‘WeekendGo!’ A digital health intervention for promoting children’s physical activity in the family environment: a cluster randomised controlled trial protocol

Abstract

Insufficient physical activity (PA) among children has become a major global public health concern. The family environment plays a crucial role in shaping children’s weekend PA, yet evidence-based interventions in this context remain scarce This study will conduct a three-arm cluster randomised controlled trial, ‘WeekendGo!’ guided by an integrated theoretical framework that encompasses the Social Cognitive Theory, Health Action Process Approach and Family Functioning Theory, aimed at promoting children’s weekend PA. Approximately 555 children and their parents will be recruited and randomised into three groups: a staged intervention group (intervention I), a general intervention group (intervention II) and a control group, for 12 months. The primary outcome will be the children’s weekend moderate-to-vigorous PA. Secondary outcomes will include children’s cognitive factors such as self-efficacy, perceived barriers and resources, motivation and behavioural intention. Generalised linear mixed-effects models will be used for analysis, adhering to the intention-to-treat principle, with missing data handled through multiple imputation. Trial registration number: ChiCTR2500095942.

WHAT IS ALREADY KNOWN ON THIS TOPIC.

WHAT THIS STUDY ADDS

• This three-arm cluster-randomised controlled trial will evaluate a theory-guided digital health intervention (‘WeekendGo!’) designed specifically to promote children’s weekend PA within the family context. The trial will compare the effects of a staged, tailored intervention, a general intervention and a control condition to empower parents by using an integrated Social Cognitive Theory-Health Action Process Approach-Family Functioning Theory framework and behaviour change techniques delivered via a WeChat mini-program.

HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY

• The findings will provide an evidence-based and replicable model for developing theory-driven digital family interventions, potentially informing future mechanism-focused research. The ‘WeekendGo!’ programme will also offer a scalable tool for health and education practitioners to engage parents in promoting child PA. Results may also inform public health policy by highlighting the potential of integrating targeted family-level digital strategies into broader efforts to increase children’s PA.

Introduction

Physical activity (PA), defined as ‘any bodily movement produced by skeletal muscles that results in energy expenditure’,¹ plays a vital role in children’s health. It contributes to improved bone health, body weight regulation, cardiorespiratory fitness, muscle strength and cardiometabolic health, enhancing cognitive function and reducing the risk of depression.² The benefits of PA for children extend across both short-term and long-term developmental stages.³

Despite broad recognition of its importance, insufficient PA among children and adolescents remains a global issue. The WHO recommends that children and adolescents aged 5–17 years engage in an average of at least 60 min of moderate-to-vigorous PA (MVPA) daily.⁴ However, approximately 80% of individuals aged 14–24 years fail to meet this guideline, and PA levels tend to decline with age.⁵ In China, the situation is similarly concerning.⁶ The persistent inadequacy of PA among children has become a pressing public health challenge.

Globally, researchers have primarily focused on school-based PA interventions. Despite numerous school-based intervention studies worldwide, the overall improvement in children’s PA levels has been modest, and the downward trend has not been reversed.⁵ These findings suggest that relying solely on the school setting may be insufficient to effectively change children’s PA behaviours. PA patterns differ across environments and time periods: weekday PA mostly occurs at school,⁷ whereas children tend to be more active during weekends at home.⁸ Therefore, sustainable improvement in children’s PA is unlikely without the engagement of family members.⁹ Therefore, sustainable improvement in children’s PA is unlikely without the engagement of family members.¹⁰ Indeed, PA is not only a vital component of education, but also a habit and interest that requires family guidance and support. Therefore, scholars have proposed that family factors should be emphasised in PA interventions.¹¹

The family holds irreplaceable advantages in fostering children’s PA behaviour. Parents serve not only as the primary shapers of children’s daily routines but also as key organisers and facilitators of their PA. Parents’ participation in PA helps cultivate children’s interest and habits,¹² and family-based interactions are beneficial for sustaining healthy behaviours over time.¹³ Meta-analysis indicates that children receiving higher levels of parental support are more likely to meet PA recommendations.¹⁴ Parental support includes encouraging participation, engaging in PA alongside, role modelling and watching during children’s PA—all of which are positively associated with meeting PA guidelines.¹⁵ Longitudinal research further confirms that parental companionship and encouragement predict higher levels of children’s MVPA both in the short and long term.¹⁶ Thus, family-based interventions effectively complement school programmes. Studies have demonstrated that incorporating family components into school-based health programmes enhances the effectiveness and sustainability of children’s PA outcomes.^{17 18} Direct parental involvement yields stronger effects on children’s PA than indirect involvement.⁹

Moreover, family influence extends beyond direct support behaviours to include family functioning¹⁹ and the home environment,²⁰ both of which can affect the accessibility and sustainability of PA interventions. However, previous studies generally combine family and school settings, making it difficult to disentangle their independent effects or assess PA during family-dominant periods such as weekends. Consequently, the sole impact of family-based interventions on children’s PA remains insufficiently explored.

Previous interventions have relied heavily on workshops or in-person meetings with limited frequency, thus constricting parental engagement. Yet, parental participation is a key determinant of PA promotion among children. Joint parent–child activities are more likely to produce lasting behavioural changes.⁹

In addition, previous interventions mostly lack personalisation tailored to family characteristics, potentially restricting effectiveness. With the advancement of digital technology, digital health interventions offer new opportunities for precise and personalised health promotion. Digital health tools have been widely applied in disease prevention, health behaviour promotion and public health services.^{21 22} In the PA domain, integrating digital components enhances intervention fidelity and provides real-time feedback. For instance, a study evaluating a remote classroom PA intervention combined with family digital support demonstrates its feasibility and effectiveness in increasing children’s PA.²³ Similarly, app-based family interventions have been shown to improve both PA levels and children’s psychological well-being.²⁴ Therefore, integrating digital health technologies into family-based PA interventions holds great promise for delivering personalised strategies that promote parents’ participation and sustain children’s PA improvements over time.

Objectives

This study aims to develop and evaluate a theory-based digital health intervention to promote children’s weekend PA within the family environment—an independent, family-dominant time frame less influenced by school settings. By empowering parents and leveraging digital tools, the study seeks to provide both theoretical insights and practical evidence for future family-based interventions targeting children’s PA.

Methods

This protocol complies with the Standard Protocol Items: Recommendations for Interventional Trials (SPIRIT) 2025 statement (see online supplemental materials).

Study design and setting

This study will adopt a three-arm cluster randomised controlled trial design. The trial will be conducted in six primary schools located in Daxing District, Beijing, China. To ensure comparability, eligible schools should be: (1) non-key schools with moderate teaching quality and facilities; (2) not affiliated with any specific government agency, state-owned enterprise or other public institution; (3) non-boarding and (4) moderate in size. From each participating school, three classes will be selected as randomisation clusters.

Participants and sample size

Participants will be second-grade students (approximately 8 years old) and their parents, recruited from the selected six schools.

Inclusion criteria

• Children with no contraindications to PA.

• Children with no plans to participate in professional sports training within the following year.

• Parents who provide written informed consent and agree to participate in follow-up assessments.

Exclusion criteria

• Children with medical conditions that restrict MVPA (eg, asthma, heart disease).

• Children who are already engaged in professional sports training programmes.

Sample size calculation

The primary outcome will be the mean daily duration of children’s weekend PA. As a previous Chinese family-based intervention study suggests,²⁵ the mean duration of moderate PA is expected to increase from 30 min to 40 min postintervention (SD≈30 min). This trial will include three groups: (1) staged intervention group (intervention I); (2) general intervention group (intervention II) and (3) control group.

Assuming postintervention mean durations of 50, 40 and 30 min for the three groups, respectively, with a superiority margin of 10 min and a true mean difference of 20 min between intervention I and the control group, the required sample size per group is calculated to be 112 participants (α=0.05, one-sided; β=0.20; SD=30) using PASS 2020 software. Considering a design effect of 1.5 for cluster randomisation and a 10% attrition rate, at least 185 participants per group will be required, for a total of approximately 555 participants. Assuming an average of 35 students per class, 18 classes (6 per group) will be included.

Recruitment and informed consent

Participants will be recruited with assistance from their homeroom teachers. The teachers will verify eligibility and distribute project leaflets and informed consent forms to all eligible children and their parents. Participation is entirely voluntary. Parents and children willing to participate must submit signed paper-based consent forms (with both the child’s and the parent’s signatures).

Randomisation, allocation and blinding

To minimise within-class contamination and enhance feasibility, classrooms will serve as randomisation units. Each school’s three classes will be randomly assigned to one of three arms: (1) staged intervention group (intervention I); (2) general intervention group (intervention II) and (3) control group. Randomisation will be conducted by a researcher using R software, generating random numbers (1–3). The allocation list will be securely stored and concealed until assignment to prevent bias. Designated personnel will distribute intervention materials to participants. Only authorised staff can access allocation information; other team members will remain blinded to group assignments. Given the nature of behavioural interventions and the possibility of intergroup contact of participants, complete blinding of participants and implementers is not feasible. However, data analysts will remain blinded to group allocation to ensure objectivity in data processing and interpretation.

Intervention

Theoretical framework and approach

This study integrates Social Cognitive Theory (SCT), Health Action Process Approach (HAPA) and Family Functioning Theory (FFT) into a comprehensive SCT-HAPA–FFT theoretical framework to explain the mechanisms through which family-level factors influence children’s PA.

SCT emphasises the interplay among personal, behavioural and environmental determinants,²⁶ enabling exploration of how the family environment affects children’s PA. HAPA delineates the transition from intention to action and focuses on behavioural planning and self-efficacy,²⁷ clarifying children’s individual-level determinants of PA. FFT conceptualises the family as a functional system that provides supportive conditions for its members’ development.^{28 29}

Integrating these theories allows a multilevel understanding of how individual, familial and environmental factors collectively influence PA behaviour, forming the theoretical basis for this intervention.

Intervention strategy

Based on the integrated SCT–HAPA–FFT framework, the study will implement a digital family-based staged intervention named ‘WeekendGo!’, designed to empower parents to promote children’s PA. Intervention content will be developed using the Behaviour Change Techniques (BCTs) and Mechanisms of Action (MoAs) frameworks. BCTs are ‘replicable components of an intervention designed to alter or redirect the causal processes regulating behaviour’,³⁰ while MoAs refer to ‘the processes through which a BCT affects behaviour’.³¹

The design process will use the Theory and Techniques Tool (https://theoryandtechniquetool.humanbehaviourchange.org/tool)³² to identify the theoretical constructs, relevant MoAs and linked BCTs. All selected BCTs will be adapted according to the principles of BCT³³ and the Chinese BCT taxonomy.³⁴ The intervention tools include: WeChat mini-program, WeChat groups and Redmi 2 band.

Feedback from parents and experts will be collected through focus groups and interviews to refine the intervention before implementation (see the Patient and public involvement section). The final intervention (WeekendGo!) comprises 13 BCTs (see online supplemental materials) and includes the following components for the different targeted groups (see figure 1):

Figure 1. Overview of intervention components in the WeekendGo! programme. PA, physical activity.

• A. Core information dissemination

  Parents will receive daily push notifications every weekend and static resources via the WeChat mini-program for 12 months. Push notifications will deliver knowledge and skills to support children’s PA and family communication, while static content includes information on PA venues, PA clinic resources and PA tutorials.

• B. Interactive consultation

  Dedicated WeChat groups will enable continuous two-way communication between parents and the research team, facilitating timely responses to PA-related queries. The response includes periodically collecting parents’ PA-related questions via questionnaires for a centralised response session, while also providing prompt replies to queries raised directly by parents within the WeChat group every day.

• C. Wearable device data monitoring

  The Redmi 2 band will be employed for the monitoring of children’s PA every 3 months, providing feedback on various biological indicators (eg, heart rate). Usage guidance for the device will be disseminated within the WeChat groups before distribution.

• D. Reinforcement information dissemination

  Following the initial 3 months of the intervention, parents will be classified into different stages (HAPA Stages) every 3 months: preaction, initiation, maintenance, relapse and recovery and receive individualised stage-specific reinforcement information via the WeChat mini-program every weekend (see online supplemental materials).

• E. Supervision, reminder and feedback

  Parents will receive a prompt wearing band and dissemination every week, personalised children’s PA reports every 3 months via the WeChat mini-program and the WeChat group. Parents will also be encouraged to jointly formulate and adhere to action and coping plans with their children, and to record their child’s weekend PA and feelings via the WeChat mini-program. The plan and record can be edited every 3 months and every weekend, respectively.

• F. Incentives

  • Gamified map exploration: In line with Chinese parents’ aspirations for their children to attend prestigious universities, the incentive mechanism permits participants who meet the PA standard in each monitoring period to draw virtual postcards of landmarks in a ‘prestigious university map’ every 3 months within the WeChat mini-program. Each draw highlights the corresponding landmark, and on completing all monitoring periods, the map is fully illuminated, earning the participant a final prize. (2) Codesign graded incentive: Parents and children will be encouraged to codesign graded incentive plans. The incentive goals can be achieved by accumulating incentive points through recording PA status and formulating PA plans. And the incentive goals can be edited every 3 months.

• G. Routine health education

  Weekly dissemination of general PA-related knowledge via the WeChat group, covering the benefits of PA and methods for handling common PA-related injuries.

All information will be made available to participants in all groups after the intervention. The final programme photo is available in the online supplemental materials.

Outcome measurement and instrument

Primary outcome

The primary outcome is the mean daily duration of children’s weekend PA (in minutes) assessed at T3–T5 (grades 3–4). PA will be measured using both:

Parent-reported questionnaires (adapted from the Chinese version of the International Physical Activity Questionnaire³⁵); Objective accelerometer data from the Redmi 2 band.

According to the HAPA model, PA stage classification (preaction, initiation, maintenance, relapse, recovery) is determined by changes in PA level between consecutive time points. Children who achieve ≥60 min of MVPA at two consecutive time points will be classified as being in the maintenance stage.

Secondary outcome

Secondary outcomes include changes in children’s: (1) stage-specific self-efficacy (action, maintenance, recovery); (2) perceived resources and barriers and (3) motivation and intention.

These data will be collected via self-administered questionnaires completed in classrooms under the teacher’s supervision.

The participant timeline is illustrated in figure 2.

Figure 2. Schedule of enrolment, interventions and assessments (SPIRIT figure). ^bThe interval between integer time points (eg, t1-t2) represents 6 months; the interval between a time point with an integer and one with a 0.5 decimal (eg, t1-t1.5) represents 3 months.

Data collection

Data collection comprises two primary methods: questionnaire surveys and wearable device monitoring. Questionnaires are designed based on the theoretical variables of SCT, HAPA and FFT and are divided into two instruments: the parent questionnaire and the child questionnaire. Items for each variable are either adapted from existing validated questionnaires36,43 or are developed by the research team. All responses use a 5-point Likert scale, with scores ranging from 1 to 5. The variable’s total score is calculated by summing the constituent items’ scores, with higher scores indicating a stronger degree of the measured variable (see online supplemental materials).

Device monitoring will be based on the Redmi 2 Band worn by children to collect objective PA data and classify children’s PA stages in intervention I. Data are automatically synchronised to the Mi Fitness App and retrieved directly by the research team from the app. Monitoring will be conducted continuously over two consecutive weekends at seven scheduled time points (see figure 2 and online supplemental materials).

Statistical analysis

Baseline characteristics will be described according to variable type. Continuous variables such as minutes of PA, stage-specific self-efficacy scores and family support scores will be reported as mean±SD or median (IQR), as appropriate. Categorical variables (eg, proportion of meeting the PA guideline, PA stage, adoption of plans) will be summarised as counts and percentages. Between-group baseline balance will be evaluated using t-tests or Mann-Whitney U tests for continuous variables and χ² tests (or Fisher’s exact test when appropriate) for categorical variables.

Analyses of primary and secondary outcomes will use generalised linear mixed-effects models to account for clustering at the class and school levels and for repeated measures over time. The comparison between interventions I and II aims to verify the impact of staged, individualised enhanced information, incentive measures and supervision with reminders and feedback in empowering parents to influence children’s PA. Conversely, the comparison between intervention II and the control group is intended to examine the effect of core information in empowering parents to influence children’s PA.

Primary analyses will follow the intention-to-treat principle, including all randomised participants in the groups to which they are initially allocated, regardless of adherence. Missing data will be addressed by multiple imputation under the missing-at-random assumption. Sensitivity analyses of per-protocol populations using complete-case analyses will be performed to assess robustness.

Subgroup analyses will explore effect modification by child sex. Objective data from wearable devices will be used for sensitivity analyses to compare results derived from parent-reported versus device-measured PA.

Safety and monitoring

This study constitutes a behavioural intervention, with no serious physical harm anticipated. Potential minor harms include information overload or discomfort arising from answering sensitive questionnaire items. The research team will mitigate these risks by providing dedicated Q&A and support via the WeChat group and by closely monitoring all parent feedback (see online supplemental materials).

Patient and public involvement

During the study design, five parents and five children from each selected school (30 parents and 30 children in total) will be invited to interviews to elicit needs, barriers and preferred intervention formats and frequencies. A multidisciplinary panel of seven experts (in fields of psychology, PA, family education, health intervention, child and adolescent research, and digital health) will provide feedback through focus group discussions. During the intervention, a sample of parents and children from intervention arms will be interviewed to assess acceptability, perceived effectiveness and preferences. On study completion, participants and school staff will be invited to debriefing sessions, and dissemination and potential scale-up will be informed based on gathered insights.

Research ethics and dissemination

This trial was prospectively registered with the Chinese Clinical Trial Registry (ChiCTR2500095942, https://www.chictr.org.cn/showproj.html?proj=246767) on 15 January 2025. Any protocol amendments will be submitted to the institutional review board and updated on the trial registry.

Before enrolment, written informed consent will be obtained from parents; age-appropriate assent (oral or written where applicable) will be sought from participating children.

Study findings will be disseminated through peer-reviewed journals, conference presentations, reports to participating schools and families, and public summaries. All dissemination materials will preserve participant anonymity.

Ancillary and post-trial care

As there are no investigational products or invasive procedures, no routine provision of post-trial medical care is planned beyond standard care. For any adverse event during the intervention, necessary medical assistance will be provided and, where applicable, financial compensation will be handled in accordance with national regulations.

Discussion

Insufficient PA among children is a major global public health concern. Although extensive intervention studies have been conducted in school settings in recent years,⁵ the effects have not been ideal, suggesting that reliance solely on school interventions may be insufficient to effectively change children’s overall PA levels. The family, as another vital living environment for children, has unique advantages in promoting children’s PA. School interventions primarily operate for limited periods on campus and have a limited impact on the family environment, whereas children are more active in PA during family time. Interventions targeting the family setting are expected to supplement the shortcomings of school-based interventions and maintain and consolidate existing school-based PA intervention effects during family-dominated time periods. This study aims to provide new research evidence for children’s PA family interventions by focusing on weekend PA, which is a family-dominated time period.

Second, parental involvement is a key component of children’s PA interventions. However, previous family intervention formats are primarily based on seminars, resulting in insufficient parental engagement and a lack of personalised intervention measures, which may ultimately limit the intervention’s effect. To address this shortcoming, this study aims to empower parents and improve their participation through measures such as implementing health education via the WeChat mini-program and having parents and children jointly set PA plans, with the expectation of promoting sustained changes in children’s PA behaviour.

Furthermore, the theoretical framework guiding children’s PA interventions in the family context is currently unclear, and systematic, scientific guidance is lacking. This study utilises established scientific behavioural theories, such as HAPA and SCT, in combination with the influence of family function to construct the SCT-HAPA-FFT integrated theoretical framework. This framework is suitable for explaining PA interventions in the family context, as it comprehensively considers the influence of individual cognition, interpersonal factors and the family environment on PA behaviour. Based on this theoretical framework, MoAs are identified according to their theoretical constructs and further matched with BCTs, ultimately yielding PA intervention measures applicable to the family environment. This development process clearly demonstrates a complete logical path from theory to practice (behavioural theory→theoretical construct→MoA→BCT→final intervention measures), providing a systematic reference for future family interventions for children’s PA.

Strengths and Implications

This study has the following strengths: First, most previous research focusing on the school environment fails to provide sufficient evidence on the impact of the family environment on children’s PA. This study adopts a family environment perspective, selecting the weekend—a time when the family dominates and is less susceptible to school interference—as the entry point, and using children’s weekend PA as the research indicator for children’s PA in the family environment. This can more authentically reflect children’s PA status in the family setting. Second, this study integrates traditional behavioural theories, considering the influence of personal, interpersonal and environmental factors on behaviour. Guided by the integrated theoretical framework, the study empowers parents. It validates the effects of stepped and non-stepped interventions and routine health education, providing a reference for extending the explanation and intervention theory of PA behaviour. Finally, this study uses wearable devices to obtain objective data on children’s MVPA and cross-validates these results with questionnaire data, thereby more fully demonstrating the reliability of the research findings.

Limitations

The limitations of this study include: fully blinding of participants and researchers is not feasible due to the nature of the study, and only the statistical analysis personnel will be blinded to the group allocation. Challenges related to adherence to wearable device data monitoring exist. Furthermore, the study sample size is limited and does not cover the entire country, thus restricting the generalisability and representativeness of the results; future multicentre studies should be considered.

Despite these limitations, the findings of this study are expected to provide high-quality evidence for the field of children’s weekend PA intervention. By comparing different intervention groups, the importance of stepped individualised information will be revealed. In-depth analysis of the MoAs will provide a theoretical basis for developing more precise and effective intervention strategies in the future. The study results will serve as a reference for public health departments and educational institutions in formulating policies and measures to promote children’s PA.

Conclusions

This study focuses on the family as the entry point and the weekend as the family-dominated behavioural context, integrating multiple behavioural theories to conduct research on children’s weekend PA intervention. This research is expected to provide high-quality evidence for family-based children’s PA interventions and to reveal their MoAs. The study results are anticipated to provide a scientific basis for formulating more effective and targeted children’s PA intervention strategies and policies in the future.

Data availability statement

No data are available.