Measuring real-world stepping and walking performance in infants and toddlers with down syndrome

The National Institutes of Health Office of the Director awarded the University of Southern California $462,951 on July 15, 2026, under the Trans-NIH Research Support program (CFDA 93.310) to measure real-world stepping and walking performance in infants and toddlers with Down syndrome.

The award funds validation of accelerometer-based wearable step-counting devices for infants with Down syndrome, addressing a gap in clinical measurement tools. The project will establish the accuracy of step counts as a measure of real-world stepping in pre-walking infants and new walkers with Down syndrome by comparing step counts to manual video coding and to standardized capacity measures of standing and walking function. Infants with Down syndrome will be followed longitudinally from the onset of cruising to three months after independent walking onset, with assessments conducted during home visits using the Gross Motor Function Measure-88, portable pressure-sensitive gait assessment, and Stepwatch ankle-mounted devices paired with hour-long video recordings of everyday activity.

Work is performed at Los Angeles, California. The period of performance runs from July 15, 2026, to June 30, 2028.

Seattle Children's Hospital, doing business as Seattle Children's Research Institute, is a sub-recipient on the award as of August 31, 2026, delivering research collaboration services in support of the stepping and walking performance measurement protocol.

Abstract

The development of walking is disrupted in individuals with down syndrome (DS): children with DS walk later and demonstrate immature gait compared to their typically developing peers. Although much is known about the development of gait kinematics and walking skill (capacity) in DS, data on real-world walking (performance) are essentially nonexistent. Measuring real-world walking is essential to inform and target early interventions to improve locomotor development and as a clinical outcome measure for documenting effectiveness of interventions. Although real-world walking has been measured in other populations using accelerometer-based wearable step-counting devices, such devices have not been validated with infants or with any age individuals with DS. The lack of a validated step counter for infants with DS impedes scientific progress in understanding walking development and delivering interventions to target walking function. This proposal aims to address this GAP by establishing the validity of step counts as a measure of real-world stepping in pre-walking infants and new walkers with DS. Our specific aims are: 1) determine the accuracy of step counts in infants with DS compared to manual coding from video, and 2) assess the convergent validity of step counts compared to capacity measures of standing and walking function and gait in infants with DS. Infants with DS will be followed longitudinally from the onset of cruising (supported stepping) to three months after the onset of independent walking. In a series of home visits, we will assess infants' standing and walking skill (gross motor function measure-88 and spatiotemporal gait assessment using a portable pressure-sensitive walkway). We will also obtain hour-long video recordings of everyday activity while infants wear stepwatch devices on both ankles. Infants will then wear the stepwatches throughout their regular activities to collect stepping data, daily for one week following each visit. The methodological advance and knowledge gained from this project will accelerate our understanding of locomotor development in DS, inform evidence-based dosage targets for early interventions, and deliver a novel, meaningful outcome measure for clinical practice and clinical intervention trials in infants with DS. Moreover, longitudinal collection of hour-long video recordings of spontaneous behavior in the home environment over the transition to walking will generate a large, novel corpus of natural activity data that can be coded for a variety of other behaviors, informing our currently limited understanding of early development in DS and accelerating DS research.