussion: With age, alternating treadmill stepping became a more stable response, although the relative timing of interlimb coordination (phase lag) of the step cycles remained quite variable across ages. We discuss our results relative to the usefulness of dynamic systems theory in understanding delayed development and the possibilities of pursuing the treadmill paradigm as an intervention approach.