Ulrich, D.A. & Ulrich B.D. (March, 1999). Treadmill training
facilitates the onset of walking in infants with Down syndrome.
Paper presented at the 32nd annual Gatlinburg Conference
on Research and Theory in Mental Retardation & Developmental
Disabilities, Charleston, SC.
Introduction. Pediatric physical therapists are being challenged
to document the functional outcomes of their therapeutic practices.
When asked, parents of infants with Down syndrome (DS) typically identify
independent walking as an extremely valued outcome for their child.
Although there is great variability in the age of onset of most motor
milestones in all children, a review of multiple studies involving
infants with DS would suggest that 24 months of age is a very common
age for walking to occur. The onset of locomotion facilitates the
acquisition of many other important developmental skills in the cognitive,
communication, social, and motor domains (Bertenthal & Campos, 1990;
Campos & Bertenthal, 1991). Many factors interact to influence
the onset of walking. Leg strength, postural control, cognition, and
motivation are only a few examples (Thelen & Smith, 1994). In 1992
we (Ulrich, Ulrich, & Collier, 1992) reported that infants with DS
were able to display consistent, well-coordinated, alternating stepping
patterns by 11 months of age when held upright on a small motorized
treadmill. Infants with DS performed similar to infants without DS but
at a later age. Learning that infants with DS possess a hidden ability
for alternating stepping long before they walk offers an early window
of opportunity to implement an intensive early intervention program
designed to facilitate earlier onset of walking and improved walking gait.
How and why would specific practice on a treadmill be more effective
than traditional global approaches to motor development intervention?
We propose that treadmill stepping practice strengthens and stabilizes
the neural network involved in producing this pattern, increases the leg
strength needed to pull to a stand and walk, and improves the specific
postural control mechanisms needed to maintain upright balance when
transferring weight from one leg to the other. By creating a stimulus
(e.g. treadmill) that facilitates the repetition of a pattern of movement,
the neural connections involved are strengthened (Edelman, 1987; Sporns
& Edelman, 1993). The enhancement of these neural connections
arises from the coupling of multimodal sensory imput generated by the
active child in relation to his/her environment. This process helps
the child learn how to coordinate and control his/her extremities.
Dynamic systems theory (Thelen & Ulrich, 1991) aligns with Edelman's
approach but extends it by emphasizing that multiple subsystems, such as
strength, proprioception, joint structure, motivation, temperament, etc.
are as important as the nervous system in determining the specific motor
behaviors a child displays. We hypothesized that the treadmill training
will have a positive impact on multiple subsystems which, in cooperation,
should facilitate the onset of walking.
Methods. In this study we randomly assigned 30 infants with
Trisomy 21 to the experimental treadmill or control groups. All infants
entered the study when they could sit independently for 30 seconds.
In our earlier work (Ulrich, Ulrich, Collier, & Cole, 1995) the
ability to sit for 30 seconds was a behavior that occurred just prior to
the child's sensitivity to the treadmill stimulus. All infants received
pediatric physical therapy at least biweekly from a registered physical
therapist throughout the course of the study. Infants assigned to
the treadmill training group received parent administered training in
their home 5 days per weeks for 8 minutes per day. All infants were
observed biweekly for the onset of new motor behaviors and to measure
physical growth. The gauge on the infant treadmills allowed us to monitor
treadmill use. All infants were videotaped bimonthly while performing
for 5 one minute trials on the treadmill.
Results. Infants in the treadmill group progressed from sitting
to walking with assistance and walking independently significantly faster
than the control group (P=.03 and P=.02, respectively). The magnitude
of the treatment effect as measured by effect size statistics, indicates
a large treatment effect. On average, the experimental treadmill group
walked independently 101 days earlier than the control group.
Discussion. The pattern of results supports the hypothesis
that intensive early training based on sound principles of developmental
science can lead to functional outcomes in locomotor behavior in infants
with DS. Although the results appear very promising we are not confident
that we have designed the optimal treadmill procedures and will need to
pursue future modifications based on research, feedback from pediatric
physical therapists, and parent insights. We are confident that the
treadmill has the potential to drive new clinical practices and have an
impact beyond locomotor behavior.
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