The emergence of crawling and walking is significantly delayed in infants with Down syndrome (DS), but the development of independent mobility provides infants with new opportunities for exploring the environment and interacting with objects and people that are important foundations for early learning. Increasing infant mobility early in development with body weight supported harness systems may support infant exploration, communication, and social interaction. This project will set the stage for the first clinical trial of a mobility-related intervention specifically tailored for infants with DS by testing the feasibility of harness systems with infants and families and identifying measures that will serve as primary outcome variables. Upon completion of this pilot project, necessary preliminary data and experience required for an in-home, high-impact clinical trial for infants with DS will have been obtained.

Investigators will visit families at home both in-person and virtually via Zoom. At all sessions, infants and caregivers will be videorecorded at home while playing together with the infant's own toys (15 min) and with a standard set of age-appropriate commercially available toys provided by the research team (15 min). During the harness trial period, sessions will be divided so that the infant is observed both in and out of the harness. Parent reports of language development (MacArthur-Bates Communicative Development Inventory; 10 min) and locomotor development (Locomotor Experience Interview; 10 min) will be collected at the initial visit, study midpoint (3 months), and study exit (6 months). Parents will be surveyed once about the feasibility and acceptability of the body weight supported harness system at the end of the harness trial period (10 min), and they will complete a study participation satisfaction survey at study exit (10 min). In addition, infants will be administered the Bayley Scales of Infant and Toddler Development-4 (30 min) and the Early Social Communication Scales (10 min) at the beginning, middle, and end of study participation.

Participants will be observed twice a month for 6 months (one visit per month on Zoom and the other in person), for a total of 12 observations per child.

Part 2 study participation will involve a total of 12 sessions per parent/infant dyad, lasting between 30 and 70 min, depending on the visit protocol (see above).

Each family will also have a 1-month Harness Trial Period with the PUMA system in their home. These will be staggered over the course of the study period. At the beginning of the trial period, investigators will deliver the harness system to the home and assist with setup and troubleshooting. Families will be given a brief training in harness setup and use and a safety checklist to review daily before using the system with their infant. Families will be asked to use the harness with their infant for at least 30 minutes daily. The harness will be collected by the research team at the end of the trial period. Each day during the Harness Trial Period, parents will track how long they use the harness system with their infant (in minutes), what activities they engaged in (e.g., toy play, book sharing), and any challenges they encountered (e.g., infant fussiness) in a log (5 min).

The PUMA system is an FDA registered device manufactured by Enliten LLC that provides body weight support while moving around. It consists of a 9' x 9' metal canopy frame with no cover that is adjustable in height. Infants will wear custom lightweight cloth vests designed specifically for the PUMA. The vest will be connected to a beam at the top of the structure. The PUMA supports up to 60 pounds and permits movement anywhere beneath the structure. In case of an emergency, a quick release unit can be pulled to rapidly separate the harness from the support unit. For the PUMA, this device is attached to the spreader bar, out of reach of the child user.

Inclusion Criteria:

• confirmed diagnosis of Trisomy 21
• younger than 24 months
• English is the primary language of the home (due to use of standardized language assessments normed on English-speaking children)
• able to sit without support
• not yet taking any independent steps.

Exclusion Criteria:

• Mosaic or Translocation Down syndrome
• severe, uncontrolled medical problems (including heart disease with cardiovascular instability, uncontrolled epilepsy)
• severe uncorrected hearing or vision impairments

Data from standardized assessments will be shared with the NIH INCLUDE database.

One year after study completion

Access granted to approved users of the INCLUDE database