This study assessed a 12-week, family-oriented program intended to promote healthier 24-hour movement patterns among school-age children and their parents in Chile. Parent-child pairs volunteered from two private schools and one public school, and schools were used to determine group assignment in a parallel, non-randomized, open-label design.

The intervention blended brief weekly digital guidance for parents (concise infographics/videos and actionable tips sent via email/WhatsApp) with three in-person family sessions (a functional-training class, parent-child modified games, and an outdoor trekking activity) led by a Physical Education teacher with support from school staff. The comparison group continued usual routines and completed the same assessments.

Outcomes were collected at baseline and after the intervention period (post-intervention window around Week 16). The primary outcome was the change in children's out-of-school moderate-to-vigorous physical activity (MVPA) estimated with the Youth Activity Profile-Spain/Latin America version (YAP-SL). Secondary outcomes encompassed children's in-school and weekend MVPA, sedentary time, and sleep duration, as well as parents' MVPA and sedentary time (IPAQ-Short Form) and perceived physical fitness for both parents and children (International Fitness Scale, IFIS). Potential intervention-related adverse events during face-to-face activities and those reported between sessions were monitored.

The institutional ethics committee approved the protocol and the intervention was considered minimal risk. This is a retrospective registration completed after study execution at the request of the sponsor. An exploratory mediation analysis is planned to examine plausible pathways linking the program to changes in MVPA.

Rationale Low physical activity and prolonged sedentary time in childhood are widespread and linked to unfavorable health and developmental outcomes. Engaging parents as agents of change is a promising strategy to support children's daily movement behaviors across the full 24-hour cycle (physical activity, sedentary time, and sleep). In Latin American school settings, pragmatic, scalable formats that combine short digital prompts with occasional on-site family activities may be feasible and impactful.

Objectives

1. Primary: Determine whether a 12-week multicomponent, family-based program increases children's out-of-school MVPA compared with usual activities.
2. Secondary: Evaluate effects on children's in-school and weekend MVPA, sedentary time, and sleep; parents' MVPA and sedentary time; and perceived physical fitness (parents and children).
3. Exploratory: Conduct a mediation analysis to explore potential pathways (e.g., changes in sedentary time, sleep, or perceived fitness) through which the intervention may influence children's MVPA.

Design and Setting Two-arm, parallel, non-randomized, open-label study conducted in Chilean primary schools. Group assignment was determined at the school level for logistical and feasibility reasons (two private and one public school). Assessments were completed at baseline and post-intervention (~Week 16).

Participants Eligible units were parent-child pairs recruited through school meetings. Children were primarily 5th-grade students (one school deviated for scheduling reasons). Inclusion required the ability to participate safely in light-to-moderate physical activity and access to email and/or WhatsApp for digital communications. Informed consent (parents) and assent (children) were obtained. Exclusions included medical conditions that would preclude safe participation or concurrent enrollment in another structured physical activity program.

Intervention (summary aligned with TIDieR)

• Format & Dose: 12 weeks combining weekly digital materials for parents and three on-site family sessions.
• Digital component (Weeks 4-15): Short infographics/videos and practical suggestions were delivered via email/WhatsApp each week (brief educational content early in the week and follow-up prompts later in the week).
• In-person sessions: (i) Functional training class for parents and children (school gym), (ii) modified games session (school gym), and (iii) outdoor trekking activity. Each lasted ~90 minutes and was supervised by a Physical Education teacher with assistance from the school's sports department.
• Implementation timeline (abridged): Week 1 school authorization; Week 2 information sessions and consent/assent; Week 3 baseline questionnaires and anthropometry; Weeks 4-15 digital materials; Weeks 7, 11, and 15 in-person sessions; Week 16 post-test; Week 17 feedback meetings with families and school authorities.
• Adherence & Fidelity: Delivery logs for digital materials and attendance records for on-site sessions were maintained; activities were adapted to accommodate varied fitness levels.

Comparator Participants in the comparison group maintained their usual activities and were measured on the same schedule as the intervention group.

Outcomes and Measurements

• Primary outcome: Children's out-of-school MVPA (min/day) estimated with the YAP-SL, which uses context-specific items and established calibration procedures to model daily MVPA.
• Secondary outcomes: Children's in-school and weekend MVPA (YAP-SL); sedentary time (hours/day, YAP-SL); sleep duration computed from weekday/weekend bed/wake times (average across the week); parents' MVPA and sedentary time derived from the IPAQ-Short Form; and perceived physical fitness for both parents and children using the International Fitness Scale (IFIS) (higher scores reflect better perceived fitness).
• Safety monitoring: Any intervention-related adverse events (e.g., musculoskeletal complaints, dizziness, falls) were recorded during face-to-face sessions and via parent reports between sessions.

Statistical Approach Primary analyses compare change from baseline to post-intervention between groups, with models adjusted for baseline values and additional covariates as appropriate for the non-randomized design. The mediation analysis will estimate indirect effects along pre-specified behavioral/fitness pathways using established regression-based procedures, recognizing design constraints and measured covariates.

Ethics and Oversight The study received approval from the institutional bioethics committee and adhered to the principles of the Declaration of Helsinki. Given the behavioral nature and low risk of the activities, monitoring was conducted by the research team, with procedures specified for reporting serious events to the PI and the ethics board.

Registration Note This is a retrospective registration finalized after data collection at the sponsor's request.

Inclusion Criteria:

• Parent-child dyad from a participating primary school (child typically in grades 3-6).
• Parent/legal guardian aged ≥18 years; child aged ≥8 years at enrollment.
• Able to take part safely in light-to-moderate physical activity (medical clearance as needed).
• Access to a mobile phone with WhatsApp and/or email for weekly digital materials.
• Signed informed consent from the parent/legal guardian and assent from the child.
• Availability to attend the three scheduled in-person family sessions and complete baseline and post-intervention assessments.

Exclusion Criteria:

• Any medical condition, injury, or disability that, in the investigator's judgment, would make participation unsafe or preclude planned activities.
• Current participation in another structured physical activity or lifestyle intervention trial.
• Inability to comply with the study schedule, procedures, or outcome assessments.
• Lack of access to WhatsApp/email for receiving digital materials.

De-identified individual participant data (IPD) underlying the main results will be shared, including parent-child demographics, group assignment, baseline and post-intervention outcomes (YAP-SL MVPA components, sedentary time, sleep measures), IPAQ-Short Form metrics, International Fitness Scale (IFIS) scores, and adverse event dataset. Direct identifiers will be removed; quasi-identifiers will be generalized (e.g., age in years; site masked). A data dictionary/codebook will accompany the dataset. Requests must be consistent with consent and ethics approvals.

Beginning 6 months after the Primary Completion Date and available for 36 months thereafter (extensions considered upon reasonable request).

Available to qualified researchers with IRB/ethics approval and a signed Data Use Agreement. Requests should include a brief proposal and analysis plan and be sent to the Principal Investigator. Approved requests will receive access via a secure file transfer or institutional repository. Re-identification attempts and contact with participants/schools are prohibited; citation of the original study is required.

Not applicable for this behavioral program; participants and providers were aware of group assignment. Standardized instructions and prespecified analyses were used to reduce bias.