The long-term goal of this project is to learn whether a tailored physical activity program is practical, enjoyable, and helpful for families, and whether it has the potential to improve children's physical development and health. Before launching a large study, the research team completed several early phases to make sure the program met families' needs. First, a needs assessment was conducted with mothers to understand barriers to physical activity and what types of support would be most useful. Using this feedback, the program was refined and tested with three mother-child pairs over six weeks. Finally, there was an 18-week pilot randomized trial to examine feasibility and acceptability.

Researchers are now conducting a larger randomized trial with up to 266 families. Half of the families are randomly assigned to receive the physical activity program, and half to a comparison group. The program combines fun, age-appropriate movement activities for children with practical support for parents. Sessions focus on building core movement skills such as jumping, balancing, running, and throwing, while also encouraging confidence, coordination, and enjoyment of being active. Activities can be adapted to each child's ability and home environment, making the program realistic for busy families.

The program includes both in-person sessions and technology-based activities. In-person sessions provide hands-on support for learning new skills. Technology-based activities offer simple ideas families can use at home or during daily routines, such as hopping games, balance challenges, or quick movement breaks.

Because parents in earlier phases wanted nutrition support, in-person sessions also includes a brief, child-friendly exposure to fruits and vegetables, along with simple recipes. A "Tasting Party" at the start of the program allows children to try different foods, and Veggie Meter scans at the beginning and end of the study help track changes in fruit and vegetable intake.

Overall, this study will help determine whether a family-tailored physical activity program is a promising approach to improving physical activity, movement skills, and early health indicators in young children born to mothers with obesity.

Children born to mothers with obesity are at elevated risk for obesity and related cardiometabolic conditions beginning early in life. Evidence suggests that these children may engage in lower levels of physical activity, experience delays in gross motor skill development, and encounter additional barriers to movement and active play prior to school entry. Early childhood represents a critical window for establishing movement competence, physical activity behaviors, and dietary exposures that track into later childhood and adulthood. Interventions during this developmental period may therefore offer an important opportunity to reduce health risk trajectories. To address this need, the research team developed a family-based, developmentally tailored physical activity intervention designed to support gross motor skill development, promote enjoyable movement experiences, and reinforce healthy eating behaviors among preschool-aged children at elevated risk.

Prior to initiating the this trial, the team conducted a series of formative and pilot phases to refine intervention components and ensure alignment with family needs and preferences. First, a needs assessment with mothers of preschool-aged children was conducted to identify perceived barriers to child physical activity, contextual constraints within the home environment, and desired forms of support. Findings from this phase informed iterative refinement of program content and delivery strategies. Next, the revised materials were pre-tested with three mother-child dyads over a six-week period to assess usability, engagement, and logistical feasibility. Building on these findings, we conducted an 18-week pilot randomized trial to further evaluate feasibility, acceptability, and preliminary implementation outcomes.

The current study is a larger-scale randomized controlled trial enrolling up to 266 families. Families are randomized to either the intervention condition or a control condition. The intervention integrates developmentally appropriate, play-based movement activities for children with structured support for parents to facilitate and reinforce physical activity in the home. Intervention sessions focus on foundational gross motor skills-including jumping, balancing, running, and throwing-while also fostering coordination, self-efficacy, and positive affect toward physical activity. Activities are designed to be adaptable to children's developmental skill levels and household environments, enhancing feasibility for diverse families.

Intervention delivery combines in-person and technology-delivered components. In-person sessions provide hands-on instruction and guided practice to support skill acquisition and movement confidence. Technology-delivered components extend learning beyond in-person sessions by offering brief, low-burden activity prompts that families can integrate into daily routines (e.g., movement games during transitions, short balance or hopping challenges, or active play during household tasks). This hybrid approach is intended to promote skill generalization, reinforce parent engagement, and support sustained physical activity opportunities in the home.

In response to strong interest expressed by parents during formative work, nutrition exposure is embedded in in-person sessions. Children participate in brief, developmentally appropriate fruit and vegetable tastings, accompanied by simple, family-friendly recipes to encourage at-home practice. Objective assessment of fruit and vegetable intake is conducted at baseline and follow-up using Veggie Meter scans to examine changes in carotenoid status over time.

Across all phases, the intervention is grounded in the principle that young children learn most effectively through positive experiences, encouragement, repetition, and opportunities for mastery. Because caregivers-particularly mothers-play a central role in shaping home routines and modeling health behaviors, the intervention targets the family unit rather than the child alone. Primary outcomes for the trial include feasibility, acceptability, and fidelity of intervention delivery, as well as child-level changes in physical activity, gross motor skill development, and early health indicators. Findings from this study will inform the potential of a family-tailored physical activity intervention to alter early-life health trajectories among children born to mothers with obesity.

*The study was registered once the requirement for registration in an ICMJE-accepted registry was identified. No changes were made to study procedures or participant activities as a result of this timing.

Inclusion Criteria: Mother-child pair where the mother has

• Body mass index >30 and
• The child is between 3 and 5 years of age.

Exclusion Criteria:

• mothers sharing that a doctor has requested that either mother or child not exercise (e.g., asthma).