Research Review Treadmill training facilitates the onset of walking in infants with Down syndrome 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. References. Bertenthal, B.I. & Campos, J.J. (1990). A systems approach to the organizing effects of self-produced locomotion during infancy. In C. Rovee-Collier & L.P. Lipsitt (Eds.), Advances in Infancy Research (vol. 6, pp. 1-60). Norwood, NJ: Ablex. Campos, J.J. & Bertenthal, B.I. (1991). Locomotion and psychological development in infancy. In F. Morrison, C. Lord, & D. Keating (Eds.), Applied Developmental Psychology (vol. 3). New York: Academic. Edelman, G.M. (1987). Neural Darwinism. New York: Basic Books. Sporns, O. & Edelman, G.M. (1993). Solving Bernstein's problem: A proposal for the development of coordinated movement by selection. Child Development, 64(4), 960-981. Thelen, E. & Smith, L.B. (1994). A dynamic systems approach to the development of cognition and action. Cambridge, MA: MIT Press. Thelen, E. & Ulrich, B.D. (1991). Hidden skills: A dynamic systems analysis of treadmill stepping during the first year. Monographs of the Society for Research in Child Development, 56, (1, Serial No. 223). Ulrich, B.D., Ulrich, D.A. & Collier, D.H. (1992). Alternating stepping patterns: Hidden abilities of 11-month -old infants with Down syndrome. Developmental Medicine and Child Neurology, 34, 233-239. Ulrich, B.D., Ulrich, D.A., Collier, D.H., & Cole, E. (1995). Developmental shifts in the ability of infants with Down syndrome to produce treadmill steps. Physical Therapy, 34, 233-239. All Research Reviews