The goal of this clinical trial is to evaluate whether a home-based mHealth intervention can improve adherence to the 24-Hour Movement Guidelines in preschool-aged children (3-4 years old) who currently meet 0 or 1 of the guidelines for physical activity, sedentary behavior, and sleep. The main questions it aims to answer are:

• Can the intervention increase the proportion of children meeting all three 24-Hour Movement Guidelines (physical activity, screen-time, and sleep)?
• Is the intervention feasible for parents to implement, as measured by a parent feedback survey?

Researchers will compare an intervention group to a waitlist control group to assess whether the intervention leads to increased guideline adherence.

Parents and Participants:

• Children will wear an accelerometer to track physical activity and sleep patterns.
• Parents will use a mobile app that delivers weekly lessons and behavior-related goals to encourage healthy movement behaviors in their children.
• Parents will complete questionnaires on their child's movement behaviors and development at baseline, 6 weeks, and 12 weeks.
• Additionally, children will undergo motor skills assessments, and parents will provide feedback on cognitive development and behavioral changes.

The Shining Star study is a randomized controlled trial designed to evaluate the feasibility and preliminary effectiveness of a 12-week home-based mHealth intervention aimed at improving adherence to the 24-Hour Movement Guidelines (physical activity, sedentary behavior, and sleep) among preschool-aged children (3-4 years old). The trial consists of two groups: an intervention group receiving the mHealth intervention and a waitlist control group.

The primary objective is to determine if the intervention increases the proportion of children meeting all three 24-Hour Movement Guidelines. The intervention focuses on engaging parents through a mobile app, which delivers weekly lessons and behavior-related goals to promote healthy movement behaviors in children. Secondary objectives include assessing changes in child motor skills, cognition, behavioral problems and executive function, and BMI.

Study Design and Procedures:

Participants will be randomly assigned to either the intervention group or a waitlist control group. The intervention group will use the Shining Star mobile app, which provides short, weekly messages (less than 500 characters) and links to additional resources. The app will also include gamification elements, behavior trackers, and a forum for parents to connect with each other. Participants in the control group will receive access to the app after the 12-week intervention period.

Key measurements will be taken at three time points: baseline (Week 0), mid-point (Week 6), and at the end of the intervention (Week 12). Measurements include accelerometer data to assess physical activity, sedentary time, and sleep, anthropometrics to assess BMI, as well as parent-reported screen time, child motor skills, behavioral problems and executive function, and cognition. Usability and feasibility of the mobile app will be assessed through weekly app usage and feedback questionnaires.

Sample Size and Statistical Plan:

A total of 80 parent-child dyads (40 per group) will be enrolled in the study. A sample size of 30 families per group is expected to provide 80% power to detect a meaningful difference in the proportion of children meeting all three recommendations after 12 weeks. Based on a projected dropout rate of 25%, the target enrollment is 80 families.

Statistical analysis will focus on two primary hypotheses:

1. Whether a greater proportion of children in the intervention group meet the 24-Hour Movement Guidelines compared to the control group at 12 weeks.
2. Whether parents report that the intervention is feasible, with a target feasibility rating of ≥4.0/5.0 on a Likert scale.

Additional exploratory analyses will evaluate changes in child motor skills, behavioral problems, cognition, and growth as well as home-level and parent-level correlates.

Quality Assurance and Data Management:

Data will be collected using validated measures, and all data will be securely stored in REDCap. Clinical data collected at screening and follow-up visits, including accelerometer data and questionnaires, will be stored in a secure database at the University of Kansas Medical Center (KUMC). The data will undergo validation and consistency checks before analysis.

• Quality Assurance Plan: The research coordinator will ensure that accurate and complete data is transcribed from paper sources into REDCap. To maintain data quality, accuracy, and integrity, data entry will be performed twice. The REDCap data comparison tool will then be used to produce a final "Clean" entry.
• Missing Data Plan: Participants who do not complete the required assessments at baseline (Week 0), mid-point (Week 6), and end of the intervention (Week 12) will be excluded from the final analysis. Efforts will be made to retain participants throughout the study to minimize missing data.
• Statistical Analysis Plan: The primary analysis will compare the proportion of participants in the intervention and control groups meeting all three recommendations at 12 weeks using chi-square analysis. The secondary analysis will average the Likert scale responses across all weeks completed. Exploratory analyses will utilize linear regression to examine changes in outcomes between the treatment and control groups, along with iso-temporal substitution analysis to assess the impact of behavior substitution on child developmental outcomes. Additionally, the investigators will examine the relationship between meeting specific movement recommendations and child outcomes, with changes in theoretical components as potential mediators. Statistical significance will be set at p = 0.05 for analyses.

The study will also adhere to KUMC standard operating procedures for data collection, data analysis, and confidentiality as outlined in the study protocol.

Inclusion (Child):

• Ages 3-4 years.
• Parent report that they meet 0 or 1 recommendation for physical activity, sleep, and screen-time as defined by the 24-hour movement guidelines. The physical activity recommendation is defined as greater than or equal to 3 hours/day of total physical activity, including 1 hour of moderate-to-vigorous physical activity. The sleep recommendation is defined as 10-13 hours/day. The sedentary behavior recommendation is defined as less than or equal to 1 hour/day of sedentary screen-time.

Inclusion (Parents):

• Parents must agree to use their mobile phone for the duration of the study (~12 weeks) and download the mobile app onto their phone.
• The parent/caregiver is fluent in English to participate in testing the mobile app.
• The parent/caregiver must be willing to travel to KUMC to complete study visits.

Exclusion (child):

• Mobility limitations as reported by the parent.
• Meeting two or more recommendations for physical activity, sleep, and screen-time.
• Sibling or household member is participating or participated in the study.

male and female.

Final data will be submitted to the NICHD DASH database.

Beginning 1 year after publication with no end date.

Data will be stored in the DASH data repository. Other requests for data and further information can be made to the PI, who will follow appropriate channels to distribute the data.