Intervention to Reduce Sedentary Behavior During School Recess Among Adolescents

Effectiveness of an Intervention to Reduce Sedentary Behavior During School Recess Among Adolescents: A Cluster Randomized Controlled Trial

This cluster randomized controlled trial evaluated the effectiveness of an 8-week, school-based behavioural intervention grounded in the Multi-Process Action Control (M-PAC) framework in promoting interruption of sedentary behaviour during school breaks among adolescents. Twelve primary and secondary schools in China, were recruited and randomly allocated (at the school level) to either an intervention group or a control group to minimise contamination and support pragmatic delivery within the school setting. Schools assigned to the intervention group implemented a multi-component programme comprising educational materials, teacher-delivered guidance, peer reminders, and health lectures, whereas control schools continued their usual routines without receiving intervention materials. The primary outcome was interruption of sedentary behaviour during school breaks assessed using self-reported measures. Secondary outcomes included physical activity levels, emotional and behavioural problems, executive function, and psychological factors related to behaviour regulation, such as motivation, planning, and habit. Findings from this trial are intended to inform the development and implementation of feasible, theory-informed school strategies to reduce sedentary behaviour during school breaks.

This study was a cluster randomized controlled trial designed to evaluate the effectiveness of a school-based intervention grounded in the Multi-Process Action Control (M-PAC) framework to promote interruption of sedentary behaviour during school breaks among adolescents. A cluster randomization design was adopted, with schools as the unit of randomization, to minimise contamination between participants and to enhance the feasibility of intervention delivery within the school setting.

Twelve primary and secondary schools in China were recruited using convenience sampling and randomly allocated to either an intervention group or a control group. Schools were recruited through existing school partnerships and administrative feasibility considerations. The majority of participating schools were located in Guangdong Province (n=9), reflecting the location of the coordinating research team and the primary recruitment network. To enhance the diversity of school contexts and improve the external validity of findings, additional schools were recruited from Hainan (n=1) and Shanxi (n=2) using the same eligibility criteria and standardized implementation procedures across sites. The intervention was implemented over an 8-week period. Schools assigned to the intervention group received a multi-component programme informed by the M-PAC framework, designed to target key behaviour regulation processes relevant to sedentary behaviour interruption, including reflective, regulatory, and reflexive mechanisms. Intervention components included weekly educational leaflets, guidance delivered by physical education teachers, peer reminders during school breaks, and health lectures. Schools assigned to the control group continued their usual school routines and did not receive intervention materials during the study period.

The primary outcome was interruption of sedentary behaviour during school breaks, assessed using self-reported measures. Secondary outcomes encompassed physical activity levels, emotional and behavioural problems, executive function, and social-cognitive variables derived from the M-PAC framework (e.g., attitudes, intention, and habit). In addition, process evaluation indicators (e.g., intervention fidelity) and relevant covariates (e.g., demographic characteristics, academic stress, and the school physical activity environment) were assessed to support interpretation of intervention effects.The study involved a non-clinical population and did not include biomedical or medical health outcomes. The study protocol was approved by the institutional ethics committee, and written informed consent was obtained from all participants prior to participation.

Inclusion Criteria

1. Students aged 10-17 years
2. Enrolled in participating primary or secondary schools
3. Able to participate in regular school physical activities and daily routines
4. Able to understand and complete study questionnaires
5. Willing to comply with study procedures
6. Written informed consent obtained from parents or legal guardians

Exclusion Criteria

1. Diagnosed medical conditions that contraindicate participation in physical activity
2. Physical disabilities, injuries, or health conditions that limit normal participation in school-based activities
3. Participation in other structured physical activity or sedentary behavior intervention programs during the study period
4. Cognitive or language difficulties that preclude understanding of study procedures or completion of questionnaires
5. Inability or unwillingness to comply with study procedures